CN108246340B - Preparation and use method of metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination - Google Patents
Preparation and use method of metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination Download PDFInfo
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Abstract
The invention relates to a preparation method and a use method of a metal-free catalyst for synthesizing vinyl chloride by hydrochlorinating acetylene in a fixed bed. Compared with other metal-free catalysts prepared by 'dipping-calcining', the method adopts a mode of combining in-situ doping with ammonia gas treatment to increase the nitrogen content in the catalyst, effectively improves the specific surface area of the catalyst by calcining the precursor and polytetrafluoroethylene under a special temperature-raising system, and improves the proportion of effective active sites and the number of oxygen-containing functional groups on the surface by matching with means such as nitrogen-sulfur co-doping, oxidation treatment and the like, so that the metal-free catalyst has higher activity and excellent selectivity in the reaction of preparing vinyl chloride by hydrochlorinating acetylene in a fixed bed. The preparation method is green and environment-friendly, has wide raw material sources and low cost, can replace a toxic mercuric chloride catalyst, and has wide application prospects in industrial production.
Description
Technical Field
The invention belongs to the technical field of preparation technology and application of catalysts for organic synthesis, and relates to a preparation method and a use method of a metal-free catalyst for preparing vinyl chloride by hydrochlorinating acetylene.
Background
As one of the most widely used general-purpose plastics in the world, polyvinyl chloride has recently been playing an increasingly important role in the production and life of people. Because of the special energy structure of 'poor oil, less gas and rich coal' in China, the monomer for producing the polyvinyl chloride, namely the vinyl chloride, mainly utilizes the mercuric chloride (HgCl) loaded on the activated carbon2) The catalyst is carried out by hydrochlorination of acetylene. However, the high toxicity of mercuric chloride itself and its sublimation during the reaction make this process a serious safety and environmental problem. Therefore, the method is searched for the process for producing the chloroethylene by the calcium carbide methodAn efficient and environment-friendly catalyst for replacing mercuric chloride becomes a subject of wide attention of related researchers at home and abroad.
The replacement of mercuric chloride with other metal chlorides and their built compounds has been a hot spot of research in this field over the last decade. For example, research by Deng national talents and the like at university of south Kelvin finds that stannous chloride has higher catalytic activity on acetylene hydrochlorination, while Weifei and the like at university of Qinghua take bismuth salt as an active component and SiO2As a carrier, the high-efficiency two-component composite catalyst BiPO for the hydrochlorination of acetylene is prepared4-Cu3(PO4)2/SiO2. However, these base metal catalysts have problems such as loss of active components or serious carbon deposition, and thus it is difficult to meet the requirements of industrial application. After a great deal of research on a catalyst taking noble metals such as gold, palladium, platinum and the like as active components, professor Hutchings and the like at British cadov university find that the gold catalyst can show higher activity and selectivity on vinyl chloride in acetylene hydrochlorination. However, the application of the catalyst is severely restricted by the scarce resource and high price of the noble metal, so that the catalyst is difficult to popularize on a large scale.
In recent years, researches of various institutions including Qinghua university, Dalianghuan and Xinjiang river university in China all show that the nitrogen-doped carbon material can be used as a metal-free catalyst in the reaction of preparing vinyl chloride by hydrochlorinating acetylene and has acceptable catalytic activity. Considering the characteristics of environmental friendliness and low price of the material, the material is likely to be developed into a new-generation catalyst for replacing mercury chloride. Patent CN201410532264.1 discloses a metal-free catalyst for synthesizing vinyl chloride, which is characterized in that activated carbon after acid treatment is used as a carrier, the carrier is added into an impregnation solution containing a nitrogen compound for impregnation, and then the impregnated carbon is dried and calcined in a nitrogen atmosphere to obtain the metal-free catalyst. Patent CN201510006148.0 discloses a polypyrrole activated carbon catalyst for catalyzing the reaction of acetylene and hydrogen chloride to generate vinyl chloride, which also uses activated carbon as a carrier, and the catalyst is added into a pyrrole solution to be soaked, and an initiator is added to initiate pyrrole polymerization to obtain polypyrrole activated carbon, and the polypyrrole activated carbon catalyst is obtained by washing, drying and calcining the activated carbon. Patent CN201310518594.0 discloses a metal-free catalyst for hydrochlorination of acetylene, which is prepared in a very similar way to the above two patents, but with an expanded selection of the impregnated support, the impregnating solvent and the non-metallic compound used. Although this patent mentions the use of thiourea, a non-metallic compound, as used in this patent, the process of preparation is quite different from this patent. Generally, these metal-free catalysts use bulk doping to introduce nitrogen from the outside into a support based on activated carbon, and then the catalyst is obtained by calcination under an inert atmosphere. However, this doping method often cannot effectively and uniformly utilize the nitrogen component in the non-metal compound, and meanwhile, the simple "impregnation-calcination" method can produce a metal-free catalyst with relatively low catalytic activity, which is not enough to meet the requirement of practical production.
