Metal modified molecular sieve catalyst as well as preparation method and application thereof
By loading metal components onto molecular sieves and performing post-processing modification, a highly efficient metal-modified molecular sieve catalyst was prepared, which solved the problems of low conversion rate and poor stability of catalysts in the dehydrogenation of cycloalkanes to produce aromatics, and achieved efficient aromatics production and cost control.
Patent Information
- Application Number
- CN202410554773.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-06
- Publication Date
- 2025-11-07
AI Technical Summary
Existing catalysts for the dehydrogenation of cycloalkanes to produce aromatics suffer from low cycloalkane conversion rates, low aromatic yields, poor hydrothermal stability, easy loss of precious metals, and irreversible deactivation due to sintering.
A metal-modified molecular sieve catalyst was prepared by loading metal components onto the molecular sieve and performing post-treatment modifications, including Na+ ion exchange, high-temperature heat treatment, and high-temperature steam treatment, to produce a catalyst with high activity and stability.
It improved the conversion rate of cycloalkanes and the yield of aromatics, extended the catalyst life, reduced production costs, and significantly improved the stability of the catalyst.
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Figure CN120900693A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of petrochemical industry, and particularly relates to a metal-modified molecular sieve catalyst, a preparation method thereof and application thereof in a reaction of preparing aromatic hydrocarbon by dehydrogenation of naphthene. BACKGROUND
[0002] Aromatic hydrocarbon is a basic product of modern petrochemical industry and one of the most important basic raw materials in chemical production, and plays a basic supporting role in the chemical industry and the fine product industry downstream thereof. With the rapid and sustained growth of China's economy, China is currently the largest country in terms of demand for aromatic hydrocarbon, and the supply of aromatic hydrocarbon products cannot meet the demand. Aromatic hydrocarbon is mainly produced by catalytic reforming of naphtha, which accounts for about 70% of the aromatic hydrocarbon production. The raw material containing more naphthene is a good reforming raw material, but it is difficult to produce aromatic hydrocarbon by catalytic reforming for straight-chain alkanes or light alkanes with C<6. Naphthene is a bulk chemical, but its added value is low. Preparing high-value-added aromatic hydrocarbon by dehydrogenation of naphthene is a valuable path.
[0003] The reforming process uses a Pt / Al2O3 catalyst. The noble metal Pt active center mainly catalyzes dehydrogenation and hydrogenation reactions, so it can efficiently catalyze the dehydrogenation of naphthene to produce aromatic hydrocarbon. At the same time, the Al2O3 carrier in the catalyst has strong acidity, and carbon is easily deposited on the surface of the catalyst, causing the catalyst to deactivate quickly. Therefore, it is urgent to prepare a low-cost catalyst and improve the activity and stability of the catalyst for the preparation of aromatic hydrocarbon by dehydrogenation of naphthene.
[0004] Molecular sieves play an important role in petroleum chemical processes as shape-selective catalysts due to their unique active sites and pore structures. The shape-selective catalytic performance of molecular sieves is also affected by the surface active center and pore structure. Some molecular sieves have pore sizes similar to those of aromatic hydrocarbons, which can produce aromatic hydrocarbons with high selectivity. The introduction of metals into molecular sieves can catalyze dehydrogenation reactions, and the combination of acid centers in molecular sieves can catalyze isomerization and aromatization reactions. In theory, adjusting the appropriate metal centers and acid centers of the metal-modified molecular sieve catalyst can efficiently catalyze the dehydrogenation of naphthene to produce aromatic hydrocarbon. However, these metals are easily lost and sintered during aromatization, causing irreversible deactivation of the catalyst. SUMMARY
[0005] In view of this, the present application provides a metal-modified molecular sieve catalyst, a preparation method thereof and application thereof, and the main purpose is to solve the technical problems of low conversion rate of naphthene, low yield of aromatic hydrocarbon and poor hydrothermal stability in the catalysis of the catalyst in the preparation of aromatic hydrocarbon from naphthene and carbon dioxide.
[0006] In one aspect, the present application provides a metal-modified molecular sieve catalyst, which is a supported metal molecular sieve obtained by loading a metal component on a molecular sieve and then modifying it by post-treatment;
[0007] The metal component in the catalyst is at least one of rare earth metals, copper, cobalt, zinc, gallium, iridium, and iron.
