CN116693360A

CN116693360A - Method for preparing olefin by dehydrogenating low-carbon alkane

Info

Publication number: CN116693360A
Application number: CN202210191733.2A
Authority: CN
Inventors: 纪中海; 刘昌呈; 王春明
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2022-02-28
Filing date: 2022-02-28
Publication date: 2023-09-05

Abstract

The invention relates to a method for preparing olefin by dehydrogenating low-carbon alkane, which comprises the following steps of contacting low-carbon alkane with a dehydrogenation catalyst in a dehydrogenation reaction device under the conditions of hydrogen and no water to perform dehydrogenation reaction, and adjusting a controllable three-way valve to enable the dehydrogenation catalyst output by an upstream movable bed reactor to enter a catalyst regeneration unit for regeneration treatment through a catalyst regeneration pipeline without entering a downstream movable bed reactor when the carbon content of the dehydrogenation catalyst at the outlet of the upstream movable bed reactor falls within the range of 1-1.8 wt%. The dehydrogenation catalyst comprises an alumina support containing Sn and a rare earth metal and an active component. The method can improve the conversion rate of the raw materials for preparing the olefin from the low-carbon alkane, and improve the selectivity and the yield of the target product.

Description

Method for preparing olefin by dehydrogenating low-carbon alkane

Technical Field

The invention relates to a method for preparing olefin by dehydrogenating light alkane.

Background

Propylene is an important organic chemical basic raw material next to ethylene and is widely used for producing chemical products such as polypropylene, acrolein, acrylic acid, isopropanol, acrylonitrile, butanol and octanol. The traditional source of propylene mainly comes from byproducts of the catalytic cracking process of preparing ethylene and petroleum by steam cracking, and the yield of low-carbon alkane can be greatly increased along with the accelerated exploitation of unconventional oil gas such as global shale gas and the like. The lightening of ethylene cracking raw materials leads to the reduction of the amount of propylene as a byproduct, and simultaneously, the increase of oil demand is slowed down, and the propylene yield is limited due to the low-load operation of an FCC (fluid catalytic cracking) device of a refinery. With the increasing demand of propylene, the conventional propylene production process cannot meet the demand of propylene in the chemical industry, and other alternative process technologies must be developed rapidly, wherein the process of producing propylene by dehydrogenation of propane is the most interesting.

The existing catalytic dehydrogenation process of propane mainly comprises a Catofin process of Lummus company and an Oleflex process of UOP company, and adopts a fixed bed technology and a moving bed technology respectively. Wherein, the Oleflex process of UOP adopts Sn and alkali metal modified Pt/Al ₂ O ₃ The catalyst can be continuously regenerated, the reaction can be continuously carried out, and the application is wide.

US10336666 discloses a feed-wise improved moving bed dehydrogenation process. The streams in the process are not passing through the reactors in sequence, but may be fed at selective intervals. The maintenance of a certain reactor due to the abnormal pressure can be ensured, and the running time of the whole device is prolonged by adjusting the feeding mode.

US20190352240 and the same patent CN110177770 aim at solving the defect of low conversion rate of the moving bed dehydrogenation reactor, and the solution measures are to independently supply heat to each reactor and adjust the hydrogen-hydrocarbon ratio in the feed gas to 0.4 or lower, and each reactor is independently fed with steam to improve propylene yield, and the steam also has the function of inhibiting carbon deposition. The heater between the reactors adopts two parallel connection modes, and the side reaction in the heating process is restrained to reduce the propylene yield.

US20190232255 and the same family CN110352093 disclose a dehydrogenation catalyst. The mole ratio of platinum to promoter metal in the catalyst is 0.5-1.49, and when KOH is used for dripping, the acidity of the catalyst is 20-150 mu mol KOH/g, and the catalyst can reduce H ₂ And under the condition of alkane feeding proportion, the rapid carbon deposition is prevented, so that the reaction efficiency is improved.

U.S. Pat. No. 20190126249, U.S. Pat. No. 20190126251 and U.S. Pat. No. 3, 20190126256 disclose novel catalysts for the dehydrogenation of C2-C6 alkanes, U.S. Pat. No. 20190127297 shows the use of the above catalysts in a synergistic reduction of the reactor inlet temperature (500-645 ℃) and H ₂ Under the reaction condition of HC (0.01-0.4), the single pass yield is not reduced, and the carbon deposit quantity is combined with high reactor inlet temperature and high H ₂ The HC condition is equivalent.

Disclosure of Invention

The invention aims to provide a method for preparing olefin by dehydrogenating low-carbon alkane, which can improve the conversion rate of raw materials for preparing olefin by low-carbon alkane and the selectivity and yield of target products.

