A method for toluene shape-selective methylation reaction

Abstract

The present application relates to a kind of toluene, methylating agent is obtained in the production method of paraxylene concentration greater than 80% of dimethylbenzene with water vapor as medium to promote reaction.The main problem is that in the existing toluene shape selective methylation fixed bed reaction process, hydrogen and / or nitrogen are used as carrier gas to promote the reaction, which causes high fixed equipment investment, high device material requirements and other problems.The present application solves the problem by shape selective methylation of toluene and methylating agent, adding water vapor instead of hydrogen and / or nitrogen as carrier gas as medium to promote the reaction, and the catalyst para-selectivity is 80-95%, the laboratory life can reach 1000 hours, which can better solve the problem.The method has the advantages of high product purity, no complex separation, simple operation, low fixed asset investment, low material consumption, etc., and can be used for the industrial production of paraxylene.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing p-xylene by shape-selective methylation of toluene. Specifically, the method uses toluene and methanol as raw materials, and produces p-xylene by a fixed bed reaction process under the condition of not hydrogen but water. In the reaction process, water vapor is used as the driving medium, and no carrier gas such as hydrogen and nitrogen is needed, which can significantly save resources such as hydrogen and nitrogen, reduce the fixed asset investment of large supporting facilities such as hydrogen circulation compressor and air cooling in production, and effectively reduce the production investment cost of p-xylene. At the same time, the concentration of p-xylene in the product can reach 80-95%, the separation difficulty is low, the energy consumption is low, and the operation cost can be greatly reduced. BACKGROUND

[0002] China is a large country in textile production and consumption. As the main raw material for producing synthetic fibers, the market demand for p-xylene is extremely strong. Large-scale production of p-xylene is mainly realized through modern aromatic hydrocarbon combined devices. With the continuous progress of technology, the production threshold of p-xylene is gradually lowered. In the current environment where many private enterprises are rushing into the production of p-xylene, how to use limited resources to maximize and scale the production of p-xylene products at the lowest production cost will become a key factor in the competitiveness of p-xylene devices. In the traditional aromatic production process, dimethylbenzene is a thermodynamic mixture of o-, p-, and m-dimethylbenzene, and the concentration of p-xylene is only 24%. It needs to go through steps such as super-refining and multi-stage freezing to obtain p-xylene. The high operating cost and low p-xylene yield of this method will restrict its production prospects of p-xylene to some extent. Therefore, the method for producing p-xylene with high selectivity of p-isomer has attracted widespread attention.

[0003] Aromatic shape-selective methylation is a catalytic reaction of aromatic compounds with alkylating agents to produce p-xylene. The current research on toluene methylation reaction is mainly based on fixed bed process under hydrogen condition or fluidized bed process under non-hydrogen condition.

[0004] US patent US6504072 discloses a method for preparing p-xylene, which comprises reacting toluene with methanol in an alkylation reactor in the presence of a porous crystalline material catalyst. The reaction can be carried out in a fixed, mobile or fluidized reactor.

[0005] Patent ZL201611064254.5, applied for by Shaanxi Coal Chemical Technology Engineering Center Co., Ltd., mainly relates to a fluidized bed process for producing paraxylene from toluene and methanol. The main claim is that it employs a reaction configuration of multiple circulating fluidized bed reactors connected in series. All toluene feedstock enters from the first reactor, while methanol is divided into multiple streams. The methanol and toluene-containing materials are mixed evenly in a mixer at each reaction inlet before entering the respective reactors for reaction. Each fluidized bed reactor is equipped with a corresponding regenerator to ensure the stability and continuous regeneration of catalyst carbon deposition within the reactor. This technical solution improves methanol utilization by using segmented methanol feeding, achieving efficient mixing of methanol and toluene, and controlling the optimal amount of catalyst carbon deposition. However, this technical solution employs a complex process with multiple circulating fluidized bed reactors connected in series, making implementation difficult.

