Method for increasing yield of xylene through methylation of toluene and methanol

Abstract

The invention discloses a method for increasing the yield of xylene through methylation of toluene and methanol. The method comprises the following steps: (1) mixing toluene and methanol, feeding the mixture into a first reaction zone, contacting the mixture with an aromatic methylation catalyst in the presence of hydrogen, and carrying out a gas-phase methylation reaction to obtain a first material flow; and (2) introducing the first material flow into a second reaction zone, contacting the first material flow with a methyl transfer catalyst in the presence of hydrogen, obtaining a second material flow through a liquid-phase methyl transfer reaction, and separating to obtain a xylene product. The method provided by the invention can improve the selectivity of xylene and the conversion rate of toluene.

Description

Technical Field

[0001] The invention relates to the technical field of xylene production, and in particular to a method for increasing the production of xylene by methylating toluene with methanol. Background Art

[0002] Xylene is an important basic organic raw material and is widely used in the fields of medicine, resin, oil products, etc. Xylene has three isomers, namely o-xylene, p-xylene and m-xylene. Among them, p-xylene has the largest market demand and is mainly used to prepare terephthalic acid and dimethyl terephthalate, and then produce polyethylene terephthalate. At present, the production method of p-xylene is to separate p-xylene from the isomer mixture with similar boiling points by adsorption separation or crystallization separation technology from the thermodynamically balanced mixed xylene generated by catalytic reforming of naphtha. The remaining o-xylene and m-xylene are further separated by isomerization technology, and the mixed xylene obtained by isomerization continues to be used as the raw material for p-xylene separation. At present, toluene disproportionation and transalkylation technology is the most widely used xylene production increase technology. This technology is based on toluene and carbon nine / carbon ten aromatics (C9 / C 10 A) is used as raw material to produce benzene and xylene through transalkylation reaction and hydrodealkylation reaction (Chemical Technology and Economics, 2006, 24(2):13-16.).

[0003] Toluene methanol methylation technology is a process in which methanol is used as a methylating agent to react with toluene to produce xylene and water. Theoretically, one mole of toluene can produce one mole of xylene, which improves the utilization rate of toluene and saves petroleum resources. As the aromatics market is affected by the economic environment, the prices of various products will fluctuate significantly. Among them, in the context of the likely decline in benzene prices, the toluene methanol methylation technology that produces more xylene without benzene has received great attention. Considering the changing trend of market demand and prices for aromatics products, increasing xylene production and reducing benzene production has become the main goal of production enterprises. Toluene methylation technology has become one of the process technologies for effectively adjusting the product structure of benzene and xylene. In 2012, the MTX toluene methanol methylation technology for producing xylene developed by Sinopec was successfully put into operation at the 200,000 tons / year industrial demonstration unit of Yangzi Petrochemical, marking the first industrialization of this technology (Petroleum Refining and Chemical Industry, 2014, 45(9):1.). However, in the process of toluene methanol methylation, in addition to the main product xylene, due to the existence of excessive methylation side reactions, by-products such as trimethylbenzene and tetramethylbenzene are also generated, making the single-pass xylene selectivity of the general toluene methanol methylation reaction only about 70-80% (Chemical Reaction Engineering and Technology, 2019, 35(5): 402-409.). CN 111068756 A discloses a toluene alkylation molecular sieve catalyst and its application. The molecular sieve catalyst containing rare earth elements and group VIII elements can increase the toluene conversion rate to 35% to 40%, and the xylene selectivity is 70% to 80%. CN 103772129 A discloses a technical solution in which a plurality of fixed bed reactors are connected in series, fresh toluene raw materials and methylating agents are preheated and supplied to respective reactors, each reactor is filled with the same or different amounts of catalysts, and the reaction materials pass through each bed layer in sequence under certain process conditions, and the logistics flowing out of the outlet of each fixed bed reactor, except for the last reactor, flow into the inlet of the next fixed bed reactor respectively, mainly solving the problems of rapid catalyst deactivation, and low toluene conversion rate and methyl utilization rate. CN 111072445 A discloses a reaction separation method, which solves the problem of high content of heavy aromatic byproducts in toluene methanol methylation technology and improves xylene selectivity.

[0004] In summary, the existing toluene methanol methylation technology has the problem of low xylene selectivity, and it is necessary to develop a toluene methanol methylation technology with high conversion rate and high selectivity to increase xylene production. Summary of the invention

[0005] The invention aims to solve the problem of low xylene selectivity in the existing process of producing xylene by toluene methanol methylation, and provides a method for increasing xylene production by toluene methanol methylation. The method can improve xylene selectivity and toluene conversion rate.

[0006] The present invention provides a method for increasing the production of xylene by methylating toluene and methanol, comprising the following steps:

[0007] (1) mixing toluene and methanol into a first reaction zone, contacting with an aromatic methylation catalyst under hydrogen conditions, and causing a gas phase methylation reaction to obtain a first stream;

[0008] (2) introducing the first stream described in step (1) into a second reaction zone, contacting it with a methyl transfer catalyst under hydrogenation conditions, obtaining a second stream through a liquid phase methyl transfer reaction, and separating to obtain a xylene product.

