CN113477191B - Reaction device and method for preparing ethylene through oxidative coupling of methane - Google Patents
Reaction device and method for preparing ethylene through oxidative coupling of methane Download PDFInfo
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- CN113477191B CN113477191B CN202110911135.3A CN202110911135A CN113477191B CN 113477191 B CN113477191 B CN 113477191B CN 202110911135 A CN202110911135 A CN 202110911135A CN 113477191 B CN113477191 B CN 113477191B
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
- B01J8/38—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed containing a rotatable device or being subject to rotation or to a circulatory movement, i.e. leaving a vessel and subsequently re-entering it
- B01J8/384—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed containing a rotatable device or being subject to rotation or to a circulatory movement, i.e. leaving a vessel and subsequently re-entering it being subject to a circulatory movement only
- B01J8/388—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed containing a rotatable device or being subject to rotation or to a circulatory movement, i.e. leaving a vessel and subsequently re-entering it being subject to a circulatory movement only externally, i.e. the particles leaving the vessel and subsequently re-entering it
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
- C07C2/82—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen oxidative coupling
- C07C2/84—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen oxidative coupling catalytic
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention discloses a reaction device and a method for preparing ethylene by oxidative coupling of methane. The reaction device comprises a lifting pipe, an oxidizer, a stripper, a pre-lifting section, a cyclone separator and the like; the reaction device adopts a mode of separate feeding of methane and oxygen and multi-mode operation, flexibly controls the supply of oxygen and realizes flexible control between two reaction mechanisms. Oxygen and methane in the feed are not contacted; after the reaction, products such as ethylene and the like are directly led out from the reactor and are not mixed with oxygen. The reactor and the oxidizer are coaxially arranged, wherein the reactor is arranged at the lower part, the oxidizer is arranged at the upper part, and the reactor adopts a riser as the reactor. The invention realizes the complete separation of oxygen and methane in the process of methane oxidative coupling reaction, avoids the contact of products and oxygen, avoids the deep oxidation of the products, reduces the generation of non-selective products, and effectively improves the selectivity and yield of ethylene.
Description
Technical Field
The invention relates to the technical field of petrochemical industry, in particular to a reaction device and a method for preparing ethylene by oxidative coupling of methane.
Background
The natural gas has low price and abundant reserves, and can replace petroleum to become main energy and chemical raw materials. Methane is the main component in natural gas and accounts for 70-90%. At present, natural gas is mainly used as fossil fuel for direct combustion, and the further deep processing of the natural gas is less than 10 percent of the synthetic chemical raw materials. Oxidative Coupling of Methane (OCM) is an important way for preparing ethylene in a non-petroleum route, has the advantages of simple reaction steps, short flow and good economy, and is the research focus of direct conversion of methane at present.
In 1982, the company of United carbon Compounds first proposed that ethylene could be produced by direct oxidative coupling of methane. The Oxidative Coupling of Methane (OCM) reaction is a high temperature (>600 ℃) process with a strong exotherm (>293 kJ/mol). The main reaction equation is shown in table 1.
TABLE 1 kinetic parameters of the oxidative coupling reaction of methane
It is believed that the oxidative coupling of methane proceeds according to a surface catalysis-gas phase free radical reaction mechanism. The reaction for generating ethylene by oxidative coupling of methane mainly comprises three steps of (1) breaking a C-H bond of methane to remove an H atom, and generating a methyl group in a gas phase; (2) coupling of the methyl groups to form ethane; (3) ethane is further oxidatively dehydrogenated to ethylene. There are two ways in which methane can be activated to form methyl groups: methane is activated by oxygen in the gas phase or by lattice oxygen at the catalyst surface.
In the oxidative coupling reaction of methane, when oxygen is used as an oxidant to activate methane, the ratio of methane to oxygen (CH) in the feed4/O2) Affecting the selectivity and yield of ethylene. When the oxygen concentration is lower, the methane conversion rate is lower, and the selectivity and the yield of the ethylene are not high. At higher oxygen concentrations, methane conversion is higher, but the excess oxygen will cause deep oxidation of ethylene and ethane to form non-selective products, CO and CO2Resulting in lower selectivity and yield of ethylene. In addition, CO and CO are formed by methane oxidation2Is much lower than the activation energy for the oxidation of methane to ethane (as shown in table 1), methane will preferentially form CO and CO2Rather than ethane, results in lower selectivity and yield of ethylene in the reaction. Thus, when oxygen is used as the oxidant to activate methane, CH4/O2Feed ratio of (2) and O2The feed position of (a) appears to be critical.
