Preparation method of catalytic cracking reaction composite metal catalyst and application thereof in preparation of vinylidene chloride

Abstract

The present application belongs to the technical field of catalysts, and particularly relates to a preparation method of a catalytic cracking reaction composite metal catalyst and application thereof in preparation of vinylidene chloride, the preparation method of the catalytic cracking reaction composite metal catalyst comprising the following steps: (1) mixing a chitosan solution with an acetic acid solution, adjusting pH to obtain a mixed solution, and then adding a zinc lactate solution into the mixed solution and mixing uniformly to obtain a zinc chelate solution; (2) mixing the zinc chelate solution, an aluminum-containing compound, a silicon-containing compound and a template agent to form a slurry, forming molecular sieve particles through spray granulation, crystallizing, washing and drying to obtain zinc-containing molecular sieve microspheres; (3) mixing cesium sulfate, oleic acid and octadecene to obtain a cesium oleate solution through a mixing reaction; and (4) dispersing the zinc-containing molecular sieve microspheres into the cesium oleate solution to react, and obtaining the catalytic cracking reaction composite metal catalyst. The present application optimizes process conditions in the preparation process, and forms a perfect catalytic system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a preparation method of a catalytic cracking reaction composite metal catalyst and application thereof in preparation of vinylidene chloride. BACKGROUND

[0002] Vinylidene chloride is a colorless oily liquid, and its molecular formula is C2H2Cl2. Vinylidene chloride has a pungent odor, a melting point of -122℃, a boiling point of 31.2℃, is insoluble in water, and soluble in many organic solvents such as ethanol and diethyl ether. Vinylidene chloride has two symmetrical chlorine atoms on one carbon, which makes vinylidene chloride have relatively active chemical properties. Vinylidene chloride is an important monomer in the polymer synthesis industry, and is commonly used to produce latex and resin products.

[0003] Polyvinylidene chloride is a copolymer formed by polymerization of vinylidene chloride, and is currently widely used in food, medicine, tobacco, paint and other fields. Polyvinylidene chloride resin is mainly used in three aspects: first, polyvinylidene chloride resin for fibers, mainly used in seat cushions, artificial turf, fishing nets, flame-retardant cloth and the like; second, polyvinylidene chloride resin for solution type coating, mainly used in paint, adhesive and viscous agent; and third, polyvinylidene chloride resin multilayer co-extruded film, mainly used in packaging of food and beverages. Polyvinylidene chloride latex is a copolymer produced by copolymerization of vinylidene chloride and acrylate monomers, and is mainly used in packaging of pharmaceuticals, beverages, tobacco and the like.

[0004] For preparation of vinylidene chloride, the main methods currently include 1,1,2-trichloroethane alkaline hydrolysis method, 1,2-dichloroethane chlorination method, chloroethylene hydrogen chlorination method, chloroethylene chlorination method, ethane chlorination method and the like. Because the blocking performance of polyvinylidene chloride is far superior to other similar products, polyvinylidene chloride has a wide range of applications, and therefore the potential market demand for vinylidene chloride is large. Therefore, a synthesis process route with less by-products, simple process, environmental friendliness, mild reaction conditions and green atom economy is the key to production of vinylidene chloride. Among them, the method of producing vinylidene chloride by using 1,1,2-trichloroethane gas phase catalytic dehydrochlorination does not require additional investment of alkali, and does not produce high-salt wastewater, and therefore this method is worth further research.

[0005] 1,1,2-trichloroethane is a colorless transparent and non-flammable liquid with characteristics similar to chloroform, has a melting point of -35℃, a boiling point of 113-114℃, is insoluble in water, and is miscible with many organic solvents. 1,1,2-trichloroethane can be prepared by catalytic chlorination of ethane or ethylene, and can be prepared by further chlorination of 1,2-dichloroethane in industry.

