Metal modified molecular sieve catalyst as well as preparation method and application thereof

Abstract

The invention discloses a metal modified molecular sieve catalyst and a preparation method and application thereof. The catalyst is a metal-loaded molecular sieve which is modified by post-treatment after a metal component is loaded on the molecular sieve; the molecular sieve is selected from at least one of H-ZSM-5, H-Beta, H-ZSM-35, H-MOR, H-MCM-22, H-ZSM-11 and H-ZSM-22, and the molecular sieve is selected from at least one of H-ZSM-5, H-Beta, the metal is loaded on the molecular sieve through ion exchange and / or impregnation; the post-treatment modification is selected from at least one of heating treatment, water vapor treatment and silanization treatment. The metal component of the catalyst can catalyze dehydrogenation reaction and carbon dioxide activation, the molecular sieve component provides a substance diffusion channel and an acid center, and post-treatment modification can regulate the distribution of the molecular sieve acid center and improve the hydrothermal stability of the catalyst. The catalyst can efficiently promote the coupling reaction of cycloalkane and carbon dioxide, the selectivity of aromatic hydrocarbon reaches 90% or above, and the conversion rate of carbon dioxide reaches 20% or above.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of petrochemical industry, and particularly relates to a metal-modified molecular sieve catalyst and a preparation method and application thereof. BACKGROUND

[0002] Aromatic hydrocarbons are basic products of modern petrochemical industry and one of the most important basic raw materials in chemical production, which plays a basic supporting role in the chemical industry and its downstream fine product industry. With the rapid and sustained growth of China's economy, China is currently the largest country in terms of demand for aromatic hydrocarbons, and aromatic hydrocarbon products are in short supply. At present, aromatic hydrocarbons are mainly produced by catalytic reforming of naphtha, which accounts for about 70% of the aromatic hydrocarbon production. Technically, aromatic hydrocarbons are generated from naphtha, which not only requires a Pt-based noble metal catalytic reforming step, but also requires multiple supporting devices, a complex process, difficult separation, and high energy consumption.

[0003] The production of aromatic hydrocarbons through alkanes aromatization is a very valuable but challenging path, and the catalyst used is mainly a metal-modified molecular sieve. Among them, the molecular sieve used mainly includes ZSM-5, MCM-22 and L molecular sieve, and the metal used mainly includes Zn, Ni and Ga, etc. These metals are easy to lose and sinter in the aromatization process, which causes irreversible deactivation of the catalyst. The H / C ratio of alkanes is higher than that of aromatic hydrocarbons, and the molecular sieve catalyzes alkanes to produce aromatic hydrocarbons, which follows a hydrogen transfer route. Therefore, a large amount of hydrogen-rich methane is generated at the same time, and the selectivity of aromatic hydrocarbons is limited.

[0004] With the development of industry, more and more carbon dioxide (CO2) is discharged. As is known, CO2 is a major greenhouse gas, and large-scale CO2 emissions can cause serious environmental problems, so it is urgent to recover and utilize CO2. The preparation of aromatic hydrocarbons through the coupling reaction of alkanes and CO2 is a very potential way, in which CO2 can neutralize the hydrogen in alkanes, regulate the product distribution, and improve the yield of aromatic hydrocarbons. Due to the inertness of CO2, metal catalysts or metal-modified molecular sieve catalysts are required for catalyzing CO2.

[0005] Patent CN115851309A discloses a method for converting naphtha and carbon dioxide into aromatic hydrocarbons, but it is difficult to generate aromatic hydrocarbons from a large amount of linear alkane components in naphtha, the selectivity of aromatic hydrocarbons has certain limitations, and the catalyst is easy to deactivate. Although patent CN116120139A discloses a method for generating aromatic hydrocarbons through the coupling of alkanes and carbon dioxide using a zeolite molecular sieve, it is proposed that a solid acid catalyst (zeolite molecular sieve) can be used to catalyze the process, but the activation ability of the molecular sieve for carbon dioxide is insufficient, resulting in insufficient conversion of carbon dioxide in the process. SUMMARY

[0006] In view of this, the application provides a metal-modified molecular sieve catalyst, a preparation method and application thereof, and mainly aims to solve the technical problem of low selectivity of the catalyst in catalyzing naphthenes and carbon dioxide to produce aromatic hydrocarbons.

