A method for in-situ preparation of highly dispersed nickel-based molecular sieve catalysts

Abstract

The present invention provides a method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst. First, a silicon source and a metal precursor are mixed evenly, and after adjusting the pH value, aging treatment is carried out to obtain gel A; then a template agent and an aluminum source are mixed evenly to obtain gel B; after adding gel B into gel A and mixing evenly, the obtained initial gel C is subjected to crystallization, washing, drying, and calcination treatments to obtain the highly dispersed nickel-based molecular sieve catalyst. In the present invention, a metal precursor is introduced in-situ into the synthetic molecular sieve precursor gel, and by utilizing the interaction between the metal species and the molecular sieve precursor during the crystallization process, the high dispersion of nickel is achieved, the utilization rate of nickel and the anti-sintering ability are improved, and a new method for efficiently synthesizing the highly dispersed nickel-based molecular sieve catalyst is provided. The method provided by the present invention has a simple process flow, does not require additional water sources, and does not need to add ligands, surfactants, etc., avoids repeated drying and calcination operations, shortens the crystallization time, improves the synthesis yield, and greatly reduces the cost and energy consumption.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst synthesis and relates to a method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst. Background Art

[0002] Metals have exposed outer surfaces and unfilled d orbitals, and their ability to adsorb and activate reactants is relatively strong. Metal-based catalysts are widely used in the production processes of energy and bulk chemicals, such as hydroisomerization, catalytic reforming, biomass hydrodeoxygenation, dry reforming of methane with carbon dioxide, hydrogenation of carbon dioxide, etc. Common carriers of metal-based catalysts include silica, alumina, molecular sieve, carbon carriers, etc. Among them, molecular sieve has shape selectivity for reactants and products, a large specific surface area, adjustable acid properties, and good hydrothermal stability, and is often used as a catalyst carrier and can also provide acidic sites. In terms of metal active components, due to their strong catalytic activity, noble metals such as platinum, palladium, and rhodium have been widely used, but they have the problems of high price and easy poisoning and deactivation. Compared with noble metal-based catalysts, transition metal nickel has a lower preparation cost and toxicity resistance, and at the same time has good mechanical strength and thermal conductivity, and is commonly used as a catalyst for hydrogenation and dehydrogenation reactions and C1 chemistry reactions, etc. However, nickel-based catalysts have low low-temperature activity, and metal aggregation is extremely likely to occur during the high-temperature calcination and reduction process, and carbon deposition is likely to occur in C1 reactions, resulting in catalyst deactivation. Therefore, it is extremely important to develop a preparation method for highly dispersed nickel-based molecular sieve catalysts.

[0003] CN110368982A discloses a preparation method for a catalyst in which non-precious metals (Cu, Fe, Co, Ni) are loaded on Silicalite-1 molecular sieve. By using a hydrothermal one-step method with ethanolamine or ethylenediamine as a ligand, due to the protection of the ligand and the confinement effect of the molecular sieve pores, a catalyst with high metal dispersion is obtained, and this catalyst shows good activity and ultra-high single-product selectivity in the solvent-free liquid-phase oxidation reaction of toluene. CN103934040B discloses a catalyst preparation method in which an organic compound containing a carboxyl group or an amino group is used as a chelating agent, and noble metals and transition metals are loaded on a molecular sieve or an oxide carrier by a grinding and mixing method. Among them, the prepared Ru / H-β molecular sieve catalyst has metal clusters of 1-2 nm and a relatively high dispersion, and this catalyst exhibits excellent Fischer-Tropsch reaction activity. CN112844461A discloses a method for preparing a Pt / SSZ-32 isomerization catalyst by using polyvinylpyrrolidone (PVP) as a stabilizer and 3-mercaptopropyltrimethoxysilane as a grafting agent. By first preparing a metal nanoparticle dispersion and then grafting the molecular sieve, the selectivity of isoparaffins is improved.

