Method and system for reducing circulating gas amount in aromatic hydrocarbon conversion reaction process and application

Abstract

The invention discloses a method and a system for reducing circulation gas amount in an aromatic hydrocarbon conversion reaction process and application. The method provided by the invention comprises the following steps: the aromatic hydrocarbon conversion reaction comprises a hydrogen and / or hydrogenation reaction; separating a product after the aromatic hydrocarbon conversion reaction to obtain a liquid-phase product and a gas-phase product; hydrogen is supplemented into the gas-phase product, then hydrogen purification treatment is conducted, and methane-rich gas and purified hydrogen are obtained; and the purified hydrogen is used as recycle gas for aromatic hydrocarbon conversion reaction. According to the method, on one hand, the circulating gas amount can be greatly reduced, so that the energy consumption of the compressor, the supplementary hydrogen amount and the purge gas emission amount are reduced; and on the other hand, the light hydrocarbon content in the recycle gas can be reduced, the hydrogen partial pressure in the reaction system is easier to control, the catalyst is not easy to coke and inactivate, and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of aromatic hydrocarbon conversion reactions. Further, it relates to a method and system for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction process and applications thereof. Background Art

[0002] Aromatic hydrocarbons (including benzene, toluene, xylene, etc.) are important basic raw materials in the petrochemical industry. The largest use of benzene in aromatic hydrocarbons is in the production of styrene, cyclohexane, and phenol, as well as nitrobenzene, maleic anhydride, chlorobenzene, linear alkylbenzene, etc. Most of the toluene is used for blending oils and also as a raw material for dealkylation to produce benzene and disproportionation and transalkylation. Among the three isomers of xylene, p-xylene is an important raw material for the polyester industry and has a wide range of uses in many chemical production fields such as chemical fibers, plastics, and rubber. The large-scale industrial production of the above three aromatic hydrocarbons is achieved through an aromatic hydrocarbon combined unit. The aromatic hydrocarbon combined unit usually includes units for producing aromatic hydrocarbons such as naphtha reforming or pyrolysis gasoline hydrogenation, as well as units for aromatic hydrocarbon conversion, aromatic hydrocarbon separation, etc. Among them, aromatic hydrocarbon conversion includes units such as disproportionation and transalkylation, dealkylation to produce benzene, and xylene isomerization, and aromatic hydrocarbon separation includes units such as aromatic hydrocarbon extraction, aromatic hydrocarbon fractionation, and p-xylene separation.

[0003] The technology for dealkylating aromatic hydrocarbons to produce benzene is to produce benzene by removing the side chain substituents of alkylbenzene. The purpose is to convert toluene and C 9 and higher aromatic hydrocarbons with relatively less direct use and relative surplus into benzene with wide uses, so as to increase the production of benzene and its derived chemical products and meet the demand in areas with insufficient benzene resources. It is an important means to improve the utilization rate of aromatic hydrocarbons.

[0004] The main process routes for dealkylating aromatic hydrocarbons to produce benzene include hydrodealkylation, non-hydrogen dealkylation, steam reforming dealkylation, etc. At present, the mainly mature and large-scale applied technology is the aromatic hydrocarbon hydrodealkylation process. The aromatic hydrocarbon hydrodealkylation process includes thermal cracking hydrodealkylation and catalytic hydrodealkylation processes. The catalytic hydrodealkylation process has a lower apparent reaction activation energy due to the use of a catalyst, making it have a lower reaction temperature and higher benzene selectivity than the thermal cracking hydrodealkylation process. However, the inventors of the present invention found that both the thermal cracking hydrodealkylation and catalytic hydrodealkylation technologies have technical defects such as a large recycle gas volume resulting in a high compressor power, a large amount of olefins carried in the recycle gas leading to easy coking of the catalyst, and at the same time, the recycle gas contains too much C 1 ~C 6 components, resulting in difficulty in controlling the hydrogen partial pressure in the reaction system, etc. As a result, the economy of this technology is poor, seriously restricting the commercialization process of the technology.

[0005] Chinese Patent CN115141074A discloses a method for producing benzene from light aromatics, the steps are as follows: Mix light aromatics with hydrogen and enter a dealkylation reactor. Under the action of a dealkylation catalyst, the alkyl side chains are highly selectively removed to produce benzene. The C 7 ~C 9 components are returned as recycle oil and mixed with the light aromatics feedstock and then enter the dealkylation reactor again to further increase the production of benzene. This method uses a reactor different from the existing fixed-bed reactor and develops a new catalyst matching it, and carries out the dealkylation reaction to produce benzene under milder conditions.