[0007] In one aspect, the application provides a metal-modified molecular sieve catalyst, wherein the catalyst is a supported metal molecular sieve after a molecular sieve is loaded with a metal component and then modified by post-treatment;

[0008] The molecular sieve in the catalyst is at least one selected from H-ZSM-5, H-Beta, H-ZSM-35, H-MOR, H-MCM-22, H-ZSM-11 and H-ZSM-22 molecular sieves.

[0009] The metal in the catalyst is loaded on the molecular sieve by ion exchange and / or impregnation;

[0010] The post-treatment modification of the catalyst is at least one selected from heating treatment, water vapor treatment and silanization treatment.

[0011] The molecular sieve used in the catalyst of the application is at least one selected from molecular sieves with ten-membered ring pore channel structure and twelve-membered ring pore channel structure.

[0012] The application improves the dehydrogenation active center and carbon dioxide activation center by the metal component to catalyze isomerization and aromatization reactions. Compared with the complexity of naphtha to aromatic hydrocarbon reaction and the need for isomerization, aromatization and other complex processes for straight-chain alkanes to produce aromatic hydrocarbons, naphthenes can generate aromatic hydrocarbons through a simple dehydrogenation process. The process from naphthenes to aromatic hydrocarbons is a process of reducing the H / C ratio, and the introduction of carbon dioxide with H deficiency can adjust the H / C ratio in the product and improve the yield of aromatic hydrocarbons. At the same time, carbon dioxide can react with the H2 product in the dehydrogenation reaction to promote the dehydrogenation reaction and improve the efficiency of aromatic hydrocarbon generation. It also solves the problem of how to effectively utilize the large amount of carbon dioxide byproduct in the chemical process, improving the economy.

[0013] Optionally, the metal in the catalyst is at least one selected from metals Zn, Cu, Ga, Cr, Fe, Mo, Ir and La.

[0014] Optionally, the loading amount of the metal component in the catalyst is 0.5-5.0 wt.% based on the total mass of the catalyst.

[0015] Optionally, the loading amount of the metal component in the catalyst is selected from any one of 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.% or a range value between any two thereof.

[0016] In a second aspect, the application provides a preparation method of the metal-modified molecular sieve catalyst, which comprises the following steps:

[0017] S1: mixing a molecular sieve and an aqueous solution of a metal-soluble salt, and performing ion exchange and / or impregnation to obtain a product I of the molecular sieve loaded with metal;

[0018] S2: drying and calcining the product I of the molecular sieve loaded with metal to obtain a product II of calcination;

[0019] S3: modifying the product II of calcination in step S2 through post-treatment to obtain the metal-modified molecular sieve catalyst.

[0020] The application has the advantages of simple preparation process, good catalyst performance, and solving the problems of high cost of catalyst and easy loss and sintering of metal components.

[0021] Optionally, the metal-soluble salt in step S1 is at least one selected from metal nitrate, carbonate, chloride and acetylacetone salt.

[0022] Optionally, the liquid-solid phase mass ratio of the aqueous solution of the metal-soluble salt to the molecular sieve is (10-1):1.

[0023] Optionally, the ion exchange temperature is 50-100°C, and the ion exchange time is 1-10 hours.

[0024] Optionally, the exchange temperature can be independently selected from any value or a value range between any two of 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C and 100°C.

[0025] Optionally, the ion exchange time can be independently selected from any value or a value range between any two of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours and 10 hours.

[0026] Optionally, the impregnation temperature is 25-70°C, and the impregnation time is 1-4 hours.

[0027] Optionally, the impregnation temperature can be independently selected from any value or a value range between any two of 25°C, 30°C, 40°C, 50°C, 60°C and 70°C.

[0028] Optionally, the impregnation time can be independently selected from any value or a value range between any two of 1 hour, 2 hours, 3 hours and 4 hours.

[0029] Optionally, in step S2, the drying process comprises drying at a temperature of 80-150°C under air or nitrogen atmosphere.

[0030] Optionally, the drying temperature is selected from any of 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C and 150°C or a value within a range between any two of them.

[0031] Optionally, the calcination process comprises calcination at a temperature of 500-700°C under air or nitrogen atmosphere.

[0032] Optionally, the calcination temperature is selected from any of 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C and 700°C or a value within a range between any two of them.

[0033] Optionally, in step S3, the post-treatment modification is at least one selected from high-temperature heat treatment, high-temperature water vapor treatment and silanization.

[0034] Optionally, the high-temperature heat treatment is calcination at a temperature of 600-800°C under air atmosphere, and the calcination time is 4-12 hours.

