Combined method and system for aromatic hydrocarbon conversion

Abstract

The invention relates to the technical field of aromatic hydrocarbon conversion, and discloses a combined method and system for aromatic hydrocarbon conversion, and the method comprises the following steps: respectively feeding C7, C9 and above aromatic hydrocarbons from an upstream device into a catalytic transalkylation unit and a catalytic hydrodealkylation unit for separate treatment; efficient production of benzene, adjustable mixed xylene yield and production of C2-C5 light hydrocarbons with higher value are realized by adjusting the amount of materials entering the two combined systems. The system comprises a catalytic transalkylation unit, a catalytic hydrodealkylation unit and a product separation system. According to the method disclosed by the invention, the high product quality of the benzene product and the xylene product is ensured on the premise of fully producing the benzene product.

Description

Technical Field

[0001] The present invention relates to the technical field of aromatic hydrocarbon conversion, and more particularly to a combined method and system for aromatic hydrocarbon conversion. Background Art

[0002] Benzene is an important bulk basic organic raw material with a rich industrial chain and dispersed industrial bases. Its main downstream products include ethylbenzene (41.0%), phenol (16%), caprolactam (16%), cyclohexane (12%), etc. In 2020, the world's pure benzene production capacity is about 69.45 million tons / a and the output is about 48.75 million tons / a. It is expected that the world's pure benzene production capacity will reach 73.87 million tons / a in 2022, and the pure benzene demand will reach 52.78 million tons / a.

[0003] The coal chemical industry has high carbon emissions, and the call for "carbon neutrality" is becoming increasingly strong. In the future, the benzene production of the coking industry may be compressed. In addition, toluene disproportionation technology is currently the most widely used technology for aromatic conversion, but toluene disproportionation technology can only theoretically achieve 2 moles of toluene to increase the production of 1 mole of benzene and 1 mole of xylene. The raw materials are limited and the efficiency of aromatic conversion cannot be maximized. The existing heavy aromatic lightweight technology is only efficient in removing C2+ side chains, and it is impossible to achieve efficient removal of methyl groups. The product is mainly xylene, and the benzene production is limited. Aromatic dealkylation benzene production technology is to effectively remove side chain alkyl groups including methyl groups and above through side chain dealkylation technology, and efficiently convert aromatics into benzene. In theory, 1 mole of aromatics can produce 1 mole of benzene, which is the most efficient benzene production technology at present. Aromatic dealkylation includes hydrogenation dealkylation, non-hydrogenation dealkylation, steam reforming dealkylation, and transalkylation dealkylation (e.g. CN102190553A). The hydrodealkylation process includes thermal hydrodealkylation and catalytic hydrodealkylation. Catalytic hydrodealkylation has the characteristics of high reaction efficiency, low hydrogen consumption, high conversion rate, good selectivity, low operating temperature and high liquid yield. Since the application of catalytic hydrodealkylation technology in the 1960s, several production processes have been developed successively. The technology market is mainly concentrated in several major foreign oil companies, such as UOP's Hydeal process, Hoadley Process's Detol process, Pyrotol process and Litol process. The reactors of these processes are mostly fixed bed reactors. The focus of aromatic catalytic hydrodealkylation technology is mainly on the improvement of catalysts and the development of new catalysts. Although it can maximize the production of benzene, the gas phase product is mainly low-value methane, the reaction chemical hydrogen consumption is large, and it is impossible to take into account the production of mixed xylenes. The product plan of the device is single and the economic efficiency is poor. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides a combined method for aromatic hydrocarbon conversion, wherein a catalytic transalkylation unit and a catalytic hydrodealkylation unit are used to process C7 aromatic hydrocarbons and C9 and above aromatic hydrocarbons respectively, thereby obtaining a high-yield and high-purity benzene product. In addition, the present invention can flexibly adjust the benzene production as required on the basis of increasing the benzene production, thereby obtaining a high-yield xylene product. In the case of obtaining xylene products and benzene products at the same time, the present invention significantly retains the long-chain alkane gas phase product, reduces the generation of methane, and has strong economic efficiency.

[0005] A first aspect of the present invention is to provide an integrated process for aromatic hydrocarbon conversion, the process comprising the following steps:

[0006] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0007] In the presence of hydrogen, a raw material for a hydrodealkylation reaction from an upstream is contacted with a dealkylation catalyst to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0008] (b) separating the transalkylation reaction product and / or the hydrodealkylation reaction product obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0009] (c) separating the first liquid phase material obtained in step (b) to obtain a tower top material containing C7 aromatics and a second liquid phase material;

[0010] (d) at least part of the overhead material containing C7 aromatics is transported to step (a) for hydrodealkylation, and the rest of the overhead material containing C7 aromatics is transported to step (a) for transalkylation;

[0011] (e) separating the second liquid phase stream obtained in step (c) to obtain a tower top material containing xylene and a third liquid phase material;

[0012] (f) separating the third liquid phase material from fresh C9 or higher aromatic hydrocarbon material from the outside to obtain a tower top material containing C9 or higher aromatic hydrocarbons and a fourth liquid phase material, wherein at least a portion of the tower top material containing C9 or higher aromatic hydrocarbons is transported to step (a) for transalkylation reaction, and the rest of the tower top material containing C9 or higher aromatic hydrocarbons is transported to step (a) for hydrodealkylation reaction;

[0013] The raw materials of the combined method also include fresh materials containing C7 aromatics from the outside, and the fresh materials containing C7 aromatics are used as feed raw materials for one or more steps of the separation in step (b), the separation in step (c), the hydrodealkylation reaction in step (a), and the transalkylation reaction in step (a).

[0014] Through research, the inventors of the present invention unexpectedly found that, compared with the method of using a single transalkylation reaction to treat fresh materials containing C7 aromatics and fresh materials containing C9 and above aromatics, the combined method of aromatic conversion in the present invention has a higher benzene product yield, a lower content of methane in non-aromatics, and less heavy aromatics bottom liquid. Compared with the method of using a single hydrodealkylation reaction to treat fresh materials containing C7 aromatics and fresh materials containing C9 and above aromatics, the combined method of aromatic conversion in the present invention has a lower content of methane in non-aromatics, can also obtain xylene products with high added value, and has less heavy aromatics bottom liquid. In general, the combined method of aromatic conversion of the present invention obtains a high-yield benzene product. At the same time, the present invention can flexibly adjust the benzene yield as needed on the basis of increasing the benzene yield to obtain a high-yield xylene product. In the case of obtaining xylene products and benzene products at the same time, the present invention significantly retains the long-chain alkane gas phase product and reduces methane generation.

