CN112457874B - Method for controlling multistage catalytic cracking according to multi-zone partition coupling bed layers of raw material types - Google Patents

Method for controlling multistage catalytic cracking according to multi-zone partition coupling bed layers of raw material types Download PDF

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CN112457874B
CN112457874B CN202011129515.3A CN202011129515A CN112457874B CN 112457874 B CN112457874 B CN 112457874B CN 202011129515 A CN202011129515 A CN 202011129515A CN 112457874 B CN112457874 B CN 112457874B
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catalytic cracking
catalyst
reaction
cracking reaction
raw material
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CN112457874A (en
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赵亮
高金森
张宇豪
白宇恩
郝天臻
孟庆飞
徐春明
李德忠
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China University of Petroleum Beijing
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
    • C10G11/06—Sulfides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
    • B01J29/16—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J29/166—Y-type faujasite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G11/14—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts
    • C10G11/18—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts according to the "fluidised-bed" technique
    • C10G11/182—Regeneration
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G11/14—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts
    • C10G11/18—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts according to the "fluidised-bed" technique
    • C10G11/187—Controlling or regulating
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
    • C10G2400/20—C2-C4 olefins

Abstract

The invention provides a multi-zone-coupled bed control multi-stage catalytic cracking method according to the type of raw materials, wherein the raw materials comprise a first raw material containing C4 hydrocarbon, a second raw material containing C5-C6 hydrocarbon and a third raw material containing C7-C8 hydrocarbon, and a reaction device comprising a first downer, a second downer and a riser is adopted, and the method comprises the following steps: the first raw material enters a first downlink pipe to generate a first catalytic cracking reaction; the second raw material enters a second downlink pipe to generate a second catalytic cracking reaction; the product of the first catalytic cracking reaction, the product of the second catalytic cracking reaction and the third raw material enter a riser to generate a third catalytic cracking reaction; carrying out gas-solid separation on a product of the third catalytic cracking reaction to obtain an oil gas product and a spent catalyst; the spent catalyst is returned to each catalytic cracking reaction after being stripped and regenerated. According to the cracking characteristics of various hydrocarbon raw materials, different light hydrocarbon raw materials are cracked by using one system under different conditions, so that high yield of light olefins is realized.

Description

Method for controlling multistage catalytic cracking according to multi-zone partition coupling bed layers of raw material types
Technical Field
The invention relates to a catalytic cracking method of light hydrocarbon, in particular to a method for controlling multistage catalytic cracking according to a multi-zone coupling bed layer of a raw material type, belonging to the technical field of petroleum processing.
Background
With the improvement of technology and productivity, the surplus trend of oil refining and supply capacity has been developed, and in our country, 2018 oil refining capacity reaches 8.4 hundred million tons, 6.1 hundred million tons of crude oil is processed, 3.64 hundred million tons of gasoline and diesel oil are produced, and the average operating load is 72.4%, and the surplus of 1.1 hundred million tons is expected in 2020. Meanwhile, with further strict environmental protection requirements, the development of new energy and the improvement of automobile fuel efficiency are represented by electric power, hydrogen energy, biofuel and the like, the demand acceleration of gasoline is further reduced, the demand of global chemicals is increased by 4% in annual average, and the demand of global chemicals is higher than the GDP acceleration of 3% in global. Therefore, the transformation of the traditional fuel type refinery into the chemical type refinery becomes one of the development trend and the way, and particularly, how to transform the fuel type product of the gasoline into the comprehensive production of the fuel-high added value chemicals improves the social benefit and the economic benefit.
Still taking our country as an example, in order to promote the scientific development and continuous progress of petrochemical industry, the industry and informatization department makes and issues "petrochemical and chemical industry development planning (2016-2020)" in 2016, and the "planning" indicates that: in 2015-2020, the consumption of Chinese ethylene is increased from 4030 to 4800 ten thousand tons, the annual average increase rate of demand is 3.6%, the consumption of propylene is increased from 3180 to 4000 ten thousand tons, the annual average increase rate is 4.7%, the output of Chinese ethylene in 2018 is 1841 ten thousand tons, the input is 258 ten thousand tons, the input dependency is 12.3%, the output of propylene is 3035 ten thousand tons, the input is 28.4 ten thousand tons, and the input dependency is 8.6%. Therefore, the requirements of the domestic for several low-carbon olefins such as ethylene, propylene and the like are huge, the constraint of olefin import is eliminated, the whole development of the industry is promoted, and the method has significance for the whole strategic requirements of the country.
The gasoline or light hydrocarbon oil product is reasonably converted into the olefin product, and the urgent problems of excessive oil refining and shortage of the olefin product in China can be solved at the same time.
At present, at the technical level, light olefins are mainly derived from heavy oil fraction cracking processes, while the overall yield of propylene as a cracking product is significantly lower than the overall yield of ethylene. In the future global low-carbon olefin market, the propylene demand growth rate is greater than that of ethylene, so that process exploration about how to produce propylene at high yield is receiving more and more attention, and the catalytic cracking process is also the main direction of research.
The development of the deep catalytic cracking process (DCC process) is a technology for preparing gas olefin by taking heavy oil as a raw material and utilizing shape selective catalytic reaction, is considered to realize the extension of oil refining process to petrochemical industry, and opens a new way for directly preparing low-carbon olefin by taking heavy oil as a raw material. Aiming at the characteristics of heavy oil, the process adopts a reactor type of a riser and a bed layer for maximum propylene production, combines harsh operation conditions and catalyst selection, ensures that the propylene content in the composition of a cracking product can reach 21 percent, and simultaneously ensures that the yields of byproduct dry gas and coke are higher.
Chinese patent document CN101045667a discloses a combined catalytic conversion method for producing high yields of low-carbon olefins. In the method, heavy oil raw materials are contacted with a regenerated catalyst and a selected carbon deposition catalyst in a down-pipe reactor, cracked products and spent catalyst are separated, the cracked products are separated to obtain low-carbon olefins, a part of the rest products (the rest products are taken as a product extraction device) is introduced into the riser reactor to be contacted with the regenerated catalyst, oil gas and the catalyst are separated, and the oil gas is separated to obtain the low-carbon olefins. The spent catalyst enters one or more of a pre-lifting section of the down-pipe reactor, a stripper and a regenerator which are connected with the down-pipe reactor after steam stripping, and the spent catalyst and the selected carbon deposition catalyst return to the down-pipe reactor and the lifting pipe reactor after burning and regenerating. The key point of the method is that propylene generated in the down-pipe reactor is separated from the catalyst in time, so that the aim of inhibiting secondary reaction of propylene is fulfilled, and meanwhile, insufficiently cracked components are reintroduced into the riser reactor to contact with the regenerated catalyst, so that deep cracking reaction is carried out under more severe conditions, and the aim of further improving the yield of low-carbon olefin is fulfilled. However, the catalyst after the riser reaction is introduced into the catalyst pre-lifting section of the down-pipe reactor to contact with the heavy oil raw material, although the contact between the heavy oil raw material and the catalyst can be increased, the catalyst with carbon deposit has lower activity and insufficient capability of catalyzing and cracking heavy oil, so that the catalyst is simply introduced into the down-pipe, and the effect of improving the yield of propylene by improving the conversion rate of heavy oil cracking is very limited.
Chinese patent document CN101074392a discloses a method for producing propylene and high quality gasoline and diesel by two-stage catalytic cracking. The method aims at heavy hydrocarbon or various animal and plant raw materials rich in hydrocarbon, and achieves the purposes of improving propylene yield, simultaneously considering light oil yield and quality and inhibiting coke and coke generation rate by utilizing a two-stage riser catalytic process. According to the method, the first-stage riser is fed with fresh heavy raw oil, the second-stage riser is fed with gasoline and circulating oil with high olefin content, which are obtained by the reaction of the first-stage riser, and the yield of low-carbon olefin (especially propylene) is improved by deeper cracking, and meanwhile, diesel with low olefin content and higher cetane number is obtained. The method is still aimed at cracking the heavy oil hydrocarbon raw material, and the production of diesel oil is considered, so that the conversion rate of the raw material to propylene can be reduced in the process, and the yields of dry gas and coke are higher.
Chinese patent document CN102690682a discloses a catalytic cracking method and apparatus for producing propylene. The method comprises the steps of enabling heavy raw materials (comprising heavy hydrocarbon or various animal and vegetable oil raw materials rich in hydrocarbon) to contact and react with a first catalytic cracking catalyst taking Y-type zeolite as a main active component in a first riser reactor to generate oil gas; contacting light hydrocarbons (including gasoline and/or C4 hydrocarbons produced in the first riser, or gasoline fractions produced by other devices, such as one or more of catalytically cracked naphtha, catalytically cracked-stabilized gasoline, coker gasoline, visbreaker gasoline, or a mixture thereof) with a second catalytic cracking catalyst having a shape selective zeolite with a pore size of less than 0.7nm as the primary active component in a second riser reactor, and introducing the reacted oil and gas into a fluidized bed reactor in series with the second riser reactor for reaction with the catalyst. The oil gas products in the first riser and the fluidized bed reactor are collected and fractionated by a common pipeline leading-out device. Although the method can improve the propylene yield, the improvement of propylene selectivity is limited because the yield of butene is also improved. In addition, the yields of coke and dry gas are also higher with heavy hydrocarbons or various animal and vegetable oils rich in hydrocarbons as raw materials. More importantly, the method needs to adopt different catalysts to participate in the cracking reaction in the first riser reactor and the second riser reactor respectively, so that different regeneration paths are required to be arranged when the reacted spent catalyst is regenerated, and the device is complex and is not beneficial to industrial application.