[0006] The traditional 1,1,2-trichloroethane base hydrolysis method for preparing vinylidene chloride mainly adopts alkali solution and 1,1,2-trichloroethane to react at normal pressure to remove one molecule of hydrogen chloride to generate vinylidene chloride and the corresponding salt solution, and the method for preparing vinylidene chloride has serious environmental pollution; the 1,2-dichloroethane chlorination method generates 1,1,2-trichloroethane by chlorination reaction of 1,2-dichloroethane and chlorine, and then the 1,1,2-trichloroethane is refined and subjected to base hydrolysis saponification to obtain vinylidene chloride, and the method has harsh reaction conditions and more by-products; the chloroethylene hydrochlorination method adopts thermal cracking to remove hydrogen chloride, and the process flow is long, and more equipment is required, so the economic investment is large; the chloroethylene chlorination method catalytically generates 1,1,2-trichloroethane by introducing chloroethylene and chlorine into a reactor, and then the 1,1,2-trichloroethane is subjected to saponification reaction to generate vinylidene chloride. The ethane chlorination method uses ethane as a raw material, and high-temperature chlorination generates a mixture containing hydrogen chloride, chloroethane, chloroethylene and vinylidene chloride, and then the products are separated by rectification, and the process flow is long, the energy consumption is large, and the investment cost is high. The 1,1,2-trichloroethane gas phase catalytic dehydrochlorination method does not generate waste water at all, and meets the green environmental protection concept.

[0007] Chinese patent CN112774591A discloses a continuous preparation system and method of vinylidene chloride, which couples two-stage high gravity reactors, and uses steam stripping to remove the product vinylidene chloride and water vapor from the reaction system in the form of an azeotrope. The method has more by-products and low conversion rate, and the waste water pollution is large, and the subsequent environmental protection treatment cost is high.

[0008] At present, the 1,1,2-trichloroethane base hydrolysis method for preparing vinylidene chloride still has many problems, such as many side reactions, rectification and purification for refining, and large energy consumption; and the base hydrolysis method inevitably needs to invest a large amount of alkali solution, and generates salt-containing waste water in the generation process, which pollutes the environment and has high subsequent treatment cost.

[0009] The existing vinylidene chloride preparation technology has a series of key bottleneck problems such as long process flow, unfriendly production process environment, many by-products and high energy consumption, so it is urgent to develop an environment-friendly high-efficiency catalyst for preparing vinylidene chloride. SUMMARY

[0010] In view of the deficiencies in the prior art, the technical problem to be solved by the present application is to provide a preparation method of a catalytic cracking reaction composite metal catalyst, so as to obtain a composite metal catalyst with better catalytic performance; and the application also provides an application of the catalytic cracking reaction composite metal catalyst in preparing vinylidene chloride.

[0011] The technical scheme adopted by the present application to solve the technical problem is:

[0012] The preparation method of the catalytic cracking reaction composite metal catalyst comprises the following steps:

[0013] (1) mixing a chitosan solution with an acetic acid solution, adjusting pH to obtain a mixed solution, and then adding a zinc lactate solution into the mixed solution and mixing uniformly to obtain a zinc chelate solution;

[0014] (2) mixing the zinc chelate solution, an aluminum-containing compound, a silicon-containing compound and a template agent to form a slurry, forming molecular sieve particles by spray granulation, and then placing the molecular sieve particles into an alkaline solution for crystallization, washing, drying to obtain zinc-containing molecular sieve microspheres;

[0015] (3) mixing cesium sulfate, oleic acid and octadecene under nitrogen protection to obtain a cesium oleate solution;

[0016] (4) dispersing the zinc-containing molecular sieve microspheres into the cesium oleate solution under nitrogen protection for reaction, filtering, washing, shaping, drying and calcining to obtain the catalytic cracking reaction composite metal catalyst.

[0017] In the step (1), the concentration of the acetic acid solution is 10-14 wt%, the concentration of the chitosan solution is 0.5-2 wt%, the mass ratio of acetic acid in the acetic acid solution to chitosan in the chitosan solution is 1:0.05-0.15, the pH is adjusted by using a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 0.1-0.5 M, and the pH value is 6-7.