[0006] The patent ZL201710289046.3 applied for by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, discloses a rapid fluidized bed reactor, apparatus, and process for the co-production of low-carbon olefins from methanol and / or dimethyl ether with toluene and para-xylene. The main method is to control the mass transfer and reaction in each reactor by setting up multiple feed distributors in each reactor, and to coordinate and optimize the competition between the alkylation reaction and the MTO reaction, so as to improve the toluene conversion rate, para-xylene chirality, and low-carbon olefin selectivity.

[0007] The key technical problem that urgently needs to be solved in the industrialization process of toluene-methanol shape-selective methylation to produce p-xylene is how to improve the long-term stability of the catalyst and reduce the production cost of p-xylene while achieving a selective crystallization separation concentration of 80%.

[0008] As summarized above, while significant progress has been made in the technology of shape-selective methylation of aromatics in recent years, issues such as poor catalyst stability, high fixed asset investment, and high product production costs have hindered the industrialization of this technology. The present invention provides a fixed-bed process for the production of para-xylene using toluene shape-selective methylation, employing steam as the reaction medium and without the need for hydrogen or nitrogen as a carrier gas. This process features high catalyst stability and high selectivity for para-xylene products. Furthermore, because it eliminates the need for carrier gas recirculation, the reaction unit does not require hydrogen and / or nitrogen, saving on large fixed capital investments such as hydrogen compressors and air cooling systems. This results in low operating costs, and the large-scale production of this technology will significantly reduce the cost of para-xylene. Summary of the Invention

[0009] The technical problems to be solved by this invention are the poor catalyst stability, high fixed asset investment due to the need to complete the reaction under hydrogen or nitrogen atmosphere, and low concentration of p-xylene in the product in existing toluene shape-selective methylation reactions. This invention provides a new combined process for toluene shape-selective methylation to prepare p-xylene. This method has the advantages of using water vapor as the main driving medium during the reaction, simple fixed-bed process operation, minimal benzene generation during the reaction, wide operability, and high concentration of p-xylene in the product.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a toluene shape-selective methylation reaction method, wherein, under the condition of water vapor as the driving medium, an aromatic raw material containing toluene reacts with a methylating agent via an alkylation catalyst to generate a product mainly containing p-xylene, wherein the alkylation catalyst comprises, by weight, the following components:

[0011] 1) 20-90 parts of silica-rich molecular sieve;

[0012] 2) 10-80 parts of adhesive;

[0013] 3) 0.01 to 20 parts of metal or non-metal oxide modifier;

[0014] The metal or non-metal modifier is selected from one or more of groups IIA, IIIB, IVB, VIB, IVA, VA or VIII of the periodic table.

[0015] In the above technical solution, the water vapor is a reaction condition in which the driving medium exists, that is, the driving medium of the reaction also contains no more than 5% carrier gas (volume fraction), preferably no more than 2% carrier gas (volume fraction), and more preferably no carrier gas; the carrier gas is selected from one or at least one of hydrogen, nitrogen, argon and helium.

[0016] In the above technical solution, the reaction conditions of the shape-selective alkylation reactor are as follows: the total molar ratio of the toluene-containing aromatic feedstock to the methylating agent is 1:10 to 10:1, and / or the weight hourly space velocity is 0.2 to 5 hr. -1 The reaction conditions are as follows: and / or the reaction temperature is 300–600°C, and / or the reaction pressure is 0.01–3.0 MPa, and / or the molar ratio of water vapor to methylating agent in the reaction is 0.5–20. A preferred range is a total molar ratio of aromatic raw material to methylating agent of 1:2–5:1 and a weight hourly space velocity of 0.5–3 hr. -1 The reaction temperature is 400–550℃, the reaction pressure is 0.1–1.5 MPa, and the molar ratio of water vapor to methylating agent is 1–15. More preferably, the total molar ratio of aromatic raw material to methylating agent is 1:2–3:1, and the weight hourly space velocity is 0.5–1.5 hr. -1The reaction temperature is 450–520℃, the reaction pressure is 0.1–0.8 MPa, and the molar ratio of water vapor to methylating reagent is 5–12. The aromatic raw material containing toluene is at least one of benzene and toluene, preferably toluene.

