Liquid-phase xylene isomerization catalyst, preparation method thereof and liquid-phase xylene isomerization reaction

Abstract

The invention provides a liquid-phase xylene isomerization catalyst, a preparation method thereof and a liquid-phase xylene isomerization reaction, the liquid-phase xylene isomerization catalyst comprises 10-80% of an H-type molecular sieve and 20-90% of a binder, and the H-type molecular sieve comprises 5-90% of a ZSM-5 molecular sieve, 5-90% of a Beta molecular sieve and 5-90% of an MOR molecular sieve. According to the liquid-phase xylene isomerization catalyst, the H-type ZSM-5 molecular sieve, the Beta molecular sieve and the MOR molecular sieve serve as active components, the three molecular sieves can achieve a synergistic effect, the catalyst has high p-xylene selectivity, and high p-xylene isomerization activity and high xylene yield can be obtained at the same time.

Description

Technical Field

[0001] This invention relates to the field of xylene isomerization technology, specifically to a liquid-phase xylene isomerization catalyst and its preparation method, and a liquid-phase xylene isomerization reaction. Background Technology

[0002] Para-xylene (PX) is an important chemical raw material, mainly used in the production of terephthalic acid, and further in the production of ethylene glycol terephthalate, butylene terephthalate, and other products. 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 has grown rapidly. To meet market demand, the construction scale of aromatic hydrocarbon complexes, mainly producing PX, is constantly expanding. These complexes consist of C8 aromatic hydrocarbon isomerization, xylene distillation, and adsorption or crystallization separation technologies. Among them, the xylene isomerization unit technology for increasing PX production is a key means to convert ethylbenzene, m-xylene, and o-xylene into PX. Typically, aromatic hydrocarbon complexes use traditional crystallization or molecular sieve adsorption methods to separate pure PX. The remaining C8 aromatic hydrocarbons, after being processed by a heptane removal tower and a xylene removal tower to remove small amounts of light non-aromatic hydrocarbons, benzene, toluene, and C9+ heavy aromatic hydrocarbons, can be used as isomerization feedstock. After passing through the xylene isomerization unit, the three xylene isomers in C8 aromatics can reach or approach thermodynamic equilibrium composition, namely 52-54% by mass of m-xylene, 23-24% by mass of p-xylene, and 23-24% by mass of o-xylene, which are then recycled back to the separation unit for purification of p-xylene. However, ethylbenzene in the C8 aromatic feed requires higher isomerization temperatures and conditions such as hydrogenation to be converted into xylene or deethylated to produce benzene. In recent years, with the continuous advancement of combined processes, various methods have been developed 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 of non-hydrogenation or relying solely on dissolved hydrogen to maintain catalyst stability, thereby significantly reducing energy and material consumption in PX production.

[0003] Taking into account the process design and power consumption of the device, selecting non-hydrogen-contaminated liquid phase conditions for the isomerization reaction unit is a technical solution with unique advantages.

[0004] Patent CN111250164B provides a method for preparing modified MOR molecular sieve catalysts. The method uses selective silicon deposition to obtain catalysts with good reaction selectivity and low-temperature activity, which is beneficial for olefin desorption and delaying polymerization, aromatization and coking reactions, thereby improving the catalyst's operational stability and ethylene yield.

[0005] In patent US20170297977A1, the liquid-phase non-hydrogenated xylene isomerization catalyst 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-hydrogenated conditions, the xylene isomerization reaction can reach thermodynamic equilibrium.

[0006] The catalyst prepared using Ga-MFI molecular sieves in patent US7371913 can perform alkyl aromatic hydrocarbon isomerization in a completely hydrogen-free state, and retains higher levels of ethylbenzene and C8 cycloalkanes in the feedstock when the isomerization achieves good performance.

[0007] 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 are in a liquid state, a xylene fraction with a near-equilibrium composition can be obtained. Only ppm-level dissolved hydrogen is required in the feed, and the process can operate continuously. It can also be recycled with non-hydrogen-dependent feeds, but the catalyst needs periodic regeneration with low-ppm-level hydrogen.

[0008] The literature "A Study on Xylene Liquid-Phase Isomerization Catalysts" (Petrochemical Technology, Vol. 7, No. 3, 1978) investigated the performance of xylene liquid-phase isomerization reaction on the ZSM-5 catalyst, synthesized from water glass, aluminum sulfate, sulfuric acid, and ethylamine. 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.

[0009] 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. Finding an isomerization catalyst that simultaneously possesses high p-xylene isomerization activity and xylene yield, while also reducing energy consumption and catalyst cost, is a pressing technical problem that needs to be solved. Summary of the Invention

[0010] To address the above problems, this invention provides a liquid-phase xylene isomerization catalyst, its preparation method, and a liquid-phase xylene isomerization reaction.

[0011] On one hand, the present invention provides a liquid-phase xylene isomerization catalyst, comprising 10-80% H-type molecular sieve and 20-90% binder, based on the mass of the liquid-phase xylene isomerization catalyst;

[0012] The H-type molecular sieve comprises the following components in the following proportions based on the total mass of the H-type molecular sieve:

[0013] ZSM-5 molecular sieve 5-90%

[0014] Beta molecular sieve 5-90%

[0015] MOR molecular sieves have a purity of 5-90%.