In order to achieve the above object, the present invention provides a method for preparing olefin by dehydrogenating light alkane, comprising: under the conditions of hydrogen and no water, the low-carbon alkane and a dehydrogenation catalyst are contacted in a dehydrogenation reaction device to carry out dehydrogenation reaction;

wherein the dehydrogenation reaction device at least comprises a plurality of moving bed reactors which are arranged in series, and the moving bed reactors at least comprise a first moving bed reactor and a second moving bed reactor; a first oil gas conveying pipeline and a first catalyst conveying pipeline are arranged between the first moving bed reactor and the second moving bed reactor; the first catalyst conveying pipeline is also provided with a first controllable three-way valve, and the first controllable three-way valve is connected with a first catalyst regeneration pipeline;

Detecting the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor in the operation process of the dehydrogenation reaction device, and adjusting the first controllable three-way valve to enable the dehydrogenation catalyst output by the first moving bed reactor to enter a catalyst regeneration unit through the first catalyst regeneration pipeline for regeneration treatment without entering the second moving bed reactor when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor falls within the range of 1-1.8 wt%;

the dehydrogenation catalyst comprises an alumina carrier containing Sn and rare earth metals and an active component, wherein the active component comprises 0.1-5.0 wt% of group VIII metal, 0.1-3.0 wt% of alkali metal, 0.3-5.0 wt% of halogen and 0.1-3.0 wt% of Sn and 0.01-5.0 wt% of rare earth metals based on the dry weight of the alumina carrier.

Optionally, when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor falls within the range of 1.2-1.6 wt%, adjusting the first controllable three-way valve so that the dehydrogenation catalyst output by the first moving bed reactor enters a catalyst regeneration unit through the first catalyst regeneration pipeline to be subjected to regeneration treatment without entering the second moving bed reactor;

More preferably, when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor falls within the range of 1.3 to 1.5 wt%, the first controllable three-way valve is adjusted so that the dehydrogenation catalyst outputted from the first moving bed reactor enters a catalyst regeneration unit through the first catalyst regeneration pipe to be subjected to regeneration treatment without entering the second moving bed reactor.

Optionally, the conditions under which the dehydrogenation reaction is carried out include: the inlet temperature of the dehydrogenation reaction device is 550-655 ℃, the pressure is 0.01-1.0MPa, the molar ratio of hydrogen to the lower alkane is 0.001-0.45, and the mass airspeed of the lower alkane is 0.1-20h ^-1 Preferably, the molar ratio of the hydrogen to the lower alkane is 0.01-0.3.

Optionally, the dehydrogenation reaction unit further comprises a third moving bed reactor connected downstream of the second moving bed reactor;

a second oil gas conveying pipeline and a second catalyst conveying pipeline are arranged between the second moving bed reactor and the third moving bed reactor; the second catalyst conveying pipeline is also provided with a second controllable three-way valve, and the second controllable three-way valve is connected with a second catalyst regeneration pipeline;

Detecting the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor in the operation process of the dehydrogenation reaction device, and adjusting the second controllable three-way valve to enable the dehydrogenation catalyst output by the second moving bed reactor to enter a catalyst regeneration unit through the second catalyst regeneration pipeline for regeneration treatment without entering the third moving bed reactor when the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor falls within the range of 1-1.8 wt%;

preferably, the dehydrogenation reaction unit further comprises a fourth moving bed reactor connected downstream of the third moving bed reactor;

a third oil gas conveying pipeline and a third catalyst conveying pipeline are arranged between the third moving bed reactor and the fourth moving bed reactor; the third catalyst conveying pipeline is also provided with a third controllable three-way valve, and the third controllable three-way valve is connected with a third catalyst regeneration pipeline;

detecting the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor in the operation process of the dehydrogenation reaction device, and adjusting the third controllable three-way valve to enable the dehydrogenation catalyst output by the third moving bed reactor to enter a catalyst regeneration unit through the third catalyst regeneration pipeline for regeneration treatment without entering the fourth moving bed reactor when the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor falls within the range of 1-1.8 wt%;

Optionally, the catalyst regeneration unit comprises a scorching zone, a chlorine-oxygen activation zone, and a drying zone;

the conditions in the scorch zone include: the temperature is 420-600 ℃, and the oxygen content is 0.1-8.0mol%;

the conditions in the chlorine-oxygen activation zone include: the temperature is 480-610 ℃, the oxygen content is 0.1-25mol%, and the chlorine injection amount is 0.1-3% of the catalyst circulation rate;

the conditions in the drying zone include: the temperature is 400-550 ℃, and the oxygen content is 0.1-25mol%.

Optionally, the active component comprises 0.1 to 5.0 wt% of a group viii metal, 0.1 to 3.0 wt% of an alkali metal, 0.3 to 5.0 wt% of a halogen, based on the dry weight of the alumina carrier, 0.1 to 3.0 wt% of Sn, and 0.1 to 2.5 wt% of a rare earth metal.

Optionally, the alumina carrier contains theta-alumina, and the specific surface area of the alumina carrier is 50-140m ² Per gram, pore volume of 0.4-0.75mL/g, average particle diameter of 1.6-2.5mm, and apparent bulk density of 0.7-0.45g/cm ³ ；

The group VIII metal is selected from one or more of platinum, palladium, gold and iridium, preferably platinum;

the rare earth metal is selected from one or more of La, ce, pr, eu, sm and Tm, preferably one or more of La, ce, eu and Sm, more preferably Ce and Eu;

The alkali metal is selected from one or more of potassium, lithium, sodium and cesium, preferably potassium;

the halogen is selected from one or more of chlorine, bromine and fluorine, preferably chlorine.