Most catalytic cracking studies currently focus on the catalytic cracking of heavy oil feedstocks, or simultaneously with light hydrocarbon (gasoline) feedstocks, but the complexity of the cracking products and low propylene selectivity, as well as the high yields of dry gas and coke in pursuing relatively high propylene selectivity, remain a difficult crossover commonality problem. On the other hand, the design of these catalytic cracking processes and systems is around the nature of heavy oil feedstock, and cannot be simply applied to the cracking treatment of light fraction feedstock (such as light hydrocarbon oil product), and as the heavy oil processing and refining technology and productivity are improved, byproduct fractions output downstream may have various situations, for example, may be materials mainly containing certain types of hydrocarbons or mainly containing hydrocarbons with specific carbon numbers, how to design more feasible processes according to the compositions and properties of these materials, and at the same time, can further improve the yield of target olefins, so to speak, one direction for realizing the improvement of olefin productivity.
Disclosure of Invention
The invention provides a method for controlling multistage catalytic cracking according to a multi-zone coupling bed layer of a raw material type, which adjusts a cracking process according to the cracking characteristics of various hydrocarbon raw materials, so that different types of light hydrocarbon raw materials are cracked by using one system, and the production of high-yield light olefins is realized.
The invention provides a multi-zone-coupled bed control multi-stage catalytic cracking method according to the type of raw materials, wherein the raw materials comprise a first raw material rich in C4 hydrocarbon, a second raw material rich in C5-C6 hydrocarbon and a third raw material rich in C7-C8 hydrocarbon, a reaction device comprising a first downpipe, a second downpipe and a riser is adopted, and the method comprises the following steps:
enabling a first raw material to enter a first downlink pipe to contact with a catalyst to generate a first catalytic cracking reaction, so as to obtain a first catalytic cracking product and a first spent catalyst; enabling a second raw material to enter the second downlink pipe to perform a second catalytic cracking reaction to obtain a second catalytic cracking product and a second spent catalyst; a first catalytic cracking product and a first spent catalyst from the first downpipe, a second catalytic cracking product and a second spent catalyst from the second downpipe, and a third raw material enter the riser to perform a third catalytic cracking reaction; carrying out gas-solid separation on the product of the third catalytic cracking reaction to respectively obtain an oil gas product and a spent catalyst; the spent catalyst enters a regenerator to be regenerated after being subjected to steam stripping treatment, and then returns to participate in each catalytic cracking reaction;
The conditions of the first catalytic cracking reaction are as follows: the reaction temperature is 500-700 ℃, the catalyst-to-oil ratio is 5-40, the reaction pressure is 0.1-0.4MPa, and the residence time is 0.3-6s;
the conditions of the second catalytic cracking reaction are as follows: the reaction temperature is 480-680 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s;
the conditions of the third catalytic cracking reaction are as follows: the reaction temperature is 450-650 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s.
A process as described above wherein the reaction apparatus further comprises a fluidized bed reactor in series with the riser, the process further comprising:
the product of the third catalytic cracking reaction enters the fluidized bed reactor to generate a fourth catalytic cracking reaction, and the product of the fourth catalytic cracking reaction is subjected to gas-solid separation to respectively obtain the oil gas product and the spent catalyst;
the conditions of the fourth catalytic cracking reaction are as follows: space velocity of 2-25h -1 The linear speed of the bed layer is 0.1-0.5m/s, and the reaction temperature is 600-650 ℃.
A process as described above, wherein the first feedstock has a C4 hydrocarbon content of greater than 40%;
the content of C5-C6 hydrocarbon in the second raw material is more than 40 percent;
the content of C7-C8 hydrocarbon in the third raw material is more than 40 percent.
A method as described above, wherein the reaction temperature of the first catalytic cracking reaction is higher than the reaction temperature of the second catalytic cracking reaction; the reaction temperature of the second catalytic cracking reaction is higher than that of the third catalytic cracking reaction;
the catalyst-to-oil ratio of the first catalytic cracking reaction is greater than that of the second catalytic cracking reaction; the catalyst-to-oil ratio of the second catalytic cracking reaction is greater than that of the third catalytic cracking reaction;
the residence time of the first catalytic cracking reaction is longer than the residence time of the second catalytic cracking reaction; the residence time of the second catalytic cracking reaction is greater than the residence time of the third catalytic cracking reaction.
A method as described above, wherein the temperature of the first catalytic cracking reaction is at least 50 ℃ higher than the reaction temperature of the second catalytic cracking reaction; the temperature of the second catalytic cracking reaction is at least 40 ℃ higher than the reaction temperature of the third catalytic cracking reaction;
the ratio of the catalyst to the oil of the first catalytic cracking reaction is at least 3 greater than the ratio of the catalyst to the oil of the second catalytic cracking reaction; the catalyst-to-oil ratio of the second catalytic cracking reaction is at least 3 greater than the catalyst-to-oil ratio of the third catalytic cracking reaction;
The residence time of the first catalytic cracking reaction is at least 0.2s greater than the residence time of the second catalytic cracking reaction; the residence time of the second catalytic cracking reaction is at least 0.2s greater than the residence time of the third catalytic cracking reaction.
The method as described above, wherein prior to the first feedstock entering the first downcomer, further comprising preheating the first feedstock to 100-300 ℃; and/or the number of the groups of groups,
the second raw material is preheated to 100-250 ℃ before entering the second downgoing pipe; and/or the number of the groups of groups,
the third raw material is preheated to 100-250 ℃ before entering the riser.
The method comprises the following steps of preparing the catalyst, wherein the raw material composition of the catalyst comprises 20-50wt% of modified molecular sieve, 1-50wt% of matrix, 3-35wt% of binder and 3-15wt% of composite auxiliary agent, and the catalyst is obtained through hydrothermal aging treatment at the temperature of 500-800 ℃; wherein, the liquid crystal display device comprises a liquid crystal display device,
the modified molecular sieve is obtained by alkali treatment of a molecular sieve raw material with the mass content of at least 80% of that of the ZSM-5 molecular sieve, non-metallic element modification and metallic element impregnation modification, and hydrothermal treatment is carried out between the two modification treatments; the nonmetallic element is impregnated with at least two nonmetallic elements selected from groups IIIA, VA, VIA and VIIA of the periodic Table; the metal element is selected from at least three elements of IIA, IVB, VB, VIB, VIIB, VIII and lanthanide series in periodic Table, and at least comprises one transition metal element except the lanthanide series;
The composite auxiliary agent at least comprises inorganic acid and cellulose.
A method as described above, wherein the nonmetallic element is selected from at least two of B, P, S, cl and Br; optionally, the nonmetallic element includes at least S;
the metal element at least comprises a group IIA metal and a lanthanide series metal; alternatively, the metal element is selected from three or more of Mn, V, fe, nb, cr, mo, W, mg, ca and La.
The method as described above, wherein the regenerating process comprises:
and inputting the to-be-regenerated catalyst into a heat compensator outside the regenerator through the regenerator to perform fluidization and pre-combustion treatment, then entering the regenerator, and performing regeneration treatment under the action of regenerated gas to obtain the regenerated catalyst.
The method as described above, wherein the temperature of the regeneration treatment is 600 ℃ to 850 ℃, the oxygen concentration in the regeneration gas is 10wt% to 35wt% and the linear velocity of the regeneration gas is 0.5m/s to 30m/s.
The implementation of the invention has at least the following advantages:
1. the method has the advantages that the specific reaction conditions and flow are designed based on the cracking performance of the light hydrocarbon type contained in the raw material, the catalytic cracking reaction of different types of hydrocarbon can be enhanced in a specific manner, the depth of the cracking reaction and the conversion rate of the raw material are improved, and the selectivity and the yield of propylene are improved;
2. Aiming at the cracking principle and characteristics of light hydrocarbons with different carbon numbers, the method realizes the combination of partition cracking and deep cracking of the raw materials by the design of a downlink pipe reactor, a riser reactor and a catalyst regeneration system which are matched and cooperated with each other, is more suitable for the catalytic cracking of the light hydrocarbon raw materials or the light oil raw materials, not only meets the reaction time and the atmosphere requirement of cracking different hydrocarbons, but also reduces the residence time of intermediate products, and achieves the effect of reducing the yield of dry gas and coke;
3. the reaction conditions of the C4 hydrocarbon raw material, the C5-C6 hydrocarbon raw material and the C7-C8 hydrocarbon raw material are refined and distinguished, so that deep cracking of each raw material is realized more favorably, matching of material flow and energy flow in the whole cracking system can be realized further, stability of the whole light hydrocarbon catalytic cracking process is ensured, overall energy efficiency is improved, and industrial feasibility is realized;
4. the light hydrocarbon raw material of catalytic cracking can come from byproducts of cracking processing of heavy raw material and even products with different distillation ranges, so that the catalytic cracking method can be used as a downstream treatment process of the existing heavy raw material cracking treatment products, and can further improve the utilization rate of the heavy raw material while realizing high propylene yield.
Drawings
FIG. 1 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to yet another embodiment of the present invention;
FIG. 3 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to yet another embodiment of the present invention.
Detailed Description
In order to make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a multi-zone-coupled bed control multi-stage catalytic cracking method according to the type of raw materials, wherein the raw materials comprise a first raw material rich in C4 hydrocarbon, a second raw material rich in C5-C6 hydrocarbon and a third raw material rich in C7-C8 hydrocarbon, a first downer, a second downer and a riser which are sequentially connected in series are adopted as a reaction device, and the method comprises the following steps:
Enabling a first raw material to enter a first downlink pipe to contact with a catalyst to generate a first catalytic cracking reaction, so as to obtain a first catalytic cracking product and a first spent catalyst; enabling a second raw material to enter the second downlink pipe to perform a second catalytic cracking reaction to obtain a second catalytic cracking product and a second spent catalyst; the first catalytic cracking product and the first spent catalyst from the first downgoing pipe, the second catalytic cracking product and the second spent catalyst from the second downgoing pipe and the third raw material enter the riser to generate a third catalytic cracking reaction; carrying out gas-solid separation on the product of the third catalytic cracking reaction to respectively obtain an oil gas product and a spent catalyst; the spent catalyst enters a regenerator to be regenerated after being subjected to steam stripping treatment, and then returns to participate in each catalytic cracking reaction;
the conditions of the first catalytic cracking reaction are as follows: the reaction temperature is 500-700 ℃, the catalyst-to-oil ratio is 5-40, the reaction pressure is 0.1-0.4MPa, and the residence time is 0.3-6s;
the conditions of the second catalytic cracking reaction are as follows: the reaction temperature is 480-680 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s;
the conditions of the third catalytic cracking reaction are as follows: the reaction temperature is 450-650 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s. The agent-oil ratio of the invention refers to the agent-oil volume ratio.
