Hydrogenation dehalogenation catalyst and preparation method of chlorotrifluoroethylene and trifluoroethylene
阅读说明：本技术 加氢脱卤催化剂和三氟氯乙烯与三氟乙烯的制备方法 (Hydrogenation dehalogenation catalyst and preparation method of chlorotrifluoroethylene and trifluoroethylene ) 是由 廖湘洲 粟小理 陆子薇 胡总 卢磊 杜丽君 赖春波 陆艳萍 郑渝佳 于 2021-09-22 设计创作，主要内容包括：公开了加氢脱卤催化剂和三氟氯乙烯与三氟乙烯的制备方法。所述加氢脱卤催化剂用的催化剂载体包括由多孔碳基质和金属卤化物改性剂烧制形成的多孔碳-金属卤化物复合物,按重量计,所述催化剂载体中金属卤化物的量占0.01～10％。(Disclosed are a hydrodehalogenation catalyst and a preparation method of chlorotrifluoroethylene and trifluoroethylene. The catalyst carrier for the hydrodehalogenation catalyst comprises a porous carbon-metal halide compound formed by firing a porous carbon substrate and a metal halide modifier, wherein the amount of metal halide in the catalyst carrier accounts for 0.01-10% by weight.)
1. A catalyst carrier for a hydrodehalogenation catalyst comprises a porous carbon-metal halide compound formed by firing a porous carbon substrate and a metal halide modifier, wherein the amount of metal halide in the catalyst carrier accounts for 0.01-10% by weight.
2. The catalyst support according to claim 1, characterized in that the metal halide comprises one or more halides, preferably chlorides or fluorides, preferably fluorides, selected from the group consisting of magnesium, aluminium, calcium, barium, potassium, iron and chromium.
3. The catalyst carrier according to claim 1 or 2, wherein pores having a pore diameter of 2 to 50nm in the carbon substrate account for 50 to 99%, preferably 60 to 98%, more preferably 70 to 95%.
4. The catalyst support according to claim 1 or 2, characterized in that it is obtained by a process comprising:
treating the porous carbon matrix with a metal halide solution or sol-gel so that the amount of the metal halide salt in the formed treated porous carbon matrix is 0.01-10% by weight, and then drying and firing the porous carbon matrix in an inert atmosphere at a temperature of 250-400 ℃ for 2-6 hours.
5. A hydrodehalogenation catalyst comprising a procatalyst palladium and a cocatalyst selected from one or more of ruthenium, copper, cesium, silver, indium, zinc, nickel, lanthanum, cerium, zirconium, titanium, chromium, aluminum, cobalt, niobium, tantalum, platinum, manganese, rhodium supported on a catalyst support according to any one of claims 1 to 4.
6. The hydrodehalogenation catalyst according to claim 5, wherein the amount of palladium element of the main catalyst is 0.01 to 1% by weight, preferably 0.02 to 0.9% by weight, more preferably 0.03 to 0.8% by weight, preferably 0.04 to 0.7% by weight, preferably 0.05 to 0.6% by weight; the amount of the cocatalyst is 0 to 5%, preferably 0.3 to 4.8%, more preferably 0.8 to 4.2%, preferably 1.2 to 3.8%, and most preferably 2 to 3.5%.
7. The hydrodehalogenation catalyst according to claim 5 or 6, which is prepared by the following method:
providing a catalyst support according to any one of claims 1 to 4;
forming an acidic aqueous solution of a soluble palladium salt, impregnating the acidic aqueous solution into the catalyst carrier, drying and roasting the catalyst carrier;
an acidic aqueous solution of the promoter is formed and impregnated with the dried and calcined catalyst precursor and calcined at 350-.
8. A method for preparing chlorotrifluoroethylene and trifluoroethylene by hydrodechlorination of 1, 12-trifluorotrichloroethane comprises the following steps:
providing a hydrodehalogenation catalyst according to any one of claims 5-6;
the reactants 1,1, 2-trifluorotrichloroethane and hydrogen were passed through a catalyst bed.