[0035] Optionally, the high-temperature heat treatment temperature is selected from any of 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, 750°C, 775°C and 800°C or a value within a range between any two of them.

[0036] Optionally, the calcination time of the high-temperature heat treatment is selected from any of 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 8 hours, 10 hours, 11 hours and 12 hours or a value within a range between any two of them.

[0037] Optionally, the high-temperature water vapor treatment method comprises the following steps:

[0038] a) loading the calcined metal-modified molecular sieve into a fixed-bed reaction tube, and passing dry air to heat to 600-850°C;

[0039] b) passing a gas containing water vapor into the fixed-bed reaction tube to treat the above-mentioned molecular sieve, wherein the water vapor content is 5%-100%, and the rest of the gas is one of air, N2, He and Ar;

[0040] c) after 2-10 hours of water vapor treatment, switching to air, and cooling to obtain the catalyst.

[0041] Optionally, the high temperature steam treatment temperature is selected from any of 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, 750°C, 775°C, 800°C, 825°C, and 850°C or a range between any two of these values.

[0042] Optionally, the high temperature steam treatment time can be independently selected from any of 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, and 10 hours or a range between any two of these values.

[0043] Optionally, the high temperature steam treatment steam content can be independently selected from any of 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% or a range between any two of these values.

[0044] Optionally, the silanization treatment method is a silanization modification using chemical vapor deposition, comprising the following steps:

[0045] (1) The calcined metal modified molecular sieve is placed in a fixed bed reactor, and is pretreated with nitrogen at 400-550°C, and the silanization modification temperature is adjusted to 300-600°C;

[0046] (2) Silanization reagent is continuously fed into the reactor in step (1), and nitrogen is used as the carrier gas for silanization;

[0047] (3) After a period of treatment, the feeding of silanization reagent is stopped, the reactor is re-heated to above 400°C, and nitrogen is switched to air for calcination.

[0048] Preferably, the silanization reagent is selected from at least one of the compounds of Formula I;

[0049]

[0050] wherein R1, R2, R3, and R4 are each independently selected from one of C 1-4 alkyl, halogen, C 1-4 alkoxy, or hydrogen.

[0051] Optionally, at most one of R1, R2, R3, and R4 is a C

[0052] alkyl or alkoxy group having a number of C greater than 2.

[0053] Optionally, the silanization modification temperature can be independently selected from any value or range between any two values of 300 °C, 325 °C, 350 °C, 375 °C, 400 °C, 425 °C, 450 °C, 475 °C, 500 °C, 525 °C, 550 °C, 575 °C, and 600 °C.

[0054] In a third aspect, the present application provides a method for preparing aromatic hydrocarbon by coupling cycloalkane and carbon dioxide, the method comprising the following steps: contacting, reacting cycloalkane, carbon dioxide and a catalyst to generate aromatic hydrocarbon; wherein the catalyst is selected from the catalysts described above or the catalysts prepared by the preparation method described above.

[0055] Optionally, the cycloalkane is selected from at least one of cyclohexane, methylcyclohexane and dimethylcyclohexane.

[0056] Optionally, the reaction is carried out in a reactor; the reactor is selected from a fluidized bed reactor, a fixed bed reactor or a moving bed reactor.

[0057] Optionally, the reaction conditions include: the reaction pressure is 0.1-4 MPa (preferably normal pressure), the reaction temperature is 400-650 °C, the mass space velocity of cycloalkane is 1-8 h -1 , the mass space velocity of carbon dioxide is 1-8 h -1 , and the mass ratio of cycloalkane to carbon dioxide is 1:8-8:1.

[0058] Optionally, the reaction temperature is selected from any value or range between any two values of 400 °C, 425 °C, 450 °C, 475 °C, 500 °C, 525 °C, 550 °C, 575 °C, 600 °C, 625 °C and 650 °C.

[0059] Optionally, the reaction pressure is selected from any value or range between any two values of 0.1 MPa, 0.2 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa and 4.0 MPa.

[0060] Optionally, the mass space velocity of cycloalkane is selected from 1 h -1 , 1.5 h -1 , 2 h -1 , 2.5 h -1 , 3.0 h -1 , 3.5 h -1 , 4.0 h -1 , 4.5 h -1 , 5.0 h -1 , 5.5 h -1 , 6.0 h -1 , 6.5 h -1 , 7.0 h-1 , 7.5 h -1 , and 8 h -1 , or any range between any two of the listed values.

