CN115007197B

CN115007197B - Multistage hole ZSM-5 molecular sieve encapsulated Ni metal catalyst with micropores and mesopores, and preparation method and application thereof

Info

Publication number: CN115007197B
Application number: CN202210740892.3A
Authority: CN
Inventors: 田亚杰; 刘国柱; 郭龙辉
Original assignee: Material Green Creation And Manufacturing Haihe Laboratory; Henan University
Current assignee: Material Green Creation And Manufacturing Haihe Laboratory; Henan University
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2024-02-27
Anticipated expiration: 2042-06-27
Also published as: CN115007197A

Abstract

The invention discloses a multistage pore ZSM-5 molecular sieve encapsulated Ni metal catalyst with micropores and mesopores, a preparation method and application thereof, which are used for catalyzing a reaction for preparing low-carbon olefin by heavy oil pyrolysis and belong to the field of petrochemical industry. The invention takes the acid center on the surface of the molecular sieve as a cracking active site to catalyze the cracking of macromolecular hydrocarbon to form micromolecules, and then utilizes the highly dispersed Ni active center in the pore canal of the molecular sieve to promote the dehydrogenation reaction of micromolecular alkane to form low-carbon olefin. The stability of Ni metal active center encapsulated in the molecular sieve pore canal is obviously enhanced due to the space domain-limiting effect, and the catalytic cracking stability is obviously improved.

Description

Multistage hole ZSM-5 molecular sieve encapsulated Ni metal catalyst with micropores and mesopores, and preparation method and application thereof

Technical Field

The invention relates to a molecular sieve catalyst and a preparation method and application thereof, in particular to a multistage pore ZSM-5 molecular sieve encapsulated Ni metal catalyst with micropores and mesopores for the catalyst and the preparation method and application thereof, belonging to the field of catalysts.

Background

With the rapid development of the economic society in China, the demand for low-carbon olefins represented by ethylene, propylene and butylene is continuously rising (Chemical Engineering Journal 2021,409,128192). The low-carbon olefin can be used as raw material for producing plastics, fibers and fine chemical intermediates. In the past, the low-carbon olefin is mainly sourced from the steam cracking process of naphtha, and accounts for more than 60% of the total source of olefin. However, the steam cracking process has the problems of high reaction temperature (> 800 ℃), high energy consumption, high carbon dioxide emission and the like, and does not meet the sustainable green development requirement (Journal of Industrial and Engineering Chemistry 2012,18,1736). And the selectivity of ethylene in the product of the naphtha catalytic cracking process is higher, and the yield of propylene which belongs to byproducts is lower, so that technical limitations exist. In recent years, olefin preparation technologies represented by methods of heavy oil catalytic cracking, alkane dehydrogenation, alcohol to olefin and the like are rapidly developed, and a great deal of demands of low-carbon olefin downstream markets are strongly supplemented. In particular, catalytic cracking processes have been developed based on thermal cracking, and can be upgraded to put into production using existing equipment, with a high degree of attention from a large number of researchers (Applied Catalysis A: general 2011,398,1).

The key technical node in the catalytic cracking technology is the design of a cracking catalyst. ZSM-5 molecular sieves have received extensive attention from researchers due to their high hydrothermal stability and regular pore characteristics. A typical ZSM-5 molecular sieve consists of a silica-alumina framework with regular straight and sinusoidal channels (0.51X 0.55 nm) ² ,0.53×0.56nm ² Fuel 2021,306,121725). The surface of the catalyst has rich acidic sites as active centers of cracking reaction, and the hydrocarbon molecules are catalyzed to crack to generate the low-carbon olefin (Fuel Processing Technology 2013,108,25) through a typical carbonium ion mechanism. It should be noted, however, that conventional microporous ZSM-5 molecular sieves have pore sizes of only about 0.5nm and that hydrocarbon molecules present significant diffusion resistance within the pore channels of the sieve. If the acid sites on the inner surface of the molecular sieve are required to be fully utilized, hydrocarbon molecules need to diffuse through long microporous channels, so that the cracking activity is reduced. And is cleavedThe resulting olefin molecules are very susceptible to saturation to alkanes by bimolecular hydrogen transfer reactions, resulting in reduced yields of olefins in the product (Microporous and Mesoporous Materials 2012,149,126).

Especially based on the current state of petrochemical development in China, a large amount of heavy oil components exist in oil products. Heavy oil molecules generally have carbon chain lengths greater than 7. The molecular sieve is used as a catalyst, the catalytic cracking reaction of heavy oil molecules has more remarkable diffusion and remarkable effect, and how to improve the activity of the cracking reaction by accelerating the diffusion rate of hydrocarbon molecules has become one of the key scientific problems for improving the yield of olefins in products. Studies have shown that constructing fast diffusion channels in molecular sieves is one of the effective ways to increase the conversion of reactants by cleavage. The two-dimensional nano sheet ZSM-5 molecular sieve can be prepared by utilizing the induction effect of the template agent in the synthesis of the molecular sieve, the two-dimensional molecular sieve has high surface area, and the nano sheet has rich interlayer mesopores, so that the hydrocarbon molecular conversion can be promoted. But the thermal stability of the structure is low due to the fact that the thickness of the sheet layer is in nano-scale (about 2 nm), which is unfavorable for the application of the sheet layer in cracking reaction. And excessive amounts of external surface acid are very likely to promote bimolecular hydrogen transfer reactions at the molecular sieve surface (Chinese Journal of Chemical Engineering2021,38,276). Based on ZSM-5 molecular sieve catalyst, how to construct a rapid diffusion channel to realize rapid diffusion of reactant molecules to promote molecular conversion and inhibit secondary consumption of olefin molecules in the product is a key to realizing a high-yield olefin process in a cracking product reaction.

Disclosure of Invention

Based on the background, the application provides a strategy based on seed crystal induction-in-situ synthesis, and a preparation method for preparing a multistage pore ZSM-5 molecular sieve encapsulated high-dispersion metal Ni catalyst with micropores and mesopores, which is used for preparing low-carbon olefin by catalyzing heavy oil pyrolysis. In the synthesis process of the molecular sieve, the introduction of the seed crystal can obviously accelerate the nucleation rate of the molecular sieve, the lamellar ZSM-5 molecular sieve is formed by induction, and the lamellar molecular sieve stacking arrangement can construct a rich mesoporous structure so as to promote the diffusion rate of hydrocarbon molecules in the cracking reaction. Secondly, ni complex is added into the synthetic liquid, and is highly dispersed in the molecular sieve, so that the dehydrogenation activity of active metal Ni can be utilized to inhibit olefin molecules in the product from being saturated through hydrogen transfer reaction. While promoting hydrocarbon molecular conversion, the occurrence of secondary reactions of the product olefin molecules is suppressed. In addition, the template agent dosage in the molecular sieve synthesis liquid can be properly reduced due to the introduction of the seed crystal, and the catalyst synthesis strategy has better economy.