[0016] On the other hand, the present invention also provides a method for preparing the above-mentioned liquid-phase xylene isomerization catalyst, comprising the following steps:

[0017] (1) Provide alkali metal ion type ZSM-5 molecular sieve;

[0018] (2) Provide alkali metal ion type Beta molecular sieves;

[0019] (3) Provide alkali metal ion-type MOR molecular sieves;

[0020] (4) After mixing the alkali metal ion type ZSM-5 molecular sieve, alkali metal ion type Beta molecular sieve and alkali metal ion type MOR molecular sieve with the binder, add acid solution for kneading, molding and first calcination, then contact with ammonium salt solution for ion exchange and second calcination to obtain the liquid phase xylene isomerization catalyst.

[0021] Optionally, the preparation method of the alkali metal ion-type ZSM-5 molecular sieve in step (1) includes:

[0022] The first silicon source, the first aluminum source, the first template agent, the first alkali and water are mixed and subjected to the first crystallization synthesis to obtain the alkali metal ion type ZSM-5 molecular sieve;

[0023] The preparation method of the alkali metal ion type Beta molecular sieve in step (2) includes:

[0024] The second silicon source, the second aluminum source, the second template agent, the second alkali, and water are mixed and subjected to a second crystallization synthesis to obtain the alkali metal ion type Beta molecular sieve.

[0025] The preparation method of the alkali metal ion type MOR molecular sieve in step (3) includes:

[0026] The alkali metal ion type MOR molecular sieve is obtained by mixing the third silicon source, the third aluminum source, the third alkali, and water and then performing a third crystallization synthesis.

[0027] Optionally, the molar ratio of the first silicon source (calculated as SiO2), the first aluminum source (calculated as Al2O3), the first template agent, the first alkali, and water is 1:(0.005~0.05):(0.05~1):(0.02~1):(10~60);

[0028] The first template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R1)4. + X- R1 is selected from alkyl groups having 1 to 4 carbon atoms, preferably propyl, X - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions;

[0029] The first crystallization synthesis is carried out at 140–190°C and under autogenous pressure for 40–140 h, preferably at 175–185°C and under autogenous pressure for 96–120 h.

[0030] Optionally, the molar ratio of the second silicon source (calculated as SiO2), the second aluminum source (calculated as Al2O3), the second template agent, the second alkali, and water is 1:(0.005~0.05):(0.05~1.5):(0.02~0.5):(10~60);

[0031] The second template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R2)4. + Y - R2 is selected from alkyl groups having 1 to 4 carbon atoms, preferably ethyl, Y - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions;

[0032] The second crystallization synthesis is carried out at 120–180°C and under autogenous pressure for 60–140 h, preferably at 135–175°C and under autogenous pressure for 96–120 h.

[0033] Optionally, the molar ratio of the third silicon source (calculated as SiO2), the third aluminum source (calculated as Al2O3), the third alkali, and water is 1:(0.005~0.05):(0.1~1.5):(10~60);

[0034] The third crystallization synthesis was carried out at 110–200 °C and under autogenous pressure for 40–140 h.

[0035] Optionally, the third crystallization process can be a single-stage or two-stage crystallization, wherein the temperature of the single-stage crystallization is 170–190°C and the time is 48–96 h.

[0036] The two-stage crystallization includes a first-stage crystallization and a second-stage crystallization. The temperature of the first-stage crystallization is 110–130°C and the time is 10–24 h. The temperature of the second-stage crystallization is 150–200°C and the time is 36–96 h.

[0037] Optionally, the first silicon source, the second silicon source, and the third silicon source are each independently selected from liquid silica sol and / or solid silica gel;

[0038] 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 100-500 μm, preferably 200-400 μm.

[0039] Optionally, the grain size of the alkali metal ion type ZSM-5 molecular sieve is 0.05–10 μm, preferably 0.5–5 μm; the grain size of the alkali metal ion type Beta molecular sieve is 30–600 nm, preferably 50–300 nm; and the grain size of the alkali metal ion type MOR molecular sieve is 0.5–10 μm, preferably 0.5–5 μm.

[0040] In another aspect, the present invention also provides a liquid-phase xylene isomerization reaction, comprising contacting a raw material containing alkyl aromatics with a liquid-phase xylene isomerization catalyst under a reaction pressure that maintains a liquid state to carry out an isomerization reaction, wherein the liquid-phase xylene isomerization catalyst is the above-mentioned liquid-phase xylene isomerization catalyst or is prepared by the above-mentioned method;

[0041] Preferably, the isomerization reaction is carried out at 240–310°C and a mass hourly space velocity (WHSV) of 1–10 h⁻¹. -1 The following will proceed.

