Special catalyst for dehydrochlorination of tetrachloropropane and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a catalyst special for tetrachloropropane dehydrochlorination and a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: (1) placing gamma-alumina powder in a solvent, adding an amino-containing silane coupling agent, and heating for reaction to obtain modified gamma-alumina powder; and (2) preparing modified gamma-alumina powder loaded with trivalent iron salt or trivalent chromium salt, and drying to obtain the special catalyst for dehydrochlorination of tetrachloropropane. Iron ions or chromium ions complexed by an amino silane coupling agent improve the stability of the active component, the active component is attached to a gamma-alumina matrix by the catalyst, the activity of the main catalyst can be effectively regulated and controlled, the phenomena of chlorine absorption, coking and the like are reduced, the dehydrochlorination reaction is carried out when tetrachloropropane is in contact with the solid matrix, and the dehydrochlorination reaction is carried out when the tetrachloropropane is in contact with the solid matrix. On the basis of high conversion rate and selectivity, side reaction is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to a special catalyst for dehydrochlorination of tetrachloropropane, a preparation method thereof, and an application thereof. Background Art

[0002] At present, the widely used refrigerant 1,1,1,2-tetrafluoroethane has entered the process of being phased out due to its relatively high GWP value (global warming potential, GWP = 1300). It has become extremely urgent to research and develop a new type of green and environmentally friendly refrigerant with a zero ODP value (ozone depletion potential) and a low GWP value. The ODP value of 2,3,3,3-tetrafluoropropene is zero, and the GWP value is 4. It has a refrigeration system performance very close to that of 1,1,1,2-tetrafluoroethane. It is currently recognized as an ideal substitute that can "directly replace" 1,1,1,2-tetrafluoroethane and is considered a new generation of new type of green and environmentally friendly refrigerant.

[0003] As an ideal substitute for 1,1,1,2-tetrafluoroethane, 2,3,3,3-tetrafluoropropene has many physical properties similar or close to those of 1,1,1,2-tetrafluoroethane. The molecular weight of 2,3,3,3-tetrafluoropropene is close to that of 1,1,1,2-tetrafluoroethane. The boiling point of 2,3,3,3-tetrafluoropropene is lower than that of 1,1,1,2-tetrafluoroethane, and the saturated vapor pressure (25°C) is higher than that of 1,1,1,2-tetrafluoroethane. It has a saturated gas density and a critical point temperature similar to those of 1,1,1,2-tetrafluoroethane. These properties enable 2,3,3,3-tetrafluoropropene to directly replace 1,1,1,2-tetrafluoroethane without the need to replace the air-conditioning system, and its refrigeration performance is equivalent to that of 1,1,1,2-tetrafluoroethane.

[0004] As an important precursor of the new type of green and environmentally friendly refrigerant 2,3,3,3-tetrafluoropropene, with the continuous expansion of the demand for the new refrigerant, the demand for 1,1,3-trichloropropene is also increasing. In recent years, as the main raw material of the new generation of refrigerant 2,3,3,3-tetrafluoropropene, it has become one of the main hotspots and trends concerned and invested by major companies and the military industry.

