CN111229274B - High-energy mechanical ball-milling SiC Lewis acid catalyst and preparation method and application thereof - Google Patents
High-energy mechanical ball-milling SiC Lewis acid catalyst and preparation method and application thereof Download PDFInfo
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/20—Carbon compounds
- B01J27/22—Carbides
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
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Abstract
The invention discloses a high-energy mechanical ball milling SiC Lewis acid catalyst, a preparation method thereof and application thereof, wherein the preparation of the high-energy mechanical ball milling SiC Lewis acid catalyst comprises the following steps: placing SiC in an oven for drying, weighing SiC with a certain mass, placing the SiC in a ball milling tank, adding grinding balls with corresponding sizes in proportion, placing the SiC in a ball milling machine for high-energy mechanical ball milling under a set ball milling condition to prepare the high-energy mechanical ball milling SiC Lewis acid catalyst, wherein the ball milling condition comprises at least one of ball milling time, ball milling rotating speed, material of the ball milling tank and the grinding balls, and mass ratio of SiC raw materials and the grinding balls. The catalyst prepared by the invention is a SiC Lewis acid catalyst prepared by high-energy mechanical ball milling, and has good catalytic activity and stability in the reaction of preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane.
Description
Technical Field
The invention relates to a method for preparing a Lewis acid catalyst by utilizing high-energy mechanical ball milling and application thereof.
Background
The mechanochemical treatment (MCT) process is a non-hazardous treatment process operating in a ball mill and is considered to be a promising non-combustion process by high energy mechanical ball milling treatment. This method was used in this experiment because it consumes less energy and produces minimal harmful by-products.
Silicon carbide (SiC) is a very covalently strongly bonded semiconductor compound with a small band gap and a high electron transfer rate, and valence electrons of the semiconductor can be activated by light, electricity or heat and can jump to a conduction band to form free electrons. Meanwhile, the catalyst has the excellent characteristics of corrosion resistance, high temperature resistance, oxidation resistance, wear resistance, high mechanical strength, high heat conductivity coefficient, high heat conductivity, small thermal expansion coefficient and the like, and can effectively transfer reaction heat in the catalytic reaction process. It can maintain excellent chemical stability even under severe conditions, and thus it is a recyclable catalyst material, which is receiving much attention. Silicon carbide is widely used in various fields as a structural material, including abrasives, preparation of advanced refractory materials, functional ceramics and the like.
Mg, Al, Cr based catalysts such as magnesium oxide (MgO), magnesium fluoride (MgF) 2 ) Aluminum oxide (Al) 2 O 3 ) Aluminum fluoride (AlF) 3 ) Chromium oxide (Cr) 2 O 3 ) Chromium fluoride (CrF) 3 ) Or any Lewis acid catalyst containing other metals and metal oxides or metal halides, which is a common reaction for the dehydrofluorination of fluorine-containing alkanes to produce fluorine-containing olefins. However, these catalysts are easily deposited with carbon and sintered during the catalytic reaction, thereby deactivating the catalysts. The gas-phase catalytic dehydrofluorination process has good catalytic reaction performance for preparing fluorine-containing olefin by dehydrofluorinating fluorine-containing alkane under the condition of certain temperature under the action of the high-energy mechanical ball-milling SiC Lewis acid catalyst, can obtain higher product yield under normal conditions, greatly reduces the reaction temperature compared with a pyrolysis process, and greatly reduces the three wastes compared with a liquid-phase dehydrofluorination process, so that the gas-phase catalytic dehydrofluorination process is more suitable for industrial scale-up production relatively. However, the C-F bond energy in the fluorine-containing alkane is extremely high (450 KJ/mol or more, which is one of the chemical bonds having the highest bond energy). Therefore, in the reaction of preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane, the heat absorption capacity is extremely high, and the thermal conductivity of the catalyst directly influences the catalytic reaction performance. And SiC can effectively transfer reaction heat in the catalytic reaction process as a catalyst.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention aims to provide a preparation method and application of a high-energy mechanical ball-milling SiC Lewis acid catalyst. The catalyst prepared by the invention is a high-energy mechanical ball milling SiC Lewis acid catalyst. The catalyst synthesized by the method has good catalytic activity and stability in the reaction of preparing the fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane.
The preparation method of the high-energy mechanical ball-milling SiC Lewis acid catalyst is characterized by comprising the steps of firstly placing SiC in an oven for drying, then placing the dried SiC in a ball-milling tank, adding grinding balls with corresponding sizes in proportion, and placing the ball-milling tank in a ball mill for high-energy mechanical ball-milling under the set ball-milling condition to obtain the high-energy mechanical ball-milling SiC Lewis acid catalyst.
