Catalyst for preparing BTX from polycyclic aromatic hydrocarbon as well as preparation method and application of catalyst

Abstract

The invention discloses a BTX catalyst prepared from polycyclic aromatic hydrocarbon as well as a preparation method and application of the BTX catalyst. The catalyst comprises a carrier and an active component, wherein the carrier comprises a molecular sieve A and a molecular sieve B, the molecular sieve A is selected from at least one of mordenite, a Beta molecular sieve and a Y molecular sieve, and the molecular sieve B is a ZSM-5 molecular sieve; the active component comprises a rare earth metal M1 and a transition metal M2. The catalyst provided by the invention is used in a reaction for preparing BTX from polycyclic aromatic hydrocarbon, and has the advantages of good conversion activity of polycyclic aromatic hydrocarbon, high selectivity of a target product and the like.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the production of BTX from polycyclic aromatic hydrocarbons, its preparation method, and its application. Background Technology

[0002] In petroleum refining and downstream chemical production, polycyclic aromatic hydrocarbons (PAHs) are common heavy byproducts. Among them, naphthalene derivatives, a type of bicyclic aromatic hydrocarbon, are present in high concentrations, making them a key focus of research. Researchers believe that partially hydrogenating and saturating naphthalene derivatives, followed by selective ring-opening to generate high-value-added light aromatics such as benzene, toluene, and xylene (BTX), is an effective solution. Currently, Chinese research institutions, such as the LTAG technology at the Sinopec Research Institute of Petroleum Processing and the FD2G technology at the Dalian Petrochemical Research Institute, employ partial hydrogenation saturation followed by selective ring-opening reaction pathways, and these technologies have already been industrially applied in some refineries.

[0003] While hydrogenation saturation of naphthalene derivatives is relatively easy to achieve, controlling the selective ring-opening of cycloalkanes and aromatics in the hydrogenation products is more challenging. Tetrahydronaphthalene is a product of selective hydrogenation saturation of naphthalene, and researchers have used it as a model to investigate its selective ring-opening reaction behavior. Metal bifunctional catalysts are the primary choice for studying the hydrocracking reaction of tetrahydronaphthalene. The acidic centers on the catalyst possess catalytic dehydrogenation, cracking, isomerization, and dealkylation properties, while the active metal sites primarily promote hydrogenation, hydrocracking, and isomerization reactions. Excessive acidic or metallic sites are detrimental to the selective ring-opening of cycloalkanes and aromatics. Achieving a good balance between metal and acid functions is essential for achieving optimal catalyst performance. Commonly used molecular sieves in research include MOR, Beta, USY, and ZSM-5 zeolite molecular sieves, while the supported metals are typically transition metals Ni, Mo, and W, as well as noble metals Pt and Ir.

[0004] CN1169915C discloses a method for preparing a rare-earth-containing hydrocracking catalyst. The method involves supporting rare-earth metals on an alumina precursor or amorphous silica-alumina, mixing them with molecular sieves and a colloidal solvent to prepare the catalyst, and finally loading the hydrogenation-active metal onto a shaped catalyst support. This is an early method for preparing rare-earth-containing hydrocracking catalysts, and the operation is relatively simple and convenient.

[0005] US5464527A discloses a method for preparing a rare-earth-containing hydrocracking catalyst. The method involves first exfoliating a Y-type molecular sieve with ammonium, calcining it to prepare an H-type molecular sieve, then exchanging it with a rare-earth metal salt solution to prepare a rare-earth Y-type molecular sieve, and using alumina as a binder to prepare the catalyst. The catalyst obtained by this method can convert heavy distillate oils into light hydrocarbon compounds, but for the tetrahydronaphthalene hydrocracking reaction, the selectivity for the target product BTX is low.

[0006] CN104588081A discloses a rare-earth-containing hydrocracking catalyst, which consists of hydrogenation-active components of Ni, W, Si, and Al, rare-earth metals, and Y-type molecular sieves. The catalyst is prepared by a co-precipitation method to produce a nickel-aluminum mixed precipitate, a co-current precipitation method to produce a tungsten, silicon, and aluminum mixed precipitate, followed by hydrothermal treatment of the two precipitates, addition of a molecular sieve suspension, and finally soaking in a rare-earth organic mixture to obtain the hydrocracking catalyst. This co-precipitation method allows for sufficient contact between the rare-earth metals and the hydrogenation-active metals, resulting in a good balance between the hydrogenation and cracking activities. However, the preparation method is relatively complex and is suitable for heavy feedstocks such as vacuum gas oil, deasphalted oil, and catalytic cracking gas oil. Summary of the Invention

[0007] This invention addresses the problems of low conversion rate of polycyclic aromatic hydrocarbons (PAHs) and low selectivity of the target product BTX in the prior art reaction for the production of BTX from PAHs. This invention provides a catalyst for the production of BTX from PAHs, its preparation method, and its application. The catalyst provided by this invention exhibits advantages such as high conversion activity of PAHs and high selectivity of the target product in the reaction for the production of BTX from PAHs.

