Production method of xylene

Abstract

The invention relates to the technical field of xylene preparation, and discloses a xylene production method, which comprises: (1) feeding an aromatic hydrocarbon raw material into a first stage moving bed reactor, and contacting the aromatic hydrocarbon raw material with a solid acid aromatic hydrocarbon methylation catalyst filled in the first stage moving bed reactor to carry out an alkylation reaction; dividing an alkylation reagent into n parts, and respectively feeding the n parts into the first-stage to nth-stage moving bed reactors; a reaction discharge material of the first-stage moving bed reactor is used as a reaction feed material of the second-stage moving bed reactor; a solid acid aromatic hydrocarbon methylation catalyst in the primary moving bed reactor is fed into the secondary moving bed reactor through a catalyst lifter; (2) feeding a reaction discharge material of the nth-stage moving bed reactor and C9 < + > heavy aromatics into a fixed bed reactor, and contacting with a solid acid transalkylation catalyst in the presence of hydrogen; and (3) separating the product obtained in the step (2). The method can significantly improve the conversion rate of toluene and improve the selectivity of xylene.

Description

Technical Field

[0001] The invention relates to the technical field of xylene preparation, and in particular to a method for producing xylene. Background Art

[0002] Paraxylene (PX) is an important basic organic chemical raw material, mainly used to produce purified terephthalic acid (PTA) and dimethyl terephthalate (DMT). PTA is used to manufacture polyester products such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). In recent years, the demand for PX has been strong and the growth has been rapid.

[0003] At present, large-scale industrial production of aromatics is achieved through aromatics integrated units. Increasing the yield of xylene is an important goal of aromatics integrated units. Existing technologies mainly include toluene disproportionation and alkyl transfer, C8 aromatics isomerization, toluene selective disproportionation, and heavy aromatics lightening.

[0004] Toluene disproportionation and transalkylation technology is an effective way to convert toluene and C9 and C10 heavy aromatics produced by aromatics complex into mixed xylenes and benzene. More than 50% of mixed xylenes in aromatics complexes are produced by this technology, which is the main means to increase PX production in aromatics complexes. However, toluene disproportionation technology cannot utilize C9 / C10 aromatics produced by aromatics complexes. Although the toluene conversion rate of pure toluene disproportionation technology can reach up to 45-50%, a large amount of benzene is also produced as a by-product while mixed xylene products are obtained, and the xylene selectivity is low. The cost of improving the para-selectivity of toluene shape-selective disproportionation technology is a significant decrease in toluene conversion rate, which is only 25-31%. (Yu Zhengxi et al., Research Progress and Development Trend of Para-Xylene Production Technology, Chemical Industry Progress, 2020, 39(12): 4984-4992)

[0005] The benzene and / or toluene alkylation technology using benzene and / or toluene and methanol as reaction raw materials is a new process route for increasing the production of xylene. This technology achieves the purpose of increasing the production of xylene by introducing methyl groups, breaking the limitation of insufficient methyl groups in toluene disproportionation and transalkylation technology. The disadvantages of this technology are that the toluene conversion rate is low, and in addition to the main methylation reaction, deep alkylation will also occur to produce trimethylbenzenes, tetramethylbenzenes and other polymethylbenzenes. In order to improve the stability of the catalyst, the molar ratio of the feed benzene / toluene to the alkylation agent is usually high. The reaction temperature of the benzene / toluene alkylation technology is relatively high, about 400-600°C (Qi Xiaolan et al., Toluene and methanol alkylation to produce PX technology and industrial application, Petrochemical Technology, 2019(2): 131-132).

[0006] The existing xylene production technologies, whether toluene disproportionation and transalkylation technology or pure toluene disproportionation technology, all have the disadvantages of relatively low toluene conversion rate and low xylene selectivity due to a large amount of benzene in the product, resulting in a large amount of toluene circulating in the system, resulting in excessive energy consumption and other problems, and cannot meet the energy-saving and consumption-reducing needs of aromatics complexes.

[0007] CN110678438A discloses a method for producing mixed xylene from heavy reforming product feed, firstly introducing heavy reforming product and hydrogen into a dealkylation reactor to carry out dealkylation reaction; then introducing the effluent into a splitter unit to separate and obtain light gas stream, toluene stream, benzene stream, C9 aromatic stream, C10+ aromatic stream and mixed xylene stream; then introducing the toluene stream, C9 aromatic stream and hydrogen stream into an alkylation reactor for alkylation reaction; introducing the alkylation effluent into a splitter unit; and separating the alkylation effluent in the splitter unit to obtain xylene, wherein the alkylation reactor includes an alkylation catalyst. Its essence is a combination of heavy aromatic dealkylation reaction and aromatic alkylation reaction. Since no additional methyl groups are introduced from the outside like in the methylation reaction, the xylene yield is limited by the ratio of methyl groups to benzene rings in the heavy reforming product feed, and there is a problem of low xylene selectivity. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems of low toluene conversion rate and C9 + In order to solve the problem of low utilization rate of heavy aromatics, a method for producing xylene is provided. The method has the characteristics of high benzene / toluene conversion rate and high xylene yield, which is beneficial to energy saving and consumption reduction.

[0009] In order to achieve the above object, the present invention provides a method for producing xylene, which is carried out in a xylene production device, wherein the device comprises n-stage moving bed reactors and a fixed bed reactor connected in series; each moving bed reactor is provided with a catalyst lifter, wherein n≥2;

[0010] The method comprises:

[0011] (1) feeding an aromatic hydrocarbon feedstock into a first-stage moving bed reactor to contact the aromatic hydrocarbon methylation catalyst loaded in the first-stage moving bed reactor to carry out an alkylation reaction; dividing the alkylation agent into n portions and feeding them into the first to n-stage moving bed reactors respectively;

[0012] The reaction discharge from the first-stage moving bed reactor is used as the reaction feed of the second-stage moving bed reactor; the solid acid aromatic methylation catalyst in the first-stage moving bed reactor is sent to the second-stage moving bed reactor via a catalyst riser; the aromatic raw material is benzene and / or toluene;

[0013] (2) The reaction discharge of the nth stage moving bed reactor, C9 + Heavy aromatics are fed into a fixed bed reactor and contacted with a solid acid transalkylation catalyst under hydrogenation conditions;

[0014] The content of xylene in the reaction discharge of the n-stage moving bed reactor is 20-60wt%; the mass of the reaction discharge of the n-stage moving bed reactor is about the same as that of C9 + The mass ratio of heavy aromatics is 1:(0.5-2);

[0015] (3) Separating the product obtained in step (2) to obtain xylene.

[0016] Preferably, the alkylation reaction is carried out in the absence of a carrier gas.

[0017] The present invention provides a method for producing xylene, which couples the aromatic hydrocarbon methylation reaction with the heavy aromatic hydrocarbon transalkylation reaction. The inventors of the present invention have found in their research that the product of the methylation of benzene and / or toluene is reacted with C9 + Heavy aromatics can be directly used as raw materials for transalkylation reaction. By controlling the composition of the products of benzene and / or toluene methylation, it is possible to solve the problem that disproportionation and transalkylation technology are difficult to increase the yield of xylene, and to utilize C9 + Heavy aromatics can solve the problem that aromatic methylation technology cannot utilize heavy aromatic resources, achieve the effect of increasing xylene production, and greatly reduce material circulation, which is beneficial to energy saving and consumption reduction of the device. In addition, through multi-stage feeding of alkylating agents, compared with single reactor technology, it is also convenient to effectively adjust process parameters, further reduce the occurrence of side reactions, and improve the selectivity of the main reaction products.

[0018] In addition, a multi-stage moving bed reactor is used for a series reaction, and the aromatic methylation catalyst is sent from the preceding moving bed reactor to the succeeding moving bed reactor through a catalyst lifter, thereby reducing the amount of catalyst used. In a preferred case, the alkylation reaction can be carried out without a carrier gas such as hydrogen, and the catalyst flowing out of the last moving bed reactor is regenerated and then returned to the first moving bed reactor, which is beneficial to further improve the economy of the reaction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a reaction system used in one embodiment of the present invention.