[0061] Optionally, the mass hourly space velocity of the carbon dioxide is selected from any value or any range between any two of the listed values of 1 h -1 , 1.5 h -1 , 2 h -1 , 2.5 h -1 , 3.0 h -1 , 3.5 h -1 , 4.0 h -1 , 4.5 h -1 , 5.0 h -1 , 5.5 h -1 , 6.0 h -1 , 6.5 h -1 , 7.0 h -1 , 7.5 h -1 , and 8 h -1 .

[0062] Optionally, the mass ratio of the cycloalkane and carbon dioxide can be independently selected from any value or any range between any two of the listed values of 1:8, 2:8, 4:8, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, and 8:1.

[0063] Compared with the prior art, the present application has the following beneficial effects:

[0064] 1) The present application provides a new method for coupling production of aromatic hydrocarbons from cycloalkanes and carbon dioxide, which promotes the utilization and conversion of carbon dioxide and overcomes the limitation of limited hydrogen resources in traditional carbon dioxide hydrogenation technology.

[0065] 2) The present application provides a metal-modified molecular sieve catalyst suitable for the above coupling reaction, the metal component provides a cycloalkane dehydrogenation and carbon dioxide activation center, the molecular sieve channel structure is suitable for the generation and diffusion of aromatic hydrocarbons, and the molecular sieve component provides an acid center to catalyze isomerization and aromatization reactions.

[0066] 3) The present application adjusts the acid center in the molecular sieve component through a post-treatment method, which is beneficial to inhibit the occurrence of carbon deposition reaction and prolong the service life of the catalyst.

[0067] 4) The present application catalyzes the coupling reaction of cycloalkanes and carbon dioxide with the metal-modified molecular sieve catalyst, and the selectivity of aromatic hydrocarbons is as high as 90% or more, and the carbon dioxide conversion rate is 20% or more. DETAILED DESCRIPTION

[0068] The application will be further described in connection with the specific embodiments. The following description is only a few embodiments of the application, and does not limit the application in any form. Although the preferred embodiments are disclosed as follows, they are not intended to limit the application. Any skilled person in the art can make some changes or modifications to the disclosed technical contents without departing from the scope of the technical solutions of the application, and the equivalent embodiments are also included in the scope of the technical solutions.

[0069] Unless otherwise specified, the raw materials in the embodiments of the application are purchased through commercial channels and directly used without any special treatment.

[0070] Unless otherwise specified, the analysis methods in the embodiments all use the conventional settings of instruments or equipment and conventional analysis methods.

[0071] In the embodiments of the application, only the hydrocarbon products of the coupling reaction of naphthenes and carbon dioxide are listed, and other products except hydrocarbons are not listed.

[0072] Example 1 Preparation of Zn-modified ZSM-5 molecular sieve catalyst

[0073] In this embodiment, 20 g of commercial H-ZSM-5 molecular sieve with Si / Al of 17 is mixed with 200 ml of zinc nitrate solution with a molar concentration of 0.5 mol / ml, and stirred uniformly at 80℃ for 4 hours. Then, the mixture is washed with deionized water for three times, dried at 120℃ for 12 hours, and then calcined at 500℃ for 6 hours to obtain Zn-ZSM-5 molecular sieve.

[0074] 5 g of Zn-ZSM-5 molecular sieve is programmed to 750℃ under air atmosphere, and calcined for 8 hours to obtain Zn-ZSM-5-T catalyst.

[0075] 5 g of Zn-ZSM-5 molecular sieve is placed in a fixed bed reactor, programmed to 750℃ under air atmosphere, switched to pure water vapor atmosphere, and treated for 4 hours at a water amount of 0.1 g / min. Then, the air atmosphere is switched to room temperature to obtain Zn-ZSM-5-S catalyst.

[0076] 5 g of Zn-ZSM-5 molecular sieve is placed in a fixed bed reactor, programmed to 750℃ under air atmosphere, and calcined for 8 hours to obtain Zn-ZSM-5-T catalyst. -1 After 2 hours of treatment, the trimethylchlorosilane feeding is stopped, and the reactor is purged with nitrogen for 2 hours. Then, the temperature is increased to 450℃, and switched to air calcination for 6 hours to obtain Zn-ZSM-5-Si catalyst.