[0004] Currently, the methods for improving metal dispersion include ligand protection, support anchoring, constructing special structures, etc. However, the above methods have the disadvantages of complex processes and harsh synthesis conditions. The addition of organic ligands or surfactants not only increases the catalyst cost but also poses a pollution risk. Therefore, developing a green synthesis method for catalysts with a simple process and easy control to achieve the regulation of metal particle size is of great significance for obtaining highly efficient and low-cost nickel-based molecular sieve catalysts. Summary of the Invention

[0005] To solve the problems in the above catalyst preparation process, the purpose of the present invention is to provide a method for preparing a nickel-based molecular sieve catalyst with high metal dispersion. The present invention adopts an in-situ synthesis method, which has a simple process and is easy to control. A metal precursor is introduced in-situ into the molecular sieve precursor gel. First, the metal precursor is aged and stabilized, and by adjusting the pH value of the synthesis system and the ratios of the molecular sieve silicon source, aluminum source, base source, template agent, and metal precursor, the interaction between the metal and the existing substances in the synthesis system during the molecular sieve crystallization process is directly utilized, ultimately achieving high metal dispersion. At the same time, there is no need to add ligands, surfactants, or extra water, reducing the synthesis cost of the catalyst and the sewage discharge, which is environmentally friendly.

[0006] A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to the present invention specifically includes the following steps:

[0007] (1) First, mix the silicon source and the metal precursor evenly, then add the base source to adjust the pH value to 12.5 - 14.5, and obtain gel A after aging treatment;

[0008] (2) Mix the calculated amount of the template agent and the aluminum source evenly to obtain gel B; then add gel B to gel A obtained in step (1), and after mixing them evenly, obtain the initial gel C;

[0009] (3) Subject the initial gel C obtained in step (2) to crystallization, washing, drying, and calcination treatments to obtain the highly dispersed nickel-based molecular sieve catalyst.

[0010] In the above method, the silicon source in step (1) is selected from one or more of alkaline silica sol, tetraethyl orthosilicate, and sodium silicate; the metal precursor is selected from one or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, nickel citrate, and nickel acetylacetonate; the base source is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, and urea.

[0011] In the above method, the pH value in step (1) is 12.5 - 14.5, preferably 13 - 14; the aging treatment is room temperature aging, and the aging time is 6 - 24 h.

[0012] In the above method, the aluminum source in step (2) is selected from one or more of aluminum hydroxide, aluminum isopropoxide, sodium aluminate, sodium metaaluminate, pseudo-boehmite, and aluminum sulfate octadecahydrate; the template agent is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, hexamethylenediamine, diethylamine, triethylamine, di-n-propylamine, and di-n-butylamine.

[0013] In the above method, for the convenience of calculation, the silicon source, metal precursor, and aluminum source are respectively calculated as SiO2, Ni, and Al2O3, and the template agent and alkali source are respectively represented by the symbols R and S. Among them, by mass fraction, Ni:(SiO2 + Al2O3)=0.1wt%-10wt%, and by molar ratio, SiO2:Al2O3:R:S = 1:(0 - 0.1):(0 - 0.6):(0.02 - 2.5).

[0014] In the above method, the crystallization temperature in step (3) is 90 - 200 °C, and the crystallization time is 12 - 72 h; when washing after crystallization, by weight, the amount of deionized water used is 5 - 20 times that of the crystallization product, so that the final crystallization product is neutral; the drying temperature is 90 - 110 °C, and the drying time is 6 - 12 h; the calcination atmosphere is one of hydrogen, nitrogen, and air, the calcination temperature is 450 - 650 °C, and the calcination time is 4 - 8 h.

[0015] The present invention synthesizes a Ni / zeolite catalyst by an in-situ method, and in-situ introduces a metal nickel precursor during the synthesis of the molecular sieve support. First, the metal precursor is mixed with the molecular sieve silicon source, and aged at room temperature under a certain alkalinity to stabilize the metal, and then an aluminum source, a template agent, etc. are added. After mixing evenly, an initial gel is obtained. Before aging, by adjusting the pH value and the composition ratio of the gel, the interaction between the metal precursor and the molecular sieve precursor during the molecular sieve crystallization process is utilized to anchor the metal, inhibit the metal aggregation phenomenon during the high-temperature calcination treatment process, and improve the metal dispersion and the anti-sintering ability of the metal. For gel A containing a silicon source, a metal precursor, and an alkali source, the pH value cannot be too low, otherwise, during the aging process, the depolymerization of the silicon source by the alkali will be insufficient, and the reaction between the metal and the silicon species will be insufficient, thereby weakening the interaction between the metal and the silicon, which is not conducive to metal dispersion. In addition, too high a pH value will cause a certain destructive effect on the silicate species formed by the metal and the silicon, which is also not conducive to metal dispersion. For the composition ratio of substances, the ratio of the metal precursor to the silicon source cannot be too high, otherwise, the formed silicate species will be unstable, thereby affecting the dispersion. In the highly dispersed nickel-based molecular sieve prepared by the present invention, the nickel metal is well dispersed, and the average particle size of NiO is 2 - 3 nm. The Ni / Beta and Ni / Y catalysts prepared by the present invention have respectively obtained excellent alkane isomerization and methane dry reforming with carbon dioxide reaction performances.