[0009] Furthermore, the molar ratio of toluene to methanol in step (1) is 1:1 to 2:1.

[0010] Furthermore, the aromatic methylation catalyst in step (1) can be any toluene methanol methylation catalyst disclosed in the prior art, such as patents / documents CN103664492A, CN101885662B, Chemical Reaction Engineering and Technology, 2019, 35(5): 8-13, etc. As an example, the aromatic methylation catalyst in step (1) can be the following catalyst: the catalyst comprises a carrier and an active component, wherein the carrier comprises a molecular sieve and a binder, and the molecular sieve is selected from at least one of MFI molecular sieve, BETA molecular sieve, and MOR molecular sieve, preferably MFI molecular sieve.

[0011] Furthermore, the active component of the aromatic methylation catalyst in step (1) is selected from at least one of VIII transition metal elements, preferably at least one of iron, cobalt and nickel; wherein the mass content of the active component is 0.1 to 40% in terms of oxide, based on the weight of the aromatic methylation catalyst.

[0012] Furthermore, the aromatic methylation catalyst described in step (1) can be prepared by conventional methods in the art, for example, ammonium molecular sieve powder is mixed with a binder (selected from at least one of alumina, pseudo-boehmite, and silica sol), and the carrier is obtained by molding, drying and calcining, and the carrier loads the active component to obtain an aromatic methylation catalyst. The ammonium molecular sieve is at least one of MFI molecular sieve, BETA molecular sieve, and MOR molecular sieve, preferably MFI molecular sieve. The drying and calcining conditions can adopt conventional processing conditions in the art, such as a drying temperature of 90 to 150°C and a drying time of 1 to 10 hours; a calcining temperature of 450 to 550°C and a calcining time of 1 to 10 hours.

[0013] Furthermore, the hydrogenation conditions of step (1) are as follows: the molar ratio of toluene to hydrogen is 0.1 to 2:1.

[0014] Furthermore, the gas phase methylation reaction conditions in step (1) include: a temperature of 400 to 550° C., a pressure of 0.5 to 1 MPa, and a toluene feed mass space velocity of 2 to 10 h -1 .

[0015] Furthermore, the first stream obtained in step (1) is preferably treated with an adsorbent before being introduced into the second reaction zone.

[0016] Furthermore, after the first stream obtained in step (1) is separated from oil and water, the oil phase is treated with an adsorbent at a treatment temperature of 100 to 200° C., and the treated first stream is then introduced into the second reaction zone. The purpose of the adsorption treatment is to adsorb the dissolved trace water and the very small amount of oxygen-containing compounds generated during the methylation reaction.

[0017] Furthermore, the adsorbent may be an adsorbent commonly used in the prior art, for example, the adsorbent may be selected from at least one of polyester, kaolin, amorphous silica-alumina or acidic molecular sieve.

[0018] Furthermore, the methyl transfer catalyst in step (2) comprises BETA / MOR symbiotic molecular sieve and a binder, wherein the mass content of the binder in the methyl transfer catalyst is 20% to 50%, and the mass content of the BETA / MOR symbiotic molecular sieve in the methyl transfer catalyst is 50% to 80%.

[0019] Furthermore, in step (2), the BETA / MOR symbiotic molecular sieve has a surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio is 0.1 to 0.8.

[0020] Furthermore, the BETA / MOR intergrowth molecular sieve in step (2) has the following schematic chemical composition, in terms of molar ratio: nSiO2 / Al2O3, wherein 10≤n≤100, preferably 20≤n≤50.

[0021] Furthermore, in the BETA / MOR symbiotic molecular sieve of step (2), the mass ratio of BETA / MOR is 10 / 90 to 90 / 10, preferably 25 / 75 to 75 / 25.

[0022] Further, preferably, the surface aluminum S of the molecular sieve in the BETA / MOR symbiotic molecular sieve in step (2) SAR With the aluminum inside the molecular sieve SAR The atomic ratio is 0.5 to 0.8.

[0023] Furthermore, the specific surface area of ​​the BETA / MOR symbiotic molecular sieve is 400 to 550 m 2 / g, pore volume is 0.10~0.30cm3 / g.

[0024] Furthermore, the method for preparing the BETA / MOR symbiotic molecular sieve described in step (2) comprises:

[0025] (a) mixing a silicon source, an aluminum source, a first template T1, a second template T2, an alkali source and water, adjusting the pH to 9-13, and then adding MOR seed crystals to obtain a molecular sieve precursor;

[0026] (b) The molecular sieve precursor described in (a) is first subjected to a first-stage hydrothermal crystallization, and then the temperature is increased to perform a second-stage hydrothermal crystallization to obtain the BETA / MOR symbiotic molecular sieve.