[0006] Chinese Patent CN115141652A discloses a method for lightening a benzene-rich fraction oil to produce benzene. The steps include that the benzene-rich fraction oil is selectively hydrogenated in a pre-hydrogenation reactor and then enters a lightening dealkylation reactor in an isobaric series connection. Under the action of a catalyst loaded in a graded manner, it is selectively hydrocracked to produce benzene. The reaction product is separated to obtain hydrogen, dry gas, liquefied gas, C 5 light hydrocarbons, benzene, C 7 ~C 9 components, C 10 + components, among which the C 10 + components are returned to the feed inlet of the lightening dealkylation reactor, and the C 7 ~C 9 components are returned as the refrigerant in the lightening section to the middle section of the lightening dealkylation reactor to further produce benzene.

[0007] The above several methods achieve the purpose of aromatics hydrodealkylation to produce benzene through different process routes. However, in order to maintain the hydrogen purity in the recycle gas of the reaction system, there are also the following problems: (1) The recycle gas volume is large, and the energy consumption of the reaction system is large; (2) The make-up amount of make-up hydrogen and the discharge amount of purge gas are large. Summary of the Invention

[0008] To solve the problems in the prior art, the present invention proposes a method, a system and an application for reducing the recycle gas volume in the aromatics conversion reaction process. The method of the present invention introduces a hydrogen purification device into the aromatics conversion reaction system, so that the gas-phase product of the aromatics conversion reaction and the supplemented hydrogen are processed by the purification device to improve the hydrogen purity and remove the methane-rich gas and then returned to the aromatics conversion reactor as recycle gas. On the one hand, the recycle gas volume can be greatly reduced, thereby reducing the compressor energy consumption, the make-up hydrogen amount and the purge gas discharge amount; on the other hand, the light hydrocarbon content in the recycle gas can be reduced, making it easier to control the hydrogen partial pressure in the reaction system, the catalyst is not easy to coke and deactivate, and the service life of the catalyst is prolonged.

[0009] One of the purposes of the present invention is to provide a method for reducing the recycle gas volume in the aromatics conversion reaction process, including the following steps:

[0010] The aromatic hydrocarbon conversion reaction includes hydroconversion and / or hydrogenation reactions; the products after the aromatic hydrocarbon conversion reaction are separated to obtain a liquid-phase product and a gas-phase product; hydrogen is supplemented into the gas-phase product, and then hydrogen purification treatment is carried out to obtain methane-rich gas and purified hydrogen; the purified hydrogen is used as recycle gas in the aromatic hydrocarbon conversion reaction.

[0011] In the method for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction according to the present invention, preferably, the following steps are included:

[0012] (a) The aromatic hydrocarbon and the recycle gas are subjected to an aromatic hydrocarbon conversion reaction under the action of a catalyst to generate reaction products;

[0013] (b) After cooling the reaction products, gas-liquid separation is carried out to obtain a liquid-phase product and a gas-phase product containing hydrogen;

[0014] (c) Hydrogen is supplemented into the gas-phase product, and then hydrogen purification treatment is carried out to obtain methane-rich gas and purified hydrogen; the purified hydrogen is used as recycle gas in the aromatic hydrocarbon conversion reaction;

[0015] (d) Optionally, the liquid-phase product enters a distillation separation system, and light alkanes and light aromatic hydrocarbons are sequentially separated, and the remaining heavy components are recycled to step (a) to continue to participate in the aromatic hydrocarbon conversion reaction.

[0016] In the technical solution of the present invention,

[0017] The aromatic hydrocarbon and the recycle gas can be mixed and preheated and then introduced into an aromatic hydrocarbon conversion reactor for the aromatic hydrocarbon conversion reaction.

[0018] In the method for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction according to the present invention, preferably,

[0019] Step (a),

[0020] The aromatic hydrocarbon is selected from at least one of aromatic hydrocarbons having 7 or more carbon atoms; preferably, the aromatic hydrocarbon is selected from at least one of aromatic hydrocarbons of C 7 ~C 12 ; more preferably, the aromatic hydrocarbon is selected from at least one of toluene and heavy aromatic hydrocarbons of C 9 ~C 12 ;

[0021] Even more preferably, the aromatic hydrocarbon contains toluene and heavy aromatic hydrocarbons of C 9 ~C 12 ; still more preferably, the mass content of heavy aromatic hydrocarbons of C 9 ~C 12 in the aromatic hydrocarbon is 0 to 70%.

[0022] In the method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process of the present invention, preferably, step (a),

[0023] The hydrogen content in the recycle gas is 90.0 - 99.9 mol%, preferably 99.0 - 99.9 mol%; the balance is mainly C 1 -C 6 alkanes.

[0024] In the method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process of the present invention, preferably, step (a),

[0025] During the aromatic hydrocarbon conversion reaction,

[0026] The mass space velocity of the reaction feed is 0.5 - 5.5 h -1 ; preferably 1.0 - 3.0 h -1 ; and / or,

[0027] The hydrogen-hydrocarbon molar ratio is 1.0 - 6.0; preferably 2.0 - 4.0.