The invention firstly provides a preparation method of a molecular sieve catalyst for efficiently catalyzing heavy oil molecular cracking, which comprises the following steps:

(1) Mixing Ni source solution with a silanization reagent, and stirring at room temperature to obtain Ni complex solution; mixing a silicon source, a template agent and water, stirring for a period of time at room temperature, performing hydrothermal treatment, washing with water after the hydrothermal treatment is finished, and sequentially drying and roasting to obtain a nano molecular sieve seed crystal;

(2) Mixing a silicon source, a template agent, an alkali source, an aluminum source and water, stirring for a period of time at room temperature, then adding the molecular sieve seed crystal prepared in the step (1), continuously stirring for a period of time at room temperature, then adding the Ni complex solution obtained in the step (1), and stirring for a period of time to obtain a synthetic solution;

(3) Carrying out hydrothermal treatment on the synthetic liquid obtained in the step (2), washing with water after the hydrothermal treatment is finished, and sequentially drying and roasting to obtain the encapsulated NiO molecular sieve powder;

(4) And (3) adding a certain amount of ammonium salt solution into the solution obtained in the step (3), performing ion exchange treatment at a certain temperature, cleaning with water after exchange, and sequentially drying, roasting and reducing to obtain the molecular sieve-encapsulated Ni catalyst with the multi-stage pore structure.

Preferably, in step (1), the nickel source comprises one or both of nickel nitrate or nickel chloride; the silane reagent is N- [3- (trimethoxysilyl) propyl ] ethylenediamine (TPE); the molar ratio of Ni to TPE in the Ni complex is 1/10-1/1.

Preferably, in step (2), the silicon source comprises one of silica gel, fumed silica, inorganic silicate, organosilicate, white carbon black, or silicic acid; the template agent is one of tetrapropylammonium hydroxide and tetrapropylammonium bromide; siO (SiO) ₂ The molar ratio of the template agent to the water is 100 (5-50): 500-3000.

Preferably, in step (3), the silicon source comprises one of silica gel, fumed silica, inorganic silicate, organosilicate, white carbon black, or silicic acid; the template agent is one of tetrabutyl phosphonium hydroxide and tetrabutyl phosphonium bromide; the aluminum source comprises one or more of an organic aluminum compound, an inorganic aluminum salt or a complex thereof; the alkali source is one or more of sodium hydroxide or potassium hydroxide; in the synthetic liquid, siO ₂ 、Al ₂ O ₃ The molar ratio of the template agent to the water is 100 (0.1-2.5) (5-50) (500-3000), the proportion of Si in the seed crystal to the total Si content is 1-20%, and the metal Ni load in the prepared catalyst is 1-15% of pure Ni.

Preferably, in the step (2), the temperature of the hydrothermal treatment is 100-180 ℃, and the time of the hydrothermal treatment is 12-72 hours; the temperature of the roasting treatment is 300-600 ℃, and the time of the roasting treatment is 2-12 h;

Preferably, in the step (4), the temperature of the hydrothermal treatment is 100-200 ℃, and the time of the hydrothermal treatment is 12-120 hours; the temperature of the roasting treatment is 300-600 ℃, and the time of the roasting treatment is 2-12 h;

preferably, in the step (5), the ion exchange temperature is 70-95 ℃, the ion exchange time is 2-12 h, the roasting temperature is 300-650 ℃, the roasting time is 4-12 h, and the roasting is performed in an air atmosphere; the reduction temperature is 450-650 ℃, the reduction time is 4-12 h, and the reduction is carried out in a hydrogen atmosphere.

The second purpose of the invention is to provide the catalyst for catalyzing the cracking reaction of hydrocarbon compounds, which is prepared by the preparation method, wherein the catalyst is a multistage hole ZSM-5 molecular sieve encapsulated metal Ni catalyst with micropores and mesopores.

A third object of the present invention is to provide the use of the above catalyst for catalyzing the cracking of hydrocarbon compounds to produce light olefins.

A fourth object of the present invention is to provide a method for preparing light olefins by cracking a hydrocarbon compound, wherein the catalyst is used for catalyzing.

Preferably, the hydrocarbon compound is preferably a heavy oil component wherein the heavy oil molecule has a common carbon chain length of greater than 7.

ADVANTAGEOUS EFFECTS OF INVENTION

The invention prepares the multistage hole ZSM-5 molecular sieve encapsulated high-dispersion metal Ni catalyst with micropores and mesopores for catalyzing heavy oil cracking to prepare the application of low-carbon olefin. The rapid diffusion built with multi-stage pores facilitates the conversion of feedstock hydrocarbon molecules. Meanwhile, part of alkali metal Ni encapsulated in the molecular sieve can reduce the acid quantity on the surface of the molecular sieve to inhibit olefin bimolecular hydrogen transfer reaction through interaction with oxygen atoms on the surface of the molecular sieve, and the rest of Ni metal can promote the generated alkane molecules to be secondarily converted into olefin through dehydrogenation. The encapsulation effect of the molecular sieve pore canal can inhibit agglomeration of the metal Ni at high temperature. Thereby improving the yield of the low-carbon olefin in the catalytic heavy oil cracking reaction.

Drawings

FIG. 1 is a characterization result of the multi-stage pore molecular sieve catalyst prepared in example 1, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst, and b is a distribution diagram of particle size of monomer nano-crystalline particles obtained by statistics.

FIG. 2 is a representation of the hierarchical pore molecular sieve catalyst prepared in example 1, wherein a is a TEM image of the hierarchical pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle size of the metal particles obtained by statistics.

Fig. 3 is an XRD pattern of the multi-stage pore molecular sieve catalyst prepared in example 1.

FIG. 4 is a characterization result of the multi-stage pore molecular sieve catalyst prepared in example 6, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst, and b is a distribution diagram of the particle size of the monomer nano-crystalline particles obtained by statistics.

FIG. 5 is a graph showing the results of characterization of the multi-stage pore molecular sieve catalyst prepared in example 6, wherein a is a TEM image of the multi-stage pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

Fig. 6 is an XRD pattern of the multi-stage pore molecular sieve catalyst prepared in example 6.

FIG. 7 is a characterization result of the multi-stage pore molecular sieve catalyst prepared in example 11, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst, and b is a distribution diagram of the particle size of the monomer nano-crystalline particles obtained by statistics.

FIG. 8 is a graph showing the results of characterization of the multi-stage pore molecular sieve catalyst prepared in example 11, wherein a is a TEM image of the multi-stage pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

Fig. 9 is an XRD pattern of the multi-stage pore molecular sieve catalyst prepared in example 11.

FIG. 10 is a characterization result of the multi-stage pore molecular sieve catalyst prepared in example 16, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst, and b is a distribution diagram of the particle size of the monomer nano-crystalline particles obtained by statistics.

FIG. 11 is a graph showing the results of characterization of the multi-stage pore molecular sieve catalyst prepared in example 16, wherein a is a TEM image of the multi-stage pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

Fig. 12 is an XRD pattern of the multi-stage pore molecular sieve catalyst prepared in example 16.

FIG. 13 is a graph showing the characterization of the molecular sieve catalyst prepared in example 21, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst and b is a distribution diagram of the particle size of the monomer nano-crystallites obtained by statistics.

FIG. 14 is a graph showing the results of characterization of the molecular sieve catalyst prepared in example 21, wherein a is a TEM image of a hierarchical pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

Fig. 15 is an XRD pattern of the molecular sieve catalyst prepared in example 21.

FIG. 16 is a graph showing the characterization of the molecular sieve catalyst prepared in example 22, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst and b is a distribution chart of the particle size of the monomer nano-crystallites obtained by statistics.

FIG. 17 is a graph showing the results of characterization of the molecular sieve catalyst prepared in example 22, wherein a is a TEM image of a hierarchical pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

FIG. 18 is a characterization result of the molecular sieve catalyst prepared in example 23, wherein a is an SEM image of the multi-stage pore molecular sieve catalyst and b is a distribution diagram of the particle size of the monomer nanocrystalline obtained by statistics.