[0020] Description of Reference Numerals

[0021] 1-1 1st stage moving bed reactor 1-2 2nd stage moving bed reactor

[0022] 1-n nth stage moving bed reactor 2-1 fixed bed reactor

[0023] 1 Alkylating agent logistics 2 Aromatic hydrocarbon raw material logistics

[0024] 3Hydrogen logistics 4C9+aromatics logistics

[0025] 5. Logistics of Regenerated Solid Acid Aromatic Methylation Catalyst

[0026] 6 Deactivated solid acid aromatic methylation catalyst logistics DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] The present invention provides a method for producing xylene, which is carried out in a xylene production device, wherein the device comprises n-stage moving bed reactors and a fixed bed reactor connected in series; each moving bed reactor is provided with a catalyst lifter, wherein n≥2;

[0029] The method comprises:

[0030] (1) feeding an aromatic hydrocarbon feedstock into a first-stage moving bed reactor to contact the aromatic hydrocarbon methylation catalyst loaded in the first-stage moving bed reactor to carry out an alkylation reaction; dividing the alkylation agent into n portions and feeding them into the first to n-stage moving bed reactors respectively;

[0031] The reaction discharge from the first-stage moving bed reactor is used as the reaction feed of the second-stage moving bed reactor; the solid acid aromatic methylation catalyst in the first-stage moving bed reactor is sent to the second-stage moving bed reactor via a catalyst riser; the aromatic raw material is benzene and / or toluene;

[0032] (2) The reaction discharge of the nth stage moving bed reactor, C9 + Heavy aromatics are fed into a fixed bed reactor and contacted with a solid acid transalkylation catalyst under hydrogenation conditions;

[0033] The content of xylene in the reaction discharge of the n-stage moving bed reactor is 20-60wt%; the mass of the reaction discharge of the n-stage moving bed reactor is about the same as that of C9 + The mass ratio of heavy aromatics is 1:(0.5-2);

[0034] (3) Separating the product obtained in step (2) to obtain xylene.

[0035] The existing xylene production technology, whether it is toluene disproportionation and transalkylation technology or pure toluene disproportionation technology, has the disadvantages of relatively low toluene conversion rate and low xylene selectivity due to a large amount of benzene in the product, resulting in a large amount of toluene circulating in the system, resulting in excessive energy consumption and other problems, and cannot meet the energy conservation and consumption reduction needs of aromatics integrated devices. The method provided by the present invention couples the aromatics methylation reaction and the aromatics transalkylation reaction, and by controlling the composition of the products of benzene and / or toluene methylation, it can not only solve the problem that the disproportionation and transalkylation technology is difficult to improve the xylene yield, but also utilize C9 + Heavy aromatics, solve the defect that aromatics methylation technology cannot utilize heavy aromatics resources, and achieve the effect of increasing the production of xylene; at the same time, by utilizing the characteristics of the moving bed reactor, the solid acid aromatics methylation catalyst is circulated between the multi-stage moving bed reactors, which is conducive to reducing material costs and improving the economy of the production process. Preferably, at the beginning of the reaction, the n-stage moving bed reactors are all filled with solid acid aromatics methylation catalysts. The filling amount in each reactor can be the same or different, and the present invention has no particular limitation on this.

[0036] According to the present invention, the aromatic hydrocarbon feedstock is fed into the device from the first stage moving bed reactor, and the alkylating agent is divided into n portions and fed into the first to nth stage moving bed reactors respectively. For the first stage moving bed reactor, the aromatic hydrocarbon feedstock and the first portion of the alkylating agent may be fed into the reactor separately, or the aromatic hydrocarbon feedstock and the first portion of the alkylating agent may be mixed and then fed into the reactor; the discharge of the first stage moving bed reactor may be mixed with the second portion of the alkylating agent and then used as the reaction feed of the second stage fixed bed reactor, and so on.

[0037] According to the present invention, each moving bed reactor is provided with a catalyst lifter for feeding the solid acid aromatic methylation catalyst in the first moving bed reactor into the second moving bed reactor to realize the circulation of the catalyst in the n-stage moving bed reactor. The catalyst in the n-stage moving bed reactor is returned to the first-stage moving bed reactor or flows out of the device through the catalyst lifter.

[0038] According to some preferred embodiments of the present invention, the xylene production device further comprises a catalyst regenerator. The method further comprises: sending the deactivated solid acid aromatic methylation catalyst into the catalyst regenerator for regeneration treatment.

[0039] In the present invention, "deactivated solid acid aromatic methylation catalyst" refers to a catalyst whose conversion rate of raw material benzene and / or toluene is lower than 30% of the initial conversion rate. Those skilled in the art can send the deactivated catalyst flowing out of any one-stage moving bed reactor to a regeneration reactor through a catalyst lifter for regeneration according to the actual reaction process, and can also supplement fresh solid acid aromatic methylation catalyst according to actual conditions to continue the alkylation reaction. The present invention has no particular limitation on this.

[0040] According to the present invention, the regenerated solid acid aromatic methylation catalyst can be used as a fresh catalyst for standby use, or returned to any one-stage moving bed reactor.

[0041] According to some preferred embodiments of the present invention, the method comprises: sending the solid acid aromatic methylation catalyst in the nth stage moving bed reactor into a regeneration reactor via a catalyst lifter for regeneration treatment, and returning the regenerated solid acid aromatic methylation catalyst to the first stage moving bed reactor.

[0042] The present invention does not particularly limit the conditions of the regeneration treatment, and the regeneration can be carried out under conventional regeneration conditions in the art, and those skilled in the art can make a selection according to actual conditions. Preferably, the regeneration treatment comprises: heat treating the deactivated solid acid aromatic methylation catalyst under an oxygen-containing atmosphere. Preferably, the heat treatment temperature is 400-700°C, preferably 500-600°C, the pressure is 0.01-10MPa, preferably 0.1-0.5MPa, and the regeneration time is 1-70h, preferably 5-10h.

[0043] Preferably, the oxygen-containing atmosphere is provided by air.

[0044] In the present invention, the reaction discharge of the nth stage moving bed reactor is directly or optionally sent to the fixed bed reactor after heat exchange, and no separation or purification process is involved.

[0045] According to the present invention, the content of xylene in the composition of the reaction discharge of the nth stage moving bed reactor in step (1) is controlled, and then it is directly used as a reaction raw material to react with C9 + The transalkylation reaction of heavy aromatics is beneficial to the coordinated alkylation reaction and transalkylation reaction, achieving reaction performance with quasi-atom economy and maximizing the xylene yield.

[0046] According to some preferred embodiments of the present invention, the reaction output of the nth stage moving bed reactor includes benzene, xylene and optional non-xylene alkylbenzene. Preferably, the non-xylene alkylbenzene is selected from at least one of toluene, trimethylbenzene and tetramethylbenzene.

[0047] According to some preferred embodiments of the present invention, in the reaction discharge of the n-stage moving bed reactor, the content of xylene is 20-60wt%, preferably 25-55wt%, and the content of non-xylene alkylbenzene is 40-80wt%, preferably 45-75wt%. By controlling the composition of the reaction discharge of the n-stage fixed bed reactor within the above preferred range, it is beneficial to ensure the conversion rate and the selectivity of the xylene product. If the xylene content is too high, the conversion rate may be too low, and if it is too low, the xylene selectivity may be low.

[0048] In the present invention, the xylene production device includes at least two stages of moving bed reactors, and those skilled in the art can select them according to actual conditions, as long as the composition of the reaction discharge of the final moving bed reactor is controlled within the above range. Preferably, n is selected from a positive integer of 3-30. The above preferred embodiment is adopted to facilitate the coordinated alkylation reaction and transalkylation reaction, achieve reaction performance with quasi-atomic economy, and maximize the xylene yield.