[0042] Beneficial effects:

[0043] The liquid-phase xylene isomerization catalyst of this invention uses H-type ZSM-5 molecular sieve, Beta molecular sieve and MOR molecular sieve as active components. The three molecular sieves can synergistically enhance each other, and the catalyst has high selectivity for p-xylene, which can simultaneously obtain high p-xylene isomerization activity and xylene yield. Attached Figure Description

[0044] Figure 1 The XRD diffraction pattern of the ZSM-5 molecular sieve synthesized in this embodiment of the invention;

[0045] Figure 2 The XRD diffraction pattern of the synthesized Beta molecular sieve in this embodiment of the invention;

[0046] Figure 3 The XRD diffraction pattern of the synthesized MOR molecular sieve in this embodiment of the invention is shown below.

[0047] Figure 4 Here is a SEM image of the ZSM-5 molecular sieve synthesized in this embodiment of the invention;

[0048] Figure 5 Here is a SEM image of the synthesized Beta molecular sieve in this embodiment of the invention;

[0049] Figure 6 This is a SEM image of the MOR molecular sieve synthesized in an embodiment of the present invention. Detailed Implementation

[0050] 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.

[0051] 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.

[0052] 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.

[0053] On one hand, the present invention provides a liquid-phase xylene isomerization catalyst, comprising 10-80% H-type molecular sieve and 20-90% binder, based on the mass of the liquid-phase xylene isomerization catalyst;

[0054] The H-type molecular sieve comprises the following components in the following proportions based on the total mass of the H-type molecular sieve:

[0055] ZSM-5 molecular sieve 5-90%

[0056] Beta molecular sieve 5-90%

[0057] MOR molecular sieves have a purity of 5-90%.

[0058] It should be noted that, in the liquid-phase xylene isomerization catalyst of the present invention, based on the mass of the liquid-phase xylene isomerization catalyst, the proportion of H-type molecular sieve can be 20%, 30%, 40%, 50%, 60%, 70%, etc., and the proportion of binder can be 30%, 40%, 50%, 60%, 70%, 80%, etc. Furthermore, based on the total mass of H-type molecular sieves, the proportion of ZSM-5 molecular sieve can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.; the proportion of Beta molecular sieve can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.; and the proportion of MOR molecular sieve can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc. The binder in the catalyst can specifically be alumina, etc.

[0059] The liquid-phase xylene isomerization catalyst of the present invention does not support metals such as noble metals, but when catalyzing the liquid-phase isomerization reaction of raw materials containing alkyl aromatics, the above three H-type molecular sieves can synergistically enhance each other as active components. The catalyst has high selectivity for p-xylene and can simultaneously obtain high p-xylene isomerization activity and xylene yield.

[0060] On the other hand, the present invention also provides a method for preparing the above-mentioned liquid-phase xylene isomerization catalyst, comprising the following steps:

[0061] (1) Provide alkali metal ion type ZSM-5 molecular sieve;

[0062] (2) Provide alkali metal ion type Beta molecular sieves;

[0063] (3) Provide alkali metal ion-type MOR molecular sieves;

[0064] (4) After mixing the alkali metal ion type ZSM-5 molecular sieve, alkali metal ion type Beta molecular sieve and alkali metal ion type MOR molecular sieve with the binder, add acid solution for kneading, molding and first calcination, then contact with ammonium salt solution for ion exchange and second calcination to obtain the liquid phase xylene isomerization catalyst.

[0065] It should be noted that the above three types of alkali metal ion molecular sieves can be Na-type ZSM-5 molecular sieve, Na-type Beta molecular sieve, Na-type MOR molecular sieve, or K-type molecular sieve, etc. After ion exchange and second calcination in step (4), the alkali metal ion molecular sieve is transformed into H-type molecular sieve.

[0066] Specifically, in step (4), the molding can be extrusion molding. After molding, the product can be dried, granulated, and then subjected to the first calcination. After ion exchange, the product can be washed, dried, and then subjected to the second calcination. The washing can be performed several times until there are no chloride ions in the mother liquor. Then, it can be dried at 100-140℃ for 4-24 hours. The second calcination can be carried out at 520℃-550℃ in an air atmosphere for 2-24 hours. The second calcination can be carried out in a static atmosphere without air flow, or at a volume hourly space velocity of 50-500 h⁻¹. -1 The process is carried out in a dynamic atmosphere. The calcined catalyst does not require metal impregnation, activation, or reduction steps to obtain the finished catalyst product of this invention.

[0067] The method of this invention utilizes the aforementioned three molecular sieves as active components to achieve synergistic effects in the preparation of liquid-phase xylene isomerization catalysts. It eliminates the need for loading precious metals and activation / reduction steps, resulting in lower costs, a simplified catalyst preparation process, a shorter preparation cycle, and improved catalyst preparation efficiency. The catalyst prepared by this method, when used for catalyzing liquid-phase xylene isomerization reactions, achieves higher isomerization activity and xylene yield compared to gas-phase xylene isomerization reactions, while also resulting in lower reaction temperatures, lower energy consumption, and greater environmental friendliness.

[0068] In one embodiment of the method described above, the preparation method of the alkali metal ion-type ZSM-5 molecular sieve in step (1) includes:

[0069] The first silicon source, the first aluminum source, the first template agent, the first alkali and water are mixed and subjected to the first crystallization synthesis to obtain the alkali metal ion type ZSM-5 molecular sieve;

[0070] The preparation method of the alkali metal ion type Beta molecular sieve in step (2) includes:

[0071] The second silicon source, the second aluminum source, the second template agent, the second alkali, and water are mixed and subjected to a second crystallization synthesis to obtain the alkali metal ion type Beta molecular sieve.