Disclosure of Invention
In order to overcome the defects in the preparation mode and further improve the activity of the metal-free catalyst in the process of preparing vinyl chloride by reacting acetylene with hydrogen chloride, the invention provides a novel preparation method and a use method of the metal-free catalyst.
The technical scheme adopted by the invention is as follows:
scheme 1: a preparation method of a metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination is characterized by comprising the following steps:
(1) adding a molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at the temperature of 100 ℃ and 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, simultaneously dissolving oligosaccharide and thiourea in deionized water with the water absorption rate of 1.5-2.5 times that of a sample A to obtain a uniform solution, then adding the solution into the sample A and fully mixing, standing at room temperature, sealing and storing for 24-48 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 60-80 ℃ to dryness to obtain a precursor; wherein the oligosaccharide is one of sucrose or glucose, sample a: oligosaccharide: the mass ratio of the thiourea is 1:0.8-1.5: 0.8-4.5;
(3) fully grinding and mixing the precursor and polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5-10 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min and preserving heat for 3-5 hours, then naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Preserving the heat of the mixed gas for 1-2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a dilute nitric acid or hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at the temperature of 100-120 ℃ to obtain the required metal-free catalyst, wherein the mass concentration of the dilute nitric acid solution is 5-10%, and the mass concentration of the hydrogen peroxide solution is 5-15%.
Scheme 2: a preparation method of a metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination is characterized by comprising the following steps:
(1) adding a molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at the temperature of 100 ℃ and 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, dissolving oligosaccharide in deionized water with the water absorption rate of 1-1.2 times that of a sample A to obtain a uniform solution, then adding the solution into the sample A, fully mixing, standing at room temperature, sealing and storing for 24-48 hours, then drying the obtained mixture at 60-80 ℃, then adding the dried mixture into a dichloromethane solution containing dithizone, sealing and stirring for more than 12 hours, then transferring the obtained mixed solution into a rotary evaporator, and evaporating the mixed solution to dryness in a water bath at 40-60 ℃ to obtain a precursor; wherein the oligosaccharide is one of sucrose or glucose, sample a: oligosaccharide: the mass ratio of the dithizone is 1:0.8-1.5: 0.16-0.75;
(3) fully grinding and mixing the precursor and polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5-10 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min and preserving heat for 3-5 hours, then naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Preserving the heat of the mixed gas for 1-2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a dilute nitric acid or hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at the temperature of 100-120 ℃ to obtain the required metal-free catalyst, wherein the mass concentration of the dilute nitric acid solution is 5-10%, and the mass concentration of the hydrogen peroxide solution is 5-15%.
The preparation method in schemes 1 and 2 is characterized in that the molecular sieve is one or more of SBA-15, MCM-41 or MCM-48.
The preparation method described in schemes 1 and 2 is characterized in that the mass ratio of the precursor to the polytetrafluoroethylene powder is 1: 2-5.
A metal-free catalyst for the fixed bed hydrochlorination of acetylene to produce vinyl chloride, characterized in that it is produced using the production method described in any of schemes 1 and 2.
The application method of the metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination is characterized in that the catalyst is applied to a fixed bed acetylene hydrochlorination reactor, and the application method of the catalyst comprises the following steps: the catalyst is placed in a constant temperature interval in a fixed bed reactor, the temperature is raised to 180-250 ℃ under the flowing inert atmosphere, then the gas is switched into hydrogen chloride gas at the temperature, the hydrogen chloride gas is activated for 0.5 to 1.5 hours under the atmosphere, and then acetylene gas is introduced to start the acetylene hydrochlorination reaction; the volume space velocity of the acetylene is 30-120h-1The volume ratio of acetylene to hydrogen chloride is 1:1.05-1.3, and the use temperature range of the metal-free catalyst is 180-.