[0008] The post-treatment modification is selected from Na + The post-treatment modification is selected from Na
[0009] The metal-modified molecular sieve catalyst provided by the present application not only has low cost relative to a noble metal Pt catalyst, but also has adjustable metal dehydrogenation centers and acid centers, and when used as a catalyst for preparing aromatic hydrocarbons from naphthenes, has high naphthene conversion rate, aromatic hydrocarbon yield, and hydrothermal stability.
[0010] Optionally, the metal component is at least one of rare earth metals, copper, cobalt, zinc, gallium, iridium, and iron.
[0011] Optionally, the content of the metal component in the catalyst is 0.5-5.0 wt.%, based on the total mass of the catalyst.
[0012] Optionally, the content of the metal component in the catalyst can be independently selected from any value or any range between two values in 0.5 wt.%, 1.0 wt.%, 2.0 wt.%, 2.5 wt.%, 3.0 wt.%, 3.5 wt.%, 4.0 wt.%, 4.5 wt.%, and 5.0 wt.%.
[0013] Optionally, the metal component in the catalyst is loaded by one of ion exchange or impregnation.
[0014] In a second aspect, the present application provides a preparation method of the catalyst, comprising the following steps:
[0015] S1: mixing and contacting a metal-soluble salt solution with a molecular sieve to obtain a molecular sieve catalyst precursor;
[0016] S2: calcining the molecular sieve catalyst precursor in dry air to obtain a calcined product;
[0017] S3: post-treatment modification of the calcined product to obtain the metal-modified molecular sieve catalyst.
[0018] The present application loads metal in a molecular sieve by ion exchange, impregnation, or the like, and then performs post-treatment modification on the metal-loaded molecular sieve; the preparation process is simple, the catalyst has good performance, and the problems of high catalyst cost and easy loss and sintering of the metal component are solved.
[0019] The soluble salt of the metal component is dissolved in a proper amount of deionized water in step S1 of the application, and the solution containing the metal is contacted with the synthesized molecular sieve. To obtain a proper metal content, step S1 can be repeated multiple times to obtain a molecular sieve precursor.
[0020] Optionally, step S1 can use one of the isometric impregnation and ion exchange methods.
[0021] In step S3, the post-treatment modification can use Na + one of ion synergistic exchange, high-temperature heat treatment, and high-temperature water vapor treatment.
[0022] Optionally, in step S1 of the preparation method of the metal-modified molecular sieve dehydrogenation catalyst, the soluble salt of the metal component is selected from one of the nitrate, carbonate, ammonium salt, and ethylene acetone salt corresponding to the metal component.
[0023] Optionally, in step 1) of the preparation method of the metal-modified molecular sieve dehydrogenation catalyst, when the isometric impregnation is used as the metal loading method, the impregnation temperature is room temperature to 50°C, and the impregnation time is 1 to 12 hours.
[0024] Optionally, the impregnation temperature is selected from any value or a range between any two values of 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C.
[0025] Optionally, the impregnation time is selected from any value or a range between any two values of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, and 12 hours.
[0026] Optionally, when ion exchange is used, the ion exchange temperature is 50 to 90°C, the ion exchange time is 1 to 6 hours, and the exchange times are 1 to 4 times.
[0027] Optionally, the ion exchange temperature is selected from any value or a range between any two values of 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C.
[0028] Optionally, the ion exchange time is selected from any value or a range between any two values of 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, and 6 hours.
[0029] Optionally, the ion exchange times can be independently selected from any value or a range between any two values of 1 time, 2 times, 3 times, and 4 times.
[0030] Optionally, in step S3, the post-treatment is Na+ In the ion synergic exchange, the preparation method comprises the following steps:
[0031] a) mixing the metal soluble salt, the Na soluble salt solution and the molecular sieve, and performing ion exchange, the ion exchange temperature being 50-90℃, the ion exchange time being 1-6 hours, the exchange times being 1-4 times, to obtain the molecular sieve catalyst precursor;
[0032] b) calcining the molecular sieve catalyst precursor in dry air, the temperature being 400-600℃, to obtain the metal modified molecular sieve catalyst.