The preparation method of the high-energy mechanical ball milling SiC Lewis acid catalyst is characterized in that SiC is micron-sized or nano-sized SiC.
The preparation method of the high-energy mechanical ball-milling SiC Lewis acid catalyst is characterized in that SiC is dried in an oven at the temperature of 110 ℃ and 130 ℃ for 10-14h, preferably at the temperature of 120 ℃ for 12 h.
The preparation method of the high-energy mechanical ball-milling SiC Lewis acid catalyst is characterized in that the mass ratio of the SiC raw material to the grinding ball is 1: 5-20, preferably 1: 10.
the preparation method of the high-energy mechanical ball-milling SiC Lewis acid catalyst is characterized in that the ball-milling time is 0.5-4h, preferably 2 h; the ball milling rotating speed is 200-300r/min, preferably 300 r/min; the ball milling tank and the milling balls are made of stainless steel, corundum or quartz.
The high-energy mechanical ball-milling SiC Lewis acid catalyst prepared by the preparation method.
The application of the high-energy mechanical ball-milling SiC Lewis acid catalyst in the reaction of preparing the fluorine-containing olefin by dehydrofluorination of the fluorine-containing alkane is characterized in that the reaction temperature of the reaction of preparing the fluorine-containing olefin by dehydrofluorination of the fluorine-containing alkane is 300-400 ℃, and the reaction pressure is normal pressure.
Compared with the prior art, the invention has the following beneficial effects:
1) the method ball-mills commercial SiC to obtain the high-energy mechanical ball-milling SiC Lewis acid catalyst by a high-energy mechanical ball-milling method, and the preparation method has mild conditions, short preparation period, safety, greenness and environmental protection;
2) the high-energy mechanical ball milling SiC Lewis acid catalyst is applied to a reaction system for preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane for the first time, the heat absorption capacity of the reaction for preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane is extremely high, and the thermal conductivity of SiC is good (high thermal conductivity coefficient, high thermal conductivity and small thermal expansion coefficient), so that the catalyst can directly and effectively transfer reaction heat in the catalytic reaction process, the temperature of a catalyst bed layer is reduced, the catalyst is prevented from sintering carbon deposition under the high-temperature condition, the reduction of the reaction active sites of the catalyst is prevented, and the catalytic performance of the catalyst in the reaction for preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane is improved;
3) compared with the traditional Mg, Al and Cr-based catalyst, the high-energy mechanical ball-milling SiC Lewis acid catalyst disclosed by the invention is resistant to HF corrosion, has good chemical stability in the reaction process, is resistant to carbon deposition and sintering in the catalytic reaction process, is not easy to inactivate, still has high catalytic reaction performance after long-time catalytic reaction, prolongs the service life of the catalyst and reduces the cost.
Detailed Description
The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.
Example 1
After the product SiC was dried in an oven at 110 ℃ for 10 hours, 2.75g of the product SiC was weighed and placed in a corundum ball milling jar of which the specification was 0.4L, according to a 1: adding corundum grinding balls with corresponding sizes according to the mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 0.5h, ball milling rotating speed is 200 r/min) to obtain the SiC Lewis acid catalyst prepared by high-energy mechanical ball milling.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 0.5h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack and prepare fluoroethylene, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The sampling analysis result of the reaction 2h is as follows: the conversion of the reactant HFC-152a was 25.7% and the selectivity of the product Vinyl Fluoride (VF) was 100%. After 5h of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 7.8 percent, and the selectivity of the product is basically kept unchanged. Compared with comparative example 1, the high energy mechanical ball milling SiC Lewis acid catalyst effectively improves the activity.
Example 2
After the product SiC was dried in an oven at 130 ℃ for 14 hours, 2.75g of the product SiC was weighed and placed in a corundum ball milling jar of a specification of 0.4L, according to a ratio of 1: adding corundum grinding balls with corresponding sizes according to the mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 0.5h, ball milling rotating speed is 200 r/min) to obtain the SiC Lewis acid catalyst prepared by high-energy mechanical ball milling.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 0.5h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack and prepare fluoroethylene, and the reaction formula is as follows:
the reaction conditions are as follows: filling the catalyst into a fixed bed reactor, wherein the filling amount of the catalyst is 2mL, and introducing N 2 Mixed gas of HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a was 31.5% and the selectivity of the product Vinyl Fluoride (VF) is 100%. After 5h of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 14.9 percent, and the selectivity of the product is basically kept unchanged.