[0016] The present invention also provides a highly dispersed nickel-based molecular sieve catalyst prepared in situ by the above method. The catalyst yield is higher than 60%, the nickel metal is well dispersed, and the average particle size of NiO is 2-3 nm.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] (1) Compared with methods for improving metal dispersion such as ligand protection, second metal modification, and constructing special structures, the present invention does not require the introduction of auxiliaries such as ligands or second metals, reducing environmental pollution by organic ligands. At the same time, the preparation process is simple and easy to control, reducing the catalyst preparation cost.

[0019] (2) Compared with the preparation of metal-loaded molecular sieve catalysts by traditional post-loading methods (such as impregnation method, ion exchange method, deposition precipitation method, etc.), the present invention directly synthesizes the catalyst by an in-situ one-step method, eliminating the complex process of first preparing the molecular sieve and then loading the metal, avoiding repeated drying and calcination operations, and reducing energy consumption. Compared with the synthesis of pure molecular sieve, the in-situ synthesis of Ni / zeolite catalyst shortens the crystallization time of the molecular sieve, increases the synthesis yield, which is higher than 60%, and greatly reduces the cost of catalyst preparation. This is attributed to the interaction between the metal precursor and the molecular sieve precursor during the crystallization process. Description of the Drawings

[0020] Figure 1 XRD pattern of the Ni / Zeolite catalyst synthesized in Examples 1-6.

[0021] Figure 2 XRD pattern of the catalyst synthesized in Comparative Example 1.

[0022] Figure 3 TEM image of the catalyst synthesized in Example 1.

[0023] Figure 4 TEM image of the catalyst synthesized in Comparative Example 1.

[0024] Figure 5 TEM image of the catalyst synthesized in Example 2.

[0025] Figure 6 TEM image of the catalyst synthesized in Example 3.

[0026] Figure 7 TEM image of the catalyst synthesized in Example 4. Detailed Description of the Invention

[0027] The details of the present invention can be more clearly understood in conjunction with the accompanying drawings and the description of the specific embodiments of the present invention. However, the specific embodiments of the present invention described herein are for the purpose of explaining the present invention only and should not be construed in any way as a limitation of the present invention.

[0028] Example 1

[0029] In the Ni / Beta catalyst, the initial gel composition of Beta zeolite is as follows: 1SiO2:0.16TEAOH:0.206NaOH:0.04Al2O3. Therefore, 34.86 g of sodium silicate solution (35 wt%) was weighed and then 1.270 g of Ni(NO3)2·6H2O was added. Finally, 0.824 g of NaOH was added and mixed evenly. The pH value was adjusted to 13.5, and then aged at room temperature for 12 h to obtain gel A; 9.42 g of TEAOH (25 wt%) solution was weighed, and then 0.656 g of NaAlO2 was added and mixed evenly to obtain gel B; gel B was added to gel A obtained by aging, ground and mixed evenly, and then placed in a 100 mL crystallization kettle and crystallized at 160 °C for 60 h; after the solid product was taken out, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / Beta catalyst. The yield of the Ni / Beta catalyst was increased to 68.95%.

[0030] The synthesized Ni / Beta catalyst was evaluated for the hydroisomerization reaction of n-hexane. First, ion exchange was carried out, and then the catalyst was in-situ reduced at 550 °C for 2 h under a hydrogen atmosphere. At a reaction temperature of 300 °C, a pressure of 2.0 MPa, a space velocity of 1 h -1 -1, and a hydrogen / oil ratio of 4, the n-hexane conversion rate of this catalyst was 77.3%, and at the same time, a high isomerized hexane yield of 72.1% was obtained, comparable to that of commercial Pt-based catalysts.