[0077] Example 2 Preparation of Cu-modified ZSM-5 molecular sieve catalyst

[0078] In this example, a commercial H-ZSM-5 molecular sieve with Si / Al of 27 was used. 20 g of the H-ZSM-5 molecular sieve was mixed with 160 ml of a copper nitrate solution with a molar concentration of 0.8 mol / ml, and stirred uniformly at 90°C for 3 hours. The mixture was washed with deionized water three times, dried at 100°C for 12 hours, and then calcined at 550°C for 6 hours to obtain a Cu-ZSM-5 molecular sieve.

[0079] 5 g of the Cu-ZSM-5 molecular sieve was calcined at 700°C for 12 hours under an air atmosphere to obtain a Cu-ZSM-5-T catalyst.

[0080] 5 g of the Cu-ZSM-5 molecular sieve was placed in a fixed bed reactor, and programmed to increase the temperature to 700°C under an air atmosphere. The atmosphere was switched to 50% steam and 50% nitrogen, and the water amount was 0.15 g / min. After 6 hours of treatment, the atmosphere was switched to air, and the temperature was decreased to room temperature to obtain a Cu-ZSM-5-S catalyst.

[0081] 5 g of the Cu-ZSM-5 molecular sieve was placed in a fixed bed reactor, and programmed to increase the temperature to 500°C under a nitrogen atmosphere. After 1 hour of pretreatment, the temperature was increased to 550°C. Silicon tetrachloride was introduced into the reactor, and the mass space velocity of the silicon tetrachloride was 0.15 h -1 After 4 hours of treatment, the silicon tetrachloride feeding was stopped, and the reactor was purged with nitrogen for 2 hours. The atmosphere was switched to air calcination for 6 hours to obtain a Cu-ZSM-5-Si catalyst.

[0082] Example 3 Preparation of Zn-modified ZSM-11 molecular sieve catalyst

[0083] In this example, a commercial H-ZSM-11 molecular sieve with Si / Al of 22 was used. 20 g of the H-ZSM-11 molecular sieve was mixed with 100 ml of a zinc nitrate solution with a molar concentration of 0.6 mol / ml, and stirred uniformly at 85°C for 5 hours. The mixture was washed with deionized water three times, dried at 110°C for 12 hours, and then calcined at 500°C for 8 hours to obtain a Zn-ZSM-11 molecular sieve.

[0084] 5 g of the Zn-ZSM-11 molecular sieve was calcined at 800°C for 6 hours under an air atmosphere to obtain a Zn-ZSM-11-T catalyst.

[0085] The 5 g of Zn-ZSM-11 molecular sieve was placed in a fixed bed reactor, and programmed to heat to 750°C under an air atmosphere, switched to an atmosphere of 75% water vapor and 25% nitrogen, with a water amount of 0.2 g / min, treated for 5 hours, then switched to an air atmosphere, and reduced to room temperature to obtain a Zn-ZSM-11-S catalyst.

[0086] The 5 g of Zn-ZSM-11 molecular sieve was placed in a fixed bed reactor, and programmed to heat to 550°C under a nitrogen atmosphere, pretreated for 1 hour, reduced to 500°C, and trimethylchlorosilane was fed into the reactor, with a trimethylchlorosilane mass hourly space velocity of 0.2 h -1 . After treating for 3 hours, the trimethylchlorosilane feeding was stopped, purged with nitrogen for 4 hours, switched to air calcination for 6 hours, and a Zn-ZSM-11-Si catalyst was obtained.

[0087] Preparation of a Ga modified MOR molecular sieve catalyst

[0088] In this example, a commercial H-MOR molecular sieve with a Si / Al of 10 was used. 20 g of H-ZSM-11 molecular sieve was mixed with 80 ml of a gallium nitrate solution with a molar concentration of 1.0 mol / ml, and stirred uniformly at 70°C for 6 hours, washed with deionized water three times, dried at 100°C for 12 hours, and then calcined at 550°C for 8 hours to obtain a Ga-MOR molecular sieve.

[0089] The 5 g of Ga-MOR molecular sieve was placed in a fixed bed reactor, and programmed to heat to 700°C under an air atmosphere, and calcined for 8 hours to obtain a Ga-MOR-T catalyst.

[0090] The 5 g of Ga-MOR molecular sieve was placed in a fixed bed reactor, and programmed to heat to 750°C under an air atmosphere, switched to a pure water vapor atmosphere, with a water amount of 0.2 g / min, treated for 4 hours, then switched to an air atmosphere, and reduced to room temperature to obtain a Ga-MOR-S catalyst.