[0008] The first aspect of this invention provides a catalyst for the production of BTX from polycyclic aromatic hydrocarbons, comprising a support and an active component;

[0009] The carrier includes molecular sieve A and molecular sieve B; molecular sieve A is selected from at least one of mordenite, Beta molecular sieve, and Y molecular sieve; molecular sieve B is ZSM-5 molecular sieve.

[0010] The active components include rare earth metal M1 and transition metal M2.

[0011] In the above technical solution, the rare earth metal M1 is one or more of lanthanum, cerium, and praseodymium; the transition metal M2 is at least one selected from nickel, molybdenum, cobalt, copper, tungsten, iron, zirconium, chromium, vanadium, or zinc, preferably at least one of nickel, molybdenum, cobalt, chromium, and copper.

[0012] In the above technical solution, the distribution of the rare earth metal M1 and the transition metal M2 on the carrier is denoted as M2@M1-molecular sieve A, wherein the rare earth metal M1 is distributed on the framework of molecular sieve A, and the transition metal M2 is loaded on the surface of M1-molecular sieve A.

[0013] In the above technical solution, the weights of molecular sieve A and molecular sieve B, calculated on a dry basis, are 10:90 to 90:10, preferably 40:60 to 60:40.

[0014] In the above technical solution, the molar ratio of SiO2 / Al2O3 in the molecular sieve A is 10 to 100, and preferably, the molar ratio of SiO2 / Al2O3 in the molecular sieve A is 15 to 40.

[0015] In the above technical solution, the molar ratio of SiO2 / Al2O3 in the molecular sieve B is 10 to 100, and preferably, the molar ratio of SiO2 / Al2O3 in the molecular sieve B is 15 to 40.

[0016] In the above technical solution, the average pore size of the molecular sieve A is 1-5 nm, preferably 2-3 nm.

[0017] In the above technical solution, the acid content on the outer surface of the molecular sieve B accounts for 5-40% of the total acid content, preferably 15-30% of the total acid content.

[0018] In the above technical solution, the external specific surface area of ​​the molecular sieve B accounts for 5-30% of the total specific surface area, preferably 10-25%.

[0019] In the above technical solution, the rare earth metal M1 in the catalyst has a weight content of 0.01-10% (based on metal content), preferably 0.01-5%.

[0020] In the above technical solution, the transition metal M2 in the catalyst has a weight content of 0.01-20% (based on metal content), preferably 0.01-5%.

[0021] The second aspect of the present invention provides a method for preparing the above-mentioned polycyclic aromatic hydrocarbon to BTX catalyst, comprising the steps of first preparing M2@M1-molecular sieve A, and then mixing it with molecular sieve B to form a catalyst.

[0022] In the above technical solution, preferably, the preparation method of M2@M1-molecular sieve A includes: first introducing rare earth metal M1 into molecular sieve A through ion exchange to obtain an intermediate, and then impregnating it with a loaded transition metal M2 to obtain M2@M1-molecular sieve.

[0023] In the above technical solution, the molecular sieve A is selected from at least one of mordenite, Beta molecular sieve, and Y molecular sieve.

[0024] In the above technical solution, the average pore size of the molecular sieve A is 1-5 nm, preferably 2-3 nm.

[0025] In the above technical solution, the molar ratio of SiO2 / Al2O3 in the molecular sieve A is 10 to 100, and preferably, the molar ratio of SiO2 / Al2O3 in the molecular sieve A is 15 to 40.

[0026] In the above technical solution, the rare earth metal M1 is introduced by using a rare earth metal salt, which is selected from one or more metal salts of lanthanum, cerium, and praseodymium.

[0027] In the above technical solution, the transition metal M2 is introduced by means of a transition metal salt solution, wherein the transition metal salt solution can be a metal nitrate, a metal sulfate or other metal salt solution that is easily soluble in water.