The method of the invention is a method for producing propylene in high yield by catalytic cracking light hydrocarbon as raw material. Specifically, the first raw material refers to light hydrocarbon with C4 hydrocarbon as main component, the second raw material refers to light hydrocarbon with C5-C6 hydrocarbon as main component, and the third raw material refers to light hydrocarbon with C7-C8 hydrocarbon as main component.
The reaction device comprises a first downlink pipe, a second downlink pipe and a lifting pipe, and specifically, an outlet of the first downlink pipe and an outlet of the second downlink pipe are respectively communicated with an outlet of the lifting pipe. According to the invention, the down pipe is adopted for catalytic cracking reaction, so that the residence time of the raw materials and the catalyst is reduced under the action of gravity, and the generation of intermediate products is favorably inhibited; and the density distribution of the catalyst is more uniform, so that the yield of propylene is improved. In addition, the specific structural form of the riser of the present invention may be selected according to practical needs, for example, selected from one of an isopipe reactor, a variable diameter riser reactor, and an isopipe reactor.
In the method, a first raw material rich in C4 hydrocarbon enters a first downlink reactor through an inlet of the first downlink reactor, and undergoes a first catalytic cracking reaction with a catalyst in the downlink process in the first downlink to obtain a first catalytic cracking product (catalytic cracking product of the first raw material) and a first spent catalyst;
The second raw material rich in C5-C6 hydrocarbon enters a second downlink pipe through an inlet of the second downlink pipe, and a second catalytic cracking reaction occurs in the process of descending in the second downlink pipe, so as to obtain a second catalytic cracking product (catalytic cracking product of the second raw material) and a second spent catalyst;
the first catalytic cracking product and the first spent catalyst at the lower part of the first downlink pipe are output from the outlet of the first downlink pipe, the second catalytic cracking product and the second spent catalyst at the lower part of the second downlink pipe are output from the outlet of the second downlink pipe, and the two materials and the third raw material rich in C7-C8 hydrocarbon enter the riser pipe through the inlet of the riser pipe together and undergo a third catalytic cracking reaction in the process of ascending inside the riser pipe reactor. The product of the third catalytic cracking reaction is output through an outlet of the riser and then enters a gas-solid separation device for gas-solid separation, the separated gas phase is collected as an oil-gas product, and products such as propylene, ethylene and the like are obtained through treatment such as fractional distillation and refining; the separated solid phase can be stripped as spent catalyst and recycled by regenerating the regenerated catalyst. The recycling comprises the steps that the regenerated catalyst after the regeneration of the spent catalyst is respectively conveyed back to the first downlink pipe, the second downlink pipe and the lifting pipe to respectively participate in the first catalytic cracking reaction, the second catalytic cracking reaction and the third catalytic cracking reaction, so that the preparation cost of propylene can be reduced through the recycling of the spent catalyst, and the adjustment of reaction parameters, such as the reaction temperature and the catalyst-oil ratio, in the downlink pipe and the lifting pipe can be realized through controlling the quantity of the regenerated catalyst returned to the downlink pipe and the lifting pipe. It should be emphasized that, before the spent catalyst obtained by gas-solid separation is regenerated, the spent catalyst downstream is stripped by the upward stripping gas (such as water vapor) to adsorb the oil gas product on the surface, and the vapor adsorbed with the oil gas product can rise into the gas-solid separation device under the action of the stripping gas to be collected as the oil gas product for fractionation and refining.
The method can divide light hydrocarbon into different hydrocarbon raw materials according to the number of carbon atoms by utilizing a designed system through the control of the technological process and the conditions to carry out the catalytic cracking reaction in a partitioned way, thereby further improving the yield and the selectivity of propylene and reducing the generation of coke and dry gas in the reaction.
In the specific implementation process, the first raw material rich in C4 hydrocarbon and water vapor enter the first downlink pipe together according to a certain proportion (for example, the mass ratio of the first raw material to the water vapor is 1:0.1-3), and the water vapor can play a role in partial pressure to maintain a more proper cracking atmosphere of the downlink pipe. After the first raw material enters the first downpipe, the first catalytic cracking reaction, specifically, the catalytic cracking of the first raw material, is carried out by controlling the reaction temperature to be 500-700 ℃, the catalyst-oil ratio to be 5-40, the reaction pressure to be 0.1-0.4MPa and the residence time to be 0.2-6s, and the catalyst is converted into a first spent catalyst.
The second raw material rich in C5-C6 and water vapor (for example, the mass ratio of the second raw material to the water vapor is 1:0.1-3) enter a second downlink pipe together, and the second catalytic cracking reaction is carried out under the conditions of the reaction temperature of 480-680 ℃, the catalyst-oil ratio of 3-30, the reaction pressure of 0.1-0.35MPa and the residence time of 0.3-4 s. Specifically, the second raw material is subjected to a second catalytic cracking reaction under the action of a catalyst to obtain a product of the second catalytic cracking reaction (a second catalytic cracking product and a second spent catalyst).
Then, the first catalytic cracking product, the first spent catalyst, the second catalytic cracking product, the second spent catalyst, a third raw material rich in C7-C8 and water vapor (for example, the mass ratio of the third raw material to the water vapor is 1:0.1-3) enter a riser together, and the third catalytic cracking reaction occurs under the conditions of the reaction temperature of 450-650 ℃, the catalyst-oil ratio of 3-30, the reaction pressure of 0.1-0.35MPa and the residence time of 0.2-4 s. And (3) carrying out gas-solid separation on the product of the third catalytic cracking reaction to respectively obtain light oil gas and spent catalyst.
Because the low-carbon-number hydrocarbon is relatively difficult to crack, the invention firstly cracks the C4 hydrocarbon and the C5-C6 hydrocarbon, introduces the generated catalytic cracking product into the C7-C8 hydrocarbon to crack together with the C7-C8 hydrocarbon, is beneficial to increasing the cracking time of the C4 hydrocarbon and the C5-C6 hydrocarbon, and promotes the deep cracking of the respective catalytic cracking products of the C4 hydrocarbon and the C5-C6 hydrocarbon, thereby further increasing the yield of the low-carbon hydrocarbon, especially propylene, and simultaneously further inhibiting the dry gas and coke output.
The first raw material, the second raw material and the third raw material may be preheated before entering the first downgoing pipe, the second downgoing pipe and the riser respectively, and then the preheated first raw material enters the first downgoing pipe to participate in the first catalytic cracking reaction, the preheated second raw material enters the second downgoing pipe to participate in the second catalytic cracking reaction, and the preheated third raw material enters the riser to participate in the third catalytic cracking reaction. Specifically, the first feedstock may be preheated to 100-300 ℃, the second feedstock may be preheated to 100-250 ℃, and the third feedstock may be preheated to 100-250 ℃.
The invention takes light hydrocarbon as raw materials, can come from fractions or oil products of different processes, the raw materials rich in C4 hydrocarbon, raw materials rich in C5-C6 hydrocarbon and raw materials rich in C7-C8 hydrocarbon are respectively introduced into a first down pipe, a second down pipe and a riser as first raw materials, the second raw materials and third raw materials, the process conditions are respectively controlled to realize the zonal reaction of the raw materials, the first catalytic cracking reaction and the second catalytic cracking reaction are respectively realized in the first down pipe and the second down pipe aiming at the C4 hydrocarbon and the larger C5-C6 hydrocarbon with relatively higher cracking difficulty, the cracked materials are respectively sent into the riser connected with the first down pipe and the second down pipe in series, the third catalytic cracking reaction is jointly implemented with the C7-C8 hydrocarbon feed, if necessary, the raw materials can be continuously sent into a subsequent fluidized bed reactor connected in series for further deep cracking, and the operating conditions of the riser and the fluidized bed reactor can be more flexibly controlled to improve the conversion and the conversion rate of the propylene are improved on the basis of implementing the C4 hydrocarbon and the C5-C6 hydrocarbon cracking reaction. Therefore, the method of the invention not only can set more proper cracking conditions according to the difference of raw materials to improve propylene selectivity, but also can improve propylene yield and increase the conversion rate of the raw materials. The zonal reaction of the feedstock also reduces the residence time of the feedstock and reduces the formation of dry gas and coke.
In addition, the light hydrocarbon raw material can be derived from various light hydrocarbon byproducts after cracking treatment of the heavy oil, and is introduced into the cracking system according to the composition condition of the light hydrocarbon raw material, and the conversion rate of the heavy oil can be effectively improved by cracking treatment of the byproducts after cracking treatment of the heavy oil, so that the conversion of comprehensive production of high-added-value chemicals is realized.
Further, the reaction apparatus of the present invention may further comprise a fluidized bed reactor in series with the riser, i.e. the outlet of the riser is in communication with the inlet of the fluidized bed reactor.
In order to avoid incomplete cracking degree of the third catalytic cracking reaction, the invention can also ensure that the product of the third catalytic cracking reaction is output from the outlet of the lifting pipe and then enters the fluidized bed reactor to carry out the fourth catalytic cracking reaction on the basis of the method. Specifically, fourthThe conditions of the catalytic cracking reaction are as follows: space velocity of 2-25h -1 The linear speed is 0.1-0.5m/s, and the reaction temperature is 600-650 ℃.
