Preparation method and application of porous tungsten boride catalyst

Abstract

The invention discloses a preparation method and application of a porous tungsten boride catalyst. According to different precursors, fluxes and preparation temperature selections, the prepared catalyst has different microscopic morphologies, can be directly used as a catalyst, and can also be used as a catalyst carrier, and has good catalytic activity; when applied to a dehydrochlorination reaction, it exhibits excellent catalytic performance, can be used as a wear-resistant, corrosion-resistant and electrode material in a strong acid, strong alkali and high temperature environment, has high and stable mechanical strength, high temperature resistance, strong acid and strong alkali corrosion resistance, high specific surface area, easily activated surface, good thermal and electrical conductivity, low production cost, little harm to the environment, and has high research value.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a preparation method and application of a porous tungsten boride catalyst. Background Art

[0002] As an important synthetic monomer in industry, vinylidene chloride is widely used in many fields. The gas-phase catalytic dehydrochlorination of 1,1,2-trichloroethane to prepare vinylidene chloride has significant advantages such as high atomic utilization, simple process flow, clean and environmental protection. Existing catalysts for preparing vinylidene chloride in the gas phase have significant defects such as poor reaction activity and short life. Due to cost issues, the high price of metal catalysts limits the further promotion and application of such catalysts; the mechanical strength of the activated carbon-supported catalyst is very poor, resulting in the collapse and sintering of the catalyst pores during long-term use, resulting in catalyst loss and serious pollution to the environment. Therefore, it is of great industrial application value to develop a cheap, effective, durable and environmentally friendly catalyst to replace the existing metal-based catalysts. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention creatively conceives a preparation method and application of a porous tungsten boride catalyst. The pores of the porous tungsten boride catalyst are mainly composed of micropores and mesopores, with a diverse microstructure and a surface area of ​​50-2500m 2 / g. Depending on the selection of different precursors, flux and preparation temperature, the prepared catalyst has different microscopic morphology. When used in dehydrochlorination reaction, it exhibits excellent catalytic performance and can be used as wear-resistant, corrosion-resistant and electrode materials in strong acid, strong alkali and high temperature environments.

[0004] One of the technical solutions used to implement the present invention is: a method for preparing a porous tungsten boride catalyst, wherein the chemical formula of the porous tungsten boride catalyst is W x B y , wherein x=0-3, y=1-12, characterized in that the preparation method comprises the following steps:

[0005] 1) The tungsten precursor and the boron precursor are mixed in a ratio of tungsten:boron=1:0.5 to 1:12, and the mixture is fully mixed with flux A and stirred to obtain a uniform mixture;

[0006] 2) The mixture stirred evenly in step 1) is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , forming a solid solution state and obtaining a solid solution;

[0007] 3) Under the protection of inert gas, the solid solution in step 2) is cooled to 25° C. to 120° C.;

[0008] 4) subjecting the solid solution after cooling in step 3) to mechanical ball milling, wherein the ball milling time is 3 h to 6 h, the vacuum degree is 100 Pa to 100000 Pa, and the ball milling speed is 60 to 300 r / min to obtain a ball milled mixture;

[0009] 5) Under inert gas conditions, the ball-milled mixture in step 4) is subjected to high-temperature calcination at a temperature of 200 to 1800° C. for a time of 2 to 12 hours, and then cooled to 25° C.;

[0010] 6) Grinding the mixture obtained in step 5) into powder of 10-200 mesh, and then pressing into blocks.

[0011] Furthermore, the tungsten-containing precursor in step 1) is one or more of metallic tungsten, tungsten oxide, tungsten sulfide, tungsten carbide, tungsten fluoride, tungsten bromide, tungsten chloride, tungsten iodide or tungsten nitride.

[0012] Furthermore, the tungsten-containing precursor in step 1) is tungstate.

[0013] Furthermore, the tungstate is one or more of sodium tungstate, calcium tungstate, magnesium tungstate or sodium octafluorotungstate.