[0017] In the above technical solution, the water generated in the reaction product can be recycled into the reactor or directly discharged outside the reaction area; the preferred solution is that the water generated in the reaction is separated into oil and water, stripped, purified to remove impurities, and then used as circulating water to enter the reaction system as a reaction medium to carry out heat and mass transfer in order to promote the reaction.

[0018] In the above technical solution, the methylating agent is at least one of methanol, methane, methylamine, and / or dimethyl ether, preferably methanol, and / or dimethyl ether, and more preferably methanol. Methanol can be introduced into the reactor in a continuous or segmented manner, preferably in a segmented manner. The alkylation reactor is at least one of a single-bed fixed-bed reactor, a multi-bed fixed-bed reactor, and a multi-stage series fixed-bed reactor, preferably at least one of a multi-bed fixed-bed reactor or a multi-stage series fixed-bed reactor.

[0019] This invention provides a shape-selective alkylation catalyst based on modified molecular sieves and its preparation method, comprising the following components by weight:

[0020] 1) 20-90 parts of silica-rich molecular sieve;

[0021] 2) 10-80 parts of adhesive;

[0022] 3) 0.01 to 20 parts of metal or non-metal oxide modifier;

[0023] The metal or non-metal modifier is selected from one or more of groups IIA, IIIB, IVB, VIB, IVA, VA or VIII of the periodic table.

[0024] In the above technical solution, the silica-alumina ratio of the outer layer of the silica-rich molecular sieve detected by Etch-XPS is greater than 150, preferably 200 to ∞, and more preferably 280 to ∞. The sieve is selected from at least one of ZSM-5, ZSM-11, ZSM-12, Silicate-I@ZSM-5, Silicate-I@Y, Silicate-I, and Silicate-II, or a mixture of the above molecular sieves; preferably ZSM-5, ZSM-11, Silicate-I@ZSM-5, and Silicate-I; more preferably at least one of ZSM-5 and Silicate-I@ZSM-5.

[0025] In the above technical solution, the molecular sieve is loaded with at least one of the following elements by weight percentage: Mg, Ca, Ba, Zr, Ti, Co, Mo, Ni, Pt, Pd, La, Ce, Cu, Fe, Si, P, Sn, Pb, etc., with a preferred weight percentage range of 0.05 to 15%, and a more preferred range of 0.1 to 10%.

[0026] In the above technical solution, the binder used for the catalyst is at least one of silica, silica sol, titanium dioxide, alumina, and diatomaceous earth, with a weight percentage of 10-80%, preferably 20-70%, and more preferably 40-60%.

[0027] In the above technical solution, water vapor is used as a medium to drive heat and mass transfer in the reaction process. The molar ratio of water vapor to alkylating reagent is preferably 5-15. The reaction medium contains at least 95% water vapor by weight, preferably at least 98% water vapor, and more preferably water vapor without carrier gas. The carrier gas mentioned by those skilled in the art generally refers to one or at least one of hydrogen, nitrogen, argon and helium.

[0028] In this invention, all toluene shape-selective methylation reactions can be driven by steam as the heat transfer medium. No carrier gas such as hydrogen or nitrogen is required during the reaction, which saves hydrogen resources and is beneficial for the capacity expansion and modification of other hydrogen-consuming units in the aromatic hydrocarbon complex.

[0029] Generally speaking, in chemical production processes, hydrogen is mostly used as the carrier gas for processes that require carrier gas transport, while nitrogen is used in small quantities. This is because hydrogen has the characteristics of small relative molecular weight, large thermal conductivity, and low viscosity; while nitrogen has a larger relative molecular mass, small diffusion coefficient, and small thermal conductivity. Nitrogen is weaker than hydrogen in terms of heat and mass transfer in reaction and separation processes. However, hydrogen is flammable and explosive, so the safety requirements for equipment and operation are high during its use.

[0030] However, in the process of using hydrogen, such as the recycling of hydrogen in the reaction process, a hydrogen recycling compressor is often required. If hydrogen is used in a one-way process, a PSA processing system is required. The fixed asset investment, daily use and maintenance of these large-scale equipment all require a lot of financial, material and human resources. In addition, under hydrogen-containing conditions, the alkylation reaction process will inevitably produce a large number of side reactions such as methanol self-decomposition and hydrocarbonation. The acidic gaseous impurities produced will often cause serious damage to the hydrogen compressor and PSA system.

