Hydrodealkylation catalysts and methods of making, methods of making xylene

Abstract

The present application relates to the field of hydrodealkylation catalyst, discloses a kind of hydrodealkylation catalyst and preparation method, the preparation method of xylene, the catalyst includes carrier and first active component and second active component supported on the carrier;Wherein, the first active component is selected from at least one of group IA metal, group IIA metal and phosphorus;The second active component is selected from group VIII metal and / or group IVB metal;The carrier is molecular sieve with multistage pore structure, and the volume ratio of micropore and mesopore in the carrier is 1.5-8.5.The hydrodealkylation catalyst provided by the present application has higher hydrodealkylation activity, low aromatic ring loss rate, and can improve the selectivity of xylene in the hydrodealkylation reaction of ethylbenzene.

Description

Technical Field

[0001] This invention relates to the field of hydrodealkylation catalysts, specifically to a hydrodealkylation catalyst and its preparation method, and a method for preparing xylene. Background Technology

[0002] Paraxylene (PX) is an important basic chemical raw material, widely used in the production of polyester, synthetic fibers, and other industries. It is closely related to national economic development and people's basic needs, and its demand has been strong and rapidly increasing in recent years. Large-scale industrial production of aromatics is achieved through aromatics complex units, which typically include five basic units: catalytic reforming, aromatics extraction, disproportionation and alkyl transfer, xylene isomerization, and adsorption separation. Aromatics production technology is showing a trend towards using lower-quality raw materials, maximizing product yield, and minimizing energy and material consumption. Continuously improving the PX yield of complex units is one of the important directions for technological development.

[0003] The yield of PX or xylene in an aromatics complex depends primarily on the methylbenzene ring ratio in the feedstock; the higher the number of methyl groups in the feedstock, the higher the yield of PX or xylene. The C8 and C9 aromatics feedstocks in the aromatics complex contain a large amount of C2... + Side-chain alkyl aromatics, such as reformed C8 aromatics, contain approximately 18% ethylbenzene, and C9 aromatics contain approximately 35% methylbenzene and approximately 10% propylbenzene. Large amounts of C2 aromatics are involved in disproportionation and alkyl transfer, and deethylation isomerization techniques. + The side-chain alkyl removal reaction, in existing technology, involves removing this C2 portion. + All side chain substituents are removed to generate the corresponding C2. + Alkanes, such as methyl ethylbenzene, can be converted into toluene and ethane, and ethylbenzene can be converted into benzene and ethane.

[0004] In the traditional route, C2 + The side-chain substituents were not effectively utilized and therefore did not contribute to increasing xylene production. In 2021, ExxonMobil filed two aromatic C2 patent applications in the United States. + Patent applications for side-chain alkyl demethylation technology (US2021 / 0017102A1, US2021 / 0017103A1) can remove C2 from aromatic materials. + Side-chain substituents are converted into methyl groups through hydrogenation and demethylation reactions. For example, ethylbenzene is converted into xylene and methane, and ethylbenzene is converted into toluene and methane, thereby effectively increasing the number of methyl groups in the feedstock. Introducing this technology into aromatic hydrocarbon complexes effectively improves the PX yield of the unit. Therefore, developing aromatic C2... + Side-chain alkyl demethylation technology, utilizing aromatic C2 +Increasing the production of methyl by side-chain alkyl groups and improving the methylbenzene ring ratio in the combined unit can significantly improve the yield of PX or xylene, but this method is relatively complex.

[0005] In summary, the C2 in existing aromatic hydrocarbon complexes... + The side chain substituents have not been effectively utilized, and there is a lack of efficient industrial methods. Therefore, developing a xylene production technology with a wide range of raw material sources and high xylene yield is of great significance for increasing xylene production. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor hydrodealkylation activity, high aromatic ring loss rate, and poor xylene selectivity of existing hydrodealkylation catalysts, and to provide a hydrodealkylation catalyst and its preparation method, as well as a method for preparing xylene. This hydrodealkylation catalyst has better hydrodealkylation activity and a low aromatic ring loss rate.

[0007] To achieve the above objectives, the present invention provides a hydrodealkylation catalyst, the catalyst comprising a support and a first active component and a second active component supported on the support; The first active component is selected from at least one of Group IA metals, Group IIA metals and phosphorus; the second active component is selected from Group VIII metals and / or Group IVB metals; the support is a molecular sieve with a hierarchical porous structure, and the volume ratio of micropores to mesopores in the support is 1.5-8.5.

[0008] A second aspect of this invention provides a method for preparing a hydrogenation dealkylation catalyst, comprising the following steps: (1) A solution of a soluble compound containing the first active component is brought into contact with a support to perform a first ion exchange, thereby obtaining a catalyst precursor; (2) A solution of a soluble compound containing a second active component is contacted with the catalyst precursor to perform a second ion exchange, followed by drying and calcination to obtain the hydrogenation dealkylation catalyst; The first active component is selected from at least one of Group IA metals, Group IIA metals and phosphorus; the second active component is selected from Group VIII metals and / or Group IVB metals; the support is a molecular sieve with a hierarchical porous structure, and the volume ratio of micropores to mesopores in the support is 1.5-8.5.

[0009] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the above-described preparation method.