[0015] In summary, the present invention allows C7, C9 and above aromatics from upstream devices to enter the catalytic transalkylation unit and the catalytic hydrodealkylation unit for separate treatment, preferably by adjusting the amount of materials entering the two combined systems to achieve efficient production of benzene, adjustable mixed xylene production and production of more valuable C2-C5 light hydrocarbons. In addition, the method of the present invention ensures high product quality of benzene products and xylene products under the premise of fully producing benzene products.

[0016] In addition, the xylene tower of this process can be equipped with a side line extraction port to extract part of the mixture of C8 and above aromatics and send it directly to the dealkylation unit to reduce the operating energy consumption of the xylene tower and heavy aromatics tower. In addition, it can be considered to send the separated stream from the toluene tower kettle and / or the xylene tower kettle directly to the dealkylation unit, which can also be used as a measure to optimize the energy consumption of this process.

[0017] According to the present invention, the composition of the raw material for the transalkylation reaction in step (a) can be selected within a wide range. In a preferred embodiment of the present invention, the sulfur content in the raw material for the transalkylation reaction in step (a) is less than 200 ppmwt, and the bromine index is less than 5000 mgBr / 100g; more preferably,

[0018] The raw material used for the transalkylation reaction contains at least one of olefin components with a carbon content of 7 or more, alkanes with a carbon content of 7, alkanes with a carbon content of 9, cycloalkanes with a carbon content of 9, cumene, methylethylbenzene, trimethylbenzene, indane, and heavy aromatic hydrocarbons with a carbon content of 10 or more;

[0019] Further more preferably, the raw material for the transalkylation reaction contains, in mass percentage, 0.01%-10% alkanes, 20%-70% toluene, 15%-79.9% C9 aromatics, and 0%-30% C10 and above aromatics.

[0020] According to the present invention, the composition of the raw material used for the hydrodealkylation reaction in step (a) can be selected within a wide range. In a preferred embodiment of the present invention, the sulfur content in the raw material used for the hydrodealkylation reaction in step (a) is less than 200 ppmwt, and the bromine index is less than 5000 mgBr / 100g; more preferably,

[0021] The raw materials used for the hydrodealkylation reaction contain at least one of olefin components with a carbon content of 7 or more, carbon 7 alkanes, carbon 9 alkanes, carbon 9 cycloalkanes, isopropylbenzene, methylethylbenzene, trimethylbenzene, indane, and heavy aromatic hydrocarbons with a carbon content of 10 or more;

[0022] Further more preferably, the raw material for the hydrodealkylation reaction contains, in mass percentage, 0.01%-7% alkanes, 20%-99.9% toluene, 0.01%-60% xylene, 0.01%-79.9% C9 aromatics, and 0%-20% C10 and above heavy aromatics.

[0023] According to the present invention, the transalkylation catalyst can be selected in a wide range. In a preferred embodiment of the present invention, the transalkylation catalyst contains at least one of β zeolite, mordenite, ZSM-5 molecular sieve, MCM-22 molecular sieve, bismuth metal and / or bismuth oxide; preferably,

[0024] The total amount of bismuth metal and / or bismuth oxide is 0.005-5wt% of the transalkylation catalyst, based on the weight of bismuth metal element, such as 0.005, 0.01, 0.015, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5wt%, and any two values ​​or any interval between any two values; more preferably,

[0025] The transalkylation catalyst further contains at least one of the following metals and / or metal oxides: rhenium and molybdenum. The content of rhenium and / or palladium can be selected in a wide range. Preferably, based on the weight content of the metal elements corresponding to the two elements of rhenium and / or molybdenum, the rhenium content in the transalkylation catalyst is 0.1-0.8wt%, such as 0.1, 0.3, 0.5, 0.8wt%, and any two values ​​or any interval between any two values, and / or the molybdenum content is 0.2-1.5wt%, such as 0.2, 0.5, 0.8, 1, 1.3, 1.5wt%, and any two values ​​or any interval between any two values.

[0026] According to the present invention, the dealkylation catalyst can be selected in a wide range. In a preferred embodiment of the present invention, the dealkylation catalyst contains at least one of the following metals and / or their oxides: platinum, molybdenum, magnesium, chromium, nickel; preferably, based on the weight of the metal element, the total amount of the metal and its oxide accounts for 0.001-20wt% of the dealkylation catalyst, such as 0.001wt%, 0.003wt%, 0.005wt%, 0.1wt%, 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, and any two values ​​or any interval between any two values.

[0027] According to the present invention, the conditions for the transalkylation reaction can be selected within a wide range. In a preferred embodiment of the present invention, the conditions for the transalkylation reaction include:

[0028] The reaction temperature is 300-490°C; and / or, the pressure is 2-4 MPaG; and / or, the hydrogen-to-hydrocarbon ratio is 0.5-4 mol / mol, and / or, the weight space velocity is 1-5 h -1 .

[0029] According to the present invention, the conditions for the hydrodealkylation reaction can be selected within a wide range. In a preferred embodiment of the present invention, the conditions for the hydrodealkylation reaction include:

[0030] Temperature 400-700°C; and / or, pressure 2-6 MPaG; and / or, hydrogen-to-hydrocarbon ratio 2-8 mol / mol; and / or, weight space velocity 0.3-3 h -1 .

[0031] According to the present invention, the toluene tower overhead stream (i.e., the tower overhead material containing C7 aromatics) sent to the catalytic hydrodealkylation unit accounts for 0-100% of the toluene tower overhead production stream, and is not 0. The heavy aromatics tower overhead stream sent to the catalytic hydrodealkylation unit accounts for 0-100% of the heavy aromatics tower overhead production stream, and is not 100wt%. Part of the xylene tower overhead product can also be sent to the catalytic hydrodealkylation unit, and the xylene tower overhead stream sent to the catalytic hydrodealkylation unit accounts for 0-100% of the xylene tower overhead production stream. The following is a detailed description:

[0032] According to the present invention, the proportion of the overhead material containing C7 aromatics flowing to the hydrodealkylation reaction stage in step (d) to the total amount of the overhead material containing C7 aromatics obtained in step (c) can be selected in a wide range, for example, it can be 0-100wt% and not 0. In a preferred embodiment of the present invention, the overhead material containing C7 aromatics flowing to the hydrodealkylation reaction stage accounts for 0-100wt% of the total amount of the overhead material containing C7 aromatics obtained in step (c) and is not 0, preferably 50-100wt%, more preferably 70-100wt%. In this preferred embodiment, the content of benzene product, xylene product and long-chain alkane gas phase product is more flexible and adjustable, and the content of methane is lower in the process.