[0049] According to some preferred embodiments of the present invention, in step (1), the molar ratio of the total molar amount of the alkylating agent introduced into the n-stage moving bed reactor to the aromatic hydrocarbon feedstock is (0.2-3):1, preferably (0.5-2):1.

[0050] In the present invention, the molar amount of the alkylating agent introduced into each moving bed reactor can be the same or different. In a further preferred embodiment, the ratio of the feed amount of the alkylating agent in the latter moving bed reactor to the feed amount of the alkylating agent in the previous moving bed reactor is (0.5-1.2):1, preferably (0.6-1):1. The use of the above preferred alkylating agent feeding method is conducive to exerting the performance of the alkylation catalyst in each reactor and controlling the bed temperature rise.

[0051] According to some preferred embodiments of the present invention, the ratio of the SiO2 / Al2O3 molar ratio of the first solid acid zeolite molecular sieve contained in the solid acid aromatic methylation catalyst to the SiO2 / Al2O3 molar ratio of the second solid acid zeolite molecular sieve contained in the solid acid transalkylation catalyst is 2-15, preferably 2.5-12. The present invention controls the ratio of the silicon-aluminum molar ratio of the first solid acid zeolite molecular sieve in the solid acid aromatic methylation catalyst to the silicon-aluminum molar ratio of the second solid acid zeolite molecular sieve in the solid acid transalkylation catalyst, so that the acidity of the two catalysts is mutually matched, and then the degree of alkylation reaction and transalkylation reaction is controlled, which is conducive to further improving the conversion rate of the reaction raw materials and the yield of the target product xylene, and reducing the energy consumption of the reaction device.

[0052] According to some preferred embodiments of the present invention, the method further comprises: using C9 +The heavy aromatics are used to exchange heat with the discharge of the n-stage moving bed reactor, and then sent to the fixed bed reactor. The inventors of the present invention have found in their research that due to the continuous heat release of the alkylation reaction, the discharge temperature of the n-stage moving bed reactor is relatively high. By using C9 + The heavy aromatics heat exchange with the reaction discharge of the n-stage moving bed reactor can increase the C9 + The temperature of the heavy aromatic feedstock is beneficial to the effective utilization of the heat of the device to reduce energy consumption, and can also reduce the inlet temperature of the fixed bed reactor to a suitable reaction temperature, which is beneficial to the alkyl transfer reaction and reduces possible side reactions.

[0053] Preferably, the temperature of the reaction feed of the fixed bed reactor is 10-100°C lower than the temperature of the reaction discharge of the nth stage moving bed reactor, preferably 30-90°C.

[0054] According to the present invention, preferably, the alkylation reaction is carried out in the absence of a carrier gas. In the prior art, in order to increase the service life of the catalyst, the alkylation reaction is usually carried out in the presence of hydrogen. The present invention uses a series of moving bed reactors with staged feeding of the alkylation agent, which is beneficial to improving the stability of the catalyst, and can carry out the alkylation reaction in the absence of hydrogen, and the reaction cycle is long.

[0055] Preferably, in step (1), relative to the total mass of the solid acid aromatic methylation catalyst loaded in the first to nth stage moving bed reactors, the mass space velocity of the aromatic feedstock is 1-15h -1 , preferably 2-10h -1 .

[0056] Preferably, the conditions of the first to nth moving bed reactors independently include: the reactor inlet temperature is 310-480°C, preferably 320-460°C; the pressure is 0.2-3.8MPa, preferably 0.5-3.5MPa. In the present invention, in the n-stage moving bed reactor, the reaction conditions in each stage of the moving bed reactor can be the same or different, and all meet the above preferred ranges, and those skilled in the art can adjust according to actual needs.

[0057] According to the present invention, preferably, in the aromatic hydrocarbon raw material, the molar ratio of methyl group to benzene ring is 0.3-4:1, preferably 0.5-2:1. The use of the above preferred aromatic hydrocarbon raw material composition is conducive to further improving the yield of xylene product.

[0058] In the present invention, the selection range of the alkylating agent is relatively wide, and any alkylating agent that can introduce a methyl group conventionally used in the art can be used. Preferably, the alkylating agent is selected from at least one of methanol, dimethyl ether, methyl bromide and carbon monoxide, more preferably methanol.

[0059] In the present invention, the composition of the solid acid aromatic hydrocarbon methylation catalyst can be selected in a wide range. Preferably, the solid acid aromatic hydrocarbon methylation catalyst comprises a first solid acid zeolite molecular sieve, a first binder and an optional first active component; the first solid acid zeolite molecular sieve is selected from at least one of MFI type, MEL type, FER type and TON type topological structure molecular sieves, preferably an MFI type topological structure molecular sieve; for example, a ZSM-5 molecular sieve. With this preferred embodiment, the molecular sieve has a suitable acid strength, which is conducive to further improving the activity of catalyzing the aromatic hydrocarbon methylation reaction.

[0060] Preferably, the SiO2 / Al2O3 molar ratio of the first solid acid zeolite molecular sieve is 80-300, preferably 85-200; in the above preferred case, it is beneficial to improve the stability of the catalyst while maintaining a high catalytic activity.

[0061] In the present invention, there is no particular limitation on the type of the first binder. Preferably, in step (1), the first binder is aluminum oxide and / or silicon oxide.

[0062] In the present invention, preferably, the solid acid aromatic methylation catalyst optionally contains an active component. Preferably, in step (1), the first active component is selected from at least one of rare earth elements and Group VIII metal elements, and more preferably, the active component is selected from at least one of La, Ce, Fe, Co and Ni.

[0063] In a further preferred embodiment, the first active component includes rare earth elements and Group VIII metal elements, more preferably La and Ni.

[0064] Preferably, the mass ratio of the rare earth element to the Group VIII metal element is 1:(0.5-2).

[0065] In some preferred embodiments, relative to 100 parts by weight of the first solid acid zeolite molecular sieve, the content of the first binder is 15-400 parts by weight, preferably 20-200 parts by weight, and the content of the first active component is 0-80 parts by weight, preferably 10-75 parts by weight.

[0066] In the present invention, there is no particular limitation on the preparation method of the solid acid aromatic hydrocarbon methylation catalyst, which may be a method conventionally defined in the art. For example, it may be prepared by the following method: an ammonium-type first solid acid zeolite molecular sieve powder and a first binder are mixed, and the mixture is molded, dried and calcined, and then the first active component is optionally loaded to obtain a solid acid aromatic hydrocarbon methylation catalyst, wherein the content of the first binder is 15-400 parts by weight relative to 100 parts by weight of the first solid acid zeolite molecular sieve.

[0067] Preferably, the method further comprises: optionally introducing an active component before or after the catalyst is extruded. In the present invention, there is no particular limitation on the molding method, for example, it can be extrusion molding. In the present invention, there is no particular limitation on the drying conditions, preferably, the drying temperature is 100-140°C and the time is 1-8h. In the present invention, there is no particular limitation on the calcination conditions, preferably, the calcination temperature is 450-600°C and the time is 2-8h.

[0068] In the present invention, the type and properties of the first solid acid zeolite molecular sieve, the type of the first binder and the type of the active component have been described in the foregoing content and will not be repeated here.

[0069] In the present invention, the first binder is preferably a material that can be converted into oxides by calcination, for example, pseudo-boehmite and / or silica sol.

[0070] In the present invention, the preparation method of the solid acid aromatic methylation catalyst also includes introducing a first extrusion molding aid and / or a first peptizing agent during the molding process. Those skilled in the art can select the type and amount of the first extrusion molding aid and the first peptizing agent within a reasonable range according to the specific circumstances of the extrusion molding. Preferably, the first extrusion molding aid is selected from at least one of sesbania powder, dextrin and methylcellulose. Preferably, the first peptizing agent is selected from at least one of nitric acid, acetic acid and citric acid.