[0031] Comparative Example 1

[0032] The catalyst Ni / Beta-im was prepared by the impregnation method and compared with Example 1. First, Beta zeolite was synthesized. The initial gel composition of the zeolite was as follows: 1SiO2:0.16TEAOH:0.206NaOH:0.04Al2O3. Therefore, 34.86 g of sodium silicate (35 wt%) solution was weighed and placed in a mortar. Then, 9.42 g of TEAOH (25 wt%) solution was gradually added dropwise, and then ground evenly. Then, 0.824 g of NaOH and 0.656 g of NaAlO2 were added in turn and ground evenly. It was placed in a 100 mL crystallization kettle and crystallized at 160 °C for 72 h. After the solid product was taken out, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain Beta zeolite; the yield of the synthesized Beta zeolite was 53.21%, while the yield of the in-situ synthesized Ni / Beta catalyst in Example 1 was increased to 68.95%, and the optimal crystallization time was shortened from 72 h to 60 h.

[0033] Then, the catalyst Ni / Beta-im was synthesized by the impregnation method. 0.26 g of Ni(NO3)2·6H2O was weighed and dissolved in 1.2 g of water. After ultrasonic dissolution until completely dissolved, 1.3 g of Beta zeolite was added, stirred evenly, left standing at room temperature for 22 h, dried at 100 °C for 4 h, and finally calcined at 400 °C for 4 h to obtain the catalyst Ni / Beta-im.

[0034] Comparative Example 2

[0035] Same as Example 1, the same in-situ synthesis method was used, and only the pH value of gel A was changed to prepare the Ni / Beta-c catalyst. In the Ni / Beta-c catalyst, the initial gel composition of Beta-c zeolite was as follows: 1SiO2:0.16TEAOH:0.004NaOH:0.04Al2O3. Therefore, 34.86 g of sodium silicate solution (35 wt%) was weighed, then 1.270 g of Ni(NO3)2·6H2O was added, and finally 0.016 g of NaOH was added and mixed evenly to adjust the pH value to 12, and then aged at room temperature for 12 h to obtain gel A; 9.42 g of TEAOH (25 wt%) solution was weighed, and then 0.656 g of NaAlO2 was added and mixed evenly to obtain gel B; gel B was added to the aged gel A, ground and mixed evenly, and then placed in a 100 mL crystallization kettle and crystallized at 160 °C for 60 h; after the solid product was taken out, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / Beta-c catalyst. The yield of the Ni / Beta-c catalyst was 55.38%.

[0036] Example 2

[0037] In the Ni / ZSM-5 catalyst, the initial gel composition of the ZSM-5 molecular sieve is as follows: 1SiO2:0.08TPAOH:0.21NaOH:0.033Al2O3. Therefore, 20 g of alkaline silica sol (30 wt%) was weighed and placed in a mortar. After adding 1.256 g of Ni(NO3)2·6H2O and mixing evenly, 0.84 g of NaOH was added and ground evenly. The pH value was adjusted to 13.8, and then aged at room temperature for 12 h to obtain gel A; 6.51 g of TPAOH (25 wt%) solution was weighed, and after adding 0.549 g of NaAlO2 and grinding evenly, gel B was obtained; Gel B was added to gel A and ground evenly, and then placed in a 100 mL crystallization kettle and crystallized at 170 °C for 24 h; After taking out the solid product, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / ZSM-5 catalyst. The yield of this Ni / ZSM-5 catalyst was 83.45%.

[0038] Example 3

[0039] In the Ni / S-1 catalyst, the initial gel composition of the S-1 molecular sieve is as follows: 1SiO2:0.12TPAOH:0.22NaOH. Therefore, 20 g of alkaline silica sol (30 wt%) was weighed and placed in a mortar. After adding 1.189 g of Ni(NO3)2·6H2O and grinding evenly, 0.3 g of NaOH was added and ground evenly. The pH value was adjusted to 13.3, and then aged at room temperature for 18 h to obtain gel A; 9.76 g of TPAOH (25 wt%) solution was weighed, and after adding 0.58 g of NaOH and mixing evenly, gel B was obtained; Gel B was added to gel A and ground evenly, and then placed in a 100 mL crystallization kettle and crystallized at 170 °C for 24 h; After taking out the solid product, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / S-1 catalyst. The yield of this Ni / S-1 catalyst was 87.31%.