[0033] According to the present invention, the proportion of the overhead material containing carbon nine or more aromatics flowing to the hydrodealkylation reaction stage in step (f) to the total amount of the overhead material containing carbon nine or more aromatics obtained in step (f) can be selected in a wide range. In a preferred embodiment of the present invention, the overhead material containing carbon nine or more aromatics flowing to the hydrodealkylation reaction stage accounts for 0-100wt% and not 100wt% of the total amount of the overhead material containing carbon nine or more aromatics obtained in step (f), preferably 0-70wt%, more preferably 0-50wt%. In this preferred embodiment, the content of the benzene product, the xylene product and the long-chain alkane gas phase product is more flexible and adjustable, and the content of methane is lower in the process.

[0034] The present invention can produce a high-purity benzene product and significantly increase the benzene yield. In addition, on the basis of increasing the benzene yield, the present invention can also flexibly adjust the benzene yield as needed to obtain a high-yield xylene product. For example, in the above-mentioned preferred technical scheme, the present invention can achieve an increase in benzene production by adjusting the proportion of materials flowing to the hydrodealkylation reaction stage, or obtain a suitable xylene product while increasing the benzene production. In a preferred embodiment of the present invention, in order to further increase the yield of the benzene product, preferably, the top material containing xylene obtained in part of step (e) flows to the hydrodealkylation reaction stage. In this way, the benzene product can be further increased by controlling the output of xylene.

[0035] Preferably, the xylene-containing overhead material flowing to the hydrodealkylation reaction stage accounts for 0-100wt%, preferably 10-60wt%, and more preferably 20-40wt% of the total amount of the xylene-containing overhead material obtained in step (e). The xylene can be transported from the top of the xylene tower to the hydrodealkylation reaction unit, or by adjusting the xylene content in the xylene tower kettle, the xylene tower is transported to the downstream heavy aromatics tower, and then transported to the hydrodealkylation reaction stage through the top of the heavy aromatics tower.

[0036] According to the present invention, the fresh material containing C7 aromatics is used as a feed material for one or more steps of the separation in step (b), the separation in step (c), the hydrodealkylation reaction in step (a), and the transalkylation reaction in step (a). In a preferred embodiment of the present invention, in order to further improve the purity of the benzene product / xylene product while increasing the benzene yield, preferably,

[0037] When the fresh material containing C7 aromatics comes from the top of the toluene tower of the extraction device and has a bromine index of ≥2000 mgBr / 100 g, the fresh material containing C7 aromatics is used as the separation raw material of step (b);

[0038] When the fresh material containing C7 aromatics comes from the top of the toluene tower of the extraction device and the bromine index is less than 2000 mgBr / 100g, the fresh material containing C7 aromatics is used as a feed raw material for hydrodealkylation reaction and / or transalkylation reaction;

[0039] When the fresh material containing C7 aromatics comes from an extraction device and has not been subjected to fractionation treatment, the fresh material containing C7 aromatics is used as the separation raw material of step (b);

[0040] When the fresh material containing C7 aromatics has not been treated by an extraction device, the fresh material containing C7 aromatics is used as a feed raw material for one or more steps of the separation in step (b), the separation in step (c), the hydrodealkylation reaction in step (a), and the transalkylation reaction in step (a).

[0041] According to the present invention, the xylene product is a mixture of ethylbenzene, o-xylene, m-xylene and p-xylene.

[0042] According to the present invention, the mixed material obtained in the hydrodealkylation reaction stage and the transalkylation reaction stage further includes a light removal treatment step, which is preferably carried out in a light removal tower (i.e., a stripping tower). The specific light removal conditions are conventionally selected in the art and are not described in detail herein. That is, through the above steps, the transalkylation reaction product and the hydrodealkylation reaction product are first separated in the stripping tower to obtain a tower top material containing C1-C5 alkanes and a stripping tower bottom material, and then the stripping tower bottom material is separated in step (b).

[0043] According to the present invention, the step of deolefination of the mixed material obtained in the hydrodealkylation reaction stage and the transalkylation reaction stage is also included, preferably in a container filled with clay. The specific deolefination conditions are conventionally selected in the art and will not be described in detail here.

[0044] According to the present invention, the combined method for aromatic conversion includes two raw materials, namely, fresh material containing C7 aromatics from outside and fresh C9 and above aromatics from outside. The present invention has no special restrictions on the ratio of these two materials.

[0045] In the present invention, the purity of hydrogen obtained in the transalkylation reaction stage is 60-99 mol%, and / or the purity of hydrogen obtained in the hydrodealkylation reaction is 60-99 mol%.

[0046] In the present invention, the purity of the benzene product is ≥99.9%wt, and / or the purity of the xylene product is ≥95%wt.

[0047] The second aspect of the present invention is to provide a combined system for aromatics conversion, preferably the combined system for aromatics conversion is used for the combined method for aromatics conversion described in the first aspect; comprising: a hydrogen supply unit, an alkyl transfer reaction unit, a hydrodealkylation reaction unit, a fresh material supply unit containing C7 aromatics, a fresh C9 and above aromatic material supply unit, and a benzene fractionation tower, a toluene fractionation tower, a xylene fractionation tower and a heavy aromatic fractionation tower connected in sequence according to the flow direction of the liquid phase material;

[0048] The hydrogen supply unit, the heavy aromatic material outlet at the top of the heavy aromatic fractionation tower, the toluene material outlet at the top of the optional toluene fractionation tower, and the xylene material outlet at the top of the optional xylene fractionation tower are respectively connected to the inlet of the transalkylation reaction unit;

[0049] The hydrogen supply unit, the toluene material outlet at the top of the toluene fractionation tower, the heavy aromatic material outlet at the top of the optional heavy aromatic fractionation tower, and the xylene material outlet at the top of the optional xylene fractionation tower are respectively connected to the inlet of the hydrodealkylation reaction unit;

[0050] The material outlet of the transalkylation reaction unit and the material outlet of the transalkylation reaction unit can be respectively connected to the inlet of the benzene fractionation tower;

[0051] The fresh material supply unit containing C7 aromatics is connected to at least one of the following inlets: the inlet of the transalkylation reaction unit, the inlet of the hydrodealkylation reaction unit, the inlet of the benzene fractionation tower, and the inlet of the toluene fractionation tower;

[0052] The fresh C9 and above aromatic material supply unit is connected to the feed inlet of the heavy aromatic fractionation tower.