[0005] The common raw material of 1,1,3-trichloropropene is 1,1,1,3-tetrachloropropane, which needs to be prepared through dehydrochlorination reaction. The dehydrochlorination reaction is a key step in the synthesis of hydrofluoroolefins, and the catalyst is its core. The dehydrochlorination catalysts for the synthesis of hydrofluoroolefins can be mainly divided into three categories: carbon-based catalysts, metal oxide catalysts, and metal halide catalysts. The dehydrochlorination of 1,1,1,3-tetrachloropropane generally uses soluble metal chloride catalysts. Although it has high conversion rate and selectivity, it needs to go through processes such as distillation and separation of products, with complex processes and low recyclability of the catalyst. In addition, the dissolved metal chloride catalyst is prone to side reactions, affecting the improvement of product performance. CN111559952A uses iron p-toluenesulfonate as a catalyst to heat and dehydrochlorinate 1,1,1,3-tetrachloropropane in a stirred tank reactor to produce 1,1,3-trichloropropene, and an extractant is added after the reaction to recover the catalyst iron p-toluenesulfonate. However, its essence is still a liquid-phase catalyst, and a solvent is needed to extract and recover the catalyst, with low catalyst activity. CN 111559953 A, CN 111604041 A, etc. use metal oxides and ferrous ions as catalysts respectively. Although the recyclability of the catalyst is improved, the conversion rate of 1,1,1,3-tetrachloropropane and the selectivity of 1,1,3-trichloropropene are still low, and ferrous ions are unstable, limiting their popularization and use. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a special catalyst for the dehydrochlorination of tetrachloropropane. The catalyst makes the active component adhere to the solid matrix, and the dehydrochlorination reaction occurs when 1,1,1,3-tetrachloropropane contacts the solid matrix, which can effectively regulate the activity of the main catalyst. On the basis of high conversion rate and selectivity, the stability of the catalyst is further improved, and the occurrence of side reactions is avoided.

[0007] To achieve the above object, the technical solution provided by the present invention is: A preparation method of a special catalyst for the dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a solvent, then add an amino-silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-silane coupling agent is 1:(0.01 - 0.2); (2) Use the equal-volume impregnation method to prepare modified γ-alumina powder loaded with trivalent iron salt or trivalent chromium salt, and obtain the special catalyst for the dehydrochlorination of tetrachloropropane after drying.

[0008] γ-aluminum oxide powder has a high specific surface area and a rich pore structure, so the loaded metal ions are more likely to be dispersed on its surface. Due to its adjustable pore structure, the diffusion resistance of the loaded metal ions is reduced and the occurrence of unnecessary pore blockage is avoided. At the same time, the adjustable surface acidity of γ-aluminum oxide powder plays a stabilizing role in the catalyst used in the dehydrochlorination process and also has an important impact on the carbon deposition behavior occurring in the catalytic reaction. Using γ-aluminum oxide powder as a carrier can greatly improve the adhesion efficiency to ferric salts or chromium salts.

[0009] However, relying solely on the physical properties of γ-aluminum oxide powder, its adhesion is limited. To improve the adhesion stability, the present invention adds an amino coupling agent to modify it. On the one hand, the siloxane bond in the coupling agent can undergo a hydrolysis reaction with the hydroxyl groups on the surface of γ-aluminum oxide powder, overcoming the physical forces such as van der Waals forces and electrostatic attraction between γ-aluminum oxide particles and improving the dispersion performance of the powder. On the other hand, since the coupling agent contains various amino groups, it can complex with ferric ions or chromium ions, improving the stability of ferric ions or chromium ions. Compared with ferrous ions and divalent metal ions such as copper, zinc, magnesium, and palladium, ferric ions or chromium ions are more stable; more importantly, ferric ions or chromium ions are more likely to undergo a complexation reaction with amino groups, improving the stability of the catalyst.

[0010] Further, the specific surface area of the γ-aluminum oxide powder described in step (1) is 200 - 300 m 2 / g, the average pore diameter is 5 - 12 nm, and the pore volume is 0.3 - 1 cm 3 / g. The diameter of the powder particles is not particularly limited, and generally those within 0.2 - 3 mm are acceptable. An appropriate specific surface area can not only load more active components but also be evenly loaded by the silane coupling agent. And a larger pore diameter provides more space for carbon deposition and ionic active components, improving the dehydrochlorination performance of the catalyst.

[0011] Further, the amino-containing silane coupling agent described in step (1) is at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylethyldimethoxysilane, γ-aminopropylethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-divinyltriaminepropylmethyldimethoxysilane, 3-divinyltriaminepropyltrimethoxysilane, 3-divinyltriaminepropyltriethoxysilane.