[0071] In a preferred embodiment, relative to 100 parts by weight of the first solid acid zeolite molecular sieve, the amount of the first extrusion molding aid is 1-30 parts by weight, and the amount of the first peptizing agent is 1-8 parts by weight.

[0072] In the present invention, there is no special requirement for the loading method of the first active component, and a conventional method can be used, such as impregnating the calcined product with a solution of a soluble precursor compound containing the first active component, and then drying and calcining. The present invention also has no special restrictions on the conditions of the drying and calcining, and those skilled in the art can choose according to actual conditions. Preferably, the drying temperature is 100-140°C and the time is 1-8h. Preferably, the calcination temperature is 450-600°C and the time is 2-8h.

[0073] Preferably, the precursor of Fe is selected from at least one of ferric nitrate, basic iron carbonate and ferric acetate. Preferably, the precursor of Co is selected from at least one of cobalt nitrate, basic cobalt carbonate and cobalt acetate. Preferably, the precursor of Ni is selected from at least one of nickel nitrate, basic nickel carbonate and nickel acetate. Preferably, the precursor of the rare earth element is selected from the water-soluble salts of each, for example, it can be at least one of lanthanum nitrate, lanthanum sulfate, lanthanum chloride, lanthanum acetate, lanthanum carbonate, lanthanum oxalate, cerium nitrate and cerium chloride.

[0074] According to the present invention, preferably, the quality of the reaction discharge of the nth stage moving bed reactor is similar to that of C9 + The mass ratio of heavy aromatics is 1:(0.5-2), preferably 1:(0.6-1.5). By controlling the mass of the reaction discharge of the nth stage moving bed reactor and C9 + The mass ratio of heavy aromatics being within the above preferred range is beneficial to exerting the performance of the transalkylation catalyst and improving the xylene yield.

[0075] According to the present invention, in step (2), the reaction discharge of the nth stage moving bed reactor, C9 + The heavy aromatic hydrocarbons are contacted with a solid acid transalkylation catalyst under hydrogenation conditions to carry out a transalkylation reaction. Preferably, in step (2), the contacting conditions include: a reactor inlet temperature of 300-450°C, preferably 320-430°C; C9 + The mass space velocity of heavy aromatics is 1-8h -1 , preferably 1-6h -1 The pressure is 1-5 MPa, preferably 1-4 MPa; the hydrogen-to-oil molar ratio is 1-6, preferably 1-4. Under the above preferred reaction conditions, the main transalkylation reaction is favorable.

[0076] In the present invention, unless otherwise specified, the pressures described in the present invention are gauge pressures.

[0077] According to the present invention, preferably, the C9 + Heavy aromatics selected from C9 + Monocyclic aromatic hydrocarbons and / or condensed aromatic hydrocarbons, the present invention is for the C9 + The specific composition of the heavy aromatics is not particularly limited, and for example, the heavy aromatics may contain at least one of trimethylbenzene, tetramethylbenzene, methylethylbenzene and dimethylethylbenzene.

[0078] Preferably, the C9 + Among heavy aromatics, C 10 The content of aromatic hydrocarbons is 1-75wt%, preferably 5-60wt%. In the above preferred case, it is beneficial to improve the efficiency of transalkylation reaction.

[0079] According to some preferred embodiments of the present invention, the solid acid transalkylation catalyst comprises a second solid acid zeolite molecular sieve, a second binder and an optional second active component; the second solid acid zeolite molecular sieve is selected from at least one of MFI type, MWW type, BEA type, MOR type, FAU type topology structure molecular sieves and BEA / MOR symbiotic molecular sieves, preferably at least one of BEA type, MOR type topology structure molecular sieves and BEA / MOR symbiotic molecular sieves, and further preferably BEA / MOR symbiotic molecular sieves.

[0080] In the present invention, it is understood that the BEA / MOR symbiotic molecular sieve refers to a two-phase symbiotic molecular sieve formed by the intergrowth of twins of two phases with different structural types of BEA and MOR. The BEA type and MOR type molecular sieves have conventional definitions in the art, the BEA type molecular sieve is, for example, a beta zeolite molecular sieve, and the MOR type molecular sieve is, for example, a mordenite molecular sieve.

[0081] Preferably, in the BEA / MOR symbiotic molecular sieve, the mass ratio of the BEA type to the MOR type molecular sieve is 95:5-5:95, preferably 85:15-35:65.

[0082] In a preferred embodiment, the molar ratio of silicon oxide to aluminum oxide in the second solid acid zeolite molecular sieve is 10-80, preferably 15-60. The advantage of adopting this preferred embodiment is that its acid properties are more suitable for catalyzing aromatic hydrocarbon transalkylation reactions.

[0083] Preferably, the second binder is at least one of aluminum oxide, silicon oxide, titanium oxide, zinc oxide and zirconium oxide.

[0084] Preferably, the second active component is selected from at least one of Group VA metal elements and Group VIB metal elements, for example, it can be selected from at least one of Sb, Bi, Cr, Mo and W.

[0085] In a further preferred embodiment, the second active component includes any one of the metal elements of Group VA and any one of the metal elements of Group VIB.

[0086] Preferably, in the second active component, the mass ratio of the metal element of group VA to the metal element of group VIB is 10-1:1-10. In the above preferred case, it is beneficial to match the performance of the metal and the molecular sieve, and improve the activity, selectivity and stability of the transalkylation catalyst.

[0087] Preferably, the Group VA metal element is selected from Sb and / or Bi, more preferably Bi.

[0088] Preferably, the Group VIB metal element is at least one selected from Cr, Mo and W, and more preferably Mo.

[0089] Preferably, relative to 100 parts by weight of the second solid acid zeolite molecular sieve, the content of the second binder is 15-200 parts by weight, preferably 20-150 parts by weight; the content of the second active component is 2-160 parts by weight, preferably 10-80 parts by weight.

[0090] According to some preferred embodiments of the present invention, the solid acid transalkylation catalyst is prepared by the following method, comprising:

[0091] S1, subjecting the second solid acid zeolite molecular sieve raw powder to at least one acid treatment;

[0092] S2, exchanging the product obtained by acid treatment with ammonium to obtain an ammonium-type second solid acid zeolite molecular sieve;

[0093] S3, mixing and molding the ammonium type second solid acid zeolite molecular sieve and the second binder precursor, and drying and calcining to obtain a catalyst molded body;

[0094] S4, treating the catalyst shaped body with ammonia-containing water vapor to obtain a catalyst precursor;

[0095] The method further comprises: introducing metal active components into the mixing in step S3, or introducing metal active components into the catalyst precursor by an impregnation method.

[0096] According to some preferred embodiments of the present invention, the acid treatment in step S1 comprises: contacting the second solid acid zeolite molecular sieve with an acid solution. The acid solution may be an aqueous solution of an organic acid and / or an inorganic acid, preferably, the acid solution is selected from at least one of citric acid, acetic acid, glycolic acid, oxalic acid and ethylenediaminetetraacetic acid. Preferably, the concentration of the acid solution is 0.2-4.5 mol / L.

[0097] Preferably, the acid treatment is performed 1-4 times, more preferably 1-2 times.

[0098] Preferably, the acid treatment conditions include: temperature of 50-90° C. and time of 2-15 h.

[0099] According to some preferred embodiments of the present invention, those skilled in the art can reasonably select the type and amount of ammonium salt used and the solid-liquid ratio of ammonium exchange according to the specific circumstances of ammonium exchange to obtain ammonium-type solid acid zeolite.

[0100] According to some preferred embodiments of the present invention, in step S3, relative to 100 parts by weight of the ammonium type second solid acid zeolite molecular sieve, the amount of the second binder is 15-200 parts by weight, preferably 20-150 parts by weight; preferably, the second binder precursor refers to any substance that can be calcined to obtain the second binder, which is well known to those skilled in the art.

