Xylene isomerization catalyst and liquid-phase non-hydrogen-dependent xylene isomerization method

Abstract

This invention relates to the field of xylene isomerization, specifically to a xylene isomerization catalyst and a method for liquid-phase non-hydrogenated xylene isomerization. Based on the total weight of the catalyst, the catalyst comprises 10-80% by mass of a molecular sieve mixture and 20-90% by mass of a binder; wherein, based on the total weight of the molecular sieve mixture, the molecular sieve mixture comprises 10-80% by mass of Beta molecular sieve, 10-80% by mass of ZSM-5 molecular sieve, and 10-80% by mass of ZSM-11 molecular sieve. This invention involves mixing the proportionally mixed Beta molecular sieve (β molecular sieve), ZSM-5 molecular sieve, and ZSM-11 molecular sieve with a binder, extruding the mixture into strips, and then subjecting it to ion exchange, molding, drying, and calcination to produce the xylene isomerization catalyst, eliminating the need for precious metal loading, activation, and reduction processes.

Description

Technical Field

[0001] This invention relates to the field of xylene isomerization, and more specifically to a method for isomerization of xylene isomerization catalyst and non-hydroxylene in the liquid phase. Background Technology

[0002] Para-xylene (PX) is an important chemical raw material, mainly used in the production of terephthalic acid, ethylene terephthalate, and butylene glycol ester. In addition, it can be used in coatings, dyes, pesticides, and pharmaceuticals. With the continuous development of these industries in my country, the demand for PX is growing rapidly. To meet market demand, the construction scale of aromatic hydrocarbon complexes, which mainly produce PX and include technical units such as C8 aromatic isomerization, xylene distillation, and adsorption or crystallization separation, is constantly expanding.

[0003] Among them, the xylene isomerization unit technology for increasing PX production is a key step in converting ethylbenzene, m-xylene, and o-xylene into PX. Typically, aromatic hydrocarbon complexes use traditional methods such as crystallization or molecular sieve adsorption to separate pure p-xylene; then, small amounts of light non-aromatic hydrocarbons, benzene, toluene, and C9 are added. + After the heavy aromatics are separated, the remaining C8 aromatics can be used as isomerization feedstock. In the xylene isomerization unit, the three xylene isomers in the C8 aromatics (i.e., 52–54% by mass of m-xylene, 23–24% by mass of p-xylene, and 23–24% by mass of o-xylene) reach or approach thermodynamic equilibrium, and are then recycled back to the separation unit for purification to obtain p-xylene. However, ethylbenzene in the C8 aromatics requires higher isomerization temperatures and conditions such as hydrogenation to be converted to xylene or deethylated to produce benzene.

[0004] In recent years, with the continuous advancement of combined processes, there are various methods to ensure that the mixed C8 aromatics in the isomerization feed are essentially free of ethylbenzene. This allows for the catalytic isomerization of o-xylene and m-xylene at lower temperatures and in the liquid phase under conditions where the catalyst is not exposed to hydrogen or relies solely on dissolved hydrogen to maintain catalyst stability, thereby significantly reducing the energy and material consumption in PX production.

[0005] CN109399660A discloses a hierarchical porous molecular sieve and a catalyst prepared from the molecular sieve, specifically a hierarchical porous Beta molecular sieve and its Ca-Ni type catalyst, as well as a preparation method. It provides a bifunctional template agent to meet the needs of preparing hierarchical porous molecular sieves, and further modifies it to prepare a catalyst for ethanol reforming to produce hydrogen.

[0006] US9809509 uses small-grained ZSM-23 molecular sieves with a silica / alumina molar ratio between 15 and 75 as the acidic component of a catalyst for a liquid-phase isomerization reaction at 260°C for 5.2 hours. -1At an air velocity of 3.1 MPa and an operating pressure of 3.1 MPa, PX / X can be made greater than the gas phase equilibrium value of 24 by mass.

[0007] The liquid-phase non-hydrogen-dependent xylene isomerization catalyst in US20170297977A1 ​​uses UZM-54 molecular sieve, preferably with a molecular sieve content of 70%, and alumina as the binder, without the need for metal support. Under non-hydrogen-dependent conditions, the xylene isomerization reaction can reach thermodynamic equilibrium.

[0008] The catalyst prepared using Ga-MFI molecular sieves in US7371913 can perform alkyl aromatic hydrocarbon isomerization in a completely hydrogen-free state, while retaining higher levels of ethylbenzene and C8 cycloalkanes in the feedstock when the isomerization achieves good performance.

[0009] US20110263918 A1 describes a xylene isomerization process using HZSM-5 or MCM-49 as the acidic catalyst. Under conditions of below 295°C and pressure ensuring the reactants remain liquid, a xylene fraction with a near-equilibrium composition can be obtained. This process can operate continuously when the feed only requires ppm-level dissolved hydrogen. It can also be recycled with non-hydrogen-dependent feeds, but the catalyst needs periodic regeneration with low-ppm-level hydrogen.

[0010] The literature "A Study on Xylene Liquid-Phase Isomerization Catalysts" (Petrochemical Technology, Vol. 7, No. 3, 1978) investigated the performance of the ZSM-5 catalyst, synthesized from water glass, aluminum sulfate, sulfuric acid, and ethylamine, for the xylene liquid-phase isomerization reaction. Experimental results showed that the ZSM-5 zeolite catalyst exhibits high activity and selectivity for xylene liquid-phase isomerization and is suitable for mixed xylene feedstocks containing ethylbenzene.