[0028] In the above technical solution, the ion exchange specifically involves adding molecular sieve A to a rare earth metal M1 salt solution, heating and stirring, and then filtering to obtain a filter cake; then adding the filter cake to water, heating and stirring again, and then filtering and drying to obtain an intermediate.

[0029] In the above technical solution, the impregnation is performed by adding the obtained intermediate to a transition metal M2 salt solution for impregnation;

[0030] In the above technical solution, during ion exchange, the heating temperature is 50-120℃ and the time is 0.5-10 hours, preferably 1-5 hours.

[0031] In the above technical solution, during ion exchange, the secondary heating temperature is 50-120℃ and the time is 0.5-10 hours, preferably 1-4 hours.

[0032] In the above technical solution, during ion exchange, the drying operation is carried out under an atmosphere of air, nitrogen, or inert gas, with a processing temperature of 60–150°C and a processing time of 1–24 hours.

[0033] In the above technical solution, during ion exchange, the mass ratio of rare earth metal M1 salt solution to molecular sieve A is 1 to 10:1, preferably 3 to 6:1.

[0034] In the above technical solution, during impregnation, the mass ratio of transition metal M2 salt solution to molecular sieve A is 0.1 to 10:1, preferably 0.5 to 3:1.

[0035] In the above technical solution, the impregnation temperature is preferably room temperature, i.e., 15-35℃, and the impregnation time is 0-12 hours. After the impregnation treatment, it can be left overnight and then dried. The drying operation is carried out as follows: the impregnated powder left overnight is placed in a heating device and processed in an atmosphere of air, nitrogen, or inert gas at a temperature of 0-60℃ for 1-3 hours. Then the temperature is raised to 70-100℃ and the processing time is 1-3 hours to obtain M2@M1-molecular sieve A.

[0036] In the above technical solution, the molecular sieve B is a ZSM-5 molecular sieve.

[0037] In the above technical solution, the molar ratio of SiO2 / Al2O3 in the molecular sieve B is 10 to 100, and preferably, the molar ratio of SiO2 / Al2O3 in the molecular sieve B is 15 to 40.

[0038] In the above technical solution, the weights of molecular sieve A and molecular sieve B, calculated on a dry basis, are 10:90 to 90:10, preferably 60:40 to 40:60.

[0039] In the above technical solution, the mixing and molding method of M2@M1-molecular sieve A and molecular sieve B can adopt conventional kneading molding method in the art. For example, the binder is kneaded with M2@M1-molecular sieve A and molecular sieve B respectively, and then mixed to obtain the catalyst; or, the binder is kneaded with M2@M1-molecular sieve A and molecular sieve B to obtain the catalyst.

[0040] In the above technical solution, the binder is preferably at least one of boehmite or alumina sol.

[0041] In the above technical solution, after kneading and shaping, conventional drying and calcination processes are performed. The drying conditions are: temperature 100–150℃, time 0.5–2 hours. The calcination process takes 1–5 hours and is carried out at a temperature of 400–550℃.

[0042] A third aspect of the present invention provides the application of the above-mentioned catalyst in the reaction of polycyclic aromatic hydrocarbons to BTX.

[0043] In the above technical solution, in the presence of a catalyst and under hydrogen-exposed conditions, polycyclic aromatic hydrocarbons are reacted to produce BTX products.

[0044] In the above technical solution, the catalyst needs to be reduced and activated before the reaction.

[0045] In the above technical solution, a reducing gas, preferably hydrogen, is used in the reduction activation treatment. The reduction temperature of the reduction activation treatment is 400–450°C, and the reduction time is 1–4 hours.

[0046] In the above technical solution, the polycyclic aromatic hydrocarbon is preferably at least one of tetrahydronaphthalene, indane, naphthalene, and anthraquinone.

