An EUO molecular sieve, a solid-phase synthesis method, a preparation method of a xylene isomerization catalyst and a xylene isomerization reaction

Abstract

The present application relates to a kind of EUO molecular sieve and solid phase synthesis method, xylene isomerization catalyst preparation method and xylene isomerization reaction, the solid phase synthesis method of EUO molecular sieve includes: solid-state silicon source, aluminum source, alkali source and EUO molecular sieve structure guiding agent are mixed and ground, then solid phase hot synthesis is carried out.The solid phase synthesis method of EUO molecular sieve of the present application has the advantages of environment-friendly, little waste discharge, and by reasonably controlling the ratio of silicon and aluminum source, adjusting the basicity of molecular sieve, effectively and environment-friendlyly modify the acidity of molecular sieve, and then the xylene isomerization catalyst with excellent catalytic performance is prepared, can well play isomerization catalytic effect to the xylene isomerization raw material containing ethylbenzene.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to an EUO molecular sieve and a solid-phase synthesis method, a method for preparing a xylene isomerization catalyst, and a xylene isomerization reaction. Background Technology

[0002] p-Xylene (PX) is an important chemical raw material, mainly used in the production of terephthalic acid and diterephthalate, and also applied in coatings, dyes, pesticides, and pharmaceuticals. With the development of these industries, the demand for PX is growing rapidly. Currently, the main process technology for increasing PX production is xylene isomerization, a crucial method for converting low-value m-xylene and o-xylene into p-xylene (PX).

[0003] Through the xylene isomerization reaction, the p-xylene in the product reaches or approaches thermodynamic equilibrium. The product can be separated into PX product by a separation device, and then small amounts of light non-aromatic hydrocarbons, benzene, toluene and C9 are also separated. + After the heavy aromatics are separated, the remaining C8 aromatics can be recycled as raw materials for isomerization.

[0004] Under current technological conditions, separating ethylbenzene from xylene is extremely difficult and uneconomical, regardless of whether efficient distillation or adsorption separation methods are used. Therefore, ethylbenzene must be converted simultaneously during the xylene isomerization process. There are two different directions for ethylbenzene conversion: ethylbenzene to xylene and ethylbenzene deethylation to benzene. The economics of these two directions depend on the composition of the feedstock, the energy consumption of the equipment, and market conditions.

[0005] When the mass fraction of ethylbenzene in the feedstock is low, the ethylbenzene deethylation route is often used. This route allows the reaction to proceed under conditions of higher space velocity and lower hydrogen-to-hydrogen ratio and pressure, saving energy. However, when the mass fraction of ethylbenzene in the feedstock is high, the deethylation route produces a large amount of benzene as a byproduct. When the price of benzene is low, the economic viability deteriorates significantly. Therefore, for high-ethylbenzene feedstocks, the route of ethylbenzene to xylene is often used. The reaction pathway for ethylbenzene to xylene is more complex, the single-pass processing capacity of the catalyst is lower, and the required hydrogen-to-hydrogen ratio, temperature, and pressure conditions are more stringent. Furthermore, the types of molecular sieves and acidity characteristics of the catalysts in the two routes also differ significantly.

[0006] CN200910260072.9 discloses an ethylbenzene conversion isomerization catalyst, the active component of which is an EUO-type molecular sieve. EUO-type molecular sieves are generally considered in the art to be novel materials that have emerged in recent years, and are particularly suitable for the catalytic process of isomerization of ethylbenzene to xylene. Their unique pore structure features one-dimensional ten-membered ring straight channels and staggered twelve-membered ring side bags. The side bag structure is beneficial for maintaining a longer residence time of ethylbenzene within the molecular sieve, thus completing the catalytic conversion to xylene.

[0007] As described in the aforementioned patent, the synthesis process of EUO molecular sieves is relatively complex. The main component of the structure-directing agent used is hexamethyldiamine bromide, which is expensive and used in large quantities. However, in traditional hydrothermal synthesis processes, the utilization rate of the structure-directing agent is not high. After the synthesis process is completed, a considerable portion of the structure-directing agent dissolves in the mother liquor, resulting in the mother liquor containing organic ammonia nitrogen and bromides, which are difficult to post-process, having to be treated as waste liquid, which is very detrimental to environmental protection.

[0008] Molecular sieve raw powder is usually in the Na form, which needs to be converted to the ammonium form through ion exchange using ammonium salts, followed by calcination to decompose the ammonium cations into the H form, i.e., protonic acid (or... (Acid). Patent CN200880120492.0 describes a method for preparing a xylene isomerization catalyst via ion exchange, preferably using ZSM-5 molecular sieve, in which a molded support is subjected to ion exchange in solution. The exchange solution typically contains at least one cation source that forms hydrogen, such as NH4+. + The hydrogen-forming cations primarily replace alkali metal cations to provide hydrogen as a component of the molecular sieve after calcination. Suitable compounds used as solutes in aqueous solutions include ammonium nitrate, ammonium sulfate, and / or ammonium chloride.