In the fourth catalytic cracking reaction, the product of the third catalytic cracking reaction is further catalytically cracked in the bed layer of the fluidized bed reactor to obtain the product of the fourth catalytic cracking reaction. Under the action of the fluidizing gas, in the process that the product of the fourth catalytic cracking reaction goes upward through a settler (section), spent catalyst particles are separated and fall back to a stripping section, and cracked oil gas products are output from the top of the settler and are used as cracking products, or the cracking products are sent to a subsequent refining and separating process to respectively collect products such as ethylene, propylene and the like; the catalyst to be regenerated which falls back to the stripping section is stripped to remove oil gas products adsorbed on the surface under the action of lifting gas, then is discharged out of the reaction device, is sent into a regenerator to be regenerated, and the regenerated catalyst (regenerated catalyst) is returned to each down pipe for recycling. The recycling comprises the steps of respectively conveying regenerated catalysts after regenerating spent catalysts back to the first downlink pipe, the second downlink pipe and the lifting pipe to participate in the first catalytic cracking reaction, the second catalytic cracking reaction and the third catalytic cracking reaction, or respectively conveying the regenerated catalysts back to the first downlink pipe, the second downlink pipe, the lifting pipe and the fluidized bed to participate in the first catalytic cracking reaction, the second catalytic cracking reaction, the third catalytic cracking reaction and the fourth catalytic cracking reaction.
The method comprises the steps that a first raw material rich in C4 hydrocarbon and a catalyst are subjected to a first catalytic cracking reaction in a first downlink pipe by adopting a reactor comprising the first downlink pipe, a second downlink pipe, a lifting pipe and a fluidized bed reactor, so that a first catalytic cracking product and a first spent catalyst are generated; and (3) feeding a second raw material rich in C5-C6 hydrocarbon into a second downlink pipe, and carrying out a second catalytic cracking reaction on the second raw material under the action of a catalyst in the second downlink pipe to obtain a second catalytic cracking product and a second spent catalyst. And then, the first catalytic cracking product, the first spent catalyst, the second catalytic cracking product, the second spent catalyst and a third raw material rich in C7-C8 hydrocarbon enter a riser together to perform a third catalytic cracking reaction, so that products of the third catalytic cracking reaction (the third catalytic cracking product and the third spent catalyst) are obtained. Finally, the product of the third catalytic cracking reaction from the riser enters a fluidized bed reactor to carry out a fourth catalytic cracking reaction, so that the catalytic cracking product of the first raw material, the catalytic cracking product of the second raw material and the catalytic cracking product of the third raw material continue deep cracking. The product of the fourth catalytic cracking reaction in the fluidized bed reactor is respectively collected after gas-solid separation in a settling section of the fluidized bed reactor, gas phase is collected to be oil gas product obtained by raw material cracking, solid phase is collected to be spent catalyst, and the spent catalyst can be recycled as regenerated catalyst after regeneration treatment.
After the fluidized bed reactor is connected in series with the outlet of the riser, under the reaction conditions of the fluidized bed reactor defined by the invention, the deep cracking of the first raw material, the second raw material and the third raw material can be further ensured, thereby further increasing the yield of low-carbon olefin, especially propylene, and further inhibiting the production of dry gas and coke.
In the process of the fourth catalytic cracking reaction, a product of the fourth catalytic cracking reaction has a certain residence time in a sedimentation section and a transfer pipeline in the fluidized bed reactor, the temperature is higher, a considerable secondary reaction mainly including thermal cracking reaction can occur, and the yield of dry gas and coke is increased. Specifically, the gas-solid phase of the product of the fourth catalytic cracking reaction is rapidly separated by utilizing the gas-solid rapid separation device, so that the progress of side reaction is inhibited, and the dilute phase space volume of the sedimentation section is properly reduced. There are various forms of gas-solid quick separating member, and there are commonly used semi-circular cap-shaped separating member, T-shaped member or primary cyclone separator. In one embodiment, the gas-solid rapid separation means may be a primary cyclone, shortening the distance between the riser outlet of the primary cyclone and the cyclone inlet at the top of the settling section significantly reduces the occurrence of secondary reactions, increases the oil and gas product yield, and reduces the rate of coke and dry gas production. Meanwhile, a settling section is arranged in a dilute phase zone at the upper part of the fluidized bed reactor, so that gas and solid phases in the product of the fourth catalytic cracking reaction can be rapidly separated.
Further, nozzles may be provided at the inlets of the first downcomers, the second downcomers, the riser and the fluidized bed reactor, through which the materials entering the downcomers, the riser or the fluidized bed reactor are brought into mixed contact, and the materials are moved upward with a preset residence time while being catalytically cracked. The nozzle may be in various forms, and may be selected according to practical needs, for example, in the form of a hollow cone nozzle, a solid cone nozzle, a square nozzle, a rectangular nozzle, an oval nozzle, a fan nozzle, a cylindrical flow (direct current) nozzle, a two-fluid nozzle, a multi-fluid nozzle, or the like.
In addition, the sharp included angle between the inlets of the first downgoing pipe, the second downgoing pipe and the lifting pipe and the internal axis of the first downgoing pipe, the second downgoing pipe and the lifting pipe is 30 degrees to 60 degrees, and the angle can enable materials entering the reactor to be mixed more fully, so that cracking can be more fully achieved.
The present invention does not impose excessive restrictions on the first feedstock rich in C4 hydrocarbons, the second feedstock rich in C5-C6 hydrocarbons, and the third feedstock rich in C7-C8 hydrocarbons, and may be, for example, naphtha, catalytic pyrolysis gasoline, pressurized gas oil, steam cracking byproducts or light pyrolysis gasoline, byproducts of a fluidized catalytic cracker or cracker, byproducts of a methanol-to-olefin apparatus, or the like. The catalytic cracking method of the present invention is carried out as the first feedstock or the second feedstock or the third feedstock depending on the contents of C4 hydrocarbons, C5-C6 hydrocarbons and C7-C8 hydrocarbons therein. Of course, C4 hydrocarbons, C5-C6 hydrocarbons and C7-C8 hydrocarbons may also be selected as the first feedstock, the second feedstock or the third feedstock, respectively.
The mass content of C4 hydrocarbon in the first raw material is not less than 40%, the mass content of C5-C6 hydrocarbon in the second raw material is not less than 40%, and the mass content of C7-C8 hydrocarbon in the third raw material is not less than 40%.
Further, in order to ensure deep cracking of the raw material and ensure yield and selectivity of propylene, the reaction conditions of each reaction may be further defined on the basis of the aforementioned first catalytic cracking reaction condition, second catalytic cracking reaction condition and third catalytic cracking reaction condition. Specifically, the reaction temperature of the first catalytic cracking reaction is made higher than the reaction temperature of the second catalytic cracking reaction, which is made higher than the reaction temperature of the third catalytic cracking reaction; the catalyst-oil ratio of the first catalytic cracking reaction is larger than that of the second catalytic cracking reaction, and the catalyst-oil ratio of the second catalytic cracking reaction is larger than that of the third catalytic cracking reaction; the residence time of the first catalytic cracking reaction is made longer than the residence time of the second catalytic cracking reaction, which is made longer than the residence time of the third catalytic cracking reaction.
Specifically, the temperature of the first catalytic cracking reaction is at least 50 ℃ higher than the reaction temperature of the second catalytic cracking reaction; the temperature of the second catalytic cracking reaction is at least 40 ℃ higher than the reaction temperature of the third catalytic cracking reaction; the catalyst to oil ratio of the first catalytic cracking reaction is at least 3 greater than the catalyst to oil ratio of the second catalytic cracking reaction (refers to the difference between the catalyst to oil ratio of the first catalytic cracking reaction and the catalyst to oil ratio of the second catalytic cracking reaction); the ratio of the catalyst to the oil of the second catalytic cracking reaction is at least 3 greater than the ratio of the catalyst to the oil of the third catalytic cracking reaction; the residence time of the first catalytic cracking reaction is at least 0.2s greater than the residence time of the second catalytic cracking reaction; the residence time of the second catalytic cracking reaction is at least 0.2s greater than the residence time of the third catalytic cracking reaction.
As a preferred embodiment, the conditions of the first catalytic cracking reaction are as follows: the reaction temperature is 600-680 ℃, the catalyst-to-oil ratio is 20-40, and the residence time is 2-4s; the conditions of the second catalytic cracking reaction are as follows: the reaction temperature is 530-600 ℃, the agent-oil ratio is 15-25, and the residence time is 2-3s; the conditions of the third catalytic cracking reaction are as follows: the reaction temperature is 480-530 ℃, the agent-oil ratio is 15-25, and the residence time is 2-4s. Thereby further realizing the matching of the material flow and the energy flow in the whole cracking system, ensuring the stability of the whole light olefin catalytic cracking process, improving the overall energy efficiency and realizing the industrial feasibility.
In the practical application process, the determination of the specific operation conditions of the second downcomers, the risers and the fluidized bed reactor can be further adjusted according to the changes of the first catalytic cracking product and the second catalytic cracking product so as to realize the deep cracking of the raw materials.
The invention can further improve propylene yield by selecting a specific catalyst which can simultaneously perform catalytic cracking on a first raw material rich in C4 hydrocarbon, a second raw material rich in C5-C6 hydrocarbon and a third raw material rich in C7-C8 hydrocarbon.
Specifically, the catalyst is a catalyst capable of simultaneously catalytically cracking alkane and alkene, utilizes a plurality of metal elements and nonmetal elements to modify a molecular sieve, and enables the acid strength and the acid density of a molecular sieve carrier to be controlled in a targeted manner, so that the catalyst has different types of acid centers such as super acid, strong acid, weak acid and the like, can simultaneously promote the adsorption capacity of alkene and alkane, enables the simultaneous catalytic cracking of alkane and alkene to be possible, provides higher total conversion rate of alkane and alkene, and simultaneously provides better propylene yield. By means of the synergistic effect of the specific composite auxiliary agents, the catalyst wear resistance is improved and the service life of the catalyst is prolonged while the catalytic performance is ensured.