[0033] Optionally, the Na ion exchange temperature is selected from any value or a range between any two values selected from the group consisting of 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ and 90℃.
[0034] Optionally, the ion exchange time is selected from any value or a range between any two values selected from the group consisting of 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours and 6 hours.
[0035] Optionally, the ion exchange times can be independently selected from any value or a range between any two values selected from the group consisting of 1 time, 2 times, 3 times and 4 times.
[0036] Optionally, in step S3, in the high-temperature heat treatment, the treatment condition is 600-800℃, calcination for 5-10 hours in a dry air atmosphere.
[0037] Optionally, the high-temperature heat treatment temperature is selected from any value or a range between any two values selected from the group consisting of 600℃, 625℃, 650℃, 675℃, 700℃, 725℃, 750℃, 775℃ and 800℃.
[0038] Optionally, the high-temperature heat treatment calcination time is selected from any value or a range between any two values selected from the group consisting of 5 hours, 5.5 hours, 6.0 hours, 6.5 hours, 7.0 hours, 7.5 hours, 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours and 10 hours.
[0039] Optionally, in the high-temperature steam treatment, the specific steps are as follows:
[0040] a) loading the metal modified molecular sieve obtained in step 2) into a fixed bed reaction tube, and passing dry air to warm up to 600-850℃, the air flow rate being 20-50 mL / min;
[0041] b) treating the above mentioned molecular sieve with a gas containing water vapor, wherein the water vapor content is in the range of 5 to 100% and the remaining gas component is an inert atmosphere selected from the group consisting of air, N2, He, Ar;
[0042] c) after 2 to 10 hours of treatment, switching to air and cooling down, thereby obtaining the desired catalyst;
[0043] Optionally, the high temperature water vapor treatment temperature is selected from any of the values 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.
[0044] Optionally, the high temperature water vapor treatment time is selected from any of the values 2 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, 5.5 hours, 6.0 hours, 6.5 hours, 7.0 hours, 7.5 hours, 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours and 10 hours or a range between any two of these values.
[0045] Optionally, the high temperature water vapor treatment air flow rate is selected from any of the values 20 ml / min, 25 ml / min, 30 ml / min, 35 ml / min, 40 ml / min, 45 ml / min and 50 ml / min or a range between any two of these values.
[0046] Optionally, the high temperature water vapor treatment water vapor content is selected from any of the values 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% or a range between any two of these values.
[0047] In a third aspect, the present application provides a method for preparing aromatic hydrocarbon by dehydrogenation of naphthene, which uses the above-mentioned metal-modified molecular sieve catalyst to catalyze the dehydrogenation of naphthene to prepare aromatic hydrocarbon, wherein the mass space velocity of naphthene is 2.0-6.0 h -1 , the reaction temperature is 400-600 °C, and the reaction pressure is normal pressure.
[0048] Optionally, the mass space velocity of naphthene is selected from any of the values 2.0 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 or a range between any two of these values.
[0049] Optionally, the reaction temperature of the naphthene dehydrogenation to aromatics is selected from any value or a range between any two values of 400℃, 425℃, 450℃, 475℃, 500℃, 525℃, 550℃, 575℃ and 600℃.
[0050] Compared with the prior art, the present application has the following beneficial effects:
[0051] 1) The catalyst provided by the present application uses a molecular sieve with ten-membered ring pores as a carrier, the size of the ten-membered ring pores is close to the size of the aromatic molecules, which is conducive to shape-selective generation of aromatic hydrocarbons; the molecular sieve carrier provides a site for the metal components, which is conducive to stable dispersion of the metal components; the acid centers in the molecular sieve can be adjusted, which is conducive to inhibition of the occurrence of carbon deposition reactions and prolongation of the service life of the catalyst.
[0052] 2) The catalyst provided by the present application uses a non-noble metal, and the molecular sieve carrier is conducive to dispersion of the metal active components, which can effectively reduce the loading amount of the metal components and reduce the production cost of the catalyst.
[0053] 3) The catalyst provided by the present application regulates the distribution of acid centers through post-processing, only a small amount of acid centers are left to catalyze isomerization and aromatization reactions, and at the same time, the occurrence of carbon deposition reactions is inhibited.