[0011] In the aforementioned patents and literature, the xylene liquid-phase isomerization reaction exhibits high activity, but requires trace amounts of dissolved hydrogen to maintain catalyst stability. Furthermore, achieving high activity typically implies a decrease in reaction selectivity. Summary of the Invention

[0012] The main objective of this invention is to overcome at least one deficiency of the prior art and provide a method for isomerization of xylene using a xylene isomerization catalyst and a liquid-phase non-hydrogenated xylene. By employing the catalyst of this invention, the energy consumption of xylene liquid-phase isomerization is reduced, the cost of the catalyst is lowered, hydrogenation is not required, and higher xylene yield and isomerization activity are achieved.

[0013] The first aspect of the present invention provides a xylene isomerization catalyst, characterized in that, based on the total weight of the catalyst, the catalyst comprises 10-80% by mass of a molecular sieve mixture and 20-90% by mass of a binder;

[0014] The molecular sieve mixture comprises, based on the total weight of the mixture, 10-80% by mass of Beta molecular sieve, 10-80% by mass of ZSM-5 molecular sieve, and 10-80% by mass of ZSM-11 molecular sieve.

[0015] A second aspect of the present invention provides a method for liquid-phase non-hydrogenated xylene isomerization, comprising contacting an alkyl aromatic hydrocarbon with the xylene isomerization catalyst under isomerization reaction conditions to carry out an isomerization reaction.

[0016] The following beneficial effects are achieved by using the xylene isomerization catalyst and the liquid-phase non-hydrogenated xylene isomerization method provided by this invention:

[0017] By employing the xylene isomerization catalyst provided in this invention, the present invention mixes a proportionally blended Beta molecular sieve (β molecular sieve), ZSM-5 molecular sieve, and ZSM-11 molecular sieve with a binder, extrudes the mixture into strips, and then performs ion exchange, molding, drying, and calcination to produce the xylene isomerization catalyst. This eliminates the need for precious metal loading, activation, and reduction processes, simplifying the catalyst preparation process, shortening the preparation cycle, and improving preparation efficiency.

[0018] The catalyst of this invention is used for liquid-phase non-hydrogenated xylene isomerization reaction. Compared with gas-phase aromatic hydrocarbon isomerization reaction, it can achieve higher isomerization activity and xylene yield, while the reaction temperature is lower, energy consumption is significantly reduced, and it is more environmentally friendly.

[0019] In existing technologies, catalysts used in xylene isomerization reactions require the presence of trace amounts of dissolved hydrogen to maintain their stability and thus preserve good catalytic activity. Furthermore, achieving high activity typically implies a decrease in reaction selectivity. By employing the catalyst of this invention, through the synergistic effect of Beta molecular sieves, ZSM-5 molecular sieves, and ZSM-11 molecular sieves, excellent catalytic performance can be achieved without loading precious metals and without using trace amounts of dissolved hydrogen. Attached Figure Description

[0020] The following figures are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0021] Figure 1 XRD patterns of Beta molecular sieves B-1, B-2, and B-3;

[0022] Figure 2 XRD patterns of ZSM-5 molecular sieves Z-1, Z-2, and Z-3;

[0023] Figure 3 XRD patterns of ZSM-11 molecular sieves M-1, M-2, and M-3;

[0024] Figure 4 SEM images of Beta molecular sieves B-1, B-2, and B-3;

[0025] Figure 5 SEM images of Z-1, Z-2 and Z-3 of ZSM-5 molecular sieves;

[0026] Figure 6 SEM images of ZSM-11 molecular sieves M-1, M-2, and M-3. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] According to an exemplary embodiment of the present invention, a xylene isomerization catalyst is provided, characterized in that, based on the total weight of the catalyst, the catalyst comprises 10-80% by mass of a molecular sieve mixture and 20-90% by mass of a binder;

[0032] The molecular sieve mixture comprises, based on the total weight of the mixture, 10-80% by mass of Beta molecular sieve, 10-80% by mass of ZSM-5 molecular sieve, and 10-80% by mass of ZSM-11 molecular sieve.

[0033] In existing technologies, catalysts used in xylene isomerization reactions require the presence of trace amounts of dissolved hydrogen to maintain their stability and thus preserve good catalytic activity. Furthermore, achieving high activity typically implies a decrease in reaction selectivity. By employing the catalyst of this invention, the synergistic effect of Beta molecular sieves, ZSM-5 molecular sieves, and ZSM-11 molecular sieves enables excellent catalytic performance without the use of trace amounts of dissolved hydrogen. In this application, the molecular sieve mixture comprises Beta molecular sieves, ZSM-5 molecular sieves, and ZSM-11 molecular sieves, which can account for 10–80% by mass, for example, 40–80% by mass, or 50–80% by mass, based on the total weight of the catalyst.

[0034] As a preferred embodiment of the present invention, the Beta molecular sieve includes a Na-type Beta molecular sieve; the ZSM-5 molecular sieve includes a Na-type ZSM-5 molecular sieve; and the ZSM-11 molecular sieve includes a Na-type ZSM-11 molecular sieve.