[0028] In the method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process of the present invention, preferably, step (a),

[0029] During the aromatic hydrocarbon conversion reaction,

[0030] The reaction temperature is 200 - 750 °C, preferably 300 - 600 °C; and / or,

[0031] The reaction pressure is 2.0 MPaG - 7.0 MPaG, preferably 2.5 MPaG - 5.5 MPaG; and / or,

[0032] The aromatic hydrocarbon conversion reaction is a toluene and heavy aromatic hydrocarbon disproportionation and transalkylation reaction, a heavy aromatic hydrocarbon lightening reaction, or an aromatic hydrocarbon hydrodealkylation reaction; in the technical solution of the present invention, the aromatic hydrocarbon hydrodealkylation reaction (hydrogenation reaction), the disproportionation and transalkylation reaction (hydrogenation reaction), and the pure toluene disproportionation reaction (hydrogenation reaction).

[0033] In the method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process of the present invention, preferably,

[0034] Step (b),

[0035] The gas-phase product mainly contains hydrogen, C 1 -C 6 alkanes and benzene; preferably, the hydrogen content in the gas-phase product is 10 - 50 wt%; more preferably 15 - 45 wt%;

[0036] Even more preferably,

[0037] When the aromatic hydrocarbon conversion reaction is an aromatic hydrocarbon hydrodealkylation reaction, the hydrogen content in the gas-phase product is 10-20 wt%; preferably 12-18 wt%; and / or,

[0038] When the aromatic hydrocarbon conversion reaction is a disproportionation and transalkylation reaction, the hydrogen content in the gas-phase product is 10-20 wt%; preferably 12-18 wt%; and / or,

[0039] When the aromatic hydrocarbon conversion reaction is a pure toluene disproportionation reaction, the hydrogen content in the gas-phase product is 30-50 wt%; preferably 35-45 wt%.

[0040] In the technical solution of the present invention, the cooling temperature is 30-50 °C, preferably 35-45 °C.

[0041] In the method for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction described in the present invention, preferably,

[0042] Step (c),

[0043] The volume ratio of the gas-phase product to the hydrogen supplemented is 2.0-30.0; preferably,

[0044] When the aromatic hydrocarbon conversion reaction is an aromatic hydrocarbon hydrodealkylation reaction, the volume ratio of the gas-phase product to the hydrogen supplemented is 2.0-6.0, preferably 3.0-5.0; and / or,

[0045] When the aromatic hydrocarbon conversion reaction is a disproportionation and transalkylation reaction, the volume ratio of the gas-phase product to the hydrogen supplemented is 5.0-15.0, preferably 8.0-12.0; and / or,

[0046] When the aromatic hydrocarbon conversion reaction is a pure toluene disproportionation reaction, the volume ratio of the gas-phase product to the hydrogen supplemented is 20.0-30.0, preferably 22.0-28.0.

[0047] In the technical solution of the present invention, the catalyst can be a catalyst commonly used in the aromatic hydrocarbon conversion reaction in the prior art. Preferably,

[0048] When used in the reaction of producing benzene by aromatic hydrocarbon hydrodealkylation, the catalyst in step (a) is the catalyst described in the invention patent ZL201210412569.X (CN103772123A).

[0049] When used in the disproportionation and transalkylation reaction, the catalyst in step (a) is the catalyst described in the invention patent ZL201110369964.X (CN103121915A).

[0050] When used in the pure toluene disproportionation reaction, the catalyst described in step (a) is the catalyst described in the invention patent ZL201310129905.4 (CN104107714A).

[0051] In the method for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction process of the present invention, preferably,

[0052] The method of hydrogen purification treatment is one or more of PSA hydrogen production, chemical adsorption, or membrane separation, preferably PSA hydrogen production.

[0053] The second object of the present invention is to provide a system for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction process, including an aromatic hydrocarbon conversion reactor, a reaction product cooler, a gas-liquid separator, a hydrogen purification device, and optionally a compressor;

[0054] The outlet of the aromatic hydrocarbon conversion reactor is successively connected to the reaction product cooler and the gas-liquid separator; the gas-phase outlet of the gas-liquid separator is connected to the inlet of the hydrogen purification device (that is, the outlet of the aromatic hydrocarbon conversion reactor is connected to the reaction product cooler, and the reaction product cooler is connected to the gas-liquid separator); a supplementary hydrogen feed pipeline and a rich methane gas discharge pipeline are also provided on the hydrogen purification device; the hydrogen purified by the hydrogen purification device is discharged from the recycle gas outlet, and the recycle gas outlet is connected to the inlet of the aromatic hydrocarbon conversion reactor or the recycle gas outlet is connected to the inlet of the compressor, and the outlet of the compressor is connected to the inlet of the aromatic hydrocarbon conversion reactor; the inlet of the aromatic hydrocarbon conversion reactor is also connected to an aromatic hydrocarbon feed pipeline;

[0055] Preferably, the method for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction process described in one of the objects of the present invention is adopted in the system.