[0054] 4) The catalyst provided by the present application is applied in the reaction of naphthene dehydrogenation to aromatics, the yield of aromatic hydrocarbons reaches more than 95%, and the reaction has high stability and industrial application value. BRIEF DESCRIPTION OF DRAWINGS
[0055] Figure 1 The figure is a comparison chart of the reaction performance of the metal-modified molecular sieve catalyst in the preparation of aromatic hydrocarbons from cyclohexane in the embodiments of the present application. DETAILED DESCRIPTION
[0056] The present application will be further described below in combination with specific embodiments. The following description 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 as follows with a preferred embodiment, however, it is not intended to limit the present application, and 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.
[0057] Unless otherwise specified, the raw materials in the embodiments of the present application are purchased through commercial channels and directly used without any special treatment.
[0058] In the following examples, the preparation of ZSM-5 molecular sieve is a mature technology, the Si / Al of the used ZSM-5 molecular sieve is 27; the preparation of MCM-22 molecular sieve is a mature technology, the Si / Al of the used MCM-22 molecular sieve is 22; the preparation of L-type molecular sieve is a mature technology, the Si / Al of the used L-type molecular sieve is 10.
[0059] Example 1
[0060] Example 1 uses ZSM-5 molecular sieve with Si / Al of 27 as precursor, and the specific preparation process is as follows: 2.2 g of zinc nitrate is dissolved in 6 ml of deionized water to prepare a zinc nitrate solution. The zinc nitrate solution and 12 g of ZSM-5 molecular sieve are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 2 hours, drying at 130°C for 2 hours, and then calcining at 550°C for 6 hours, Zn / ZSM-5 molecular sieve is obtained. 0.5 g of sodium nitrate is dissolved in 1.5 ml of deionized water to prepare a sodium nitrate solution. The sodium nitrate solution and 3 g of Zn / ZSM-5 molecular sieve in Example 1 are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 2 hours, drying at 130°C for 2 hours, and then calcining at 550°C for 6 hours, the molecular sieve catalyst Zn / ZSM-5-Na is obtained.
[0061] Example 2
[0062] The preparation process of this example 2 is the same as that of example 1, except that 3 g of Zn / ZSM-5 molecular sieve obtained by calcining at 550°C for 6 hours in example 1 is placed in a muffle furnace, and the temperature is programmed to 750°C for calcination for 6 hours to obtain Zn / ZSM-5-T molecular sieve.
[0063] Example 3
[0064] The preparation process of this example 3 is the same as that of example 1, except that 3 g of Zn / ZSM-5 molecular sieve obtained by calcining at 550°C for 6 hours in example 1 is placed in a fixed bed reaction tube, and the temperature is programmed to 750°C under dry air, then switched to pure water vapor atmosphere, with a water amount of 0.2 g / min, treated for 4 hours, then switched to air atmosphere, and cooled to room temperature to obtain Zn / ZSM-5-S molecular sieve.
[0065] Example 4
[0066] The preparation process of this embodiment 4 is as follows: 2.0 g of copper nitrate pentahydrate is dissolved in 6 ml of deionized water to prepare a copper nitrate solution. The copper nitrate solution and 12 g of ZSM-5 molecular sieve are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 4 hours, drying at 110°C for 2 hours, and then calcining at 550°C for 6 hours, a Cu / ZSM-5 molecular sieve is obtained. 0.6 g of sodium nitrate is dissolved in 1.5 ml of deionized water to prepare a sodium nitrate solution. The sodium nitrate solution and 3 g of the Cu / ZSM-5 molecular sieve of embodiment 4 are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 2 hours, drying at 110°C for 2 hours, and then calcining at 550°C for 6 hours, a molecular sieve catalyst Cu / ZSM-5-Na is obtained.
[0067] Embodiment 5
[0068] The preparation process of this embodiment 5 is the same as that of embodiment 4, except that 3 g of the Cu / ZSM-5 molecular sieve calcined at 550°C for 6 hours in embodiment 4 is placed in a fixed bed reaction tube, dried air is used, the temperature is programmed to 750°C, switched to a pure water vapor atmosphere, the water amount is 0.2 g / min, treated for 4 hours, then switched to an air atmosphere, and then reduced to room temperature to obtain a Cu / ZSM-5-T molecular sieve.