In the methane oxidative coupling reaction, when the catalyst surface lattice oxygen is used as an oxidant to activate methane, no oxygen exists, and C is avoided2+The deep oxidation of the product improves the selectivity and yield of the ethylene. The dehydrogenation of methane and ethane is enhanced by the lattice oxygen on the surface of the catalyst, the generation of ethylene is promoted, and the selectivity and the yield of the ethylene are improved.
The types of fluidized bed reactors currently used in the OCM reaction process mainly include fixed bed reactors, bubbling fluidized bed reactors, circulating fluidized bed reactors, and the like.
Patent application CN2129171Y discloses a thin layer fixed bed methane oxidative coupling reactor consisting of a heat exchanger and a reaction furnace. The lower half part of the reaction furnace is conical, a porous support plate, a packing layer, a catalyst bed layer, a thermoelectric couple and a heater are respectively arranged from the bottom to the top, and the top of the reaction furnace is communicated with a heat exchanger. The device can take away a large amount of exotherms in the methane oxidative coupling reaction, and the catalyst bed layer maintains the required reaction temperature through heat exchange. However, the method adopts a mode of feeding methane and oxygen in a mixed mode, and high-concentration oxygen can cause CO and CO2The large amount of non-selective products and the deep oxidation of ethylene cause C2+The selectivity and yield of hydrocarbons are low.
Patent application CN111744434A discloses a fixed bed reactor for methane oxidative coupling reaction, which comprises a reactor shell, a catalyst bed layer arranged in the reactor shell, a plurality of U-shaped heat extraction tube bundles and a high-pressure steam superheating section. The catalyst bed layer is divided into an upper layer and a lower layer, the upper layer is a heat insulation layer, the lower layer is an approximate isothermal layer, and the lower part of the catalyst bed layer is provided with a high-pressure steam superheating section. Oxygen and methane are fed from the upper part of the catalyst bed layer, react in the catalyst bed layer, and are discharged from the reactor after being cooled by the high-pressure steam superheating section after the reaction. The reaction temperature can be controlled and the reaction heat can be recovered.However, in the reaction process, the heat remover is only arranged at the lower part of the catalyst bed layer, and the catalyst bed layer has larger thickness, is easy to form hot spots and is not beneficial to industrial amplification. And the conversion of methane is only 30 percent, C2+The hydrocarbon selectivity is only 60% -65%.
Patent application CN110227394A discloses a circulating fluidized bed apparatus comprising a fluidized bed reactor, a cyclone separator and a heat exchanger. Methane and oxygen are simultaneously fed from the bottom of the fluidized bed, the coupling reaction is carried out in the fluidized bed, and the product and the catalyst are subjected to gas-solid separation in the cyclone separator. The catalyst is in a fluidized state in the reactor, the relative speed of gas and particles is high, mass and heat transfer are facilitated, the temperature in the fluidized bed is ensured to be uniform, and local overheating is avoided. However, the reaction adopts the mixed feeding of methane and oxygen, so the safety is poor and the deflagration is easy to cause. In addition, oxygen is fed from the bottom of the fluidized bed in a centralized manner, the oxygen concentration at the lower part of the bed layer is too high, a large amount of heat is released in the reaction, and the axial temperature gradient is too large. And the presence of oxygen in large quantities can also lead to CO and CO2Formation of equal amounts of non-selective products, resulting in C2+The selectivity of the hydrocarbon is low. The products cannot be removed in time, resulting in deep oxidation of ethylene, resulting in low ethylene yields.
Disclosure of Invention
The invention aims to provide a reaction device and a method for preparing ethylene by oxidative coupling of methane, which realize separate feeding of methane and oxygen, flexible supply of oxygen, direct extraction of products such as ethylene after generation, no contact with oxygen and effective improvement of the yield of ethylene.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a reaction device for preparing ethylene by oxidative coupling of methane, which comprises a pre-lifting section, a lifting pipe, a catalyst circulating pipe, a gas stripper, an oxidizer and a first cyclone separator;
the riser is used as a reactor, and the upper section of the riser coaxially extends into the inner cavity of the oxidizer from the bottom of the oxidizer; the top of the riser is connected with a first cyclone separator for separating gas products such as ethylene and the like from catalyst solids, and the outlet of the riser of the first cyclone separator is communicated with the outer side of the oxidizer to separate and lead out the products such as ethylene and the like;
an outlet of a cyclone dipleg of the first cyclone separator is communicated with an inner cavity of the oxidizer, and the separated catalyst enters the oxidizer to contact with oxygen; the bottom of the oxidizer is provided with an oxygen inlet, the top of the oxidizer is provided with a gas outlet, and oxygen fed into the oxidizer from the oxygen inlet acts on the catalyst;
the stripper is nested on the outer side of the middle section of the lifting pipe; the bottom of the stripper is provided with a gas inlet, and the feed is oxygen or CO and CO2The top of the stripper is communicated with the bottom of the oxidizer, and the catalyst which is reacted with oxygen enters the stripper;
the bottom of the lower section of the lifting pipe is connected with the pre-lifting section; the bottom of the pre-lifting section is provided with a raw material gas inlet for introducing methane and water vapor;
the inlet of the catalyst circulating pipe is communicated with the gas stripper, and the outlet of the catalyst circulating pipe is communicated with the pre-lifting section; preferably, a catalyst flow control valve is provided on the catalyst circulation pipe.