[0056] In the system for reducing the recycle gas volume during the aromatic hydrocarbon conversion reaction process of the present invention, preferably,

[0057] The system further includes a feed pump, and the feed pump is connected to the inlet of the aromatic hydrocarbon conversion reactor through an aromatic hydrocarbon feed pipeline; and / or,

[0058] The system further includes a rectification separation device, and the liquid-phase product outlet of the gas-liquid separator is connected to the inlet of the rectification separation device; and / or,

[0059] The reaction product cooler is a heat exchanger; and / or,

[0060] The number of aromatic hydrocarbon conversion reactors is one or more, preferably 2 to 4, and the aromatic hydrocarbon conversion reactors are connected in series; and / or,

[0061] The hydrogen purification device is one or more of a PSA hydrogen production device, a chemical adsorption hydrogen purification device, or a membrane separation hydrogen purification device.

[0062] In the technical solution of the present invention, the main function of the compressor is to increase the pressure of the recycle gas. If the pressure of the recycle gas processed in the hydrogen purification device already meets the process requirements, the compressor is not required (for example, the PSA hydrogen production device has a compressor inside, and the recycle gas coming out of it can meet the requirements). If it does not meet the requirements, a compressor is needed to increase the pressure.

[0063] In the technical solution of the present invention, the aromatic hydrocarbon feed pipeline and the recycle gas are mixed and heated and then enter the aromatic hydrocarbon conversion reactor; for example, after the pipeline where the aromatic hydrocarbon feed pipeline and the recycle gas are mixed, a heater can be further connected to heat the mixed gas, and then the mixed gas is sent to the aromatic hydrocarbon conversion reactor. It is also possible to set a jacket on the pipeline where the aromatic hydrocarbon feed pipeline and the recycle gas are mixed to achieve heating during the pipeline transportation process.

[0064] The third object of the present invention is to provide an application of a method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process as described in the first object of the present invention or a system for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process as described in the second object of the present invention in the aromatic hydrocarbon conversion reaction production process.

[0065] In the ranges and any values disclosed in the present invention, the endpoints and any values of the ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0066] Compared with the prior art, the present invention has at least the following advantages:

[0067] The method described in the present invention can be used in aromatic hydrocarbon conversion reactions such as toluene disproportionation and transalkylation, and aromatic hydrocarbon catalytic hydrodealkylation, etc., and has the advantages of a small recycle gas volume, low compressor energy consumption, a small make-up hydrogen volume, and a small purge gas emission volume. Description of the Drawings

[0068] Figure 1 It is a schematic diagram of a system for reducing the recycle gas volume in an aromatic hydrocarbon conversion reaction process of the present invention.

[0069] Description of the reference numerals:

[0070] 1 - Feed pump;

[0071] 2 - Aromatic hydrocarbon conversion reactor;

[0072] 3 - Reaction product cooler;

[0073] 4 - Gas - liquid separator;

[0074] 5 - Hydrogen purification device;

[0075] 101 - Aromatics;

[0076] 102 - Aromatics feed pipeline;

[0077] 201 - Reaction product;

[0078] 301 - Cooled reaction product;

[0079] 401 - Gas - phase product;

[0080] 402 - Liquid - phase product;

[0081] 501 - Make - up hydrogen feed pipeline;

[0082] 502 - Methane - rich gas;

[0083] 503 - Recycle gas.

[0084] Figure 1 Among them,

[0085] The aromatics 101 are pressurized by the feed pump 1 and then enter the aromatics conversion reactor 2 after being mixed with the recycle gas 503 (from the hydrogen purification device 5) through the aromatics feed pipeline 102. They contact the catalyst in the aromatics conversion reactor 2 to react. The generated reaction product 201 is cooled by the reaction product cooler 3 to obtain the cooled reaction product 301, and then enters the gas - liquid separator 4. The gas - phase product 401 and the liquid - phase product 402 are separated. The gas - phase product 401 is introduced into the hydrogen purification device 5, and at the same time, make - up hydrogen is introduced through the make - up hydrogen feed pipeline 501 for hydrogen purification treatment, generating methane - rich gas 502 and recycle gas 503 (hydrogen with higher purity). The recycle gas 503 returns to the feed inlet of the aromatics conversion reactor 2, and the liquid - phase product 402 enters the distillation separation system. Specific embodiments

[0086] The present invention will be specifically described below in conjunction with specific drawings and embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non - essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0087] In addition, it should be noted that in the following specific embodiments, the various specific technical features described can be combined in any suitable way without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0088] In addition, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original public content of this specification and also fall within the protection scope of the present invention.