[0069] Embodiment 6
[0070] The preparation process of this embodiment 6 is the same as that of embodiment 4, except that 3 g of the Cu / ZSM-5 molecular sieve calcined at 550°C for 6 hours in embodiment 1 is placed in a fixed bed reaction tube, dried air is used, the temperature is programmed to 750°C, switched to a pure water vapor atmosphere, the water amount is 0.2 g / min, treated for 4 hours, then switched to an air atmosphere, and then reduced to room temperature to obtain a Cu / ZSM-5-S molecular sieve.
[0071] Embodiment 7
[0072] The preparation process of this embodiment 7 is as follows: 3.8 g of gallium nitrate is dissolved in 6 ml of deionized water to prepare a gallium nitrate solution. The gallium nitrate solution and 12 g of ZSM-5 molecular sieve are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 4 hours, drying at 120°C for 2 hours, and then calcining at 550°C for 6 hours, a Ga / ZSM-5 molecular sieve is obtained. 3 g of the Ga / ZSM-5 molecular sieve obtained in embodiment 7 is placed in a fixed bed reaction tube, dried air is used, the temperature is programmed to 750°C, switched to a pure water vapor atmosphere, the water amount is 0.2 g / min, treated for 4 hours, then switched to an air atmosphere, and then reduced to room temperature to obtain a Ga / ZSM-5-T molecular sieve.
[0073] Example 8
[0074] The preparation process of this example 8 is the same as example 7, except that 3 g of Ga / ZSM-5 zeolite obtained by calcining ZSM-5 zeolite with Si / Al of 27 at 550℃ for 6 hours is placed in a fixed bed reactor, and then the temperature is programmed to 750℃ under dry air, switched to pure water vapor atmosphere, and the water amount is 0.2 g / min. After treatment for 4 hours, the air atmosphere is switched, and the temperature is reduced to room temperature to obtain Ga / ZSM-5-S zeolite.
[0075] Comparative Example 1
[0076] In this comparative example 1, ZSM-5 zeolite with Si / Al of 27 is used as a precursor, and the specific preparation process is as follows: 2.2 g of zinc nitrate is dissolved in 6 ml of deionized water to prepare a zinc nitrate solution. The zinc nitrate solution and 12 g of ZSM-5 zeolite are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 2 hours, drying is performed at 130℃ for 2 hours, and then calcination is performed at 550℃ for 6 hours to obtain Zn / ZSM-5 zeolite.
[0077] Comparative Example 2
[0078] In this comparative example, ZSM-5 zeolite with Si / Al of 27 is used as a precursor, and the specific preparation process is as follows: 2.0 g of copper nitrate pentahydrate is dissolved in 6 ml of deionized water to prepare a copper nitrate solution. The copper nitrate solution and 12 g of ZSM-5 zeolite are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 4 hours, drying is performed at 110℃ for 2 hours, and then calcination is performed at 550℃ for 6 hours to obtain Cu / ZSM-5 zeolite.
[0079] Comparative Example 3
[0080] In this example, ZSM-5 zeolite with Si / Al of 27 is used as a precursor, and the specific preparation process is as follows: 3.8 g of gallium nitrate is dissolved in 6 ml of deionized water to prepare a gallium nitrate solution. The gallium nitrate solution and 12 g of ZSM-5 zeolite are uniformly mixed at room temperature, and the solid-liquid phase is fully fused. After standing at room temperature for 4 hours, drying is performed at 120℃ for 2 hours, and then calcination is performed at 550℃ for 6 hours to obtain Ga / ZSM-5 zeolite.
[0081] Characterization results of the zeolite catalysts in examples 1-8:
[0082] 1 H MAS NMR technology is an excellent means for characterizing acid centers in zeolites. In this application, 1 H MAS NMR technology is used to characterize the content of acid centers in the zeolite catalysts in the examples. The content of metal components in the zeolite catalysts in the examples is determined by XRF technology, and the characterization results are shown in Table 1.
[0083] The metal component content and the acid center content in the molecular sieve catalysts of Examples 1 to 8 are shown in Table 1.