[0012] The complexation principle of amino-silane coupling agents is mainly based on the coordination between ferric ions or chromium ions and amino-silane coupling agent molecules. Amino-silane coupling agents contain multiple electron-donating groups - amino groups, and these electron-donating groups have lone pairs of electrons that can form coordination bonds with ferric ions or chromium ions. Aqueous solutions of ferric ions or chromium ions are acidic. During the complexation process, ferric ions or chromium ions act as central ions, and amino-silane coupling agents act as ligands. Through the formation of coordination bonds, ferric ions or chromium ions are surrounded within the molecular structure of the complexing agent. Amino coupling agents have strong complexation ability and can form stable complexes with ferric ions or chromium ions, remaining stable even within a relatively wide pH range. Through complexation, ferric ions or chromium ions are stably loaded onto the alumina support, improving the stability of the catalyst.

[0013] Furthermore, the amino-silane coupling agent mentioned in step (1) is at least two of the above-mentioned coupling agents. For example, the coupling agent comprises component A and component B; component A is selected from at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylethyldimethoxysilane, γ-aminopropylethyldiethoxysilane, and component B is selected from at least one of N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-divinyltriaminepropylmethyldimethoxysilane, 3-divinyltriaminepropyltrimethoxysilane, 3-divinyltriaminepropyltriethoxysilane; wherein, the molar ratio of component A to component B is (0 - 1):(1 - 2), the molar amount of component B is greater than that of component A, and the amount of component A is not 0.

[0014] The combination of different coupling agents can better exert the steric effect, improve the stability of the catalyst, and enable it to be used for a long time. Further, the amino-silane coupling agent is at least three of the above coupling agents. For example, the coupling agent includes component a, component b, and component c; component a is selected from at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylethyldimethoxysilane, γ-aminopropylethyldiethoxysilane, component b is selected from at least one of N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and component c is selected from at least one of 3-divinyltriaminopropylmethyldimethoxysilane, 3-divinyltriaminopropyltrimethoxysilane, 3-divinyltriaminopropyltriethoxysilane; the molar ratio of component a, component b, and component c is (0-1):(1-2):(2-4), and the molar amounts of the three components are such that component c > component b > component a, and the amount of component a is not 0. As the amino chain length and the number of amino groups in component a, component b, and component c increase, their amounts gradually increase, resulting in a gradient distribution of amino groups on the carrier surface. The composite modification with amino chains of different lengths is more conducive to improving the dispersion performance of ions. Based on the coupling agent with a long amino carbon chain as the main body, a small amount of coupling agent with a short amino carbon chain is introduced into the composite coupling agent, which can, on the one hand, exert the excellent complexing effect of the long-chain amino group, and on the other hand, solve the steric hindrance effect caused by the longer amino carbon chain, and improve the complexing ability for iron ions or chromium ions.

[0015] Further, in step (1), the dispersion adopts an ultrasonic process, and the ultrasonic power is 100-200W.

[0016] Further, in step (1), the temperature of the heating reaction is 45-60°C, and the reaction time is 1-3h. Through the ultrasonic dispersion process, the coupling agent can be promoted to enter the micropores of the alumina powder for full modification. The heating process, on the one hand, improves the modification rate, and on the other hand, improves the mobility of the coupling agent molecular chain, promoting the uniformity of the modification of the alumina surface.

[0017] Further, in step (2), the ferric salt is ferric chloride, and the chromic salt is chromium chloride. Based on the total mass of the catalyst, the loading amount of the ferric salt or the chromic salt is 15-30wt%. In particular, the ferric salt or the chromic salt is impregnated in the form of an aqueous solution.

[0018] Further, in step (2), the drying is a vacuum drying process.

[0019] On the other hand, the present invention also provides a special catalyst for dehydrochlorination of tetrachloropropane and the application of the special catalyst for dehydrochlorination of tetrachloropropane in the dehydrochlorination of 1,1,1,3-tetrachloropropane.