[0101] In the present invention, the preparation method of the transalkylation catalyst further comprises introducing a second extrusion molding aid during the molding process. Those skilled in the art can select the type and amount of the second extrusion molding aid within a reasonable range according to the specific conditions of the extrusion molding. Preferably, the second extrusion molding aid is selected from at least one of sesbania powder, dextrin and methylcellulose.

[0102] In a preferred embodiment, the amount of the second extrusion molding aid is 1-20 parts by weight relative to 100 parts by weight of the second solid acid zeolite molecular sieve.

[0103] In the present invention, the type and properties of the second solid acid zeolite molecular sieve and the type and amount of the second binder have been described in the above content and will not be repeated here.

[0104] In the present invention, the selection range of the loading method of the second active component is relatively wide. According to the present invention, the precursor compound of the second active component can be added during the mixing process in step S3, and then the molding can be performed; or after the catalyst precursor is obtained in step S4, the second active component can be loaded on the catalyst precursor by impregnation. Preferably, after the catalyst precursor is obtained in step 4, the second active component is loaded on the catalyst precursor by impregnation. The above preferred embodiment is conducive to better matching of the metal component and the acid center of the molecular sieve, and the synergistic effect is better.

[0105] Preferably, the precursor compound of the second active component can be an organic salt or an inorganic salt containing the second active component, preferably at least one of nitrate, acetate, basic carbonate, chloride, acetate, carbonate, oxalate and sulfate. The amount of the precursor compound of the second active component is based on the composition of the prepared catalyst.

[0106] The present invention has no particular limitation on the specific operation of the impregnation method, which can be the same as the loading method and operating conditions of the active components in the solid acid aromatic methylation catalyst described above, and will not be described in detail here.

[0107] In the present invention, there is no particular limitation on the drying conditions of the solid acid transalkylation catalyst. Preferably, in step S3, the drying conditions include: a temperature of 100-140° C. and a time of 2-24 hours.

[0108] According to the present invention, preferably, the calcination conditions in step S3 include: a temperature of 200-600° C. and a time of 3-10 h.

[0109] In the present invention, it can be understood that as long as the ammonia-containing water vapor can be brought into contact with the catalyst molded body, the specific method of providing the ammonia-containing water vapor and the contact form with the catalyst molded body are not particularly limited. Preferably, the treatment conditions include: bringing the ammonia water into contact with the catalyst precursor under conditions that satisfy the vaporization of ammonia and water. In this preferred embodiment, the specific operation can be to introduce an ammonia-containing aqueous solution into a container containing the catalyst precursor, and then increase the temperature to vaporize the ammonia and water.

[0110] In the present invention, there is no particular limitation on the concentration of the aqueous ammonia. Preferably, the aqueous ammonia has an ammonia content of 5-25% by weight, more preferably 10-20% by weight.

[0111] In the present invention, there is no particular limitation on the contact conditions between the aqueous ammonia and the catalyst molding. Preferably, the contact conditions include: a temperature of 200-600°C, a time of 1-12 hours, a mass space velocity of the aqueous ammonia of 0.5-10 h -1 Further preferably, the contact conditions include: temperature of 250-550°C, time of 2-10h, mass space velocity of ammonia water of 1-6h -1 .

[0112] The method for preparing a solid acid transalkylation catalyst using the above preferred embodiment has the advantages of optimizing the pore structure of the catalyst and improving diffusion, which is conducive to further improving the yield of xylene.

[0113] According to some preferred embodiments of the present invention, the separation in step (3) also obtains dry gas and gas containing benzene, toluene, C9 + A further stream of at least one of the heavy aromatic hydrocarbons.

[0114] Preferably, the method further comprises: returning the mixture containing benzene and / or toluene to step (1) for reuse, so as to provide at least part of the aromatic hydrocarbon feedstock in step (1). + The heavy aromatics are returned to step (2) for reuse to provide at least part of the C9 + Heavy aromatics. The preferred implementation method of logistics recycling can improve resource utilization and reduce material loss.

[0115] The present invention will be described in detail below through examples.

[0116] The conversion of each reactant and the selectivity of xylene are defined as follows:

[0117]

[0118]

[0119] The following preparation examples are used to illustrate the preparation of the solid acid aromatic methylation catalyst in the present invention.

[0120] Preparation Example A1

[0121] (1) 100 parts by weight of ammonium ZSM-5 molecular sieve powder (silicon-aluminum molar ratio SiO2 / Al2O3 is 150), 107 parts by weight of silica sol (containing 40 wt% SiO2) and 15 parts by weight of sesbania powder are mixed and extruded into strips, dried at 120°C for 3 hours, calcined at 550°C in air for 4 hours, and sheared to obtain a cylindrical carrier with a diameter of 2.0 mm and a length of 2.0 mm.

[0122] (2) The obtained cylindrical carrier was impregnated with a mixed aqueous solution of lanthanum nitrate and nickel nitrate (with respect to 100 parts by weight of ammonium ZSM-5 molecular sieve, lanthanum content was 20 parts by weight, and nickel content was 20 parts by weight), allowed to stand for 4 hours, dried at 120°C for 3 hours, and calcined at 550°C in an air atmosphere for 4 hours to obtain a solid acid aromatic methylation catalyst M1.

[0123] Preparation Example A2

[0124] (1) 100 parts by weight of ammonium ZSM-5 molecular sieve powder (silicon-aluminum molar ratio SiO2 / Al2O3 is 123), 100 parts by weight of silica sol (containing 40 wt% SiO2) and 15 parts by weight of sesbania powder are mixed and extruded into strips, dried at 120°C for 3 hours, calcined at 550°C in air for 4 hours, and sheared to obtain a cylindrical carrier with a diameter of 2.0 mm and a length of 2.0 mm.

[0125] (2) The obtained cylindrical carrier was impregnated with a mixed aqueous solution of lanthanum nitrate and nickel nitrate (relative to 100 parts by weight of ammonium-type ZSM-5 molecular sieve, the lanthanum content was 10 parts by weight and the nickel content was 10 parts by weight), allowed to stand for 4 hours, dried at 120°C for 3 hours, and calcined at 550°C in an air atmosphere for 4 hours to obtain a solid acid aromatic methylation catalyst M2.

[0126] The following preparation examples are used to illustrate the preparation of the solid acid transalkylation catalyst of the present invention.

[0127] Preparation Example B1

[0128] (1) BEA / MOR symbiotic molecular sieve raw powder (silicon-aluminum molar ratio SiO2 / Al2O3 is 25, and the mass ratio of β zeolite to mordenite phase composition is BEA / MOR=35 / 65) is taken, and it is contacted with 0.5 mol / L glycolic acid at a temperature of 80°C, and the acid treatment is performed twice, each time for 4 hours;

[0129] (2) exchanging the BEA / MOR symbiotic molecular sieve obtained by acid treatment with ammonium to obtain an ammonium-type BEA / MOR symbiotic molecular sieve;

[0130] (3) 100 parts by weight of ammonium-type BEA / MOR symbiotic molecular sieve powder, 25 parts by weight of alumina binder and 15 parts by weight of extrusion molding aid sesbania powder were mixed and uniformly extruded into strips. The mixture was dried at 140° C. for 3 hours and then calcined at 550° C. for 3 hours to obtain a catalyst molded body A1;

[0131] (4) The catalyst molded body A1 was treated with water vapor containing aqueous ammonia (specifically, an aqueous solution containing 20 wt% aqueous ammonia was brought into contact with A1 at a temperature of 250° C. for 10 h and a mass space velocity of the aqueous ammonia solution of 1 h -1 ), to obtain a solid acid transalkylation catalyst precursor PA1;

[0132] (5) The obtained catalyst precursor PA1 was impregnated with a mixed aqueous solution of bismuth nitrate and ammonium heptamolybdate (containing 20 parts by weight of bismuth and 20 parts by weight of molybdenum relative to 100 parts by weight of ammonium-type BEA / MOR symbiotic molecular sieve), allowed to stand for 4 hours, dried at 120°C for 3 hours, and calcined at 550°C in an air atmosphere for 4 hours to obtain a solid acid transalkylation catalyst T1.