[0031] To address the aforementioned issues, this invention employs water vapor instead of hydrogen or nitrogen to drive the shape-selective alkylation reaction. Due to the inhibitory effect of water on the strong Brønsted acid active sites of the catalyst, the probability of methanol side reactions is reduced, improving methanol utilization while simultaneously decreasing the catalyst deactivation rate and extending catalyst lifespan. Furthermore, using water vapor as the heat and mass transfer medium, and through oil-water separation, gaseous olefins can be efficiently separated from circulating water, avoiding the difficulties in separating small-molecule gaseous olefins during hydrogen circulation and their accumulation within the reaction system.

[0032] X-ray etching photoelectron spectroscopy (Etch-XPS) was performed using a PHI 5000C (XPS) instrument from PHI Corporation, USA. Etching was conducted with X-rays for 5–10 s, and the elemental composition of the molecular sieve surface was analyzed. The operating conditions were an aluminum / magnesium target, a high voltage of 14 kV, a power of 250 W, and a vacuum better than 1 × 10⁻⁶. -8 Torr. The silicon-to-aluminum ratio calculated from the elemental composition obtained before etching is the surface silicon-to-aluminum ratio, and the silicon-to-aluminum ratio calculated from the elemental composition obtained after etching is the bulk silicon-to-aluminum ratio.

[0033] During the reaction process, the specific expressions for each indicator are as follows:

[0034]

[0035]

[0036] The present invention will be further illustrated below through examples. Detailed Implementation

[0037]

Comparative Example 1

[0038] The purchased ammonium-type ZSM-5, designated D1-A, had a silica-to-alumina ratio of 70 according to chemical analysis. Etching and XPS analysis revealed a bulk silica-to-alumina ratio of 67.8 and a surface silica-to-alumina ratio of 71.1.

[0039] Take 40g of D1-A ammonium type raw powder, add 25g of silica sol (containing 40% SiO2 by weight) and 6ml of water, knead and extrude into strips, dry and calcine at 500℃ for 2 hours to obtain the unselective shaped catalyst matrix D1-B.

[0040] 45 g of catalyst precursor D1-B was added to a solution of 150 mL cyclohexane and 14.5 g phenylmethyl polysiloxane. The cyclohexane was removed by open distillation in an oil bath at 90 °C. The residue after evaporation was heated to 500 °C in a muffle furnace, held for 3 hours, and then naturally cooled to obtain catalyst D1-C with 10% SiO2 external surface liquid phase deposition modification.

[0041] The 40g of catalyst D1-C obtained above was added to a mixed solution of chloroplatinic acid and tin nitrate. After static impregnation for 2 hours, it was dried, heated to 550℃ in a muffle furnace, held for 3 hours, and then naturally cooled to obtain the 10%SiO2-0.01%Pt-0.2%Sn catalyst D1-D.

[0042] A conventional fixed-bed reactor was used, with 10g of catalyst D1-D loaded. For evaluation, liquid toluene and methanol were mixed in a molar ratio of 2:1, stirred thoroughly, vaporized, and then introduced into the top of the reactor. After dispersion and preheating through upper ceramic balls, the mixture entered the catalyst bed. No hydrogen or nitrogen was introduced during the reaction, at a weight hourly space velocity (WHSV) of 2.0 h⁻¹. -1 The reaction was carried out at a temperature of 460℃, a pressure of 0.5MPa, and a molar ratio of pure water to methanol of 5. The reaction products were separated by passing through a gas-liquid separator from the bottom of the reactor after cooling. The liquid products were sampled and analyzed, and their technical indicators are listed in Table 1.