[0084] Table 1
[0085]
[0086]
[0087] Example 9
[0088] Example 9 uses MCM-22 molecular sieve with Si / Al of 22 as a precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of zinc nitrate solution with a molar concentration of 0.5 mol / ml are uniformly mixed, stirred at 80°C for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120°C for 12 hours, then calcined at 550°C for 6 hours to obtain Zn-MCM-22 molecular sieve. 3 g of Zn-MCM-22 molecular sieve in Example 9 is placed in a muffle furnace, and the temperature is programmed to 800°C, and calcined for 8 hours to obtain Zn-MCM-22-T molecular sieve.
[0089] Example 10
[0090] The preparation process of this embodiment 10 is the same as that of Example 9, except that 3 g of Zn-MCM-22 molecular sieve in Example 9 is placed in a fixed bed reaction tube, and the temperature is programmed to 800°C under dry air, and switched to an atmosphere of 50% water vapor and 50% air, with a water amount of 0.1 g / min, treated for 6 hours, then switched to an air atmosphere, and reduced to room temperature to obtain Zn-MCM-22-S molecular sieve.
[0091] Example 11
[0092] Example 11 uses MCM-22 molecular sieve with Si / Al of 22 as a precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of copper nitrate solution with a molar concentration of 1.0 mol / ml are uniformly mixed, stirred at 80°C for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120°C for 12 hours, then calcined at 550°C for 6 hours to obtain Cu-MCM-22 molecular sieve. 3 g of Cu-MCM-22 molecular sieve in Example 9 is placed in a muffle furnace, and the temperature is programmed to 800°C, and calcined for 8 hours to obtain Cu-MCM-22-T molecular sieve.
[0093] Example 12
[0094] The preparation process of this example 12 is the same as example 11, except that 3 g of Cu-MCM-22 molecular sieve in example 11 is placed in a fixed bed reaction tube, and under dry air, the temperature is programmed to 800°C, and then switched to an atmosphere of 50% water vapor and 50% air, with a water amount of 0.1 g / min, and after 6 hours of treatment, switched to an air atmosphere, and then reduced to room temperature, to obtain Cu-MCM-22-S molecular sieve.
[0095] Example 13
[0096] This example 13 uses MCM-22 molecular sieve with Si / Al of 22 as a precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of cobalt nitrate solution with a molar concentration of 0.2 mol / ml are uniformly mixed, stirred at 80°C for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120°C for 12 hours, and then calcined at 550°C for 6 hours to obtain Co-MCM-22 molecular sieve, and 3 g of Co-MCM-22 molecular sieve in example 9 is placed in a muffle furnace, and the temperature is programmed to 800°C, and then calcined for 8 hours to obtain Co-MCM-22-T molecular sieve.
[0097] Example 14
[0098] The preparation process of this example 14 is the same as example 13, except that 3 g of Co-MCM-22 molecular sieve in example 13 is placed in a fixed bed reaction tube, and under dry air, the temperature is programmed to 800°C, and then switched to an atmosphere of 50% water vapor and 50% air, with a water amount of 0.1 g / min, and after 6 hours of treatment, switched to an air atmosphere, and then reduced to room temperature, to obtain Co-MCM-22-S molecular sieve.
[0099] Comparative Example 4
[0100] This comparative example 4 uses MCM-22 molecular sieve with Si / Al of 22 as a precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of zinc nitrate solution with a molar concentration of 0.5 mol / ml are uniformly mixed, stirred at 80°C for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120°C for 12 hours, and then calcined at 550°C for 6 hours to obtain Zn-MCM-22 molecular sieve.
[0101] Comparative Example 5
[0102] The comparative example 5 uses MCM-22 molecular sieve with Si / Al of 22 as precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of copper nitrate solution with a molar concentration of 1.0 mol / ml are uniformly mixed, stirred at 80℃ for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120℃ for 12 hours, and then calcined at 550℃ for 6 hours to obtain Cu-MCM-22 molecular sieve.
[0103] Comparative example 6
[0104] The comparative example 6 uses MCM-22 molecular sieve with Si / Al of 22 as precursor, and the specific preparation process is as follows: 12 g of MCM-22 molecular sieve and 100 ml of cobalt nitrate solution with a molar concentration of 0.2 mol / ml are uniformly mixed, stirred at 80℃ for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120℃ for 12 hours, and then calcined at 550℃ for 6 hours to obtain Co-MCM-22 molecular sieve.