[0091] The 5 g of Ga-MOR molecular sieve was placed in a fixed bed reactor, and programmed to heat to 550°C under a nitrogen atmosphere, pretreated for 1 hour, and trimethyl-methoxysilane was fed into the reactor, with a trimethyl-methoxysilane mass hourly space velocity of 0.1 h -1 . After treating for 4 hours, the trimethyl-methoxysilane feeding was stopped, purged with nitrogen for 6 hours, switched to air calcination for 6 hours, and a Ga-MOR-Si catalyst was obtained.

[0092] Preparation of a Cu modified MCM-22 molecular sieve catalyst

[0093] The commercial H-MCM-22 molecular sieve with Si / Al of 11 was used in this example. 20 g of H-MCM-22 molecular sieve was mixed with 60 ml of copper nitrate solution with a molar concentration of 0.4 mol / ml, and stirred uniformly at 80°C for 6 hours. The mixture was washed with deionized water for three times, dried at 120°C for 12 hours, and then calcined at 550°C for 6 hours to obtain Cu-MCM-22 molecular sieve.

[0094] 5 g of Cu-MCM-22 molecular sieve was calcined under air atmosphere by programmed temperature rising to 750°C for 9 hours to obtain Cu-MCM-22-T catalyst.

[0095] 5 g of Cu-MCM-22 molecular sieve was placed in a fixed bed reactor, and programmed temperature rising was performed under air atmosphere to 760°C. The atmosphere was switched to 50% steam and 50% nitrogen, and the water amount was 0.2 g / min. After 4 hours of treatment, the atmosphere was switched to air, and the temperature was lowered to room temperature to obtain Cu-MCM-22-S catalyst.

[0096] 5 g of Cu-MCM-22 molecular sieve was placed in a fixed bed reactor, and programmed temperature rising was performed under nitrogen atmosphere to 500°C. After 1 hour of pretreatment, the temperature was lowered to 400°C. Trimethylchlorosilane was fed into the reactor, and the mass space velocity of trimethylchlorosilane was 0.1 h -1 After 2 hours of treatment, the feeding of trimethylchlorosilane was stopped, the temperature was raised to 550°C, and the reactor was purged with nitrogen for 4 hours. The atmosphere was switched to air calcination for 6 hours to obtain Cu-MCM-22-Si catalyst.

[0097] Example 6 Reaction evaluation of Zn-modified ZSM-5 molecular sieve catalyst

[0098] The Zn-modified ZSM-5 molecular sieve catalyst prepared in Example 1 was evaluated for catalyzing the coupling reaction of cyclohexane and carbon dioxide in a fixed bed reactor, and the steps were as follows:

[0099] 2 g of catalyst was loaded in a fixed bed reactor, and pretreated at 550°C for 1 hour under nitrogen atmosphere. The temperature was lowered to 500°C for reaction. Cyclohexane was fed by a feeding pump, and the mass flow rate of carbon dioxide was controlled by a mass flow meter. The mass ratio of cyclohexane to carbon dioxide in the raw material was 1:2, the mass space velocity of cyclohexane was 1.0 h -1 , the mass space velocity of carbon dioxide was 2.0 h -1 , and the reaction pressure was atmospheric pressure. The reaction results were analyzed by a gas chromatograph with a model of Agilent 7890B. The sample was taken for analysis at 30 min of reaction. The reaction results are shown in Table 1.

[0100] Table 1 Reaction performance of catalyst in Example 1

[0101]

[0102] Reaction evaluation of Cu-modified ZSM-5 catalyst

[0103] The Cu-modified ZSM-5 catalyst prepared in Example 2 was evaluated in a fixed bed reactor for catalyzing the coupling reaction of methylcyclohexane with carbon dioxide, with the following steps:

[0104] 2 g of catalyst was loaded in a fixed bed reactor, pretreated at 550°C for 1 h under nitrogen atmosphere, and cooled to 525°C for reaction. Methylcyclohexane was fed by a feed pump, and carbon dioxide was controlled by a mass flow meter. The mass ratio of methylcyclohexane to carbon dioxide in the feed was 1:1, the mass space velocity of methylcyclohexane was 1.0 h -1 , and the mass space velocity of carbon dioxide was 1.0 h -1 . The reaction pressure was 1.0 MPa. The reaction results were analyzed by a gas chromatograph of Agilent 7890B. The sample was taken for analysis at 30 min. The reaction results are shown in Table 2.