[0020] The weak acidity on the surface of the catalyst is beneficial to the improvement of catalytic activity. However, during the catalytic dehydrochlorination process, conventional catalysts are prone to chlorine absorption, generating strong acidic sites, and the strong acidic sites are likely to cause dimerization of olefin products, not only resulting in a decrease in selectivity, but also increasing coking and carbon deposition on the catalyst surface, leading to a reduction in catalytic performance. The iron ions or chromium ions complexed with the amino silane coupling agent avoid this problem. This catalyst attaches the active components to the solid matrix, not only reducing phenomena such as chlorine absorption and coking, but also enabling the dehydrochlorination reaction to occur when 1,1,1,3-tetrachloropropane contacts the solid matrix. On the basis of high conversion rate and selectivity, the catalyst stability is further improved, the occurrence of side reactions is avoided, and it is conducive to the separation, recycling and utilization of the catalyst.

[0021] Beneficial effects: (1) Using complexed iron or chromium to catalyze the dehydrochlorination of 1,1,1,3-tetrachloropropane, the selectivity of 1,1,3-trichloropropene is high.

[0022] (2) By catalyzing the contact of 1,1,1,3-tetrachloropropane with the catalyst attached to the γ-aluminum oxide powder carrier, it is easier to operate compared with the dissolved metal chloride catalyst, avoiding both the process of distillation separation from the dissolved catalyst and reducing the generation of by-products and the discharge of hazardous waste rich in catalyst. Specific embodiments

[0023] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the examples. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0024] The methods for testing the activity of the catalysts in the following examples and comparative examples are the same. Specifically: Under the same test conditions, 15 g of the catalyst was loaded into a reaction tube with a length of 25 cm and a diameter of 1.2 cm. Screens were installed at both ends of the reaction tube to block the catalyst inside the tube. After activation with nitrogen, the temperature and pressure were adjusted, and at 140 °C, liquid-phase 1,1,1,3-tetrachloropropane was introduced using a flow pump at a flow rate of 0.35 mL / min. After reacting for a period of time (3 h), the liquid sample leaving the tube was collected and subjected to chromatographic analysis to test the conversion rate of 1,1,1,3-tetrachloropropane and the selectivity of 1,1,3-trichloropropene respectively.

[0025] Example 1 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1, then add an amino-silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-silane coupling agent is 1:0.1; the specific surface area of the γ-alumina powder is 277 m 2 / g, the average pore diameter is 9.38 nm, and the pore volume is 0.66 cm 3 / g; the amino-silane coupling agent is 3-divinyltriaminopropylmethyldimethoxysilane; the dispersion adopts an ultrasonic process with an ultrasonic power of 100 W; the temperature of the heating reaction is 50 °C, and the reaction time is 3 h; (2) Prepare modified γ-alumina powder loaded with ferric salt by the equal-volume impregnation method, and obtain a special catalyst for dehydrochlorination of tetrachloropropane after vacuum drying; the ferric salt is ferric chloride, and it is impregnated by the ferric chloride aqueous solution impregnation method to make the ferric salt loading 23.2 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 73.8%, and the selectivity of 1,1,3-trichloropropene is 97.5%.

[0026] Example 2 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:2, then add an amino-silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-silane coupling agent is 1:0.2; the specific surface area of the γ-alumina powder is 284 m 2 / g, the average pore diameter is 7.1 nm, and the pore volume is 0.65 cm 3 / g; the amino-silane coupling agent is 3-divinyltriaminopropyltrimethoxysilane; the dispersion adopts an ultrasonic process with an ultrasonic power of 180 W; the temperature of the heating reaction is 60 °C, and the reaction time is 1.6 h; (2) Prepare modified γ-alumina powder loaded with chromic salt by the equal-volume impregnation method, and obtain a special catalyst for dehydrochlorination of tetrachloropropane after vacuum drying; the chromic salt is chromium chloride, and it is impregnated by the chromium chloride aqueous solution impregnation method to make the chromic salt loading 22.1 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 70.3%, and the selectivity of 1,1,3-trichloropropene is 98.3%.