[0089] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0090] Example 1

[0091] As Figure 1 shown, a system for reducing the recycle gas volume in the process of aromatic hydrocarbon conversion reaction of the present invention includes an aromatic hydrocarbon conversion reactor 2, a reaction product cooler 3, a gas-liquid separator 4, and a hydrogen purification device 5;

[0092] The outlet of the aromatic hydrocarbon conversion reactor is successively connected to the reaction product cooler and the gas-liquid separator; the gas-phase outlet of the gas-liquid separator is connected to the inlet of the hydrogen purification device; a supplementary hydrogen feed pipeline and a rich methane gas discharge pipeline are also provided on the hydrogen purification device; the hydrogen purified by the hydrogen purification device is discharged from the recycle gas outlet, and the recycle gas outlet is connected to the inlet of the aromatic hydrocarbon conversion reactor; the inlet of the aromatic hydrocarbon conversion reactor is also connected to an aromatic hydrocarbon feed pipeline;

[0093] The system further includes a feed pump 1, and the feed pump is connected to the inlet of the aromatic hydrocarbon conversion reactor through the aromatic hydrocarbon feed pipeline; the reaction product cooler is a heat exchanger; the number of aromatic hydrocarbon conversion reactors is 1; the hydrogen purification device is a PSA hydrogen production device, and there is a compressor inside the PSA hydrogen production device, and the recycle gas coming out of it can meet the pressure requirements without the need to newly add a compressor.

[0094] Figure 1 In, the aromatic hydrocarbon 101 is pressurized by the feed pump 1 and enters the aromatic hydrocarbon conversion reactor 2 after being mixed with the recycle gas 503 (from the hydrogen purification device 5) through the aromatic hydrocarbon feed pipeline 102, contacts the catalyst in the aromatic hydrocarbon conversion reactor 2 and reacts. The generated reaction product 201 is cooled by the reaction product cooler 3 to obtain the cooled reaction product 301, and then enters the gas-liquid separator 4 to separate the gas-phase product 401 and the liquid-phase product 402. The gas-phase product 401 is introduced into the hydrogen purification device 5, and at the same time, supplementary hydrogen is introduced through the supplementary hydrogen feed pipeline 501 for hydrogen purification treatment to generate rich methane gas 502 and recycle gas 503 (hydrogen with higher purity), and the recycle gas 503 returns to the feed inlet of the aromatic hydrocarbon conversion reactor 2, and the liquid-phase product 402 enters the distillation separation system.

[0095] Example 2

[0096] A method for reducing the recycle gas volume in an aromatics conversion reaction process, using a system for reducing the recycle gas volume in an aromatics conversion reaction process as shown in Figure 1 and including the following steps:

[0097] Aromatics (by weight, containing 80% C 9 aromatics and 20% C 10 aromatics) are mixed with a recycle gas containing 99 mol% hydrogen, and the molar ratio of hydrogen to hydrocarbons after mixing is 4.5. After being heated to 540 °C, it is sent to an aromatics conversion reactor for the hydrodealkylation reaction to produce benzene. The reaction pressure is 3.5 MPaG, and the mass space velocity is 1.5 h -1 . The catalyst filled in the reactor is prepared according to Example 4 of the authorized patent ZL201210412569.X (CN103772123A). After the reaction product is cooled to 40 °C, it is sent to a gas-liquid separator. After the gas-liquid separator, the hydrogen content in the gas-phase product is 16 wt%, and all the gas-phase products are sent to a PSA hydrogen production device. The volume ratio of the gas-phase product to the supplemented hydrogen is 2.5. The liquid-phase product in the gas-liquid separator is sent to a distillation separation system. The recycle gas volume and the supplemented hydrogen amount in the reaction system are shown in Table 1.

[0098] Example 3

[0099] A method for reducing the recycle gas volume in an aromatics conversion reaction process, using a system for reducing the recycle gas volume in an aromatics conversion reaction process as shown in Figure 1 and including the following steps:

[0100] Aromatics (toluene, purity greater than 99%) are mixed with a recycle gas containing 99 mol% hydrogen, and the molar ratio of hydrogen to hydrocarbons after mixing is 1.2. After being heated to 420 °C, it is sent to an aromatics conversion reactor for the disproportionation reaction. The reaction pressure is 2.5 MPaG, and the mass space velocity is 4.0 h -1 . The catalyst filled in the reactor is prepared according to Example 1 of the authorized patent ZL201310129905.4 (CN104107714A). After the reaction product is cooled to 40 °C, it is sent to a gas-liquid separator. After the gas-liquid separator, the hydrogen content in the gas-phase product is 37 wt%, and all the gas-phase products are sent to a PSA hydrogen production device. The volume ratio of the gas-phase product to the supplemented hydrogen is 25.0. The liquid-phase product in the gas-liquid separator is sent to a distillation separation system. The recycle gas volume and the supplemented hydrogen amount in the reaction system are shown in Table 1.