[0010] The fourth aspect of the present invention provides a method for preparing xylene, wherein ethylbenzene, hydrogen and a catalyst are contacted under hydrogenation dealkylation reaction conditions; The catalyst is the hydrogenation dealkylation catalyst provided in the first or third aspect above.

[0011] The hydrodealkylation catalyst provided by this invention has high hydrodealkylation activity, low aromatic ring loss rate, and can improve the selectivity of xylene in the hydrodealkylation reaction of ethylbenzene under the combined action of molecular sieve with multi-level porous structure, first active component and second active component.

[0012] The method for preparing the hydrogenation dealkylation catalyst provided by the present invention involves a two-step ion exchange in a specific sequence, in which the first and second active components are loaded onto the support in sequence. This method is beneficial for further optimizing the pore structure of the molecular sieve support and the acidity of the catalyst, thereby further improving the hydrogenation dealkylation activity of the catalyst, increasing benzene selectivity, and reducing the aromatic ring loss rate.

[0013] The method for preparing xylene provided by this invention flexibly uses mixed methyl and ethyl benzene aromatic hydrocarbons as raw materials and utilizes the hydrogenation and dealkylation reaction of the aromatic ring side chains to efficiently remove the C2 side chains on the methyl and ethyl benzene aromatic rings. + The methyl group on the group converts mixed ethylbenzene into xylene. The conversion rate of ethylbenzene is high, the selectivity of xylene is high, and the aromatic ring loss rate of ethylbenzene as raw material is low. The aromatic hydrocarbon yield can reach more than 99.5%, and the catalyst has good stability. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] In this invention, "ethylbenzene" refers to a product in which two hydrogen atoms on the benzene ring are replaced by methyl and ethyl, respectively, and there are three isomers: ortho, meta, and para. The ethylbenzene described in this invention can be one or more of the above three isomers or a mixture thereof.

[0016] In this invention, "xylene" refers to the product in which two hydrogen atoms on the benzene ring are replaced by methyl groups, and there are three isomers: ortho, meta, and para. The xylene described in this invention can be one or more of the above three isomers or a mixture thereof.

[0017] The first aspect of the present invention provides a hydrogenation dealkylation catalyst, the catalyst comprising a support and a first active component and a second active component supported on the support; The first active component is selected from at least one of Group IA metals, Group IIA metals and phosphorus; the second active component is selected from Group VIII metals and / or Group IVB metals; the support is a molecular sieve with a hierarchical porous structure, and the volume ratio of micropores to mesopores in the support is 1.5-8.5.

[0018] Existing hydrodealkylation catalysts often decarbonize C2 atoms in the dealkylation reaction of methyl ethyl phenyl. + All side chain substituents are removed to generate the corresponding C2. + Alkanes, such as methyl ethyl phenyl, can be converted into toluene and ethane. Therefore, xylene has poor selectivity, and C2... + Side-chain substituents also cannot be effectively utilized. Through continuous research, the inventors of this invention have discovered that by further adjusting the pore size distribution of the support through the combined action of a molecular sieve with a hierarchical porous structure, the first active component, and the second active component, the hydrodealkylation activity of the catalyst can be significantly improved, and the selectivity of xylene in the hydrodealkylation reaction of ethylbenzene can be increased, with a low aromatic ring loss rate.

[0019] According to the present invention, preferably, the volume ratio of micropores to mesopores in the carrier is 2.5-6.5.

[0020] Preferably, the average pore size of the mesopores is 4-18 nm, more preferably 4-10 nm. In the above-mentioned preferred cases, further optimization of the pore size distribution of the support can improve diffusion efficiency, thereby further enhancing the hydrogenation dealkylation activity of the catalyst, increasing xylene selectivity, and reducing aromatic ring loss rate.

[0021] According to the present invention, preferably, the catalyst has an average pore size of 4-15 nm, more preferably 6-10 nm.

[0022] According to the present invention, preferably, the total pore volume of the catalyst is 0.45-1.1 mL / g, more preferably 0.6-0.9 mL / g.

[0023] According to the present invention, preferably, the catalyst has a specific surface area of ​​100-250 m². 2 / g, preferably 120-205m 2 / g.

[0024] In this invention, the specific surface area and pore volume of the catalyst are determined using a low-temperature nitrogen adsorption method. Specifically, the nitrogen adsorption / desorption characterization is performed using a Micromeritics ASAP 2420 automated adsorption system. The sample is degassed at 350℃ and 1.33 Pa for 4 h, and then tested at -196℃ using nitrogen as the adsorbate. The specific surface area is calculated using the BET method, and the total pore volume is calculated based on the amount of N2 adsorbed when p / p0 = 0.99. The micropore volume and mesopore volume are calculated using the t-plot and BJH methods, respectively.

[0025] The average pore size of the mesopores in the carrier was determined using the BJH method, a mesopore analysis method.

[0026] In this invention, the selection range for the type of molecular sieve forming the support is relatively wide; it can be a single molecular sieve or a combination of several molecular sieves, as long as the volume ratio of micropores to mesopores in the support meets the above-mentioned range requirements. Preferably, the support is selected from at least one of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve, and mordenite molecular sieve.