[0105] Table 2 Reaction performance of the catalyst of Example 2

[0106]

[0107] Reaction evaluation of Zn-modified ZSM-11 catalyst

[0108] The Zn-modified ZSM-5 catalyst prepared in Example 3 was evaluated in a fixed bed reactor for catalyzing the coupling reaction of cyclohexane with carbon dioxide, with the following steps: 2 g of catalyst was loaded in a fixed bed reactor, pretreated at 550°C for 1 h under nitrogen atmosphere, and cooled to 475°C for reaction. Cyclohexane was fed by a feed pump, and carbon dioxide was controlled by a mass flow meter. The mass ratio of cyclohexane to carbon dioxide in the feed was 1:4, the mass space velocity of cyclohexane was 1.0 h -1 , and the mass space velocity of carbon dioxide was 4.0 h -1 . The reaction pressure was atmospheric pressure. The reaction results were analyzed by a gas chromatograph of Agilent 7890B. The sample was taken for analysis at 30 min. The reaction results are shown in Table 3.

[0109] Table 3 Reaction performance of the catalyst of Example 3

[0110]

[0111] Reaction evaluation of Ga-modified MOR catalyst

[0112] The Ga-modified MOR catalyst prepared in Example 4 was evaluated in a fixed bed reactor for catalyzing the coupling reaction of dimethylcyclohexane with carbon dioxide, with the following steps:

[0113] 2 g catalyst was packed in a fixed bed reactor, pretreated for 1 hour under nitrogen atmosphere at 550℃, and then cooled to 500℃ for reaction. Cyclohexane was fed by a feed pump, and carbon dioxide was controlled by a mass flow meter. The mass ratio of cyclohexane to carbon dioxide in the raw material was 1:5, the mass space velocity of cyclohexane was 1.0 h-1, and the mass space velocity of carbon dioxide was 5.0 h-1. The reaction pressure was normal pressure. The reaction results were analyzed by a gas chromatograph of Agilent 7890B. The sample was taken for analysis at 30 min of reaction. The reaction results are shown in Table 5. -1 -1 -1 -1 The reaction results were analyzed by a gas chromatograph of Agilent 7890B. The sample was taken for analysis at 30 min of reaction. The reaction results are shown in Table 4.

[0114] Table 4 Reaction performance of the catalyst of Example 4

[0115]

[0116] Reaction evaluation of Cu-modified MCM-22 molecular sieve catalyst

[0117] The Cu-modified MCM-22 molecular sieve catalyst prepared in Example 5 was evaluated for catalyzing the reaction of cyclohexane coupling with carbon dioxide in a fixed bed reactor, and the steps were as follows:

[0118] 2 g catalyst was packed in a fixed bed reactor, pretreated for 1 hour under nitrogen atmosphere at 550℃, and then cooled to 500℃ for reaction. Cyclohexane was fed by a feed pump, and carbon dioxide was controlled by a mass flow meter. The mass ratio of cyclohexane to carbon dioxide in the raw material was 1:5, the mass space velocity of cyclohexane was 1.0 h-1, and the mass space velocity of carbon dioxide was 5.0 h-1. The reaction pressure was normal pressure. The reaction results were analyzed by a gas chromatograph of Agilent 7890B. The sample was taken for analysis at 30 min of reaction. The reaction results are shown in Table 5.

[0119] Table 5 Reaction performance of the catalyst of Example 5

[0120]

[0121] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the technical solution of the present application, which are equivalent to equivalent embodiments and belong to the scope of the technical solution.​​​

Claims

1. A metal-modified molecular sieve catalyst characterized in that, The catalyst is a supported metal molecular sieve after the metal component is supported on the molecular sieve and then modified by post-treatment; The molecular sieve in the catalyst is at least one selected from H-ZSM-5, H-Beta, H-ZSM-35, H-MOR, H-MCM-22, H-ZSM-11 and H-ZSM-22 molecular sieves; The metal in the catalyst is supported on the molecular sieve by ion exchange and / or impregnation; The post-treatment modification of the catalyst is at least one selected from heat treatment, water vapor treatment and silanization treatment.

2. The metal-modified molecular sieve catalyst of claim 1, wherein, The metal in the catalyst is at least one selected from Zn, Cu, Ga, Cr, Fe, Mo, Ir and La.