[0133] Preparation Example B2

[0134] (1) BEA / MOR symbiotic molecular sieve raw powder (silicon-aluminum molar ratio SiO2 / Al2O3 is 33, and the mass ratio of β zeolite to mordenite phase composition is BEA / MOR=48 / 52), is brought into contact with citric acid with a concentration of 1.0 mol / L at a temperature of 70°C, and is subjected to two acid treatments, each for 6 h;

[0135] (2) exchanging the BEA / MOR symbiotic molecular sieve obtained by acid treatment with ammonium to obtain an ammonium-type BEA / MOR symbiotic molecular sieve;

[0136] (3) 100 parts by weight of ammonium BEA / MOR symbiotic molecular sieve powder, 25 parts by weight of pseudo-boehmite and 15 parts by weight of extrusion molding aid sesbania powder were mixed, and a mixed aqueous solution of bismuth nitrate and chromium nitrate (containing 40 parts by weight of bismuth and 20 parts by weight of chromium relative to 100 parts by weight of ammonium BEA / MOR symbiotic molecular sieve) was added, mixed evenly, and extruded into strips. The mixture was dried at 140°C for 3 hours and then calcined at 550°C for 8 hours to obtain a catalyst molded body A2;

[0137] (4) The catalyst molded body A2 was treated with water vapor containing aqueous ammonia (specifically, an aqueous solution containing 10 wt % aqueous ammonia was brought into contact with A2 at a temperature of 350° C. for 3 h and a mass space velocity of the aqueous ammonia solution of 2 h -1 ), to obtain a solid acid transalkylation catalyst precursor PA2;

[0138] (5) The obtained catalyst precursor PA2 was dried at 120° C. for 3 hours and calcined at 550° C. for 4 hours in an air atmosphere to obtain a solid acid transalkylation catalyst T2.

[0139] Preparation Example B3

[0140] The method of Preparation Example B1 was followed, except that the active component loading in step (5) was not performed, and the solid acid transalkylation catalyst precursor PA1 was used as the solid acid transalkylation catalyst T3.

[0141] Preparation Example B4

[0142] The method of Preparation Example B1 is followed, except that in step (5), the obtained catalyst precursor PA1 is impregnated with an aqueous solution of ammonium heptamolybdate (containing 20 parts by weight of molybdenum relative to 100 parts by weight of ammonium-type BEA / MOR symbiotic molecular sieve), allowed to stand for 4 hours, dried at 120°C for 3 hours, and calcined at 550°C in an air atmosphere for 4 hours to obtain a solid acid transalkylation catalyst T4.

[0143] Preparation Example B5

[0144] The method of Preparation Example B1 is followed, except that the silicon-aluminum molar ratio SiO2 / Al2O3 of the BEA / MOR symbiotic molecular sieve raw powder used in step (1) is 75, the mass ratio of the β zeolite and mordenite phase composition is BEA / MOR=50 / 50, and the other conditions and steps are the same as B1, recorded as solid acid transalkylation catalyst T5.

[0145] The following examples are used to illustrate the production method of xylene in the present invention.

[0146] Example 1

[0147] like Figure 1 As shown, the xylene production device includes four moving bed reactors and one fixed bed reactor connected in series, each reactor has a volume of 50 ml, and each moving bed reactor is also provided with a catalyst lifter. Before feeding, the four moving bed reactors are respectively filled with 15 ml of solid acid aromatic methylation catalyst M1, and the fixed bed reactor is filled with 15 ml of solid acid transalkylation catalyst T1.

[0148] The ratio of the molar ratio of silicon oxide to aluminum oxide of the first solid acid zeolite molecular sieve ZSM-5 in the solid acid aromatic methylation catalyst M1 to the molar ratio of silicon oxide to aluminum oxide of the second solid acid zeolite molecular sieve BEA / MOR intergrowth molecular sieve in the solid acid transalkylation catalyst T1 is 6.

[0149] Toluene flows from the first moving bed reactor to the fourth moving bed reactor in sequence. The alkylating agent methanol is divided into four equal parts and introduced into four moving bed reactors respectively. Before entering the first moving bed reactor, it is evenly mixed with toluene and then contacted with the catalyst M1 for alkylation reaction. The remaining parts of methanol are evenly mixed with the outlet flow of the previous reactor before entering the second, third and fourth moving bed reactors. The solid acid aromatic methylation catalyst M1 in the first moving bed reactor is sent to the next moving bed reactor through the catalyst lifter. The fourth flow flowing out of the fourth moving bed reactor and the newly introduced carbon nine and carbon ten aromatics are mixed at the inlet of the fixed bed reactor and then enter the fixed bed reactor, contacting with the solid acid transalkylation catalyst T1 in the reactor for transalkylation reaction. The catalyst in the fourth moving bed reactor is sent to the catalyst regenerator through the catalyst lifter for regeneration treatment, and the regenerated catalyst returns to the first moving bed reactor.

[0150] The alkylation conditions include:

[0151] The molar ratio of toluene to the total amount of methanol in the four moving bed reactors: 2.0;

[0152] Inlet temperature of four moving bed reactors: 400 °C;

[0153] Reaction pressure of four moving bed reactors: 1.0 MPa;

[0154] Mass space velocity of toluene relative to the total mass of solid acid aromatic methylation catalyst in four moving bed reactors: 4.0 h -1 ;

[0155] The outlet temperature of the fourth moving bed reactor is 428°C.

[0156] The reaction output of the fourth moving bed reactor includes benzene, toluene, xylene, C9 + Aromatic hydrocarbons, etc., wherein the content of xylene is 45wt%, and the content of non-xylene alkylbenzene is 65wt%.

[0157] The transalkylation reaction conditions include:

[0158] The fixed bed reactor inlet temperature was 360°C;

[0159] Reaction pressure: 3.0MPa;

[0160] The quality of the reaction discharge from the fourth moving bed is similar to that of C9 + The mass ratio of heavy aromatics is 1:1;

[0161] C9 + Heavy aromatic hydrocarbon composition: The mass percentage of C10 aromatic hydrocarbons is 20%;

[0162] C9+ Mass space velocity of heavy aromatics: 2.0h -1 ;

[0163] Hydrogen to oil molar ratio: 3.

[0164] The regeneration conditions of the catalyst include: after the catalyst is dried, it is calcined at 550° C. in an air atmosphere for 5 hours.

[0165] The reaction product flowing out of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, with a total of 6 samples taken. The average toluene conversion rate (mass) after 72 hours of reaction was 55.2%, and the average xylene selectivity (mass) was 89.2%.

[0166] Example 2

[0167] The xylene production device includes four moving bed reactors and one fixed bed reactor connected in series, each reactor has a volume of 50 ml, and each moving bed reactor is also provided with a catalyst lifter. Before feeding, the four moving bed reactors are respectively filled with 15 ml of solid acid aromatic methylation catalyst M2, and the fixed bed reactor is filled with 15 ml of solid acid transalkylation catalyst T2.

[0168] The ratio of the molar ratio of silicon oxide to aluminum oxide of the first solid acid zeolite molecular sieve ZSM-5 in the solid acid aromatic methylation catalyst M2 to the molar ratio of silicon oxide to aluminum oxide of the second solid acid zeolite molecular sieve BEA / MOR symbiotic molecular sieve in the solid acid transalkylation catalyst T2 is 4.