[0009] As mentioned above, the preparation technology of xylene isomerization catalysts typically requires the conversion of Na-type molecular sieves into H-type molecular sieves via ion exchange. However, the large amount of inorganic ammonium salts used in the ion exchange process dissolves in the mother liquor, posing a challenge for recovery. The required acid strength and quantity for xylene isomerization catalysis are relatively low compared to conventional hydrocarbon framework isomerization reactions. Therefore, a key technical problem to be solved is how to rationally control the silicon-aluminum source ratio and adjust the system alkalinity during molecular sieve synthesis to effectively optimize the acidity of the molecular sieve product, enabling it to meet the requirements for catalyzing xylene isomerization without the need for exchange.

[0010] In summary, the key technical problem to be solved is how to use an optimized synthesis method to synthesize EUO-structured hierarchical porous molecular sieve active components in a one-step green manner, and to modify the acidity of the catalyst using an environmentally friendly method so that the prepared catalyst can be used for xylene isomerization reaction containing ethylbenzene. Compared with existing catalysts, this method should significantly reduce the emissions of waste gas, wastewater, and solid waste during the catalyst production process while maintaining comparable performance. Summary of the Invention

[0011] The purpose of this invention is to provide an EUO molecular sieve and a solid-phase synthesis method, a method for preparing a xylene isomerization catalyst, and a xylene isomerization reaction, so as to prepare high-performance EUO molecular sieves and xylene isomerization catalysts while significantly reducing the emission of waste gas, wastewater, and solid waste during the production process.

[0012] On one hand, the present invention relates to a solid-phase synthesis method of EUO molecular sieve, comprising: mixing and grinding a solid silicon source, an aluminum source, an alkali source and an EUO molecular sieve structure directing agent, and then performing solid-phase thermal synthesis.

[0013] Optionally, the EUO molecular sieve structure directing agent is selected from compounds that satisfy the following formula (1):

[0014] N(R1)3(CH2) n N(R2)3·2X Formula (1); R1 and R2 are each independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms, X is selected from halogens, and n is 2 to 10; preferably, R1 and R2 are each independently selected from methyl or ethyl, X is selected from chlorine or bromine, and n is 4 to 8.

[0015] Optionally, the silicon source is selected from silica gel powder or fumed silica, the aluminum source is selected from boehmite or sodium aluminate, and the alkali source is selected from NaOH or KOH; preferably, the silicon source is silica gel powder and the alkali source is NaOH; more preferably, the silicon source is silica gel powder with a particle size of 2.5 to 50 nm.

[0016] Optionally, the molar ratio of the EUO molecular sieve structure directing agent to the silicon source (based on SiO2) is (0.02-0.22):1; when the aluminum source is boehmite, the molar ratio of the silicon source, the aluminum source, and the alkali source (based on SiO2, Al2O3, and Na2O) is 1:(0.003-0.02):(0.009-0.1); when the aluminum source is sodium aluminate, the molar ratio of the silicon source (based on SiO2), the aluminum source (based on Al2O3), and the total sodium in the alkali source and the aluminum source (based on Na2O) is 1:(0.003-0.02):(0.009-0.1).

[0017] Optionally, the solid-phase thermal synthesis includes a first thermal synthesis stage and a second thermal synthesis stage. The temperature of the first thermal synthesis stage is 90–140°C, and the time is 3–18 hours. The temperature of the second thermal synthesis stage is 140–180°C, and the time is 12–72 hours. Preferably, the temperature of the first thermal synthesis stage is 110–130°C, and the time is 6–12 hours. The temperature of the second thermal synthesis stage is 150–170°C, and the time is 24–36 hours.

[0018] On the other hand, the present invention relates to an EUO molecular sieve, which is prepared by the solid-phase synthesis method described above; preferably, the EUO molecular sieve is a micron-sized EUO molecular sieve with a grain size of 0.5 to 3 microns; more preferably, the grain size of the EUO molecular sieve is 0.8 to 1.8 microns.

[0019] Optionally, the molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (20-350):1; preferably, the molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (25-70):1.

[0020] In another aspect, the present invention relates to a method for preparing a xylene isomerization catalyst, comprising the following steps: (1) mixing EUO molecular sieve with a binder and a binder, molding, drying and calcining to obtain a composite support; the EUO molecular sieve is the EUO molecular sieve, or is prepared by the solid-phase synthesis method; (2) placing the composite support in a platinum solution for impregnation, and then drying, activating and reducing to obtain the xylene isomerization catalyst.