[0027] Example 3 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.3, then add an amino-functional silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-functional silane coupling agent is 1:0.13; the specific surface area of the γ-alumina powder is 271 m 2 / g, the average pore diameter is 8.3 nm, and the pore volume is 0.69 cm 3 / g; the amino-functional silane coupling agent is a mixture of 3-divinyltriaminopropylmethyldimethoxysilane and 3-divinyltriaminopropyltrimethoxysilane with a molar ratio of 1:1; the dispersion adopts an ultrasonic process with an ultrasonic power of 130 W; the temperature of the heating reaction is 52 °C, and the reaction time is 2.6 h; (2) Prepare modified γ-alumina powder loaded with trivalent chromium salt by the equal-volume impregnation method, and obtain the special catalyst for dehydrochlorination of tetrachloropropane after vacuum drying; the trivalent chromium salt is chromium chloride, and it is impregnated by the chromium chloride aqueous solution impregnation method to make the loading amount of the trivalent chromium salt 21.5 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 72.5%, and the selectivity of 1,1,3-trichloropropene is 97.2%.

[0028] Example 4 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.8, then add an amino-functional silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-functional silane coupling agent is 1:0.18; the specific surface area of the γ-alumina powder is 267 m 2 / g, the average pore diameter is 8.25 nm, and the pore volume is 0.69 cm 3 / g; the amino-functional silane coupling agent is a mixture of 3-divinyltriaminopropylmethyldimethoxysilane and 3-divinyltriaminopropyltrimethoxysilane with a molar ratio of 1:3; the dispersion adopts an ultrasonic process with an ultrasonic power of 180 W; the temperature of the heating reaction is 56 °C, and the reaction time is 1.9 h; (2) Prepare modified γ-alumina powder loaded with trivalent iron salt by the equal-volume impregnation method, and obtain the special catalyst for dehydrochlorination of tetrachloropropane after vacuum drying; the trivalent iron salt is iron chloride, and it is impregnated by the iron chloride aqueous solution impregnation method to make the loading amount of the trivalent iron salt 23.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 72.3%, and the selectivity of 1,1,3-trichloropropene is 98.1%.

[0029] Example 5 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.2, then add an amino-silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-silane coupling agent is 1:0.16; the specific surface area of the γ-alumina powder is 277 m 2 / g, the average pore diameter is 9.38 nm, and the pore volume is 0.66 cm 3 / g; the amino-silane coupling agent is 3-divinyltriaminopropyltrimethoxysilane; the dispersion adopts an ultrasonic process with an ultrasonic power of 170 W; the temperature of the heating reaction is 53 °C, and the reaction time is 2.2 h; (2) Prepare modified γ-alumina powder loaded with ferric salt by the equal-volume impregnation method, and obtain a special catalyst for dehydrochlorination of tetrachloropropane after vacuum drying; the ferric salt is ferric chloride, and it is impregnated by the ferric chloride aqueous solution impregnation method to make the loading amount of ferric salt 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 69.9%, and the selectivity of 1,1,3-trichloropropene is 97.3%.

[0030] Example 6 A preparation method of a special catalyst for dehydrochlorination of tetrachloropropane, comprising the following steps: (1) Place γ-alumina powder in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.2, then add an amino-silane coupling agent, disperse evenly, heat and react, filter, wash, and dry to obtain modified γ-alumina powder; the mass ratio of γ-alumina powder to the amino-silane coupling agent is 1:0.16; the specific surface area of the γ-alumina powder is 277 m 2 / g, the average pore diameter is 9.38 nm, and the pore volume is 0.66 cm 3 / g; the amino-silane coupling agent is a mixture of 3-divinyltriaminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltriethoxysilane with a molar ratio of 0.5:1.5; the dispersion adopts an ultrasonic process with an ultrasonic power of 170 W; the temperature of the heating reaction is 53 °C, and the reaction time is 2.2 h; (2) The modified γ-alumina powder loaded with ferric salt was prepared by the equal-volume impregnation method and obtained the special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination after vacuum drying; the ferric salt was ferric chloride and was impregnated by the ferric chloride aqueous solution impregnation method to make the loading amount of ferric salt be 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane was 72.2%, and the selectivity of 1,1,3-trichloropropene was 98.1%.