[0047] In the above technical solution, the reaction conditions include: a reaction temperature of 200–500°C, a pressure of 0.1–4 MPa, and a feed mass hourly space velocity of 0.1–10 h⁻¹. -1The hydrogen / polycyclic aromatic hydrocarbon molar ratio is (0.1-10):1; preferably, the hydrogen-exposed conditions include: 300-400°C, pressure of 1-3 MPa, feed mass hourly space velocity of 1-5 h⁻¹, and hydrogen / polycyclic aromatic hydrocarbon molar ratio of (1-5):1.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] The production of BTX from polycyclic aromatic hydrocarbons (PAHs) involves hydrocracking, isomerization, alkyl transfer, and dehydrogenation reactions. The products include not only BTX but also isomerization products, alkyl transfer products, and dehydrogenation products. For example, when tetrahydronaphthalene is used as the feedstock, the products often include the isomerization product methylindane, the alkyl transfer product dimethyltetrahydronaphthalene, and the dehydrogenation product naphthalene. Using molecular sieve catalysts with a single structure is no longer sufficient to meet the requirement of high selectivity for the target product.

[0050] The catalyst provided by this invention contains two different types of molecular sieves, namely, the support of this invention includes molecular sieve A and molecular sieve B, with transition metals and rare earth metals as active components, particularly the introduction of rare earth metals into the framework of molecular sieve A to replace the H in the aluminum hydroxyl groups. + The process involves adjusting the acidity of the molecular sieve, and secondly, the coordination of rare earth metals with framework oxygen atoms to improve the stability of the molecular sieve. Transition metal components are loaded onto the surface of M1-molecular sieve A, primarily involving aromatic ring hydrogenation and hydrogen spillover to provide hydrogen to acidic centers, resulting in outstanding polycyclic aromatic hydrocarbon (PAH) conversion performance. This also reduces the formation of naphthalene derivatives as byproducts in PAH dehydrogenation reactions, effectively regulating product distribution and improving the selectivity of the target product. In PAH reaction processes involving hydrocracking, isomerization, alkyl transfer reactions, and dehydrogenation reactions, where the products are complex, this method better meets the selectivity requirements compared to using single-structure molecular sieve catalysts or other types of catalysts.

[0051] The preparation method provided by this invention is simple. Rare earth metals and transition metals are introduced into molecular sieve A, wherein rare earth metals are introduced into the molecular sieve framework through ion exchange, and transition metals are introduced to the surface of the molecular sieve through impregnation. Then, it is mixed with molecular sieve B to form the catalyst, which can be used in the reaction of polycyclic aromatic hydrocarbons to BTX. It has the advantages of good conversion activity of polycyclic aromatic hydrocarbons and high selectivity of target products. Detailed Implementation

[0052] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of this invention are still within the scope of protection of the present invention.

[0053] In this invention, the polycyclic aromatic hydrocarbon is selected from at least one of the following: fused-ring aromatic hydrocarbons having two or more benzene rings, aromatic hydrocarbons having at least one benzene ring and at least one hydrogenated benzene ring, and aromatic hydrocarbons having at least one benzene ring and at least one cycloalkane ring.

[0054] In this invention, the acid content on the outer surface of the molecular sieve is determined by tert-butylamine titration, the total acid content is determined by n-butylamine titration, and the acid content inside the molecular sieve channels is calculated using the difference between the two methods. The tests were performed on a ZDJ-5 potential titrator from Shanghai Leici Instruments Co., Ltd. Before testing, the sample was ground into powder, activated at high temperature, and dehydrated. The powder was dispersed in an acetonitrile solution and stirred until the potential stabilized. An organic amine solution was gradually added dropwise, and the potential change was recorded simultaneously. Titration continued until the potential remained essentially constant. The number of acidic sites added was calculated based on the amount of organic amine consumed.

[0055] In this invention, specific surface area includes external specific surface area and internal specific surface area. The specific surface area, external specific surface area, and pore structure in the embodiments and comparative examples of this invention were determined using nitrogen adsorption-desorption method. The tests were performed using an ASAP 2020 automated physical adsorption instrument from Micromeritics Instruments, Inc. High-purity nitrogen was used as the adsorbate, and the measurements were conducted at -196°C. A vacuum pretreatment at 350°C for 4 hours was required before the test. Specific surface area and external surface area were calculated using the BET formula, and pore structure analysis was performed using the BJH method.

[0056] In this invention, the silicon-to-aluminum ratio and related element content of the molecular sieve and catalyst are determined using an Agilent 725ES inductively coupled plasma optical emission spectrometer (ICP-OES). The samples are first calcined into the hydrogen form before testing.

[0057] In the embodiments and comparative examples of this invention, tetrahydronaphthalene was used as a reaction model compound for polycyclic aromatic hydrocarbons. The reaction performance of tetrahydronaphthalene to BTX was calculated by mass according to the following formula:

[0058]

[0059]

[0060] Among them, S (B+T+X) This indicates the selectivity of BTX.