[0027] More preferably, the support is a composite molecular sieve. Preferably, the support is selected from at least two of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve and mordenite molecular sieve, and the volume ratio of micropores to mesopores in each molecular sieve is independently 1.5-8.5, preferably 2.5-6.5. Using the above-mentioned composite support is beneficial to adjusting the distribution of acidic sites on the support, providing conditions for the loading of metal active components, and at the same time, it is beneficial to improve the hydrogenation dealkylation activity of the catalyst, improve xylene selectivity, and reduce the aromatic ring loss rate.

[0028] According to the most preferred embodiment of the present invention, the carrier includes ZSM-5 molecular sieve and mordenite molecular sieve, wherein the volume ratio of micropores to mesopores in ZSM-5 molecular sieve and mordenite molecular sieve is independently 1.5-8.5, preferably 2.5-6.5.

[0029] Preferably, the mass ratio of ZSM-5 molecular sieve to mordenite molecular sieve is 60-80:40-20.

[0030] According to the present invention, preferably, the first active component is selected from at least one of sodium, potassium, magnesium, barium, and phosphorus, more preferably from at least two of sodium, potassium, magnesium, and barium, more preferably from at least two of potassium, magnesium, and barium, and even more preferably from barium and magnesium; more preferably, the weight ratio of barium to magnesium, calculated as oxides, is 5-8.5:1. Using the above-mentioned preferred embodiments is beneficial for optimizing the pore structure and promoting the diffusion of ethylbenzene feedstock within the pores, thereby further improving the hydrogenation dealkylation activity of the catalyst, increasing xylene selectivity, and reducing the aromatic ring loss rate.

[0031] According to the present invention, preferably, the second active component is selected from at least one of rhodium, lanthanum, cerium, cobalt, nickel, and platinum, and more preferably from at least one of rhodium, lanthanum, cerium, and cobalt. The above-described preferred embodiments are beneficial for reducing the acidity of the molecular sieve, improving the metal catalytic activity, and further enhancing the catalytic efficiency of the catalyst.

[0032] In this invention, the first active component and the second active component can exist in the form of oxides, sulfides, elements, etc., without any particular limitation, and can be converted according to actual needs.

[0033] In this invention, preferably, the weight ratio of the support, the first active component (calculated as oxide), and the second active component (calculated as oxide) is 1:(0.01-0.03):(0.015-0.055); more preferably, it is 1:(0.015-0.025):(0.03-0.05). Adopting the above preferred embodiments is beneficial for optimizing the pore structure, reducing the acidity of the molecular sieve, promoting the diffusion of ethylbenzene feedstock within the pores, and further improving the catalytic efficiency of the catalyst.

[0034] The hydrodealkylation catalyst of the present invention can be prepared by loading the first active component and the second active component onto a support through a two-step ion exchange. Preferably, the first ion exchange and the second ion exchange are performed in sequence, which is beneficial to further improve the catalytic performance of the hydrodealkylation catalyst.

[0035] A second aspect of this invention provides a method for preparing a hydrogenation dealkylation catalyst, comprising the following steps: (1) A solution of a soluble compound containing the first active component is brought into contact with a support to perform a first ion exchange, thereby obtaining a catalyst precursor; (2) A solution of a soluble compound containing a second active component is contacted with the catalyst precursor to perform a second ion exchange, followed by drying and calcination to obtain the hydrogenation dealkylation catalyst; The first active component is selected from at least one of Group IA metals, Group IIA metals and phosphorus; the second active component is selected from Group VIII metals and / or Group IVB metals; the support is a molecular sieve with a hierarchical porous structure, and the volume ratio of micropores to mesopores in the support is 1.5-8.5.

[0036] The method for preparing the hydrogenation dealkylation catalyst provided by the present invention involves a two-step ion exchange in a specific sequence, in which the first and second active components are loaded onto the support in sequence. This method is beneficial for further optimizing the pore structure of the molecular sieve support and the acidity of the catalyst, thereby further improving the hydrogenation dealkylation activity of the catalyst, increasing benzene selectivity, and reducing the aromatic ring loss rate.

[0037] In this invention, the support is selected from the same range as the support in the above-mentioned hydrodealkylation catalyst, and will not be described again here.

[0038] According to the present invention, when the support is a composite molecular sieve, step (1) further includes: mixing the molecular sieve uniformly to obtain the support. The mixing can be carried out using conventional methods in the art, as long as the components are mixed uniformly, and the present invention does not have any special limitations in this regard.

[0039] According to the present invention, preferably, the first active component is selected from at least one of sodium, potassium, magnesium, barium and phosphorus, more preferably at least two of sodium, potassium, magnesium and barium, more preferably at least two of potassium, magnesium and barium, and even more preferably barium and magnesium; and even more preferably, the weight ratio of barium to magnesium, based on oxides, is 5-8.5:1.

[0040] The above-described preferred embodiments are beneficial for optimizing the pore structure and promoting the diffusion of ethylbenzene feedstock within the pores, thereby further improving the hydrogenation dealkylation activity of the catalyst, increasing xylene selectivity, and reducing the aromatic ring loss rate.

[0041] In this invention, the range of soluble compounds for the first active component is relatively wide, and can be soluble salts of the first active component. Preferably, the soluble compounds for the first active component are selected from at least one of sulfates, nitrates, phosphates and carbonates of the first active component.

[0042] According to the present invention, there are no special requirements for the concentration of the solution containing the soluble compound of the first active component, as long as it meets the content range of the first active component in the catalyst. Preferably, the concentration of the solution containing the soluble compound of the first active component is 0.05-0.6 mol / L, and more preferably 0.1-0.4 mol / L, based on elemental composition.