[0072] The preparation method of the alkali metal ion type MOR molecular sieve in step (3) includes:

[0073] The alkali metal ion type MOR molecular sieve is obtained by mixing the third silicon source, the third aluminum source, the third alkali, and water and then performing a third crystallization synthesis.

[0074] It should be noted that after preparing the three alkali metal ion-type molecular sieves according to the above method, they can be washed and dried. The thoroughly washed molecular sieve powder can be dried at 100-140℃ for 8-24 hours. The three alkali metal ion-type molecular sieves prepared according to the above method are combined to form a catalyst. When used to catalyze the liquid-phase xylene isomerization reaction of feedstocks containing alkyl aromatics, the catalyst exhibits good selectivity for p-xylene, and can simultaneously obtain high p-xylene isomerization activity and xylene yield.

[0075] In another embodiment of the method described above, the molar ratio of the first silicon source (calculated as SiO2), the first aluminum source (calculated as Al2O3), the first template agent, the first alkali, and water is 1:(0.005~0.05):(0.05~1):(0.02~1):(10~60);

[0076] The first template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R1)4. + X - R1 is selected from alkyl groups having 1 to 4 carbon atoms, preferably propyl, X - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions;

[0077] The first crystallization synthesis is carried out at 140–190°C and under autogenous pressure for 40–140 h, preferably at 175–185°C and under autogenous pressure for 96–120 h.

[0078] It should be noted that when preparing alkali metal ion-type ZSM-5 molecular sieves, the SiO2 / Al2O3 ratio in the first silicon source and first aluminum source feed meter is 20–200:1, preferably 25–150:1. Here, SiO2 / Al2O3 represents the molar ratio of SiO2 to Al2O3, and can specifically be 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, etc. The molar ratio of the first template agent to the first silicon source (based on SiO2) in the feed meter is preferably 0.06–0.9:1. After the first crystallization synthesis is completed, the solid can be collected, and the molecular sieve can be washed and dried. The first template agent is N(R1)4. + X - In this context, N represents nitrogen atoms, and the first aluminum source can be aluminum nitrate nonahydrate.

[0079] When preparing alkali metal ion-type ZSM-5 molecular sieves, by controlling the feed ratio of several raw materials and the conditions in the first crystallization synthesis process as described above, and by selecting the template agent mentioned above, the prepared alkali metal ion-type ZSM-5 molecular sieves can be combined with two other molecular sieves to prepare catalysts. The ZSM-5 molecular sieves can better exert their effects to promote the catalyst's selectivity for xylene, which is beneficial to simultaneously improving the isomerization activity of xylene and the xylene yield.

[0080] In another embodiment of the above method of the present invention, the molar ratio of the second silicon source (calculated as SiO2), the second aluminum source (calculated as Al2O3), the second template agent, the second alkali, and water is 1:(0.005~0.05):(0.05~1.5):(0.02~0.5):(10~60);

[0081] The second template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R2)4. + Y - R2 is selected from alkyl groups having 1 to 4 carbon atoms, preferably ethyl, Y - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions;

[0082] The second crystallization synthesis is carried out at 120–180°C and under autogenous pressure for 60–140 h, preferably at 135–175°C and under autogenous pressure for 96–120 h.

[0083] It should be noted that, in preparing alkali metal ion-type Beta molecular sieves, the SiO2 / Al2O3 ratio in the second silicon source and second aluminum source feed ratio is 20–200:1, preferably 25–150:1. Specifically, the SiO2 / Al2O3 ratio can be 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, etc. The preferred molar ratio of the second template agent to the second silicon source (based on SiO2) is 0.08–1.4:1. After the second crystallization synthesis is completed, the solid can be collected, and the molecular sieve can be washed and dried. The second aluminum source can be aluminum chloride, and the second template agent is N(R2)4. + Y - N in the figure represents nitrogen atoms.

[0084] When preparing alkali metal ion-type Beta molecular sieves, by controlling the feed ratio of several raw materials and the conditions in the second crystallization synthesis process as described above, and by selecting the template agent mentioned above, the prepared alkali metal ion-type Beta molecular sieves are combined with two other molecular sieves to prepare catalysts. The Beta molecular sieves can better synergize with the other two molecular sieves, and the resulting catalysts can obtain high p-xylene isomerization activity and xylene yield in the catalytic liquid-phase xylene isomerization reaction.

[0085] In one embodiment of the method described above, the molar ratio of the third silicon source (calculated as SiO2), the third aluminum source (calculated as Al2O3), the third alkali, and water is 1:(0.005~0.05):(0.1~1.5):(10~60);

[0086] The third crystallization synthesis was carried out at 110–200 °C and under autogenous pressure for 40–140 h.