[0035] This invention does not impose any particular limitation on the binder used. For example, the binder may be selected from alumina and / or silica. When alumina is selected as the binder, it can be added directly during the catalyst preparation process. Alternatively, alumina sol can be used as the aluminum source, or a mixture of alumina and alumina sol can be added. When silica is selected as the binder, it can be added directly during the catalyst preparation process. Alternatively, silica sol can be used as the silicon source, or a mixture of silica and silica sol can be added. When the binder is selected from alumina and silica, the aforementioned aluminum-containing and silicon-containing materials can be mixed in a certain proportion. Kaolin can also be used as a raw material. In this application, the binder may account for 20-90% by mass, for example, 20-80% by mass, 20-60% by mass, or 20-50% by mass, based on the total weight of the catalyst.

[0036] According to an exemplary embodiment of the present invention, the Na-type Beta molecular sieve is prepared by the following method: At least a silicon source, an aluminum source, a template agent, sodium hydroxide, and water are mixed uniformly to obtain a first mixture, wherein the amount of silicon source added is calculated as SiO2, the amount of aluminum source added is calculated as Al2O3, the molar ratio of each component in the first mixture is SiO2:Al2O3 = 20-200, preferably 25-150, and the template agent:water:SiO2 = 0.05-1.5:10-60:1, preferably the molar ratio of template agent to SiO2 is 0.08-1.4, wherein the template agent has the general formula N(R)4. + X - A quaternary ammonium base or quaternary ammonium salt, wherein R is an alkyl group having 1 to 4 carbon atoms, preferably an ethyl group, and X... -The first mixture is selected from any one of hydroxide ions, chloride ions, and bromide ions, preferably hydroxide ions; the first mixture is crystallized at 120-180°C under autogenous pressure for 60-140 hours, the solid is collected and dried.

[0037] The specific preparation process of Na-type Beta molecular sieve is as follows: In the synthesis of Na-type Beta molecular sieve, a silicon source, an aluminum source, a template agent, NaOH, and water are used. The molar ratio of silicon source, aluminum source, template agent, NaOH, and water should conform to SiO2:Al2O3:template agent:NaOH:H2O = 1:0.005~0.05:0.05~1.5:0.02~0.5:10~60. The silicon source is selected from liquid silica sol or solid silica gel. The concentration of the liquid silica sol is 10~40% by mass, preferably 30~40% by mass. The particle size of the solid silica gel is 100~500μm, preferably 150~300μm, and the pore size is 1~40nm, preferably 5~20nm. The aluminum source is selected from at least one of aluminum nitrate, aluminum chloride, and sodium aluminate, for example, aluminum chloride is used as the aluminum source. The template agent used is a quaternary ammonium base or quaternary ammonium salt with the general formula N(R)4. + X - In the formula, R is an alkyl group having 1 to 4 carbon atoms, preferably an ethyl group, and X... - The ions are hydroxide ions or halide anions (e.g., chloride ions, bromide ions), preferably hydroxide ions, and N is a nitrogen atom. The synthesis temperature of the molecular sieve is 120–180℃, preferably 135–175℃; the synthesis time is 60–140 h, preferably 96–120 h. The synthesized Na-type Beta molecular sieve has a crystal size of 30–600 nm, preferably 50–300 nm; and a silicon-to-aluminum ratio of 25–150.

[0038] According to an exemplary embodiment of the present invention, the Na-type ZSM-5 molecular sieve is prepared by the following method: At least a silicon source, an aluminum source, a template agent, sodium hydroxide, and water are mixed uniformly to obtain a second mixture, wherein the amount of silicon source added is calculated as SiO2, the amount of aluminum source added is calculated as Al2O3, the molar ratio of each component in the second mixture is SiO2:Al2O3 = 10-200, preferably 25-150, and the template agent:water:SiO2 = 0.05-1:10-60:1, preferably the molar ratio of template agent to SiO2 is 0.06-0.9, wherein the template agent has the general formula N(R)4. + X - A quaternary ammonium base or quaternary ammonium salt, wherein R is an alkyl group having 1 to 4 carbon atoms, preferably propyl, and X... - The mixture is selected from any one of hydroxide ions, chloride ions, and bromide ions, preferably hydroxide ions; the second mixture is crystallized at 140-190°C under autogenous pressure for 40-140 hours, the solid is collected and dried.

[0039] Specifically, the preparation process of Na-type ZSM-5 molecular sieve is as follows: using a silicon source, an aluminum source, a template agent, NaOH, and water. The molar ratio of silicon source, aluminum source, template agent, NaOH, and water should conform to SiO2:Al2O3:template agent:NaOH:H2O = 1:0.005~0.1:0.05~1:0.02~1:10~60. The silicon source is selected from liquid silica sol or solid silica gel. The concentration of the liquid silica sol is 10~40% by mass, preferably 30~40% by mass. The particle size of the solid silica gel is 100~500μm, preferably 150~300μm, and the pore size is 1~40nm, preferably 5~20nm. The aluminum source is selected from at least one of aluminum nitrate, aluminum chloride, and sodium aluminate, for example, aluminum nitrate is used as the aluminum source. The template agent used is a quaternary ammonium base or quaternary ammonium salt with the general formula N(R)4. + X - In the formula, R is an alkyl group having 1 to 4 carbon atoms, preferably propyl, and X... - It is a hydroxide ion or a halide anion (e.g., chloride ion, bromide ion), preferably a hydroxide ion, and N is a nitrogen atom.

[0040] The synthesis temperature of the molecular sieve is 140–190℃, preferably 175–185℃; the synthesis time is 40–140 h, preferably 96–120 h. The synthesized Na-type ZSM-5 molecular sieve has a crystal size of 0.05–10 μm, preferably 0.6–5 μm; and a silicon-to-aluminum ratio of 25–150.