[0021] Optionally, the binder is selected from alumina or titanium dioxide, and the adhesion promoter is selected from nitric acid or hydrochloric acid; preferably, the binder is alumina and the adhesion promoter is nitric acid.

[0022] Optionally, in the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-90%, with the remainder being alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.01-0.5%, based on the mass of the composite support; preferably, in the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-40%, with the remainder being alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.15-0.25%, based on the mass of the composite support.

[0023] Optionally, in step (2), the activation is carried out in an air atmosphere, and the reduction is carried out in a hydrogen atmosphere.

[0024] In another aspect, the present invention relates to a xylene isomerization reaction, wherein xylene isomerization raw materials containing ethylbenzene are subjected to a xylene isomerization reaction in the presence of a xylene isomerization catalyst obtained by the preparation method described above.

[0025] Optionally, the mass percentage of ethylbenzene in the xylene isomerization feedstock is 1-20%, based on the mass of the xylene isomerization feedstock; the xylene isomerization reaction temperature is 375-395℃, the pressure is 0.8-1.5 MPa, the hydrogen-to-hydrocarbon molar ratio is 2.5-3.5, and the weight hourly space velocity of the xylene isomerization catalyst is 3-6 h⁻¹. -1 .

[0026] Beneficial effects:

[0027] The solid-phase synthesis method of EUO molecular sieve of this invention has the advantages of being environmentally friendly and producing less waste. By rationally controlling the ratio of silicon and aluminum sources and adjusting the basicity of the molecular sieve, the acidity of the molecular sieve can be effectively and environmentally modified, thereby obtaining a xylene isomerization catalyst with excellent catalytic performance. It can effectively perform isomerization catalysis on xylene isomerization feedstock containing ethylbenzene. Attached Figure Description

[0028] Figure 1 This is the XRD diffraction pattern of the EUO molecular sieve prepared in Example 1 of this invention;

[0029] Figure 2 This is a scanning electron microscope image of the EUO molecular sieve prepared in Example 1 of the present invention. Detailed Implementation

[0030] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0031] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0032] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0033] In a first aspect, the present invention relates to a solid-phase synthesis method for EUO molecular sieves, comprising: mixing and grinding a solid silicon source, an aluminum source, an alkali source and an EUO molecular sieve structure directing agent, and then performing solid-phase thermal synthesis.

[0034] It should be noted that the solid-phase synthesis method of the EUO molecular sieve of the present invention is a mother liquor-free synthesis method, which is a one-step green synthesis of EUO structure hierarchical porous molecular sieve. The molecular sieve is a micron-sized EUO molecular sieve synthesized by mechanical grinding and programmed temperature control under specific silicon and aluminum sources under mother liquor-free conditions.

[0035] It should be noted that in the solid-phase synthesis method of EUO molecular sieve of the present invention, the mixing can be carried out by mechanical mixing, the grinding time can be 5 to 60 minutes, and the ground powder can be transferred to the synthesis kettle for closed reaction.

[0036] According to one embodiment of the first aspect of the present invention, the EUO molecular sieve structure directing agent is selected from compounds satisfying the following formula (1):

[0037] N(R1)3(CH2)n N(R2)3·2X Equation (1);

[0038] R1 and R2 are each independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms, X is selected from halogens, and n is 2 to 10; preferably, R1 and R2 are each independently selected from methyl or ethyl, X is selected from chlorine or bromine, and n is 4 to 8.

[0039] It should be noted that in the above formula (1), C represents carbon, H represents hydrogen, N represents nitrogen, and -(CH2) n - is a straight-chain alkylene group. In a preferred embodiment, R1 and R2 can be the same straight-chain alkyl group, such as each N being connected to two methyl groups or each N being connected to two ethyl groups.

[0040] According to one embodiment of the first aspect of the present invention, the silicon source is selected from silica gel powder or fumed silica, the aluminum source is selected from boehmite or sodium aluminate, and the alkali source is selected from NaOH or KOH; preferably, the silicon source is silica gel powder and the alkali source is NaOH; more preferably, the silicon source is silica gel powder with a particle size of 2.5 to 50 nm.

[0041] It should be noted that in the solid-phase synthesis method of EUO molecular sieve of the present invention, specific silicon source, aluminum source, alkali and structure directing agent are selected, and EUO molecular sieve is obtained based on solid-phase thermal synthesis.

[0042] According to one embodiment of the first aspect of the present invention, the molar ratio of the EUO molecular sieve structure directing agent to the silicon source (based on SiO2) is (0.02-0.22):1; when the aluminum source is boehmite, the molar ratio of the silicon source, the aluminum source, and the alkali source (based on SiO2, Al2O3, and Na2O) is 1:(0.003-0.02):(0.009-0.1); when the aluminum source is sodium aluminate, the molar ratio of the silicon source (based on SiO2), the aluminum source (based on Al2O3), and the total sodium in the alkali source and the aluminum source (based on Na2O) is 1:(0.003-0.02):(0.009-0.1).