[0053] According to the present invention, the connection method of the benzene fractionation tower, the toluene fractionation tower, the xylene fractionation tower and the heavy aromatics fractionation tower is a conventional choice in the art. Specifically, in a preferred embodiment of the present invention, the bottom outlet of the benzene fractionation tower is connected to the inlet of the toluene fractionation tower, the bottom outlet of the toluene fractionation tower is connected to the inlet of the xylene fractionation tower, and the bottom outlet of the xylene fractionation tower is connected to the inlet of the heavy aromatics fractionation tower.

[0054] In a preferred embodiment of the present invention, the xylene material outlet at the top of the xylene fractionation tower can also be connected to the inlet of the hydrodealkylation reaction unit.

[0055] As mentioned above, preferably, the combined system for aromatic conversion also includes a stripping tower, the material outlet of the transalkylation reaction unit and the material outlet of the transalkylation reaction unit are respectively connected to the inlet of the stripping tower, and the bottom outlet of the stripping tower is connected to the inlet of the benzene fractionation tower.

[0056] For ease of understanding, as an example, in one embodiment of the present invention, C7, C9 and above aromatics and hydrogen from an upstream device enter a catalytic transalkylation unit together, non-aromatic cracking and transalkylation reactions occur, and a mixture containing benzene, toluene, C8 aromatics I, and C9 and above aromatics is produced;

[0057] In the presence of hydrogen, the raw materials for hydrodealkylation reaction (containing non-aromatic hydrocarbons, toluene, xylene, C10 aromatic hydrocarbons, etc.) from the upstream enter the catalytic dealkylation unit and contact with the dealkylation catalyst to undergo hydrodealkylation reaction to obtain a mixture of hydrodealkylation reaction products (the products after the reaction mainly contain benzene, toluene, and xylene);

[0058] The mixture of the two reactions enters the benzene tower for separation, and the benzene product is obtained at the top of the benzene tower. The bottom liquid of the benzene tower enters the toluene tower for separation. The toluene obtained at the top of the toluene tower is divided into two parts, one part is returned to the catalytic transalkylation unit, and the other part enters the catalytic dealkylation unit. The toluene bottom liquid obtained in the bottom of the tower enters the xylene tower for separation. The xylene obtained at the top of the xylene tower enters the separation unit (extraction), and the carbon nine and above components obtained in the bottom of the tower enter the heavy aromatics tower for separation. The carbon nine and above aromatics obtained at the top of the heavy aromatics tower are divided into two parts, one part is returned to the catalytic transalkylation unit, and the other part enters the catalytic dealkylation unit, and the carbon ten and above aromatics obtained in the bottom of the tower are sent out of the boundary.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention significantly increases the benzene yield by using a catalytic transalkylation unit and a catalytic hydrodealkylation unit to process C7 aromatics and C9 and above aromatics respectively. In addition, the present invention can flexibly adjust the benzene yield as needed to obtain a xylene product with an appropriate flow rate on the basis of increasing the benzene yield. When obtaining xylene products and benzene products at the same time, compared with the prior art of producing the same yield of xylene products, the present invention significantly retains long-chain alkanes and reduces the production of low-value methane.

[0061] More specifically, the advantages of the present invention are:

[0062] (1) The method of the present invention flexibly increases the production of benzene by flexibly allocating the amount of C7 aromatics and C9 and above aromatics to the catalytic transalkylation unit and the catalytic hydrodealkylation unit;

[0063] (2) The method of the present invention can obtain high-quality benzene products and xylene products;

[0064] (3) The storytelling method of the present invention can retain long-chain alkanes and reduce the production of low-value methane;

[0065] (4) The method of the present invention is simple to operate, easy to implement, and can be applied on a large scale in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 A process flow chart showing an integrated method for aromatic hydrocarbon conversion according to the present invention.

[0067] 1 is a catalytic transalkylation reactor, 2 is a transalkylation reaction product, 3 is a catalytic hydrogenation dealkylation reactor, 4 is a catalytic hydrogenation dealkylation reaction product, 5 is a benzene tower, 6 is a benzene product, 7 is a first liquid phase material, 8 is a toluene tower, 9 is a toluene tower top material containing toluene, 10 is a toluene tower top material sent to the catalytic transalkylation reactor, 11 is a toluene tower top material sent to the catalytic hydrogenation dealkylation reactor, 12 is a second liquid phase material, 13 is a xylene tower, 14 is a xylene product, 15 is a third liquid phase material, 16 is a heavy aromatics tower, 17 is a tower top material containing C9 and above aromatics, 18 is a tower top material containing C9 and above aromatics sent to the catalytic transalkylation reactor, 19 is a tower top material containing C9 and above aromatics sent to the catalytic hydrogenation dealkylation reactor, 20 is a fourth liquid phase material, 21 is supplementary hydrogen, 22 is supplementary hydrogen sent to the catalytic transalkylation unit, and 23 is supplementary hydrogen sent to the catalytic hydrogenation dealkylation unit. 24 is a fresh material containing C7 aromatics, 25 is a fresh C9 and above aromatic material from outside, and 26 is a xylene flow going to the dealkylation reaction.

[0068] A combined method and system for aromatics conversion, embodiments of the method and system include the following steps:

[0069] (a) in the presence of hydrogen, a raw material for transalkylation reaction from upstream (including at least one of the following: a toluene overhead material 10 sent to a catalytic transalkylation reactor, and a overhead material 18 containing aromatic hydrocarbons having carbon nine or more sent to a catalytic transalkylation reactor) is contacted with a transalkylation catalyst in a catalytic transalkylation reactor 1 to carry out a transalkylation reaction, thereby obtaining a transalkylation reaction product 2;

[0070] In the presence of hydrogen, the raw materials for the hydrodealkylation reaction from the upstream (including at least one of the following: the toluene top material 11 sent to the catalytic hydrodealkylation reactor, the top material 19 containing C9 and above aromatics sent to the catalytic hydrodealkylation reactor, and the xylene stream 26 sent to the dealkylation reaction) are contacted with the dealkylation catalyst in the catalytic hydrodealkylation reactor 3 to carry out the hydrodealkylation reaction, thereby obtaining the hydrodealkylation reaction product 4;

[0071] (b) separating the transalkylation reaction product 2 and the hydrodealkylation reaction product 4 obtained in step (a) in a benzene tower 5 to obtain a benzene product 6 and a first liquid phase material 7;

[0072] (c) separating the first liquid phase material 7 obtained in step (b) in a toluene tower 8 to obtain a toluene tower top material 9 containing toluene and a second liquid phase material 12, i.e., a toluene tower bottom liquid;