9. The method of claim 8, wherein the catalyst is dried and reduced prior to use, the drying atmosphere being nitrogen and the reducing atmosphere being hydrogen or a hydrogen diluent gas; the drying temperature is 100-300 ℃, preferably 120-220 ℃. The reduction temperature is 100-450 ℃, preferably 200-350 ℃.
10. Use of the hydrodehalogenation catalyst according to claim 5 or 6 for the hydrodechlorination of 1, 12-trifluorotrichloroethane to chlorotrifluoroethylene and trifluoroethylene.
Technical Field
The invention relates to a hydrogenation dehalogenation catalyst and a method for simultaneously preparing chlorotrifluoroethylene and trifluoroethylene. The catalysts of the invention have, in addition to improved product selectivity, improved service life, which reduces operating costs.
Technical Field
Fluorine-containing olefins such as Chlorotrifluoroethylene (CTFE) and trifluoroethylene (TrFE) have high added values in the field of fluorine chemical industry, are key monomers for synthesizing fluorine-containing materials such as fluororubber, fluororesin and fluorine paint, and are also one of important raw materials of fluorine-containing fine chemicals. At present, zinc powder is mainly adopted in the industry to reduce 1,1, 2-trifluorotrichloroethane to prepare CTFE, but the zinc powder consumption of the route is large, the environmental protection cost is high, and a new process route is urgently needed to replace the zinc powder.
The synthesis of trifluoroethylene (TrFE) mainly comprises CTFE hydrogenation and tetrafluoroethane (HFC-134a) cracking routes, but the large-scale industrial application of the trifluoroethylene is still limited due to the limited raw material sources and the immature catalytic technology at present.
The 1,1, 2-trifluoro trichloroethane is polychlorinated fluorine-containing alkane with wide application and can be used as an important raw material for synthesizing fluorine-containing olefin. It has been reported that Chlorotrifluoroethylene (CTFE) is prepared by hydrogenation and dechlorination through the reaction of 1,1, 2-trifluorotrichloroethane (CFC-113) and hydrogen, and trifluoroethylene (TrFE) is prepared by hydrogenation of chlorotrifluoroethylene, so that chlorofluoroalkane is effectively converted into fluorine-containing olefin, the conversion of CFC-113 to high value-added chemicals is promoted, and the environmental protection problems of chlorofluoroalkane greenhouse effect, ozone destruction and the like are solved. Thermodynamically, CFC-113 hydrogenation easily produces fluorine-containing alkane, and relatively lower reaction temperature and lower hydrogen partial pressure are selected to favor the production of fluorine-containing olefin. Therefore, the generation of chlorotrifluoroethylene and trifluoroethylene in this reaction is not only influenced by the reaction process conditions, but more importantly, the catalyst plays a very important role in controlling the hydrodechlorination route and progress of polychlorinated fluorine-containing alkanes like CFC-113.
Ohnishi, R., W. -L.Wang and M.Ichikawa "Selective hydrodechlorination of CFC-113 over Bi-and Tl-modified Palladium catalysts" with bismuth and thallium-modified Palladium catalysts "Applied Catalysis A: General 113(1):29-41, 1994) reported that palladium-supported catalysts are used for CFC-113 hydrogenation, and that different catalysts can achieve better selectivity for chlorotrifluoroethylene or trifluoroethylene with suitable promoters, e.g., trifluoroethylene as the main product with Bi as promoter, up to 86% selectivity for chlorotrifluoroethylene and chlorotrifluoroethylene as the main product with Tl as promoter, up to 98%. However, studies have found that both of these types of catalysts suffer from different degrees of deactivation.
Chinese patent CN1065261 discloses that a noble metal supported activated carbon catalyst with copper as a cocatalyst can be used for the hydrodechlorination of 1,1, 2-trifluorotrichloroethane to prepare chlorotrifluoroethylene and trifluoroethylene, the generation ratio of chlorotrifluoroethylene and trifluoroethylene can be changed by adjusting the content of copper, meanwhile, the ratio of different noble metals such as palladium and platinum also has an influence on the former, the selectivity of chlorotrifluoroethylene and trifluoroethylene is usually more than 90%, but the service life of the catalyst is not long, and the deactivation phenomenon occurs after 300 hours of reaction.