[0018] In the step (1), the mass ratio of zinc lactate in the zinc lactate solution to chitosan in the chitosan solution is 1:0.05-0.11, the concentration of the zinc lactate solution is 0.1-2 M, the mixing temperature is room temperature, and the mixing time is 2-6 h.

[0019] In the step (2), the aluminum-containing compound is aluminum isopropoxide, the silicon-containing compound is tetraethyl orthosilicate, the template agent is tetrapropylammonium bromide, the mass ratio of the zinc chelate solution, the aluminum-containing compound, the silicon-containing compound and the template agent is 0.01-0.5:1:40-60:0.5-1.5, and the mixing time is 0.5-3 h.

[0020] In the step (2), the average particle size of the molecular sieve particles is 25-50 µm, the alkaline solution is a tetrapropylammonium hydroxide solution, the concentration of the alkaline solution is 2-3 wt%, the ratio of the alkaline solution to the molecular sieve particles is 1-20:1, the alkaline solution is measured by ml, and the molecular sieve particles are measured by g; the crystallization temperature is 150-190 ℃, the crystallization time is 24-72 h, and the drying temperature is 80-150 ℃.

[0021] In the step (2), the average particle size of the molecular sieve particles is 25-50 µm, the alkaline solution is a tetrapropylammonium hydroxide solution, the concentration of the alkaline solution is 2-3 wt%, the ratio of the alkaline solution to the molecular sieve particles is 1-20:1, the alkaline solution is measured by ml, and the molecular sieve particles are measured by g; the crystallization temperature is 150-190 ℃, the crystallization time is 24-72 h, and the drying temperature is 80-150 ℃.

[0022] The mass ratio of cesium sulfate, oleic acid and octadecene in the step (3) is 1:25-100:0.25-0.5; the mixing reaction temperature is 80-150 DEG C, and the mixing reaction time is 1.5-2.5h.

[0023] The ratio of the zinc-containing molecular sieve microspheres and the cesium oleate solution in the step (4) is 1:1-10, the zinc-containing molecular sieve microspheres are measured in g, and the cesium oleate solution is measured in ml; the reaction temperature is 25-30 DEG C, the reaction time is 0.5-6h, the calcination temperature is 450-650 DEG C, and the calcination time is 4-6h.

[0024] The application of the catalytic cracking reaction composite metal catalyst prepared by the preparation method in the preparation of vinylidene chloride is as follows: 1,1,2-trichloroethane is mixed with nitrogen to obtain a mixed gas, the catalytic cracking reaction composite metal catalyst is added into the mixed gas to perform a cracking reaction, and then vinylidene chloride product is obtained by condensation after the reaction.

[0025] The mass ratio of the 1,1,2-trichloroethane and nitrogen is 1:100-1000, and the volume space velocity of the mixed gas is 25-30min -1 .

[0026] The cracking reaction temperature is 140-160 DEG C, and the cracking reaction pressure is 0.3-2MPa.

[0027] The application has the beneficial effects that:

[0028] The application firstly mixes the chitosan solution with the acetic acid solution, the role of the acetic acid is to provide a suitable acidic dissolution environment for the chitosan, the addition of the acetic acid facilitates the breaking of the strong hydrogen bond force between the chitosan molecules, so that the chitosan is quickly dispersed and dissolved in water, after the pH is adjusted to 6-7, the chitosan fully contacts with the zinc ions and a coordination reaction occurs, forming a chelate, which improves the reaction efficiency of the chitosan and the zinc ions; in this process, due to the special spatial structure of the chelate, a steric hindrance effect is generated, which significantly increases the distance between the zinc ions, thereby effectively improving the dispersion uniformity of the zinc ions in the zinc-containing molecular sieve microspheres. These highly dispersed zinc ions are connected with each other inside the zinc-containing molecular sieve microspheres, and a grid-like structure is constructed, which provides a favorable framework foundation for the subsequent uniform dispersion and filling of cesium ions; during the forming process of the zinc-containing molecular sieve microspheres, the chitosan-zinc lactate chelate can be uniformly distributed in the entire molecular sieve particle system, which ensures the high uniformity of the zinc-containing molecular sieve microspheres in the macroscopic morphology, plays a key role in the catalytic process, and promotes the formation of rich and interconnected pore structures inside and outside the zinc-containing molecular sieve microspheres, which greatly increases the specific surface area and pore volume of the molecular sieve, so that the molecular sieve can more efficiently and quickly adsorb and desorb the reactants during the catalytic reaction, thereby significantly improving the catalytic performance of the composite metal catalyst, and providing a more excellent material basis for related catalytic applications.