The raw materials of the catalyst comprise 20-50wt% of modified molecular sieve, 1-50wt% of matrix, 3-35wt% of binder and 3-15wt% of composite auxiliary agent, and the catalyst is obtained by hydrothermal aging treatment at 500-800 ℃; wherein the modified molecular sieve is obtained by alkali treatment of a molecular sieve raw material with the mass content of at least 80% of that of the ZSM-5 molecular sieve, non-metallic element modification and metallic element impregnation modification, and hydrothermal treatment is carried out between the two modification treatments; the nonmetallic element is impregnated with at least two nonmetallic elements selected from groups IIIA, VA, VIA and VIIA of the periodic Table; the metal element is selected from at least three elements of IIA, IVB, VB, VIB, VIIB, VIII and lanthanide series of the periodic Table, and at least comprises one transition metal element except the lanthanide series; the composite auxiliary agent at least comprises inorganic acid and cellulose.
Wherein, the molecular sieve raw material is HZSM-5 molecular sieve which is obtained by converting ZSM-5 molecular sieve through conventional hydrogenation treatment and is mainly ZSM-5 molecular sieve, and the molecular sieve raw material is also covered in the range of the molecular sieve raw material. The ZSM-5 molecular sieve has good shape selectivity in pore structure, and is more suitable for impregnating various metals and nonmetal. Therefore, the ZSM-5 molecular sieve content in the molecular sieve raw material selected by the catalyst is at least 80 percent in terms of catalyst quality and cost.
The grain diameter and the silicon-aluminum ratio of the molecular sieve raw material are in a proper range, which is more beneficial to providing proper acid center and alkali center as a carrier, thereby being more beneficial to loading of metal and nonmetal elements. In one possible embodiment, it is advantageous to select the nanoscale molecular sieve particles, e.g., ZSM-5 particles having a size of about 500 to 3000nm, e.g., 1500 to 2000nm, and a silica to alumina ratio of about 90 to 110, e.g., about 100. The molecular sieve raw materials can be purchased commercially or entrusted to production according to design requirements, and can also be synthesized by oneself.
In the process of modifying the molecular sieve raw material, desilication reaming is realized on the molecular sieve raw material through alkali treatment, coking of catalyst orifices is avoided, and ammonium exchange treatment can be implemented after reaming to restore acidity of the molecular sieve, but ammonium exchange is not necessarily required. The alkali solution used for the alkali treatment may be a conventional alkali solution used for this purpose in the art, and is selected from, for example, one or two of sodium hydroxide solution, potassium hydroxide solution, aqueous ammonia and the like; the ammonium ion exchange reagent used may be one or both of those conventional in the art for this purpose and selected from, for example, ammonium nitrate and ammonium chloride, etc.
Specifically, the following operations may be adopted: firstly mixing molecular sieve raw materials with 0.2-1.0mol/L alkaline solution according to the mass ratio of 1:4-8, exchanging for 1-5h at 70-90 ℃, then washing the molecular sieve to be neutral, drying for 3-12h at 60-150 ℃ and roasting for 2-6h at 400-600 ℃. Mixing the molecular sieve treated by the alkaline solution with 0.5-1.2mol/L ammonium ion-containing solution (such as 1mol/L ammonium nitrate solution) according to the mass ratio of 1:4-10, exchanging for 1-5h at 70-90 ℃, washing to be neutral, then drying for 3-12h at 60-150 ℃ and roasting for 2-6h at 400-600 ℃.
Subsequently, the alkali-treated molecular sieve feedstock is impregnated with a plurality of nonmetallic elements and metallic elements.
The nonmetallic elements are selected from at least two elements in IIIA, VA, VIA and VIIA of the periodic Table, for example, can be selected from two of P, B, S, cl and Br, such as P or B loaded on the molecular sieve, so that the hydrothermal stability of the molecular sieve can be improved, and deacidification is avoided; the loading of S on the molecular sieve is beneficial to improving acidity.
All three or more metal elements are chosen to include acidic metals and basic metals, advantageously at least three metal elements, and include one group IIA metal and one lanthanide metal. Briefly, the metal element is selected from three or more of the above groups of the periodic table, including alkaline earth metals, lanthanide metals, and transition metals of the listed sub-groups, and may be specifically selected from three or more of Mn, V, fe, nb, cr, mo, W, mg, ca and La, for example, according to the above-described principle. In view of the fact that the conversion rate of the alkane-alkene blending material is mainly limited by the conversion rate of alkane, the synergistic effect of various metal elements is selected according to the principle, the adsorption capacity of alkane on a catalyst is improved, and the simultaneous catalytic cracking of alkane and alkene becomes possible, so that the conversion rate of alkane and alkene and the propylene yield are improved.
When modifying a molecular sieve, although the non-metal element and the metal element have different loading sites, there is no adsorption competition relationship between the non-metal element and the metal element, but separate impregnation is generally selected due to solubility or the like. For example, the nonmetallic elements may be impregnated first, then the metallic elements may be impregnated, and the synchronous impregnation may be generally selected or the stepwise impregnation may be selected depending on the solubility between the metallic elements and between the nonmetallic elements.
In the case of carrying out the metal element impregnation modification, for some of the metal salts which are relatively insoluble, the corresponding salts of the metal may be dissolved in the dispersant to increase the solubility thereof. For example, a dispersing agent (e.g., a solution of citric acid and/or oxalic acid) having a total concentration of about 0.1 to 4mol/L may be used to dissolve the corresponding salt of the metal element to prepare an impregnating solution, and then the molecular sieve may be subjected to impregnation modification of the metal element. Too low a concentration of the dispersant may not achieve the dispersing effect, and too high a concentration may affect the impregnating effect. The mass ratio of the impregnating solution to the molecular sieve can be set according to the expected loading, for example, the mass ratio can be 0.2-0.8:1.
In the preparation of the catalyst, too much or too little loading of non-metallic elements and metallic elements can affect the catalytic effect of the catalyst. For example, if the loading of the metal element/nonmetal element is excessive, the dispersibility is poor, and the catalyst tends to accumulate in the catalyst pores to form coke. If the loading of the metal element/nonmetal element is too small, the desired catalytic effect cannot be achieved even if the catalytic reaction time is prolonged. Thus, the loading of each nonmetallic element in the catalyst is about 0.05 to 5wt% and the loading of each metallic element is about 0.1 to 10wt%, based on the mass of the catalyst.
When nonmetallic modification and metal modification treatment are carried out, no matter how the sequence is, hydrothermal treatment is needed between two types of modification treatment to dredge molecular sieve channels, so that the molecular sieve channels are favorable for loading of next type of modification elements. The conditions of the hydrothermal treatment are not particularly limited, and the treatment is generally carried out in an environment at a temperature of less than 550 ℃.
Typically, each impregnation is followed by aging, drying and calcination. The aging temperature after each impregnation is 0-50deg.C, such as 20-40deg.C, and the aging time is 2-20 hr, such as 4-12 hr; the drying temperature is 50-160deg.C, such as 70-120deg.C, and the drying time is 2-20 hr, such as 3-12 hr; the calcination temperature is 300-800 ℃, e.g. 400-600 ℃, and the calcination time is 1-10 hours, e.g. 2-6 hours.
The proper amount of matrix material can provide the dispersion environment of the carrier and the active ingredients, increase the mechanical strength and carbon capacity of the catalyst, prevent the catalyst from coking and inactivating, and prolong the service life of the catalyst. Meanwhile, the required catalyst is finally obtained by utilizing the bonding effect of the bonding agent. In addition, the inorganic acid and the cellulose are adopted for synergistic action in the composite auxiliary agent, so that the abrasion resistance of the auxiliary agent can be improved.
If the content of the composite auxiliary agent is too low, the loss amount of the catalyst is increased, but if the content of the composite auxiliary agent is too high, the viscosity of the raw material is too high, and the molding is not easy. The present invention therefore defines the content of the compounding ingredients, the sum of the mass fractions of all compounding ingredients being about 3 to 15wt%, for example 3 to 12wt%.
In order to further ensure that the acidity of the catalyst is not easily changed and to ensure the pore channel structure and mechanical properties of the catalyst, the types and contents of the inorganic acid and cellulose in the composite auxiliary agent can be properly adjusted and selected within the above-mentioned set ranges, and the mass fraction of the inorganic acid is generally not more than 2wt%, preferably based on the mass of the catalyst, and can include common inorganic acids: sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, etc., and under comprehensive consideration, the inorganic acid may be selected from one of nitric acid and hydrochloric acid; and the cellulose may be one selected from methyl cellulose and ethyl cellulose, but is not limited thereto.
In addition, the selection of the components of the binder and the matrix is not particularly limited. The adhesive comprises sesbania powder, has strong adhesive property, can better play the role of the adhesive, and can also comprise silica sol and/or aluminum sol, but is not limited to the above.
The matrix may be kaolin, pseudo-boehmite, or a group IVB metal oxide. The IVB metal oxide can increase the pore structure of the matrix, thereby prolonging the reaction path of the alkane-alkene blending material in the catalyst and leading the catalyst to better play the effect. For example, it may be an oxide of Ti and/or Zr.
After the raw material components are selected and modified, the catalyst preparation can be completed according to the conventional operation. The modified molecular sieve, the matrix, the binder and the composite auxiliary agent can be mixed and pulped to obtain slurry with the solid content of about 20-50wt%, and the catalyst microsphere with the particle size of about 20-200nm can be obtained by drying (such as spray drying) and molding in general, then the catalyst microsphere can be subjected to multi-step drying and roasting operations, such as drying at about 20-50 ℃ for 12-50 hours, drying at 100-200 ℃ for 12-50 hours and roasting at 500-700 ℃ for 1-12 hours, thus obtaining the catalyst, and further hydrothermal aging treatment, such as hydrothermal aging treatment at 500-800 ℃.