FIG. 19 is a graph showing the results of characterization of the molecular sieve catalyst prepared in example 23, wherein a is a TEM image of a hierarchical pore molecular sieve, b is a distribution diagram of metal particles in the catalyst particles, and c is a distribution diagram of the particle diameters of the metal particles obtained by statistics.

FIG. 20 shows a graph of (a) the cleavage activity and (b) the low-carbon olefin selectivity of example 1, example 2, example 3 for the catalysis of n-decane, and (c) the catalytic stability at 600 ℃.

FIG. 21 shows graphs of (a) the cleavage activity and (b) the low-carbon olefin selectivity of example 1, example 7, example 8, example 9 for catalyzing n-decane, and (c) the catalytic stability at 600 ℃.

FIG. 22 shows a graph of (a) the cleavage activity of n-decane and (b) the selectivity for lower olefins, for example 1, example 21, example 22, example 23, and (c) the catalytic stability at 600 ℃.

FIG. 23 shows a graph of (a) the cleavage activity and (b) the low-carbon olefin selectivity of example 26 for the catalysis of n-decane.

Detailed Description

The following describes the present invention in detail. The following description of the technical features is based on the representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

in the present specification, the numerical range indicated by the term "numerical value a to numerical value B" means a range including the end point numerical value A, B.

In the present specification, unless specifically stated otherwise, "a plurality" of "a plurality of" etc. means a numerical value of 2 or more.

In the present specification, "%" means mass% unless otherwise specified.

As referred to herein, the "room temperature" is generally at a temperature of "10℃to 40 ℃.

First aspect

The first aspect of the present invention provides a method for preparing a molecular sieve catalyst for efficiently catalyzing the cracking of heavy oil molecules, comprising the steps of:

nickel nitrate hexahydrate (Ni (NO) ₃ ) ₂ ·6H ₂ O) dissolving in deionized water, and stirring for a period of time at room temperature to obtain nickel nitrate solution. Weighing a certain amount of N3- (trimethoxysilyl) propyl ]Ethylenediamine (TPE) was dissolved in the nickel nitrate solution prepared as described above, and stirred at room temperature for a while to prepare a Ni complex solution.

The template agent and deionized water are mixed, and then a silicon source is slowly added dropwise thereto, and the mixture is stirred at room temperature for a period of time. After the stirring is completed, transferring the synthetic solution into a hydrothermal crystallization kettle, and carrying out hydrothermal crystallization at a certain temperature for a certain time. And washing with deionized water, drying and roasting in sequence to obtain the nano molecular sieve seed crystal.

And (3) weighing the template agent and the aluminum source, mixing the template agent and the aluminum source, stirring the mixture for a period of time at room temperature, then adding alkali liquor and deionized water into the mixture, and continuously stirring the mixture for a period of time at room temperature. Slowly adding a silicon source dropwise into the solution through a constant pressure separating funnel, and stirring for a period of time at room temperature. Then adding the molecular sieve seed crystal prepared in the previous step, and continuously stirring for a period of time at room temperature. After the stirring is completed, adding a certain amount of the prepared Ni complex solution, and continuously stirring for a period of time at room temperature to obtain a synthetic solution.

And transferring the synthetic liquid obtained in the steps into a hydrothermal crystallization kettle for hydrothermal crystallization to obtain a hydrothermal product. Washing the synthesized product with water to be neutral, and sequentially drying and roasting to obtain the encapsulated NiO molecular sieve powder.

Mixing the molecular sieve powder prepared in the previous step with ammonia salt solution, and performing ion exchange. And then washing with water to be neutral, and sequentially drying, roasting and reducing to obtain the molecular sieve Ni metal catalyst with the hierarchical pore structure.

Synthetic liquid gel

In some embodiments of the present invention, for the silicon source, one or more of a silica gel, fumed silica, inorganic silicate, organosilicate, white carbon black, or silicic acid may be used. In some specific embodiments, the silicon source comprises one or a combination of two or more of silica sol, ethyl orthosilicate, or sodium silicate.

For the aluminum source usable in the present invention, one or more of an organoaluminum compound, pseudo-boehmite, aluminum gel, and an organic acid salt, an inorganic acid salt or a complex thereof containing aluminum, and a hydrate may be mentioned. Preferably, the aluminum source of the present invention may be selected from one or more of pseudo-boehmite, alumina, aluminum gel, sodium aluminate, aluminum phosphate, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum isopropoxide, or aluminum hydroxide. In some specific embodiments, the aluminum source comprises aluminum sulfate, aluminum nitrate, aluminum isopropoxide, or a combination of one or more thereof.

In the present invention, the templating agent also plays an important role. The template agent has the main function of structure guiding, and different template agents have obvious influence on the formed skeleton structure and product properties. The template agent comprises a quaternary ammonium salt surfactant, and specifically, the quaternary ammonium salt surfactant comprises tetrabutyl phosphonium hydroxide and tetrabutyl phosphonium bromide.

In the present invention, for the optional presence of an alkaline source, which in some specific embodiments comprises sodium hydroxide or potassium hydroxide, it may be any alkaline material practicable in the art.

The solvent is not particularly limited, and may be any solvent that can be used in the art, for example: polar solvents such as water or alcohols. Preferably, water is used as solvent.

In the present invention, the seed crystal synthesis liquid SiO ₂ The molar ratio of the template agent to the water is 100 (5-50) (500-3000)The method comprises the steps of carrying out a first treatment on the surface of the Catalyst SiO in the synthetic liquid gel ₂ 、Al ₂ O ₃ The molar ratio of the template agent to the water is 100 (0.1-2.5) (5-50) (500-3000).

Step of hydrothermal crystallization

And carrying out hydrothermal crystallization treatment on the synthetic hydrogel to obtain a hydrothermal crystallization product. Specifically, the precursor solution obtained above is placed in a hydrothermal reaction kettle for hydrothermal crystallization treatment to obtain a product.

The temperature for the hydrothermal treatment may be 130 ℃ or higher and 200 ℃ or lower, preferably 140 ℃ to 160 ℃; the time for the hydrothermal treatment may be 24 to 168 hours, preferably 48 to 72 hours.

Further, the present invention generally performs post-treatment operations such as washing, drying, etc. on the hydrothermal crystallized product. Specifically, for washing, deionized water may be used for washing to neutrality, and the drying may be performed at a temperature of 80 to 150 ℃.

Roasting

And (3) roasting the hydrothermal product for one time to obtain the NiO-encapsulated molecular sieve powder. The conditions for the primary calcination are not particularly limited, and the molecular sieve catalyst precursor of the present invention can be obtained by calcining at 300 to 650℃for 4 to 12 hours.

Ion exchange

Further, the present invention uses an ammonium chloride solution to ion exchange the intermediate product.

Further, the conditions under which the ion exchange is performed are not particularly limited in the present invention, as long as the ion exchange of the present invention can be achieved. In some specific embodiments, the temperature of the ion exchange treatment is 20 ℃ to 120 ℃ and the time of the ion exchange treatment is 2 hours to 48 hours.