[0041] According to an exemplary embodiment of the present invention, the Na-type ZSM-11 molecular sieve is prepared by the following method: At least a silicon source, an aluminum source, a template agent, sodium hydroxide, and water are mixed uniformly to obtain a third mixture, wherein the amount of silicon source added is calculated as SiO2, the amount of aluminum source added is calculated as Al2O3, the molar ratio of each component in the third mixture is SiO2:Al2O3 = 10-200, preferably 25-150, and the template agent:water:SiO2 = 0.06-1:10-60:1, preferably the molar ratio of template agent to silicon source is 0.06-0.9, and the template agent is a material having the general formula N(R)4. + X - A quaternary ammonium base or quaternary ammonium salt, wherein R is an alkyl group having 1 to 4 carbon atoms, preferably butyl, and X... - The mixture is selected from any one of hydroxide ions, chloride ions, and bromide ions, preferably hydroxide ions; the third mixture is crystallized at 120-180°C under autogenous pressure for 50-150 hours, the solid is collected and dried.

[0042] Specifically, the preparation process of Na-type ZSM-11 molecular sieve is as follows: using a silicon source, an aluminum source, a template agent, NaOH, and water. The molar ratio of silicon source, aluminum source, template agent, NaOH, and water should conform to SiO2:Al2O3:template agent:NaOH:H2O = 1:0.005~0.1:0.06~1:0.05~1:10~60. The silicon source is selected from liquid silica sol or solid silica gel. The concentration of the liquid silica sol is 10~40% by mass, preferably 30~40% by mass. The particle size of the solid silica gel is 100~500μm, preferably 150~300μm, and the pore size is 1~40nm, preferably 5~20nm. The aluminum source is selected from at least one of aluminum nitrate, aluminum chloride, and sodium aluminate, for example, aluminum nitrate or aluminum chloride is used as the aluminum source. The template agent used is a quaternary ammonium base or quaternary ammonium salt with the general formula N(R)4. + X - In the formula, R is an alkyl group having 1 to 4 carbon atoms, preferably propyl or butyl, and X... - The ions are hydroxide ions or halide anions (e.g., chloride ions, bromide ions), preferably hydroxide ions, and N is a nitrogen atom. The synthesis temperature of the molecular sieve is 120–180℃, preferably 125–150℃; the synthesis time is 50–150 h, preferably 96–150 h. The synthesized Na-type ZSM-11 molecular sieve has a crystal size of 0.05–10 μm, preferably 0.6–5 μm; and a silicon-to-aluminum ratio of 25–150.

[0043] The differences between the three types of molecular sieves can be explained based on the XRD characterization results. Different molecular sieves have different peak positions and crystal planes. XRD analysis can be performed on the products obtained from the above preparation process. Based on the XRD spectra and the characteristic peaks of Beta molecular sieve, ZSM-5 molecular sieve, and ZSM-11 molecular sieve, the type of molecular sieve obtained can be determined.

[0044] In this application, based on the total weight of the molecular sieve mixture, the molecular sieve mixture comprises 10-80% by mass of Beta molecular sieve, 10-80% by mass of ZSM-5 molecular sieve, and 10-80% by mass of ZSM-11 molecular sieve. For example, based on the total weight of the molecular sieve mixture, Beta molecular sieve may account for 10-80% by mass, for example, 12-75% by mass. Based on the total weight of the molecular sieve mixture, ZSM-5 molecular sieve may account for 10-80% by mass, for example, 12-50% by mass. Based on the total weight of the molecular sieve mixture, ZSM-11 molecular sieve may account for 10-80% by mass, for example, 12-50% by mass.

[0045] In this application, the catalyst is not supported by metals, particularly noble metals such as palladium or platinum. Even without supporting metals, particularly noble metals such as palladium or platinum, the catalyst still exhibits good catalytic activity for xylene isomerization.

[0046] According to an exemplary embodiment of the present invention, the catalyst preparation method is as follows: Beta molecular sieve, ZSM-5 molecular sieve, and ZSM-11 molecular sieve are prepared. The thoroughly washed molecular sieve powder is dried at a temperature of 100–140°C for 8–24 hours. The three molecular sieves are mixed in a certain proportion and then mixed with a binder in a certain proportion, extruded into strips, dried, and calcined. An ion exchange process is then performed, using an excess solution containing ammonium chloride, washing several times until the pH of the washing solution is 6–8. The strips are then dried at a temperature of 100–140°C for 4–24 hours. Finally, the strips are calcined in air at a temperature of 500–550°C for 2–24 hours. Calcination can be carried out 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 atmosphere. The calcined catalyst does not require metal impregnation or activation / reduction steps to obtain the catalyst product described in this invention.

[0047] According to an exemplary embodiment of the present invention, the catalyst of the present invention can be applied to a liquid-phase non-hydrogenated xylene isomerization reaction, thereby providing a second aspect of the present invention: a method for liquid-phase non-hydrogenated xylene isomerization, comprising contacting an alkyl aromatic hydrocarbon with the xylene isomerization catalyst of the present application under isomerization reaction conditions. In one embodiment, the isomerization reaction conditions include: a reaction pressure that keeps the alkyl aromatic hydrocarbon in a liquid state, a reaction temperature of 240–310°C, and a weight hourly space velocity of 1–10 h⁻¹. -1 In one embodiment, the alkyl aromatic hydrocarbon can be a C8 aromatic hydrocarbon such as m-xylene, o-xylene, ethylbenzene, and combinations thereof, particularly m-xylene, o-xylene, and combinations thereof. These alkyl aromatic hydrocarbons can be converted to p-xylene through isomerization reactions.