Because the invention aims at light hydrocarbon raw materials, the coke attached to the surface of the spent catalyst after each stage of catalytic cracking reaction is less, and the heat of burning the coke is insufficient to provide the heat of regenerating the spent catalyst. In order to ensure efficient regeneration of the spent catalyst, the invention adopts a regenerator comprising a heat compensator, in particular, the heat compensator is arranged outside the regenerator, a spent catalyst inlet of the regenerator is communicated with a spent catalyst outlet of a stripping section and is used for receiving stripped spent catalyst, a spent catalyst outlet of the regenerator is communicated with a spent catalyst inlet of the heat compensator through a spent catalyst conveying pipeline, a precombustion catalyst outlet of the heat compensator is communicated with a precombustion catalyst inlet of the regenerator through a precombustion catalyst conveying pipeline, and a regenerated catalyst outlet of the regenerator is respectively communicated with inlets of a first downlink pipe, a second downlink pipe and a lifting pipe, or a regenerated catalyst outlet of the regenerator is respectively communicated with inlets of the first downlink pipe, the second downlink pipe, the lifting pipe and a fluidized bed reactor. In addition, the inside of the heat compensator is provided with a fuel distributor, a combustion improver distributor and a fluidization and pre-combustion medium distributor, wherein the fuel distributor is used for releasing and spraying fuel to the spent catalyst in the heat compensator, the combustion improver distributor is used for releasing and spraying combustion improver to the spent catalyst in the heat compensator, and the fluidization and pre-combustion medium distributor is used for enabling the spent catalyst in the heat compensator to be in a fluidization state and enabling the spent catalyst to be pre-combusted.
Hereinafter, the regeneration treatment of the present invention will be described by taking a spent catalyst after the fourth catalytic cracking reaction as an example.
In the fluidized bed reactor, after gas-solid separation of the product of the fourth catalytic cracking reaction in the settling section of the fluidized bed reactor, the gas-phase cracked product is collected as oil gas product, and the solid spent catalyst is stripped by the ascending steam in the descending process and then is output from the fluidized bed reactor through the spent catalyst outlet of the fluidized bed reactor, and enters the regenerator through the spent catalyst inlet of the regenerator. The steam stripping treatment of the catalyst to be regenerated is to collect the gas-phase pyrolysis products attached to the surface of the catalyst to be regenerated by utilizing steam, and the gas-phase pyrolysis products collected by the steam stripping treatment can enter a gas-solid separation device to be collected as oil gas products.
The spent catalyst (whole spent catalyst or partial spent catalyst) in the regenerator firstly enters the heat compensator through a spent catalyst conveying pipeline, then the fuel distributor and the combustion improver distributor uniformly distribute fuel and combustion improver on the surface of the spent catalyst, and the fluidization and pre-combustion medium distributor enables the spent catalyst with the fuel distributed on the surface to be in a fluidization state and pre-burn under low-temperature oxygen-deficient condition, so that the spent catalyst is converted into a pre-combustion catalyst with coke on the surface. It will be appreciated that the concentration of coke attached to the spent catalyst is maximally homogenized during fluidization of the spent catalyst by the fluidizing medium.
And then, the pre-burning catalyst enters the regenerator through a pre-burning catalyst conveying pipeline, is uniformly distributed in a bed layer in the regenerator, is introduced into regenerated gas to perform a burning exothermic reaction, supplies heat required by the regeneration of the catalytic cracking catalyst to obtain a regenerated catalyst, and the regenerated catalyst is output from the regenerator and returns to the reactor through conveying pipelines communicated with the reactor to be recycled. In the process, because coke is uniformly distributed on the surface of the pre-combustion catalyst, the pre-combustion catalyst is not deactivated due to local overheating when being combusted in the regenerator, the control of homogenization and the coking process is realized to the greatest extent, the regeneration performance and the physical and chemical properties of the catalyst can be well maintained, and the efficient regeneration of the spent catalyst is facilitated.
According to the invention, the pre-burning (i.e. post combustion) heat supplementing is carried out on the spent catalyst, so that on one hand, the heat supplementing is carried out on the spent catalyst, on the other hand, the severe combustion of the spent catalyst under the action of main wind (i.e. regenerated gas) can be reduced, the local temperature is too high, the structure of the catalyst is damaged, catalyst particles are broken, the catalyst is deactivated, and the heat balance and the production capacity of the whole device are improved. In the process of matching the heat compensator and the regenerator, the preheating and the post combustion are carried out simultaneously, the operation is continuous, and the uniformly mixed catalyst is subjected to mild and stable combustion, so that the structural property and the physicochemical property of the catalyst are protected.
In the heat compensator, the operation temperature is 400-800 ℃, for example, can be 500-600 ℃, and the absolute pressure is 0.05-0.4 MPa. In addition, the heat compensator is in a low oxygen state, the linear velocity of low oxygen-containing gas is 0.3-0.5m/s, and the oxygen content in the low oxygen-containing gas is 0.005-7wt%, and further 0.1-1wt%. By controlling the oxygen content in the heat compensator to be in a certain rangeThe extent of pre-combustion is well controlled, thereby ensuring the catalytic performance of the regenerated catalyst. During actual operation, the oxygen content in the external supplemental heater may be maintained by controlling the linear velocity of the pre-combustion medium (e.g., air). In addition, the fuel may be a CO combustion improver (using Al 2 O 3 Or SiO 2 -Al 2 O 3 A CO combustion improver comprising a carrier and a noble metal such as platinum or palladium supported thereon as a main active component); the fluidizing medium may be steam and the pre-combustion medium may be air.
In the regenerator, the regeneration temperature is 600-850 ℃, preferably 650-750 ℃, and the linear velocity of the regenerated gas is 0.5-30 m/s; the regeneration gas is an oxygen-containing gas having an oxygen concentration of 10wt% to 35wt%, preferably 15wt% to 25 wt%.
Further, valves may be provided on the spent catalyst transfer piping and the pre-combustion catalyst transfer piping so that the amount of catalyst and the operation temperature in the regenerator and the heat compensator are maintained stable, and independent operations may be performed as necessary.
The method for controlling multi-stage catalytic cracking by the multi-zone-coupled bed according to the type of raw materials of the present invention is described in detail below by way of specific examples.
Example 1
FIG. 1 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to an embodiment of the present invention. As shown in fig. 1, the system comprises a first downcomer 1, a second downcomer 2, a riser 3, a fluidized bed reactor 4, a regenerator 5 and a heat compensator 6 external to the regenerator 5. The outlet of the first downgoing pipe 1 and the outlet of the second downgoing pipe 2 are respectively communicated with the inlet of the riser pipe 3 through a pipeline, the outlet of the riser pipe 3 is communicated with the inlet of the fluidized bed reactor 4 through a pipeline, the spent catalyst outlet of the fluidized bed reactor 4 is communicated with the spent catalyst inlet of the regenerator 5 through a pipeline, the spent catalyst outlet of the regenerator 5 is communicated with the spent catalyst inlet of the heat compensator 6 through a spent catalyst conveying pipeline, and the pre-combustion catalyst outlet of the heat compensator 6 is communicated with the pre-combustion catalyst inlet of the regenerator 5 through a pre-combustion catalyst conveying pipeline. The regenerated catalyst outlet of the regenerator 5 is respectively communicated with the inlets of the first downlink pipe 1, the second downlink pipe 2 and the lifting pipe 3, and is used for inputting and returning the regenerated catalyst a to the first downlink pipe 1, the second downlink pipe 2 and the third downlink pipe 3 for recycling.
Inside the fluidized bed reactor 4, a settling section at the upper part of the fluidized bed layer is provided with a gas-solid separation device 7 (for performing gas-solid separation on the product of the fourth catalytic cracking reaction), and the lower part of the fluidized bed layer is provided with a steam stripping device 8 (for stripping the spent catalyst b1 descending inside the fluidized bed reactor); an oil gas product outlet is arranged at the top of the fluidized bed reactor 4 and is used for collecting the oil gas product c separated by the gas-solid separation device for further fractionation and refining; a lifting gas inlet is provided at the bottom of the fluidized bed reactor 4 for feeding lifting gas d to the steam stripping device 8 to strip the downstream spent catalyst b 1.
Inside the regenerator 5, in particular above the catalyst inlet to be regenerated, there is provided a fuel distributor; a flue gas outlet is arranged at the top of the regenerator 5 and is used for discharging flue gas e generated by burning in the regeneration treatment; a regeneration gas inlet is arranged at the bottom of the regenerator 5 and is used for introducing regeneration gas f into the regenerator 5 to assist the combustion and regeneration of the pre-combustion catalyst.
The heat compensator 5 is internally provided with a fuel distributor (not shown), a combustion improver distributor (not shown), and a fluidization and pre-combustion medium distributor (not shown), wherein the fuel distributor is used for releasing and spraying fuel to the spent catalyst in the heat compensator 5, the combustion improver distributor is used for releasing and spraying combustion improver to the spent catalyst in the heat compensator 5, and the fluidization and pre-combustion medium distributor is used for enabling the spent catalyst in the heat compensator 5 to be in a fluidization state and pre-burning the spent catalyst.
The system shown in fig. 1 is used for catalytic cracking of light hydrocarbons, and is briefly described as follows:
the preheated first raw material A, the first catalyst and water vapor enter the first downlink pipe 1 through the inlet of the first downlink pipe 1, and the first raw material A and the first catalyst undergo a first catalytic cracking reaction in the process of descending in the first downlink pipe 1 to generate a product A1 (a first catalytic cracking product and a first spent catalyst) of the first catalytic cracking reaction.