Compared with the existing metal-free catalyst and the preparation method thereof, the invention has the following innovation:
(1) the method of combining in-situ doping with ammonia gas treatment greatly improves the content of effective nitrogen components in the catalyst. The method takes sucrose or glucose as a carbon source and thiourea or dithizone as a doping agent, simultaneously decomposes the carbon source and the doping agent in the calcining and carbonizing process, and uniformly introduces nitrogen and sulfur components into a carbon material, so that the doping agent is fully utilized; meanwhile, an ammonia gas treatment step is added in the calcining process, so that the nitrogen content of the carbon material is further improved, and the activity and the stability of the metal-free catalyst can be effectively improved.
(2) The carbon material is simultaneously doped with nitrogen and sulfur elements, so that the activity of the metal-free catalyst is further improved. Various documents have suggested that pyridine nitrogen is the active site for the hydrochlorination of acetylene (Journal of Catalysis, 2014, 311: 288-. Our studies show that the addition of sulfur can increase the ratio of pyridine nitrogen in nitrogen species, thereby promoting the improvement of the activity of the metal-free catalyst.
(3) The molecular sieve template is removed by using a new technology, and a calcination system of sectional heating is adopted, so that the specific surface area of the metal-free catalyst is increased. On one hand, the molecular sieve template is removed in a mode of co-heating precursor powder and polytetrafluoroethylene powder, so that the preparation process is simplified, the carbonization and silicon removal are combined to be carried out in one step, and meanwhile, a large number of micropores are reserved in the material in the mode, so that the specific surface area of the metal-free catalyst is increased; on the other hand, the second stage in the calcining process adopts a slow temperature rise mode, so that the collapse of a microporous structure is avoided, and the specific surface area of the material is further improved.
(4) The molecular sieve is subjected to acidification treatment before use, so that the number of hydroxyl groups on the surface of the molecular sieve is increased, the loading of substances in the dipping process is facilitated, and the utilization efficiency of raw materials is improved.
(5) The carbon material obtained by calcining is oxidized by dilute nitric acid or hydrogen peroxide solution, so that the number of oxygen-containing functional groups on the surface of the material can be increased, the adsorption and activation capability of the material on acetylene is improved, and the activity of a metal-free catalyst is improved.
Drawings
FIG. 1: scanning electron micrographs of Cat-1 prepared in example 1;
FIG. 2: scanning electron micrograph of Cat-5 prepared in example 5.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to the embodiments. It is to be understood that the following examples are for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Example 1
(1) Adding 1g of SBA-15 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, simultaneously dissolving 0.8g of sucrose and 1.6g of thiourea in deionized water with the water absorption rate of 1.5 times that of the sample A to obtain a uniform solution, then adding the solution into the sample A, fully mixing, standing at room temperature, sealing and storing for 24 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 60 ℃ to dryness to obtain a precursor;
(3) fully grinding and mixing 3.4g of precursor and 13.6g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5 ℃/min under the flowing inert gas atmosphere, preserving heat for 1 hour, continuing heating to 1000 ℃ at the heating rate of 1 ℃/min, preserving heat for 3 hours, naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 1 hour, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 5% dilute nitric acid solution, stirring at room temperature for more than 3 hours, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-1.
Example 2
(1) Adding 1g of MCM-41 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 100 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, simultaneously dissolving 1g of glucose and 3g of thiourea in deionized water with the water absorption rate of 2.5 times that of the sample A to obtain a uniform solution, then adding the solution into the sample A and fully mixing, standing at room temperature, sealing and storing for 24 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 80 ℃ to dryness to obtain a precursor;
(3) fully grinding and mixing 5g of precursor and 15g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at a heating rate of 10 ℃/min under the atmosphere of flowing inert gas, preserving heat for 1 hour, continuing heating to 800 ℃ at a heating rate of 2 ℃/min, preserving heat for 4 hours, naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 5% hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 100 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-2.
Example 3
(1) Adding 1g of MCM-48 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, simultaneously dissolving 1.2g of sucrose and 2.4g of thiourea in deionized water with the water absorption rate of 2 times of that of the sample A to obtain a uniform solution, then adding the solution into the sample A and fully mixing, standing at room temperature, sealing and storing for 48 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 70 ℃ to dryness to obtain a precursor;
(3) fully grinding and mixing 4.6g of precursor and 13.8g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 7 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 700 ℃ at the heating rate of 5 ℃/min and preserving heat for 5 hours, and then switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 1 hour, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 10% hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-3.