[0169] Toluene flows from the first moving bed reactor to the fourth moving bed reactor in sequence. The alkylating agent methanol is divided into four equal parts and introduced into four moving bed reactors respectively. Before entering the first moving bed reactor, it is evenly mixed with toluene and then contacted with the catalyst M2 for alkylation reaction. The remaining parts of methanol are evenly mixed with the outlet flow of the previous reactor before entering the second, third and fourth moving bed reactors. The solid acid aromatic methylation catalyst M2 in the first moving bed reactor is sent to the next moving bed reactor through the catalyst lifter. The fourth flow flowing out of the fourth moving bed reactor and the newly introduced carbon nine and carbon ten aromatics are mixed at the inlet of the fixed bed reactor and then enter the fixed bed reactor, contacting with the solid acid transalkylation catalyst T2 in the reactor for transalkylation reaction. The catalyst in the fourth moving bed reactor is sent to the catalyst regenerator through the catalyst lifter for regeneration treatment, and the regenerated catalyst returns to the first moving bed reactor.

[0170] The alkylation conditions include:

[0171] The molar ratio of toluene to the total amount of methanol in the four moving bed reactors: 1.5;

[0172] Inlet temperature of four moving bed reactors: 450 °C;

[0173] Reaction pressure of four moving bed reactors: 3MPa;

[0174] Mass space velocity of toluene relative to the total mass of solid acid aromatic methylation catalyst in four moving bed reactors: 4 hours -1 ;

[0175] The outlet temperature of the fourth moving bed reactor was 484°C.

[0176] The reaction output of the fourth moving bed reactor includes benzene, toluene, xylene, C9 + Aromatic hydrocarbons, etc., wherein the content of xylene is 58wt%, and the content of non-xylene alkylbenzene is 42wt%.

[0177] The transalkylation reaction conditions include:

[0178] The fixed bed reactor inlet temperature was 420°C;

[0179] Reaction pressure: 3MPa;

[0180] The quality of the reaction discharge from the fourth moving bed is similar to that of C9 + The mass ratio of heavy aromatics is 1:1.5;

[0181] C9 + Heavy aromatics composition: The mass percentage of C10 aromatics is 55%;

[0182] C9 + Mass space velocity of heavy aromatics: 2h -1 ;

[0183] Hydrogen to oil molar ratio: 4.

[0184] The regeneration conditions of the catalyst include: after the catalyst is dried, it is calcined at 550° C. in an air atmosphere for 5 hours.

[0185] The reaction product flowing out of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, with a total of 6 samples taken. The average toluene conversion rate (mass) after 72 hours of reaction was 68.5%, and the average xylene selectivity (mass) was 93.1%.

[0186] Example 3

[0187] The method of Example 1 is followed, except that the solid acid aromatic methylation catalyst is M1 and the solid acid transalkylation catalyst is T3.

[0188] The reaction was carried out under the same reaction conditions as in Example 1. The reaction product at the outlet of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours. A total of 6 samples were taken. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 50.1%, and the average xylene selectivity (mass) was 84.5%.

[0189] Example 4

[0190] The method of Example 1 is followed, except that the solid acid aromatic methylation catalyst is M1 and the solid acid transalkylation catalyst is T4.

[0191] The reaction was carried out under the same reaction conditions as in Example 1. The reaction product at the outlet of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours. A total of 6 samples were taken. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 51.9%, and the average xylene selectivity (mass) was 81.8%.

[0192] Example 5

[0193] The method of Example 1 is followed, except that the solid acid aromatic methylation catalyst is M1 and the solid acid transalkylation catalyst is T5. The molar ratio of silicon oxide to aluminum oxide of the first solid acid zeolite molecular sieve ZSM-5 in the solid acid aromatic methylation catalyst M1 and the molar ratio of silicon oxide to aluminum oxide of the second solid acid zeolite molecular sieve BEA / MOR intergrowth molecular sieve in the solid acid transalkylation catalyst T5 is 1.6.

[0194] The reaction was carried out under the same reaction conditions as in Example 1. The reaction product at the outlet of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours. A total of 6 samples were taken. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 40.5%, and the average xylene selectivity (mass) was 77.6%.

[0195] Example 6

[0196] According to the method of Example 1, the difference is that

[0197] The alkylation conditions include:

[0198] The molar ratio of toluene to the total amount of methanol in the four moving bed reactors: 3.5;

[0199] Inlet temperature of four moving bed reactors: 400 °C;

[0200] Reaction pressure of four moving bed reactors: 1.0 MPa;

[0201] Mass space velocity of toluene relative to the total mass of solid acid aromatic methylation catalyst in four moving bed reactors: 4 hours -1 ;

[0202] The outlet temperature of the fourth moving bed reactor was 419°C.

[0203] The reaction output of the fourth moving bed reactor includes benzene, toluene, xylene, C9+ aromatics, etc., wherein the content of xylene is 38wt%, and the content of non-xylene alkylbenzene is 62wt%.

[0204] Then, the transalkylation reaction was carried out according to the method of Example 1.

[0205] The reaction product at the outlet of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, with a total of 6 samples taken. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 44.9%, and the average xylene selectivity (mass) was 81.9%.

[0206] Example 7

[0207] According to the method of Example 1, the difference is that

[0208] The transalkylation reaction conditions include:

[0209] The fixed bed reactor inlet temperature was 490°C;

[0210] Reaction pressure: 3.0MPa;

[0211] The quality of the reaction discharge from the fourth moving bed is similar to that of C9 + The mass ratio of heavy aromatics is 1:0.85;

[0212] C9 + Heavy aromatics composition: C10 aromatics mass percentage is 20%;

[0213] C9 + Mass space velocity of heavy aromatics: 2.0h -1 ;

[0214] Hydrogen to oil molar ratio: 3.

[0215] The reaction product at the outlet of the fixed bed reactor was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, with a total of 6 samples taken. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 58.1%, and the average xylene selectivity (mass) was 74.2%.

[0216] Comparative Example 1

[0217] A fixed bed reactor with a reactor volume of 50 ml was used, and 15 ml of solid acid aromatic methylation catalyst M1 was loaded. Toluene and alkylating agent methanol were fed into the fixed bed reactor to contact with the catalyst.

[0218] Alkylation conditions include:

[0219] Toluene to methanol molar ratio: 2.0;

[0220] Reaction temperature: 400°C;

[0221] Reaction pressure: 1.0MPa;

[0222] Hydrogen to oil molar ratio: 2.0;

[0223] Liquid volume space velocity of toluene: 4.0 hours -1 ;

[0224] The reaction product was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, for a total of 6 samples. The average toluene conversion rate (mass) after the initial reaction time of 72 hours was 33.5%, and the average xylene selectivity (mass) was 72.6%.

[0225] Comparative Example 2

[0226] Four fixed bed reactors connected in series were used, each reactor had a volume of 50 ml, and each reactor was filled with 15 ml of solid acid aromatic methylation catalyst M1.

[0227] Toluene flows from the first reactor to the fourth reactor in sequence, and the alkylation agent methanol is divided into four equal parts and introduced into four fixed bed reactors respectively, and is evenly mixed with toluene before entering the first reactor; before entering the second, third and fourth reactors, it is evenly mixed with the outlet flow of the previous reactor, and then contacted and reacted with the solid acid aromatic methylation catalyst in each reactor respectively.

[0228] The alkylation conditions include:

[0229] The molar ratio of toluene to the total amount of methanol introduced into the four reactors: 2.0;

[0230] Inlet temperature of the first to fourth reactors: 400°C;

[0231] Reaction pressure of the first to fourth reactors: 1.0 MPa;

[0232] The hydrogen to oil molar ratio of hydrogen and toluene introduced into the first reactor is 2.0;

[0233] Mass space velocity of toluene relative to the total mass of solid acid aromatic methylation catalyst: 4.0 h -1 ;

[0234] The reaction product was cooled by an air condenser and separated by a gas-liquid separator to obtain a liquid product. The liquid product was sampled and analyzed every 12 hours, for a total of 6 samples. The average toluene conversion rate (mass) after the initial reaction for 72 hours was 36.2%, and the average xylene selectivity (mass) was 76.1%.