[0027] Furthermore, the MOR seed crystals in step (a) are MOR molecular sieve seed crystals having a silicon-aluminum molar ratio (SiO2 / Al2O3) of 15 to 25.

[0028] Furthermore, the silicon source in step (a) is selected from water glass, preferably water glass containing 15 to 40 wt% SiO2 and a modulus of 3.0 to 3.5; the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, boehmite, sodium aluminate, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide, preferably sodium aluminate and / or aluminum sulfate; the alkali source is selected from ammonia water and / or alkaline hydroxide, preferably NaOH; the first template is tetraethylammonium hydroxide (TEAOH) and / or tetraethylammonium bromide (TEABr); and the second template is sodium fluoride.

[0029] Furthermore, the silicon source, aluminum source, first template T1, second template T2, alkali source and water in step (a) are mixed in a molar ratio of (1-6) alkali source: (30-55) SiO2: Al2O3: (8-15) T1: (100-1000) H2O: (2-8) T2 to form a sol.

[0030] Furthermore, the mass content of the MOR seed crystals in the molecular sieve precursor in step (a) is 20% to 55%.

[0031] Furthermore, in step (b), the hydrothermal crystallization conditions of the first stage are: 100-130° C. hydrothermal crystallization for 24-48 hours; and the hydrothermal crystallization conditions of the second stage are 160-200° C. hydrothermal crystallization for 24-48 hours.

[0032] Furthermore, the method for preparing the transmethylation catalyst described in step (2) comprises the following steps:

[0033] (i) mixing BETA / MOR symbiotic molecular sieve powder and a binder, mixing them uniformly, and then molding, drying and calcining to obtain a catalyst precursor;

[0034] (ii) treating the catalyst precursor with water vapor containing ammonia to obtain a methyl transfer catalyst.

[0035] Furthermore, the molding in step (i) is preferably extrusion molding, and during extrusion molding, a molding aid can be added as needed, such as at least one of sesbania powder and cellulose. The amount of the binder added accounts for 20% to 50% of the total mass of the molecular sieve powder and the binder. The amount of the molding aid added accounts for 2% to 5% of the total mass of the molecular sieve powder and the binder.

[0036] Furthermore, the binder in step (i) is selected from at least one of alumina, pseudo-boehmite and silica.

[0037] Furthermore, in step (i), the drying temperature is 90-150° C. and the drying time is 1-10 hours; and the calcination temperature is 350-550° C. and the calcination time is 1-10 hours.

[0038] Furthermore, the step (ii) of treating the catalyst precursor with ammonia-containing water vapor includes: contacting the catalyst precursor with an ammonia-containing aqueous solution under conditions that satisfy the vaporization of ammonia and water; preferably, the ammonia content of the aqueous solution containing ammonia is 5% to 25%, more preferably 10% to 20%. Preferably, the contact conditions include: a temperature of 200 to 600°C, preferably 250 to 550°C; a time of 1 to 12 hours, preferably 2 to 10 hours; and a mass space velocity of the aqueous solution containing ammonia of 0.5 to 10 h -1 , preferably 1 to 6 hours -1 .

[0039] Further, the acid distribution value obtained by NH3-TPD characterization of the methyl transfer catalyst in step (2) is A, where A is W acid With S acid The ratio of and A is 1 to 2; where W acid is the amount of NH3 desorbed at a desorption temperature of 100-350°C, S acid It is the amount of NH3 desorbed at a desorption temperature of 350-600℃.

[0040] Furthermore, in the step (2), the second logistics is separated to obtain fractions including dry gas, benzene, toluene, xylene, trimethylbenzene and tetramethylbenzene.

[0041] Furthermore, preferably, the toluene, trimethylbenzene and tetramethylbenzene obtained after separation of the second logistics are returned to the first reaction zone and / or the second reaction zone, which can further improve the xylene selectivity.

[0042] Furthermore, in step (2), the liquid phase methyl transfer reaction conditions include: temperature of 200-300°C, pressure of 4-6 MPa, and mass space velocity of aromatic feed of 1-4 h -1 , the molar ratio of aromatics to hydrogen is 0.5 to 2:1.

[0043] Compared with the prior art, the advantages of the present invention are:

[0044] The present invention introduces an alkyl transfer reaction on the basis of the toluene methanol methylation reaction to convert the C9 / C 10 Aromatics are further converted into xylenes. Compared with the simple toluene methanol methylation technology, the xylene selectivity of this technology is significantly improved. In addition, the alkyl transfer unit adopts a hydrogen liquid phase methyl transfer reaction and a specific methyl transfer catalyst. Compared with the traditional hydrogen gas phase alkyl transfer technology, it not only has excellent catalytic performance, but also has a simple reaction process, low material consumption and equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the XRD pattern of the BETA / MOR symbiotic molecular sieve obtained in Example 1;

[0046] Figure 2 This is the SEM image of the BETA / MOR symbiotic molecular sieve obtained in Example 1. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0048] The raw materials used in the examples and comparative examples of the present invention are commercially available and have an analytical purity (AR).