[0043] According to the present invention, preferably, the second active component is selected from at least one of rhodium, lanthanum, cerium, cobalt, nickel, and platinum, and more preferably from at least one of rhodium, lanthanum, cerium, and cobalt. The above-described preferred embodiments are beneficial for reducing the acidity of the molecular sieve, improving the metal catalytic activity, and further enhancing the catalytic efficiency of the catalyst.

[0044] In this invention, the range of soluble compounds for the second active component is relatively wide. Preferably, the soluble compounds for the second active component are selected from at least one of the nitrate, chloroplatinic acid, molybdate, and sulfate of the second active component.

[0045] According to the present invention, the concentration range of the solution containing the soluble compound of the second active component is relatively wide, as long as it can meet the content range of the second active component in the catalyst. Preferably, the concentration of the solution containing the soluble compound of the second active component is 0.1-0.8 mol / L, and more preferably 0.2-0.6 mol / L, based on elemental composition.

[0046] In this invention, preferably, the amounts of the support, the solution of the soluble compound containing the first active component, and the solution of the soluble compound containing the second active component are such that the weight ratio of the support, the first active component (calculated as oxide), and the second active component (calculated as oxide) in the prepared catalyst is 1:(0.01-0.03):(0.015-0.055); more preferably, it is 1:(0.015-0.025):(0.03-0.05).

[0047] In this invention, the first and second ion exchanges can be performed using methods conventional in the art, as long as the above-mentioned requirements for the amount of the first and second active components are met; this invention does not have any special limitations in this regard. The first and second ion exchanges can each include one or more exchanges, and drying can be performed after each exchange.

[0048] According to the present invention, preferably, the conditions for the first ion exchange include: a temperature of 50-90°C, preferably 60-80°C; and a time of 2-6 h, preferably 3-5 h.

[0049] According to the present invention, preferably, the conditions for the second ion exchange include: a temperature of 40-95°C, preferably 55-90°C; and a time of 2-6 h, preferably 3-5 h.

[0050] In this invention, the conditions for the first ion exchange and the second ion exchange can be the same or different.

[0051] In this invention, preferably, the preparation method further includes: performing solid-liquid separation on the product of the second ion exchange, followed by drying and calcination. The solid-liquid separation can be performed using methods conventional in the art, such as filtration.

[0052] In this invention, there are no special limitations on the drying conditions, and conventional operating conditions in the art can be used. Preferably, the drying conditions include: a temperature of 80-180℃, more preferably 90-130℃; and a time of 5-15 hours, more preferably 8-11 hours.

[0053] In this invention, preferably, the calcination conditions include: a temperature of 400-600℃, more preferably 450-550℃; and a time of 2-8 h, more preferably 2-6 h.

[0054] In this invention, preferably, the preparation method further includes a molding step, which can be performed after the second ion exchange or after calcination. The molding method can be selected according to the needs of the actual application, so that the catalyst has a certain strength and morphology. For example, the molding method can be tableting.

[0055] A third aspect of the present invention provides a hydrogenation dealkylation catalyst prepared by the above-described preparation method.

[0056] The fourth aspect of the present invention provides a method for preparing xylene, wherein ethylbenzene, hydrogen and a catalyst are contacted under hydrogenation dealkylation reaction conditions; The catalyst is a hydrogenation dealkylation catalyst provided in the first or third aspect.

[0057] Preferably, the ethylbenzene includes at least one of p-ethylbenzene, m-ethylbenzene, and ortho-ethylbenzene.

[0058] In the above preparation method, mixed methyl and ethylbenzene aromatics are flexibly used as raw materials, and the side chain C2 of the aromatic ring is efficiently removed by the hydrogenation and dealkylation reaction of the aromatic ring side chain. + The methyl group on the group converts mixed ethylbenzene into xylene, with high conversion rate of ethylbenzene, high selectivity of xylene, and low loss rate of aromatic ring of ethylbenzene as raw material.

[0059] According to the present invention, those skilled in the art can rationally select the specific process conditions for the hydrodealkylation reaction, and can achieve considerable technical effects. Preferably, the hydrodealkylation reaction conditions include: a reaction temperature of 400-650℃, preferably 420-630℃; a pressure of 0.1-5 MPa, preferably 0.5-3.5 MPa; and a mass hourly space velocity (HSV) of methyl ethylbenzene of 1-10 h⁻¹. -1 Preferably 2-5h -1 The hydrogen-to-oil volume ratio is 800-1500, preferably 1000-1250.

[0060] In this invention, preferably, the method further includes: reducing the catalyst by contacting it with hydrogen gas before use. The reduction aims to at least partially convert the second active component into an element.

[0061] Preferably, the reduction temperature is 400-650℃, more preferably 500-650℃, the time is 1-5 h, more preferably 2.5-4 h, the heating rate is 1-5℃ / min, more preferably 2.5-3.5℃ / min, and the hydrogen volume hourly space velocity is 10-25 h⁻¹. -1 Preferably 15-20h -1 .

[0062] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0063] The present invention will be described in detail below through embodiments.