Likewise, the ion exchange product is typically subjected to post-treatment operations such as washing, drying, calcination, reduction, and the like. Specifically, for washing, deionized water may be used for washing to neutrality, the drying may be performed at a temperature of 80 to 150 ℃, and the drying time may be 4 to 12 hours. Roasting and reducing the ion exchange product to obtain the molecular sieve catalyst. The conditions for firing are not particularly limited, and may be firing at 300 to 650℃for 4 to 12 hours. The reduction condition can be that the reduction is carried out for 4 to 12 hours at the temperature of 450 to 650 ℃, and the reduction is carried out under the hydrogen atmosphere, thus obtaining the molecular sieve Ni metal catalyst with the multistage pore structure.

Second aspect

The second aspect of the invention provides a multistage pore molecular sieve Ni metal catalyst prepared by the preparation method according to the first aspect of the invention.

Third aspect of the invention

The third aspect of the invention provides an application of the multistage pore molecular sieve Ni metal catalyst prepared by the preparation method of the first aspect of the invention in high-efficiency catalytic heavy oil molecular cracking.

Fourth aspect of

In a fourth aspect, the present invention provides a method for efficiently catalyzing heavy oil molecular cracking, which uses the above multi-stage pore molecular sieve Ni metal catalyst as a catalyst.

The Ni source used in the invention takes nickel nitrate as an example, the silicon source used in the invention takes Tetraethoxysilane (TEOS) as an example, the water used in the invention is deionized water, and the reagents used in the invention are all analytically pure reagents.

Examples 1 to 5

In the synthesized hierarchical pore ZSM-5 molecular sieve encapsulated metal Ni catalyst, the examples of this section focus on variations in the molar ratio of Ni to silane reagent and Ni loading in the metal precursor.

2g of nickel nitrate hexahydrate (Ni (NO) ₃ ) ₂ ·6H ₂ O) was dissolved in 8g of deionized water and stirred at room temperature for 1 hour to prepare a nickel nitrate solution. Weighing a certain amount of N3- (trimethoxysilyl) propyl]Ethylenediamine (TPE) was dissolved in 5g of the nickel nitrate solution prepared above, and stirred at room temperature for 1 hour to prepare a Ni complex solution.

12.2016g of tetrapropylammonium hydroxide (TPAOH) and 1.6488g of deionized water were weighed and mixed, 8.75g of TEOS was slowly added dropwise thereto, and stirred at room temperature for 24 hours. After the stirring is completed, the synthetic solution is transferred into a hydrothermal crystallization kettle, and is subjected to hydrothermal crystallization at 80 ℃ for 72 hours. And washing with deionized water, drying at 120 ℃ for 6 hours, and roasting at 550 ℃ for 6 hours in the atmosphere of muffle furnace air to obtain the nano molecular sieve seed crystal.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. 7.9165g TEOS was weighed and slowly dropped into the above solution through a constant pressure separating funnel, and stirred at room temperature for 3 hours. Then 0.12g of the molecular sieve seed crystal prepared in the previous step is added, stirring is continued for 1h at room temperature, then a certain amount of the Ni complex solution prepared in the previous step is added, and stirring is continued for 2h at room temperature, so as to obtain a synthetic liquid.

Transferring the synthetic liquid obtained in the steps into a hydrothermal crystallization kettle, and performing hydrothermal crystallization for 48 hours at 130 ℃ to obtain a hydrothermal product. Washing the synthesized product with water to be neutral, drying the product for 6 hours at 120 ℃, and roasting the product for 6 hours at 550 ℃ in the atmosphere of muffle furnace air to obtain the NiO-encapsulated molecular sieve powder.

Weighing 1g of the molecular sieve powder prepared in the previous step and 125mL of NH ₄ Cl (1 mol/L) solution is mixed, stirred for 3 hours at 85 ℃, washed to be neutral by water, dried for 6 hours at 120 ℃, baked for 6 hours at 550 ℃ in a muffle air atmosphere, and tubular furnace H ₂ And (3) reducing for 5 hours at 500 ℃ in the atmosphere to obtain the molecular sieve Ni metal catalyst with the multi-level pore structure.

The mass of TPE used in example 1 was 4.5877g and the mass of Ni complex solution used was 5.7009g. The Ni/TPE molar ratio was 1:6, at this time, the theoretical load amount calculated as metallic Ni is 5%.

The mass of TPE used in example 2 was 4.5877g and the mass of Ni complex solution used was 3.4205g. The Ni/TPE molar ratio was 1:6, at this time, the theoretical load amount calculated as metallic Ni is 3%.

The mass of TPE used in example 3 was 4.5877g and the mass of Ni complex solution used was 7.9813g. The Ni/TPE molar ratio was 1:6, at this time, the theoretical load amount calculated as metallic Ni is 7%.

The mass of TPE used in example 4 was 3.0585g and the mass of Ni complex solution used was 4.7916g. The Ni/TPE molar ratio was 1:4, at this time, the theoretical load calculated as metallic Ni was 5%.

FIG. 1 is a SEM image of the catalyst prepared in example 1, showing that the catalyst has a spindle-shaped morphology of layered molecular sieve clusters (FIG. 1 a) and the monomer nanocrystalline clusters obtained by statistics have an elongated axis dimension of about 600nm (FIG. 1 b). The pore volume of the molecular sieve catalyst is 0.529m ³ Per g, surface area of 498m ² /g。

FIG. 2 is a TEM image of the catalyst prepared in example 1. From the TEM images, the prepared molecular sieve catalyst was found to be present from distinct mesopores (fig. 2 a); the metal particles were uniformly distributed in the catalyst particles (FIG. 2 b), and the average particle diameter of the metal particles obtained by statistics was 0.68nm (FIG. 2 c).

FIG. 3 shows the XRD pattern of the catalyst prepared in example 1, which was found to have a typical MFI molecular sieve crystalline form by comparison with pdf card (JCPDS-44-0003) in Jade software. Thanks to the encapsulation of metallic Ni inside the molecular sieve, no diffraction peaks of Ni were detected in the XRD pattern.

Examples 6 to 10

In the process of preparing the multi-stage pore structure molecular sieve packaging metal Ni catalyst, the applicant adopts the seed crystals with different proportions to prepare a series of molecular sieve catalysts.

2g of nickel nitrate hexahydrate (Ni (NO) ₃ ) ₂ ·6H ₂ O) was dissolved in 8g of deionized water and stirred at room temperature for 1 hour to prepare a nickel nitrate solution. Weighing 4.5877g N- [3- (trimethoxysilyl) propyl group]Ethylenediamine (TPE) was dissolved in 5g of the nickel nitrate solution prepared above, and stirred at room temperature for 1 hour to prepare a Ni complex solution.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. A certain amount of TEOS is weighed and slowly dripped into the solution through a constant pressure separating funnel, and stirring is carried out for 3 hours at room temperature. Then, a certain amount of the molecular sieve seed crystal prepared in the previous step was added, stirring was continued at room temperature for 1 hour, then 5.7009g of the Ni complex solution prepared above was added, and stirring was continued at room temperature for 2 hours to obtain a synthetic solution.

The mass of the nano molecular sieve seed crystal used in example 6 was 0.024g, the addition amount of TEOS was 8.2499g, and the Si content of the seed crystal was 1%.

The mass of the nano molecular sieve seed crystal used in example 7 was 0.060g, the addition amount of TEOS was 8.1249g, and the proportion of Si in the seed crystal to the total Si content was 2.5%.

The mass of the nano molecular sieve seed crystal used in example 8 was 0.240g, the addition amount of TEOS was 7.4999g, and the proportion of Si in the seed crystal to the total Si content was 10%.