[0014] Furthermore, the boron-containing precursor is one or more of elemental boron, boric acid, sodium borohydride, boron oxide, boron trichloride, boron powder, borane ammonia, boron carbide, boron nitride or boron trifluoride.

[0015] Furthermore, the flux A in step 1) is a halogen-containing metal compound with the molecular formula: MX, wherein M is Na, Mg, K, Ca, Cs or Cu, and X is F, Cl, Br or I.

[0016] Furthermore, the inert gas in step 3) or step 5) is helium, argon or nitrogen.

[0017] The second technical solution adopted to realize the present invention is: a method for preparing a porous tungsten boride catalyst. The prepared porous tungsten boride catalyst is applied to the reaction of preparing vinylidene chloride by dehydrochlorination of 1,1,2-trichloroethane.

[0018] The beneficial effects of the preparation method and application of a porous tungsten boride catalyst of the present invention are as follows:

[0019] 1. A method for preparing a porous tungsten boride catalyst. The prepared porous tungsten boride catalyst is an in-situ synthesized porous tungsten boride material catalyst. It has good catalytic activity in the dehydrochlorination reaction of 1,1,2-trichloroethane under a wide range of space velocity. In the above-mentioned dehydrochlorination reaction of 1,1,2-trichloroethane, the reaction activity is good, the conversion rate can reach more than 86%, and the selectivity of vinylidene chloride can reach more than 99%. The material itself has excellent activity and can be directly used as a catalyst or as a catalyst carrier;

[0020] 2. A method for preparing a porous tungsten boride catalyst. By adjusting the precursor and flux, the physical and chemical properties of the catalyst can be controlled. The porous tungsten boride material has high and stable mechanical strength, high temperature resistance, strong acid and alkali corrosion resistance, high specific surface area, easy activation surface, and good thermal and electrical conductivity. At the same time, due to the abundant resources and low price of synthetic raw materials, the preparation process is green and simple, the production cost is low, the harm to the environment is small, and it has high research value;

[0021] 3. A porous tungsten boride catalyst has the characteristics of high hardness, good conductivity, good thermal shock resistance and low chemical activity in corrosive media. It is used as wear-resistant, corrosion-resistant and electrode material in strong acid, strong alkali and high temperature environments and is applied in national defense science and technology, medical treatment, nuclear technology, surface treatment, machinery manufacturing, transmission machinery and catalytic new materials. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example 1

[0024] (1) Weigh 12.32 g of tungsten oxide, 13.92 g of boron oxide, and 0.5 g of sodium chloride, and stir for 0.5 h to mix them thoroughly;

[0025] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0026] (3) cooling the molten material to 80° C. under the protection of helium;

[0027] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 100 Pa and a rotation speed of 300 r / min for 3 h;

[0028] (5) calcining the ball-milled catalyst at 1800° C. for 10 h, and then cooling it to room temperature;

[0029] (6) Grinding the catalyst after cooling to room temperature to a particle size of 20 mesh;

[0030] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: reaction at 220°C, space velocity 100 h -1 The reaction was carried out under the following conditions: The reaction conversion rate was 68% and the selectivity of vinylidene chloride was 99%.

[0031] Example 2

[0032] (1) Weigh 18.38 g of tungsten, 6 g of boron, and 0.2 g of sodium chloride, and stir for 0.5 h to mix them thoroughly;

[0033] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0034] (3) cooling the molten material to 120° C. under the protection of helium;

[0035] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 1000 Pa and a rotation speed of 200 r / min for 5 h;

[0036] (5) calcining the ball-milled catalyst at 1100° C. for 5 h, and then cooling it to room temperature;

[0037] (6) Grinding the catalyst after cooling to room temperature to a particle size of 10 mesh;

[0038] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: reaction at 300°C, space velocity 5h -1 The reaction was carried out under the following conditions: the reaction conversion rate was 86% and the selectivity of vinylidene chloride was 99%.