[0064] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0065] In the following examples, the specific surface area and pore volume of the catalyst were determined using a low-temperature nitrogen adsorption method. Specifically, nitrogen adsorption / desorption characterization was performed using a Micromeritics ASAP 2420 automated adsorption system. The sample was degassed at 350℃ and 1.33 Pa for 4 h, and then tested at -196℃ using nitrogen as the adsorbate. The specific surface area was calculated using the BET method, and the total pore volume was calculated based on the amount of N2 adsorbed at p / p0 = 0.99. The micropore volume and mesopore volume were calculated using the t-plot and BJH methods, respectively.

[0066] The mesopore size of the carrier was determined using the BJH method, a mesopore analysis method.

[0067] The following examples illustrate the hydrodealkylation catalyst and its preparation method provided by the present invention. Example 1 a. Select ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 3.5 and a mesopore pore size of 5 nm, and mordenite molecular sieve with a micropore to mesopore volume ratio of 3 and a mesopore pore size of 5.5 nm. Mix the two molecular sieves evenly according to a weight ratio of ZSM-5 molecular sieve to mordenite molecular sieve of 80:20 to obtain a support. The physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution of barium nitrate and magnesium acetate, wherein the concentration of barium nitrate is 0.2 mol / L and the concentration of magnesium acetate is 0.1 mol / L; take 10.0 g of the mixed molecular sieve from a, and perform the first ion exchange in 100 mL of the above mixed solution at 75℃ for 3 h, exchange once, and after filtration and separation, obtain the catalyst precursor; c. Prepare a 0.5 mol / L rhodium chloride solution. At 85°C, take the catalyst precursor obtained in step b and perform a second ion exchange in 150 mL of rhodium chloride solution for 5 h, repeating the exchange once. After filtering, the product is dried at 120°C for 4 h and then calcined at 550°C for 4 h. The finished catalyst is obtained by tableting. In the obtained catalyst, the weight ratio of barium to magnesium, calculated as oxides, is 6:1.

[0068] The physicochemical properties of the finished catalyst, including total pore volume, specific surface area, and average pore diameter, are shown in Table 2.

[0069] Example 2 a. Select ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 3.5 and a mesopore pore size of 5 nm. Mix the molecular sieve support evenly. The composition and physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution of diammonium hydrogen phosphate and magnesium acetate, wherein the concentration of diammonium hydrogen phosphate is 0.1 mol / L and the concentration of magnesium acetate is 0.1 mol / L; take 10.0 g of the mixed molecular sieve from a, and carry out the first ion exchange in 100 mL of the above mixed solution at 75℃ for 3 h, exchange once, and after filtration and separation, obtain the catalyst precursor; c. Prepare a 0.5 mol / L rhodium chloride solution. At 85℃, take the catalyst precursor obtained in step b and perform a second ion exchange in 150 mL of rhodium chloride solution for 5 h, repeating the exchange once. After filtering, the product is dried at 120℃ for 4 h and then calcined at 450℃ for 4 h. The finished catalyst is obtained by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0070] Example 3 a. Select X molecular sieve with a micropore to mesopore volume ratio of 2.5 and a mesopore diameter of 4 nm, and Y molecular sieve with a micropore to mesopore volume ratio of 6.5 and a mesopore diameter of 5.5 nm. Mix the two molecular sieves evenly according to the weight ratio of X molecular sieve to Y molecular sieve of 60:40 to obtain the support. The physicochemical properties of the support are shown in Table 1. b. Prepare a 0.15 mol / L barium nitrate solution; take 10.0 g of the mixed molecular sieve from a, and perform the first ion exchange in 100 mL of the above mixed solution at 75℃ for 3 h. After one exchange, filter and separate to obtain the catalyst precursor. c. Prepare a 0.5 mol / L cobalt acetate solution. At 85℃, take the molecular sieve exchanged in step b and perform a second ion exchange in 150 mL of cobalt acetate solution for 5 h, repeating the exchange once. After filtration, the molecular sieve is dried at 120℃ for 4 h and then calcined at 500℃ for 4 h. The finished catalyst is obtained by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0071] Example 4 a. Select a β molecular sieve with a micropore to mesopore volume ratio of 3.5 and a mesopore pore size of 3.8 nm. The physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution of potassium nitrate and magnesium acetate, wherein the concentration of potassium nitrate is 0.08 mol / L and the concentration of magnesium acetate is 0.12 mol / L; take 10.0 g of the mixed molecular sieve from a, and perform the first ion exchange in 100 mL of the above mixed solution at 75℃ for 3 h, exchange once, and after filtration, obtain the catalyst precursor; c. Prepare a 0.25 mol / L lanthanum nitrate solution. At 85℃, take the catalyst precursor obtained in step b and perform a second ion exchange in 150 mL of lanthanum nitrate solution for 5 h, repeating the exchange once. After filtration through molecular sieve, dry at 120℃ for 4 h, and then calcine at 550℃ for 4 h. Obtain the finished catalyst by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0072] Example 5 a. Select ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 2.5 and a mesopore diameter of 10 nm, and mordenite molecular sieve with a micropore to mesopore volume ratio of 6.5 and a mesopore diameter of 4.0 nm. Mix the two molecular sieves evenly according to a weight ratio of 80:20 to obtain the support. The physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution of barium nitrate and magnesium acetate, wherein the concentration of barium nitrate is 0.05 mol / L and the concentration of magnesium acetate is 0.03 mol / L; take 10.0 g of the mixed molecular sieve from a, and carry out the first ion exchange in 100 mL of the above mixed solution at 75℃ for 3 h, exchange once, and after filtration and separation, obtain the catalyst precursor; c. Prepare a 0.25 mol / L lanthanum nitrate solution. At 65℃, take the molecular sieve exchanged in step b and perform a second ion exchange in 150 mL of lanthanum nitrate solution for 5 h, repeating the exchange once. After filtration, the molecular sieve is dried at 120℃ for 4 h and then calcined at 500℃ for 4 h. The finished catalyst is obtained by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0073] Example 6 a. Select ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 2.5 and a mesopore diameter of 10 nm, and mordenite molecular sieve with a micropore to mesopore volume ratio of 6.5 and a mesopore diameter of 4.0 nm. Mix the two molecular sieves evenly according to a weight ratio of 80:20 to obtain the support. The physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution with a concentration of 0.25 mol / L diammonium hydrogen phosphate; take 10.0 g of the mixed molecular sieve from a, and perform the first ion exchange in 100 mL of the above mixed solution at 80℃ for 3 h. After one exchange, filter and separate to obtain the catalyst precursor. c. Prepare a 0.15 mol / L cerium nitrate solution. At 65℃, take the molecular sieve exchanged in step b and perform a second ion exchange in 150 mL of cerium nitrate solution for 3 hours, repeating the exchange once. After filtration, the molecular sieve is dried at 120℃ for 4 hours and then calcined at 450℃ for 4 hours. The finished catalyst is obtained by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0074] Example 7 a. Select ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 0.8 and an average mesopore diameter of 3.5 nm, and mordenite molecular sieve with a micropore to mesopore volume ratio of 1.5 and an average mesopore diameter of 4.5 nm. Mix the two molecular sieves evenly according to a weight ratio of 80:20 to obtain the support. The physicochemical properties of the support are shown in Table 1. b. Prepare a mixed solution of diammonium hydrogen phosphate and barium nitrate, wherein the concentration of diammonium hydrogen phosphate is 0.25 mol / L and the concentration of barium nitrate is 0.05 mol / L; take 10.0 g of the mixed molecular sieve from a, and perform the first ion exchange in 100 mL of the above mixed solution at 65 ℃ for 3 h, exchange once, and after filtration and separation, obtain the catalyst precursor; c. Prepare a 0.25 mol / L cobalt acetate solution. At 65℃, perform a second ion exchange on the molecular sieve exchanged in step b in 150 mL of cerium nitrate solution for 5 h, repeating the exchange once. After filtration, the molecular sieve is dried at 120℃ for 4 h and then calcined at 500℃ for 4 h. The finished catalyst is obtained by tableting. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0075] Example 8 The method of Example 1 was followed, except that in step a, the support was selected as a mordenite molecular sieve with a microporous to mesoporous volume ratio of 3.0 and an average mesopore diameter of 5.5 nm. The temperature of the first ion exchange was 45 °C. All other parameters were the same as in Example 1, and the finished catalyst was obtained. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore diameter, are shown in Table 2.