Optionally, the dehydrogenation catalyst is prepared by a method comprising the following steps:

(1) Mixing alumina sol, a tin source, a rare earth metal source and a pore-enlarging agent, and then performing forming treatment to obtain a first solid product;

(2) Performing first roasting on the first solid product to obtain a second solid product;

(3) Contacting the second solid product with a first impregnating solution to carry out first impregnation, and carrying out second roasting on the solid after the first impregnation to obtain a third solid product; wherein the first impregnating solution contains a compound containing a group VIII metal and halogen;

(4) And contacting the third solid product with a second impregnating solution to carry out second impregnation, and optionally drying, third roasting and reducing the solid after the second impregnation, wherein the second impregnating solution contains an alkali metal source.

Optionally, the tin source is selected from one or more of stannous bromide, stannous chloride, stannic chloride pentahydrate and tetrabutyltin;

The rare earth metal source is selected from one or more of europium chloride, cerium chloride, samarium nitrate, cerium nitrate and lanthanum nitrate;

the pore-expanding agent is one or more selected from C10-C16 hydrocarbon, urea and ammonium carbonate salt;

the compound containing the group VIII metal and halogen is selected from one or more of chloroplatinic acid, ammonium chloroplatinate and platinum chloride;

the alkali metal source is one or more of potassium nitrate, potassium hydroxide and potassium chloride.

Optionally, the lower alkane is at least one of propane, butane and isobutane.

According to the technical scheme, the catalyst with the specific composition is adopted, the carbon content on the catalyst is controlled in the specific range, and the dehydrogenation reaction of the low-carbon alkane is carried out under the condition, so that the conversion rate of raw materials, the selectivity and the yield of target products can be improved, and the amount of chlorine used for regeneration and the abrasion of the catalyst are reduced.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:

Fig. 1 is a schematic structural view of an embodiment of the present invention.

Description of the reference numerals

1. First moving bed reactor 2, second moving bed reactor 3, third moving bed reactor

4. Fourth moving bed reactor 5, catalyst regeneration unit 6, compressor

7. Hydrogen 8, dryer 9, expander

10. Low carbon alkane

Detailed Description

The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

The invention provides a method for preparing olefin by dehydrogenating light alkane, which comprises the following steps: under the conditions of hydrogen and no water, the low-carbon alkane and a dehydrogenation catalyst are contacted in a dehydrogenation reaction device to carry out dehydrogenation reaction;

wherein the dehydrogenation reaction device at least comprises a plurality of moving bed reactors which are arranged in series, and the moving bed reactors at least comprise a first moving bed reactor 1 and a second moving bed reactor 2; a first oil gas conveying pipeline and a first catalyst conveying pipeline are arranged between the first moving bed reactor 1 and the second moving bed reactor 2; the first catalyst conveying pipeline is also provided with a first controllable three-way valve, and the first controllable three-way valve is connected with a first catalyst regeneration pipeline;

During the operation of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor 1, and when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor 1 falls within the range of 1-1.8 wt%, adjusting the first controllable three-way valve to enable the dehydrogenation catalyst output by the first moving bed reactor 1 to enter a catalyst regeneration unit 5 through the first catalyst regeneration pipeline for regeneration treatment without entering the second moving bed reactor 2;

In the present invention, the dry basis weight of the alumina carrier means the dry basis weight of the alumina carrier from which Sn and rare earth metal are removed by planing from the alumina carrier containing Sn and rare earth metal. The method adopts the catalyst with specific composition, controls the carbon content on the catalyst in a specific range, and under the condition, the dehydrogenation reaction of the low-carbon alkane is carried out, so that the conversion rate of raw materials, the selectivity and the yield of target products can be improved, the amount of chlorine used for regeneration is reduced, and the abrasion of the catalyst is reduced.

In one embodiment of the present invention, when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor 1 falls within the range of 1.2-1.6 wt%, the first controllable three-way valve is adjusted so that the dehydrogenation catalyst output from the first moving bed reactor 1 enters a catalyst regeneration unit through the first catalyst regeneration pipe for regeneration treatment without entering the second moving bed reactor;

more preferably, when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor 1 falls within the range of 1.3 to 1.5 wt%, the first controllable three-way valve is adjusted so that the dehydrogenation catalyst outputted from the first moving bed reactor enters the catalyst regeneration unit 5 through the first catalyst regeneration pipe to be subjected to a regeneration treatment without entering the second moving bed reactor 2.

In one embodiment of the present invention, the conditions under which the dehydrogenation reaction is carried out include: the dehydrogenation reaction unit has an inlet temperature of 550-655 deg.C and a pressure of 0.01-1.0MPa, the molar ratio of hydrogen to the lower alkane may vary widely, for example, may be 0.001-0.45, preferably 0.01-0.3, the mass space velocity of the lower alkane may also vary widely, preferably 0.1-20h ^-1 Preferably 0.5-10h ^-1 。

In one embodiment of the present invention, argon, methane, ethane, nitrogen, etc. may be optionally used as the diluent material for the dehydrogenation reaction, and the diluent material is preferably hydrogen.

In one embodiment of the present invention, as shown in FIG. 1, the dehydrogenation reaction unit further comprises a third moving bed reactor 3 connected downstream of the second moving bed reactor 2; a second oil gas conveying pipeline and a second catalyst conveying pipeline are arranged between the second moving bed reactor 2 and the third moving bed reactor 3; the second catalyst conveying pipeline is also provided with a second controllable three-way valve, and the second controllable three-way valve is connected with a second catalyst regeneration pipeline; and in the operation process of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor 2, and when the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor 2 falls within the range of 1-1.8 weight percent, adjusting the second controllable three-way valve to enable the dehydrogenation catalyst output by the second moving bed reactor 2 to enter a catalyst regeneration unit 5 through a second catalyst regeneration pipeline for regeneration treatment without entering the third moving bed reactor 3.