Example 4
(1) Adding 0.5g of SBA-15 and 0.5g of MCM-41 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring for more than 6 hours at room temperature, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, simultaneously dissolving 1.5g of glucose and 1.5g of thiourea in deionized water with the water absorption rate of 2 times of that of the sample A to obtain a uniform solution, then adding the solution into the sample A, fully mixing, standing at room temperature, sealing and storing for 48 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 60 ℃ to dryness to obtain a precursor;
(3) fully grinding and mixing 4g of precursor and 8g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at a heating rate of 10 ℃/min under the atmosphere of flowing inert gas, preserving heat for 1 hour, continuing heating to 900 ℃ at a heating rate of 2 ℃/min, preserving heat for 4 hours, naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Mixed gas (es)Keeping the temperature of the sample for 1 hour, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 10% dilute nitric acid solution, stirring at room temperature for more than 3 hours, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 110 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-4.
Example 5
(1) Adding 1g of SBA-15 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 120 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, 0.8g of sucrose is dissolved in deionized water with the water absorption rate of 1 time that of the sample A to obtain a uniform solution, then the solution is added into the sample A and fully mixed, the mixture is kept stand and sealed for storage for 24 hours at room temperature, then the obtained mixture is dried at 60 ℃, then the mixture is added into a dichloromethane solution containing 0.32g of dithizone and is stirred for more than 12 hours in a sealed manner, then the obtained mixed solution is transferred to a rotary evaporator and is evaporated to dryness in a water bath at 50 ℃ to obtain a precursor;
(3) fully grinding and mixing 2.12g of precursor and 10.6g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5 ℃/min under the flowing inert gas atmosphere, preserving heat for 1 hour, continuing heating to 900 ℃ at the heating rate of 2 ℃/min, preserving heat for 4 hours, naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 5% dilute nitric acid solution, stirring at room temperature for more than 3 hours, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-5.
Example 6
(1) Adding 1g of MCM-41 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 100 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, dissolving 1.2g of glucose in deionized water with the water absorption rate of 1.2 times that of a sample A to obtain a uniform solution, then adding the solution into the sample A and fully mixing, standing at room temperature, sealing and storing for 36 hours, then drying the obtained mixture at 80 ℃, then adding the dried mixture into a dichloromethane solution containing 0.24g of dithizone and sealing and stirring for more than 12 hours, then transferring the obtained mixed solution into a rotary evaporator, and evaporating to dryness in a water bath at 60 ℃ to obtain a precursor;
(3) fully grinding and mixing 2.44g of precursor and 9.76g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 8 ℃/min under the flowing inert gas atmosphere, preserving heat for 1 hour, continuing heating to 1000 ℃ at the heating rate of 1 ℃/min, preserving heat for 3 hours, naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 10% hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-6.
Example 7
(1) Adding 0.5g of SBA-15 and 0.5g of MCM-48 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring for more than 6 hours at room temperature, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 110 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, 1.5g of sucrose is dissolved in deionized water with the water absorption rate of 1.1 times of that of the sample A to obtain a uniform solution, then the solution is added into the sample A and fully mixed, the mixture is kept stand and sealed at the room temperature for 24 hours, then the obtained mixture is dried at 70 ℃, then the mixture is added into a dichloromethane solution containing 0.75g of dithizone and is stirred for more than 12 hours in a sealed manner, then the obtained mixed solution is transferred to a rotary evaporator and is evaporated to dryness in a water bath at 40 ℃ to obtain a precursor;
(3) fully grinding and mixing 3.25g of precursor and 9.75g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 10 ℃/min under the flowing inert gas atmosphere, preserving the heat for 1 hour, continuing heating to 700 ℃ at the heating rate of 5 ℃/min, preserving the heat for 3 hours, and then switching the gas to 10% NH3/N2Keeping the temperature of the mixed gas for 1 hour, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into 8% dilute nitric acid solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 110 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-7.