The mass of the nano molecular sieve seed crystal used in example 9 was 0.360g, the addition amount of TEOS was 7.0832g, and the proportion of Si in the seed crystal to the total Si content was 15%.

The mass of the nano molecular sieve seed crystal used in example 10 was 0.480g, the addition amount of TEOS was 6.6666g, and the Si content of the seed crystal was 20%.

FIG. 4 is a SEM image of the catalyst prepared in example 6, showing the catalyst as a fusiform morphology of layered molecular sieve clusters (FIG. 4 a) and a monomer nanocrystalline cluster extension dimension of about 443nm (FIG. 4 b). The molecular sieve catalyst pore volume was 0.539m ³ Per g, surface area of 523m ² /g。

FIG. 5 is a TEM image of the catalyst prepared in example 6. From the TEM images, a large number of mesopores exist in the prepared molecular sieve catalyst (fig. 5 a); the metal particles were uniformly distributed in the catalyst particles (FIG. 5 b), and the average particle diameter of the metal particles obtained by statistics was 0.74nm (FIG. 5 c).

FIG. 6 shows the XRD pattern of the catalyst prepared in example 6, which was found to have a typical MFI molecular sieve crystalline form by comparison with pdf card (JCPDS-44-0003) in Jade software. Thanks to the encapsulation of metallic Ni inside the molecular sieve, no diffraction peaks of Ni were detected in the XRD pattern.

Examples 11 to 15

In the process of preparing the multi-stage pore structure molecular sieve packaging metal Ni catalyst, the applicant adopts different template agent dosages and different temperatures and times to bake and reduce respectively, so as to prepare a series of molecular sieve catalysts.

A certain amount of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. 7.9165g TEOS was weighed and slowly dropped into the above solution through a constant pressure separating funnel, and stirred at room temperature for 3 hours. Then, 0.12g of the molecular sieve seed crystal prepared in the previous step was added, stirring was continued at room temperature for 1 hour, then 5.7009g of the Ni complex solution prepared as described above was added, and stirring was continued at room temperature for 2 hours to obtain a synthetic solution.

Weighing 1g of the molecular sieve powder prepared in the previous step and 125mL of NH ₄ Mixing Cl (1 mol/L) solution, stirring at 85deg.C for 3 hr, washing with water to neutrality, drying at 120deg.C for 6 hr, and respectively cooling in muffle furnace air atmosphere and tube furnace H ₂ Calcining and reducing at different temperatures and times in the atmosphere to obtain the molecular sieve Ni metal catalyst with a multi-stage pore structure.

The amount of template used in example 11 was 2.0733g, the firing temperature used was 550℃and the firing time was 6h; the reduction temperature is 500 ℃ and the reduction time is 5h.

The amount of template used in example 12 was 6.2199g, the firing temperature used was 550℃and the firing time was 6h; the reduction temperature is 500 ℃ and the reduction time is 5h.

The amount of template used in example 13 was 8.2932g, the firing temperature used was 550℃and the firing time was 6h; the reduction temperature is 500 ℃ and the reduction time is 5h.

The amount of template used in example 14 was 4.1466g, the firing temperature used was 600℃and the firing time was 5h; the reduction temperature is 600 ℃ and the reduction time is 6h.

The amount of template used in example 15 was 2.0733g, the firing temperature used was 500℃and the firing time was 5 hours; the reduction temperature is 600 ℃ and the reduction time is 6h.

FIG. 7 is a SEM image of the catalyst prepared in example 11, showing that the catalyst has a spindle morphology formed by agglomerating layered molecular sieves (FIG. 7 a) and the monomer nanocrystalline clusters have an elongated axis dimension of about 768nm (FIG. 7 b). The molecular sieve catalyst pore volume is 0.525m ³ Per g, surface area 495m ² /g。

FIG. 8 is a TEM image of the catalyst prepared in example 11. From the TEM image, the prepared molecular sieve catalyst has obvious mesoporous existence (figure 8 a); the metal particles were uniformly distributed in the catalyst particles (FIG. 8 b), and the average particle diameter of the metal particles obtained by statistics was 0.77nm (FIG. 8 c).

FIG. 9 shows the XRD pattern of the catalyst prepared in example 11, which was found to have a typical MFI molecular sieve crystalline form by comparison with pdf card (JCPDS-44-0003) in Jade software. Thanks to the encapsulation of metallic Ni inside the molecular sieve, no diffraction peaks of Ni were detected in the XRD pattern.

Examples 16 to 20

In the process of preparing the multi-stage pore structure molecular sieve packaging metal Ni catalyst, the applicant respectively adopts different silicon-aluminum ratios to prepare a series of molecular sieve catalysts.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and a certain amount of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. 7.9165g TEOS was weighed and slowly dropped into the above solution through a constant pressure separating funnel, and stirred at room temperature for 3 hours. Then, 0.12g of the molecular sieve seed crystal prepared in the previous step was added, stirring was continued at room temperature for 1 hour, then 5.7009g of the Ni complex solution prepared as described above was added, and stirring was continued at room temperature for 2 hours to obtain a synthetic solution.

The mass of aluminum isopropoxide used in example 16 was 0.0408g, at which time the SiO in the synthetic hydrogel was ₂ With Al ₂ O ₃ The molar ratio of (2) was 200.

The mass of aluminum isopropoxide used in example 17 was 0.4085g, at which time the SiO in the synthetic hydrogel was ₂ With Al ₂ O ₃ The molar ratio of (2) was 20.

The mass of aluminum isopropoxide used in example 18 was 0.1634g, at which time the SiO in the synthetic hydrogel was ₂ With Al ₂ O ₃ The molar ratio of (2) was 50.

The mass of aluminum isopropoxide used in example 19 was 0.1021g, at which time the SiO in the synthetic hydrogel was ₂ With Al ₂ O ₃ The molar ratio of (2) was 80.

The mass of aluminum isopropoxide used in example 20 was 0.0678g, at which time the SiO in the synthetic hydrogel was ₂ With Al ₂ O ₃ The molar ratio of (2) was 120.

FIG. 10 is a SEM image of the catalyst of example 16, showing the catalyst as a layered molecular sieve agglomerated to form a spindle-shaped morphology (FIG. 10 a),the elongated axis dimension of the monomer nanocrystalline clusters was about 428nm (fig. 10 b). The molecular sieve catalyst pore volume is 0.527m ³ Per g, surface area 497m ² /g。

FIG. 11 is a TEM image of the catalyst prepared in example 16. From the TEM images, the molecular sieve catalyst prepared by the prepared molecular sieve catalyst has obvious mesoporous existence (fig. 11 a); the metal particles were uniformly distributed in the catalyst particles (FIG. 11 b), and the average particle diameter of the metal particles obtained by statistics was 0.78nm (FIG. 11 c).

FIG. 12 shows the XRD pattern of the catalyst prepared in example 16, which was found to have a typical MFI molecular sieve crystalline form by comparison with pdf card (JCPDS-44-0003) in Jade software. Thanks to the encapsulation of metallic Ni inside the molecular sieve, no diffraction peaks of Ni were detected in the XRD pattern.