[0049] In the present invention, the aluminum distribution value obtained by XPS-argon ion etching technology is S, S is S SAR with I SAR The ratio of SAR is the atomic percentage of aluminum on the surface of the molecular sieve obtained by direct XPS testing, I SAR It is the atomic percentage of aluminum inside the molecular sieve tested by XPS after argon ion etching, and the argon ion etching depth is 20-50nm.

[0050] In the present invention, ammonia temperature-programmed desorption (NH3-TPD) is carried out on an AutoChem2920 fully automatic temperature-programmed chemical adsorption instrument, and a thermal conductivity detector is used. The desorption peak located at 150-350°C (Peak I) corresponds to NH3 adsorption at a weak acid site, and the other desorption peak located in the high temperature region of 350-600°C (Peak II) corresponds to NH3 adsorption at a strong acid site. The peak area of ​​Peak I / Peak area of ​​Peak II ratio A is 1-2.

[0051] In the context of this specification, the so-called specific surface area refers to the total area of ​​a sample per unit mass, including the internal surface area and the external surface area. Non-porous samples only have external surface area, such as silicate cement, some clay mineral powders, etc.; porous and porous samples have external surface area and internal surface area, such as asbestos fiber, diatomaceous earth and molecular sieves, etc. In the context of this specification, the so-called pore volume refers to the volume of pores per unit mass of porous materials. The so-called total pore volume refers to the volume of all pores per unit mass of molecular sieves (generally only pores with a pore diameter of less than 50 nanometers are counted). The pore structure parameters of molecular sieves, such as total pore volume and total specific surface area, are measured by physical adsorption instrument (such as TriStar 3000 physical adsorption instrument of Mack Instruments, USA) to obtain nitrogen physical adsorption and desorption isotherms, and then calculated by BET method and t-plot method. The experimental conditions for molecular sieves are: measurement temperature -196°C, and the molecular sieves are vacuum pretreated at 300°C for 10 hours before measurement.

[0052] In the context of this specification, including in the following examples and comparative examples, the model of the scanning electron microscope (SEM) of the molecular sieve is S-4800II field emission scanning electron microscope.

[0053] In the context of this specification, the structure of the molecular sieve is determined by an X-ray diffraction spectrum (XRD), and the X-ray diffraction spectrum (XRD) is determined by an X-ray powder diffractometer, including in the following embodiments and comparative examples, the model of the X-ray powder diffractometer of the molecular sieve is a Panalytical X PERPRO X-ray powder diffractometer, the physical phase of the sample is analyzed, CuKα ray source nickel filter, 2θ scanning range 5 to 50°, operating voltage 40KV, current 40mA, scanning rate 10° / min.

[0054] In the present invention, the definitions of toluene conversion and xylene selectivity are as follows:

[0055]

[0056]

[0057] Example 1

[0058] 1. Preparation of aromatic methylation catalyst

[0059] (1) Vector preparation

[0060] 70 g of ammonium ZSM-5 powder (silicon-aluminum molecular ratio SiO2 / Al2O3 is 180, and the BET mesoporous specific surface area measured by low-temperature nitrogen adsorption method is 80 m 2 / g, mesoporous pore volume 0.15ml / g), and 75g of silica sol containing 40wt% SiO2 were uniformly mixed, fully kneaded and evenly mixed, extruded, dried at 120℃ for 3 hours, calcined at 550℃ in air atmosphere for 4 hours, and sheared to obtain a cylindrical carrier with a diameter of 2.0mm and a length of 2.0mm.

[0061] (2) Catalyst preparation

[0062] Take 1 liter of the carrier prepared according to the method of step (1), mix it with 400 ml of a mixed aqueous solution of ferric nitrate and nickel nitrate (containing 12 g of iron oxide and 12 g of nickel oxide), impregnate it for 4 hours, dry it at 120°C for 3 hours, and calcine it at 550°C in an air atmosphere for 4 hours to obtain an aromatic methylation catalyst M1, in which the mass content of the active components iron oxide and nickel oxide is 24%.

[0063] 2. Preparation of liquid phase methyl transfer catalyst

[0064] (1) 75 g of ammonium BETA / MOR symbiotic molecular sieve powder, 25 g of alumina binder and 5 g of extrusion molding aid sesbania powder were mixed and mixed thoroughly, then extruded, dried at 120° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain catalyst precursor A. The BETA / MOR symbiotic molecular sieve was characterized by XPS-argon ion etching technology to obtain the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio S is 0.55.