[0087] It should be noted that no template agent is required when preparing alkali metal ion-type MOR molecular sieves. The SiO2 / Al2O3 ratio in the third silicon source and third aluminum source feed ratio is 20–200:1, preferably 20–30:1. Specific SiO2 / Al2O3 ratios can also be 25:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, 150:1, 180:1, etc. After the third crystallization synthesis is completed, the solid can be collected, and the molecular sieve can be washed and dried. The third aluminum source can be SB powder, aluminum sulfate, or sodium aluminate.

[0088] When preparing alkali metal ion-type MOR molecular sieves, by controlling the feed ratio of several raw materials and the conditions of the third crystallization synthesis as described above, the prepared alkali metal ion-type MOR molecular sieves can be better compounded with the other two molecular sieves, and the resulting catalyst has better selectivity for p-xylene.

[0089] In one embodiment of the above method of the present invention, the third crystallization synthesis is a single-stage crystallization or a two-stage crystallization, wherein the temperature of the single-stage crystallization is 170-190°C and the time is 48-96h;

[0090] The two-stage crystallization includes a first-stage crystallization and a second-stage crystallization. The temperature of the first-stage crystallization is 110–130°C and the time is 10–24 h. The temperature of the second-stage crystallization is 150–200°C and the time is 36–96 h.

[0091] It should be noted that, when preparing alkali metal ion-type MOR molecular sieves, controlling the conditions of the third crystallization synthesis as described above can further improve the performance of the prepared alkali metal ion-type MOR molecular sieves. The catalyst prepared by combining the alkali metal ion-type MOR molecular sieve synthesized under these conditions with ZSM-5 molecular sieves and Beta molecular sieves can achieve higher p-xylene isomerization activity and xylene yield when used to catalyze the liquid-phase xylene isomerization reaction.

[0092] In one embodiment of the method described above, the first silicon source, the second silicon source, and the third silicon source are each independently selected from liquid silica sol and / or solid silica gel.

[0093] 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 100-500 μm, preferably 200-400 μm.

[0094] It should be noted that by using liquid silica sol of the above concentration, or by controlling the particle size of solid silica as described above, such a silicon source can prepare alkali metal ion molecular sieves with better and more stable performance.

[0095] In one embodiment of the method described above, the crystal size of the alkali metal ion type ZSM-5 molecular sieve is 0.05–10 μm, preferably 0.5–5 μm; the crystal size of the alkali metal ion type Beta molecular sieve is 30–600 nm, preferably 50–300 nm; and the crystal size of the alkali metal ion type MOR molecular sieve is 0.5–10 μm, preferably 0.5–5 μm.

[0096] It should be noted that by controlling the crystal size of the three alkali metal ion molecular sieves as described above, the liquid-phase xylene isomerization catalyst used to catalyze the isomerization of C8 aromatics can better increase the production of para-xylene while maintaining good selectivity.

[0097] In another aspect, the present invention also provides a liquid-phase xylene isomerization reaction, comprising contacting a raw material containing alkyl aromatics with a liquid-phase xylene isomerization catalyst under a reaction pressure that maintains a liquid state to carry out an isomerization reaction, wherein the liquid-phase xylene isomerization catalyst is the above-mentioned liquid-phase xylene isomerization catalyst or is prepared by the above-mentioned method;

[0098] Preferably, the isomerization reaction is carried out at 240–310°C and a mass hourly space velocity (WHSV) of 1–10 h⁻¹. -1 The following will proceed.

[0099] It should be noted that the alkyl aromatics in the feedstock may include C8 aromatics, such as ethylbenzene (EB), o-xylene (OX), m-xylene (MX), and optionally p-xylene (PX), and may also include C8NA, optional benzene, and optional C9... + The proportion of ethylbenzene in the raw materials can be 1-10%, o-xylene can be 20-40%, m-xylene can be 50-80%, and p-xylene can be 0-1%. The isomerization reaction temperature can be 250℃, 260℃, 270℃, 280℃, 290℃, etc., and the mass hourly space velocity (WHSV) can be 2 h⁻¹. -1 3h -1 4h -1 5h -1 6h -1 7h -1 8h -1 wait.

[0100] The present invention will be further described in detail below through embodiments, but these embodiments do not limit the scope of the invention. Unless otherwise specified, the experimental instruments and raw materials involved in the following embodiments are commercially available products.

[0101] Example 1

[0102] 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 - The molecular sieve consisted of 81.34 g of a 25% (w / w) aqueous solution, 0.8 g of NaOH, and 0.972 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:31.33:1. The synthesis temperature was 175℃, and the synthesis time was 120 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0103] The obtained ZSM-5 molecular sieve, denoted as Z-1, has a silica-to-alumina ratio of 30 and an average grain size of 0.75 μm. The XRD diffraction pattern is attached. Figure 1Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5, representing the (011), (020), (332), and (051) crystal planes of ZSM-5 molecular sieve, respectively, indicating that the catalyst 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 characterization is shown in the appendix. Figure 4 .

[0104] 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 - The molecular sieve consisted of 70.14 g of a 35% (w / w) aqueous solution, 1.33 g of NaOH, and 26.41 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:16:1. The synthesis temperature was 135℃, and the synthesis time was 115 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0105] The obtained Beta molecular sieve, designated B-1, has a silica-to-alumina ratio of 30 and an average grain size of 230 nm. The XRD diffraction pattern is attached. Figure 2 It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 5 .