[0039] Example 3

[0040] (1) Weigh 19.5 g of tungsten carbide, 13.92 g of boron oxide, and 0.5 g of magnesium chloride, and stir for 0.5 h to mix them thoroughly;

[0041] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0042] (3) cooling the molten material to 25° C. under the protection of helium;

[0043] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 100,000 Pa and a rotation speed of 60 r / min for 3 h;

[0044] (5) calcining the ball-milled catalyst at 1000° C. for 10 h, and then cooling it to room temperature;

[0045] (6) Grinding the catalyst after cooling to room temperature to a particle size of 200 mesh;

[0046] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: The reaction was carried out at 180°C and a space velocity of 90 h -1 The reaction conversion rate was 74% and the selectivity of vinylidene chloride was 99%.

[0047] Example 4

[0048] (1) Weigh 19.5 g of tungsten carbide, 27.84 g of boron oxide, and 0.3 g of copper chloride, and stir for 0.5 h to mix them thoroughly;

[0049] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0050] (3) cooling the molten material to 120° C. under the protection of helium;

[0051] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 100 Pa and a rotation speed of 250 r / min for 5 h;

[0052] (5) calcining the ball-milled catalyst at 1600° C. for 10 h, and then cooling it to room temperature;

[0053] (6) Grinding the catalyst after cooling to room temperature to a particle size of 40 mesh;

[0054] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: reaction at 250°C, space velocity 30h -1 The reaction conversion rate was 83%, and the selectivity of vinylidene chloride was 96%.

[0055] Example 5

[0056] (1) Weigh 9.19 g of tungsten oxide, 55.68 g of boron oxide, and 0.3 g of sodium chloride, and stir for 0.5 h to mix them thoroughly;

[0057] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0058] (3) cooling the molten material to 120° C. under the protection of helium;

[0059] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 100 Pa and a rotation speed of 200 r / min for 5 h;

[0060] (5) calcining the ball-milled catalyst at 1500° C. for 2 h, and then cooling it to room temperature;

[0061] (6) Grinding the catalyst after cooling to room temperature to a particle size of 100 mesh;

[0062] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: reaction at 150°C, space velocity 90h -1 The reaction was carried out under the following conditions: The reaction conversion rate was 26% and the selectivity of vinylidene chloride was 96%.

[0063] Example 6

[0064] (1) Weigh 4.54 g of tungsten oxide, 55.68 g of boron oxide, and 0.4 g of potassium bromide, and stir for 0.5 h to mix them thoroughly;

[0065] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0066] (3) cooling the molten material to 50° C. under the protection of helium;

[0067] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 3000 Pa and a rotation speed of 250 r / min for 5 h;

[0068] (5) calcining the ball-milled catalyst at 1600° C. for 8 h, and then cooling it to room temperature;

[0069] (6) Grinding the catalyst after cooling to room temperature to a particle size of 80 mesh;

[0070] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: reaction at 160°C, space velocity 30h -1 The reaction was carried out under the following conditions: the reaction conversion rate was 86% and the selectivity of vinylidene chloride was 99%.

[0071] Example 7

[0072] (1) Weigh 2.27 g of tungsten oxide, 55.68 g of boron oxide, and 0.5 g of sodium chloride, and stir for 0.5 h to mix them thoroughly;

[0073] (2) The above mixture is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , so that it becomes a molten substance;

[0074] (3) cooling the molten material to 60° C. under the protection of helium;

[0075] (4) The cooled mixture was ball-milled in a ball mill at a vacuum degree of 5000 Pa and a rotation speed of 200 r / min for 3 h;

[0076] (5) calcining the ball-milled catalyst at 200° C. for 2 h, and then cooling it to room temperature;

[0077] (6) Grinding the catalyst after cooling to room temperature to a particle size of 90 mesh;

[0078] (7) Evaluation of 1,1,2-trichloroethane dehydrochlorination reaction in a fixed bed reactor: The reaction was carried out at 220°C and a space velocity of 60 h -1 The reaction was carried out under the following conditions: The reaction conversion rate was 51% and the selectivity of vinylidene chloride was 99%.