[0040] Example 4

[0041] In the Ni / MOR catalyst, the initial gel composition of the MOR molecular sieve is as follows: 1SiO2:0.2TEAOH:0.25NaOH:0.025Al2O3. Therefore, 20 g of alkaline silica sol (30 wt%) was weighed and placed in a mortar, 1.240 g of Ni(NO3)2·6H2O was added and ground evenly, then 1 g of NaOH was added and ground evenly. The pH value was adjusted to 14, and then aged for 6 h to obtain gel A; 11.78 g of TEAOH (25 wt%) solution was weighed, 1.666 g of Al2(SO4)3·18H2O was added, and after mixing evenly, gel B was obtained; finally, gel B was added to gel A, ground evenly, and then placed in a 100 mL crystallization kettle, heated to 170 °C and crystallized for 36 h; after taking out the solid product, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / MOR catalyst. The yield of the Ni / MOR catalyst was 77.92%.

[0042] Example 5

[0043] In the Ni / ZSM-22 catalyst, the initial gel composition of the ZSM-22 molecular sieve is as follows: 1SiO2:0.27DAH:0.1KOH:0.01Al2O3. Therefore, 20 g of alkaline silica sol (30 wt%) was weighed and placed in a mortar, 1.209 g of Ni(NO3)2·6H2O was added and ground evenly, and then 0.561 g of KOH was added and ground evenly. The pH value was adjusted to 13.5, and then aged at room temperature for 12 h to obtain gel A; 3.138 g of DAH was weighed, 0.666 g of Al2(SO4)3·18H2O was added, and ground evenly to obtain gel B; finally, gel B was added to gel A, ground evenly, and then placed in a 100 mL crystallization kettle, and crystallized at 160 °C for 72 h; after taking out the solid product, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / ZSM-22 catalyst. The yield of the Ni / ZSM-22 catalyst was 62.52%.

[0044] Example 6

[0045] In the Ni / Y catalyst, the initial gel composition of the Y zeolite is as follows: 1SiO2:2.4NaOH:0.1Al2O3. Therefore, 20 g of basic silica sol (30 wt%) was weighed and placed in a mortar. After adding 1.391 g of Ni(NO3)2·6H2O and grinding evenly, 0.84 g of NaOH was added and mixed evenly. The pH was adjusted to 13.8, and then aged at room temperature for 12 h to obtain gel A. 8.76 g of NaOH and 0.82 g of NaAlO2 were weighed and ground evenly to obtain gel B; gel B was added to gel A and ground evenly, then placed in a 100 mL crystallization kettle and crystallized at 100 °C for 24 h; after taking out the solid product, it was centrifuged and washed with deionized water until the supernatant was neutral, dried overnight at 100 °C, and calcined at 550 °C for 6 h to obtain the Ni / Y catalyst. The yield of the Ni / Y catalyst was 72.26%.

[0046] The synthesized Ni / Y catalyst was evaluated for the dry reforming reaction of methane with carbon dioxide. First, the catalyst was in-situ reduced at 550 °C for 2 h in a hydrogen atmosphere. Under the conditions of a reaction temperature of 750 °C, normal pressure, a catalyst dosage of 0.4 g, and GHSW = 24000 ml / g·h, the catalyst achieved a CO2 conversion rate of 90.84% and a CH4 conversion rate of 84.15%, approaching the equilibrium conversion rate at 750 °C.

[0047] It can be seen from Figure 1 that the catalysts synthesized in Examples 1-6 did not show characteristic diffraction peaks corresponding to NiO crystals at 2θ = 37.3°, 43.3°, and 62.9°, indicating good metal dispersion. However, the catalyst synthesized by the impregnation method in Comparative Example 1 showed characteristic diffraction peaks corresponding to NiO crystals at 2θ = 37.3°, 43.3°, and 62.9°, indicating a lower metal dispersion degree of the catalyst. See Figure 2 .