The preheated second raw material B, the first catalyst and the water vapor enter the second downlink pipe 2 together, the second raw material B undergoes a second catalytic cracking reaction under the action of the first catalyst in the process of descending in the second downlink pipe 2, and a product B1 (a second catalytic cracking product and a second spent catalyst) of the second catalytic cracking reaction is generated.
The first catalytic cracking product and the first spent catalyst are output through the outlet of the first downpipe 1, the second catalytic cracking product and the second spent catalyst are output through the outlet of the second downpipe 2, the two materials flow through the inlet of the riser 3 and enter the riser 3 together with the preheated third raw material C and water vapor, the first catalytic cracking product, the second catalytic cracking product and the third raw material C generate a third catalytic cracking reaction in the process of ascending inside the riser 3, and the products C1 (the third catalytic cracking product and the third spent catalyst) of the third catalytic cracking reaction are obtained.
The product C1 of the third catalytic cracking reaction is output through the outlet of the riser 3 and then enters the fluidized bed reactor 4 through the inlet of the fluidized bed reactor 4 to carry out the fourth catalytic cracking reaction.
In the fluidized bed reactor 4, the product b2 of the fourth catalytic cracking reaction can go up to the gas-solid separation device 7 of the sedimentation section for gas-solid separation under the action of the fluidizing gas and the lifting gas d, the separated oil-gas phase is collected as an oil-gas product c at an outlet of the oil-gas product, and then the oil-gas product c is fractionated and refined to obtain propylene, ethylene and the like respectively; the separated solid-phase spent catalyst b1 and the residual spent catalyst b1 (spent catalyst which does not enter the gas-solid separation device) drop to a steam stripping device 8, the oil-gas phase on the surface b1 of the spent catalyst is adsorbed and stripped by steam under the action of a lifting gas d, and then the stripped spent catalyst b3 is output from the fluidized bed reactor 4 through a spent catalyst outlet and enters the regenerator 5 through a spent catalyst inlet; while the vapor of the hydrocarbon phase carrying the spent catalyst surface will travel up the settling section to be collected as hydrocarbon product c.
The stripped spent catalyst b3 enters a complementary heater 6 through a spent catalyst conveying pipeline in the regenerator 5, and is subjected to precombustion treatment under the actions of fuel, combustion-supporting medium, fluidizing medium and precombustion medium to generate precombustion catalyst with coke uniformly distributed on the surface. The precombustion catalyst enters the regenerator 5 through a precombustion catalyst conveying pipeline, and is combusted and regenerated under the action of regenerated gas f and fuel to obtain a regenerated catalyst a. The regenerated catalyst a is respectively returned to the first downlink pipe 1, the second downlink pipe 2 and the lifting pipe 3 through regenerated catalyst conveying pipelines for recycling, and in the recycling process of the regenerated catalyst, the reaction parameters (such as reaction temperature and catalyst-oil ratio) of the first downlink pipe 1, the second downlink pipe 2 and the lifting pipe 3 can be adjusted by respectively controlling the quantity of the regenerated catalyst returned to the first downlink pipe 1, the second downlink pipe 2 and the lifting pipe 3.
The specific reaction conditions for catalytic cracking in this example are shown in the following table.
Example 2
FIG. 2 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to yet another embodiment of the present invention. As shown in fig. 2, the system of the present embodiment is different from the system shown in fig. 1 in that:
the regenerated catalyst outlet of the regenerator 5 is communicated with the inlets of the first downpipe 1, the second downpipe 2 and the riser 3, and is also communicated with the inlet of the fluidized bed reactor 4, so as to input and return the regenerated catalyst a to the first downpipe 1, the second downpipe 2, the riser 3 and the fluidized bed reactor 4 for recycling.
The method for catalytic cracking of light hydrocarbons using the system shown in fig. 2 is different from that of example 1 in that:
the regenerated catalyst a in the regenerator 5 is respectively returned to the first downpipe 1, the second downpipe 2, the riser 3 and the fluidized bed reactor 4 through regenerated catalyst conveying pipelines for recycling, and in the recycling process of the regenerated catalyst, the reaction parameters (such as reaction temperature and catalyst-oil ratio) of the first downpipe 1, the second downpipe 2, the riser 3 and the fluidized bed reactor 4 can be adjusted by respectively controlling the amounts of the regenerated catalyst returned to the first downpipe 1, the second downpipe 2, the riser 3 and the fluidized bed reactor 4.
The specific reaction conditions for this example are shown in the following table.
Example 3
FIG. 3 is a schematic diagram of a system for multi-zone coupled bed controlled multi-stage catalytic cracking by feedstock type according to yet another embodiment of the present invention. As shown in fig. 3, the system of the present embodiment is different from the system shown in fig. 1 in that:
the system in this example does not contain a fluidized bed, and the product C1 from the third catalytic cracking reaction of the riser 3 directly enters the gas-solid separation device 7 for gas-solid separation.
The method for catalytic cracking of light hydrocarbons using the system shown in fig. 3 is different from that of example 1 in that:
the product C1 from the third catalytic cracking reaction of the riser 3 directly enters a gas-solid separation device 7 for gas-solid separation under the action of lifting gas d (stripping steam), the separated oil-gas phase is collected as an oil-gas product C at an outlet of the oil-gas product, and then the oil-gas product C is fractionated and refined to obtain propylene, ethylene and the like respectively; the separated solid-phase spent catalyst b1 and the residual spent catalyst b1 (the spent catalyst which is not mixed with the hydrocarbon phase) can descend to a steam stripping device 8, the hydrocarbon phase on the surface of the spent catalyst b1 is adsorbed and stripped by steam under the action of a lifting gas d, and then the stripped spent catalyst b3 enters a regenerator 5 through an output steam stripping section and a spent catalyst inlet; while the vapor of the hydrocarbon phase carrying the spent catalyst surface will travel up the settling section to be collected as hydrocarbon product c.
The specific reaction conditions for this example are shown in the following table.
Example 4
The catalytic cracking process of the light hydrocarbon feedstock of this example is substantially the same as that of example 2, except that the first catalyst is replaced with a second catalyst.
Example 5
The catalytic cracking process of the light hydrocarbon feedstock of this example is substantially the same as that of example 2, except that the first catalyst is replaced with a third catalyst.
Comparative example 1
This comparative example 1 uses the system of example 1 to perform catalytic cracking of light hydrocarbons, differing from the process of example 1 in that: and replacing the first raw material, the second raw material and the third raw material with mixed raw materials obtained by mixing the first raw material, the second raw material and the third raw material respectively.
The specific reaction conditions for this comparative example are shown in the following table.
Comparative example 2
This comparative example 2 uses the system of example 1 to perform catalytic cracking of light hydrocarbons, and differs from the process of example 1 in that: the specific reaction conditions for catalytic cracking in this comparative example were different from those in example 1.
The specific reaction conditions for this comparative example are shown in the following table.
Comparative example 3
This comparative example 3 uses the system of example 1 to perform catalytic cracking of light hydrocarbons, and differs from the process of example 1 in that: the specific reaction conditions for catalytic cracking in this comparative example were different from those in example 1.
The specific reaction conditions for this comparative example are shown in the following table.
Comparative example 4
This comparative example 4 uses the system of example 2 to perform catalytic cracking of light hydrocarbons, and differs from the process of example 2 in that: the specific reaction conditions for catalytic cracking in this comparative example were different from those in example 2.
The specific reaction conditions for this comparative example are shown in the following table.
Comparative example 5
This comparative example 5 uses the system of example 2 to perform catalytic cracking of light hydrocarbons, and differs from the process of example 2 in that: the specific reaction conditions for catalytic cracking in this comparative example were different from those in example 2.
The specific reaction conditions for this comparative example are shown in the following table.
The composition of the first catalyst in the above examples and comparative examples and the preparation method thereof include:
(1) Preparation of ZSM-5
First will be positiveEthyl silicate, sodium aluminate, tetrapropylammonium hydroxide, ammonia water and water according to 100SiO 2 :1Al 2 O 3 :20TPABr:120NH 3 ·H 2 O:2000H 2 Mixing the mol ratio of O, crystallizing for 12 hours at 80 ℃, crystallizing for 48 hours at 180 ℃ to obtain ZSM-5 with the grain size of 500-3000nm, washing, filtering, drying for 12 hours at 120 ℃, and roasting for 10 hours at 600 ℃ to obtain the molecular sieve raw material ZSM-5.
(2) Alkali treatment of catalyst supports
Mixing the molecular sieve raw material ZSM-5 with 0.4mol/L NaOH solution according to the mass ratio of 1:6, exchanging for 2 hours at 90 ℃, washing to be neutral, drying for 12 hours at 120 ℃ and roasting for 2 hours at 540 ℃.
Mixing a ZSM-5 molecular sieve with an ammonium nitrate solution with the mass ratio of 1:10, performing ammonium exchange at the temperature of 90 ℃ for 4 hours, washing to be neutral, drying at 120 ℃ for 12 hours, and roasting at 540 ℃ for 2 hours in sequence to obtain the catalyst carrier HZSM-5.
(3) Modification of nonmetallic elements
HZSM-5 treated with alkali and NH 4 H 2 PO 4 And (NH) 4 ) 2 SO 4 The mass ratio of the mixed solution of (2) is 0.5:1, and impregnating P and S on HZSM-5 to obtain the loading of P of 0.8wt% and the loading of S of 0.5wt%, and then ageing for 6h at room temperature, drying for 12h at 120 ℃ and roasting for 4h at 540 ℃.
(4) Hydrothermal treatment
The HZSM-5 modified by non-metallic element impregnation is subjected to hydro-thermal treatment for 4 hours at 550 ℃ in a water vapor atmosphere.
(5) Modification of metallic elements
(5.1) Nb impregnation
First (NH) 4 ) 3 [NbO(C 2 O 4 )]Heating to 60 ℃ to dissolve, then impregnating the HZSM-5 subjected to the hydrothermal treatment according to the mass ratio of 1:0.4 to obtain the Nb loading of 0.2wt%, aging for 6 hours at room temperature, drying for 12 hours at 120 ℃, and baking at 540 DEG C And (5) burning for 4 hours.