In this reactor, the riser is used in a coaxial arrangement as a reactor and an oxidizer, with the reactor in the lower part and the oxidizer in the upper part. The top of the riser is provided with a cyclone separator for separating the product and the catalyst. The riser is externally nested with the stripper and is coaxially arranged with the riser. A catalyst circulating pipe is arranged between the gas stripper and the pre-lifting section, the supply of oxygen is flexibly controlled by adopting a mode of methane and oxygen separated feeding and multi-mode operation, and oxygen and methane are not contacted in the feeding process; after reaction, products such as ethylene and the like are directly led out from the lifting pipe through the cyclone separator and are not mixed with oxygen, so that deep oxidation of the products is avoided, the generation of non-selective products is reduced, and the selectivity and the yield of the ethylene are effectively improved.
When the reaction device is used for preparing ethylene by oxidative coupling of methane, when the catalyst surface lattice oxygen is used as an oxidant to activate methane, the riser is fed with methane and water vapor, the oxidizer is fed with oxygen, and the stripper is fed with CO and CO2And (4) mixing the gases. Methane is activated by catalyst lattice oxygen in the riser, and products such as ethylene are directly led out of the reactor (riser) from the top of the riser through the first cyclone separator. The separated catalyst enters the dense phase of the oxidizer through a cyclone dipleg to generate surface lattice oxygen in the oxidizer. The oxidized catalyst flows downward into a stripper where the oxygen adsorbed on the catalyst surface is removed. The stripped catalyst is returned to the pre-lift section through a catalyst circulation tube. Oxygen, CO at the outlet of the oxidizer2Flows out from the gas outlet at the top of the oxidizer.
When oxygen is used as the oxidant to activate methane, the pre-lift section feeds are methane and steam, the oxidizer feed is oxygen, and the stripper feed is oxygen. Methane is activated by oxygen in the riser, products such as ethylene and the like are directly led out of the reactor (riser) from the top of the reactor through the first cyclone separator, and the catalyst separated by the cyclone enters the oxidizer through the cyclone dipleg to be oxidized in a dense phase manner. The oxidized catalyst flows downwards into a stripper, and the catalyst is ensured to have enough contact time with oxygen. The stripped catalyst is returned to the pre-lift section through a catalyst circulation tube.
According to the reaction device of the present invention, preferably, the gas outlet at the top of the oxidizer is connected with a second cyclone separator, the riser of the second cyclone separator is connected with a first compressor, and the outlet of the first compressor is connected to the oxygen inlet at the bottom of the oxidizer; and the cyclone dipleg of the second cyclone separator is communicated with the inner cavity of the oxidizer. And gas flowing out of a gas outlet at the top of the oxidizer is led out through a second cyclone separator, and is circularly led into the oxidizer after being compressed. The recycling of the gas at the outlet of the oxidizer is realized; and a cyclone dipleg of the second cyclone separator is communicated with the oxidizer, and the separated catalyst returns to the oxidizer through the cyclone dipleg.
When the oxygen is used as the oxidant to activate the methane, the gas flowing out of the gas outlet at the top of the oxidizer is the oxygen and is recycled into the oxidizer through an oxygen recycle compressor (a first compressor).
According to the reaction device of the present invention, preferably, the second cyclone separator includes a primary cyclone separator and a secondary cyclone separator which are connected in series, the gas outlet at the top of the oxidizer is connected to the primary cyclone separator, the riser of the primary cyclone separator is connected to the secondary cyclone separator, and the riser of the secondary cyclone separator is connected to the first compressor.
According to the reaction device of the present invention, preferably, the oxygen inlet of the oxidizer comprises an oxygen distributor; the outlet of the first compressor is connected with the oxygen distributor.
According to the reaction apparatus of the present invention, preferably, the reaction apparatus further comprises a gas separation unit;
the riser of the second cyclone separator is connected with the gas separation unit, the gas separation unit comprises an oxygen outlet and a second outlet, and the oxygen outlet is connected with the first compressor. Further preferably, the second outlet of the gas separation unit is connected to a second compressor, the outlet of which is connected to the stripper.