[0076] Example 9 The method is the same as in Example 1, except that in step a, ZSM-5 molecular sieve with a micropore to mesopore volume ratio of 9.1 and a mesopore diameter of 16.5 nm and mordenite molecular sieve with a micropore to mesopore volume ratio of 6.4 and a mesopore diameter of 10.6 nm are selected. The two molecular sieves are mixed evenly according to a weight ratio of 80:20 between ZSM-5 molecular sieve and mordenite molecular sieve to obtain a support. The physicochemical properties of the support are shown in Table 1. The rest of the process was the same as in Example 1, and the finished catalyst was obtained. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0077] Example 10 Following the method of Example 1, except that in step c, the calcination temperature was 400℃, while the rest were the same as in Example 1, the finished catalyst was obtained. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore diameter, are shown in Table 2.

[0078] Example 11 The method was followed in Example 1, except that a second ion exchange was performed first, followed by a first ion exchange, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0079] Example 12 Following the method of Example 1, except that the first active component includes only Ba and does not contain Mg, the finished catalyst was obtained. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0080] Comparative Example 1 The method is the same as in Example 1, except that in step a, neither ZSM-5 molecular sieve nor mordenite molecular sieve contains mesopores, the pore volume of the support is 0.86 mL / g, the average pore size is 0.55 nm, and the physicochemical properties of the support are shown in Table 1. The rest of the process was the same as in Example 1, and the finished catalyst was obtained. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0081] Comparative Example 2 Following the method of Example 1, except that the first ion exchange was not performed, the rest were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0082] Comparative Example 3 Following the method of Example 1, except that a second ion exchange was not performed, all other aspects were the same as in Example 1, to obtain the finished catalyst. The physicochemical properties of the finished catalyst, such as total pore volume, specific surface area, and average pore size, are shown in Table 2.

[0083] Table 1

[0084] Table 2

[0085] The following test examples are used to evaluate the catalytic performance of the hydrodealkylation catalyst provided by the present invention in the reaction of ethylbenzene to xylene via hydrodealkylation.