[0048] In existing technologies, catalysts used in xylene isomerization reactions require the presence of trace amounts of dissolved hydrogen to maintain their stability and thus preserve good catalytic activity. Furthermore, achieving high activity typically implies a decrease in reaction selectivity. By employing the catalyst of this invention, through the synergistic effect of Beta molecular sieves, ZSM-5 molecular sieves, and ZSM-11 molecular sieves, excellent catalytic performance can be achieved without the use of trace amounts of dissolved hydrogen.

[0049] The catalyst provided by this invention is used for the isomerization of C8 aromatics, which can improve the isomerization activity while maintaining good selectivity, so as to increase the production of para-xylene.

[0050] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents used in the following examples are commercially available industrial products.

[0051] The following are the test methods for performance parameters involved in this invention:

[0052] (1) Indicators of isomerization activity:

[0053] (2) Xylene yield:

[0054] The present invention will be described in detail below with examples, but the present invention is not limited thereto.

[0055] Preparation Example 1

[0056] Preparation of Na-type Beta molecular sieves:

[0057] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 2.22g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - 70.14g of Al₂O₃, 1.33g of NaOH, and 26.41g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:16:1. The synthesis temperature was 135℃, and the synthesis time was 115h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type Beta molecular sieve, denoted as B-1.

[0058] B-1 has a silicon-to-aluminum ratio of 30 and an average grain size of 230 nm. (See XRD pattern for details.) Figure 1 It is evident that this is a pure-phase molecular sieve, exhibiting not only high crystallinity and a stable baseline, but also a series of characteristic peaks at 2θ values ​​of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These characteristic peaks correspond one-to-one with the (330), (302), (304), (008), and (306) crystal planes of the Beta molecular sieve. The XRD pattern shows no other impurity peaks, indicating that the synthesized Beta molecular sieve is a pure-phase product. Its SEM image is shown below. Figure 4 .

[0059] Preparation of Na-type ZSM-5 molecular sieves:

[0060] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 3.75g of aluminum source (aluminum nitrate nonahydrate), and 4g of template agent N(C3H7) to a 200mL reactor. + OH - 81.34g of Al₂O₃, 0.8g of NaOH, and 0.972g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:31.33:1. The synthesis temperature was 175℃, and the synthesis time was 120h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type ZSM-5 molecular sieve, denoted as Z-1.

[0061] Z-1 has a silicon-to-aluminum ratio of 30 and an average grain size of 0.75 μm. The XRD pattern is shown below. Figure 2 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which represent the characteristic peaks of the (011), (020), (332), and (051) crystal planes of the H-type (cell structure) ZSM-5 molecular sieve, respectively, indicating that the Z-1 sample has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline and no impurity peaks, indicating the synthesis of a well-crystallized ZSM-5 molecular sieve. Its SEM image is attached. Figure 5 .

[0062] Preparation of Na-type ZSM-11 molecular sieves:

[0063] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 6.25g of aluminum source (aluminum nitrate nonahydrate), and 4g of template agent N(C4H9) to a 200mL reactor. + OH - 129.74g, NaOH 1g, water 39.459g. The molar ratio of each substance added is Al2O3:template agent:NaOH:H2O:SiO2 = 0.033:0.8:0.1:26.67:1.

[0064] The molecular sieve was synthesized at a temperature of 145℃ for 120 h using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain the Na-type ZSM-11 molecular sieve, denoted as M-1.

[0065] M-1 has a silicon-to-aluminum ratio of 30 and an average grain size of 0.79 μm. See attached XRD pattern. Figure 3The XRD pattern shows two diffraction peaks at 2θ = 7.9°, 8.8°, and 22.5–25.5° (with a single peak at 2θ = 45.2°), which are typical characteristic peaks of ZSM-11 molecular sieves, indicating that the synthesized ZSM-11 molecular sieve has a typical MEL structure. Meanwhile, the XRD pattern shows a stable baseline and no impurity peaks, indicating that a well-crystallized ZSM-11 molecular sieve was synthesized. Its SEM image is attached. Figure 6 .

[0066] Preparation Example 2

[0067] Preparation of Na-type Beta molecular sieves:

[0068] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 1.11g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - 52.61g of Al₂O₃, 0.5g of NaOH, and 46.81g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.017:0.5:0.05:18:1. The synthesis temperature was 140℃, and the synthesis time was 115h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type Beta molecular sieve, denoted as B-2.

[0069] B-2 has a silicon-to-aluminum ratio of 60 and an average grain size of 180 nm. (See XRD pattern for details.) Figure 1 It is evident that this is a pure-phase molecular sieve, exhibiting not only high crystallinity and a stable baseline, but also a series of characteristic peaks at 2θ values ​​of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These characteristic peaks correspond one-to-one with the (330), (302), (304), (008), and (306) crystal planes of the Beta molecular sieve. The XRD pattern shows no other impurity peaks, indicating that the synthesized Beta molecular sieve is a pure-phase product. Its SEM image is attached. Figure 4 .

[0070] Preparation of Na-type ZSM-5 molecular sieves:

[0071] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 1.88g of aluminum source (aluminum nitrate nonahydrate), and 4g of template agent N(C3H7) to a 200mL reactor. + OH -61g of Al₂O₃, 0.6g of NaOH, and 0.834g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.017:0.5:0.1:25.33:1. The synthesis temperature was 180℃, and the synthesis time was 96h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type ZSM-5 molecular sieve, denoted as Z-2.