[0061] Example 1

[0062] 20g of lanthanum nitrate hexahydrate was dissolved in 1000ml of deionized water to prepare a lanthanum nitrate solution. 200g of mordenite molecular sieve (dry basis) was added to the lanthanum nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain an intermediate.

[0063] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and impregnated at room temperature for 3 hours. The mixture was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain Mo@La-mordenite zeolite molecular sieve.

[0064] Take 30g of Mo@La-mordenite molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0065] Both the mordenite zeolite molecular sieve and the ZSM-5 molecular sieve were purchased externally. The average pore size of the mordenite zeolite molecular sieve is 2.36 nm. The SiO2 / Al2O3 molar ratio of the mordenite zeolite molecular sieve is 25. The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 32. The ZSM-5 molecular sieve has an outer surface acid content of 105 μmol tert-butylamine / g, a total acid content of 678 μmol n-butylamine / g, and an inner pore acid content of 573 μmol tert-butylamine / g, with the outer surface acid content accounting for 15.49% of the total acid content. The BET specific surface area of ​​the ZSM-5 molecular sieve is 354 m². 2 / g, with an external specific surface area of ​​57m² 2 / g, the external specific surface area accounts for 16.10% of the total specific surface area.

[0066] The catalyst prepared contained 0.63% lanthanum (a rare earth metal) and 1.59% molybdenum (a transition metal) by weight.

[0067] Example 2

[0068] 20g of lanthanum nitrate hexahydrate was dissolved in 800ml of deionized water to prepare a lanthanum nitrate solution. 200g of Beta molecular sieve (dry basis) was added to the lanthanum nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain an intermediate.

[0069] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and soaked at room temperature for 3 hours. The sample was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain the Mo@La-Beta molecular sieve.

[0070] Take 30g of Mo@La-Beta molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0071] Both Beta and ZSM-5 molecular sieves were purchased externally. The average pore size of the Beta molecular sieve was 2.63 nm. The SiO2 / Al2O3 molar ratio of the Beta molecular sieve was 24. The ZSM-5 molecular sieve used was the same as in Example 1.

[0072] The catalyst prepared contained 0.69% lanthanum (a rare earth metal) and 1.62% molybdenum (a transition metal) by weight.

[0073] Example 3

[0074] 20g of lanthanum nitrate hexahydrate was dissolved in 900ml of deionized water to prepare a lanthanum nitrate solution. 200g of Y molecular sieve (dry basis) was added to the lanthanum nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain an intermediate.

[0075] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and soaked at room temperature for 3 hours. The sample was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain the Mo@La-Y molecular sieve.

[0076] Take 30g of Mo@La-Y molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0077] Both Y-type and ZSM-5 molecular sieves were purchased externally. The average pore size of the Y-type molecular sieve is 2.75 nm. The SiO2 / Al2O3 molar ratio of the Y-type molecular sieve is 22. The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 32. The ZSM-5 molecular sieve has an external surface acid content of 108 μmol tert-butylamine / g, a total acid content of 690 μmol n-butylamine / g, and an internal acid content of 582 μmol tert-butylamine / g, with the external surface acid content accounting for 15.65% of the total acid content. The BET specific surface area of ​​the ZSM-5 molecular sieve is 350 m² / g. 2 / g, with an external specific surface area of ​​62m² 2 / g, the external specific surface area accounts for 17.71% of the total specific surface area.

[0078] The catalyst prepared contained 0.87% lanthanum (a rare earth metal) and 1.56% molybdenum (a transition metal) by weight.

[0079] Example 4

[0080] 24g of cerium nitrate hexahydrate was dissolved in 1000ml of deionized water to prepare a cerium nitrate solution. 200g of mordenite molecular sieve (dry weight) was added to the cerium nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain an intermediate.

[0081] 26.5 g of nickel nitrate hexahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the nickel nitrate solution, and the mixture was impregnated and stirred at room temperature for 3 hours. The sample was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain Ni@Ce-mordenite zeolite molecular sieve.

[0082] Take 60g of Ni@Ce-mordenite molecular sieve, mix it evenly with 40g of pseudoboehmite (both converted to dry basis) and 3g of guar gum powder, knead it, and extrude it into strips. After drying in an oven at 120℃ for 0.5 hours, place it in a muffle furnace, heat it to 550℃ for 2 hours, and calcine it for 3 hours to obtain catalyst A precursor.