[0029] The application converts cesium sulfate into cesium oleate, and then introduces oleate ions into the zinc-containing molecular sieve microspheres through loading; the oleate is dispersed on the surface of the pore of the zinc-containing molecular sieve microspheres through adsorption, and then the cesium oleate and the chitosan-zinc lactate chelate on the molecular sieve are further dispersed through intermolecular forces, the action mode of the two is relatively mild, which can effectively avoid the excessive loading of active components in the traditional loading mode. At the same time, the special molecular structure of the cesium oleate enables it to exhibit good dispersity in the gap of the zinc-containing molecular sieve microspheres, which can significantly reduce the problem of waste of active sites caused by aggregation, thereby greatly improving the effective utilization rate of the active sites of the molecular sieve. In the zinc-containing molecular sieve microspheres, the cesium ions in the cesium oleate can synergize with the previously introduced zinc ions, and the zinc ions can regulate the active center structure and electron cloud distribution of the cesium ions in the catalyst, thereby improving the activity of the composite metal catalyst, improving the conversion efficiency of raw materials in the reaction process of synthesizing vinylidene chloride, optimizing the selectivity of the reaction, and shortening the reaction time, so that the catalyst exhibits more excellent catalytic performance in the synthesis of vinylidene chloride. The preparation process of the application optimizes the process conditions, improves the product quality, and forms a perfect catalytic system. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the SEM diagram of the catalytic cracking reaction composite metal catalyst prepared in Example 1 of the application. DETAILED DESCRIPTION

[0031] The application will be further described in connection with the following examples.

[0032] Example 1

[0033] The preparation method of the catalytic cracking reaction composite metal catalyst comprises the following steps:

[0034] (1) 500 g of a 1 wt% chitosan solution and 500 g of a 12 wt% acetic acid solution are mixed at room temperature for 3 h, and after being fully dissolved, a 0.2 M sodium hydroxide solution is used to adjust the pH to 6.5 to obtain a mixed solution, and then 400 mL of a 0.5 M zinc lactate solution is added to the mixed solution and fully mixed at room temperature for 5 h to obtain a zinc chelate solution;

[0035] (2) 10 g of the zinc chelate solution, 100 g of aluminum isopropoxide, 5000 g of tetraethyl orthosilicate, and 100 g of tetrapropylammonium bromide are mixed for 1 h to form a slurry, and the slurry is formed into molecular sieve particles with an average particle size of 30 μm by spray granulation, and then 1000 g of the molecular sieve particle is placed into a 2.5 wt% 10000 ml tetrapropylammonium hydroxide solution and crystallized at 150 °C for 48 h, and washed to neutral, and dried at 80 °C to obtain zinc-containing molecular sieve microspheres;

[0036] (3) 10 g of cesium sulfate, 500 g of oleic acid, and 5 g of octadecene are mixed at 150 °C for 1.5 h under nitrogen protection to obtain a cesium oleate solution;

[0037] (4) 500 g of the zinc-containing molecular sieve microspheres are dispersed into 2500 ml of the cesium oleate solution and reacted at 30 °C for 2 h under nitrogen protection, and then filtered and washed, kneaded and shaped, and dried, and calcined at 500 °C for 5 h to obtain a catalytic cracking reaction composite metal catalyst, and a SEM image thereof is shown in Figure 1

[0038] Application of the catalytic cracking reaction composite metal catalyst in the preparation of vinylidene chloride:

[0039] 200 g of the catalytic cracking reaction composite metal catalyst is put into a DN25 fixed bed reactor, the effective packing height is 0.3 meters, and 10 cm high quartz sand is laid on the upper and lower parts of the bed; nitrogen is used to replace for 30 min, and then a mixture of 1,1,2-trichloroethane and nitrogen with a mass ratio of 1:1000 is continuously introduced, and the reaction is carried out at 150 °C and an empty speed of 25 min -1 The pressure in the fixed bed reactor is 2 MPa, and after the reaction, the gas is condensed to obtain a vinylidene chloride liquid; the conversion rate of 1,1,2-trichloroethane is 38.28%, and the selectivity of vinylidene chloride is 88.23%.

[0040] Example 2 ​

[0041] A preparation method of a catalytic cracking reaction composite metal catalyst, comprising the following steps:

[0042] (1) 500g of a 2wt% chitosan solution is mixed with 500g of a 15wt% acetic acid solution at room temperature for 5h, and after being fully dissolved, a 0.1M sodium hydroxide solution is used to adjust the pH to 7, to obtain a mixed solution, and then 400mL of a 2M zinc lactate solution is added to the mixed solution and fully mixed at room temperature for 6h, to obtain a zinc chelate solution.

[0043] (2) 50g of the zinc chelate solution, 100g of aluminum isopropoxide, 6000g of tetraethyl orthosilicate, and 150g of tetrapropylammonium bromide are mixed for 3h to form a slurry, which is spray granulated to form molecular sieve particles with an average particle size of 25μm, and then 1000g of the molecular sieve particle is placed in a 3wt%, 20000ml tetrapropylammonium hydroxide solution and crystallized at 170℃ for 72h, washed to neutral, and dried at 150℃ to obtain zinc-containing molecular sieve microspheres;

[0044] (3) 10g of cesium sulfate, 250g of oleic acid, and 3.5g of octadecene are mixed at 80℃ for 2h to obtain a cesium oleate solution under nitrogen protection;

[0045] (4) 500g of the zinc-containing molecular sieve microspheres is dispersed into 5000ml of the cesium oleate solution and reacted at 28℃ for 6h under nitrogen protection, and then filtered and washed, kneaded and shaped, and dried, and then calcined at 650℃ for 4h to obtain a catalytic cracking reaction composite metal catalyst.

[0046] Application of the catalytic cracking reaction composite metal catalyst in the preparation of vinylidene chloride:

[0047] 200g of the catalytic cracking reaction composite metal catalyst is put into a DN25 fixed bed reactor, with an effective packing height of 0.4m, and 10cm high quartz sand is laid on the top and bottom of the bed; nitrogen is used to replace for 50min, and then a mixture of 1,1,2-trichloroethane and nitrogen with a mass ratio of 1:500 is continuously introduced, and the reaction is carried out at 140℃ and an empty speed of 30min -1 The pressure in the fixed bed reactor is 0.3MPa, and after the reaction, the gas is condensed to obtain a vinylidene chloride liquid; the conversion rate of 1,1,2-trichloroethane is 37.62%, and the selectivity of vinylidene chloride is 87.02%.

[0048] Example 3

[0049] A preparation method of a catalytic cracking reaction composite metal catalyst, comprising the following steps:

[0050] (1) 500 g of a 0.5 wt% chitosan solution and 500 g of a 10 wt% acetic acid solution were mixed at room temperature for 2 h, and after complete dissolution, the pH was adjusted to 6 using a 0.5 M sodium hydroxide solution to obtain a mixed solution, and then 1100 mL of a 0.1 M zinc lactate solution was added to the mixed solution and mixed thoroughly at room temperature for 2 h to obtain a zinc chelate solution.