[0065] Among them, the BETA / MOR molecular sieve synthesis method: take MOR molecular sieve with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 20 as a seed, take water glass (containing 28wt% SiO2, modulus 3.0-3.5) as a silicon source, and take sodium aluminate as an aluminum source; take tetraethylammonium hydroxide (TEAOH) as the first template, take sodium fluoride as the second template, and take NaOH as an alkali source. The molecular sieve synthetic glue composition is: n(Na2O) / n(SiO2) / n(Al2O3) / n(TEAOH / ) / n(H2O) / n(NaF)=1.5:40:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, and stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor was first hydrothermally crystallized at 120°C for 48 hours, and then hydrothermally crystallized at 180°C for 48 hours to obtain a symbiotic molecular sieve, namely, a BETA / MOR symbiotic molecular sieve. The BETA / MOR phase mass ratio was 35 / 65, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio is 0.55, and the molar ratio of SiO2 / Al2O3 is 29.

[0066] The XRD pattern of the intergrowth molecular sieve in this example is shown in Figure 1 ,Depend on Figure 1 It can be seen that it has typical characteristic peaks of BETA and MOR molecular sieves. The SEM image of this example of symbiotic molecular sieve is shown in Figure 2 ,Depend on Figure 2 It can be seen that there is a clear morphology in which large MOR particles and small BETA molecular sieve particles coexist.

[0067] The specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this case is 410m 2 / g, pore volume is 0.25cm 3 / g.

[0068] (2) The catalyst precursor A was treated with ammonia-containing water vapor (specifically, an aqueous solution containing 20 wt% ammonia was contacted with A at a temperature of 350° C. for 10 h, and a mass space velocity of 1 h -1 ), to obtain a solid acid transalkylation catalyst T1. The acid distribution value A of the catalyst T1 after being treated with NH3 steam is 1.5.

[0069] 3. Catalyst evaluation

[0070] (1) Methylation reaction conditions: reaction temperature 440°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 2.0, toluene feed mass space velocity 4 h -1The molar ratio of hydrogen to toluene is 2. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 180°C white clay adsorption treatment and then enters a liquid phase methyl transfer reaction unit.

[0071] (2) Liquid phase methyl transfer reaction conditions: reaction temperature 290°C, reaction pressure 4 MPa, aromatic feed mass space velocity 1 h -1 , the molar ratio of hydrogen to aromatics is 1, the reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0072] The toluene conversion rate of the above reaction for 72 hours was 47.5%, and the xylene selectivity was 93.6%.

[0073] Example 2

[0074] 1. Preparation of aromatic methylation catalyst

[0075] (1) Vector preparation

[0076] 70 g of ammonium ZSM-5 powder (silicon-aluminum molecular ratio SiO2 / Al2O3 is 260, and the BET mesoporous specific surface area measured by low-temperature nitrogen adsorption method is 70 m 2 / g, mesoporous pore volume 0.12ml / g), and 30g of alumina-containing material were uniformly mixed, fully kneaded, extruded, dried at 100°C for 10 hours, calcined at 450°C in air atmosphere for 10 hours, and sheared to obtain a cylindrical carrier with a diameter of 2.0mm and a length of 2.0mm.

[0077] (2) Catalyst preparation

[0078] Take 1 liter of the carrier prepared according to the method of step (1), mix it with 400 ml of a mixed aqueous solution of ferric nitrate and nickel nitrate (containing 10 g of iron oxide and 18 g of nickel oxide), impregnate it for 4 hours, dry it at 120°C for 5 hours, and calcine it at 550°C in an air atmosphere for 4 hours to obtain an aromatic methylation catalyst M2, in which the mass content of the active components iron oxide and nickel oxide is 28%.

[0079] 2. Preparation of liquid phase methyl transfer catalyst

[0080] (1) 75 g of ammonium BETA / MOR symbiotic molecular sieve powder, 25 g of alumina binder and 5 g of extrusion molding aid sesbania powder were mixed and mixed thoroughly, then extruded, dried at 120° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain catalyst precursor A. The BETA / MOR symbiotic molecular sieve was characterized by XPS-argon ion etching technology to obtain the surface aluminum S SAR With the aluminum inside the molecular sieve SARThe atomic ratio S is 0.60.

[0081] BETA / MOR molecular sieve synthesis method: take MOR molecular sieve with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 25 as a seed, take water glass (containing 28wt% SiO2, modulus 3.0-3.5) as a silicon source, take aluminum sulfate as an aluminum source; take tetraethylammonium bromide (TEABr) as the first template, take sodium fluoride as the second template, and take NaOH as an alkali source. The molecular sieve synthesis glue composition is: n(Na2O) / n(SiO2) / n(Al2O3) / n(TEABr / ) / n(H2O) / n(NaF)=2.0:55:1:12:980:6, adjust the pH to 11 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 35%. The above precursor was first hydrothermally crystallized at 130°C for 24 hours and then hydrothermally crystallized at 170°C for 48 hours to obtain a BETA / MOR symbiotic molecular sieve. The BETA / MOR phase mass ratio was 56 / 44, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO2 / Al2O3 is 0.60, and the molar ratio of SiO2 / Al2O3 is 31. The XRD pattern of the intergrowth molecular sieve in this example is similar to Figure 1 Similarly, the SEM images of the co-existing molecular sieves in this example are similar to Figure 2 Similarly, the specific surface area of ​​BETA / MOR symbiotic molecular sieve is 466m 2 / g, pore volume is 0.27cm 3 / g.