In another embodiment of the present invention, the dehydrogenation reaction unit further comprises a fourth moving bed reactor 4 connected downstream of the third moving bed reactor 3; a third oil gas conveying pipeline and a third catalyst conveying pipeline are arranged between the third moving bed reactor and the fourth moving bed 4 reactor; the third catalyst conveying pipeline is also provided with a third controllable three-way valve, and the third controllable three-way valve is connected with a third catalyst regeneration pipeline; and in the operation process of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor 3, and when the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor 3 falls within the range of 1-1.8 weight percent, adjusting the third controllable three-way valve to enable the dehydrogenation catalyst output by the third moving bed reactor 3 to enter a catalyst regeneration unit 5 through a third catalyst regeneration pipeline for regeneration treatment without entering the fourth moving bed reactor 4.

In one embodiment of the invention, the effluent from the fourth moving bed reactor 4 is compressed by a compressor 6 and then sent to a dryer 8 for drying, and the dried product is separated to obtain an olefin product. Preferably, the separated hydrogen is led out through an expander 9, and is mixed with the raw material low-carbon alkane 10 as hydrogen 7, and then is led into the first moving bed reactor 1.

In one embodiment of the present invention, the catalyst regeneration unit 5 includes a char zone, a chlorine-oxygen activation zone, and a drying zone; the conditions in the scorch zone include: the temperature is 420-600 ℃, and the oxygen content is 0.1-8.0mol%; the conditions in the chlorine-oxygen activation zone include: the temperature is 480-610 ℃, the oxygen content is 0.1-25mol%, and the chlorine injection amount is 0.1-3% of the catalyst circulation rate; the conditions in the drying zone include: the temperature is 400-550 ℃, and the oxygen content is 0.1-25mol%.

In one embodiment of the invention, the active component comprises 0.1 to 5.0 wt.% group viii metal, 0.1 to 3.0 wt.% alkali metal, 0.3 to 5.0 wt.% halogen, 0.1 to 3.0 wt.% Sn, and 0.1 to 2.5 wt.% rare earth metal, based on the dry weight of the alumina support.

In one embodiment of the invention, the alumina carrier contains theta-alumina, and the specific surface area of the alumina carrier is 50-140m ² Per gram, pore volume of 0.4-0.75mL/g, average particle diameter of 1.6-2.5mm, and apparent bulk density of 0.7-0.45g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the Preferably, the specific surface area is 80-130m ² Per gram, pore volume of 0.50-0.72mL/g, average particle diameter of 1.6-2.0mm, and apparent bulk density of 0.7-0.55g/cm ³ . In the invention, the specific surface area and the pore volume are detected by a BET method, the average particle diameter is detected by a particle size analyzer, and the apparent bulk density is detected by a method of placing catalyst particles in a measuring cylinder and beating until the volume is unchanged.

According to the present invention, the source of theta alumina is not limited and may be commercially available or self-prepared, and in one embodiment, the theta alumina is prepared by a process comprising the steps of: roasting alumina pellets at 450-650 ℃ to prepare gamma-Al ₂ O ₃ And thenRoasting at 900-1100 deg.c for 1-20 hr. Preferably, gamma-Al is used ₂ O ₃ Treating with air with water content of 2-10 vol.% at 450-650deg.C for 2-8 hr, and calcining at 900-1100deg.C.

The source of the alumina pellets is not particularly limited, and can be prepared by a method conventionally adopted by those skilled in the art. In one embodiment, aluminum trichloride and ammonia water are reacted at 50-90 ℃, preferably 50-80 ℃, and then filtered and washed, an acid solution is added into a filter cake to form aluminum sol, or water is directly added into aluminum hydroxide powder to prepare slurry, and then acid is added into the slurry to prepare aluminum sol; the aluminum sol is formed by using oil ammonia column or hot oil column to drop balls, and the acid used for preparing the aluminum sol is preferably nitric acid or hydrochloric acid, wherein organic acid such as acetic acid or citric acid can be added. If alumina containing macropores is prepared, a proper amount of pore-enlarging agents such as urea, kerosene, fatty alcohol polyoxyethylene ether and the like are added into the alumina sol. And drying wet spheres obtained by the drop sphere molding to obtain the alumina spheres.

In one embodiment of the present invention, the group viii metal is selected from one or more of platinum, palladium, gold and iridium, preferably platinum; the rare earth metal is selected from one or more of La, ce, pr, eu, sm and Tm, preferably one or more of La, ce, eu and Sm, more preferably Ce and Eu; the alkali metal is selected from one or more of potassium, lithium, sodium and cesium, preferably potassium; the halogen is selected from one or more of chlorine, bromine and fluorine, preferably chlorine.