[0043] It should be noted that in the solid-phase synthesis method of EUO molecular sieve of the present invention, EUO molecular sieve can be well obtained by combining the specific silicon source, aluminum source, alkali and structure directing agent according to the specified ratio and then carrying out subsequent solid-phase thermal synthesis.

[0044] According to one embodiment of the first aspect of the present invention, the solid-phase thermal synthesis includes a first thermal synthesis stage and a second thermal synthesis stage, wherein the temperature of the first thermal synthesis stage is 90–140°C and the time is 3–18 hours, and the temperature of the second thermal synthesis stage is 140–180°C and the time is 12–72 hours; preferably, the temperature of the first thermal synthesis stage is 110–130°C and the time is 6–12 hours, and the temperature of the second thermal synthesis stage is 150–170°C and the time is 24–36 hours.

[0045] It should be noted that the solid-phase synthesis method of the present invention uses a similar temperature-programmed method for heating and crystallization to obtain micron-sized EUO molecular sieves.

[0046] Secondly, the present invention relates to an EUO molecular sieve, which is prepared by the above-described solid-phase synthesis method; preferably, the EUO molecular sieve is a micron-sized EUO molecular sieve with a grain size of 0.5 to 3 microns; more preferably, the grain size of the EUO molecular sieve is 0.8 to 1.8 microns.

[0047] like Figure 2 As shown, the EUO molecular sieves prepared by the solid-phase synthesis method of the present invention have uniform morphology and exhibit well-dispersed micron-sized spherical shapes.

[0048] According to one embodiment of the second aspect of the present invention, the molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (20-350):1; preferably, the molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (25-70):1.

[0049] It should be noted that the molecular sieve of the present invention effectively optimizes the acidity of the molecular sieve product by rationally controlling the ratio of silicon and aluminum sources and adjusting the alkalinity of the system. As a result, the catalyst obtained does not need to undergo ion exchange of inorganic ammonium salts to meet the requirements of catalytic xylene isomerization reaction, effectively reducing the emission of waste.

[0050] Thirdly, the present invention relates to a method for preparing a xylene isomerization catalyst, comprising the following steps: (1) mixing EUO molecular sieve with a binder and a binder, molding, drying and calcining to obtain a composite support; the EUO molecular sieve is the EUO molecular sieve described in the second aspect of the present invention, or is prepared by the solid-phase synthesis method described in the first aspect of the present invention; (2) placing the composite support in a platinum solution for impregnation, and then drying, activating and reducing to obtain the xylene isomerization catalyst.

[0051] It should be noted that in preparing the xylene isomerization catalyst of this invention, EUO molecular sieves need to be synthesized first according to the above-mentioned green method, followed by washing, drying, catalyst shaping, and calcination. The calcined shaped support can be directly loaded with noble metals and then activated and reduced. The catalyst prepared based on the preparation method of this invention can be used for the isomerization reaction of xylene containing ethylbenzene. Compared with existing catalysts, it can significantly reduce the emissions of waste gas, wastewater, and solid waste during the catalyst production process while maintaining comparable performance.

[0052] It should be noted that the molding in step (1) can be done by extrusion molding, and after extrusion molding, it can be granulated and then calcined. The platinum solution mentioned in step (2) can refer to a solution in which platinum exists in ionic form, such as chloroplatinic acid solution, sodium chloroplatinate solution, etc., and the impregnation can be done by conventional impregnation methods in the art.

[0053] According to one embodiment of a third aspect of the present invention, the adhesive is selected from alumina or titanium dioxide, and the adhesion promoter is selected from nitric acid or hydrochloric acid; preferably, the adhesive is alumina and the adhesion promoter is nitric acid.

[0054] It should be noted that in step (1), the drying can be carried out at 120°C for 8–24 hours, and the calcination can be carried out in air at 540°C for 2–24 hours. Calcination can be performed in a static atmosphere without air flow, or at a volume hourly space velocity (VHSV) of 50–500 h⁻¹. -1 The process is carried out in a dynamic air atmosphere. In step (2), the metal can be impregnated and activated and reduced using conventional methods to obtain the xylene isomerization catalyst of the present invention.

[0055] According to one embodiment of the third aspect of the present invention, in the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-90%, and the balance is alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.01-0.5%, based on the mass of the composite support; preferably, in the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-40%, and the balance is alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.15-0.25%, based on the mass of the composite support.