[0072] Z-2 has a silicon-to-aluminum ratio of 60 and an average grain size of 0.8 μm. The XRD pattern is shown below. Figure 2 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which represent the characteristic peaks of the (011), (020), (332), and (051) crystal planes of the H-type ZSM-5 molecular sieve, respectively, indicating that the Z-1 sample has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline and no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM image is attached. Figure 5 .

[0073] Preparation of Na-type ZSM-11 molecular sieves:

[0074] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 0.667g of aluminum source (aluminum chloride), and 4g of template agent N(C4H9) to a 200mL reactor. + OH - 58.38g, NaOH 0.8g, water 2.47g.

[0075] The molar ratio of the feed materials was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.017:0.6:0.133:21.67:1. The synthesis temperature was 135℃, and the synthesis time was 130 h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain the Na-type ZSM-11 molecular sieve, denoted as M-2.

[0076] M-2 has a silicon-to-aluminum ratio of 60 and an average grain size of 0.95 μm. See attached XRD pattern. Figure 3 The XRD pattern shows two diffraction peaks at 2θ = 7.9°, 8.8°, and 22.5–25.5° (with a single peak at 2θ = 45.2°), which are typical characteristic peaks of ZSM-11 molecular sieves, indicating that the synthesized ZSM-11 molecular sieve has a typical MEL structure. Simultaneously, the XRD pattern shows a stable baseline and no impurity peaks, indicating that a well-crystallized ZSM-11 molecular sieve was synthesized. Its SEM image is attached. Figure 6 .

[0077] Preparation Example 3

[0078] Preparation of Na-type Beta molecular sieves:

[0079] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 0.833g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - 39.46g of Al₂O₃, 0.375g of NaOH, and 41.85g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.0125:0.375:0.0375:15:1. The synthesis temperature was 155℃, and the synthesis time was 105h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type Beta molecular sieve, denoted as B-3.

[0080] B-3 has a silicon-to-aluminum ratio of 80 and an average grain size of 260 nm. (See XRD pattern for details.) Figure 1 It is evident that this is a pure-phase molecular sieve, exhibiting not only high crystallinity and a stable baseline, but also a series of characteristic peaks at 2θ values ​​of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These characteristic peaks correspond one-to-one with the (330), (302), (304), (008), and (306) crystal planes of the Beta molecular sieve. The XRD pattern shows no other impurity peaks, indicating that the synthesized Beta molecular sieve is a pure-phase product. Its SEM image is attached. Figure 4 .

[0081] Preparation of Na-type ZSM-5 molecular sieves:

[0082] Add 22.5 g of silicon source (liquid silica sol, concentration 40% by mass), 1.406 g of aluminum source (aluminum nitrate nonahydrate), and 4 g of template agent N(C3H7) to a 200 mL reactor. + OH - 30.504g of Al₂O₃, 0.45g of NaOH, and 0.814g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.0125:0.25:0.075:14:1. The synthesis temperature was 180℃, and the synthesis time was 100h. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried to obtain Na-type ZSM-5 molecular sieve, denoted as Z-3.

[0083] Z-3 has a silicon-to-aluminum ratio of 80 and an average grain size of 1 μm. (See XRD pattern for details.) Figure 2Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which represent the characteristic peaks of the (011), (020), (332), and (051) crystal planes of the H-type ZSM-5 molecular sieve, respectively, indicating that the Z-1 sample has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline and no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM image is attached. Figure 5 .

[0084] Preparation of Na-type ZSM-11 molecular sieves:

[0085] Add 22.5 g of silicon source (liquid silica sol, concentration 40% by mass), 0.5 g of aluminum source (aluminum chloride), and 4 g of template agent N(C4H9) to a 200 mL reactor. + OH - 48.65g of Al₂O₃, 0.75g of NaOH, and 18.06g of water were added. The molar ratio of each substance was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.0125:0.5:0.0125:22.5:1. The synthesis temperature was 140℃, and the synthesis time was 140h. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried to obtain Na-type ZSM-11 molecular sieve, denoted as M-3.

[0086] M-3 has a silicon-to-aluminum ratio of 80 and an average grain size of 1.1 μm. See attached XRD pattern. Figure 3 The XRD pattern shows two diffraction peaks at 2θ = 7.9°, 8.8°, and 22.5–25.5° (with a single peak at 2θ = 45.2°), which are typical characteristic peaks of ZSM-11 molecular sieves, indicating that the synthesized ZSM-11 molecular sieve has a typical MEL structure. Simultaneously, the XRD pattern shows a stable baseline and no impurity peaks, indicating that a well-crystallized ZSM-11 molecular sieve was synthesized. Its SEM image is attached. Figure 6 .

[0087] Example 1

[0088] Catalyst preparation:

[0089] The prepared Beta molecular sieve B-1, ZSM-5 molecular sieve Z-1, and ZSM-11 molecular sieve M-1 were thoroughly mixed with alumina at a mass ratio of 5:1:1:3 to obtain a homogeneous mixture. A 5% by mass nitric acid aqueous solution was added and kneaded until homogeneous, with the nitric acid aqueous solution accounting for 35% by mass of the homogeneous mixture. The mixture was then extruded into strips to obtain strips.