When catalyst surface lattice oxygen is used as an oxidant to activate methane, gas flowing out of a gas outlet at the top of the oxidizer is separated, oxygen is recycled into the oxidizer through an oxygen recycling compressor (a first compressor), and CO are obtained2The mixed gas is recycled into the stripper after being compressed (second compressor).
According to the reaction apparatus of the present invention, preferably, the gas inlet of the stripper comprises a stripper gas distributor;
the outlet of the second compressor is connected to the stripper gas distributor.
According to the reaction device of the present invention, preferably, the raw material gas inlet of the pre-lifting section comprises a raw material gas main inlet pipe and a raw material gas distributor. The raw material gas is methane and water vapor.
According to the reaction apparatus of the present invention, preferably, the oxygen inlet of the oxidizer comprises an oxygen distributor.
According to the reaction apparatus of the present invention, preferably, the reaction apparatus comprises a pre-stripper; the pre-stripper is arranged on the cyclone dipleg of the first cyclone separator.
The pre-stripper feed is steam. Products such as ethylene and the like separated by the first cyclone separator are led out from the air lifting pipe, the separated catalyst enters the pre-stripper at the lower part of the cyclone, entrained products are replaced by the pre-stripper, and the pre-stripped catalyst enters the oxidizer through a cyclone dipleg to be dense-phase.
Further, the water vapor in the product can enter a pre-lifting section and a pre-stripper after being separated for recycling.
According to the reaction device of the present invention, preferably, a nozzle is disposed on the lower section of the riser, and the outlet of the nozzle is located in the riser. More preferably, the outlet direction of the nozzle is inclined downwards with respect to the side wall of the riser.
When oxygen is used as an oxidant to activate methane, a nozzle is arranged on the lower section of the riser; methane is activated by oxygen in the riser, and oxygen is flexibly supplied to the lower section of the riser through a nozzle according to the reaction degree.
The reaction device of the invention adopts a mode of separate feeding of methane and oxygen and multi-mode operation, flexibly controls the supply of oxygen and realizes flexible control between two reaction mechanisms. Oxygen and methane in the feed are not contacted; after the reaction, products such as ethylene and the like are directly led out from the reactor and are not mixed with oxygen. The reactor and the oxidizer are coaxially arranged, wherein the reactor is arranged at the lower part, the oxidizer is arranged at the upper part, and the reactor adopts a riser as the reactor. The invention realizes the complete separation of oxygen and methane in the process of methane oxidative coupling reaction, avoids the contact of products and oxygen, avoids the deep oxidation of the products, reduces the generation of non-selective products, and effectively improves the selectivity and yield of ethylene.
In another aspect, the invention provides a method for preparing ethylene by oxidative coupling of methane, which is carried out by using the reaction device.
According to the method of the present invention, preferably, in the method for preparing ethylene by oxidative coupling of methane, the catalyst surface lattice oxygen is used as an oxidant to activate methane, or the oxygen is used as an oxidant to activate methane.
According to the process of the invention, preference is given toWhen the catalyst surface lattice oxygen is used as an oxidant to activate methane, the feed of the pre-lifting section is methane and water vapor, the feed of the oxidizer is oxygen, and the feed of the stripper is CO and CO2And (4) mixing the gases. Methane is activated by catalyst lattice oxygen in the riser, and products such as ethylene are directly led out of the reactor (riser) from the top of the riser through the first cyclone separator. The separated catalyst enters the dense phase of the oxidizer through a cyclone dipleg to generate surface lattice oxygen in the oxidizer. The oxidized catalyst flows downward into a stripper where the oxygen adsorbed on the catalyst surface is removed. The stripped catalyst is returned to the pre-lift section through a catalyst circulation tube. Oxygen, CO at the outlet of the oxidizer2Flows out from a gas outlet at the top of the oxidizer; further, the outlet of the oxidizer is provided with oxygen, CO and CO2After separation, the oxygen is compressed and then recycled to the oxidizer, CO and CO2The mixed gas is compressed and then recycled to the stripper. More preferably, the catalyst separated by the first cyclone enters a pre-stripper to displace entrained products, and the pre-stripped catalyst enters the dense phase of the oxidizer through a cyclone leg.