Example 3
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 2.75g of the product SiC was weighed and placed in a corundum ball-milling jar, the specification of which was 0.4L, according to a weight ratio of 1: adding corundum grinding balls with corresponding sizes according to the mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 0.5h, ball milling rotating speed is 200 r/min) to obtain the SiC Lewis acid catalyst prepared by high-energy mechanical ball milling.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 0.5h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a was 35.8%, and the selectivity of the product Vinyl Fluoride (VF) was 100%. And as a result of sampling and analyzing after 5 hours of reaction, the conversion rate of the reactant is reduced to 19.6%, and the selectivity of the product is basically kept unchanged. Compared with the examples 1,2 and 3, the SiC is dried in an oven at 120 ℃ for 12 hours, and the activity of the high-energy mechanical ball milling SiC Lewis acid catalyst is the best.
Example 4
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 2.75g of the product SiC was weighed and placed in a corundum ball milling jar of which the specification was 0.4L, according to a 1: adding corundum grinding balls with corresponding sizes according to the mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 0.5h, ball milling rotating speed is 300 r/min) to obtain the SiC Lewis acid catalyst prepared by high-energy mechanical ball milling.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 0.5h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack and prepare fluoroethylene, and the reaction formula is as follows:
the reaction conditions are as follows: filling the catalyst into a fixed bed reactor, wherein the filling amount of the catalyst is 2mL, and introducing N 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a is 40.1%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. After 5h of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 22.3 percent, and the selectivity of the product is basically kept unchanged. Compared with examples 3 and 4, the ball milling speed is increased, and the activity of the high-energy mechanical ball milling SiC Lewis acid catalyst is improved.
Example 5
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 2.75g of the product SiC was weighed and placed in a quartz ball mill jar, the specification of which was 0.4L, according to a 1: adding quartz grinding balls with corresponding sizes in a mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 1h, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 1h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixed gas of HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a is 21.6%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. And sampling and analyzing after 5 hours of reaction, wherein the conversion rate of the reactant is reduced to 7.2%, and the selectivity of the product is basically kept unchanged.
Example 6
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a quartz ball mill jar of 0.4L in the specification of 1: 10, adding quartz grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 1h, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 1h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: filling the catalyst into a fixed bed reactor, wherein the filling amount of the catalyst is 2mL, and introducing N 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The sampling analysis result of the reaction 2h is as follows: the conversion of the reactant HFC-152a is 25.6%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. After 5h of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 16.4 percent, and the selectivity of the product is basically kept unchanged. Compared with examples 5 and 6, when the ball milling time is 1h, the mass ratio of the SiC raw material to the grinding balls is 1: at 10, the catalyst activity is highest.
Example 7
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 2.75g of the product SiC was weighed and placed in a corundum ball milling jar of which the specification was 0.4L, according to a 1: adding corundum grinding balls with corresponding sizes in a mass ratio of 20, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under set ball milling conditions (ball milling time is 2 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 2h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixed gas of HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The sampling analysis result of the reaction 2h is as follows: the conversion of the reactant HFC-152a is 42.7%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. And sampling and analyzing after 5 hours of reaction, reducing the conversion rate of the reactant to 39.1 percent, and basically keeping the selectivity of the product unchanged. Compared with examples 4, 5 and 7, when the mass ratio of the SiC raw material to the grinding balls is 1: when the time is 20 hours, the activity of the catalyst is the highest when the ball milling time is 2 hours.
Example 8
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a corundum ball milling jar of which the specification was 0.4L, according to a 1: 10, adding corundum grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 2 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 2h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixing with HFC-152aSynthetic gas, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a is 61.6%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. And according to the result of sampling analysis after 30 hours of reaction, the conversion rate of a reactant is reduced to 43.4%, the selectivity of a product is basically kept unchanged, and the catalyst is kept stable after 8 hours. Compared with examples 7 and 8, when the ball milling time is 2 hours, the mass ratio of the SiC raw material to the grinding balls is 1: at 10, the catalyst activity is highest.
Example 9
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a stainless steel ball milling jar of 0.4L specification, as 1: 10, adding stainless steel grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 2 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 2h is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a is 73.9 percent, and the selectivity of the product Vinyl Fluoride (VF) is 100 percent. And (3) sampling and analyzing the result after 30h of reaction, wherein the conversion rate of the reactant is reduced to 56.1%, the selectivity of the product is basically kept unchanged, and the catalyst is kept stable after 8 h. Compared with examples 8 and 9, the materials of the stainless steel ball milling tank and the grinding ball improve the activity of the high-energy mechanical ball milling SiC Lewis acid catalyst.