[0090] The strip material was dried at 120℃ for 6 hours, then granulated (particle size 2-10 cm), and then calcined in air at 540℃ for 4 hours. After calcination, it was subjected to ion exchange with a 5% (w / w) ammonium chloride aqueous solution at 90℃ for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 120℃ for 6 hours, and then calcined at 540℃ for 4 hours to obtain catalyst C-1.

[0091] Example 2

[0092] Catalyst preparation:

[0093] The prepared Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, and ZSM-11 molecular sieve M-2 were thoroughly mixed with alumina at a mass ratio of 4:2:1:3 to obtain a homogeneous mixture. Then, catalyst C-2 was obtained according to the catalyst preparation method in Example 1.

[0094] Example 3

[0095] Catalyst preparation:

[0096] The prepared Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, and ZSM-11 molecular sieve M-3 were thoroughly mixed with alumina at a mass ratio of 3:2:2:3 to obtain a homogeneous mixture. Then, catalyst C-3 was obtained according to the catalyst preparation method in Example 1.

[0097] Example 4

[0098] Catalyst C-4 was obtained according to the catalyst preparation method in Example 1, except that the mass ratio of Beta molecular sieve B-1, ZSM-5 molecular sieve Z-1, ZSM-11 molecular sieve M-1 to alumina was 3:1:3:3.

[0099] Example 5

[0100] Catalyst C-5 was obtained according to the catalyst preparation method in Example 1, except that the mass ratio of Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, ZSM-11 molecular sieve M-2 to alumina was 2:3:2:3.

[0101] Example 6

[0102] Catalyst C-6 was obtained according to the catalyst preparation method in Example 1, except that the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, ZSM-11 molecular sieve M-3 to alumina was 1:3:3:3.

[0103] Comparative Example 1

[0104] Catalyst D-1 was obtained according to the catalyst preparation method in Example 1, except that ZSM-5 molecular sieve and ZSM-11 molecular sieve were not added to the catalyst, and the mass ratio of Beta molecular sieve B-1 to alumina was 7:3.

[0105] Comparative Example 2

[0106] Catalyst D-2 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve and ZSM-11 molecular sieve were not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-1 to alumina was 7:3.

[0107] Comparative Example 3

[0108] Catalyst D-3 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve and ZSM-5 molecular sieve were not added to the catalyst, and the mass ratio of ZSM-11 molecular sieve M-1 to alumina was 7:3.

[0109] Comparative Example 4

[0110] Catalyst D-4 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve was not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-3, ZSM-11 molecular sieve M-3, and alumina was 3:4:3.

[0111] Comparative Example 5

[0112] Catalyst D-5 was obtained according to the catalyst preparation method in Example 1, except that ZSM-5 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-3, ZSM-11 molecular sieve M-3, and alumina was 2:5:3.

[0113] Comparative Example 6

[0114] Catalyst D-6 was obtained according to the catalyst preparation method in Example 1, except that ZSM-11 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3 to alumina was 1:6:3.

[0115] test

[0116] In a small, continuously flowing fixed-bed apparatus, 3 grams of catalyst were loaded, and the catalyst performance was evaluated using feedstocks with the compositions described in Table 1. The evaluation conditions were: 250°C, 2 MPa, and a feed mass hourly space velocity (WHSV) of 2 h⁻¹. -1 .

[0117] The catalysts used in each embodiment and comparative example and the reaction results are shown in Tables 2 and 3.

[0118] Table 1

[0119] <![CDATA[C8NA]]> B T EB PX MX OX <![CDATA[C9 + ]]> 0.355 0.000 0.000 4.760 0.085 65.194 29.531 0.000

[0120] The values ​​in the table represent mass percentages in wt%, where C8NA represents C8 non-aromatic hydrocarbons, B represents benzene, T represents toluene, EB represents ethylbenzene, PX represents p-xylene, MX represents m-xylene, OX represents o-xylene, and C9... + Representing C9 + Aromatic hydrocarbons.

[0121] Table 2

[0122]

[0123] Table 3

[0124]

[0125] As shown in Tables 2 and 3, the catalysts prepared by the methods of Examples 1 to 6 of this invention have higher isomerization activity (PX / ∑X) and higher xylene yield than the catalysts of Comparative Examples 1 to 6. This indicates that the method of this invention, which uses a combination of three molecular sieves as the active component of the catalyst, has better isomerization activity and selectivity than using only one or two molecular sieves as the active component.

[0126] 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 xylene isomerization catalyst, characterized in that, Based on the total weight of the catalyst, the catalyst comprises 10-80% by mass of a molecular sieve mixture and 20-90% by mass of a binder; The molecular sieve mixture comprises, based on the total weight of the mixture, 10-80% by mass of Beta molecular sieve, 10-80% by mass of ZSM-5 molecular sieve, and 10-80% by mass of ZSM-11 molecular sieve. The Beta molecular sieve includes a Na-type Beta molecular sieve; the ZSM-5 molecular sieve includes a Na-type ZSM-5 molecular sieve; the ZSM-11 molecular sieve includes a Na-type ZSM-11 molecular sieve. The Na-type Beta molecular sieve is prepared by the following method: at least a silicon source, an aluminum source, a template agent, sodium hydroxide and water are mixed evenly to obtain a first mixture, the first mixture is crystallized at 120~180 °C under autogenous pressure for 60~140 h, the solid is collected and dried; The Na-type ZSM-5 molecular sieve is prepared by the following method: at least a silicon source, an aluminum source, a template agent, sodium hydroxide and water are mixed evenly to obtain a second mixture, the second mixture is crystallized at 140~190℃ under autogenous pressure for 40~140 h, the solid is collected and dried; The Na-type ZSM-11 molecular sieve is prepared by the following method: at least a silicon source, an aluminum source, a template agent, sodium hydroxide and water are mixed evenly to obtain a third mixture, the third mixture is crystallized at 120~180℃ under autogenous pressure for 50~150 h, the solid is collected and dried.