[0083] Take 60g of ZSM-5 molecular sieve and 40g of pseudoboehmite (both converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain catalyst B precursor.

[0084] Catalyst A precursor and catalyst B precursor were mixed in a 1:1 ratio to obtain the catalyst of this embodiment.

[0085] Both the mordenite zeolite molecular sieve and the ZSM-5 molecular sieve were purchased externally. The average pore size of the mordenite zeolite molecular sieve was 2.36 nm. The SiO2 / Al2O3 molar ratio of the mordenite zeolite molecular sieve was 25. The ZSM-5 used was the same as in Example 1.

[0086] The catalyst prepared contains 0.75% cerium (based on metal weight) and 0.93% nickel (based on metal weight).

[0087] Comparative Example 1

[0088] 20g of lanthanum nitrate hexahydrate was dissolved in 1000ml of deionized water to prepare a lanthanum nitrate solution. 200g of mordenite molecular sieve (dry weight) was added to the lanthanum nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain La-mordenite molecular sieve.

[0089] Take 30g of La-mordenite molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0090] The properties of the mordenite molecular sieve and the ZSM-5 molecular sieve are the same as in Example 1.

[0091] The catalyst prepared contained 0.66% lanthanum by mass.

[0092] Comparative Example 2

[0093] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of mordenite molecular sieve (dry weight) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and impregnated at room temperature for 3 hours. The sample was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain Mo@mordenite molecular sieve.

[0094] Take 30g of Mo@mordenite molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0095] The properties of the mordenite molecular sieve and the ZSM-5 molecular sieve are the same as in Example 1.

[0096] The catalyst prepared contained 1.72% molybdenum by mass.

[0097] Comparative Example 3

[0098] 20g of lanthanum nitrate hexahydrate was dissolved in 1000ml of deionized water to prepare a lanthanum nitrate solution. 200g of mordenite molecular sieve (dry basis) was added to the lanthanum nitrate solution. The solution was heated and stirred to 90℃ and held at this temperature for 4 hours. The mixture was then filtered to obtain a filter cake. The filter cake was placed in 800ml of deionized water, heated and stirred to 90℃, and held at this temperature for 1 hour. The mixture was then filtered again, and the filter cake was dried in an oven at 120℃ to obtain an intermediate.

[0099] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and impregnated at room temperature for 3 hours. The mixture was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain Mo@La-mordenite zeolite molecular sieve.

[0100] Take 30g of Mo@La-mordenite molecular sieve, mix 30g of mordenite molecular sieve with 40g of pseudoboehmite (both converted to dry basis) and 3g of guar gum powder evenly, knead, and extrude into strips. After drying in an oven at 120℃ for 0.5 hours, place in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0101] The mordenite molecular sieve was purchased externally. The properties of the mordenite molecular sieve are the same as in Example 1.

[0102] The catalyst prepared contained 0.63% lanthanum (a rare earth metal) and 1.59% molybdenum (a transition metal) by weight.

[0103] Comparative Example 4

[0104] 20g of lanthanum nitrate hexahydrate was dissolved in 200ml of deionized water to prepare a lanthanum nitrate solution. 200g of mordenite molecular sieve (dry weight) was added to the lanthanum nitrate solution, and the mixture was stirred and soaked at room temperature for 3 hours. The sample was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50℃ oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80℃ and kept at that temperature for 3 hours. Finally, the sample was placed in a 120℃ oven and kept at that temperature for 4 hours to obtain the intermediate.

[0105] 17.68 g of ammonium tetramolybdate heptahydrate was dissolved in 180 ml of deionized water to obtain an ammonium molybdate aqueous solution. 160 g of the intermediate (dry basis) was added to the ammonium molybdate aqueous solution, and the mixture was stirred and impregnated at room temperature for 3 hours. The mixture was then removed and placed in a tray to air dry overnight. The sample in the tray was placed in a 50°C oven and kept at that temperature for 2 hours. The oven temperature was then increased to 80°C and kept at that temperature for 3 hours to obtain Mo-La@mordenite zeolite molecular sieve.

[0106] Take 30g of Mo-La@mordenite molecular sieve, 30g of ZSM-5 molecular sieve, 40g of pseudoboehmite (all converted to dry basis), and 3g of guar gum powder, mix them evenly, knead them, and extrude them into strips. After drying in an oven at 120℃ for 0.5 hours, place them in a muffle furnace, heat to 550℃ for 2 hours, and calcine for 3 hours to obtain the catalyst.