[0043] [Comparative Example 2]

[0044] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 3:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. Hydrogen gas was introduced during the reaction, and the reaction was carried out at a weight hourly space velocity (WHSV) of 3.5 h⁻¹. -1 The reaction was carried out at a temperature of 430℃, a pressure of 1.5MPa, and a hydrogen to methanol molar ratio of 4. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0045] [Comparative Example 3]

[0046] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 2:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. Nitrogen gas was introduced during the reaction, and the reaction was carried out at a weight hourly space velocity (WHSV) of 5.0 h⁻¹. -1 The reaction was carried out at a temperature of 400℃, a pressure of 0.5MPa, and a nitrogen to methanol molar ratio of 2. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0047] [Comparative Example 4]

[0048] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 3:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. During the reaction, hydrogen gas with a water vapor content of 10% was introduced at a weight hourly space velocity of 5.0 h⁻¹. -1 The reaction was carried out at a temperature of 500℃, a pressure of 0.5MPa, and a hydrogen to methanol molar ratio of 20. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0049] [Comparative Example 5]

[0050] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 2:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. Nitrogen gas with a water vapor content of 20% was introduced during the reaction, and the reaction was carried out at a weight hourly space velocity of 0.5 h⁻¹. -1 The reaction was carried out at a temperature of 500℃, a pressure of 0.5MPa, and a nitrogen to methanol molar ratio of 3. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0051]

Example 1

[0052] 500g of water glass (containing 26.1% SiO2 and 7.4% Na2O by weight) was mixed with 350g of water until homogeneous. Then, 15g of aluminum sulfate octadechydrate, 20g of 98% concentrated sulfuric acid, and 400g of water were dissolved and added to the water glass mixture. After stirring for 15 minutes, the mixture was transferred to a stainless steel reactor. 250ml of concentrated ammonia and 1.5g of ethylamine (65% by weight) were then added. The mixture was crystallized at 70℃ for 5 hours to obtain the crystallized precursor S1-A.

[0053] 100g of water glass (containing 25.8% SiO2 and 7.3% Na2O by weight) was mixed with 50g of water until homogeneous. Then, 0.5g of aluminum sulfate octadecylhydrate, 40g of liquid ammonia, 10g of triethylamine solution, 600g of water, and all of the crystallization precursor S1-A were added to the water glass. After stirring for 2 hours, the mixture was transferred to a stainless steel reactor and sealed. Crystallization was carried out at 180℃ for 60 hours. The crystallized product was then filtered out, washed several times with water, and dried to obtain molecular sieve S1-B, which was identified as ZSM-5 molecular sieve by X-ray phase analysis.

[0054] Etching and XPS analysis revealed that the bulk silicon-to-aluminum ratio of molecular sieve S1-B was 67.8, and the surface silicon-to-aluminum ratio was 162.5.

[0055]

Example 2

[0056] 100g of tetraethyl orthosilicate was mixed with 350g of water. Then, 0.7g of sodium aluminate, 10g of sodium hydroxide and 10g of tetrabutylammonium hydroxide solution were dissolved in 400g of water and added to the tetraethyl orthosilicate solution. After stirring for 15 minutes, the mixture was transferred to a stainless steel reactor and crystallized at 90℃ for 5 hours to obtain the crystallized precursor S2-A.

[0057] Add 320g of water to 500g of silica sol (SiO2 content 40% by weight) and mix well. Then add 7.5g of sodium aluminate, 15g of tetrabutylammonium bromide, 600g of water and all of the crystallization precursor S1-A to the silica sol solution. After stirring for 2 hours, transfer to a stainless steel reactor and crystallize at 170℃ for 50 hours. Then filter out the crystallized product, wash it several times with water and dry it to obtain molecular sieve S2-B, which is identified as ZSM-11 molecular sieve by X-ray phase analysis.

[0058] Etching and XPS analysis revealed that the bulk silica-to-alumina ratio of the molecular sieve was 80.3, and the surface silica-to-alumina ratio was 220.5.

[0059]

Example 3

[0060] Sodium molecular sieve S1-B prepared in Example 1 was exchanged with ammonium nitrate solution at 95°C to obtain ammonium molecular sieve. 40g of ammonium molecular sieve S1-B was added to 25g of alumina, 3.5g of concentrated nitric acid and 26ml of water, kneaded and extruded into strips, dried and calcined at 500°C for 2 hours to obtain the unselective shaped catalyst parent material S1-C.