[0082] (2) The catalyst precursor A was treated with ammonia-containing water vapor (specifically, an aqueous solution containing 10 wt% ammonia was contacted with A at a temperature of 500° C. for 5 h and a mass space velocity of 2 h -1 ), to obtain a solid acid transalkylation catalyst T2. The acid distribution value A of the T2 catalyst after being treated with NH3 steam is 1.2.

[0083] 3. Catalyst evaluation

[0084] (1) Methylation reaction conditions: reaction temperature 460°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 1.0, toluene feed mass space velocity 2 h -1 The molar ratio of hydrogen to toluene is 6. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 200°C acidic ZSM-11 molecular sieve for adsorption treatment, and then enters a liquid phase methyl transfer reaction unit.

[0085] (2) Liquid phase methyl transfer reaction conditions: reaction temperature 250°C, reaction pressure 6 MPa, aromatic feed mass space velocity 4 h -1 The molar ratio of hydrogen to aromatics is 2. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0086] The toluene conversion rate of the above reaction for 72 hours was 50.4%, and the xylene selectivity was 95.7%.

[0087] Example 3

[0088] 1. Preparation of aromatic methylation catalyst

[0089] (1) Vector preparation

[0090] 70 g of ammonium ZSM-5 powder (silicon-aluminum molecular ratio SiO2 / Al2O3 is 200, and the BET mesoporous specific surface area measured by low-temperature nitrogen adsorption method is 76 m 2 / g, mesoporous pore volume 0.14ml / g), and 30g of pseudo-boehmite were uniformly mixed, fully kneaded, extruded, dried at 120°C for 5 hours, calcined at 550°C in air atmosphere for 3 hours, and sheared to obtain a cylindrical carrier with a diameter of 2.0mm and a length of 2.0mm.

[0091] (2) Catalyst preparation

[0092] Take 1 liter of the carrier prepared according to the method of step (1), mix it with 400 ml of a mixed nickel nitrate aqueous solution (containing 20 g of nickel oxide), impregnate it for 4 hours, dry it at 120°C for 5 hours, and calcine it at 550°C in an air atmosphere for 4 hours to obtain an aromatic methylation catalyst M3, in which the mass content of the active components iron oxide and nickel oxide is 20%.

[0093] 2. Preparation of liquid phase methyl transfer catalyst

[0094] (1) 75 g of ammonium BETA / MOR symbiotic molecular sieve powder, 25 g of alumina binder and 5 g of extrusion molding aid sesbania powder were mixed and mixed thoroughly, then extruded, dried at 120° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain catalyst precursor A. The BETA / MOR symbiotic molecular sieve was characterized by XPS-argon ion etching technology to obtain the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio S is 0.78.

[0095] BETA / MOR molecular sieve synthesis method: take MOR molecular sieve with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 20 as a seed, take water glass (containing 28wt% SiO2, modulus 3.0-3.5) as a silicon source, take sodium aluminate as an aluminum source; take tetraethylammonium hydroxide (TEAOH) as the first template, take sodium fluoride as the second template, and take NaOH as an alkali source. The molecular sieve synthesis glue composition is: n(Na2O) / n(SiO2) / n(Al2O3) / n(TEAOH / ) / n(H2O) / n(NaF)=2.5:55:1:12:800:4.5, adjust the pH to 13 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 40%. The above precursor was first hydrothermally crystallized at 100°C for 48 hours and then hydrothermally crystallized at 160°C for 72 hours to obtain a BETA / MOR intergrowth molecular sieve. The BETA / MOR phase mass ratio was 72 / 28, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO2 / Al2O3 is 0.78, and the molar ratio of SiO2 / Al2O3 is 25. The XRD pattern of the intergrowth molecular sieve in this example is similar to Figure 1 Similarly, the SEM images of the co-existing molecular sieves in this example are similar to Figure 2 Similar. The specific surface area of ​​BETA / MOR symbiotic molecular sieve is 538m 2 / g, pore volume is 0.29cm 3 / g.

[0096] (2) The catalyst precursor A was treated with ammonia-containing water vapor (specifically, an aqueous solution containing 20 wt% ammonia was contacted with A at a temperature of 400° C. for 3 h and a mass space velocity of 1 h -1 ), to obtain a solid acid transalkylation catalyst T3. The acid distribution value A of the T3 catalyst after being treated with NH3 steam is 1.8.

[0097] 3. Catalyst evaluation

[0098] (1) Methylation reaction conditions: reaction temperature 460°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 2.0, toluene feed mass space velocity 4 h -1 The molar ratio of hydrogen to toluene is 3. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 200°C amorphous silica-alumina adsorption treatment and then enters a liquid phase methyl transfer reaction unit.