2. The catalyst according to claim 1, wherein, The binder is selected from alumina and / or silicon dioxide.

3. The catalyst according to claim 1, wherein, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the first mixture is SiO2:Al2O3 = 20 ~ 200, and the template agent:water:SiO2 = 0.05~1.5:10~60:

1. The template agent has the general formula N(R)4. + X - Quaternary ammonium bases or salts, where R is an alkyl group having 1 to 4 carbon atoms, X... - It is selected from any one of hydroxide ions, chloride ions, and bromide ions.

4. The catalyst according to claim 3, wherein, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the first mixture is SiO2:Al2O3 = 25~150. The template agent has the general formula N(R)4. + X - Quaternary ammonium bases or quaternary ammonium salts, where R is ethyl and X is ethyl. - It is a hydroxide ion.

5. The catalyst according to claim 1, characterized in that, The molar ratio of NaOH to SiO2 in the first mixture is 0.02 to 0.5; And / or, the molar ratio of template agent to SiO2 in the first mixture is 0.08~1.4; And / or, the first mixture is crystallized at 135~175 °C under autogenous pressure for 96~120 h.

6. The catalyst according to claim 1, characterized in that, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the second mixture is SiO2:Al2O3 = 10 ~ 200, and the template agent:water:SiO2 = 0.05~1 : 10~60 :

1. The template agent is a material with the general formula N(R)4. + X - Quaternary ammonium bases or salts, where R is an alkyl group having 1 to 4 carbon atoms, X - It is selected from any one of hydroxide ions, chloride ions, and bromide ions.

7. The catalyst according to claim 6, characterized in that, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the second mixture is SiO2:Al2O3 = 25~150. The template agent has the general formula N(R)4. + X - Quaternary ammonium bases or quaternary ammonium salts, where R is propyl and X is... - It is a hydroxide ion.

8. The catalyst according to claim 1, characterized in that, The molar ratio of NaOH to SiO2 in the second mixture is 0.02 ~ 1; And / or, the molar ratio of template agent to SiO2 in the second mixture is 0.06~0.9; And / or, the second mixture is crystallized at 175-185 °C under autogenous pressure for 96-120 h.

9. The catalyst according to claim 1, characterized in that, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the third mixture is SiO2:Al2O3 = 10 ~ 200, and the template agent:water:SiO2 = 0.06~1 : 10~60 :

1. The template agent has the general formula N(R)4. + X - Quaternary ammonium bases or salts, where R is an alkyl group having 1 to 4 carbon atoms, X - It is selected from any one of hydroxide ions, chloride ions, and bromide ions.

10. The catalyst according to claim 9, characterized in that, The amount of silicon source added is calculated as SiO2, and the amount of aluminum source added is calculated as Al2O3. The molar ratio of each component in the third mixture is SiO2:Al2O3 = 25~150, and the template agent:water:SiO2 = 0.06~1 : 10~60 :

1. The template agent has the general formula N(R)4. + X - Quaternary ammonium bases or quaternary ammonium salts, where R is butyl and X is... - It is a hydroxide ion.

11. The catalyst according to claim 9, characterized in that, The molar ratio of NaOH to SiO2 in the third mixture is 0.05 to 1. And / or, the molar ratio of template agent to SiO2 in the third mixture is 0.06~0.9; And / or, the third mixture is crystallized at 125-150 °C under autogenous pressure for 96-150 h.

12. The catalyst according to claim 1, characterized in that, The silicon source is selected from liquid silica sol or solid silica gel. The concentration of the liquid silica sol is 10-40% by mass, and the particle size of the solid silica gel is 100-500 μm with a pore size of 1-40 nm.

13. The catalyst according to claim 12, characterized in that, The concentration of the liquid silica sol is 30-40% by mass, and the particle size of the solid silica gel is 150-300 μm with a pore size of 5-20 nm.

14. The catalyst according to claim 1, characterized in that, The Na-type Beta molecular sieve has a grain size of 30~600 nm and a silicon-to-aluminum ratio of 25-150; the Na-type ZSM-5 molecular sieve has a grain size of 0.05~10 μm and a silicon-to-aluminum ratio of 25-150; the Na-type ZSM-11 molecular sieve has a grain size of 0.05~10 μm and a silicon-to-aluminum ratio of 25-150.

15. The catalyst according to claim 14, characterized in that, The Na-type Beta molecular sieve has a crystal size of 50~300 nm; the Na-type ZSM-5 molecular sieve has a crystal size of 0.6~5 μm; and the Na-type ZSM-11 molecular sieve has a crystal size of 0.6~5 μm.

16. A method for liquid-phase non-hydrogenated xylene isomerization, comprising contacting an alkyl aromatic hydrocarbon with the xylene isomerization catalyst according to any one of claims 1 to 15 under isomerization reaction conditions to carry out an isomerization reaction.

17. The method of claim 16, wherein, The isomerization reaction conditions include: a reaction pressure that keeps the alkyl aromatic hydrocarbon in a liquid state, a reaction temperature of 240–310 °C, and a weight hourly space velocity of 1–10 h⁻¹. -1 .

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