[0056] According to one embodiment of the third aspect of the present invention, in step (2), the activation is carried out in an air atmosphere, and the reduction is carried out in a hydrogen atmosphere. The reduction time in the hydrogen atmosphere can be 4 hours.

[0057] Fourthly, the present invention relates to a xylene isomerization reaction, wherein xylene isomerization raw materials containing ethylbenzene are subjected to a xylene isomerization reaction in the presence of a xylene isomerization catalyst prepared by the above preparation method.

[0058] According to one embodiment of the fourth aspect of the present invention, the mass percentage of ethylbenzene in the xylene isomerization feedstock is 1-20%, based on the mass of the xylene isomerization feedstock; the temperature of the xylene isomerization reaction is 375-395°C, the pressure is 0.8-1.5 MPa, the hydrogen-to-hydrocarbon molar ratio is 2.5-3.5, and the weight hourly space velocity of the xylene isomerization catalyst is 3-6 h⁻¹. -1 .

[0059] It should be noted that the xylene isomerization catalyst prepared in this invention is particularly suitable for catalyzing xylene isomerization feedstocks with a mass ratio of 1-20% ethylbenzene. Under its catalytic action, ethylbenzene can be converted into xylene, and the xylene is brought close to its thermodynamic equilibrium composition. The xylene isomerization reaction is carried out in the presence of hydrogen. Compared with existing catalysts, the xylene isomerization catalyst of this invention has comparable isomerization activity.

[0060] The present invention will be further described in detail below through examples. All reagents used in the following examples are commercially available finished reagents.

[0061] The following Examples 1-6 describe the preparation of EUO molecular sieves.

[0062] Example 1

[0063] Take 12g of solid silica powder with a particle size range of 2.5-50nm, 0.5514g of boehmite (alumina mass percentage of 75%), 1.6g of NaOH solid, and hexamethylhexanediamine bromide (N(CH3)3C6H) 12 1.448g of N(CH3)3·2Br) was placed in a mortar and mechanically mixed and ground thoroughly for 60 minutes.

[0064] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 120℃ for 8 hours; the second stage was carried out at 170℃ for 24 hours. After synthesis, the cooled molecular sieve powder was designated Z-1, with a silicon-to-aluminum ratio (molar ratio of SiO2 to Al2O3) of 50.

[0065] Example 2

[0066] Take 12g of solid silica powder with a particle size range of 2.5-50nm, 0.2757g of boehmite (alumina mass percentage of 75%), 0.8g of solid NaOH, and 10.528g of hexaethylbutanediamine chloride (N(C2H5)3C4H8N(C2H5)3·2Cl), place them in a mortar, mix mechanically and grind thoroughly for 10 minutes.

[0067] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 110℃ for 12 hours; the second stage was carried out at 160℃ for 36 hours. After synthesis, the cooled molecular sieve powder was designated Z-2, with a silicon-to-aluminum ratio of 100.

[0068] Example 3

[0069] Take 12g of solid silica powder with a particle size range of 2.5-50nm, 0.1103g of boehmite (alumina mass percentage of 75%), 0.192g of NaOH solid, and hexamethyloctanediamine bromide (N(CH3)3C8H) 16 6.24g of N(CH3)3·2Br) was placed in a mortar and mechanically mixed and ground thoroughly for 30 minutes.

[0070] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 130℃ for 6 hours; the second stage was carried out at 150℃ for 36 hours. After synthesis, the cooled molecular sieve powder was designated Z-3, with a silicon-to-aluminum ratio of 250.

[0071] Example 4

[0072] Take 12g of solid silica gel powder with a particle size range of 2.5–50nm, 0.4918g of sodium aluminate, 0.96g of solid NaOH, and hexaethylpentanediamine chloride (N(C2H5)3C5H) 10 2.744g of N(C2H5)3·2Cl) was placed in a mortar and mechanically mixed and ground thoroughly for 60 minutes.

[0073] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 115℃ for 12 hours; the second stage was carried out at 155℃ for 32 hours. After synthesis, the cooled molecular sieve powder was designated Z-4, with a silicon-to-aluminum ratio of 66.

[0074] Example 5

[0075] Take 12g of solid silica gel powder with a particle size range of 2.5–50nm, 0.1967g of sodium aluminate, 0.48g of solid NaOH, and hexaethylpentanediamine bromide (N(C2H5)3C5H)10 8.64g of N(C2H5)3·2Br) was placed in a mortar and mechanically mixed and ground thoroughly for 45 minutes.

[0076] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 125℃ for 9 hours; the second stage was carried out at 165℃ for 28 hours. After synthesis, the cooled molecular sieve powder was designated Z-5, with a silicon-to-aluminum ratio of 167.