[0105] Characterization results of the molecular sieve catalysts in the examples:
[0106] In the present application, 1 H MAS NMR technique is used to characterize the content of acid centers in the molecular sieve catalysts in the examples. XRF technique is used to determine the content of metal components in the molecular sieve catalysts in the examples. The characterization results are shown in Table 2.
[0107] The content of metal components and the content of acid centers in the molecular sieve catalysts in the examples 9-14 and the comparative examples are shown in Table 2.
[0108] Table 2
[0109]
[0110] Example 15
[0111] The example 15 uses L-type molecular sieve with Si / Al of 10 as precursor, and the specific preparation process is as follows: 12 g of L-type molecular sieve and 100 ml of zinc nitrate solution with a molar concentration of 0.8 mol / ml are uniformly mixed, stirred at 90℃ for 4 hours, washed with deionized water for three times, repeated ion exchange for three times, dried at 120℃ for 12 hours, and then calcined at 550℃ for 6 hours to obtain Zn-L molecular sieve. 3 g of Zn-L molecular sieve in the example 15 is placed in a muffle furnace, and the temperature is programmed to 750℃, and calcined for 12 hours to obtain Zn-L-T molecular sieve.
[0112] Example 16
[0113] The preparation process of Example 16 is the same as that of Example 15, except that 3g of Zn-L molecular sieve from Example 15 is placed in a fixed-bed reaction tube, heated to 800°C in dry air, then switched to a 25% water vapor and 75% air atmosphere, with a water flow rate of 0.15g / min. After 4 hours of treatment, the atmosphere is switched to air and cooled to room temperature to obtain Zn-LS molecular sieve.
[0114] Comparative Example 7
[0115] Comparative Example 7 uses an L-type molecular sieve with a Si / Al ratio of 10 as a precursor. The specific preparation process is as follows: 12g of L-type molecular sieve and 100ml of zinc nitrate solution with a molar concentration of 0.8mol / ml are mixed evenly, stirred at 90℃ for 4 hours, washed three times with deionized water, and the ion exchange is repeated three times. The mixture is dried at 120℃ for 12 hours and then calcined at 550℃ for 6 hours to obtain Zn-L molecular sieve.
[0116] Characterization results of the molecular sieve catalysts in the examples:
[0117] The present invention adopts 1 The content of acidic centers in the molecular sieve catalysts in the examples was characterized by ¹H MAS NMR. The content of metal components in the molecular sieve catalysts in the examples was determined by XRF. The characterization results are shown in Table 3.
[0118] The content of metal components and acidic centers in the molecular sieve catalysts of Examples 15-16 and the comparative examples are shown in Table 3.
[0119] Table 3
[0120]
[0121] Example 17
[0122] The metal-modified molecular sieve catalysts prepared in Examples 1-16 above were applied to the catalytic dehydrogenation of cycloalkanes to aromatics, with cyclohexane selected as the representative reactant. The steps are as follows: 1g of catalyst (20-40 mesh) was packed into a fixed-bed reactor and activated at 550°C for 1 hour under a nitrogen atmosphere. The temperature was then lowered to 500°C to prepare for the reaction. Cyclohexane was introduced using a feed pump at a mass hourly space velocity (WHSV) of 4.0 h⁻¹. -1 The reaction was carried out at atmospheric pressure, and samples were taken for analysis after 30 minutes. The composition of the reaction products was analyzed by Agilent 7890 gas chromatography. Reaction results included cyclohexane conversion and product distribution, such as... Figure 1 As shown.
[0123] Example 18
[0124] The Zn / ZSM-5-S molecular sieve catalyst prepared in Example 3 was evaluated for catalyzing the cyclohexane conversion reaction in a fixed bed reactor, and the procedure was as follows: 2 g of the catalyst was packed in a fixed bed reactor, pretreated at 550°C for 1 h under a nitrogen atmosphere, and the temperature was adjusted to the reaction temperature. Alternatively, the reaction temperature was 450, 500, 550, and 600°C, and cyclohexane was fed by a feed pump, and the mass space velocity of methylcyclohexane was 4.0 h-1, and the reaction pressure was normal pressure. The reaction results were analyzed by a gas chromatograph of Agilent 7890B type, and the sample was analyzed at 30 min of the reaction. The reaction results with the change of the reaction temperature are shown in Table 4. -1 The reaction results with the change of the reaction temperature are shown in Table 4.