Example 10
After the commercial SiC product is dried in an oven at 120 ℃ for 12 hours, 11g of the commercial SiC product is weighed and placed in a stainless steel ball milling tank, the specification of the ball milling tank is 0.4L, and the weight percentage is as follows: 5, adding stainless steel grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 4 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 4 hours is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack and prepare fluoroethylene, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixed gas of HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a is 17.8%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. And as a result of sampling analysis after 10 hours of reaction, the conversion rate of the reactant is reduced to 10.2%, and the selectivity of the product is basically kept unchanged.
Example 11
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a stainless steel ball milling jar of 0.4L specification, as 1: 10, adding stainless steel grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 4 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 4 hours is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack to prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The result of sampling analysis in 2h of reaction is: the conversion of the reactant HFC-152a was 63.6% and the selectivity of the product Vinyl Fluoride (VF) was 100%. And (3) sampling and analyzing the result after 30h of reaction, reducing the conversion rate of the reactant to 42.4%, basically keeping the selectivity of the product unchanged, and keeping the catalyst stable after 8 h. Compared with examples 6, 8 and 11, when the mass ratio of the SiC raw material to the grinding balls is 1: when 10 hours are spent, the ball milling time is prolonged before 2 hours, and the activity of the catalyst is improved; the catalyst activity was comparable for ball milling times of 2h and 4 h. Compared with examples 10 and 11, when the ball milling time is 4 hours, the mass ratio of the SiC raw material to the grinding balls is 1: at 10, the catalyst activity is highest.
Example 12
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a stainless steel ball milling jar of 0.4L specification, as 1: 10, adding stainless steel grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 2 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 2h is used for catalyzing 1,1,1, 2-tetrafluoroethane (HFC-134a) to crack and prepare 1,1, 2-trifluoroethylene, and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixed gas of HFC-134a and N 2 The flow rate is 5mL/min, the HFC-134a flow rate is 5mL/min, and the space velocity of the HFC-134a is 300h -1 The reaction temperature was 400 ℃. The result of sampling analysis in 2h of reaction is: conversion of the reactant HFC-134aThe rate was 35.6% and the selectivity to 1,1, 2-trifluoroethylene, product, was 100%. After 10 hours of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 16.4 percent, and the selectivity of the product is basically kept unchanged.
Example 13
After the product SiC was dried in an oven at 120 ℃ for 12 hours, 5.5g of the product SiC was weighed and placed in a stainless steel ball milling jar of 0.4L specification, as 1: 10, adding stainless steel grinding balls with corresponding sizes, and finally placing the mixture in a ball mill for high-energy mechanical ball milling under the set ball milling condition (ball milling time is 2 hours, ball milling rotating speed is 300 r/min) to obtain the high-energy mechanical ball milling SiC Lewis acid catalyst.
The SiC Lewis acid catalyst prepared by the high-energy mechanical ball milling for 2h is used for catalyzing 1,1,1,3, 3-pentafluoropropane (HFC-245fa) to crack to prepare 1,3,3, 3-tetrafluoropropene (HFO-1234 ze), and the reaction formula is as follows:
the reaction conditions are as follows: the catalyst is filled into a fixed bed reactor, the filling amount of the catalyst is 2mL, and N is introduced 2 Mixed gas of HFC-245fa, N 2 The flow rate is 20mL/min, the HFC-245fa flow rate is 5mL/min, and the space velocity of the HFC-245fa is 750h -1 The reaction temperature was 350 ℃. The sampling analysis result of the reaction 2h is as follows: the conversion of reactant 1,1,1,3, 3-pentafluoropropane was 41.6%, and the selectivity of product cis-trans 1,3,3, 3-tetrafluoropropene (HFO-1234 ze) was 100%. After 10 hours of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 27.4 percent, and the selectivity of the product is basically kept unchanged.
Comparative example 1
1.8510g (2 mL) of commercial SiC is weighed and placed in an oven to be dried for 12 hours at 120 ℃, and the commercial SiC catalyst is obtained.
The commercial SiC catalyst prepared in the above way is used for catalyzing 1, 1-difluoroethane (HFC-152 a) to crack and prepare vinyl fluoride, and the reaction formula is as follows:
the reaction conditions are as follows: filling the catalyst into a fixed bed reactor, wherein the filling amount of the catalyst is 2mL, and introducing N 2 And HFC-152a, N 2 The flow rate is 5mL/min, the HFC-152a flow rate is 5mL/min, and the space velocity of the HFC-152a is 300h -1 The reaction temperature was 300 ℃. The sampling analysis result of the reaction 2h is as follows: the conversion of the reactant HFC-152a is 25.3%, and the selectivity of the product Vinyl Fluoride (VF) is 100%. After 5h of reaction, sampling and analyzing results show that the conversion rate of the reactant is reduced to 5.1 percent, and the selectivity of the product is basically kept unchanged.