[0099] (2) Liquid phase methyl transfer reaction conditions: reaction temperature 280°C, reaction pressure 3 MPa, aromatic feed mass space velocity 2 h -1, the molar ratio of hydrogen to aromatics is 1, the reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0100] The toluene conversion rate of the above reaction for 72 hours was 47.6%, and the xylene selectivity was 92.8%.

[0101] Comparative Example 1

[0102] Compared with Example 1, the only difference is that there is no liquid phase methyl transfer reaction device.

[0103] The toluene conversion rate after the above reaction for 72 hours was 36.9%, and the xylene selectivity was 75.8%.

[0104] Comparative Example 2

[0105] 1. Preparation of aromatic methylation catalyst

[0106] The aromatic methylation catalyst was the same as in Example 1 (M1).

[0107] 2. Preparation of liquid phase methyl transfer catalyst

[0108] (1) 75 g of ammonium BETA / MOR symbiotic molecular sieve powder, 25 g of alumina binder and 5 g of extrusion molding aid sesbania powder were mixed and mixed thoroughly, then extruded, dried at 120° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain catalyst DT1. The acid distribution value of the liquid phase methyl transfer catalyst that was not treated with NH3 steam was A 0.8.

[0109] The BETA / MOR molecular sieve synthesis method is the same as that in Example 1.

[0110] 3. Catalyst evaluation

[0111] (1) Methylation reaction conditions: reaction temperature 440°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 2.0, toluene feed mass space velocity 4 h -1 The molar ratio of hydrogen to toluene is 2. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 180°C white clay adsorption treatment and then enters a liquid phase methyl transfer reaction unit.

[0112] (2) Liquid phase methyl transfer reaction conditions: reaction temperature 290°C, reaction pressure 4 MPa, aromatic feed mass space velocity 1 h -1 The molar ratio of hydrogen to aromatic material is 1. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0113] The toluene conversion rate after the above reaction for 72 hours was 41.9%, and the xylene selectivity was 84.5%.

[0114] Comparative Example 3

[0115] 1. Preparation of aromatic methylation catalyst

[0116] The aromatic methylation catalyst was the same as in Example 1 (M1).

[0117] 2. Preparation of liquid phase methyl transfer catalyst

[0118] (1) 75 g of ammonium BETA / MOR symbiotic molecular sieve powder, 25 g of alumina binder and 5 g of extrusion molding aid sesbania powder were mixed and mixed thoroughly, then extruded, dried at 120° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor A. The aluminum distribution value S of the BETA / MOR symbiotic molecular sieve characterized by XPS-argon ion etching technology was 0.90.

[0119] BETA / MOR molecular sieve synthesis method: take MOR molecular sieve with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 20 as a seed, take water glass (containing 28wt% SiO2, modulus 3.0-3.5) as a silicon source, take sodium aluminate as an aluminum source; take tetraethylammonium hydroxide (TEAOH) as the first template, take sodium fluoride as the second template, and take NaOH as an alkali source. The composition of the molecular sieve synthesis glue is: n(Na2O) / n(SiO2) / n(Al2O3) / n(TEAOH / ) / n(H2O) / n(NaF)=1.5:40:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor is hydrothermally crystallized at 180°C for 48 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the mass ratio of BETA / MOR phase is 18 / 82, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of BETA / MOR is 0.90, and the molar ratio of SiO2 / Al2O3 is 22. The specific surface area of ​​BETA / MOR symbiotic molecular sieve is 384m 2 / g, pore volume is 0.14cm 3 / g.

[0120] (2) The catalyst precursor A was treated with ammonia-containing water vapor (specifically, an aqueous solution containing 20 wt% ammonia was contacted with A, wherein the temperature was 350° C., the time was 10 h, and the mass space velocity of the ammonia-containing solution was 1 h -1), to obtain a solid acid transalkylation catalyst DT2. The acid distribution value A of the DT2 catalyst after being treated with NH3 steam is 3.3.

[0121] 3. Catalyst evaluation

[0122] (1) Methylation reaction conditions: reaction temperature 440°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 2.0, toluene feed mass space velocity 4 h -1 The molar ratio of hydrogen to toluene is 2. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 180°C white clay adsorption treatment and then enters a liquid phase methyl transfer reaction unit.

[0123] (2) Liquid phase methyl transfer reaction conditions: reaction temperature 290°C, reaction pressure 4 MPa, aromatic feed mass space velocity 1 h -1 The molar ratio of hydrogen to aromatic material is 1. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0124] The toluene conversion rate of the above reaction after 72 hours was 40.6%, and the xylene selectivity was 79.8%.

[0125] Comparative Example 4

[0126] 1. Preparation of aromatic methylation catalyst

[0127] The aromatic methylation catalyst was the same as in Example 1 (M1).

[0128] 2. Preparation of gas phase methyl transfer catalyst

[0129] The liquid-phase transmethylation catalyst of Example 1 (T1) was impregnated with 0.1% Ni to obtain a gas-phase transalkylation catalyst (DT4).