According to the method of the present invention, preferably, when the methane is activated by using oxygen as the oxidant, the feed to the pre-lift section is methane and steam, the feed to the oxidizer is oxygen, and the feed to the stripper is oxygen. Methane is activated by oxygen in the riser, products such as ethylene and the like are directly led out from the top of the reactor through the first cyclone separator, and the catalyst separated by the cyclone enters the oxidizer through a cyclone dipleg to be oxidized in a dense phase. The oxidized catalyst flows downwards into a stripper, and the catalyst is ensured to have enough contact time with oxygen. The stripped catalyst is returned to the pre-lift section through a catalyst circulation tube. Further, the oxygen at the outlet of the oxidizer is compressed and then recycled into the oxidizer. More preferably, the catalyst separated by the first cyclone enters a pre-stripper to displace entrained products, and the pre-stripped catalyst enters the dense phase of the oxidizer through a cyclone leg. In addition, the oxygen can be flexibly controlled and added at the lower section of the riser according to the reaction process.
The beneficial effects of the invention include:
the invention adopts a multi-mode operation method that methane and oxygen are separately fed and oxygen is flexibly supplied. Methane and oxygen are separately fed, so that local large heat release and deep oxidation of products caused by overhigh oxygen concentration are avoided, and methane and oxygen are prevented from being directly mixed and exploding. By varying the type of feed to the stripper, operation can be achieved by different mechanisms. When the catalyst surface lattice oxygen is used as an oxidant to activate methane, the methane and the oxygen are not directly contacted in the reaction process, and the product is directly led out of the reactor, so that the deep oxidation of ethylene is avoided, and CO are reduced2And the like, and the formation of non-selective products. The dehydrogenation of methane and ethane is enhanced by the lattice oxygen on the surface of the catalyst, the generation of ethylene is promoted, and the selectivity and the yield of the ethylene are improved. When oxygen is used as oxidant to activate methane, a nozzle can be further arranged on the lift pipe to feed oxygen, so that the supply amount and the supply position of oxygen can be flexibly controlled, and the methane conversion rate and C are improved2+The selectivity of hydrocarbon increases the yield of ethylene.
Drawings
FIG. 1 is a schematic diagram showing the structure and feed of a methane oxidative coupling reaction apparatus according to example 1.
FIG. 2 is a schematic diagram showing the structure and feed of a methane oxidative coupling reaction apparatus according to example 2.
Description of reference numerals:
1 main inlet pipe for raw gas
2 raw material gas distributor
3 Pre-lifting section
4 lifting pipe
4-1 nozzle
5 catalyst circulation pipe
6 gas stripper gas distributor
7 air stripper
8 oxygen distributor
9 oxidizing device
10 first-stage cyclone separator
11 two-stage cyclone separator
12 first cyclone separator
12-1 lift pipe
12-2 cyclone dipleg
13 Pre-stripper
14 gas separation unit
14-1 oxygen outlet
14-2 second outlet
15-1 first compressor
15-2 second compressor
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
Example 1
This example addresses the mechanism of methane activation with lattice oxygen on the catalyst surface as the oxidant in the oxidative coupling of methane reaction.
As shown in figure 1, the reaction device for preparing ethylene by oxidative coupling of methane comprises a pre-lifting section 3, a lifting pipe 4, a catalyst circulating pipe 5, a stripper 7, an oxidizer 9 and a first cyclone separator 12.
The upper section of the riser 4 coaxially extends into the inner cavity of the oxidizer 9 from the bottom of the oxidizer; the top of the riser 4 is connected with a first cyclone separator 12, the outlet of a riser 12-1 of the first cyclone separator 12 is communicated with the outer side of the oxidizer 9, and the outlet of a cyclone dipleg 12-2 of the first cyclone separator 12 is communicated with the inner cavity of the oxidizer 9; a pre-stripper 13 is arranged on the cyclone dipleg of the first cyclone 12.
The bottom of the oxidizer 9 is provided with an oxygen distributor 8, and a gas outlet at the top is connected with a first-stage cyclone separator 10 and a second-stage cyclone separator 11 which are connected in series. Specifically, a gas outlet at the top of the oxidizer 9 is connected with the primary cyclone separator 10, a riser of the primary cyclone separator 10 is connected with the secondary cyclone separator 11, a riser of the secondary cyclone separator 11 is connected with a gas separation unit 14, the gas separation unit 14 comprises an oxygen outlet 14-1 and a second outlet 14-2, the oxygen outlet 14-1 is connected with the first compressor 15-1, an outlet of the first compressor 15-1 is connected with the oxygen distributor 8, and cyclone diplegs of the primary cyclone separator 10 and the secondary cyclone separator 11 are both communicated with an inner cavity of the oxidizer 9. The second outlet 14-2 of the gas separation unit 14 is connected to a second compressor 15-2, the outlet of the second compressor 15-2 being connected to the stripper gas distributor 6.