[0086] Test case Take 5.0 g of the finished catalyst prepared in the above examples and comparative examples, respectively, and pack it into a micro adiabatic fixed-bed reactor with an inner diameter of 1.5 cm. The upper and lower parts of the reaction bed are filled with glass beads. Then, hydrogen gas is introduced to ensure that the gas flow is uniformly through the catalyst bed. The mass hourly space velocity of hydrogen is 18 h⁻¹. -1 After a 200-minute programmed temperature rise to the reaction temperature of 600℃, and holding at that temperature for 2 hours, a mixed methylbenzene feedstock was introduced using a metering pump while maintaining the same temperature. The weight ratio of p-methylbenzene, m-methylbenzene, and cat-methylbenzene in the mixed feedstock was 25:50:25. The mass hourly space velocity (WHSV) of the mixed feedstock was maintained at 1.0 h⁻¹. -1 The reaction pressure was 3.0 MPa, and the hydrogen-to-oil volume ratio was 10:20. By metering and analyzing the oil and water phases in the catalytic reaction effluent and the reaction tail gas using gas chromatography, the conversion rate of ethylbenzene, xylene selectivity, aromatic ring loss rate, and stability of the reaction were finally calculated. Specific results are shown in Table 3.

[0087] The formulas for calculating the conversion rate of ethylbenzene, xylene selectivity, aromatic ring loss rate, and aromatic hydrocarbon yield are as follows: ethylbenzene conversion rate (%) = ×100%; Xylene selectivity (%) = ×100%; Aromatic ring loss rate (%) = ×100%; Aromatic yield (%) = 100% - Aromatic ring loss rate; Stability evaluation: Catalyst stability refers to the ability of a catalyst to maintain its activity, selectivity, anti-toxicity, thermal stability, and other properties and structures unchanged during a catalytic reaction. In this invention, catalyst stability is characterized by the time it takes for the xylene conversion to drop to 90% of its initial conversion during the reaction.

[0088] Table 3

[0089] The results above show that the hydrogenation dealkylation catalyst provided by this invention has a high conversion rate of ethylbenzene and a high selectivity for xylene in the hydrogenation dealkylation reaction of ethylbenzene. The aromatic ring loss rate of ethylbenzene as a raw material is low, and the aromatic hydrocarbon yield can reach more than 99.24%, with a maximum of 99.88%. In addition, the catalyst has good stability.

[0090] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A hydrogenation dealkylation catalyst, characterized in that, The catalyst comprises a support and a first active component and a second active component supported on the support; the hydrogenation dealkylation refers to the reaction of hydrogenation dealkylation of ethylbenzene to produce xylene; The first active component is selected from at least one of sodium, potassium, magnesium, barium and phosphorus; The second active component is selected from at least one of rhodium, lanthanum, cerium, cobalt, nickel and platinum; the support is a molecular sieve with a hierarchical porous structure, wherein the volume ratio of micropores to mesopores in the support is 1.5-8.5; The weight ratio of the carrier, the first active component (based on oxides), and the second active component (based on oxides) is 1:(0.01-0.03):(0.015-0.055). The catalyst has an average pore size of 4-15 nm and a total pore volume of 0.45-1.1 mL / g.

2. The catalyst according to claim 1, wherein, The volume ratio of micropores to mesopores in the carrier is 2.5-6.5; And / or, the specific surface area of ​​the catalyst is 100-250 m². 2 / g.

3. The catalyst according to claim 2, wherein, The catalyst has a specific surface area of ​​120-205 m². 2 / g.

4. The catalyst according to claim 1, wherein, The average pore size of the mesopores is 4-18 nm.

5. The catalyst according to claim 4, wherein, The average pore size of the mesopores is 4-10 nm.

6. The catalyst according to claim 1, wherein, The catalyst has an average pore size of 6-10 nm.

7. The catalyst according to claim 1, wherein, The total pore volume of the catalyst is 0.6-0.9 mL / g.

8. The catalyst according to claim 1, wherein, The carrier is selected from at least one of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve and mordenite molecular sieve.

9. The catalyst according to claim 8, wherein, The carrier is selected from at least two of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve and mordenite molecular sieve, and the volume ratio of micropores to mesopores in each molecular sieve is independently 1.5-8.

5.

10. The catalyst according to claim 8, wherein, The first active component is selected from at least two of sodium, potassium, magnesium and barium.

11. The catalyst according to claim 8, wherein, The second active component is selected from at least one of rhodium, lanthanum, cerium and cobalt.

12. The catalyst according to claim 10, wherein, The first active component is at least two of potassium, magnesium and barium.

13. The catalyst according to claim 12, wherein, The first active component is barium and magnesium.

14. The catalyst according to any one of claims 1-13, wherein, The weight ratio of the carrier, the first active component (calculated as oxide), and the second active component (calculated as oxide) is 1:(0.015-0.025):(0.03-0.05).

15. A method for preparing a hydrodealkylation catalyst according to any one of claims 1-14, characterized in that, Includes the following steps: (1) A solution of a soluble compound containing the first active component is brought into contact with a support to perform a first ion exchange, thereby obtaining a catalyst precursor; (2) A solution of a soluble compound containing a second active component is contacted with the catalyst precursor to perform a second ion exchange, followed by drying and calcination to obtain the hydrogenation dealkylation catalyst; The first active component is selected from at least one of sodium, potassium, magnesium, barium and phosphorus; The second active component is selected from at least one of rhodium, lanthanum, cerium, cobalt, nickel and platinum; the support is a molecular sieve with a hierarchical porous structure, wherein the volume ratio of micropores to mesopores in the support is 1.5-8.5; The amounts of the support, the solution containing the first active component, and the solution containing the second active component are such that the weight ratio of the support, the first active component (calculated as oxide), and the second active component (calculated as oxide) in the prepared catalyst is 1:(0.015-0.025):(0.03-0.05).