[0073] (d) the toluene overhead material 11 sent to the catalytic hydrodealkylation reactor is sent to the catalytic hydrodealkylation reactor 3 in step (a) for hydrodealkylation reaction, and the remaining toluene overhead material is sent to the catalytic transalkylation reactor 1 in step (a) for transalkylation reaction;

[0074] (e) separating the second liquid phase stream 12 obtained in step (c) in a xylene tower 13 to obtain a xylene product 14, a xylene stream 26 for dealkylation reaction, and a third liquid phase material 15, i.e., a xylene tower bottom liquid;

[0075] (f) separating the third liquid phase material 15 and / or fresh C9 and above aromatic hydrocarbon material 25 from outside in a heavy aromatic hydrocarbon tower 16 to obtain a tower top material 17 containing C9 and above aromatic hydrocarbons, i.e., a heavy aromatic hydrocarbon tower top material, and a fourth liquid phase material 20, i.e., a heavy aromatic hydrocarbon tower bottom liquid, wherein at least a portion of the tower top material 17 containing C9 and above aromatic hydrocarbons is transported to the catalytic hydrodealkylation reactor 3 of step (a) for transalkylation reaction, and the rest of the tower top material containing C9 and above aromatic hydrocarbons is transported to the catalytic transalkylation reactor 1 of step (a) for hydrodealkylation reaction;

[0076] The raw materials of the combined method also include fresh toluene material 24 from outside, and the fresh toluene material 24 is used as the feed raw material for one or more links in the benzene tower 5 in step (b), the toluene tower 8 in step (c), the catalytic hydrodealkylation reactor 3, and the catalytic transalkylation reactor 1. DETAILED DESCRIPTION

[0077] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0078] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0079] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0080] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0081] The method for determining the composition of the reaction raw materials and products of the present invention is gas chromatography.

[0082] In the following examples, all fresh C9 and above aromatic raw materials are the same.

[0083] In the embodiment of the present invention, the purity of the benzene product is ≥99.9%wt, and the purity of the xylene product is ≥95%wt.

[0084] [Example 1]

[0085] In this embodiment 1, 100 tons / hour of fresh C7 aromatics from the extraction device that have not been distilled enter the benzene tower in step (b) after passing through the stripping tower (i.e., fresh C7 aromatics are introduced into the combined system from here, and C1-C5 non-aromatics are obtained from the top of the stripping tower), and 100 tons / hour of fresh C9 and above aromatic raw materials enter the heavy aromatics tower, and after being mixed with the transalkylation reaction product and the dealkylation reaction product and separated by each distillation tower, the feed composition entering the transalkylation reaction and the feed composition entering the dealkylation reaction are as shown in Table 1. The combined method for aromatics conversion comprises the following steps:

[0086] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0087] In the presence of hydrogen, a raw material for a hydrodealkylation reaction from an upstream is contacted with a dealkylation catalyst to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0088] (b) separating the mixture of the two reactions obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0089] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a tower top material containing toluene and a second liquid phase material;

[0090] (d) 30 wt% of the toluene overhead material is returned to step (a) to contact with a dealkylation catalyst in the presence of hydrogen for a hydrogenation dealkylation reaction, and the remaining toluene-containing material is returned to step (a) for a transalkylation reaction;

[0091] (e) separating the second liquid phase stream obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material, and sending 40 wt % of the xylene material to a dealkylation reaction unit;

[0092] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, 60 wt% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) to contact with a dealkylation catalyst in the presence of hydrogen for a hydrogenation dealkylation reaction, and the rest of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for a transalkylation reaction.

[0093] The catalytic transalkylation unit uses a fixed bed reactor, and the reactor is filled with a binder-free ZSM-5 molecular sieve catalyst with a loading weight ratio of 0.13% Bi, 0.8% rhenium oxide and 0.2% molybdenum oxide. The catalytic hydrodealkylation unit uses a fixed bed reactor, and the reactor is filled with an oxide catalyst with a loading weight ratio of 0.001% magnesium, 20% molybdenum, and 5.5% nickel. The main operating conditions of each reaction unit are shown in Table 2. The product distribution obtained by Example 1 is shown in Table 3.

[0094] Table 1 Example 1 Reaction feed composition

[0095] Transalkylation feed Dealkylation feed Non-aromatic hydrocarbons, %wt 0.01 7.0 Toluene, %wt 70 50.0 Xylene, %wt - 10.0 C9 aromatics, %wt 15.0 20.0 C10 aromatics, %wt 14.99 13.0 Bromine index, mgBr / 100g 50 5000 Total sulfur content, ppmwt 1 200

[0096] Table 2 Process parameters of reaction unit in Example 1

[0097]

[0098]

[0099] Table 3 Product distribution of Example 1

[0100] Components Mass flow, tons / hour Benzene products 95.4 Mixed Xylene Products 50.3 Methane 20.4 C2-C5 non-aromatics 23.9 Heavy aromatics bottom liquid 10.0

[0101] [Example 2]

[0102] In this Example 2, 100 tons / hour of fresh C7 aromatics from the top of the toluene tower of the extraction unit enters the dealkylation reactor (i.e., the fresh C7 aromatics are introduced into the combined system from here), and 100 tons / hour of fresh C9 and above aromatic raw materials enter the heavy aromatics tower. After the fresh raw materials are mixed with the transalkylation reaction product and the dealkylation reaction product and separated in each distillation tower, the feed compositions entering the transalkylation reaction and the dealkylation reaction are as shown in Table 4.

[0103] Table 4 Example 2 Reaction feed composition

[0104]

[0105]

[0106] Table 5 Process parameters of reaction unit in Example 2

[0107] Transalkylation Dealkylation reaction Reaction temperature, °C 380 640 Reaction pressure, MPaG 2.0 2.0 Hydrogen to hydrocarbon ratio, mol / mol 4.0 2.0 <![CDATA[Weight hourly space velocity, h -1 > 5.0 0.3

[0108] The integrated process for aromatics conversion comprises the following steps:

[0109] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0110] In the presence of hydrogen, the raw material for hydrodealkylation reaction from upstream enters the dealkylation reactor to contact with the dealkylation catalyst to carry out hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0111] (b) separating the mixture of the two reactions obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0112] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a material containing toluene and a second liquid phase material;

[0113] (d) 70 wt% of the toluene overhead material is returned to step (a) for a hydrodealkylation reaction, and the remaining toluene-containing material is returned to step (a) for a transalkylation reaction;

[0114] (e) separating the second liquid phase stream obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material, wherein 22 wt % of the xylene material is sent to a dealkylation reaction unit;

[0115] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, 20% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for hydrodealkylation reaction, and the rest of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for transalkylation reaction.