[ example 21 ]

Applicants prepared a monolithic molecular sieve directly supported Ni catalyst as a comparative example. The layered molecular sieve was prepared in a manner similar to example 1, except that no seed crystals were added to the synthesis. When the template agent is tetrabutyl phosphonium hydroxide and the dosage of the tetrabutyl phosphonium hydroxide is the same as that of the embodiment 1, the lamellar molecular sieve or the aggregate thereof cannot be synthesized, which indicates that the addition of the seed crystal can reduce the dosage of the template agent (tetrapropyl phosphonium hydroxide or tetrapropyl phosphonium bromide) to a certain extent. On the basis, the template agent used in the layered lamellar molecular sieve adopted in the embodiment is twice the dosage of tetrabutyl phosphonium hydroxide as in the embodiment 1; in addition, the introduction of metallic Ni is realized by adopting a dipping method. As a comparative example to example 1, a specific synthesis method was as follows.

1.2385g of nickel nitrate hexahydrate (Ni (NO) ₃ ) ₂ ·6H ₂ O) was dissolved in 7.7615g of deionized water and stirred at room temperature for 1 hour to prepare a nickel nitrate impregnation solution.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. And weighing a certain amount of TEOS, slowly dripping the TEOS into the solution through a constant pressure separating funnel, and stirring at room temperature for 3 hours to obtain a synthetic solution.

Transferring the synthetic liquid obtained in the steps into a hydrothermal crystallization kettle, and performing hydrothermal crystallization for 48 hours at 130 ℃ to obtain a hydrothermal product. Washing the synthesized product with water to be neutral, drying the product for 6 hours at 120 ℃, and roasting the product for 6 hours at 550 ℃ in the atmosphere of muffle furnace air to obtain molecular sieve powder.

The molecular sieve powder prepared in the previous step is prepared according to the following weight ratio of 1:125 mass ratio to NH ₄ Cl (1 mol/L) solution was mixed, stirred at 85℃for 3 hours, washed with water to neutrality, dried at 120℃for 6 hours, and calcined at 550℃for 6 hours in a muffle air atmosphere.

1g of the calcined molecular sieve is weighed, 1.8g of the prepared impregnating solution is slowly dripped into the molecular sieve, and the mixture is continuously and uniformly stirred. Drying at 30deg.C, 60deg.C and 120deg.C for 6 hr, roasting at 550deg.C in muffle air atmosphere for 6 hr, and tubular furnace H ₂ And (3) reducing for 5 hours at 500 ℃ in the atmosphere to obtain the metal Ni catalyst loaded with the lamellar molecular sieve catalyst impregnated with 5% Ni metal.

FIG. 13 is a SEM image of the catalyst prepared in example 21, showing that the catalyst has a spherical morphology formed by agglomeration of platelet molecular sieves (FIG. 13 a) and the monomer nanocrystalline clusters have an elongated axis dimension of about 177nm (FIG. 13 b). The pore volume of the molecular sieve catalyst is 1.099m ³ Per g, surface area 635m ² /g。

FIG. 14 is a TEM image of the catalyst prepared in example 21. From the TEM images, the prepared molecular sieve catalyst is formed by stacking nano-sheets, and obvious mesopores exist (fig. 14 a); the metal particles were agglomerated on the catalyst surface (FIG. 14 b), and the average particle diameter of the metal particles obtained by statistics was 6.49nm (FIG. 14 c).

FIG. 15 shows the XRD pattern of the catalyst prepared in example 21, which was found to have a typical MFI molecular sieve crystalline form by comparison with pdf card (JCPDS-44-0003) in Jade software. Furthermore, the presence of a diffraction peak typical of metallic Ni at 2θ=44.5° can be detected in the XRD spectrum, indicating that metallic Ni is present on the surface of the binary molecular sieve support.

[ example 22 ]

The applicant adopts a seed crystal induction strategy to prepare a layered molecular sieve carrier firstly, and then adopts an impregnation method to load 5% of metal Ni to prepare a molecular sieve catalyst, which is taken as a comparative example of the hierarchical pore molecular sieve encapsulated metal Ni catalyst in the example 1.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. 7.9165g TEOS was weighed and slowly dropped into the above solution through a constant pressure separating funnel, and stirred at room temperature for 3 hours. Then 0.12g of the molecular sieve seed crystal prepared in the previous step is added, and stirring is continued for 3 hours at room temperature, so as to obtain a synthetic liquid.

The molecular sieve powder obtained in the previous step was prepared as in example 1:125 mass ratio to NH ₄ Cl (1 mol/L) solution was mixed, stirred at 85℃for 3 hours, washed with water to neutrality, dried at 120℃for 6 hours, and calcined at 550℃for 6 hours in a muffle air atmosphere.

1g of the calcined molecular sieve is weighed, 1.8g of the prepared impregnating solution is slowly dripped into the molecular sieve, and the mixture is continuously and uniformly stirred. Drying at 30deg.C, 60deg.C and 120deg.C for 6 hr, roasting at 550deg.C in muffle air atmosphere for 6 hr, and tubular furnace H ₂ And (3) reducing for 5 hours at 500 ℃ in the atmosphere to obtain the layered molecular sieve supported metal Ni catalyst impregnated with 5% Ni metal.

FIG. 16 is a SEM image of the catalyst of example 22, showing that the catalyst has a spindle morphology formed by agglomerating layered molecular sieves (FIG. 16 a) and the monomer nanocrystalline clusters have an elongated axis dimension of about 623nm (FIG. 16 b). The pore volume of the molecular sieve catalyst is 0.515m ³ Per g, surface area 481m ² /g。

Fig. 17 is a TEM image of the catalyst prepared in example 21. From the TEM images, the molecular sieve catalyst prepared by the prepared molecular sieve catalyst has obvious mesoporous existence (fig. 17 a); the metal particles were agglomerated on the catalyst surface (FIG. 17 b), and the average particle diameter of the metal particles obtained by statistics was 6.93nm (FIG. 17 c).

Example 23

The applicant simultaneously prepares the traditional microporous ZSM-5 molecular sieve. Then 5% of metal Ni is loaded by an isovolumetric impregnation method, and the catalyst is used as a comparative example of the hierarchical pore molecular sieve encapsulated metal Ni catalyst in the example 1.

12.9944g of tetrapropylammonium hydroxide (TPAOH) and 0.1331g of aluminum sulfate octadeca hydrate (Al) ₂ (SO ₄ ) ₃ ) Mixing, stirring at room temperature for 20min. 15.3496g of deionized water was then added and 8.32g of TEOS was slowly added dropwise and stirred at room temperature for 24 hours to give a synthetic solution.

1g of the calcined molecular sieve is weighed, 1.8g of the prepared impregnating solution is slowly dripped into the molecular sieve, and the mixture is continuously and uniformly stirred. Drying at 30deg.C, 60deg.C and 120deg.C for 6 hr, roasting at 550deg.C in muffle air atmosphere for 6 hr, and tubular furnace H ₂ And (3) reducing for 5 hours at 500 ℃ in the atmosphere to obtain the Ni/CZ molecular sieve catalyst impregnated with 5% Ni metal.

FIG. 18 shows a real worldSEM image of the catalyst prepared in example 22, from which the catalyst was hexagonal prism shaped (fig. 18 a), the elongated axis dimension of the monomer nanocrystalline clusters was about 254nm (fig. 18 b). The molecular sieve catalyst pore volume is 0.276m ³ Per g, surface area 315m ² And/g, which are significantly lower than the multi-pore ZSM-5 molecular sieve prepared in example 1.