The stripper 7 is nested on the outer side of the middle section of the riser 4; the bottom of the stripper 7 is provided with a stripper gas distributor 6, and the top of the stripper 7 is communicated with the bottom of the oxidizer 9.
The bottom of the lower section of the riser 4 is connected with a pre-lifting section 3; the bottom of the pre-lifting section 3 is provided with a raw material gas inlet which comprises a raw material gas main inlet pipe 1 and a raw material gas distributor 2.
The inlet of the catalyst circulation pipe 5 is communicated with the stripper 7, and the outlet is communicated with the pre-lifting section 3. And a catalyst flow control valve is arranged on the catalyst circulating pipe 5.
The device adopts a mode of separately feeding methane and oxygen, and the oxygen and the methane are not contacted in the feeding process; the riser 4 is used as a reactor for reaction, and products such as ethylene and the like are directly led out from the reactor after reaction and are not mixed with oxygen. The reactor (riser 4) and oxidizer 9 are in a coaxial arrangement with the reactor (riser 4) in the lower portion and the oxidizer 9 in the upper portion. The top of the riser 4 is provided with a first cyclone separator 12 for separating reaction products and the catalyst, and a pre-stripper 13 is arranged on the cyclone dipleg 12-2 for replacing products carried by the catalyst. The stripper 7 is nested outside the riser 4 and is arranged coaxially with the riser 4. The inlet of the catalyst circulation pipe 5 is connected to the stripper 7 and the outlet is connected to the pre-lift section 3. The oxidative coupling reaction of methane takes place in the riser 4, the oxidation of the catalyst takes place in the oxidizer 9, and the gas at the outlet of the oxidizer 9 passes throughAnd the gas separation unit 14 is separated, compressed and returned to the oxidizer 9 and the stripper 7 respectively, so that the recycling is realized. Methane and water vapor are introduced into a raw gas inlet at the bottom of the pre-lifting section 3, oxygen is introduced into an oxygen inlet at the bottom of the oxidizer 9, and CO are introduced into a gas inlet at the bottom of the gas stripper 72Steam is introduced into the mixed gas and the raw gas inlet at the bottom of the pre-stripper 13.
The specific implementation process of the embodiment is as follows: methane and water vapor are fed from the bottom of the pre-lifting section 3 and react in the lifting pipe 4 under the activation of the catalyst to generate ethylene, and products are directly led out from a lifting pipe 12-1 of a first cyclone separator 12 at the top of the lifting pipe 4. The catalyst after reaction enters a pre-stripper 13 at the lower part of a cyclone separator 12, steam is introduced into the pre-stripper 13 to replace products carried by catalyst particles, the catalyst after pre-stripping enters an oxidizer 9 through a cyclone dipleg 12-2 to form dense phase, oxygen is introduced into the oxidizer 9, and lattice oxygen is generated on the surface of the oxidation catalyst. The oxidized catalyst flows downwards to enter a stripper 7, and CO are introduced into the stripper 72Mixing the gas to remove the oxygen adsorbed on the surface of the catalyst. The catalyst passes through the stripper 7 and returns to the pre-lift section 3 through the catalyst circulation tube 5. Oxygen, CO and CO at outlet of oxidizer 92Flows out from the top of the oxidizer, is separated, and then enters the oxidizer 9 through the oxygen recycle compressor in a recycle mode, wherein CO and CO are2The mixed gas is recycled into stripper 7. The steam in the product can enter the pre-lifting section 3 and the pre-stripper 13 after being separated, and CO can enter the pre-stripper2After separation, the separated product can enter a stripper 7 for recycling.
Example 2
This example addresses the mechanism of methane activation with oxygen as the oxidant in the oxidative coupling of methane reaction.
As shown in FIG. 2, the reaction device for preparing ethylene by oxidative coupling of methane comprises a pre-lifting section 3, a lifting pipe 4, a catalyst circulating pipe 5, a stripper 7, an oxidizer 9 and a first cyclone separator 12.
The upper section of the riser 4 coaxially extends into the inner cavity of the oxidizer 9 from the bottom of the oxidizer; the top of the riser 4 is connected with a first cyclone separator 12, the outlet of a riser 12-1 of the first cyclone separator 12 is communicated with the outer side of the oxidizer 9, and the outlet of a cyclone dipleg 12-2 of the first cyclone separator 12 is communicated with the inner cavity of the oxidizer 9; a pre-stripper 13 is arranged on the cyclone dipleg of the first cyclone 12.