16. The preparation method according to claim 15, wherein, The volume ratio of micropores to mesopores in the carrier is 2.5-6.5; And / or, the specific surface area of ​​the catalyst is 100-250 m². 2 / g.

17. The preparation method according to claim 16, wherein, The catalyst has a specific surface area of ​​120-205 m². 2 / g.

18. The preparation method according to claim 15, wherein, The average pore size of the mesopores is 4-18 nm.

19. The preparation method according to claim 18, wherein, The average pore size of the mesopores is 4-10 nm.

20. The preparation method according to claim 15, wherein, The catalyst has an average pore size of 4-15 nm.

21. The preparation method according to claim 20, wherein, The catalyst has an average pore size of 6-10 nm.

22. The preparation method according to claim 15, wherein, The catalyst has a pore volume of 0.45-1.1 mL / g.

23. The preparation method according to claim 22, wherein, The catalyst has a pore volume of 0.6-0.9 mL / g.

24. The preparation method according to claim 15, wherein, The support is selected from at least one of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve and mordenite molecular sieve; And / or, the soluble compound of the first active component is selected from at least one of the sulfate, nitrate, phosphate and carbonate of the first active component; And / or, the soluble compound of the second active component is selected from at least one of the nitrate, chloroplatinic acid, molybdate and sulfate of the second active component.

25. The preparation method according to claim 24, wherein, The carrier is selected from at least two of ZSM-5 molecular sieve, β molecular sieve, X molecular sieve, Y molecular sieve and mordenite molecular sieve, and the volume ratio of micropores to mesopores in each molecular sieve is independently 1.5-8.5; And / or, the first active component is selected from at least two of sodium, potassium, magnesium and barium; And / or, the second active component is selected from at least one of rhodium, lanthanum, cerium and cobalt.

26. The preparation method according to claim 25, wherein, The first active component is at least two of potassium, magnesium and barium.

27. The preparation method according to claim 26, wherein, The first active component is barium and magnesium.

28. The preparation method according to any one of claims 15-27, wherein, The amounts of the support, the solution containing the first active component, and the solution containing the second active component are used such that, in the catalyst prepared, the weight ratio of the support, the first active component (calculated as oxide), and the second active component (calculated as oxide) is 1:(0.01-0.03):(0.015-0.055). And / or, the conditions for the first ion exchange include: a temperature of 50-90°C; and a time of 2-6 h; And / or, the conditions for the second ion exchange include: a temperature of 40-95°C; and a time of 2-6 h; And / or, the drying conditions include: a temperature of 80-180°C; and a time of 5-15 h; And / or, the calcination conditions include: a temperature of 400-600℃; and a time of 2-8 h.

29. The preparation method according to claim 28, wherein, The amounts of the support, the solution containing the first active component, and the solution containing the second active component are used such that, in the catalyst prepared, the weight ratio of the support, the first active component (calculated as oxide), and the second active component (calculated as oxide) is 1:(0.015-0.025):(0.03-0.05). And / or, the conditions for the first ion exchange include: a temperature of 60-80°C; and a time of 3-5 hours; And / or, the conditions for the second ion exchange include: a temperature of 55-90°C; and a time of 3-5 hours; And / or, the drying conditions include: a temperature of 90-130°C; and a time of 8-11 h; And / or, the calcination conditions include: a temperature of 450-550°C; and a time of 2-6 h.

30. The hydrogenation dealkylation catalyst prepared by the method according to any one of claims 15-29.

31. A method for preparing xylene, characterized in that, Under the conditions of hydrogenation dealkylation reaction, ethylbenzene, hydrogen gas and catalyst are brought into contact; The catalyst is a hydrodealkylation catalyst according to any one of claims 1-14 or 30.

32. The preparation method according to claim 31, wherein, The ethylbenzene includes at least one of p-ethylbenzene, m-ethylbenzene, and o-ethylbenzene.

33. The preparation method according to claim 31, wherein, The hydrogenation dealkylation reaction conditions include: a reaction temperature of 400-650℃; a pressure of 0.1-5 MPa; and a mass hourly space velocity (HSV) of methyl ethylbenzene of 1-10 h⁻¹. -1 The hydrogen-to-oil volume ratio is 800-1500.

34. The preparation method according to claim 33, wherein, The hydrogenation dealkylation reaction conditions include: a reaction temperature of 420-630℃; a pressure of 0.5-3.5 MPa; and a mass hourly space velocity (HHSV) of ethylbenzene of 2-5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 1000-1250.

35. The preparation method according to any one of claims 31-34, wherein, The method further includes reducing the catalyst by contacting it with hydrogen before use.

36. The preparation method according to claim 35, wherein, The reduction is carried out at a temperature of 400-650℃ for 1-5 hours, with a heating rate of 1-5℃ / min and a hydrogen volume hourly space velocity of 10-25 h⁻¹. -1 .

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