Example 8
(1) Adding 0.5g of SBA-15, 0.25g of MCM-41 and 0.25g of MCM-48 molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring for more than 6 hours at room temperature, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at 110 ℃ to obtain a sample A;
(2) under the condition of stirring at room temperature, dissolving 1.4g of glucose and 2.8g of thiourea in deionized water with the water absorption rate of 2.5 times of that of the sample A to obtain a uniform solution, then adding the solution into the sample A, fully mixing, standing at room temperature, sealing and storing for 36 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 60 ℃ to dryness to obtain a precursor;
(3) fully grinding and mixing 4.2g of precursor and 12.6g of polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5 ℃/min under the flowing inert gas atmosphere, preserving heat for 1 hour, continuing heating to 900 ℃ at the heating rate of 2 ℃/min, preserving heat for 5 hours, naturally cooling to 700 ℃, and switching the gas to be the gas10% NH3/N2Keeping the temperature of the mixed gas for 2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) and adding the sample B into a 15% hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then carrying out suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-8.
Comparative example 1
Preparation of non-NH3Treated Metal-free catalyst, the purpose of which is to compare with example 1 to understand NH3Effect of treatment on catalyst activity.
The preparation process is the same as example 1, only the gas is naturally cooled to 700 ℃ after step 3, and the gas is switched to 10% NH3/N2Keeping the temperature of the mixed gas for 1 hour, then switching back to the flowing inert gas atmosphere, naturally cooling to room temperature under the purging of the mixed gas, changing the obtained sample B into ' the sample B ', naturally cooling to 700 ℃, keeping the temperature for 1 hour, and finally naturally cooling to room temperature under the purging of the inert gas to obtain a sample B ', wherein the obtained catalyst is named as Cat-9.
Comparative example 2
The catalyst with the molecular sieve template removed with hydrofluoric acid was prepared in order to understand the effect of the way the molecular sieve template was removed on the activity of the catalyst, compared to example 1.
(1) Same as in step 1 of example 1.
(2) Same as in step 2 of example 1.
(3) Transferring 3.4g of precursor powder into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 1000 ℃ at the heating rate of 1 ℃/min and preserving heat for 3 hours, then naturally cooling to 700 ℃, and switching the gas into 10% NH3/N2Keeping the temperature of the mixed gas for 1 hour, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B;
(4) adding the sample B into sufficient hydrofluoric acid, stirring at room temperature for more than 24 hours, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain a sample C;
(5) and adding the sample C into a 5% dilute nitric acid solution, stirring at room temperature for more than 3 hours, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at 120 ℃ to obtain the required metal-free catalyst, wherein the number of the metal-free catalyst is Cat-10.
Comparative example 3
A catalyst doped with urea instead of thiourea was prepared with the aim of knowing the effect of the difference in doping elements on the catalyst activity compared to example 1.
The procedure was the same as in example 1 except that "0.8 g of sucrose and 1.6g of thiourea" in step 2 was changed to "0.8 g of sucrose and 1.6g of urea" and the catalyst obtained was numbered Cat-11.
Comparative example 4
The catalyst was prepared without oxidation treatment in order to understand the effect of the oxidation treatment on the catalyst activity in comparison with example 5.
The procedure was as in steps 1-3 of example 5, and the resulting catalyst was numbered Cat-12.
The evaluation conditions of the metal-free catalyst were: 4 mL of metal-free catalyst is placed in a fixed bed reactor, and the volume space velocity of acetylene is 40 h-1The volume ratio of acetylene to hydrogen chloride is 1:1.2, the catalyst is activated for 1 hour under the atmosphere of hydrogen chloride at 220 ℃ before use, and the reaction temperature is 220 ℃. Samples were taken at the 2 hour reaction point and analyzed, and comparative data for acetylene conversion and vinyl chloride selectivity for different metal-free catalysts are shown in the table:
Claims (4)
1. a preparation method of a metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination is characterized by comprising the following steps:
(1) adding a molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at the temperature of 100 ℃ and 120 ℃ to obtain a sample A; the molecular sieve is one or more of SBA-15, MCM-41 or MCM-48;
(2) under the condition of stirring at room temperature, simultaneously dissolving oligosaccharide and thiourea in deionized water with the water absorption rate of 1.5-2.5 times that of a sample A to obtain a uniform solution, then adding the solution into the sample A and fully mixing, standing at room temperature, sealing and storing for 24-48 hours, then transferring the obtained mixture into a rotary evaporator, and evaporating in a water bath at 60-80 ℃ to dryness to obtain a precursor; wherein the oligosaccharide is one of sucrose or glucose, sample a: oligosaccharide: the mass ratio of the thiourea is 1:0.8-1.5: 0.8-4.5;
(3) fully grinding and mixing the precursor and polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5-10 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min and preserving heat for 3-5 hours, then naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Preserving the heat of the mixed gas for 1-2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B; the mass ratio of the precursor to the polytetrafluoroethylene powder is 1: 2-5;
(4) and adding the sample B into a dilute nitric acid or hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at the temperature of 100-120 ℃ to obtain the required metal-free catalyst, wherein the mass concentration of the dilute nitric acid solution is 5-10%, and the mass concentration of the hydrogen peroxide solution is 5-15%.