[0077] Example 6

[0078] Take 12g of solid silica gel powder with a particle size range of 2.5-50nm, 0.0984g of sodium aluminate, 0.096g of solid NaOH, and hexamethylheptanediamine chloride (N(CH3)3C7H) 14 12.628g of N(CH3)3·2Cl was placed in a mortar and mechanically mixed and ground thoroughly for 15 minutes.

[0079] The ground powder was transferred to a sealed 200mL reactor. The first stage of synthesis was carried out at 120℃ for 7 hours; the second stage was carried out at 170℃ for 24 hours. After synthesis, the cooled molecular sieve powder was designated Z-6, with a silicon-to-aluminum ratio of 333.

[0080] The following examples illustrate the preparation of xylene isomerization catalysts.

[0081] Example 7

[0082] Take 4 g of molecular sieve Z-1 powder and mix it thoroughly with 16 g of alumina. Add 20 mL of 3% nitric acid aqueous solution to form a viscous mixture, which is then extruded into strips. The strips are dried at 120 °C for 12 hours and then granulated. They are then calcined in static air at 540 °C for 12 hours. Next, they are impregnated in 20 mL of chloroplatinic acid aqueous solution containing 0.04 g of platinum, and dried at 120 °C to prepare a catalyst containing 0.2% by mass of platinum. Finally, the catalyst is prepared at a volume hourly space velocity (VHSV) of 500 h⁻¹. -1 The catalyst was prepared in an oxidized state by activation in air atmosphere for 4 hours at an activation temperature of 500℃. -1 Catalyst C-1 was prepared by reducing the catalyst under hydrogen for 4 hours at a reduction temperature of 450℃.

[0083] Example 8

[0084] Take 5 grams of molecular sieve Z-2 powder and mix thoroughly with 15 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution and mix to form a viscous mixture, which is then extruded into strips. The strips are dried at 120°C for 8 hours and then granulated. Finally, they are calcined in a dynamic air atmosphere at 540°C for 6 hours, with an air volume hourly space velocity of 50 h⁻¹.-1 The catalyst was then impregnated in 20 mL of an aqueous solution containing 0.05 g of platinum in chloroplatinic acid, and dried at 120 °C to prepare a catalyst containing 0.25% by mass of platinum. It was then activated in air to prepare an oxidized catalyst, and reduced under hydrogen for 4 hours to prepare catalyst C-2. The space velocity, time, and temperature for activation in air were the same as in Example 7, and the temperature and space velocity for reduction in hydrogen were the same as in Example 7.

[0085] Example 9

[0086] Take 6 grams of molecular sieve Z-3 powder and mix thoroughly with 14 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution and mix to form a viscous mixture, which is then extruded into strips. The strips are dried at 120°C for 16 hours and then granulated. Finally, they are calcined in a dynamic air atmosphere at 540°C for 2 hours, with an air volume hourly space velocity (HSV) of 200 h⁻¹. -1 The catalyst was then impregnated in 20 mL of an aqueous solution containing 0.05 g of platinum in chloroplatinic acid, and dried at 120 °C to prepare a catalyst containing 0.25% by mass of platinum. It was then activated in air to prepare an oxidized catalyst, and reduced under hydrogen for 4 hours to prepare catalyst C-3. The space velocity, time, and temperature for activation in air were the same as in Example 7, and the temperature and space velocity for reduction in hydrogen were the same as in Example 7.

[0087] Example 10

[0088] Take 7 grams of molecular sieve Z-4 ​​powder and mix thoroughly with 13 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution and mix to form a viscous mixture, which is then extruded into strips. The strips are dried at 120°C for 21 hours and then granulated. Finally, they are calcined at 540°C in a dynamic air atmosphere for 8 hours, with an air volume hourly space velocity (HSV) of 400 h⁻¹. -1 The catalyst was then impregnated in 20 mL of an aqueous solution containing 0.05 g of platinum in chloroplatinic acid, dried at 120 °C, and prepared as a catalyst containing 0.25% by mass of platinum. It was then activated in air to prepare an oxidized catalyst, and reduced under hydrogen for 4 hours to prepare catalyst C-4. The space velocity, time, and temperature for activation in air were the same as in Example 7, and the temperature and space velocity for reduction in hydrogen were the same as in Example 7.

[0089] Example 11

[0090] Take 8 grams of molecular sieve Z-5 powder and mix thoroughly with 12 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution and mix to form a viscous mixture, which is then extruded into strips. The strips are dried at 120°C for 24 hours and then granulated. They are then calcined in a dynamic air atmosphere at 540°C for 18 hours, with an air volume hourly space velocity of 500 h⁻¹. -1The catalyst was then impregnated in 20 mL of an aqueous solution containing 0.03 g of platinum in chloroplatinic acid, and dried at 120 °C to prepare a catalyst containing 0.15% by mass of platinum. It was then activated in air to prepare an oxidized catalyst, and reduced under hydrogen for 4 hours to prepare catalyst C-5. The space velocity, time, and temperature for activation in air were the same as in Example 7, and the temperature and space velocity for reduction in hydrogen were the same as in Example 7.