[0235] By comparing the above examples and comparative examples, it can be seen that the present invention utilizes the product of benzene and / or toluene methylation with C9 + Heavy aromatics are directly used as the raw material for the transalkylation reaction. The aromatic methylation reaction and the heavy aromatics transalkylation reaction are coupled, which can significantly improve the conversion rate of toluene and the selectivity of xylene. At the same time, the use of multi-stage moving bed reactors for series reactions can be carried out without hydrogen or other carrier gases, which is conducive to further improving the economic efficiency of the reaction process.

[0236] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for producing xylene, characterized in that: The method is carried out in a xylene production device, which comprises n-stage moving bed reactors and a fixed bed reactor connected in series; each moving bed reactor is provided with a catalyst lifter, wherein n≥2; The method comprises: (1) feeding an aromatic hydrocarbon feedstock into a first-stage moving bed reactor to contact the aromatic hydrocarbon methylation catalyst loaded in the first-stage moving bed reactor to carry out an alkylation reaction; dividing the alkylation agent into n portions and feeding them into the first to n-stage moving bed reactors respectively; The reaction discharge from the first-stage moving bed reactor is used as the reaction feed of the second-stage moving bed reactor; the solid acid aromatic methylation catalyst in the first-stage moving bed reactor is sent to the second-stage moving bed reactor via a catalyst riser; the aromatic raw material is benzene and / or toluene; (2) The reaction discharge of the nth stage moving bed reactor, C9 + Heavy aromatics are fed into a fixed bed reactor and contacted with a solid acid transalkylation catalyst under hydrogenation conditions; The content of xylene in the reaction discharge of the n-stage moving bed reactor is 20-60wt%; the mass of the reaction discharge of the n-stage moving bed reactor is about the same as that of C9 + The mass ratio of heavy aromatics is 1:(0.5-2); (3) Separating the product obtained in step (2) to obtain xylene.

2. The method according to claim 1, wherein: The reaction output of the nth stage moving bed reactor includes xylene, optional benzene, and optional non-xylene alkylbenzene; Preferably, in the reaction discharge of the nth stage moving bed reactor, the content of xylene is 25-55wt%, and the content of non-xylene alkylbenzene is 45-75wt%.

3. The method according to claim 1 or 2, wherein: n is a positive integer selected from 3 to 30; Preferably, in step (1), the molar ratio of the total molar amount of the alkylating agent introduced into the n-stage moving bed reactor to the aromatic hydrocarbon feedstock is (0.2-3):1; Preferably, the ratio of the feed amount of the alkylating agent in the latter moving bed reactor to the feed amount of the alkylating agent in the former moving bed reactor is (0.5-1.2):

1.

4. The method according to any one of claims 1 to 3, wherein: The ratio of the SiO2 / Al2O3 molar ratio of the first solid acid zeolite molecular sieve contained in the solid acid aromatic methylation catalyst to the SiO2 / Al2O3 molar ratio of the second solid acid zeolite molecular sieve contained in the solid acid transalkylation catalyst is 2-15, preferably 2.5-12.

5. The method according to any one of claims 1 to 4, wherein: The method also includes: using C9 + The heavy aromatics exchange heat with the reaction discharge of the nth stage moving bed reactor and then feed it into the fixed bed reactor; Preferably, the temperature of the reaction feed of the first stage fixed bed reactor is 10-100°C lower than the temperature of the reaction discharge of the nth stage moving bed reactor, preferably 30-90°C.

6. The method according to any one of claims 1 to 5, wherein: In step (1), the alkylation reaction is carried out in the absence of a carrier gas; Preferably, relative to the total mass of the solid acid aromatic methylation catalyst loaded in the first to nth stage moving bed reactors, the mass space velocity of the aromatic feedstock is 1-15h -1 , preferably 2-10h -1 ; Preferably, the conditions of the first to nth stage moving bed reactors independently include: the reactor inlet temperature is 310-480°C, the pressure is 0.2-3.8MPa; Preferably, in the aromatic hydrocarbon raw material, the molar ratio of methyl group to benzene ring is 0.3-4:1, preferably 0.5-2:1; Preferably, the alkylating agent is selected from at least one of methanol, dimethyl ether, methyl bromide and carbon monoxide, preferably methanol.

7. The method according to any one of claims 1 to 6, wherein: The solid acid aromatic methylation catalyst comprises a first solid acid zeolite molecular sieve, a first binder and an optional first active component; the first solid acid zeolite molecular sieve is selected from at least one of MFI type, MEL type, FER type and TON type topological structure molecular sieves, preferably an MFI type topological structure molecular sieve; Preferably, the SiO2 / Al2O3 molar ratio of the first solid acid zeolite molecular sieve is 80-300, preferably 85-200; Preferably, the first active component is selected from at least one of rare earth elements and Group VIII metal elements, preferably at least one of La, Ce, Ni, Co, Rh, Pd and Pt, preferably La and Ni; Preferably, the first binder is aluminum oxide and / or silicon oxide; Preferably, relative to 100 parts by weight of the first solid acid zeolite molecular sieve, the content of the first binder is 15-400 parts by weight, and the content of the first active component is 0-80 parts by weight.

8. The method according to any one of claims 1 to 7, wherein: The quality of the reaction discharge of the n-stage moving bed reactor is + The mass ratio of heavy aromatics is 1:(0.6-1.5); Preferably, in step (2), the contacting conditions include: the reactor inlet temperature is 300-450°C, C9 + The mass space velocity of heavy aromatics is 1-8h -1 , pressure is 1-5MPa, hydrogen-to-oil molar ratio is 1-6; Preferably, the C9 + Heavy aromatics selected from C9 + Monocyclic aromatic hydrocarbons and / or condensed-ring aromatic hydrocarbons; Preferably, the C9 + Among heavy aromatics, C 10 The content of aromatic hydrocarbons is 1-75 wt%, preferably 5-60 wt%.

9. The method according to any one of claims 1 to 8, wherein: The solid acid transalkylation catalyst comprises a second solid acid zeolite molecular sieve, a second binder and an optional second active component; the second solid acid zeolite molecular sieve is selected from at least one of MFI type, MWW type, BEA type, MOR type, FAU type topological structure molecular sieve and BEA / MOR symbiotic molecular sieve, preferably at least one of BEA type, MOR type topological structure molecular sieve and BEA / MOR symbiotic molecular sieve, and more preferably BEA / MOR symbiotic molecular sieve; Preferably, the molar ratio of silicon oxide to aluminum oxide of the second solid acid zeolite molecular sieve is 10-100, preferably 15-80; Preferably, the second binder is at least one of aluminum oxide, silicon oxide, titanium oxide, zinc oxide and zirconium oxide; Preferably, the second active component is selected from at least one of Group VA metal elements and Group VIB metal elements, preferably including any one of Group VA metal elements and any one of Group VIB metal elements; Preferably, in the second active component, the mass ratio of the metal element of Group VA to the metal element of Group VIB is 10-1:1-10; Preferably, the Group VA metal element is selected from Sb and / or Bi; Preferably, the Group VIB metal element is selected from at least one of Cr, Mo and W; Preferably, relative to 100 parts by weight of the second solid acid zeolite molecular sieve, the content of the second binder is 15-200 parts by weight, and the content of the second active component is 2-160 parts by weight.

10. The method according to any one of claims 1 to 9, wherein: The xylene production device also includes a catalyst regenerator; The method further comprises: sending the deactivated solid acid aromatic methylation catalyst into a catalyst regenerator for regeneration treatment; Preferably, the separation in step (3) also produces dry gas and gas containing benzene, toluene, C9 + other streams of at least one of the heavy aromatics; Preferably, the method further comprises: returning the mixture containing benzene and / or toluene to step (1) for reuse, and / or returning C9 + The heavy aromatics are returned to step (2) for reuse.

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