2. A preparation method of a metal-free catalyst for preparing vinyl chloride by fixed bed acetylene hydrochlorination is characterized by comprising the following steps:
(1) adding a molecular sieve into a sulfuric acid solution with the mass concentration of 10%, stirring at room temperature for more than 6 hours, then carrying out suction filtration, separation and washing on the molecular sieve to be neutral, and drying the obtained filter cake at the temperature of 100 ℃ and 120 ℃ to obtain a sample A; the molecular sieve is one or more of SBA-15, MCM-41 or MCM-48;
(2) under the condition of stirring at room temperature, dissolving oligosaccharide in deionized water with the water absorption rate of 1-1.2 times that of a sample A to obtain a uniform solution, then adding the solution into the sample A, fully mixing, standing at room temperature, sealing and storing for 24-48 hours, then drying the obtained mixture at 60-80 ℃, then adding the dried mixture into a dichloromethane solution containing dithizone, sealing and stirring for more than 12 hours, then transferring the obtained mixed solution into a rotary evaporator, and evaporating the mixed solution to dryness in a water bath at 40-60 ℃ to obtain a precursor; wherein the oligosaccharide is one of sucrose or glucose, sample a: oligosaccharide: the mass ratio of the dithizone is 1:0.8-1.5: 0.16-0.75;
(3) fully grinding and mixing the precursor and polytetrafluoroethylene powder, transferring the mixture into an alumina tube type furnace, heating to 300 ℃ at the heating rate of 5-10 ℃/min and preserving heat for 1 hour under the flowing inert gas atmosphere, then continuously heating to 700-1000 ℃ at the heating rate of 1-5 ℃/min and preserving heat for 3-5 hours, then naturally cooling to 700 ℃, and switching the gas to 10% NH3/N2Preserving the heat of the mixed gas for 1-2 hours, then switching back to the flowing inert gas atmosphere, and naturally cooling to room temperature under the blowing of the inert gas atmosphere to obtain a sample B; the mass ratio of the precursor to the polytetrafluoroethylene powder is 1: 2-5;
(4) and adding the sample B into a dilute nitric acid or hydrogen peroxide solution, stirring for more than 3 hours at room temperature, then performing suction filtration, separation and washing to be neutral, and finally drying the obtained filter cake at the temperature of 100-120 ℃ to obtain the required metal-free catalyst, wherein the mass concentration of the dilute nitric acid solution is 5-10%, and the mass concentration of the hydrogen peroxide solution is 5-15%.
3. A metal-free catalyst for the fixed bed hydrochlorination of acetylene to vinyl chloride, characterized in that it is prepared using the preparation method according to any one of claims 1-2.
4. Use of a catalyst according to claim 3, characterized in that the catalyst is usedIn a fixed bed acetylene hydrochlorination reactor, the use method of the catalyst comprises the following steps: the catalyst is placed in a constant temperature interval in a fixed bed reactor, the temperature is raised to 180-250 ℃ under the flowing inert atmosphere, then the gas is switched into hydrogen chloride gas at the temperature, the hydrogen chloride gas is activated for 0.5 to 1.5 hours under the atmosphere, and then acetylene gas is introduced to start the acetylene hydrochlorination reaction; the volume space velocity of the acetylene is 30-120h-1The volume ratio of acetylene to hydrogen chloride is 1:1.05-1.3, and the use temperature range of the metal-free catalyst is 180-.
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| GB2492888A (en) * | 2011-07-11 | 2013-01-16 | Johnson Matthey Plc | Catalyst and method for its preparation |
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| CN104549401A (en) * | 2013-10-28 | 2015-04-29 | 天津大学 | Nonmetallic catalyst for acetylene hydrochlorination, as well as preparation method and application |
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