FIG. 19 is a TEM image of the catalyst prepared in example 23. From the TEM images, the prepared molecular sieve catalyst was in an disordered crystal structure (fig. 19 a); the metal particles were agglomerated on the catalyst surface (FIG. 19 b), and the average particle diameter of the metal particles obtained by statistics was 7.17nm (FIG. 19 c).

Example 24

The molecular sieve catalysts of example 1, example 2, example 3, with a theoretical n (Si)/n (Al) of 100, were used to catalyze the reaction of n-decane catalytic cracking. The specific operation is that 0.2g of the catalyst and 2g of silicon carbide filler are mixed and placed in a fixed bed reaction tube, the heating rate is 5 ℃/min, n-decane is pumped in by 0.05mL/h, nitrogen gas of 10mL/min is used as carrier gas, the preheating temperature is 300 ℃, the reaction temperature is 450 ℃,450 ℃,550 ℃ and 600 ℃, and the obtained products are analyzed by gas chromatography.

As shown in fig. 20a, which shows the n-heptane conversion rule under different catalysts, it can be found that the n-decane conversion decreases at the same temperature (example 2> example 1> example 3) with increasing Ni content in the catalyst, and we speculate that this is due to the fact that Ni may interact with hydroxyl groups on the surface of the molecular sieve with increasing Ni content in the catalyst, resulting in reduced acidity. FIG. 20b shows the yields of lower olefins comprising ethylene, propylene and butylene over different catalysts. First, as the reaction temperature increases, the yield of olefin gradually increases, which is due to the increase in the conversion of n-decane caused by the increase in temperature. In addition, example 1 showed the highest low-carbon olefin yield, which was 50% or more at 600 ℃. It is shown that the low olefin yield is not solely related to the Ni loading, and that high olefin yields can be achieved only at a suitable Ni loading. FIG. 20c is a graph showing the conversion of n-decane cleavage at 600℃with time for the catalyst prepared. As can be seen from the figures, the catalysts prepared in example 1, example 2 and example 3 have good catalytic stability due to the adoption of the encapsulation structure, and can effectively inhibit migration and agglomeration of metallic Ni at high temperature.

Example 24

Molecular sieve catalysts of example 1, example 7, example 8 and example 9, with a theoretical n (Si)/n (Al) of 100, were used to catalyze the reaction of n-decane catalytic cracking. The specific operation is that 0.2g of the catalyst and 2g of silicon carbide filler are mixed and placed in a fixed bed reaction tube, the heating rate is 5 ℃/min, n-decane is pumped in by 0.05mL/h, nitrogen gas of 10mL/min is used as carrier gas, the preheating temperature is 300 ℃, the reaction temperature is 450 ℃,450 ℃,550 ℃ and 600 ℃, and the obtained products are analyzed by gas chromatography.

As shown in fig. 21a, which shows the regular n-heptane conversion rate under different catalysts, it can be found that the catalyst activity shows a tendency of rising first and falling with the rising of the seed crystal content in the synthesis liquid, and the n-decane conversion rate is from high to low at the same temperature (example 1> example 7> example 8> example 9), and we speculate that this is because the seed crystal is firstly induced to generate a layered molecular sieve structure for encapsulating metallic Ni with the rising of the seed crystal content in the synthesis liquid. However, too high a seed content results in a decrease in the structure-directing effect of the templating agent, and the structure-inducing effect of the seed is significantly enhanced. This aspect results in reduced encapsulation of metallic Ni and reduced dehydrogenation activity. On the other hand, the formation of large particle size ZSM-5 molecular sieves results in a significantly reduced hierarchical pore structure and reduced diffusion efficiency to decane. FIG. 21b shows the yields of lower olefins comprising ethylene, propylene and butylene over different catalysts. First, as the reaction temperature increases, the yield of olefin gradually increases, which is due to the increase in the conversion of n-decane caused by the increase in temperature. In addition, example 1 showed the highest low-carbon olefin yield, which was 50% or more at 600 ℃. It is stated that high olefin yields can only be achieved with the appropriate seed addition.

FIG. 21c is a graph showing the conversion of n-decane cleavage at 600℃with time for the catalyst prepared. As can be seen from the figures, the catalysts prepared in example 1, example 7, example 8 and example 9 have better catalytic stability due to the adoption of the encapsulation structure, and can effectively inhibit migration and agglomeration of metallic Ni at high temperature.

Example 25

Molecular sieve catalysts of example 1, example 21, example 22 and example 23, with a theoretical n (Si)/n (Al) of 100, were used to catalyze the reaction of n-decane catalytic cracking. The specific operation is that 0.2g of the catalyst and 2g of silicon carbide filler are mixed and placed in a fixed bed reaction tube, the heating rate is 5 ℃/min, n-decane is pumped in by 0.05mL/h, nitrogen gas of 10mL/min is used as carrier gas, the preheating temperature is 300 ℃, the reaction temperature is 450 ℃,450 ℃,550 ℃ and 600 ℃, and the obtained products are analyzed by gas chromatography.

The n-heptane conversion profile for the different catalysts is shown in FIG. 22 a. The typical layered ZSM-5 molecular sieve used in example 21 was first loaded directly with 5% Ni in higher conversion than in example 1. This is due to the higher surface area and pore volume of the layered molecular sieve itself, and the higher diffusion rate for dodecane molecules, and therefore higher activity. FIG. 22b shows a pattern of selectivity in the n-decane cleavage product over different catalysts. From the TEM image, the metal Ni is obviously aggregated on the surface particles of the two-dimensional molecular sieve, so that the yield of alkene in the catalyst cracking product of the example 21 is reduced.

Example 22 the same synthesis strategy as example 1, except for the manner of Ni introduction, the strategy used in example 1 was encapsulated in situ Ni, and the strategy used in example 22 was impregnation introduced metallic Ni. At similar specific surface area and pore volume, example 22 has higher catalytic activity at the same temperature, as shown in fig. 22a, probably due to the higher dispersity of Ni metal in example 1, stronger interaction with the support, resulting in reduced acidity of the support. It is noted that, as shown in fig. 22b, although the conversion rate is advantageous in example 22, the product of example 1 still has higher yield of lower olefins at the same temperature, which indicates that the highly dispersed Ni active center contributes to the formation of more lower olefins.

The catalyst prepared in example 23 was commercial ZSM-5 molecular sieve direct impregnation loaded with metallic Ni. The pore volume and the specific surface area are reduced to a certain extent compared with those of the examples 1, 21 and 22 due to the single micropore structure, and the n-decane conversion rate at the same temperature is the lowest. And the yield of the low-carbon olefin in the product is obviously reduced due to the fact that a large amount of metal Ni is agglomerated on the surface of the catalyst.

FIG. 22c is a graph showing the conversion of n-decane cleavage at 600℃with time for the catalyst prepared. As can be seen from the figure, the catalyst prepared in the example 1 has a packaging structure, so that migration and agglomeration of metal Ni at high temperature can be effectively inhibited, and better catalytic stability is achieved. In comparison, the stability of the catalysts used in examples 21, 22 and 23 all appeared to be significantly reduced due to migration and agglomeration of the metal active centers at the high temperature line.

Example 26

Applicants prepared a hierarchical pore structured molecular sieve encapsulated metal Co catalyst as a comparative example to the hierarchical pore molecular sieve encapsulated metal Ni catalyst in example 1.