[0031] Example 7 A preparation method of a special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination, comprising the following steps: (1) The γ-alumina powder was placed in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.2, and then an amino-silane coupling agent was added, dispersed evenly, heated for reaction, filtered, washed, and dried to obtain the modified γ-alumina powder; the mass ratio of the γ-alumina powder to the amino-silane coupling agent was 1:0.16; the specific surface area of the γ-alumina powder was 277 m 2 / g, the average pore diameter was 9.38 nm, and the pore volume was 0.66 cm 3 / g; the amino-silane coupling agent was a mixture of 3-divinyltriaminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltriethoxysilane with a molar ratio of 1.5:0.5; the dispersion was carried out by an ultrasonic process with an ultrasonic power of 170 W; the temperature of the heating reaction was 53 °C, and the reaction time was 2.2 h; (2) The modified γ-alumina powder loaded with ferric salt was prepared by the equal-volume impregnation method and obtained the special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination after vacuum drying; the ferric salt was ferric chloride and was impregnated by the ferric chloride aqueous solution impregnation method to make the loading amount of ferric salt be 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane was 74.3%, and the selectivity of 1,1,3-trichloropropene was 98.6%.

[0032] Example 8 A preparation method of a special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination, comprising the following steps: (1) The γ-alumina powder was placed in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.2, and then an amino-silane coupling agent was added, dispersed evenly, heated for reaction, filtered, washed, and dried to obtain the modified γ-alumina powder; the mass ratio of the γ-alumina powder to the amino-silane coupling agent was 1:0.16; the specific surface area of the γ-alumina powder was 277 m 2 / g, the average pore diameter was 9.38 nm, and the pore volume was 0.66 cm 3 / g; The amino-functional silane coupling agent is a mixture of 3-divinyltriaminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and γ-aminopropyltriethoxysilane with a molar ratio of 3:1.5:0.5; The dispersion is carried out by an ultrasonic process with an ultrasonic power of 170 W; The temperature of the heating reaction is 53 °C and the reaction time is 2.2 h; (2) The modified γ-aluminum oxide powder loaded with ferric salt is prepared by the equal-volume impregnation method and then obtained the special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination after vacuum drying; The ferric salt is ferric chloride and is impregnated by the ferric chloride aqueous solution impregnation method to make the loading of ferric salt be 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 76.1% and the selectivity of 1,1,3-trichloropropene is 99.2%.

[0033] Comparative Example 1 A preparation method of a special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination, comprising the following steps: The γ-aluminum oxide powder loaded with ferric salt is prepared by the equal-volume impregnation method and then obtained the special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination after vacuum drying; The specific surface area of the γ-aluminum oxide powder is 277 m 2 / g, the average pore diameter is 9.38 nm, and the pore volume is 0.66 cm 3 / g; The ferric salt is ferric chloride and is impregnated by the ferric chloride aqueous solution impregnation method to make the loading of ferric salt be 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane is 51.7% and the selectivity of 1,1,3-trichloropropene is 90.9%.

[0034] Comparative Example 2 A preparation method of a special catalyst for 1,1,1,3-tetrachloropropane dehydrochlorination, comprising the following steps: (1) The γ-aluminum oxide powder is placed in a mixed solvent with a volume ratio of ethanol to deionized water of 1:1.2, and then an amino-functional silane coupling agent is added, dispersed evenly, heated for reaction, filtered, washed, and dried to obtain the modified γ-aluminum oxide powder; The mass ratio of the γ-aluminum oxide powder to the amino-functional silane coupling agent is 1:0.4; The specific surface area of the γ-aluminum oxide powder is 277 m 2 / g, the average pore diameter is 9.38 nm, and the pore volume is 0.66 cm 3 / g; The amino-functional silane coupling agent is a mixture of 3-divinyltriaminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and γ-aminopropyltriethoxysilane with a molar ratio of 3:1.5:0.5; The dispersion is carried out by an ultrasonic process with an ultrasonic power of 170 W; The temperature of the heating reaction is 53 °C and the reaction time is 2.2 h; (2) The modified γ-alumina powder loaded with ferric salt was prepared by the equal-volume impregnation method and dried in vacuum to obtain the special catalyst for dehydrochlorination of tetrachloropropane. The ferric salt was ferric chloride, and the impregnation was carried out by the impregnation method with an aqueous solution of ferric chloride to make the loading amount of ferric salt 22.0 wt%. After testing, the conversion rate of 1,1,1,3-tetrachloropropane was 64.6%, and the selectivity of 1,1,3-trichloropropene was 93.5%.