In one embodiment of the present invention, the dehydrogenation catalyst is prepared by a process comprising the steps of: (1) Mixing alumina sol, a tin source, a rare earth metal source and a pore-enlarging agent, and then performing forming treatment to obtain a first solid product; (2) Performing first roasting on the first solid product to obtain a second solid product; (3) Contacting the second solid product with a first impregnating solution to carry out first impregnation, and carrying out second roasting on the solid after the first impregnation to obtain a third solid product; wherein the first impregnating solution contains a compound containing a group VIII metal and halogen; (4) And contacting the third solid product with a second impregnating solution to carry out second impregnation, and optionally drying, third roasting and reducing the solid after the second impregnation, wherein the second impregnating solution contains an alkali metal source.

The tin and the rare earth metal in the dehydrogenation catalyst are introduced in the gelling process of the alumina, the rare earth metal element with nanometer size and tin have tighter combination degree, the damage to the active center of VIII metal-Sn when a larger rare earth element compound and tin are separated is avoided, the stabilization of the active center is enhanced, the coke rate is reduced, and the selectivity and the stability of the catalyst are improved. The dehydrogenation catalyst prepared by the method is used in the low-carbon alkane dehydrogenation reaction, so that the conversion rate of the low-carbon alkane and the yield of the alkene can be further improved.

In step (1) according to the present invention, the molding treatment may be performed by a method conventionally employed by those skilled in the art, and may be, for example, oil ammonia column or hot oil column drop ball molding. Drop ball molding is well known to those skilled in the art and the present invention is not described in detail herein.

In one embodiment of the invention, in step (3), the impregnation liquid/solid ratio may be in the range of 0.5 to 3.0mL/g, preferably 1.0 to 2.5mL/g. Step (3) may further include: drying the solid after the first impregnation, and then performing the second roasting, wherein the drying temperature is 100-300 ℃, the drying time is not particularly limited, and the drying time can be selected according to actual needs.

In one embodiment of the present invention, the tin source may be a chloride, bromide, nitrate, alkoxide or organic complex of tin, preferably, the tin source may include, but is not limited to, one or more of stannous bromide, stannous chloride, stannic chloride pentahydrate and tetrabutyltin, the rare earth metal source is selected from a chloride of rare earth metal and/or nitrate of rare earth metal, preferably, one or more of europium chloride, cerium chloride, samarium nitrate, cerium nitrate and lanthanum nitrate, and the pore expanding agent is selected from one or more of hydrocarbon of C10-C16, urea and ammonium carbonate salt; the compound containing the group VIII metal and halogen is selected from one or more of chloroplatinic acid, ammonium chloroplatinate and platinum chloride; the alkali metal source is selected from alkali metal hydroxide, alkali metal nitrate or alkali metal chloride, preferably, the alkali metal source can include one or more of potassium nitrate, potassium hydroxide, potassium chloride and potassium chloride.

In a specific embodiment of the present invention, in the step (2), the first baking includes a first-stage baking and a second-stage baking that are sequentially performed; the conditions of the one-stage roasting include: the temperature is 620-680 ℃ and the time is 1-8 hours; the conditions of the two-stage roasting include: the temperature is 900-1100 ℃ and the time is 1-8 hours.

In one embodiment of the present invention, the conditions of the second firing and the third firing each independently include: the temperature is 400-650 ℃ and the time is 1-10 hours; preferably, the temperature is 480-620 ℃ and the time is 2-6 hours. The conditions of the first impregnation and the second impregnation each independently include: the temperature is 15-40 ℃ and the time is 1-10 hours; preferably, the temperature is 20-30℃for 2-6 hours. Calcination may be carried out in equipment conventionally employed by those skilled in the art, for example in a muffle furnace or a tube furnace. The firing atmosphere is not particularly limited in the present invention, and may be, for example, an air atmosphere or an inert atmosphere.

In one embodiment of the present invention, in the step (4), the conditions of the reduction treatment include: the temperature is 450-700 ℃, more preferably 500-650 ℃ and the time is 0.5-20 hours, more preferably 2-10 hours. The reduction may be carried out before the catalyst is charged into the reactor or after the catalyst is charged into the reactor and before the dehydrogenation reaction. The gas used for the reduction treatment is hydrogen or other reducing gases, and a mixture of hydrogen and inert gas can be used.

In one embodiment of the present invention, step (4) includes: the third calcined product is subjected to an oxychlorination treatment followed by a reduction treatment, which is well known to those skilled in the art, and may be performed under conditions containing water, a chlorine-containing gas compound and oxygen. The group VIII metal is substantially dispersed in the support by the oxychlorination and reduction treatments and reduced to the corresponding metallic state.

The invention is further illustrated by the following examples, which are not intended to be limiting in any way. The raw materials used in the following examples and comparative examples are all commercially available unless otherwise specified.

Preparation examples 1-2 and preparation comparative examples 1-2 are preparation examples of hydrogenation catalysts.

Preparation example 1

(1) 27g of aluminum flakes were taken and 610 g of 18 wt% hydrochloric acid solution was added to dissolve the aluminum flakes to obtain a solution having an aluminum trichloride content of 4 wt%. Transferring the aluminum trichloride solution into a neutralization tank, adding 850 g of ammonia water with the concentration of 6 wt%, and uniformly mixing at 60 ℃ with the pH value of 7.5-8.5. The generated aluminum hydroxide is filtered and washed, and 9mL of the aluminum hydroxide with volume ratio of 1 is added into a filter cake: 1 to obtain alumina sol.