[0051] (2) 1 g of the zinc chelate solution, 100 g of aluminum isopropoxide, 4000 g of tetraethyl orthosilicate and 50 g of tetrapropylammonium bromide were mixed for 0.5 h to form a slurry, which was spray granulated to form molecular sieve particles with an average particle size of 50 μm, and then 1000 g of the molecular sieve particles were placed in a 2 wt% 1000 mL tetrapropylammonium hydroxide solution and crystallized at 190°C for 24 h, washed to neutral, and dried at 120°C to obtain zinc-containing molecular sieve microspheres;

[0052] (3) 10 g of cesium sulfate, 1000 g of oleic acid and 2.5 g of octadecene were mixed at 120°C for 2.5 h under nitrogen to obtain a cesium oleate solution;

[0053] (4) 500 g of the zinc-containing molecular sieve microspheres were dispersed in 500 mL of the cesium oleate solution and reacted at 25°C for 0.5 h under nitrogen, and then filtered and washed, kneaded and dried, and calcined at 450°C for 6 h to obtain a catalytic cracking reaction composite metal catalyst.

[0054] Use of the catalytic cracking reaction composite metal catalyst in the preparation of vinylidene chloride:

[0055] 200 g of the catalytic cracking reaction composite metal catalyst was placed in a DN25 fixed bed reactor with an effective packing height of 0.4 m and 10 cm of quartz sand on the top and bottom of the bed, and then replaced with nitrogen for 20 min, and then a mixture of 1,1,2-trichloroethane and nitrogen with a mass ratio of 1:100 was continuously introduced at 160°C and an airspeed of 27 min -1 The pressure in the fixed bed reactor was 1 MPa, and after the reaction, the gas was condensed to obtain a vinylidene chloride liquid; the conversion rate of 1,1,2-trichloroethane was 40.71%, and the selectivity of vinylidene chloride was 82.86%.

[0056] Comparative Example 1

[0057] In the preparation process of the catalytic cracking reaction composite metal catalyst, no chitosan solution was added in step (1), and the remaining steps were the same as in Example 1.

[0058] The conversion rate of 1,1,2-trichloroethane was 22.61%, and the selectivity of vinylidene chloride was 58.08%.

[0059] Comparative Example 2

[0060] In the step (1) of the preparation process of the catalytic cracking composite metal catalyst, no acetic acid solution is added, and the remaining steps are the same as those in Example 1.

[0061] The conversion rate of 1,1,2-trichloroethane is 27.53%, and the selectivity of vinylidene chloride is 63.82%.

[0062] Comparative Example 3

[0063] In the preparation process of the catalytic cracking composite metal catalyst, steps (3) and (4) are omitted, and the zinc-containing molecular sieve microspheres are directly used as the catalyst, and the remaining steps are the same as those in Example 1.

[0064] The conversion rate of 1,1,2-trichloroethane is 20.75%, and the selectivity of vinylidene chloride is 47.98%.

[0065] Comparative Example 4

[0066] In the preparation process of the catalytic cracking composite metal catalyst, step (3) is omitted, and the zinc-containing molecular sieve microspheres are added into the cesium sulfate solution in step (4), and the remaining steps are the same as those in Example 1.

[0067] The conversion rate of 1,1,2-trichloroethane is 21.24%, and the selectivity of vinylidene chloride is 55.39%.

[0068] As can be seen from the above, the composite metal catalyst has excellent catalytic performance. As can be seen from Comparative Example 1 and Comparative Example 2 compared with Example 1, without adding chitosan, the zinc chelate cannot be formed, the catalyst prepared due to the lack of a special spatial structure cannot form a steric hindrance effect, greatly reducing the catalytic performance of the catalyst, and without adding acetic acid, the chitosan is difficult to disperse and dissolve in water due to strong intermolecular hydrogen bonding, and cannot fully contact and react with zinc ions during the subsequent coordination reaction, so that the formation process of the chelate is hindered. As can be seen from Comparative Example 3 and Example 1, only using a zinc-containing catalyst cannot achieve high 1,1,2-trichloroethane conversion rate and vinylidene chloride selectivity. As can be seen from Comparative Example 4 and Example 1, using sulfate for loading is not as mild as the action of oleate, which can cause excessive loading and affect the catalytic activity. The interaction between the oleate and the surface of the molecular sieve in the application can effectively avoid the phenomenon of excessive loading of active components in the traditional loading method. In addition, the special molecular structure of cesium oleate makes it exhibit good dispersity in the gap of the zinc-containing molecular sieve microspheres.