(5.2) impregnating Mn, mg and La
MnCl is added to 2 、MgCl 2 And La (NO) 3 ) 3 Adding the modified HZSM-5 into a 4mol/L citric acid solution, dipping Mn, mg and La on the HZSM-5 loaded with Nb according to the mass ratio of the citric acid to the HZSM-5 of 0.3:1 to obtain Mn loading of 1.8wt%, mg loading of 1.5wt% and La loading of 0.5wt%, then sequentially aging for 6 hours at room temperature, drying for 12 hours at 120 ℃ and roasting for 4 hours at 540 ℃ to obtain the modified HZSM-5.
(6) Preparation of an alkane-alkene co-cleavage catalyst
Mixing modified HZSM-5, a matrix (comprising kaolin, pseudo-boehmite and ZrO with the mass ratio of 7:3:1), silica sol, sesbania powder, methylcellulose and nitric acid according to the mass percentages of 40%, 30%, 15%, 4%, 10% and 1%, adding water to prepare slurry with the solid content of 35% by weight, spray-drying and forming to obtain catalyst microspheres with the particle size of 20-200nm, roasting at 600 ℃ for 4 hours, and performing hydrothermal aging treatment at 650 ℃ for 8 hours in a steam atmosphere to obtain the first catalyst.
The composition and preparation method of the second catalyst in the above embodiment include:
a second catalyst was prepared according to the same procedure as the first catalyst except that the second catalyst was prepared with different proportions of the components, modified HZSM-5, matrix (comprising kaolin, pseudo-boehmite and ZrO in a mass ratio of 7:3:1), silica sol, sesbania powder, methylcellulose and nitric acid, mixed in a mass fraction of 36%, 40%, 15%, 0.4%, 8% and 0.6%, respectively, and the rest of the procedure was the same as in example 1.
The composition and preparation method of the third catalyst in the above embodiment include:
1) Alkali treatment of ZSM-5 molecular sieve, mixing molecular sieve raw material ZSM-5 and 0.4mol/L NaOH solution according to a mass ratio of 1:6, exchanging for 2 hours at 90 ℃, washing to be neutral, drying for 12 hours at 120 ℃ and roasting for 2 hours at 540 ℃ in sequence;
2) Mixing the ZSM-5 molecular sieve obtained in the step 1) with an ammonium nitrate solution with the mass ratio of 1:10, performing ammonium exchange for 4 hours at the temperature of 90 ℃, washing to be neutral, drying at 120 ℃ for 12 hours, and roasting at 540 ℃ for 2 hours in sequence to obtain a catalyst carrier HZSM-5;
3) HZSM-5 and NH obtained according to step 3) 4 H 2 PO 4 And (NH) 4 ) 2 SO 4 The mass ratio of the mixed solution of (2) is 0.5:1, and impregnating P on HZSM-5 to obtain the loading of the P of 0.8wt%, and then ageing for 6 hours at room temperature, drying for 12 hours at 120 ℃ and roasting for 4 hours at 540 ℃.
4) The modified ZSM-5 molecular sieve, the Y molecular sieve, the matrix (the mass percentage of kaolin and pseudo-boehmite is 1:1) and the binder (the mass percentage of alumina sol and sesbania powder is 1:1) which are obtained in the step 3) are subjected to metal oxide (MnO and Fe) 2 O 3 The mass percentage is 1:1) according to the mass percentages of 30%, 10%, 20% and 20% respectively, mechanically stirring for 4 hours at 500r/min, ageing for 12 hours at room temperature, drying for 8 hours at 120 ℃, roasting for 4 hours at 600 ℃, and performing hydrothermal ageing treatment for 8 hours in a 650 ℃ water vapor atmosphere to obtain the third catalyst.
In the foregoing examples and comparative examples, the compositions of the first, second and third feedstocks are shown in Table 1, the specific reaction conditions for catalytic cracking are shown in tables 2 to 3, and the specific reaction results for catalytic cracking are shown in Table 4.
TABLE 1 composition of raw materials
Table 2 specific reaction conditions of examples
TABLE 3 specific reaction conditions for comparative examples
Table 4 reaction results of examples and comparative examples
As can be seen from table 4: 1. in the oil gas product obtained in the embodiment of the invention, the minimum propylene content and the maximum propylene content are respectively in the embodiment 5 (31.16%) and the embodiment 2 (34.54%), which are higher than those in the comparative example;
in addition, the ethylene content in the oil gas product obtained by the embodiment of the invention is higher than that in the comparative example;
2. in the oil gas product obtained by the embodiment of the invention, the dry gas and coke content is obviously lower than those of the comparative example, so that the method can reduce cracking and coking of raw materials, and is beneficial to improving propylene yield.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (6)

1. A method for multi-zone coupled bed controlled multi-stage catalytic cracking according to feedstock type, wherein the feedstock comprises a first feedstock having a C4 hydrocarbon mass content of greater than 40%, a second feedstock having a C5-C6 hydrocarbon mass content of greater than 40%, and a third feedstock having a C7-C8 hydrocarbon mass content of greater than 40%, using a reaction apparatus comprising a first downcomer, a second downcomer, and a riser, the method comprising the steps of:
enabling a first raw material to enter a first downlink pipe to contact with a catalyst to generate a first catalytic cracking reaction, so as to obtain a first catalytic cracking product and a first spent catalyst; enabling a second raw material to enter the second downlink pipe to perform a second catalytic cracking reaction to obtain a second catalytic cracking product and a second spent catalyst; a first catalytic cracking product and a first spent catalyst from the first downpipe, a second catalytic cracking product and a second spent catalyst from the second downpipe, and a third raw material enter the riser to perform a third catalytic cracking reaction; carrying out gas-solid separation on the product of the third catalytic cracking reaction to respectively obtain an oil gas product and a spent catalyst; the spent catalyst enters a regenerator to be regenerated after being subjected to steam stripping treatment, and then returns to participate in each catalytic cracking reaction;
The conditions of the first catalytic cracking reaction are as follows: the reaction temperature is 500-700 ℃, the catalyst-to-oil ratio is 5-40, the reaction pressure is 0.1-0.4MPa, and the residence time is 0.3-6s;
the conditions of the second catalytic cracking reaction are as follows: the reaction temperature is 480-680 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s;
the conditions of the third catalytic cracking reaction are as follows: the reaction temperature is 450-650 ℃, the catalyst-to-oil ratio is 3-30, the reaction pressure is 0.1-0.35MPa, and the residence time is 0.2-4s;
the raw materials of the catalyst comprise 20-50wt% of modified molecular sieve, 1-50wt% of matrix, 3-35wt% of binder and 3-15wt% of composite auxiliary agent, and the catalyst is obtained by hydrothermal aging treatment at 500-800 ℃; wherein, the liquid crystal display device comprises a liquid crystal display device,
the modified molecular sieve is obtained by alkali treatment of a molecular sieve raw material with the mass content of at least 80% of that of the ZSM-5 molecular sieve, non-metallic element modification and metallic element impregnation modification, and hydrothermal treatment is carried out between the two modification treatments; the nonmetallic elements are at least two selected from B, P, S, cl and Br; the metal element at least comprises a group IIA metal and a lanthanide series metal;
the compound auxiliary agent at least comprises inorganic acid and cellulose;
the temperature of the first catalytic cracking reaction is at least 50 ℃ higher than the reaction temperature of the second catalytic cracking reaction; the temperature of the second catalytic cracking reaction is at least 40 ℃ higher than the reaction temperature of the third catalytic cracking reaction;
The ratio of the catalyst to the oil of the first catalytic cracking reaction is at least 3 greater than the ratio of the catalyst to the oil of the second catalytic cracking reaction; the catalyst-to-oil ratio of the second catalytic cracking reaction is at least 3 greater than the catalyst-to-oil ratio of the third catalytic cracking reaction;
the residence time of the first catalytic cracking reaction is at least 0.2s greater than the residence time of the second catalytic cracking reaction; the residence time of the second catalytic cracking reaction is at least 0.2s greater than the residence time of the third catalytic cracking reaction.
2. The method of claim 1, wherein the reaction apparatus further comprises a fluidized bed reactor in series with the riser, the method further comprising:
the product of the third catalytic cracking reaction enters the fluidized bed reactor to generate a fourth catalytic cracking reaction, and the product of the fourth catalytic cracking reaction is subjected to gas-solid separation to respectively obtain the oil gas product and the spent catalyst;
the conditions of the fourth catalytic cracking reaction are as follows: space velocity of 2-25h -1 The linear speed of the bed layer is 0.1-0.5m/s, and the reaction temperature is 600-650 ℃.
3. The method of claim 1, further comprising preheating the first feedstock to 100-300 ℃ before entering the first downcomer; and/or the number of the groups of groups,
The second raw material is preheated to 100-250 ℃ before entering the second downgoing pipe; and/or the number of the groups of groups,
the third raw material is preheated to 100-250 ℃ before entering the riser.
4. The method according to claim 1, wherein the nonmetallic element includes at least S; and/or the number of the groups of groups,
the metal element is selected from more than three of Mn, V, fe, nb, cr, mo, W, mg, ca and La.
5. The method of claim 1, wherein the regeneration process comprises:
and inputting the to-be-regenerated catalyst into a heat compensator outside the regenerator through the regenerator for fluidization and pre-burning treatment, then entering the regenerator, and carrying out regeneration treatment under the action of regenerated gas to obtain the regenerated catalyst.
6. The method according to claim 5, wherein the temperature of the regeneration treatment is 600 ℃ to 850 ℃, the oxygen concentration in the regeneration gas is 10wt% to 35wt% and the linear velocity of the regeneration gas is 0.5m/s to 30m/s.
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