[0116] The catalytic transalkylation unit uses a fixed bed reactor, and the reactor is filled with a binder-free β molecular sieve catalyst with a loading weight ratio of 5.0% Bi, 0.1% rhenium oxide and 1.5% molybdenum oxide. The catalytic hydrodealkylation unit uses a fixed bed reactor, and the reactor is filled with an oxide catalyst with a loading weight ratio of 0.001% platinum, 20% chromium, and 0.001% nickel. The main operating conditions of each reaction unit are detailed in Table 6.

[0117] The product distribution obtained by using Example 2 is shown in Table 6.

[0118] Table 6 Product distribution of Example 2

[0119] Components Mass flow, tons / hour Benzene products 71.4 Mixed Xylene Products 72.3 Methane 14.4 C2-C5 non-aromatic 31.9 Heavy aromatics bottom liquid 10.0

[0120] [Example 3]

[0121] In this Example 3, 30wt% of 100 tons / hour of fresh C7 aromatics that have not been treated by the extraction device enter the transalkylation reactor as the raw material for the transalkylation reaction, and 70wt% enter the hydrodealkylation reactor as the raw material for the hydrodealkylation reaction. 100 tons / hour of fresh C9 and above aromatic raw materials enter the heavy aromatics tower. After being mixed with the transalkylation reaction product and the dealkylation reaction product and separated by each distillation tower, the feed entering the transalkylation reaction and the feed entering the dealkylation reaction are composed as shown in Table 7.

[0122] Table 7 Example 3 Reaction feed composition

[0123] Transalkylation feed Dealkylation feed Non-aromatic hydrocarbons, %wt 6.0 0.01 Toluene, %wt 20.0 99.9 Xylene, %wt - 0.01 C9 aromatics, %wt 74.0 0.01 C10 aromatics, %wt 0.0 0.07 Bromine index, mgBr / 100g 50.0 0.0 Total sulfur content, ppm wt 1 200

[0124] Table 8 Process parameters of reaction unit in Example 3

[0125]

[0126]

[0127] The integrated process for aromatics conversion comprises the following steps:

[0128] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0129] In the presence of hydrogen, a raw material for a hydrodealkylation reaction from an upstream is contacted with a dealkylation catalyst to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0130] (b) separating the two reaction mixtures obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0131] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a material containing toluene and a second liquid phase material;

[0132] (d) 80 wt% of the toluene overhead material is returned to step (a) for a hydrodealkylation reaction, and the remaining toluene-containing material is returned to step (a) for a transalkylation reaction;

[0133] (e) separating the second liquid phase obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material, wherein the xylene-containing material is extracted from the top of the xylene tower, and the xylene material with 0 wt% is sent to a dealkylation reaction unit;

[0134] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, 0wt% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for hydrodealkylation reaction, and the rest of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for transalkylation reaction.

[0135] The catalytic transalkylation unit uses a fixed bed reactor, and the reactor is filled with a binder-free β molecular sieve catalyst with a loading weight ratio of 5.0% Bi, 0.1% rhenium oxide and 1.5% molybdenum oxide. The catalytic hydrodealkylation unit uses a fixed bed reactor, and the reactor is filled with an oxide catalyst with a loading weight ratio of 0.001% platinum, 20% chromium, and 0.001% nickel. The main operating conditions of each reaction unit are detailed in Table 9.

[0136] The product distribution obtained by using Example 3 is shown in Table 9.

[0137] Table 9 Product distribution of Example 3

[0138]

[0139]

[0140] [Example 4]

[0141] In this Example 4, 60wt% of 100 tons / hour of fresh C7 aromatics that have not been treated by the extraction device enter the transalkylation reactor as a raw material for the transalkylation reaction, and 40wt% enter the hydrodealkylation reactor as a raw material for the hydrodealkylation reaction. 100 tons / hour of fresh C9 and above aromatic raw materials enter the heavy aromatics tower. After being mixed with the transalkylation reaction product and the dealkylation reaction product and separated by each distillation tower, the feed entering the transalkylation reaction and the feed entering the dealkylation reaction are composed as shown in Table 10.

[0142] Table 10 Example 4 Reaction feed composition

[0143] Transalkylation feed Dealkylation feed Non-aromatic hydrocarbons, %wt 5.0 0.01 Toluene, %wt 30.0 20.0 Xylene, %wt - 0.01 C9 aromatics, %wt 35.0 60.0 C10 aromatics, %wt 30.0 19.98 Bromine index, mgBr / 100g 10 3000 Total sulfur content, ppm wt 100 10

[0144] Table 11 Process parameters of reaction unit in Example 4

[0145] Transalkylation Dealkylation reaction Reaction temperature, °C 400 400 Reaction pressure, MPaG 3.5 4.4 Hydrogen to hydrocarbon ratio, mol / mol 5.5 5.0 <![CDATA[Weight hourly space velocity, h -1 > 1.5 2.0

[0146] The integrated process for aromatics conversion comprises the following steps:

[0147] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0148] In the presence of hydrogen, a raw material for a hydrodealkylation reaction from an upstream is contacted with a dealkylation catalyst to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0149] (b) separating the two reaction mixtures obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0150] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a material containing toluene and a second liquid phase material;

[0151] (d) 20 wt% of the toluene overhead material is returned to step (a) for a hydrodealkylation reaction, and the remaining toluene-containing material is returned to step (a) for a transalkylation reaction;

[0152] (e) separating the second liquid phase stream obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material, wherein 0.5 wt % of the xylene material is sent to a dealkylation reaction unit;

[0153] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, 70 wt% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for hydrodealkylation reaction, and the rest of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for transalkylation reaction.

[0154] The catalytic transalkylation unit adopts a fixed bed reactor, and the reactor is filled with a binder-free MCM-22 and mordenite zeolite sieve catalyst with a loading weight ratio of 3.4% Bi, 0.5% rhenium oxide and 1.1% molybdenum oxide.

[0155] The catalytic hydrodealkylation unit uses a fixed bed reactor, and the reactor is filled with an oxide catalyst with a loading weight ratio of 0.016% molybdenum, 20% platinum, and 0.001% chromium. The main operating conditions of each reaction unit are shown in Table 11.

[0156] The product distribution obtained by using Example 4 is shown in Table 12.