[0101] Comparative Example 1

[0102] Aromatics (by weight, containing 80% C 9 aromatics and 20% C 1020% of the aromatic hydrocarbons is mixed with the recycle gas containing 77 mol% of hydrogen, and the molar ratio of hydrogen to hydrocarbon after mixing is 5.5. After being heated to 540 °C, it is sent to the aromatic hydrocarbon conversion reactor for the hydrodealkylation reaction to produce benzene. The reaction pressure is 5.8 MPaG, and the mass space velocity is 1.5 h -1 The catalyst filled in the aromatic hydrocarbon hydrodealkylation reactor is prepared according to Example 4 of the authorized patent ZL201210412569.X (CN103772123A). The reaction product is sent to the gas-liquid separator after cooling. After the gas-liquid separator, 50% by volume of the gas-phase product is directly sent to the recycle hydrogen compressor. After being pressurized, it is mixed with the make-up hydrogen and used as the recycle gas to continue participating in the reaction (so that the hydrogen content of the recycle gas is 77 mol%). The remaining gas-phase product is taken out of the system, and the liquid-phase product in the gas-liquid separator is sent to the distillation separation system. The recycle gas volume and make-up hydrogen volume in the reaction system are shown in Table 1.

[0103] Comparative Example 1 of the present invention is compared with Example 2. Except for the different post-treatments of the gas-phase product, there are also differences in reaction conditions such as the hydrogen-hydrocarbon molar ratio and reaction pressure. The above differences are set to achieve the same reaction effect.

[0104] Comparative Example 2

[0105] The aromatic hydrocarbons (toluene, purity greater than 99%) are mixed with the recycle gas containing 75 mol% of hydrogen, and the molar ratio of hydrogen to hydrocarbon after mixing is 1.5. After being heated to 420 °C, it is sent to the aromatic hydrocarbon conversion reactor for the disproportionation reaction. The reaction pressure is 3.0 MPaG, and the mass space velocity is 4.0 h -1 The catalyst filled in the reactor is prepared according to Example 1 of the authorized patent ZL201310129905.4 (CN104107714A). The reaction product is sent to the gas-liquid separator after cooling. After the gas-liquid separator, 50% by volume of the gas-phase product is directly sent to the recycle hydrogen compressor. After being pressurized, it is mixed with the make-up hydrogen and used as the recycle gas to continue participating in the reaction (so that the hydrogen content of the recycle gas is 75 mol%). The remaining gas-phase product is taken out of the system, and the liquid-phase product in the gas-liquid separator is sent to the distillation separation system. The recycle gas volume and make-up hydrogen volume in the reaction system are shown in Table 1.

[0106] Comparative Example 2 of the present invention is compared with Example 3. Except for the different post-treatments of the gas-phase product, there are also differences in reaction conditions such as the hydrogen-hydrocarbon molar ratio and reaction pressure. The above differences are set to achieve the same reaction effect.

[0107] Example 4

[0108] A method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process, using the system for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process as shown in Figure 1 The system includes the following steps:

[0109] An aromatic hydrocarbon (containing 63% toluene and 37% C 9 + aromatic hydrocarbon by weight) is mixed with a recycle gas containing 99 mol% hydrogen, and the molar ratio of hydrogen to hydrocarbon after mixing is 1.5. After being heated to 350 °C, it is sent to an aromatic hydrocarbon conversion reactor for disproportionation and transalkylation reactions. The reaction pressure is 3.5 MPaG, and the mass space velocity is 3.0 h -1 . The catalyst filled in the disproportionation and transalkylation reactor is prepared according to Example 1 of the authorized patent ZL201110369964.X (CN103121915A). The reaction product is cooled to 40 °C and then sent to a gas-liquid separator. After the gas-liquid separator, the hydrogen content in the gas-phase product is 18 wt%; all the gas-phase products are sent to a PSA hydrogen production unit, and the volume ratio of the gas-phase product to the supplemented hydrogen is 10.0. The liquid-phase product in the gas-liquid separator is sent to a distillation separation system. The recycle gas volume and the supplemented hydrogen volume in the reaction system are shown in Table 1.