[0106] 30g of silicon source (solid silica sol), 3.446g of aluminum source (SB powder), 3.2g of NaOH, and 84.1g of water were added to a 200mL reactor. The molar ratio of the added substances was Al₂O₃:NaOH:H₂O:SiO₂ = 0.05:0.16:10:1. A two-stage synthesis method was used: the first stage was at 120℃ for 12 hours, and the second stage was at 180℃ for 48 hours, employing a dynamic synthesis method for the molecular sieve. The molecular sieve was then washed and dried.

[0107] The obtained MOR molecular sieve, denoted as S-1, has a silica-to-alumina ratio of 20 and an average grain size of 2.5 μm. The XRD diffraction pattern is attached. Figure 3 The diffraction peaks appearing at 2θ = 6.5°, 8.6°, 9.78°, 13.44°, 15.36°, 19.6°, 22.2°, 25.7°, 26.36°, and 27.67° are typical characteristic diffraction peaks of MOR molecular sieves. Meanwhile, the XRD pattern shows a stable baseline and no impurity peaks, indicating the synthesis of a well-crystallized MOR molecular sieve. Its SEM characterization is shown in the appendix. Figure 6 .

[0108] ZSM-5 molecular sieve Z-1, Beta molecular sieve B-1, and MOR molecular sieve S-1 were thoroughly mixed with alumina at a mass ratio of 5:1:1:3. A 5% (w / w) nitric acid aqueous solution was added and kneaded until homogeneous, with the nitric acid aqueous solution accounting for 35% of the mass of the solid mixture. The mixture was then extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 120°C for 6 hours, and calcined at 540°C for 4 hours to obtain catalyst C-1.

[0109] Example 2

[0110] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 1.88g of aluminum source (aluminum nitrate nonahydrate), and N(C3H7)4 to a 200mL reactor. + OH - 61g (25% by mass aqueous solution), 0.6g NaOH, and 0.834g water were added. The molar ratio of the added substances was Al2O3:template:NaOH:H2O:SiO2 = 0.017:0.5:0.1:25.33:1. The synthesis temperature was 180℃, and the synthesis time was 96 hours. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried.

[0111] The obtained ZSM-5 molecular sieve, designated Z-2, has a silica-to-alumina ratio of 60 and an average grain size of 0.52 μm. The XRD diffraction pattern is attached. Figure 1 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5. These peaks represent the (011), (020), (332), and (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline with no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM characterization is shown in the appendix. Figure 4 .

[0112] 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 - The molecular sieve consisted of 52.61 g of a 35% (w / w) aqueous solution, 0.5 g of NaOH, and 46.81 g of water. The molar ratio of the additives was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.017:0.5:0.05:18:1. The synthesis temperature was 140℃, and the synthesis time was 115 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0113] The obtained Beta molecular sieve, designated B-2, has a silica-to-alumina ratio of 60 and an average grain size of 180 nm. The XRD diffraction pattern is attached. Figure 2 It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 5 .

[0114] 30 g of silicon source (solid silica sol), 2.757 g of aluminum source (SB powder), 3.6 g of NaOH, and 89.28 g of water were added to a 200 mL reactor. The molar ratio of the added substances was Al₂O₃:NaOH:H₂O:SiO₂ = 0.04:0.18:10:1. The synthesis temperature was 180℃, and the synthesis time was 72 hours, using a dynamic synthesis method to synthesize the molecular sieve. The molecular sieve was then washed and dried.

[0115] The obtained MOR molecular sieve, designated S-2, has a silica-to-alumina ratio of 25 and an average grain size of 1.8 μm. The XRD diffraction pattern is attached. Figure 3 The diffraction peaks appearing at 2θ = 6.5°, 8.6°, 9.78°, 13.44°, 15.36°, 19.6°, 22.2°, 25.7°, 26.36°, and 27.67° are typical characteristic diffraction peaks of MOR molecular sieves. Meanwhile, the XRD pattern shows a stable baseline and no impurity peaks, indicating the synthesis of a well-crystallized MOR molecular sieve. Its SEM characterization is shown in the appendix. Figure 6 .

[0116] ZSM-5 molecular sieve Z-2, Beta molecular sieve B-2, MOR molecular sieve S-2, and alumina were thoroughly mixed at a mass ratio of 4:2:1:3. Catalyst C-2 was then obtained according to the catalyst preparation method described in Example 1.

[0117] Example 3

[0118] 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 - The molecular sieve consisted of 30.504 g of a 25% (w / w) aqueous solution, 0.45 g of NaOH, and 0.814 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.0125:0.25:0.075:14:1. The synthesis temperature was 180℃, and the synthesis time was 100 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0119] The obtained ZSM-5 molecular sieve, designated Z-3, has a silica-to-alumina ratio of 80 and an average grain size of 0.79 μm. The XRD diffraction pattern is attached. Figure 1 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5. These peaks represent the (011), (020), (332), and (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline with no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM characterization is shown in the appendix. Figure 4 .