The bottom of the oxidizer 9 is provided with an oxygen distributor 8, and a gas outlet at the top is connected with a first-stage cyclone separator 10 and a second-stage cyclone separator 11 which are connected in series. Specifically, a gas outlet at the top of the oxidizer 9 is connected with the primary cyclone separator 10, a riser of the primary cyclone separator 10 is connected with the secondary cyclone separator 11, a riser of the secondary cyclone separator 11 is connected with the first compressor 15-1, an outlet of the first compressor 15-1 is connected to the oxygen distributor 8, and cyclone diplegs of the primary cyclone separator 10 and the secondary cyclone separator 11 are both communicated with an inner cavity of the oxidizer 9.
The stripper 7 is nested on the outer side of the middle section of the riser 4; the bottom of the stripper 7 is provided with a stripper gas distributor 6, and the top of the stripper 7 is communicated with the bottom of the oxidizer 9.
The bottom of the lower section of the riser 4 is connected with a pre-lifting section 3; the bottom of the pre-lifting section 3 is provided with a raw material gas inlet which comprises a raw material gas main inlet pipe 1 and a raw material gas distributor 2. A nozzle 4-1 is arranged on the lower section of the riser 4, the outlet of the nozzle 4-1 is positioned in the riser 4, and the outlet direction is inclined downwards relative to the side wall of the riser 4.
The inlet of the catalyst circulation pipe 5 is communicated with the stripper 7, and the outlet is communicated with the pre-lifting section 3. And a catalyst flow control valve is arranged on the catalyst circulating pipe 5.
The device adopts a mode of separately feeding methane and oxygen, the methane and the oxygen are not in contact, and the oxygen is flexibly supplied; after the reaction, products such as ethylene and the like are directly led out without mixing with oxygen. The reaction adopts a riser 4 as a reactor, the riser 4 and an oxidizer 9 are coaxially arranged, wherein the riser 4 is arranged at the lower part, the oxidizer 9 is arranged at the upper part, and a nozzle 4-1 is arranged on the riser 4 for supplying oxygen, so that the oxygen supply amount and the oxygen supply position can be flexibly controlled. The top of the riser 4 is provided with a first cyclone separator 12 for separating reaction products and the catalyst, and a pre-stripper 13 is arranged on the cyclone dipleg 12-2 for replacing products carried by catalyst particles. The stripper 7 is nested outside the riser 4 and is arranged coaxially with the riser 4. The inlet of the catalyst circulating pipe 5 is connected with the gas stripper 4, and the outlet is connected with the pre-lifting section 3. The methane oxidation coupling reaction is carried out in the riser 4, the catalyst oxidation is carried out in the oxidizer 9, and the gas at the outlet of the oxidizer 9 is compressed by the first compressor 15-1 and then returns to the oxidizer 9, so that the recycling of the oxygen is realized. Methane and steam are introduced into the bottom inlet of the pre-lifting section 3, oxygen is introduced into the bottom inlet of the oxidizer 9, oxygen is introduced into the bottom inlet of the stripper 7, oxygen is introduced into the nozzle 4-1, and steam is introduced into the bottom inlet of the pre-stripper 13.
The specific implementation process of the embodiment is as follows: methane and water vapor are fed from the bottom of the pre-lifting section 3, oxygen is fed obliquely downwards from a nozzle 4-1 arranged on the lifting pipe 4, so that the oxygen is fully mixed with the catalyst in the lifting pipe 4, the methane and the water vapor and react in the lifting pipe 4 to generate products such as ethylene, and the products are directly led out from a lifting pipe 12-1 of a first cyclone separator 12 at the top of the lifting pipe 4. The catalyst after reaction enters a pre-stripper 13 at the lower part of the cyclone, steam is introduced into the pre-stripper 13 to displace products carried by catalyst particles, the catalyst after pre-stripping enters an oxidizer 9 through a cyclone dipleg 12-2 to be oxidized in a dense phase, the oxidized catalyst flows downwards to enter a stripper 7, and oxygen is introduced into the stripper 7 to ensure that the catalyst has enough contact time with the oxygen. The catalyst passes through the stripper 7 and returns to the pre-lift section 3 through the catalyst circulation tube 5. Oxygen at the outlet of the oxidizer 9 is separated by a primary cyclone separator 10 and a secondary cyclone separator 11, compressed by a first compressor 15-1 and then recycled into the oxidizer 9. The water vapor in the product can enter the pre-lifting section 3 and the pre-stripper 13 after being separated, and can be recycled.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (17)
1. A reaction device for preparing ethylene by oxidative coupling of methane is characterized by comprising a pre-lifting section (3), a lifting pipe (4), a catalyst circulating pipe (5), a stripper (7), an oxidizer (9) and a first cyclone separator (12);
the upper section of the lifting pipe (4) coaxially extends into the inner cavity of the oxidizer (9) from the bottom of the oxidizer; the top of the riser (4) is connected with a first cyclone separator (12), the outlet of a riser (12-1) of the first cyclone separator (12) is communicated with the outer side of the oxidizer (9), and the outlet of a cyclone dipleg (12-2) of the first cyclone separator (12) is communicated with the inner cavity of the oxidizer (9); the bottom of the oxidizer (9) is provided with an oxygen inlet, and the top of the oxidizer is provided with a gas outlet;
the stripper (7) is nested on the outer side of the middle section of the lifting pipe (4); the bottom of the stripper (7) is provided with a gas inlet, and the top of the stripper (7) is communicated with the bottom of the oxidizer (9);
the bottom of the lower section of the lifting pipe (4) is connected with the pre-lifting section (3); a raw material gas inlet is formed in the bottom of the pre-lifting section (3);
the inlet of the catalyst circulating pipe (5) is communicated with the stripper (7), and the outlet is communicated with the pre-lifting section (3).