[0035] It can be seen from Examples 5-8 that different combinations of coupling agents can better exert the steric effect, improve the stability of the catalyst, and enable it to be used for a long time. It can be seen from the above examples and Comparative Example 1 that the amino-silane coupling agent contains multiple electron-donating groups - amino groups, and these electron-donating groups have lone pairs of electrons that can form coordination bonds with ions. The aqueous solution of ferric ions or chromium(III) ions is acidic. During the complexation process, the ions act as central ions, and the amino-silane coupling agent acts as a ligand to surround the ions in the molecular structure of the complexing agent through the formation of coordination bonds. The complexing ability of the amino coupling agent is relatively strong, and it can form stable complexes with ions and remain stable even within a relatively wide pH range. Through complexation, the ions are stably loaded on the alumina support, improving the stability of the catalyst. Compared with Example 8, in Comparative Example 2, the amount of amino-silane coupling agent used is excessive. Due to the strong hydrolysis and complexation effects of the amino-silane coupling agent, when its amount is excessive, the attachment efficiency of the microporous structure of the alumina support will be reduced, affecting the loading of ferric ions or chromium(III) ions and the weak acidic structure on the alumina surface, which is not conducive to improving the catalytic efficiency.

[0036] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a catalyst for dehydrochlorination of tetrachloropropane, characterized in that: The following steps are involved: (1) placing γ-alumina powder in a solvent, then adding an amino-containing silane coupling agent, dispersing evenly, heating for reaction, filtering, washing, and drying to obtain modified γ-alumina powder; the mass ratio of the γ-alumina powder to the amino-containing silane coupling agent is 1:(0.01-0.2); (2) The modified γ-alumina powder loaded with trivalent iron salt or trivalent chromium salt is prepared by an equal volume impregnation method, and after drying, a special catalyst for dehydrochlorination of tetrachloropropane is obtained.

2. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The specific surface area of ​​the γ-alumina powder in step (1) is 200-300m 2 / g, average pore diameter 5-12nm, pore volume 0.3-1cm 3 / g.

3. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The amino-containing silane coupling agent in step (1) is at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylethyldimethoxysilane, γ-aminopropylethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-diethylenetriaminopropylmethyldimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, and 3-diethylenetriaminopropyltriethoxysilane.

4. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The dispersion in step (1) is carried out by ultrasonic process, and the ultrasonic power is 100-200W.

5. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The heating reaction temperature in step (1) is 45-60°C, and the reaction time is 1-3h.

6. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The trivalent iron salt in step (2) is ferric chloride, and the trivalent chromium salt is chromium chloride.

7. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The loading amount of the trivalent iron salt or trivalent chromium salt in step (2) is 15-30wt%.

8. The method for preparing a special catalyst for dehydrochlorination of tetrachloropropane according to claim 1, characterized in that: The drying in step (2) is a vacuum drying process.

9. A special catalyst for dehydrochlorination of tetrachloropropane, characterized in that: The catalyst is prepared by the method for preparing a special catalyst for dehydrochlorination of tetrachloropropane as described in any one of claims 1 to 8.

10. Use of the special catalyst for dehydrochlorination of tetrachloropropane according to claim 9 in dehydrochlorination of 1,1,1,3-tetrachloropropane.