[0107] The properties of the mordenite molecular sieve and ZSM-5 molecular sieve are the same as in Example 1.

[0108] The catalyst prepared contained 0.68% lanthanum (a rare earth metal) by weight and 1.62% molybdenum (a transition metal) by weight.

[0109] Catalyst evaluation

[0110] The catalysts of each embodiment and comparative example were reduced at 450°C under hydrogen conditions for 3 hours before being evaluated.

[0111] The evaluation conditions are as follows: reaction temperature 375℃, pressure 3MPa, and feed mass hourly space velocity (MHSV) 3 h⁻¹. -1 The hydrogen / tetrahydronaphthalene molar ratio is 3:1.

[0112] Under the above conditions, the reaction performance of each catalyst is shown in Table 1.

[0113] Table 1

[0114] Catalyst number Tetrahydronaphthalene conversion rate (wt%) BTX selectivity / wt% Example 1 58.63 46.54 Example 2 59.12 47.86 Example 3 59.89 48.13 Example 4 59.45 47.56 Comparative Example 1 46.38 43.22 Comparative Example 2 45.79 42.35 Comparative Example 3 50.49 35.65 Comparative Example 4 49.89 45.23

Claims

1. A catalyst for the production of BTX from polycyclic aromatic hydrocarbons, characterized in that, The catalyst includes a support and an active component; The carrier includes molecular sieve A and molecular sieve B; molecular sieve A is selected from at least one of mordenite, Beta molecular sieve, and Y molecular sieve; molecular sieve B is ZSM-5 molecular sieve. The active components include rare earth metal M1 and transition metal M2.

2. The catalyst according to claim 1, characterized in that, The rare earth metal M1 is one or more of lanthanum, cerium, and praseodymium; And / or, the transition metal M2 is at least one of nickel, molybdenum, cobalt, copper, tungsten, iron, zirconium, chromium, vanadium or zinc; And / or, the distribution of the rare earth metal M1 and the transition metal M2 on the support is denoted as M2@M1-molecular sieve A, wherein the rare earth metal M1 is distributed on the framework of molecular sieve A, and the transition metal M2 is loaded on the surface of M1-molecular sieve A.

3. The catalyst according to claim 1, characterized in that, The weights of molecular sieve A and molecular sieve B, calculated on a dry basis, are 10:90 to 90:

10. And / or, in the catalyst, the rare earth metal M1 has a weight content of 0.01 to 10% based on metal content. And / or, in the catalyst, the weight content of transition metal M2, calculated as metal, is 0.01 to 20%.

4. The catalyst according to claim 1, characterized in that, The molar ratio of SiO2 / Al2O3 in the molecular sieve A is 10 to 100. And / or, the average pore size of the molecular sieve A is 1 to 5 nm.

5. The catalyst according to claim 1, characterized in that, The molar ratio of SiO2 / Al2O3 in the molecular sieve B is 10 to 100. And / or, in the molecular sieve B, the acid content on the outer surface accounts for 5-40% of the total acid content; And / or, in the molecular sieve B, the external specific surface area accounts for 5% to 30% of the total specific surface area.

6. A method for preparing the catalyst according to any one of claims 1-5, comprising the steps of first preparing M2@M1-molecular sieve A, and then mixing it with molecular sieve B to form a catalyst.

7. The preparation method according to claim 6, characterized in that, The preparation method of M2@M1-molecular sieve A includes: first introducing rare earth metal M1 into molecular sieve A through ion exchange to obtain an intermediate, and then impregnating it with a loaded transition metal M2 to obtain M2@M1-molecular sieve A.

8. The application of the catalyst according to any one of claims 1-5 or the catalyst prepared by the method according to any one of claims 6 or 7 in the reaction of polycyclic aromatic hydrocarbons to BTX.

9. The application according to claim 8, characterized in that, Under hydrogen-containing conditions, polycyclic aromatic hydrocarbons react with the catalyst to produce BTX.

10. The application according to claim 8, characterized in that, The reaction conditions include: a reaction temperature of 200–500°C, a pressure of 0.1–4 MPa, and a feed mass hourly space velocity of 0.1–10 h⁻¹. -1 The hydrogen / polycyclic aromatic hydrocarbon molar ratio is (0.1~10):1.

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