3. The metal-modified molecular sieve catalyst of claim 1, wherein the metal is selected from the group consisting of copper, zinc, iron, cobalt, nickel, manganese, chromium, molybdenum, tungsten, vanadium, and combinations thereof. The loading amount of the metal component in the catalyst is 0.5-5.0 wt.% based on the total mass of the catalyst.

4. A process for the preparation of the metal-modified molecular sieve catalyst according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1: mixing a molecular sieve and an aqueous solution of a metal soluble salt to obtain a product I of a molecular sieve loaded with metal by ion exchange and / or impregnation; S2: drying and calcining the product I of the molecular sieve loaded with metal to obtain a calcined product II; S3: modifying the calcined product II in step S2 by post-treatment to obtain the metal modified molecular sieve catalyst.

5. The preparation method according to claim 4, characterized in that, The metal soluble salt in step S1 is at least one selected from metal nitrate, carbonate, chloride and acetylacetone salt; Preferably, the liquid-solid phase mass ratio of the aqueous solution of the metal soluble salt to the molecular sieve is (10-1):1; Preferably, the ion exchange temperature is 50-100℃, and the ion exchange time is 1-10 hours; Preferably, the impregnation temperature is 25-70℃, and the impregnation time is 1-4 hours.

6. The preparation method according to claim 4, characterized in that, In step S2, the drying process comprises drying at a temperature of 80-150℃ in an air or nitrogen atmosphere; Preferably, the calcination process comprises calcination at a temperature of 500-700℃ in an air or nitrogen atmosphere.

7. The production method according to claim 6, wherein In step S3, the post-treatment modification is at least one selected from high-temperature heat treatment, high-temperature water vapor treatment and silanization; Preferably, the high-temperature heat treatment is calcination at a temperature of 600-800℃ in an air atmosphere, and the calcination time is 4-12 hours; Preferably, the high-temperature water vapor treatment method comprises the following steps: a) loading the calcined metal modified molecular sieve into a fixed bed reactor, and passing dry air to heat to 600-850℃; b) passing a gas containing water vapor into the fixed bed reactor to treat the above-mentioned molecular sieve, wherein the water vapor content is 5%-100%, and the remaining gas is one of air, N2, He and Ar; c) after water vapor treatment for 2-10 hours, switching to air to cool down to obtain the catalyst.

8. The method for preparing a metal-modified molecular sieve catalyst according to claim 7, characterized by, The silanization treatment method is a silanization modification by chemical vapor deposition, comprising the following steps: (1) placing the calcined metal modified molecular sieve in a fixed bed reactor, and pre-treating at 400-550℃ with nitrogen, and adjusting the silanization modification temperature to 300-600℃; (2) continuously feeding silanization reagent into the reactor in step (1), using nitrogen as the carrier gas for silanization; (3) after a period of treatment, stopping the feeding of silanization reagent, re-warming the reactor to above 400℃, switching the nitrogen to air for calcination; Preferably, the silanization reagent is selected from at least one of the compounds of chemical formula I; wherein R1, R2, R3and R4are each independently selected from one of C 1-4 alkyl, halogen, C 1-4 alkoxy or hydrogen; Preferably, at most one of R1, R2, R3 and R4 is an alkyl or alkoxy group with a C number greater than 2; Preferably, the silanization reagent is selected from at least one of silicon tetrachloride, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylhydrogenosilane, dimethyldihydrogenosilane, and trimethylmonomethoxysilane.

9. A method for producing aromatic hydrocarbons by coupling of naphthenes and carbon dioxide, characterized by, The method comprises the following steps: contacting, reacting, cycloalkane, carbon dioxide and catalyst to generate aromatic hydrocarbon; The catalyst is selected from the catalysts of any one of claims 1-3 or the catalysts prepared by the preparation method of any one of claims 4-8.

10. The method for coupling naphthene and carbon dioxide to prepare aromatic hydrocarbon according to claim 9, characterized in that, The cycloalkane is selected from at least one of cyclohexane, methylcyclohexane and dimethylcyclohexane; Preferably, the reaction is carried out in a reactor; the reactor is selected from a fluidized bed reactor, a fixed bed reactor or a moving bed reactor; Preferably, the reaction conditions include: a reaction pressure of 0.1 to 4 MPa, a reaction temperature of 400 to 650°C, a mass space velocity of cyclohexane of 1 to 8 h -1 , and a mass space velocity of carbon dioxide of 1 to 8 h -1 . Preferably, the mass ratio of cycloalkane to carbon dioxide is 1:8-8:1.

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