[0110] Example 5

[0111] An aromatic hydrocarbon (containing 70% toluene and 30% C 9 + aromatic hydrocarbon by weight) is mixed with a recycle gas containing 99 mol% hydrogen, and the molar ratio of hydrogen to hydrocarbon after mixing is 1.2. After being heated to 300 °C, it is sent to an aromatic hydrocarbon conversion reactor for disproportionation and transalkylation reactions. The reaction pressure is 2.5 MPaG, and the mass space velocity is 3.0 h -1 . The catalyst filled in the reactor is prepared according to Example 1 of the authorized patent ZL201110369964.X (CN103121915A). The reaction product is cooled to 40 °C and then sent to a gas-liquid separator. After the gas-liquid separator, the hydrogen content in the gas-phase product is 18 wt%. All the gas-phase products are sent to a PSA hydrogen production unit, and the volume ratio of the gas-phase product to the supplemented hydrogen is 12.0. The liquid-phase product in the gas-liquid separator is sent to a distillation separation system. The recycle gas volume and the supplemented hydrogen volume in the reaction system are shown in Table 1.

[0112] Example 6

[0113] An aromatic hydrocarbon (containing 80% C 9 aromatic hydrocarbon and 20% C 10 aromatic hydrocarbon by weight) is mixed with a recycle gas containing 99 mol% hydrogen, and the molar ratio of hydrogen to hydrocarbon after mixing is 4.0. After being heated to 600 °C, it is sent to an aromatic hydrocarbon conversion reactor for hydrodealkylation to produce benzene reaction. The reaction pressure is 5.5 MPaG, and the mass space velocity is 1.0 h -1。The catalyst filled in the reactor is prepared according to Example 4 of the authorized patent ZL201210412569.X (CN103772123A). The reaction product is cooled to 40°C and then sent to a gas-liquid separator. After the gas-liquid separator, the hydrogen content in the gas-phase product is 12 wt%, and all the gas-phase product is sent to a PSA hydrogen production unit. The volume ratio of the gas-phase product to the supplemented hydrogen is 5.0, and the liquid-phase product is sent to a distillation separation system. The circulating gas volume and the supplemented hydrogen volume in the reaction system are shown in Table 1.

[0114] Table 1

[0115]

[0116] As can be seen from Table 1, when the method of the present invention is adopted, under the condition that the aromatic hydrocarbon feed amount in the reactor remains the same, the circulating gas volume and the supplemented hydrogen volume in the reaction unit are significantly reduced. Furthermore, it can be shown that the method of the present invention can also effectively reduce the energy consumption in the reaction system, especially the energy consumption of the compressor that provides power for the circulating gas.

[0117] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. However, these descriptions should not be construed as limitations on the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0118] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0119] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art" or their similar terms to derive materials, substances, methods, steps, devices or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become commonly recognized in the art as suitable for similar purposes.

[0120] In the context of this specification, any matters or things not mentioned, except for the clearly stated content, directly apply to those known in the art without any change.

Claims

1. A method for reducing the recycle gas volume in an aromatics conversion reaction process, comprising the following steps: The aromatics conversion reaction includes hydroconversion and / or hydrogenation reactions; separating the products after the aromatics conversion reaction to obtain a liquid-phase product and a gas-phase product; supplementing hydrogen into the gas-phase product, and then performing hydrogen purification treatment to obtain methane-rich gas and purified hydrogen; Using the purified hydrogen as recycle gas in the aromatics conversion reaction.

2. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1, characterized in that it comprises the following steps: (a) Reacting an aromatic hydrocarbon with recycle gas under the action of a catalyst to generate reaction products; (b) After cooling the reaction products, performing gas-liquid separation to obtain a liquid-phase product and a gas-phase product; (c) Supplementing hydrogen into the gas-phase product, and then performing hydrogen purification treatment to obtain methane-rich gas and purified hydrogen; Using the purified hydrogen as recycle gas in the aromatics conversion reaction; (d) Optionally, the liquid-phase product enters a distillation separation system, and light alkanes and light aromatics are sequentially separated, and the remaining heavy components are recycled to step (a) to continue participating in the aromatics conversion reaction.

3. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, characterized in that: Step (a), The aromatic hydrocarbon is at least one selected from aromatic hydrocarbons having 7 or more carbon atoms; preferably, the aromatic hydrocarbon is selected from at least one of aromatic hydrocarbons having 7 ~ 12 carbon atoms; more preferably, the aromatic hydrocarbon is selected from at least one of toluene and heavy aromatic hydrocarbons having 9 ~ 12 carbon atoms; More preferably, the aromatic hydrocarbon contains toluene and heavy aromatic hydrocarbons of C 9 ~C 12 ; Even more preferably, the mass content of the heavy aromatic hydrocarbons of C 9 ~C 12 in the aromatic hydrocarbon is 0 to 70%.

4. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, characterized in that: Step (a), the hydrogen content in the recycle gas is 90.0 - 99.9 mol%, preferably 99.0 - 99.9 mol%.

5. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, characterized in that: Step (a), during the aromatics conversion reaction, The mass space velocity of the reaction raw materials is 0.5 to 5.5 h -1 ; preferably 1.0 to 3.0 h -1 ; and / or, the hydrogen-hydrocarbon molar ratio is 1.0 - 6.0; preferably 2.0 - 4.

0.

6. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, characterized in that: Step (a), during the aromatics conversion reaction, the reaction temperature is 200 - 750 °C, preferably 300 - 600 °C; and / or, the reaction pressure is 2.0 MPaG - 7.0 MPaG, preferably 2.5 MPaG - 5.5 MPaG; and / or, the aromatics conversion reaction is an aromatics hydrodealkylation reaction, a disproportionation and transalkylation reaction or a pure toluene disproportionation reaction.

7. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, characterized in that: Step (b), The gaseous product contains hydrogen, C 1 ~C 6 alkanes and benzene; preferably, the content of hydrogen in the gaseous product is 10 to 50 wt%; more preferably 15 to 45 wt%; more preferably, when the aromatics conversion reaction is an aromatics hydrodealkylation reaction, the hydrogen content in the gas-phase product is 10 - 20 wt%; preferably 12 - 18 wt%; and / or, when the aromatics conversion reaction is a disproportionation and transalkylation reaction, the hydrogen content in the gas-phase product is 10 - 20 wt%; preferably 12 - 18 wt%; and / or, when the aromatics conversion reaction is a pure toluene disproportionation reaction, the hydrogen content in the gas-phase product is 30 - 50 wt%; preferably 35 - 45 wt%.

8. The method for reducing the recycle gas volume in an aromatics conversion reaction process according to claim 1 or 2, It is characterized in that: Step (c), The volume ratio of the gaseous product to the supplemented hydrogen is 2.0 to 30.0; preferably, When the aromatic hydrocarbon conversion reaction is an aromatic hydrocarbon hydrodealkylation reaction, the volume ratio of the gaseous product to the supplemented hydrogen is 2.0 to 6.0, preferably 3.0 to 5.0; and / or, When the aromatic hydrocarbon conversion reaction is a disproportionation and transalkylation reaction, the volume ratio of the gaseous product to the supplemented hydrogen is 5.0 to 15.0, preferably 8.0 to 12.0; and / or, When the aromatic hydrocarbon conversion reaction is a pure toluene disproportionation reaction, the volume ratio of the gaseous product to the supplemented hydrogen is 20.0 to 30.0, preferably 22.0 to 28.

0.

9. The method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process according to claim 1 or 2, It is characterized in that: The hydrogen purification treatment method is one or more of PSA hydrogen production, chemical adsorption or membrane separation, preferably PSA hydrogen production.

10. A system for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process, comprising an aromatic hydrocarbon conversion reactor, a reaction product cooler, a gas-liquid separator, a hydrogen purification device and optionally a compressor; The outlet of the aromatic hydrocarbon conversion reactor is successively connected to the reaction product cooler and the gas-liquid separator; the gas-phase outlet of the gas-liquid separator is connected to the inlet of the hydrogen purification device; a supplementary hydrogen feed pipeline and a rich methane gas discharge pipeline are also provided on the hydrogen purification device; the hydrogen purified by the hydrogen purification device is discharged from the recycle gas outlet, and the recycle gas outlet is connected to the inlet of the aromatic hydrocarbon conversion reactor or the recycle gas outlet is connected to the inlet of the compressor, and the outlet of the compressor is connected to the inlet of the aromatic hydrocarbon conversion reactor; the inlet of the aromatic hydrocarbon conversion reactor is also connected to an aromatic hydrocarbon feed pipeline; Preferably, the method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process described in any one of claims 1-9 is adopted for the system.

11. The system for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process according to claim 10, It is characterized in that: The system further includes a feed pump, and the feed pump is connected to the inlet of the aromatic hydrocarbon conversion reactor through the aromatic hydrocarbon feed pipeline; and / or, The system further includes a rectification separation device, and the liquid-phase product outlet of the gas-liquid separator is connected to the inlet of the rectification separation device; and / or, The reaction product cooler is a heat exchanger; and / or, The number of aromatic hydrocarbon conversion reactors is one or more, preferably 2 to 4, and the aromatic hydrocarbon conversion reactors are connected in series; and / or, The hydrogen purification device is one or more of a PSA hydrogen production device, a chemical adsorption hydrogen purification device or a membrane separation hydrogen purification device.

12. An application of a method for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process described in any one of claims 1-9 or a system for reducing the recycle gas volume in the aromatic hydrocarbon conversion reaction process described in any one of claims 10-11 in the production process of aromatic hydrocarbon conversion reaction.

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