2g of cobalt nitrate hexahydrate (Co (NO) ₃ ) ₂ ·6H ₂ O) was dissolved in 8g of deionized water and stirred at room temperature for 1 hour to prepare a nickel nitrate solution. Weighing 4.5944g N- [3- (trimethoxysilyl) propyl group]Ethylenediamine (TPE) was dissolved in 5g of the cobalt nitrate solution prepared above, and stirred at room temperature for 1 hour to prepare a Co complex solution.

4.1466g of tetrabutyl phosphonium hydroxide (TPBOH) and 0.0817g of Aluminum Isopropoxide (AIP) were weighed and mixed, stirred at room temperature for 20 minutes, then 0.52g of NaOH solution (1 mol/L) and 1.7241g of deionized water were added dropwise thereto, and stirred at room temperature for 10 minutes. 7.9165g TEOS was weighed and slowly dropped into the above solution through a constant pressure separating funnel, and stirred at room temperature for 3 hours. Then, 0.12g of the molecular sieve seed crystal prepared in the previous step was added, stirring was continued at room temperature for 1 hour, then 5.6701g of the Co complex solution prepared above was added, and stirring was continued at room temperature for 2 hours to obtain a synthetic solution.

Transferring the synthetic liquid obtained in the steps into a hydrothermal crystallization kettle, and performing hydrothermal crystallization for 48 hours at 130 ℃ to obtain a hydrothermal product. Washing the synthesized product with water to be neutral, drying the product for 6 hours at 120 ℃, and roasting the product for 6 hours at 550 ℃ in the atmosphere of muffle furnace air to obtain the molecular sieve powder for encapsulating CoO.

Weighing 1g of the molecular sieve powder prepared in the previous step and 125mL of NH ₄ Cl (1 mol/L) solution is mixed, stirred for 3 hours at 85 ℃, washed to be neutral by water, dried for 6 hours at 120 ℃, baked for 6 hours at 550 ℃ in a muffle air atmosphere, and tubular furnace H ₂ And (3) reducing for 5 hours at 500 ℃ in the atmosphere to obtain the molecular sieve Co metal catalyst with a multistage pore structure.

The molecular sieve catalysts of example 1 and example 26, at a theoretical n (Si)/n (Al) of 100, were used to catalyze the reaction of n-decane catalytic cracking. The specific operation is that 0.2g of the catalyst and 2g of silicon carbide filler are mixed and placed in a fixed bed reaction tube, the heating rate is 5 ℃/min, n-decane is pumped in by 0.05mL/h, nitrogen gas of 10mL/min is used as carrier gas, the preheating temperature is 300 ℃, the reaction temperature is 450 ℃,450 ℃,550 ℃ and 600 ℃, and the obtained products are analyzed by gas chromatography.

The n-heptane conversion profile for the different catalysts is shown in FIG. 23 a. It can be seen that the in situ encapsulated 5% Ni used in example 1 produced layered ZSM-5 molecular sieve n-decane conversion was higher than in example 26. Example 26 uses the same synthetic strategy as example 1, except that the type of encapsulated metal, example 1 uses the strategy of encapsulating the metal Ni in situ, and example 26 uses the strategy of encapsulating the metal Co in situ. Example 1 has higher catalytic activity at the same temperature at similar specific surface area and pore volume. Meanwhile, as shown in fig. 23b, the product of example 1 still has higher yield of low-carbon olefin at the same temperature. The transition metal elements of the VIII groups in the periodic table of the elements of the same genus of Ni and Co have the capability of activating C-H bonds in hydrocarbon molecules, which shows that the paths of high-dispersion Ni and Co in the catalytic cracking reaction are different, and the layered ZSM-5 encapsulated Ni catalyst with a multi-stage pore structure is more beneficial to generating olefin.

From the analysis, the molecular sieve encapsulated Ni metal catalyst based on the fusiform aggregate morphology formed by the layered ZSM-5 body has a proper pore structure and a high-dispersion metal Ni active center. The rapid diffusion channel constructed by the multistage pore structure is combined with Ni metal in-situ dehydrogenation, so that the high low-carbon olefin yield is shown in the catalytic cracking reaction of heavy oil. In addition, due to the finite field effect of the molecular sieve pore canal, the metal Ni has higher dispersity and thermal stability, and also has better catalytic stability in catalytic cracking reaction.

Claims

1. A method of preparing a molecular sieve catalyst for catalyzing the molecular cracking of heavy oil, the method comprising the steps of:

(1) Mixing Ni source solution with a silanization reagent, and stirring at room temperature to obtain Ni complex solution; mixing a silicon source, a template agent and water, stirring for a period of time at room temperature, performing hydrothermal treatment, washing with water after the hydrothermal treatment is finished, and sequentially drying and roasting to obtain a nano molecular sieve seed crystal, wherein the template agent is one of tetrapropylammonium hydroxide and tetrapropylammonium bromide; the silane reagent is N- [3- (trimethoxysilyl) propyl ] ethylenediamine; the molar ratio of Ni to N- [3- (trimethoxysilyl) propyl ] ethylenediamine in the Ni complex is 1/10-1/1;

(2) Mixing a silicon source, a template agent, an alkali source, an aluminum source and water, stirring for a period of time at room temperature, then adding the molecular sieve seed crystal prepared in the step (1), continuing stirring for a period of time at room temperature, then adding the Ni complex solution obtained in the step (1), and stirring for a period of time to obtain a synthetic solution, wherein the template agent is one of tetrabutyl phosphonium hydroxide and tetrabutyl phosphonium bromide, and Si in the seed crystal accounts for 1% -20% of the total Si content;

2. The method of claim 1, wherein in step (1), the Ni source comprises one or both of nickel nitrate or nickel chloride.

3. The method of claim 1, wherein in step (1), the silicon source comprises one of a silica gel, fumed silica, an inorganic silicate, an organosilicate, a white carbon black, or silicic acid; siO (SiO) ₂ The molar ratio of the template agent to the water is 100 (5-50): 500-3000.

4. The method of claim 1, wherein in step (2), the silicon source comprises one of a silica gel, fumed silica, an inorganic silicate, an organosilicate, a white carbon black, or silicic acid; the aluminum source comprises one or more of an organic aluminum compound, an inorganic aluminum salt or a complex thereof; the alkali source is one or more of sodium hydroxide or potassium hydroxide.

5. The preparation method according to claim 1, wherein in the step (1), the temperature of the hydrothermal treatment is 100-180 ℃, and the time of the hydrothermal treatment is 12-72 h; the temperature of the roasting treatment is 300-600 ℃, and the time of the roasting treatment is 2-12 hours.

6. The preparation method according to claim 1, wherein in the step (3), the temperature of the hydrothermal treatment is 100-200 ℃, and the time of the hydrothermal treatment is 12-120 hours; the temperature of the roasting treatment is 300-600 ℃, and the time of the roasting treatment is 2-12 hours.

7. The preparation method according to claim 1, wherein in the step (4), the ion exchange temperature is 70-95 ℃, the ion exchange time is 2-12 h, the roasting temperature is 300-650 ℃, the roasting time is 4-12 h, and the roasting is performed in an air atmosphere; the reduction temperature is 450-650 ℃, the reduction time is 4-12 h, and the reduction is carried out in a hydrogen atmosphere.

8. The catalyst for catalyzing cracking reaction of hydrocarbon compounds, which is prepared by the preparation method according to any one of claims 1 to 7.

9. The use of the catalyst of claim 8 for catalyzing the cracking of hydrocarbon compounds to produce light olefins.