To the alumina sol, 40mL of a solution containing 30 g of urea and a hydrochloric acid solution containing stannous chloride, europium chloride and cerium chloride were added with stirring so that the Sn content in the solution was 0.30% by mass of dry alumina, the Eu content was 0.20% by mass of dry alumina and the Ce content was 0.05% by mass of dry alumina, and the mixture was stirred for 1 hour for acidification.

Then 30 g of kerosene and 3 g of fatty alcohol-polyoxyethylene ether were added dropwise to the acidified sol with stirring. The sol is dripped into an oil-ammonia column with an upper layer being an oil phase and a lower layer being an ammonia water phase to form the gel. The oil phase is kerosene, the concentration of ammonia water in the ammonia water phase is 8 wt%, and wet balls (namely a first solid product) are obtained;

(2) Solidifying the first solid product in ammonia water phase for 1 hr, taking out, washing with deionized water, drying at 60 deg.C for 6 hr, drying at 120 deg.C for 10 hr, first roasting at 650 deg.C in air flow for 4 hr, then treating at 650 deg.C in air with water vapor content of 5 vol% for 10 hr, heating to 1000 deg.C, and second roasting for 4 hr to obtain spherical theta-Al containing Sn, eu and Ce ₂ O ₃ A support (i.e., the second solid product) having a specific surface area of 120m ² Per gram, a pore volume of 0.45mL/g, and an apparent bulk density of 0.59g/cm ³ The average particle diameter is 1.6mm;

(3) The second solid product was impregnated with an impregnation solution containing chloroplatinic acid and hydrochloric acid at 25℃for 4 hours, the impregnation solution containing 0.30% by weight of platinum and 1.4% by weight of HCl (both relative to the mass of alumina on a dry basis, the same applies hereinafter), the liquid/solid ratio being 2.0mL/g. Drying the impregnated solid at 120 ℃ for 12 hours, and roasting at 500 ℃ for 4 hours to obtain a third solid product;

(4) The third solid product was immersed in a potassium nitrate solution at 25℃for 4 hours, and the immersed solution contained 1.2% by weight of potassium (relative to the mass of the dry alumina) and the liquid/solid ratio was 2.1mL/g. The impregnated solid was dried at 120℃for 12 hours, calcined at 600℃for 4 hours, and reduced with hydrogen at 550℃for 4 hours to give dehydrogenation catalyst A.

The dehydrogenation catalyst A had a platinum content of 0.30 wt%, a tin content of 0.30 wt%, a europium content of 0.20 wt%, a cerium content of 0.05 wt%, a potassium content of 1.2 wt% and a chlorine content of 1.1 wt% (all relative to dry alumina, the same applies hereinafter).

Preparation example 2

A dehydrogenation catalyst B was prepared in the same manner as in example 1 except that in step (1), 40mL of a solution containing 30 g of urea and a hydrochloric acid solution containing stannous chloride and cerium chloride were added to the alumina sol with stirring so that the Sn content in the solution was 0.30 mass% of the dry alumina and the Ce content was 0.3 mass% of the dry alumina, and the mixture was acidified with stirring for 1 hour. Preparing and obtaining the theta-Al containing tin and cerium ₂ O ₃ The specific surface area of the carrier is 118m ² Per gram, a pore volume of 0.361mL/g, and an apparent bulk density of 0.60g/cm ³ The average particle diameter was 1.6mm.

The dehydrogenation catalyst B obtained was free of europium, and had a platinum content of 0.30 wt%, a tin content of 0.30 wt%, a cerium content of 0.30 wt%, a potassium content of 1.2 wt% and a chlorine content of 1.1 wt%.

Preparation of comparative example 1

A dehydrogenation catalyst DA was prepared in the same manner as in example 1 except that in step (1), 40mL of a 30-gram urea-containing solution and a 30-gram sub-chloride-containing solution were added to the alumina sol with stirring A hydrochloric acid solution of tin, wherein the Sn content in the solution is 0.3 mass% of dry alumina, and the solution is stirred for 1 hour for acidification; preparing the theta-Al containing tin ₂ O ₃ The specific surface area of the carrier is 119m ² Per gram, a pore volume of 0.359mL/g, and an apparent bulk density of 0.60g/cm ³ The average particle diameter was 1.6mm. In step (3), the second solid product was impregnated with an impregnating solution containing chloroplatinic acid, cerium chloride, and hydrochloric acid at 25 ℃ for 4 hours.

The dehydrogenation catalyst DA thus obtained did not contain europium, and had a platinum content of 0.30 wt.%, a tin content of 0.3 wt.%, a cerium content of 0.30 wt.%, a potassium content of 1.2 wt.%, and a chlorine content of 1.1 wt.%.

Preparation of comparative example 2

A dehydrogenation catalyst DB was prepared in the same manner as in example 1 except that in step (1), 40mL of a solution containing 30 g of urea and a hydrochloric acid solution containing stannous chloride were added to the alumina sol with stirring so that the Sn content in the solution was 0.30 mass% of that of the dry alumina, and stirred for 1 hour for acidification.

The dehydrogenation catalyst DB obtained was free of europium and cerium, and had a platinum content of 0.30 wt%, a tin content of 0.30 wt%, a potassium content of 1.2 wt% and a chlorine content of 1.1 wt%.