To sum up, the high-energy mechanical ball milling SiC Lewis acid catalyst is dried in a SiC raw material oven at 120 ℃ for 12 hours, the ball milling time is 2 hours, the ball milling speed is 300r/min, and the mass ratio of the SiC raw material to the grinding balls is 1: 10, the ball milling tank and the milling balls are made of stainless steel, the ball milling effect is good, and the high-energy mechanical ball milling SiC Lewis acid catalyst has the highest activity and the best stability in the reaction of catalyzing the cracking of 1, 1-difluoroethane (HFC-152 a) to prepare vinyl fluoride.
The statements in this specification merely set forth a list of implementations of the inventive concept and the scope of the present invention should not be construed as limited to the particular forms set forth in the examples.
Claims (9)
1. The application of the high-energy mechanical ball-milling SiC Lewis acid catalyst in the reaction of preparing fluorine-containing olefin by dehydrofluorination of fluorine-containing alkane is characterized in that the preparation method of the high-energy mechanical ball-milling SiC Lewis acid catalyst comprises the following steps: firstly, drying SiC in an oven, then placing the dried SiC in a ball milling tank, adding grinding balls matched with corresponding sizes in proportion, placing the mixture in a ball mill for high-energy mechanical ball milling under a set ball milling condition, and obtaining the high-energy mechanical ball milling SiC Lewis acid catalyst.
2. Use according to claim 1, wherein the SiC is micron or nano-sized SiC.
3. The method as claimed in claim 1, wherein the SiC is dried in an oven at 110-130 ℃ for 10-14 h.
4. Use according to claim 1, characterized in that the SiC is dried in an oven at 120 ℃ for 12 h.
5. The use according to claim 1, wherein the mass ratio of the SiC starting material to the grinding balls is 1: 5-20.
6. The use according to claim 1, wherein the mass ratio of the SiC starting material to the grinding balls is 1: 10.
7. use according to claim 1, characterized in that the ball milling time is between 0.5 and 4 h; the ball milling rotating speed is 200-; the material of the ball milling tank and the grinding ball is stainless steel, corundum or quartz.
8. Use according to claim 1, characterized in that the ball milling time is 2 h; the ball milling speed is 300 r/min.
9. The application of claim 1, wherein the reaction temperature for preparing the fluorine-containing olefin by dehydrofluorination of the fluorine-containing alkane is 300-400 ℃, and the reaction pressure is normal pressure.
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|---|---|---|---|---|
| US2599631A (en) * | 1945-12-06 | 1952-06-10 | Du Pont | Preparation of vinyl fluoride |
| US5880315A (en) * | 1996-11-21 | 1999-03-09 | E. I. Du Pont De Nemours And Company | Catalytic manufacture of vinyl fluoride |
| CN102616781A (en) * | 2012-04-01 | 2012-08-01 | 昆明理工大学 | Method for preparing SiC ultrafine powder |
| CN103846101A (en) * | 2012-11-28 | 2014-06-11 | 中国科学院大连化学物理研究所 | C-SiC catalyst, its preparation and its application thereof |
| CN103920484A (en) * | 2013-01-14 | 2014-07-16 | 中化蓝天集团有限公司 | Catalyst for hydrofluorination reaction of acetylene to prepare vinyl fluoride and 1,1-difluoroethane, and preparation method and application thereof |
| CN104445200A (en) * | 2014-11-17 | 2015-03-25 | 哈尔滨工业大学 | Method for preparing super-long silicon carbide nano-wires |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2599631A (en) * | 1945-12-06 | 1952-06-10 | Du Pont | Preparation of vinyl fluoride |
| US5880315A (en) * | 1996-11-21 | 1999-03-09 | E. I. Du Pont De Nemours And Company | Catalytic manufacture of vinyl fluoride |
| CN102616781A (en) * | 2012-04-01 | 2012-08-01 | 昆明理工大学 | Method for preparing SiC ultrafine powder |
| CN103846101A (en) * | 2012-11-28 | 2014-06-11 | 中国科学院大连化学物理研究所 | C-SiC catalyst, its preparation and its application thereof |
| CN103920484A (en) * | 2013-01-14 | 2014-07-16 | 中化蓝天集团有限公司 | Catalyst for hydrofluorination reaction of acetylene to prepare vinyl fluoride and 1,1-difluoroethane, and preparation method and application thereof |
| CN104445200A (en) * | 2014-11-17 | 2015-03-25 | 哈尔滨工业大学 | Method for preparing super-long silicon carbide nano-wires |
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