[0130] 3. Catalyst evaluation

[0131] (1) Methylation reaction conditions: reaction temperature 440°C, reaction pressure 0.5 MPa, toluene to methanol feed molar ratio 2.0, toluene feed mass space velocity 4 h -1 The molar ratio of hydrogen to toluene is 2. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then the water generated by the reaction is separated to obtain a liquid aromatic product. The above liquid aromatic product enters a 180°C white clay adsorption treatment and then enters a liquid phase methyl transfer reaction unit.

[0132] (2) Gas-phase methyl transfer reaction conditions: reaction temperature 370°C, reaction pressure 3 MPa, aromatic feed mass space velocity 3 h- 1The molar ratio of hydrogen to aromatics is 3. The reaction product is cooled by an air condenser, separated by a gas-liquid separator, and then separated to obtain a liquid aromatic product.

[0133] The toluene conversion rate of the above reaction for 72 hours was 46.2%, and the xylene selectivity was 88.1%.

[0134] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for increasing the production of xylene by methylating toluene and methanol, comprising the following steps: (1) mixing toluene and methanol into a first reaction zone, contacting with an aromatic methylation catalyst under hydrogen conditions, and causing a gas phase methylation reaction to obtain a first stream; (2) introducing the first logistics of step (1) into a second reaction zone, contacting it with a methyl transfer catalyst under hydrogen conditions, obtaining a second logistics through a liquid phase methyl transfer reaction, and separating to obtain a xylene product.

2. The method according to claim 1, characterized in that The molar ratio of toluene to methanol in step (1) is 1:1 to 2:

1.

3. The method according to claim 1, characterized in that The aromatic methylation catalyst in step (1) comprises a carrier and an active component, wherein the carrier comprises a molecular sieve and a binder; optionally, the molecular sieve is selected from at least one of an MFI molecular sieve, a BETA molecular sieve, and a MOR molecular sieve, preferably an MFI molecular sieve; optionally, the active component of the aromatic methylation catalyst in step (1) is selected from at least one of VIII transition metal elements, preferably at least one of iron, cobalt, and nickel.

4. The method according to claim 1, characterized in that: The hydrogenation conditions of step (1) are as follows: the molar ratio of toluene to hydrogen is 0.5 to 2:1; Optionally, the gas phase methylation reaction conditions of step (1) include: temperature of 400 to 550°C, pressure of 0.5 to 1 MPa, and toluene feed mass space velocity of 2 to 10 h -1 .

5. The method according to claim 1, characterized in that The first stream obtained in step (1) is treated with an adsorbent and then introduced into the second reaction zone.

6. The method according to claim 1, characterized in that The methyl transfer catalyst in step (2) includes BETA / MOR symbiotic molecular sieve and a binder.

7. The method according to claim 6, characterized in that Step (2) the BETA / MOR symbiotic molecular sieve, the surface aluminum S in the symbiotic molecular sieve SAR With the aluminum inside the molecular sieve SAR The atomic ratio is 0.1 to 0.

8.

8. The method according to claim 6, characterized in that The BETA / MOR intergrowth molecular sieve in step (2) has the following schematic chemical composition, in terms of molar ratio: nSiO2 / Al2O3, wherein 10≤n≤100, preferably 20≤n≤50.

9. The method according to claim 6, characterized in that The method for preparing the BETA / MOR symbiotic molecular sieve described in step (2) comprises: (a) mixing a silicon source, an aluminum source, a first template T1, a second template T2, an alkali source and water, adjusting the pH to 9-13, and then adding MOR seed crystals to obtain a molecular sieve precursor; (b) The molecular sieve precursor described in (a) is first subjected to a first-stage hydrothermal crystallization, and then the temperature is increased to perform a second-stage hydrothermal crystallization to obtain the BETA / MOR symbiotic molecular sieve.

10. The method according to claim 1, 6 or 9, characterized in that: The preparation method of the transmethylation catalyst described in step (2) comprises the following steps: (i) mixing BETA / MOR symbiotic molecular sieve powder and a binder, mixing them uniformly, and then molding, drying and calcining to obtain a catalyst precursor; (ii) treating the catalyst precursor with water vapor containing ammonia to obtain a methyl transfer catalyst.

11. The method according to claim 10, characterized in that The step (ii) of treating the catalyst precursor with ammonia-containing water vapor comprises: contacting the catalyst precursor with an ammonia-containing aqueous solution under conditions that satisfy the gasification of ammonia and water.

12. The method according to claim 1 or 10, characterized in that: The acid distribution value obtained by NH3-TPD characterization of the methyl transfer catalyst in step (2) is A, where A is W acid With S acid and A is 1 to 2.

13. The method according to claim 1, characterized in that In step (2), the liquid phase methyl transfer reaction conditions include: temperature of 200-300°C, pressure of 4-6 MPa, and mass space velocity of aromatic feed of 1-4 h -1 , the molar ratio of aromatics to hydrogen is 0.5 to 2:1.

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