[0061] 45 grams of catalyst precursor S1-C were added to an ammonium phosphate solution and dynamically impregnated for 4 hours. After drying overnight, the temperature was raised to 550°C in a muffle furnace and maintained for 3 hours before natural cooling to obtain catalyst S1-D modified with 10% P2O5.

[0062] The 40g of catalyst S1-D obtained above was added to a mixed solution of magnesium acetate and nickel nitrate. After static impregnation for 2 hours, it was dried, heated to 550℃ in a muffle furnace, held for 3 hours, and then naturally cooled to obtain the 10%P2O5-6%MgO-3.5%NiO catalyst S1-E.

[0063]

Example 4

[0064] A conventional fixed-bed reactor was used, loaded with 10g of catalyst S1-E. For evaluation, liquid toluene and methanol were mixed in a molar ratio of 2:1, stirred thoroughly, vaporized, and then introduced into the top of the reactor. After dispersion and preheating through upper ceramic balls, the mixture entered the catalyst bed. No hydrogen or nitrogen was introduced during the reaction, at a weight hourly space velocity (WHSV) of 0.5 h⁻¹. -1The reaction was carried out at a temperature of 460℃, a pressure of 0.5MPa, and a molar ratio of pure water to methanol of 6. The reaction products were separated by passing through a gas-liquid separator from the bottom of the reactor after cooling. The liquid products were sampled and analyzed, and their technical indicators are listed in Table 1.

[0065]

Example 5

[0066] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 3:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. During the reaction, water vapor with a hydrogen content of 2% was introduced at a weight hourly space velocity of 1.0 h⁻¹. -1 The reaction was carried out at a temperature of 480℃, a pressure of 0.5MPa, and a water to methanol molar ratio of 4. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0067]

Example 6

[0068] The catalyst S1-E prepared in Example 3 was mixed with liquid toluene and methanol in a molar ratio of 3:1. After being stirred evenly, the mixture was vaporized and introduced into the top of the reactor. After being dispersed and preheated by the upper ceramic balls, it entered the catalyst bed. During the reaction, water vapor with a nitrogen content of 5% was introduced at a weight hourly space velocity of 3.0 h⁻¹. -1 The reaction was carried out at a temperature of 520℃, a pressure of 0.05MPa, and a water-to-methanol molar ratio of 3. The reaction products were cooled and passed through a gas-liquid separator from the bottom of the reactor for separation. The liquid products were sampled and analyzed. The technical indicators are listed in Table 1.

[0069]

Example 7

[0070] Sodium molecular sieve S2-B prepared in Example 2 was exchanged with ammonium nitrate solution at 95°C to obtain ammonium molecular sieve. 40g of ammonium molecular sieve S2-B was added to 15g of alumina, 5g of titanium dioxide, 3.5g of concentrated nitric acid and 26ml of water. The mixture was kneaded, extruded into strips, dried and calcined at 500°C for 2 hours to obtain the unselective shaped catalyst matrix S2-C.

[0071] 45 grams of catalyst precursor S2-C were added to an ammonium phosphate solution and dynamically impregnated for 4 hours. After drying overnight, the temperature was raised to 550°C in a muffle furnace and maintained for 3 hours before natural cooling to obtain catalyst S2-D modified with 15% P2O5.

[0072] The 40g of catalyst S2-D obtained above was added to a mixed solution of calcium acetate and nickel nitrate. After static impregnation for 2 hours, it was dried, heated to 550℃ in a muffle furnace, held for 3 hours, and then naturally cooled to obtain the 15%P2O5-3%CaO-3.5%NiO catalyst S2-E.