[0091] Example 12

[0092] Take 6 grams of molecular sieve Z-6 powder and mix thoroughly with 14 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution and mix to form a viscous mixture, which is then extruded into strips. The strips are dried at 120°C for 18 hours and then granulated. Finally, they are calcined in a dynamic air atmosphere at 540°C for 24 hours, with an air volume hourly space velocity of 100 h⁻¹. -1 The catalyst was then impregnated in 20 mL of an aqueous solution containing 0.04 g of platinum in chloroplatinic acid, and dried at 120 °C to prepare a catalyst containing 0.2% by mass of platinum. It was then activated in air to prepare an oxidized catalyst, and reduced under hydrogen for 4 hours to prepare catalyst C-6. The space velocity, time, and temperature for activation in air were the same as in Example 7, and the temperature and space velocity for reduction in hydrogen were the same as in Example 7.

[0093] Comparative Example 1

[0094] Preparation of xylene isomerization catalyst:

[0095] Take 6 grams of commercially available EUO molecular sieve powder with a silicon-to-aluminum ratio of 50 and mix it thoroughly with 14 grams of alumina. Add 20 ml of 3% nitric acid aqueous solution to form a viscous mixture, and extrude it into strips. Dry the strips at 120°C for 12 hours, then granulate them and calcine them at 540°C for 12 hours. Perform ion exchange with 50 ml of 0.05 mol / L ammonium chloride aqueous solution at 90°C for 2 hours × 2 times, and wash until there are no chloride ions in the mother liquor. Then impregnate it with 20 ml of chloroplatinic acid aqueous solution containing 0.04 g of platinum, and dry it at 120°C to prepare a catalyst containing 0.2% by mass of platinum. Then activate it in air to prepare an oxidized catalyst, and reduce it in hydrogen for 4 hours to prepare catalyst D-1. The space velocity, time, and temperature for activation in air atmosphere are the same as in Example 7, and the temperature and space velocity for reduction in hydrogen atmosphere are the same as in Example 7.

[0096] Test Example 1

[0097] In a continuous flow fixed-bed micro hydrogen production unit, 2 grams of catalyst were loaded, and the catalysts prepared in Examples 7-12 and Comparative Example 1 were evaluated using industrial xylene isomerization feedstock. The composition of the feedstock used in the reaction is shown in Table 1, the evaluation process parameters and characteristics of the catalysts in each example, and the reaction results are shown in Table 2.

[0098] Catalyst performance is evaluated using the following calculation method:

[0099] Heterogeneity equilibrium achievement rate:

[0100] Ethylbenzene conversion rate:

[0101] Table 1 Raw Material Composition

[0102]

[0103] Table 2 Catalysts and Reaction Performance

[0104]

[0105]

[0106] Test Example 2

[0107] XRD and scanning electron microscopy were performed on the molecular sieve powder Z-1 prepared in Example 1. The XRD diffraction pattern of the molecular sieve powder Z-1 prepared in Example 1 is shown in the appendix. Figure 1 The molecular sieves prepared in Examples 2-6 exhibit characteristic peaks of EUO within the temperature range of 5–50 degrees. The XRD spectra obtained from these molecular sieves are compared with those obtained from other samples. Figure 1 They are basically the same, both exhibiting characteristic peaks of EUO molecular sieves.

[0108] SEM images of the molecular sieve powder Z-1 prepared in Example 1 are attached. Figure 2 The micron-sized EUO molecular sieve prepared in Example 1 has a crystal size of 0.8–1.8 micrometers, a uniform morphology, and exhibits well-dispersed micron-sized spherical crystals. The molecular sieves prepared in Examples 2–6 were examined using scanning electron microscopy (SEM). SEM images showed that their morphologies were essentially the same as those of the molecular sieve prepared in Example 1, exhibiting uniform morphology and well-dispersed micron-sized spherical crystals. Figure 2 The scanning electron microscope images show that the EUO molecular sieve prepared by the method of the present invention has different pore sizes between crystals, exhibiting a hierarchical pore distribution.