[0048] At the same time, it can be seen from Figure 3 and Figure 4 results that no obvious metal particle aggregation was found in the TEM image of the Ni / Beta catalyst synthesized in Example 1, and the average particle size of NiO was 2.14 nm. However, obvious aggregated metal particles were found in the TEM image of the Ni / Beta-im catalyst synthesized in Comparative Example 1, and the average particle size of NiO was 7.42 nm. This result is consistent with the XRD result. In addition, due to the lower pH value of gel A of the Ni / Beta-c catalyst synthesized in Comparative Example 2, the silicon species were not completely depolymerized, weakening the interaction between the metal and the silicon species, resulting in poor metal dispersion and an average particle size of NiO of 6.57 nm.

[0049] Figures 5-7TEM images of the Ni / ZSM-5, Ni / S-1, and Ni / MOR catalysts synthesized in Examples 2, 3, and 4, respectively, showed no obvious aggregation of metal particles. The average particle sizes of NiO were 2.89, 2.65, and 2.36 nm, respectively, indicating good metal dispersion.

Claims

1. A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst, characterized in that, Specifically, it includes the following steps: (1) First, mix the silicon source and the nickel metal precursor evenly, then add the base source to adjust the pH value to 12.5 - 14, and obtain gel A after aging treatment; (2) Mix the calculated amount of template agent and aluminum source evenly to obtain gel B; then add gel B to gel A obtained in step (1), and obtain the initial gel C after the two are mixed evenly; (3) Carry out crystallization, washing, drying, and calcination on the initial gel C obtained in step (2) to obtain the highly dispersed nickel-based molecular sieve catalyst. The crystallization temperature is 90 - 200 °C, and the crystallization time is 12 - 72 h; the catalyst yield is higher than 60%, and the average particle size of NiO is 2 - 3 nm.

2. The method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, wherein, The silicon source in step (1) is selected from one or more of alkaline silica sol, tetraethyl orthosilicate, and sodium silicate; the nickel metal precursor is selected from one or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, nickel citrate, and nickel acetylacetonate; the base source is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, and urea.

3. The method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, characterized in that The pH value in step (1) is 13 - 14; the aging treatment is room temperature aging, and the aging time is 6 - 24 h.

4. A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, characterized in that, The aluminum source in step (2) is selected from one or more of aluminum hydroxide, aluminum isopropoxide, sodium aluminate, sodium metaaluminate, pseudoboehmite, and aluminum sulfate octadecahydrate; the template agent is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, hexamethylenediamine, diethylamine, triethylamine, di-n-propylamine, and di-n-butylamine.

5. A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, characterized in that, For the convenience of calculation, the silicon source, nickel metal precursor, and aluminum source are respectively calculated as SiO2, Ni, and Al2O3, and the template agent and base source are respectively represented by the symbols R and S. Among them, by mass fraction, Ni:(SiO2 + Al2O3)=0.1 wt% - 10 wt%, and by molar ratio, SiO2:Al2O3:R:S = 1:(0 - 0.1):(0 - 0.6):(0.02 - 2.5).

6. A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, characterized in that, When washing after crystallization in step (3), by weight, the amount of deionized water used is 5 - 20 times that of the crystallization product, so that the final crystallization product is neutral.

7. A method for in-situ preparing a highly dispersed nickel-based molecular sieve catalyst according to claim 1, characterized in that, The drying temperature in step (3) is 90 - 110 °C, and the drying time is 6 - 12 h; the calcination atmosphere is one of argon, nitrogen, and air, the calcination temperature is 450 - 650 °C, and the calcination time is 4 - 8 h.

8. The highly dispersed nickel-based molecular sieve catalyst prepared in-situ by the method according to any one of claims 1-7, characterized in that, The average particle size of NiO is 2 - 3 nm.

9. Application of the Ni / Beta molecular sieve catalyst prepared in situ by the method according to any one of claims 1 - 7 in the alkane isomerization reaction or application of the Ni / Y molecular sieve catalyst prepared in the dry reforming reaction of methane and carbon dioxide.

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