Chinese patent CN1460549 reports that a catalyst using coconut shell carbon as a carrier and copper palladium as a main active component is used for preparing CTFE by CFC-113 hydrodechlorination, and it is found that the selectivity (> 85%) of CTFE can be significantly improved by using part of alkali metals and alkaline earth metals as a modifier, but the catalyst still has an obvious deactivation phenomenon, and the service life is less than 1000 hours.
Chinese patent CN105457651 discloses a catalyst with active carbon loaded with copper-palladium alloy as a main active component, wherein the reaction temperature is 190-320 ℃, and the space velocity of raw materials is 50-150 h-1Under the conditions of (1), can obtainHigher CFC-113 conversion rate (-96%) and CTFE selectivity (-95%) are obtained, and the reaction also shows better stability. However, the hydrogenation product is mainly CTFE, and high-quality trifluoroethylene TrFE cannot be obtained, i.e. the existing catalyst and reaction process cannot meet the requirement of simultaneously preparing CTFE and TrFE.
Chinese patent CN111683919A teaches that in the gas phase dechlorination of 1,1, 2-trichloro-1, 2, 2-trifluoroethane with hydrogen to prepare CTFE, the space velocity of the catalyst supported by active carbon is often not more than about 500hr-1And this is uneconomical for industrial use, and for this reason, it is proposed to react ethylene, ethane, etc. with 1,1, 2-trichloro-1, 2, 2-trifluoroethane to prepare CTFE. The method further improves the space velocity, increases the yield, and effectively produces other valuable chlorinated alkenes as byproducts, but the reaction temperature is overhigh, the byproducts basically do not produce trifluoroethylene, and the impurity distribution is more.
In addition, in order to improve the hydrodechlorination catalyst, metal fluoride, particularly aluminum fluoride, is adopted to replace activated carbon to prepare the Pd-Cu supported catalyst, and higher chlorotrifluoroethylene selectivity or trifluoroethylene selectivity can be obtained in the hydrogenation reaction of trifluorotrichloroethane and chlorotrifluoroethylene, for example, Chinese patents CN106140193A, CN106890662B, CN109261175A and the like are published and reported. However, in the preparation process of the carrier, since metal fluorides such as aluminum fluoride and the like generally have a low specific surface area and limited loading and dispersion of active metals, it is difficult to prepare the catalyst by using the metal fluorides alone as the carrier, and even if a special method is used to prepare aluminum fluoride with a high specific surface area, a large amount of alumina components still exist, which is disadvantageous to hydrogenation catalysts and long-term operation reactions in an atmosphere such as hydrogen chloride or hydrogen fluoride, and the long-term service life of the catalyst is questionable compared with that of a catalyst directly loaded on activated carbon.
Although the existing catalyst can achieve higher CFC-113 conversion rate, the performance of the catalyst is mostly aimed at improving the selectivity of CTFE, the attention of other products in hydrogenation is less, high-quality TrFE is difficult to obtain, and undesirable impurities of fluorine-containing olefin are reduced as much as possible according to the requirements of polymer monomers. Meanwhile, in order to meet the requirements of industrial application, the hydrogenation reaction process, the catalyst and the reaction stability of the chlorotrifluoroethylene prepared by hydrogenation of trifluorotrichloroethane ethane, particularly the chlorotrifluoroethylene and trifluoroethylene prepared simultaneously, still need to be improved.
Accordingly, there remains a need in the art to provide a hydrodehalogenation catalyst having high product selectivity with improved service life. There is also a need in the art to provide processes for the preparation of chlorotrifluoroethylene and trifluoroethylene using the above catalysts.