[0120] 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 - 39.46 g of (35% by mass aqueous solution) and 0.375 g of NaOH were added. The amount of water added was 41.85 g. The molar ratio of the ingredients was Al2O3:template:NaOH:H2O:SiO2 = 0.0125:0.375:0.0375:15:1. The synthesis temperature was 155℃, and the synthesis time was 105 hours. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried.

[0121] The obtained Beta molecular sieve, designated B-3, has a silica-to-alumina ratio of 80 and an average grain size of 100 nm. The XRD diffraction pattern is attached. Figure 2It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 5 .

[0122] 30g of silicon source (solid silica sol), 2.3g of aluminum source (SB powder), 4g of NaOH, and 89.4g of water were added to a 200mL reactor. The molar ratio of the added substances was Al₂O₃:NaOH:H₂O:SiO₂ = 0.033:0.2:10:1. The synthesis temperature was 175℃, and the synthesis time was 96 hours, using a dynamic synthesis method to synthesize the molecular sieve. The molecular sieve was then washed and dried.

[0123] The obtained MOR molecular sieve, designated S-3, has a silica-to-alumina ratio of 30 and an average grain size of 3.0 μm. The XRD diffraction pattern is attached. Figure 3 The diffraction peaks appearing at 2θ = 6.5°, 8.6°, 9.78°, 13.44°, 15.36°, 19.6°, 22.2°, 25.7°, 26.36°, and 27.67° are typical characteristic diffraction peaks of MOR molecular sieves. Meanwhile, the XRD pattern shows a stable baseline and no impurity peaks, indicating the synthesis of a well-crystallized MOR molecular sieve. Its SEM characterization is shown in the appendix. Figure 6 .

[0124] ZSM-5 molecular sieve Z-3, Beta molecular sieve B-3, MOR molecular sieve S-3, and alumina were thoroughly mixed at a mass ratio of 3:2:2:3. Catalyst C-3 was then obtained according to the catalyst preparation method described in Example 1.

[0125] Example 4

[0126] Catalyst C-4 was obtained according to the catalyst preparation method in Example 1, except that the mass ratio of ZSM-5 molecular sieve Z-1, Beta molecular sieve B-1, MOR molecular sieve S-1 to alumina was 3:1:3:3.

[0127] Example 5

[0128] Catalyst C-5 was obtained according to the catalyst preparation method in Example 2, except that the mass ratio of ZSM-5 molecular sieve Z-2, Beta molecular sieve B-2, MOR molecular sieve S-2 to alumina was 2:3:2:3.

[0129] Example 6

[0130] Catalyst C-6 was obtained according to the catalyst preparation method in Example 3, except that the mass ratio of ZSM-5 molecular sieve Z-3, Beta molecular sieve B-3, MOR molecular sieve S-3 to alumina was 1:3:3:3.

[0131] Comparative Example 1

[0132] Catalyst D-1 was obtained according to the catalyst preparation method in Example 1, except that ZSM-5 molecular sieve and MOR molecular sieve were not added to the catalyst, and the mass ratio of Beta molecular sieve B-1 to alumina was 7:3.

[0133] Comparative Example 2

[0134] Catalyst D-2 was obtained according to the catalyst preparation method in Example 2, except that Beta molecular sieve and MOR molecular sieve were not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-2 to alumina was 7:3.

[0135] Comparative Example 3

[0136] Catalyst D-3 was obtained according to the catalyst preparation method in Example 3, except that Beta molecular sieve and ZSM-5 molecular sieve were not added to the catalyst, and the mass ratio of MOR molecular sieve S-3 to alumina was 7:3.

[0137] Comparative Example 4

[0138] Catalyst D-4 was obtained according to the catalyst preparation methods in Examples 1 and 2, except that ZSM-5 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-2, MOR molecular sieve S-1 and alumina was 3:4:3.

[0139] Comparative Example 5

[0140] Catalyst D-5 was obtained according to the catalyst preparation methods in Examples 2 and 3, except that Beta molecular sieve was not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-3, MOR molecular sieve S-2 and alumina was 2:5:3.

[0141] Comparative Example 6

[0142] Catalyst D-6 was obtained according to the catalyst preparation methods in Examples 1 and 3, except that MOR molecular sieve was not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-3, Beta molecular sieve B-1 and alumina was 1:6:3.

[0143] Test Implementation Examples

[0144] 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: 240°C, 2 MPa, and a feed mass hourly space velocity (MHSV) of 2 h⁻¹. -1 .

[0145] Table 1 Raw Material Composition

[0146] <![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

[0147] Catalyst performance was evaluated using the following calculation method:

[0148] Isomerization activity indicators:

[0149] Xylene yield:

[0150] The catalysts used in each embodiment and comparative example and the reaction results are shown in Tables 2 and 3.

[0151] Table 2 Catalysts and Reaction Performance in Examples

[0152]

[0153]

[0154] Table 3 Comparative Catalysts and Reaction Performance

[0155]

[0156] As shown in Tables 2 and 3, the catalysts prepared by the methods of Examples 1 to 6 of the present 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 the present 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.