[0125] Table 4 Reaction performance of the catalyst of Example 18
[0126]
[0127] 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 as above with the 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 above disclosed technical content without departing from the scope of the technical solution of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within 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 selected from one of ZSM-5, MCM-22 and L-type molecular sieve, or one of the multi-level pore or core-shell molecular sieve based thereon; The post-treatment modification is selected from Na + at least one of ion co-exchange, high temperature heat treatment, and high temperature water vapor treatment.
2. The catalyst according to claim 1, characterized in that, The metal in the catalyst is selected from at least one of rare earth metal, copper, cobalt, zinc, gallium, iridium and iron.
3. The catalyst of claim 1, wherein The metal content in the catalyst is 0.5-5.0 wt.%, based on the total mass of the catalyst.
4. The catalyst of claim 1, wherein The metal in the catalyst is supported on the molecular sieve by ion exchange and / or impregnation.
5. The production process according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1: mixing and contacting a metal soluble salt solution with a molecular sieve to obtain a molecular sieve catalyst precursor; S2: calcining the molecular sieve catalyst precursor in dry air to obtain a calcined product; S3: modifying the calcined product by post-treatment to obtain the metal-modified molecular sieve catalyst.
6. The method for preparing a metal-modified molecular sieve catalyst according to claim 5, characterized by, In step S1, the metal soluble salt solution and the molecular sieve are subjected to equal-volume impregnation and / or ion exchange to obtain the molecular sieve catalyst precursor. Preferably, in step S3, the post-treatment modification employs Na + at least one of ion co-exchange, high temperature heat treatment, and high temperature water vapor treatment.
7. The method for preparing the metal-modified molecular sieve catalyst according to claim 5, characterized in that, In step S1, the metal soluble salt is selected from any one of nitrate, carbonate, ammonium salt and ethylene acetone salt corresponding to the metal.
8. The method for preparing a metal-modified molecular sieve catalyst according to claim 6, characterized by, In step S1, the equal-volume impregnation process comprises: an impregnation temperature of 25-50℃ and an impregnation time of 1-12 hours. In step S1, the ion exchange process comprises: an ion exchange temperature of 50-90℃, an ion exchange time of 1-6 hours, and an exchange number of 1-4 times.
9. The method for preparing a metal-modified molecular sieve catalyst according to claim 6, characterized by, In step S3, the post-treatment is Na + In the ion co-exchange, the preparation method comprises the following steps: a) mixing the metal soluble salt, a Na soluble salt solution and a molecular sieve, and performing ion exchange at an ion exchange temperature of 50-90℃ for an ion exchange time of 1-6 hours and an exchange number of 1-4 times to obtain the molecular sieve catalyst precursor; b) calcining the molecular sieve catalyst precursor in dry air at a temperature of 400-600℃ to obtain the metal-modified molecular sieve catalyst; Preferably, the high-temperature heat treatment process comprises: a temperature of 600-800℃, a dry air atmosphere, and calcination for 5-10 hours; Preferably, the high-temperature water vapor treatment process comprises: a) loading the metal-modified molecular sieve obtained in step S3 into a fixed-bed reaction tube, passing dry air to warm up to 600-850℃, and an air flow rate of 20-50 ml / min; b) passing a gas containing water vapor to treat the molecular sieve, wherein the water vapor content is 5-100%, and the remaining gas components are inert atmosphere selected from one of air, N2, He and Ar; c) after treatment for 2-10 hours, switching to air to cool down to obtain the desired catalyst.
10. A process for the dehydrogenation of a cycloparaffin to an aromatic hydrocarbon, characterized in that, The catalyst prepared by any one of claims 1-4 or the catalyst prepared by any one of claims 5-9. The reaction conditions include: the mass space velocity of the cycloalkane is 2.0-6.0h -1 , the reaction temperature is 400-600 DEG C, and the reaction pressure is normal pressure.