Disclosure of Invention
It is an object of the present invention to provide a hydrodehalogenation catalyst having a high product selectivity with an improved service life. It is another object of the present invention to provide a process for preparing chlorotrifluoroethylene and trifluoroethylene using the above catalyst.
Accordingly, one aspect of the present invention relates to a catalyst support for a hydrodehalogenation catalyst, which comprises a porous carbon-metal halide composite formed by firing a porous carbon matrix and a metal halide modifier, wherein the amount of the metal halide in the catalyst support is 0.01 to 10% by weight.
Another aspect of the invention relates to a hydrodehalogenation catalyst which comprises a main catalyst palladium and a cocatalyst selected from one or more of ruthenium, copper, cesium, silver, indium, zinc, nickel, lanthanum, cerium, zirconium, titanium, chromium, aluminum, cobalt, niobium, tantalum, platinum, manganese and rhodium, which are supported on the porous carbon support.
Another aspect of the invention relates to a process for the hydrodechlorination of 1, 12-trifluorotrichloroethane to chlorotrifluoroethylene and trifluoroethylene comprising:
providing the hydrodehalogenation catalyst;
the reactants 1,1, 2-trifluorotrichloroethane and hydrogen were passed through a catalyst bed.
In a further aspect, the present invention relates to the use of the above-described hydrodehalogenation catalyst of the present invention in the hydrodechlorination of 1, 12-trifluorotrichloroethane to chlorotrifluoroethylene and trifluoroethylene.
Detailed Description
A. Hydrodehalogenation catalyst
The hydrodehalogenation catalyst comprises a main catalyst, a cocatalyst and a carrier.
1. Main catalyst
The main catalyst in the catalyst of the invention comprises palladium element, which can be present in the hydrodehalogenation catalyst in the form of metal simple substance and/or metal oxide. The amount of the main catalyst is 0.05-1.5%, preferably 0.08-1.2%, more preferably 0.1-1.0%, and preferably 0.2-0.9% based on the total weight of the hydrodehalogenation catalyst.
2. Co-catalyst
The cocatalyst suitable for the hydrodehalogenation catalyst of the present invention is not particularly limited, and may be a conventional cocatalyst element known in the art, for example, it may be a catalyst element disclosed in CN111013604A and CN 105944734A. In one embodiment of the present invention, the promoter element is selected from one or a combination of two or more of ruthenium, copper, nickel, silver, indium, cesium, lanthanum, cerium, zinc, zirconium, titanium, chromium, aluminum, cobalt, niobium, tantalum, platinum, manganese, rhodium, preferably from one or a combination of two or more of ruthenium, copper, nickel, silver, indium, cesium, lanthanum, cerium, zinc, zirconium. The promoter may be present in the hydrodehalogenation catalyst in the form of elemental metal and/or metal oxide and/or metal halide.
The amount of the cocatalyst is 0 to 5%, preferably 0.05 to 4.5%, more preferably 0.2 to 4%, most preferably 0.5 to 3.5%, preferably 0.8 to 3%, and most preferably 1.2 to 2.5%, based on the total weight of the hydrodehalogenation catalyst.
3. Carrier
The carrier used by the hydrodehalogenation catalyst is a porous carbon carrier modified by metal halide, and is formed by firing a porous carbon substrate and a metal halide modifier.
The porous carbon substrate suitable for the hydrodehalogenation catalyst carrier of the present invention is not particularly limited, and may be a porous carbon carrier known in the art as a hydrodehalogenation catalyst carrier, for example, it may be coconut shell activated carbon disclosed in CN1351903 or a specific surface area of more than 500g/m disclosed in CN111013604A2And the pore volume is 1-10cm3Per gram of activated carbon treated with conventional acids.
In one embodiment of the present invention, the porous carbon matrix comprises activated carbon commonly used in the art, such as coconut shell carbon, coal carbon, shell carbon, pitch carbon, and ligneous carbon, or a mixture of two or more thereof, and porous carbides known in the art, such as mesoporous carbon molecular sieves, carbon aerogels, carbon fibrils and nanotubes, and phenolics, may also be used.