[0079] Table 1 Evaluation table of catalytic performance of porous tungsten boride catalyst

[0080]

[0081] Tungsten boride has the characteristics of high hardness, good electrical conductivity, good thermal shock resistance and low chemical activity in corrosive media. It can be used as wear-resistant, corrosion-resistant and electrode materials in strong acid, strong alkali and high temperature environments and is applied in the fields of national defense science and technology, medical treatment, nuclear technology, surface treatment, machinery manufacturing, transmission machinery and catalytic new materials. The porous tungsten boride catalyst prepared by the present invention can be used in the reaction of preparing vinylidene chloride by 1,1,2-trichloroethane dehydrochlorination method. The reaction characteristics of preparing vinylidene chloride by 1,1,2-trichloroethane dehydrochlorination method are as follows: In a fixed bed reactor, the porous tungsten boride catalyst is loaded, and the reactant 1,1,2-trichloroethane is carried by nitrogen by bubbling method. The reaction temperature is 150-300°C and the reaction pressure is 0.1-0.3MPa to react and generate vinylidene chloride. The gas space velocity is 5-100h -1 .

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a porous tungsten boride catalyst, wherein the porous tungsten boride catalyst has the chemical formula W x B y , where x = 0 to 3, y = 1 to 12, and is characterized by: The preparation method comprises the following steps: 1) mixing a tungsten precursor and a boron precursor in a molar ratio of tungsten to boron = 1:0.5 to 1:12, and fully mixing with flux A, stirring evenly to obtain a uniform mixture; the flux A is potassium bromide; 2) The mixture stirred evenly in step 1) is placed in an electrolytic cell under the following electrolysis conditions: voltage 1.5-3V, current 10-500mA / cm 2 , forming a molten substance to obtain a melt; 3) Under the protection of inert gas, the melt in step 2) is cooled to 25° C. to 120° C.; 4) subjecting the melt after cooling in step 3) to mechanical ball milling, wherein the ball milling time is 3 h to 6 h, the vacuum degree is 100 Pa to 100000 Pa, and the ball milling speed is 60 to 300 r / min to obtain a ball milled mixture; 5) Under inert gas conditions, the ball-milled mixture in step 4) is subjected to high-temperature calcination at a temperature of 200 to 1800° C. for a time of 2 to 12 hours, and then cooled to 25° C.; 6) Grinding the mixture obtained in step 5) into powder of 10-200 mesh, and then pressing into blocks.

2. The method for preparing a porous tungsten boride catalyst according to claim 1, characterized in that: The tungsten precursor in step 1) is one or more of metallic tungsten, tungsten oxide, tungsten sulfide, tungsten carbide, tungsten fluoride, tungsten bromide, tungsten chloride, tungsten iodide or tungsten nitride.

3. The method for preparing a porous tungsten boride catalyst according to claim 1, characterized in that: The tungsten precursor in step 1) is tungstate.

4. The method for preparing a porous tungsten boride catalyst according to claim 3, characterized in that: The tungstate is one or more of sodium tungstate, calcium tungstate, magnesium tungstate or sodium octafluorotungstate.

5. The method for preparing a porous tungsten boride catalyst according to claim 1, characterized in that: The boron precursor is one or more of elemental boron, boric acid, sodium borohydride, boron oxide, boron trichloride, boron powder, borane ammonia, boron carbide, boron nitride or boron trifluoride.

6. The method for preparing a porous tungsten boride catalyst according to claim 1, characterized in that: The inert gas in step 3) or step 5) is helium, argon or nitrogen.

7. Use of the porous tungsten boride catalyst prepared by the method for preparing a porous tungsten boride catalyst according to claim 1 in the reaction of preparing vinylidene chloride by dehydrochlorination of 1,1,2-trichloroethane.

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