[0157] Table 12 Product distribution of Example 4

[0158] Components Mass flow, tons / hour Benzene products 64.8 Mixed Xylene Products 82.9 Methane 16.2 C2-C5 non-aromatic 25.1 Heavy aromatics bottom liquid 11.0

[0159] [Comparative Example 1]

[0160] In this comparative example 1, only the transalkylation reaction was carried out without the hydrodealkylation reaction:

[0161] 100 tons / hour of fresh C7 aromatics from the extraction device that have not been distilled (same as in Example 1) enter the stripping tower and then enter the benzene tower in step (b) for separation, 100 tons / hour of fresh C9 and above aromatics (same as in Example 1) enter the heavy aromatics tower, after being mixed with the transalkylation reaction product and separated by each distillation tower, the C7 aromatics and C9 and above aromatics enter the transalkylation reaction to obtain the reaction products shown in Table 13. The following steps are included:

[0162] (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product;

[0163] (b) separating the reaction mixture obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0164] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a tower top material containing toluene and a second liquid phase material;

[0165] (d) 100 wt% of the toluene overhead material is returned to step (a) for transalkylation reaction;

[0166] (e) separating the second liquid phase stream obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material;

[0167] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, and 100 wt% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) for transalkylation reaction.

[0168] Except for the raw materials, the other experimental conditions were the same as the hydrodealkylation reaction conditions in Example 1.

[0169] Table 13 Product distribution of comparative example 1

[0170] Components Mass flow, tons / hour Benzene products 36.2 Mixed Xylene Products 110.4 Methane 18.1 C2-C5 non-aromatic 16.3 Heavy aromatics bottom liquid 19.0

[0171] [Comparative Example 2]

[0172] In this comparative example 2, only the hydrodealkylation reaction was carried out without the transalkylation reaction:

[0173] In this comparative example 2, 100 tons / hour of fresh C7 aromatics (same as in Example 1) from the extraction device without distillation treatment enters the stripping tower and then enters the benzene tower in step (b) for separation, and 100 tons / hour of fresh C9 and above aromatics enter the heavy aromatics tower, after being mixed with the transalkylation reaction product and separated by each distillation tower, the C7 aromatics and the C9 and above aromatics enter the transalkylation reaction to obtain the reaction products shown in Table 13. The following steps are included:

[0174] (a) contacting a feedstock for a hydrodealkylation reaction from an upstream with a dealkylation catalyst in the presence of hydrogen to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product;

[0175] (b) separating the reaction mixture obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material;

[0176] (c) separating the first liquid phase material obtained in step (b) in a toluene tower to obtain a tower top material containing toluene and a second liquid phase material;

[0177] (d) 100 wt% of the toluene top material is returned to step (a) to contact with a dealkylation catalyst in the presence of hydrogen to carry out a hydrodealkylation reaction;

[0178] (e) separating the second liquid phase stream obtained in step (c) in a xylene tower to obtain a xylene-containing material and a third liquid phase material;

[0179] (f) The third liquid phase material and fresh C9 and above aromatic hydrocarbon material from the outside are separated in a heavy aromatic hydrocarbon tower to obtain a tower top material containing C9 and above aromatic hydrocarbons and a fourth liquid phase material, and 100 wt% of the tower top material containing C9 and above aromatic hydrocarbons is returned to step (a) to contact with a dealkylation catalyst in the presence of hydrogen for a hydrogenation dealkylation reaction.

[0180] Except for the raw materials, the other experimental conditions were the same as the hydrodealkylation reaction conditions in Example 1.

[0181] Table 14 Product distribution of comparative example 2

[0182] Components Mass flow, tons / hour Benzene products 147.2 Mixed Xylene Products 0.0 Methane 32.9 C2-C5 non-aromatic 0.9 Heavy aromatics bottom liquid 19.0

[0183] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0184] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0185] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0186] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A combined process for the conversion of aromatic hydrocarbons, the process comprising the following steps: (a) contacting a raw material for a transalkylation reaction from an upstream with a transalkylation catalyst in the presence of hydrogen to carry out a transalkylation reaction to obtain a transalkylation reaction product; In the presence of hydrogen, a raw material for a hydrodealkylation reaction from an upstream is contacted with a dealkylation catalyst to carry out a hydrodealkylation reaction to obtain a hydrodealkylation reaction product; (b) separating the transalkylation reaction product and / or the hydrodealkylation reaction product obtained in step (a) in a benzene tower to obtain a benzene product and a first liquid phase material; (c) separating the first liquid phase material obtained in step (b) to obtain a tower top material containing C7 aromatics and a second liquid phase material; (d) at least part of the overhead material containing C7 aromatics is transported to step (a) for hydrodealkylation, and the rest of the overhead material containing C7 aromatics is transported to step (a) for transalkylation; (e) separating the second liquid phase stream obtained in step (c) to obtain a tower top material containing xylene and a third liquid phase material; (f) separating the third liquid phase material from fresh C9 or higher aromatic hydrocarbon material from the outside to obtain a tower top material containing C9 or higher aromatic hydrocarbons and a fourth liquid phase material, wherein at least a portion of the tower top material containing C9 or higher aromatic hydrocarbons is transported to step (a) for transalkylation reaction, and the rest of the tower top material containing C9 or higher aromatic hydrocarbons is transported to step (a) for hydrodealkylation reaction; The raw materials of the combined method also include fresh materials containing C7 aromatics from the outside, and the fresh materials containing C7 aromatics are used as feed raw materials for one or more steps of the separation in step (b), the separation in step (c), the hydrodealkylation reaction in step (a), and the transalkylation reaction in step (a).

2. The combined process for aromatics conversion according to claim 1, characterized in that: The sulfur content of the raw materials used for the transalkylation reaction in step (a) is less than 200 ppmwt, and the bromine index is less than 5000 mgBr / 100g; preferably, The raw material for the transalkylation reaction contains at least one of C7 and above olefin components, C7 alkanes, C9 alkanes, C9 cycloalkanes, cumene, methylethylbenzene, trimethylbenzene, indane, and C10 and above heavy aromatics; More preferably, the raw material for the transalkylation reaction contains, in mass percentage, 0.01%-10% alkanes, 20%-70% toluene, 15%-79.9% C9 aromatics, and 0%-30% C10 and above aromatics.

3. The combined process for aromatics conversion according to claim 1, characterized in that: The sulfur content of the feedstock used for the hydrodealkylation reaction in step (a) is less than 200 ppmwt, and the bromine index is less than 5000 mgBr / 100g; preferably, The raw material for the hydrodealkylation reaction contains at least one of C7 and above olefin components, C7 alkanes, C9 alkanes, C9 cycloalkanes, cumene, methylethylbenzene, trimethylbenzene, indane, and C10 and above heavy aromatics; More preferably, the raw material for the hydrodealkylation reaction contains, in percentage by mass, 0.01%-7% alkanes, 20%-99.9% toluene, 0.01%-60% xylene, 0.01%-79.9% C9 aromatics, and 0%-20% C10 and above heavy aromatics.