[0109] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0110] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0111] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A solid-phase synthesis method for EUO molecular sieves, wherein, include: Solid silicon source, aluminum source, alkali source and EUO molecular sieve structure directing agent are mixed and ground, and then solid-phase thermal synthesis is carried out. The EUO molecular sieve structure directing agent is selected from compounds that satisfy the following formula (1): N(R1)3(CH2) n N(R2)3·2X formula (1). R1 and R2 are each independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms, X is selected from halogens, and n is 2 to 10; The silicon source is selected from silica gel powder or silica fume, the aluminum source is selected from boehmite or sodium aluminate, and the alkali source is selected from NaOH or KOH. When the aluminum source is boehmite, the molar ratio of the silicon source, the aluminum source, and the alkali source, calculated as SiO2, Al2O3, and Na2O, is 1:(0.003~0.02):(0.009~0.1). When the aluminum source is sodium aluminate, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the total sodium in the alkali source and the aluminum source, calculated as Na2O, is 1:(0.003~0.02):(0.009~0.1). The solid-state thermal synthesis includes a first-stage thermal synthesis and a second-stage thermal synthesis. The temperature of the first-stage thermal synthesis is 90~140℃, and the time is 3~18 hours. The temperature of the second-stage thermal synthesis is 140~180℃, and the time is 12~72 hours. The EUO molecular sieve is a micron-sized EUO molecular sieve with a crystal size of 0.5~3 microns.

2. The solid-phase synthesis method according to claim 1, wherein, In the compound of formula (1), R1 and R2 are each independently selected from methyl or ethyl, X is selected from chlorine or bromine, and n is 4 to 8.

3. The solid-phase synthesis method according to claim 1, wherein, The silicon source is silica gel powder, and the alkali source is NaOH.

4. The solid-phase synthesis method according to claim 3, wherein, The molar ratio of the EUO molecular sieve structure directing agent to the silicon source (based on SiO2) is (0.02~0.22):

1.

5. The solid-phase synthesis method according to claim 1, wherein, The temperature of the first stage of thermal synthesis is 110~130℃ and the time is 6~12 hours. The temperature of the second stage of thermal synthesis is 150~170℃ and the time is 24~36 hours.

6. The solid-phase synthesis method according to claim 3, wherein, The silicon source is silica powder with a particle size of 2.5~50nm.

7. An EUO molecular sieve, wherein, The EUO molecular sieve is prepared by the solid-phase synthesis method described in any one of claims 1-6.

8. The EUO molecular sieve according to claim 7, wherein, The EUO molecular sieve is a micron-sized EUO molecular sieve with a crystal size of 0.5~3 microns.

9. The EUO molecular sieve according to claim 7, wherein, The EUO molecular sieve has a crystal size of 0.8~1.8 micrometers.

10. The EUO molecular sieve according to claim 7, wherein, The molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (20~350):

1.

11. The EUO molecular sieve according to claim 10, wherein, The molar ratio of SiO2 to Al2O3 in the EUO molecular sieve is (25~70):

1.

12. A method for preparing a xylene isomerization catalyst, wherein, Includes the following steps: (1) The EUO molecular sieve is mixed with a binder and a binder, shaped, dried and calcined to obtain a composite carrier; the EUO molecular sieve is the EUO molecular sieve described in any one of claims 7 to 11, or is prepared by the solid-phase synthesis method described in any one of claims 1 to 6; (2) The composite support is impregnated in a platinum solution, then dried, activated and reduced to obtain the xylene isomerization catalyst.

13. The preparation method according to claim 12, wherein, The adhesive is selected from alumina or titanium dioxide, and the adhesion promoter is selected from nitric acid or hydrochloric acid.

14. The preparation method according to claim 13, wherein, The adhesive is aluminum oxide, and the adhesion promoter is nitric acid.

15. The preparation method according to claim 13, wherein, In the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-90%, and the remainder is alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.01-0.5%, based on the mass of the composite support.

16. The preparation method according to claim 15, wherein, In the composite support obtained from step (1), the mass percentage of the EUO molecular sieve is 20-40%, and the remainder is alumina, based on the mass of the composite support; in the xylene isomerization catalyst obtained from step (2), the mass percentage of platinum is 0.15-0.25%, based on the mass of the composite support.

17. The preparation method according to claim 12, wherein, In step (2), the activation is carried out in an air atmosphere, and the reduction is carried out in a hydrogen atmosphere.

18. A method for xylene isomerization, wherein, In the presence of the xylene isomerization catalyst prepared by any one of claims 12-17, a xylene isomerization feedstock containing ethylbenzene is subjected to a xylene isomerization reaction.

19. The xylene isomerization method according to claim 18, wherein, The mass percentage of ethylbenzene in the xylene isomerization feedstock is 1-20%, based on the mass of the xylene isomerization feedstock; the xylene isomerization reaction temperature is 375-395℃, the pressure is 0.8-1.5 MPa, the hydrogen-to-hydrocarbon molar ratio is 2.5-3.5, and the weight hourly space velocity of the xylene isomerization catalyst is 3-6 h⁻¹. -1 .

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