2. The reaction device according to claim 1, characterized in that the gas outlet at the top of the oxidizer (9) is connected with a second cyclone, the riser of the second cyclone is connected with a first compressor (15-1), the outlet of the first compressor (15-1) is connected with the oxygen inlet at the bottom of the oxidizer (9); the cyclone dipleg of the second cyclone separator is communicated with the inner cavity of the oxidizer (9).
3. The reactor according to claim 2, wherein the second cyclone comprises a primary cyclone (10) and a secondary cyclone (11), the gas outlet at the top of the oxidizer (9) is connected with the primary cyclone (10), the riser of the primary cyclone (10) is connected with the secondary cyclone (11), and the riser of the secondary cyclone (11) is connected with the first compressor (15-1).
4. A reactor device as claimed in claim 3, characterized in that the oxygen inlet of the oxidizer (9) comprises an oxygen distributor (8); the outlet of the first compressor (15-1) is connected with the oxygen distributor (8).
5. A reactor device according to any one of claims 2-3, characterized in that it further comprises a gas separation unit (14);
the riser of the second cyclone separator is connected with the gas separation unit (14), the gas separation unit (14) comprises an oxygen outlet (14-1) and a second outlet (14-2), and the oxygen outlet (14-1) is connected with the first compressor (15-1).
6. The reactor according to claim 5, characterized in that the second outlet (14-2) of the gas separation unit (14) is connected to a second compressor (15-2), the outlet of the second compressor (15-2) being connected to the gas inlet at the bottom of the stripper (7).
7. The reactor according to claim 6, characterized in that the gas inlet of the stripper (7) comprises a stripper gas distributor (6);
the outlet of the second compressor (15-2) is connected to the stripper gas distributor (6).
8. A reactor according to claim 1, characterized in that the feed gas inlet of the pre-lifting section (3) comprises a feed gas main inlet pipe (1) and a feed gas distributor (2).
9. A reactor device as claimed in claim 8, characterized in that the oxygen inlet of the oxidizer (9) comprises an oxygen distributor (8).
10. The reaction device according to claim 1, characterized in that it comprises a pre-stripper (13); the pre-stripper (13) is arranged on the cyclone dipleg (12-2) of the first cyclone separator (12).
11. A reactor device according to claim 1, characterized in that the catalyst circulation pipe (5) is provided with a catalyst flow control valve.
12. The reactor according to claim 1, characterized in that a nozzle (4-1) is arranged on the lower section of the riser (4), the outlet of the nozzle (4-1) being located inside the riser (4).
13. The reactor according to claim 12, characterized in that the outlet direction of the nozzles (4-1) is inclined downwards with respect to the side wall of the riser (4).
14. A process for the oxidative coupling of methane to ethylene, characterized in that it is carried out using a reaction apparatus according to any one of claims 1 to 13.
15. The method according to claim 14, wherein in the method for preparing ethylene by oxidative coupling of methane, the catalyst surface lattice oxygen is used as an oxidant to activate methane, or the oxygen is used as an oxidant to activate methane.
16. The method of claim 15, wherein the catalyst is usedWhen the superficial lattice oxygen is used as an oxidant to activate methane, the feed of the pre-lifting section (3) is methane and water vapor, the feed of the oxidizer (9) is oxygen, and the feed of the stripper (7) is CO and CO2And (4) mixing the gases.
17. The process according to claim 15, characterized in that when activating methane with oxygen as oxidant, the feed to the pre-lift section (3) is methane and water vapor, the feed to the oxidizer (9) is oxygen, and the feed to the stripper (7) is oxygen.
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