4. The combined process for aromatics conversion according to claim 1, characterized in that: The transalkylation catalyst contains at least one of beta zeolite, mordenite, ZSM-5 molecular sieve, MCM-22 molecular sieve, bismuth metal and / or bismuth oxide; preferably, The total amount of bismuth metal and / or bismuth oxide accounts for 0.005-5wt% of the transalkylation catalyst based on the weight of bismuth metal element; more preferably, The transalkylation catalyst further contains at least one of the following metals and / or metal oxides: rhenium and molybdenum.

5. The combined process for aromatics conversion according to claim 1, characterized in that: The dealkylation catalyst contains at least one of the following metals and / or their oxides: platinum, molybdenum, magnesium, chromium, nickel; preferably, based on the weight of the metal element, the total amount of the metal and its oxide accounts for 0.001-20wt% of the dealkylation catalyst.

6. The combined process for aromatics conversion according to claim 1, characterized in that: The conditions of the transalkylation reaction include: The reaction temperature is 300-490°C; and / or, the pressure is 2-4 MPaG; and / or, the hydrogen-to-hydrocarbon ratio is 0.5-4 mol / mol, and / or, the weight space velocity is 1-5 h -1 .

7. The combined process for aromatics conversion according to claim 1, characterized in that: The conditions of the hydrodealkylation reaction include: Temperature 400-700°C; and / or, pressure 2-6 MPaG; and / or, hydrogen-to-hydrocarbon ratio 2-8 mol / mol; and / or, weight space velocity 0.3-3 h -1 .

8. The combined process for aromatics conversion according to any one of claims 1 to 7, characterized in that: The top material containing C7 aromatics flowing to the hydrodealkylation reaction stage in step (d) accounts for 0-100wt% of the total amount of the top material containing C7 aromatics obtained in step (c), preferably 50-100wt%, more preferably 70-100wt%.

9. The combined process for aromatics conversion according to any one of claims 1 to 7, characterized in that: The top material containing C9 and above aromatic hydrocarbons flowing to the hydrodealkylation reaction stage in step (f) accounts for 0-100wt% and not 100wt% of the total amount of the top material containing C9 and above aromatic hydrocarbons obtained in step (f), preferably 0-70wt%, more preferably 0-50wt%.

10. The combined process for aromatics conversion according to any one of claims 1 to 7, characterized in that: The top material containing xylene obtained in part of step (e) flows to the hydrodealkylation reaction stage; preferably, The xylene-containing overhead material flowing to the hydrodealkylation reaction stage accounts for 0-100 wt %, preferably 10-60 wt %, more preferably 20-40 wt % of the total amount of xylene-containing overhead material obtained in step (e).

11. The combined process for aromatics conversion according to any one of claims 1 to 7, characterized in that: When the fresh material containing C7 aromatics comes from the top of the toluene tower of the extraction device and has a bromine index of ≥2000 mgBr / 100 g, the fresh material containing C7 aromatics is used as the separation raw material of step (b); When the fresh material containing C7 aromatics comes from the top of the toluene tower of the extraction device and the bromine index is less than 2000 mgBr / 100g, the fresh material containing C7 aromatics is used as a feed raw material for hydrodealkylation reaction and / or transalkylation reaction; When the fresh material containing C7 aromatics comes from an extraction device and has not been subjected to fractionation treatment, the fresh material containing C7 aromatics is used as the separation raw material of step (b); When the fresh material containing C7 aromatics has not been processed by the extraction device, the fresh material containing C7 aromatics is used as a feed raw material for one or more steps of the separation in step (b), the separation in step (c), the hydrodealkylation reaction in step (a), and the transalkylation reaction in step (a); and / or, The combined method further comprises separating the transalkylation reaction product and the hydrodealkylation reaction product in a stripping tower to obtain a tower top material containing C1-C5 alkanes and a stripping tower bottom material, and then separating the stripping tower bottom material in step (b).

12. An integrated system for aromatic hydrocarbon conversion, comprising a hydrogen supply unit, an alkyl transfer reaction unit, a hydrodealkylation reaction unit, a fresh material supply unit containing C7 aromatic hydrocarbons, a fresh material supply unit containing C9 and above aromatic hydrocarbons, and a benzene fractionation tower, a toluene fractionation tower, a xylene fractionation tower and a heavy aromatic hydrocarbon fractionation tower connected in sequence according to the flow direction of liquid phase materials; in, The hydrogen supply unit, the heavy aromatic material outlet at the top of the heavy aromatic fractionation tower, the toluene material outlet at the top of the optional toluene fractionation tower, and the xylene material outlet at the top of the optional xylene fractionation tower are respectively connected to the inlet of the transalkylation reaction unit; The hydrogen supply unit, the toluene material outlet at the top of the toluene fractionation tower, the heavy aromatic material outlet at the top of the optional heavy aromatic fractionation tower, and the xylene material outlet at the top of the optional xylene fractionation tower are respectively connected to the inlet of the hydrodealkylation reaction unit; The material outlet of the transalkylation reaction unit and the material outlet of the transalkylation reaction unit can be respectively connected to the inlet of the benzene fractionation tower; The fresh material supply unit containing C7 aromatics is connected to at least one of the following inlets: the inlet of the transalkylation reaction unit, the inlet of the hydrodealkylation reaction unit, the inlet of the benzene fractionation tower, and the inlet of the toluene fractionation tower; The fresh C9 and above aromatic material supply unit is connected to the feed inlet of the heavy aromatic fractionation tower.

13. The integrated system for aromatics conversion according to claim 11, characterized in that: The combined system for aromatic hydrocarbon conversion further comprises a stripping tower, wherein the material outlet of the transalkylation reaction unit and the material outlet of the transalkylation reaction unit are respectively connected to the inlet of the stripping tower, and the bottom outlet of the stripping tower is connected to the inlet of the benzene fractionation tower; and / or, The bottom outlet of the benzene fractionation tower is connected to the inlet of the toluene fractionation tower, the bottom outlet of the toluene fractionation tower is connected to the inlet of the xylene fractionation tower, and the bottom outlet of the xylene fractionation tower is connected to the inlet of the heavy aromatics fractionation tower; preferably, The xylene material outlet at the top of the xylene fractionation tower can also be communicated with the inlet of the hydrodealkylation reaction unit.

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