Claims

1. A method for preparing a composite metal catalyst for catalytic cracking reaction, characterized in that, Includes the following steps: (1) Mix chitosan solution and acetic acid solution, adjust pH to 6-7 to obtain a mixture, then add zinc lactate solution to the mixture and mix well to obtain zinc chelate solution; (2) A zinc chelate solution, an aluminum-containing compound, a silicon-containing compound and a template agent are mixed to form a slurry, which is then spray-granulated to form molecular sieve particles. The particles are then placed in an alkaline solution for crystallization, washed and dried to obtain zinc-containing molecular sieve microspheres. (3) Under nitrogen protection, cesium sulfate, oleic acid and octadecene are mixed and reacted to obtain a cesium oleate solution; (4) Under nitrogen protection, zinc-containing molecular sieve microspheres are dispersed in cesium oleate solution for reaction, filtered, washed, shaped, dried and calcined to obtain a composite metal catalyst for catalytic cracking reaction.

2. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (1), the concentration of acetic acid solution is 10-14wt%, the concentration of chitosan solution is 0.5-2wt%, the mass ratio of acetic acid in acetic acid solution to chitosan in chitosan solution is 1:0.05-0.15, and the pH is adjusted by sodium hydroxide solution with a concentration of 0.1-0.5M.

3. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (1), the mass ratio of zinc lactate in the zinc lactate solution to chitosan in the chitosan solution is 1:0.05-0.11, the concentration of zinc lactate solution is 0.1-2M, the mixing temperature is room temperature, and the mixing time is 2-6h.

4. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (2), the aluminum-containing compound is aluminum isopropoxide, the silicon-containing compound is tetraethyl orthosilicate, the template agent is tetrapropylammonium bromide, and the mass ratio of zinc chelate solution, aluminum-containing compound, silicon-containing compound and template agent is 0.01-0.5:1:40-60:0.5-1.5, and the mixing time is 0.5-3h.

5. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (2), the average particle size of the molecular sieve particles is 25-50 μm, the alkaline solution is tetrapropylammonium hydroxide solution, and the concentration of the alkaline solution is 2-3 wt%; the ratio of alkaline solution to molecular sieve particles is 1-20:1, the alkaline solution is measured in ml, and the molecular sieve particles are measured in g; the crystallization temperature is 150-190℃, the crystallization time is 24-72 h, and the drying temperature is 80-150℃.

6. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (3), the mass ratio of cesium sulfate, oleic acid and octadecene is 1:25-100:0.25-0.5; the mixing reaction temperature is 80-150℃ and the mixing reaction time is 1.5-2.5h.

7. The method for preparing the composite metal catalyst for catalytic cracking reaction according to claim 1, characterized in that, In step (4), the ratio of zinc-containing molecular sieve microspheres to cesium oleate solution is 1:1-10, with the zinc-containing molecular sieve microspheres measured in g and the cesium oleate solution measured in ml; the reaction temperature is 25-30℃, the reaction time is 0.5-6h, the calcination temperature is 450-650℃, and the calcination time is 4-6h.

8. The application of a composite metal catalyst obtained by any one of the preparation methods described in claims 1-7 in the preparation of vinylidene chloride, characterized in that, 1,1,2-trichloroethane was mixed with nitrogen to obtain a mixed gas. A composite metal catalyst for catalytic cracking was added to the mixed gas to carry out the cracking reaction. After the reaction, the product was obtained by condensation.

9. The application according to claim 8, characterized in that, The mass ratio of 1,1,2-trichloroethane to nitrogen is 1:100-1000, and the volume hourly space velocity (VHSV) of the mixture is in the range of 25-30 min. -1 .

10. The application according to claim 8, characterized in that, The pyrolysis reaction temperature is 140-160℃, and the pyrolysis reaction pressure is 0.3-2MPa.

Images