[0157] 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 liquid-phase xylene isomerization catalyst, characterized in that, It comprises 10–80% H-type molecular sieve and 20–90% binder, based on the mass of the liquid-phase xylene isomerization catalyst; The H-type molecular sieve comprises the following components in the following proportions based on the total mass of the H-type molecular sieve: ZSM-5 molecular sieve 5-90% Beta molecular sieve 5-90% MOR molecular sieves have a purity of 5-90%.

2. A method for preparing the liquid-phase xylene isomerization catalyst of claim 1, characterized in that, Includes the following steps: (1) Provide alkali metal ion type ZSM-5 molecular sieve; (2) Provide alkali metal ion type Beta molecular sieves; (3) Provide alkali metal ion-type MOR molecular sieves; (4) After mixing the alkali metal ion type ZSM-5 molecular sieve, alkali metal ion type Beta molecular sieve and alkali metal ion type MOR molecular sieve with the binder, add acid solution for kneading, molding and first calcination, then contact with ammonium salt solution for ion exchange and second calcination to obtain the liquid phase xylene isomerization catalyst.

3. The method according to claim 2, characterized in that, The preparation method of the alkali metal ion type ZSM-5 molecular sieve in step (1) includes: The first silicon source, the first aluminum source, the first template agent, the first alkali and water are mixed and subjected to the first crystallization synthesis to obtain the alkali metal ion type ZSM-5 molecular sieve; The preparation method of the alkali metal ion type Beta molecular sieve in step (2) includes: The second silicon source, the second aluminum source, the second template agent, the second alkali, and water are mixed and subjected to a second crystallization synthesis to obtain the alkali metal ion type Beta molecular sieve. The preparation method of the alkali metal ion type MOR molecular sieve in step (3) includes: The alkali metal ion type MOR molecular sieve is obtained by mixing the third silicon source, the third aluminum source, the third alkali, and water and then performing a third crystallization synthesis.

4. The method according to claim 3, characterized in that, The molar ratio of the first silicon source (calculated as SiO2), the first aluminum source (calculated as Al2O3), the first template agent, the first alkali, and water is 1:(0.005~0.05):(0.05~1):(0.02~1):(10~60); The first template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R1)4. + X - R1 is selected from alkyl groups having 1 to 4 carbon atoms, preferably propyl, X - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions; The first crystallization synthesis is carried out at 140–190°C and under autogenous pressure for 40–140 h, preferably at 175–185°C and under autogenous pressure for 96–120 h.

5. The method according to claim 3, characterized in that, The molar ratio of the second silicon source (calculated as SiO2), the second aluminum source (calculated as Al2O3), the second template agent, the second alkali, and water is 1:(0.005~0.05):(0.05~1.5):(0.02~0.5):(10~60); The second template agent is selected from quaternary ammonium bases and / or quaternary ammonium salts, with the general formula N(R2)4. + Y - R2 is selected from alkyl groups having 1 to 4 carbon atoms, preferably ethyl, Y - Selected from hydroxide ions, chloride ions, or bromide ions, preferably hydroxide ions; The second crystallization synthesis is carried out at 120–180°C and under autogenous pressure for 60–140 h, preferably at 135–175°C and under autogenous pressure for 96–120 h.

6. The method according to claim 3, characterized in that, The molar ratio of the third silicon source (calculated as SiO2), the third aluminum source (calculated as Al2O3), the third alkali, and water is 1:(0.005~0.05):(0.1~1.5):(10~60); The third crystallization synthesis was carried out at 110–200 °C and under autogenous pressure for 40–140 h.

7. The method according to claim 6, characterized in that, The third crystallization process can be either a single-stage or two-stage crystallization, wherein the temperature of the single-stage crystallization is 170–190°C and the time is 48–96 h. The two-stage crystallization includes a first-stage crystallization and a second-stage crystallization. The temperature of the first-stage crystallization is 110–130°C and the time is 10–24 h. The temperature of the second-stage crystallization is 150–200°C and the time is 36–96 h.

8. The method according to claim 3, characterized in that, The first silicon source, the second silicon source, and the third silicon source are each independently selected from liquid silica sol and / 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 100-500 μm, preferably 200-400 μm.

9. The method according to claim 2, characterized in that, The crystal size of the alkali metal ion type ZSM-5 molecular sieve is 0.05-10 μm, preferably 0.5-5 μm; the crystal size of the alkali metal ion type Beta molecular sieve is 30-600 nm, preferably 50-300 nm; the crystal size of the alkali metal ion type MOR molecular sieve is 0.5-10 μm, preferably 0.5-5 μm.

10. A liquid-phase xylene isomerization reaction, comprising contacting a feedstock containing alkyl aromatics with a liquid-phase xylene isomerization catalyst under a reaction pressure that maintains a liquid state to carry out the isomerization reaction, wherein the liquid-phase xylene isomerization catalyst is the liquid-phase xylene isomerization catalyst of claim 1 or is prepared by any one of claims 2 to 9; Preferably, the isomerization reaction is carried out at 240–310°C and a mass hourly space velocity (WHSV) of 1–10 h⁻¹. -1 The following will proceed.

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