[0073]

Example 8

[0074] A conventional fixed-bed reactor was used, loaded with 10g of catalyst S2-E. For evaluation, liquid toluene and methanol were mixed in a molar ratio of 2:1, stirred thoroughly, vaporized, and then introduced into the top of the reactor. After dispersion and preheating through upper ceramic balls, the mixture entered the catalyst bed. No hydrogen or nitrogen was introduced during the reaction, at a weight hourly space velocity (WHSV) of 1.5 h⁻¹. -1 The reaction was carried out at a temperature of 460℃, a pressure of 0.5MPa, and a molar ratio of pure water to methanol of 5. The reaction products were separated by passing through a gas-liquid separator from the bottom of the reactor after cooling. The liquid products were sampled and analyzed, and their technical indicators are listed in Table 1.

[0075] Table 1. Reaction evaluation results for different catalysts

[0076] Experiment no. Catalyst Toluene conversion, % Para selectivity, % Stability, h Comparative example 1 D1-D 22.4 45.1 500 Comparative example 2 S1-E 20.8 72.3 120 Comparative example 3 S1-E 25.1 70.6 80 Comparative example 4 S1-E 18.3 81.3 260 Comparative example 5 S1-E 27.4 77.2 200 Example 4 S1-E 28.3 95.2 1000 Example 5 S1-E 22.9 85.4 1000 Example 6 S1-E 20.8 86.2 800 Example 8 S2-E 25.8 80.9 500

Claims

1. A method for toluene shape-selective methylation reaction, characterized in that, Under conditions where water vapor is the driving medium, an aromatic feedstock containing toluene reacts with a methylating agent via an alkylation catalyst to produce a product mainly containing p-xylene. The alkylation catalyst, by weight, comprises the following components: 1) 20–90 parts of silica-rich molecular sieve; 2) 10-80 parts of adhesive; 3) 0.01–20 parts of metal or non-metal oxide modifier; The metal or non-metal modifier is selected from at least one of Mg, Ca, Ni and P; The silicon-rich molecular sieve is ZSM-5 and / or ZSM-11; The binder is titanium dioxide and / or aluminum oxide; The methylating agent is methanol; The Etch-XPS analysis of the outer layer of the silica-rich molecular sieve showed a silica-to-alumina ratio greater than 150. The reaction is carried out in a fixed-bed reactor; The propellant also contains carrier gas with a volume fraction not exceeding 5%.

2. The toluene shape-selective methylation reaction method according to claim 1, characterized in that... The propellant also contains carrier gas with a volume fraction not exceeding 2%.

3. The toluene shape-selective methylation reaction method according to claim 2, characterized in that... The propellant does not contain carrier gas.

4. The toluene shape-selective methylation reaction method according to claim 1, characterized in that... The carrier gas is selected from at least one of hydrogen, nitrogen, argon and helium.

5. The toluene shape-selective methylation reaction method according to claim 1, characterized in that: The reaction conditions are as follows: the total molar ratio of the aromatic raw material containing toluene to the methylating agent is 1:10 to 10:1, and / or the reaction temperature is 300 to 600°C, and / or the reaction pressure is 0.01 to 3.0 MPa, and / or the molar ratio of water vapor to the methylating agent in the reaction is 0.5 to 20.

6. The toluene shape-selective methylation reaction method according to claim 1, characterized in that... Water produced in the reaction can be recycled back into the reactor or discharged directly outside the reaction zone.

7. The toluene shape-selective methylation reaction method according to claim 1, characterized in that... The Etch-XPS analysis of the outer layer of the silica-alumina ratio of the silica-rich molecular sieve was 200 to ∞.

8. The toluene shape-selective methylation reaction method according to claim 7, characterized in that... The Etch-XPS analysis of the outer layer of the silica-rich molecular sieve showed a silica-to-alumina ratio of 280 to ∞.

9. The toluene shape-selective methylation reaction method according to claim 1, characterized in that... The molecular sieve is loaded with at least one of the elements Mg, Ca, Ni and P, with a weight percentage of 0.01 to 20%.

10. The toluene shape-selective methylation reaction method according to claim 1, characterized in that: The methylating agent can be introduced into the reactor either as a whole or in stages, using at least one of a single-bed fixed-bed reactor, a multi-bed fixed-bed reactor, or a multi-stage series fixed-bed reactor.

11. The toluene shape-selective methylation reaction method according to claim 10, characterized in that: The methylating agent is fed into the alkylation reactor in stages.

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