Example 1

Carrying out low-carbon alkane dehydrogenation to prepare olefin in a system shown in fig. 1, wherein a dehydrogenation reaction device comprises a first moving bed reactor 1, a second moving bed reactor 2, a third moving bed reactor 3 and a fourth moving bed reactor 4 which are arranged in series along the flow direction of raw materials; a first oil gas conveying pipeline and a first catalyst conveying pipeline are arranged between the first moving bed reactor 1 and the second moving bed reactor 2; the first catalyst conveying pipeline is also provided with a first controllable three-way valve, and the first controllable three-way valve is connected with a first catalyst regeneration pipeline; a second oil gas conveying pipeline and a second catalyst conveying pipeline are arranged between the second moving bed reactor and the third moving bed reactor; the second catalyst conveying pipeline is also provided with a second controllable three-way valve, and the second controllable three-way valve is connected with a second catalyst regeneration pipeline; a third oil gas conveying pipeline and a third catalyst conveying pipeline are arranged between the third moving bed reactor and the fourth moving bed reactor; the third catalyst conveying pipeline is also provided with a third controllable three-way valve, and the third controllable three-way valve is connected with a third catalyst regeneration pipeline.

20g of dehydrogenation catalyst A was charged in the first moving bed reactor, 22g of dehydrogenation catalyst A was charged in the second moving bed reactor, 26g of dehydrogenation catalyst A was charged in the third moving bed reactor, and 30g of dehydrogenation catalyst A was charged in the fourth moving bed reactor. The mixed gas of hydrogen and low-carbon alkane is taken as raw material and is introduced into a first moving bed reactor, wherein the inlet temperature of the first moving bed reactor is 615 ℃, the pressure is 0.21MPa (absolute pressure), and the feeding mass space velocity of the low-carbon alkane is 9.0h ^-1 The molar ratio of hydrogen to lower alkane is 0.3:1, a step of; the reaction was carried out for 20 hours under the above conditions, the product flowing out of the fourth fluidized bed reactor was sampled once every 1 hour, the conversion of light alkane and the selectivity of olefin were calculated, and the carbon content of the dehydrogenation catalyst at the outlet of the four fluidized bed reactors was detected, respectively, and when the carbon content of the dehydrogenation catalyst at the outlet of any moving bed reactor (first, second or third moving bed reactor) was in the range of 1.3 to 1.6% by weight, the three-way valve controlled on the catalyst transport pipe communicating with the catalyst outlet of the moving bed reactor was adjusted so that the dehydrogenation catalyst of carbon deposit outputted from the moving bed reactor was fed into the catalyst regeneration unit 5 through the catalyst regeneration pipe communicating with the catalyst outlet thereof to conduct the regeneration treatment without feeding into the downstream moving bed reactor, and the carbon deposit content of the catalyst at the outlet of the catalyst regeneration unit 5 was measured after the completion of the reaction, and the results are shown in table 1.

Example 2

The same procedure as in example 1 was followed except that the dehydrogenation catalyst B prepared in preparation example 2 was used instead of the dehydrogenation catalyst A, respectively.

Example 3

The dehydrogenation of light alkane was carried out in the same manner as in example 1 except that the inlet temperature in the first moving bed reactor was 615℃and 0.21MPa (absolute pressure) The feeding mass space velocity of the low-carbon alkane is 9.0h ^-1 The molar ratio of hydrogen to lower alkane was 0.35:1.

comparative example 1

The dehydrogenation of light alkane was performed in the same manner as in example 1 except that the dehydrogenation catalyst DB prepared in preparation comparative example 2 was used instead of the dehydrogenation catalyst a.

Comparative example 2

The dehydrogenation of light alkane was carried out in the same manner as in example 1 except that the dehydrogenation catalyst DA prepared in comparative example 1 was used instead of the dehydrogenation catalyst A. The inlet temperature of the first moving bed reactor is 615 ℃, the absolute pressure is 0.21MPa, and the feeding mass space velocity of the low-carbon alkane is 9.0h ^-1 The molar ratio of hydrogen to lower alkane is 0.3:1.

TABLE 1

The conversion in Table 1 is the conversion of the lower alkane as the starting material, and the selectivity and yield are the selectivity and yield of the desired product olefin. As is clear from a comparison of the results of example 2 and comparative example 1, example 2 uses the specific dehydrogenation catalyst of the present application, in which the carrier contains a rare earth metal, and a higher selectivity can be achieved at the initial stage of the reaction. As is evident from a comparison of examples 1 and 2, the active component in the dehydrogenation catalyst preferably comprises, based on the dry weight of the alumina support, from 0.1 to 5.0% by weight of a group VIII metal, from 0.1 to 3.0% by weight of an alkali metal, from 0.3 to 5.0% by weight of a halogen, based on the dry weight of the alumina support, from 0.1 to 3.0% by weight of Sn and from 0.1 to 2.5% by weight of a rare earth metal, the process of the present application provides better conversion of the starting material, selectivity to the desired product and yield, and less carbon deposition. As is clear from comparison of comparative example 2 and example 2, the subsequent impregnation method introduces rare earth metal into the dehydrogenation catalyst, i.e., the alumina carrier of the dehydrogenation catalyst does not contain rare earth metal, has little effect on improving the conversion rate and stability of the dehydrogenation catalyst and inhibiting carbon deposition. From the above, the method of the application can improve the conversion rate of the raw materials for preparing olefin from low-carbon alkane, improve the selectivity and yield of target products, and maintain lower carbon deposit of the catalyst.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein. Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims

1. A method for preparing olefin by dehydrogenating light alkane, comprising the following steps: under the conditions of hydrogen and no water, the low-carbon alkane and a dehydrogenation catalyst are contacted in a dehydrogenation reaction device to carry out dehydrogenation reaction;

Wherein the dehydrogenation reaction device at least comprises a plurality of moving bed reactors which are arranged in series, and the moving bed reactors at least comprise a first moving bed reactor (1) and a second moving bed reactor (2); a first oil gas conveying pipeline and a first catalyst conveying pipeline are arranged between the first moving bed reactor (1) and the second moving bed reactor (2); the first catalyst conveying pipeline is also provided with a first controllable three-way valve, and the first controllable three-way valve is connected with a first catalyst regeneration pipeline;

during the operation of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor (1), and when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor (1) falls within the range of 1-1.8 wt%, adjusting the first controllable three-way valve to enable the dehydrogenation catalyst output by the first moving bed reactor to enter a catalyst regeneration unit (5) through the first catalyst regeneration pipeline for regeneration treatment without entering the second moving bed reactor (2);

2. The method according to claim 1, wherein when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor (1) falls within the range of 1.2-1.6 wt%, the first controllable three-way valve is adjusted so that the dehydrogenation catalyst output by the first moving bed reactor (1) enters a catalyst regeneration unit (5) through the first catalyst regeneration pipe for regeneration treatment without entering the second moving bed reactor;

more preferably, when the carbon content of the dehydrogenation catalyst at the outlet of the first moving bed reactor (1) falls within the range of 1.3 to 1.5 wt%, the first controllable three-way valve is adjusted so that the dehydrogenation catalyst outputted from the first moving bed reactor (1) enters a catalyst regeneration unit (5) through the first catalyst regeneration pipe for regeneration treatment without entering the second moving bed reactor (2).

3. The method of claim 1, wherein the conditions under which the dehydrogenation reaction is performed comprise: the inlet temperature of the dehydrogenation reaction device is 550-655 ℃, the pressure is 0.01-1.0MPa, the molar ratio of hydrogen to the lower alkane is 0.001-0.45, and the mass airspeed of the lower alkane is0.1-20h ^-1 Preferably, the molar ratio of the hydrogen to the lower alkane is 0.01-0.3.

4. The method according to claim 1, wherein the dehydrogenation reaction unit further comprises a third moving bed reactor (3) connected downstream of the second moving bed reactor (2);

a second oil gas conveying pipeline and a second catalyst conveying pipeline are arranged between the second moving bed reactor (2) and the third moving bed reactor (3); the second catalyst conveying pipeline is also provided with a second controllable three-way valve, and the second controllable three-way valve is connected with a second catalyst regeneration pipeline;

during the operation of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor (2), and when the carbon content of the dehydrogenation catalyst at the outlet of the second moving bed reactor (2) falls within the range of 1-1.8 wt%, adjusting the second controllable three-way valve to enable the dehydrogenation catalyst output by the second moving bed reactor (2) to enter a catalyst regeneration unit (5) through a second catalyst regeneration pipeline for regeneration treatment without entering the third moving bed reactor (3);

preferably, the dehydrogenation reaction unit further comprises a fourth moving bed reactor (4) connected downstream of the third moving bed reactor;

A third oil gas conveying pipeline and a third catalyst conveying pipeline are arranged between the third moving bed reactor (3) and the fourth moving bed reactor (4); the third catalyst conveying pipeline is also provided with a third controllable three-way valve, and the third controllable three-way valve is connected with a third catalyst regeneration pipeline;

and in the operation process of the dehydrogenation reaction device, detecting the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor (3), and when the carbon content of the dehydrogenation catalyst at the outlet of the third moving bed reactor (3) falls within the range of 1-1.8 weight percent, adjusting the third controllable three-way valve to enable the dehydrogenation catalyst output by the third moving bed reactor (3) to enter a catalyst regeneration unit (5) through a third catalyst regeneration pipeline for regeneration treatment without entering the fourth moving bed reactor (4).

5. The process of claim 1, wherein the catalyst regeneration unit comprises a char zone, a chlorine-oxygen activation zone, and a drying zone;

6. The method of claim 1, wherein the active component comprises 0.1-5.0 wt.% group viii metal, 0.1-3.0 wt.% alkali metal, 0.3-5.0 wt.% halogen, based on the dry weight of the alumina support, 0.1-3.0 wt.% Sn, and 0.1-2.5 wt.% rare earth metal, based on the dry weight of the alumina support.

7. The method according to claim 1, wherein the alumina carrier contains theta-alumina, and the specific surface area of the alumina carrier is 50-140m ² Per gram, pore volume of 0.4-0.75mL/g, average particle diameter of 1.6-2.5mm, and apparent bulk density of 0.7-0.45g/cm ³ ；

8. The method of claim 1, wherein the dehydrogenation catalyst is prepared by a process comprising the steps of:

9. The method of claim 8, wherein the tin source is selected from one or more of stannous bromide, stannous chloride, stannic chloride pentahydrate, and tetrabutyltin;

10. The method of claim 1, wherein the lower alkane is at least one of propane, butane, and isobutane.