In one example of the invention, the porous carbon matrix comprises micropores (<2nm), mesopores (2-50 nm) and macropores (>50nm), wherein 50-99%, preferably 60-98%, more preferably 70-95% of the pores are mesopores. Such a carbon matrix is commercially available, for example, from the national pharmaceutical group chemical agents limited under the trade names "granular activated carbon", "mesoporous carbon".
In one embodiment of the present invention, the porous carbon may be surface-oxidatively modified to increase its hydrophilicity, specific surface area, pore distribution, and the like. The surface oxidation modification method to be used is not particularly limited, and may be a conventional method known in the art, for example, an oxidation modification method of activated carbon mentioned in "influence of nitric acid treatment on properties of activated carbon" of the recipe and the like (chemical and biological engineering, vol.28, No. 5, 2011).
The carrier of the hydrodehalogenation catalyst is modified by metal halide. The metal halide to be used is not particularly limited. In one embodiment of the invention, the metal halide is selected from the group consisting of alkali metal halides, alkaline earth metal halides, group VIB metal halides, group VIII metal halides, or mixtures thereof. In one embodiment of the invention, the metal halide comprises one or more halides, preferably chlorides or fluorides, preferably fluorides, selected from magnesium, aluminium, calcium, barium, potassium, iron and chromium.
In the carrier of the hydrodehalogenation catalyst, the metal halide accounts for 0.01-10%, preferably 0.03-8%, more preferably 0.05-5%, most preferably 0.1-3%, and most preferably 0.2-2% by weight.
The hydrogenation dehalogenation catalyst carrier is a compound formed by firing metal halide and a porous carbon substrate. The applicable manufacturing method is not particularly limited, and may be a conventional method for forming a composite known in the art. In one embodiment of the invention, the method of forming the composite comprises treating a porous carbon support with a metal halide followed by firing. In the present invention, the term "treating the porous carbon support with a metal halide" means contacting the metal halide with the porous carbon support to attach it to the porous carbon support. Non-limiting examples of the "treatment" method include, for example, a solution spraying method, an excess impregnation method, an equal volume impregnation method, a sol-gel method, and the like.
In one embodiment of the present invention, the excess impregnation method comprises the steps of:
1) the soluble metal halide salt is mixed and impregnated with the porous carbon matrix, and in one embodiment of the present invention, the metal halide salt solution is suitably used at a concentration of 0.01 to 1M, preferably 0.03 to 0.8M, more preferably 0.04 to 0.6M; the solid-liquid weight ratio of the solution to the porous carbon substrate is 100-10:1, preferably 90-15: 1, more preferably 80-20: 1 and adjusting the pH to a pH < 2. Suitable methods for adjusting pH are not particularly limited, and may be pH adjusting methods conventional in the art, for example, adjusting pH with KOH, KF, hydrochloric acid and hydrofluoric acid to a final pH < 2;
2) mixing and dipping for 4-12 hours, preferably 5-10 hours, more preferably 6-8 hours, and then washing and drying in turn, wherein the drying temperature is 80-150 ℃, preferably 90-140 ℃, more preferably 100-; the drying time is 2-12 hours, preferably 3-10 hours, more preferably 4-8 hours;
3) the dried solid is calcined at 300-700 deg.C, preferably 350-650 deg.C, more preferably 400-600 deg.C under the protection of inert gas (such as nitrogen) for 0.5-8 hours, preferably 1-7 hours, more preferably 2-6 hours.
In one embodiment of the present invention, the isovolumetric impregnation method comprises the steps of:
1) the saturated adsorption capacity of the porous carbon substrate to deionized water (the volume of deionized water used for adsorbing deionized water per unit mass of the porous carbon substrate to wet the surface at 25 ℃) was tested by a conventional method, and the soluble metal halide salt was prepared as an aqueous solution, and the porous carbon was impregnated with the same volume. In one embodiment of the present invention, the concentration of the metal halide salt solution is controlled to be 0.01 to 1M, preferably 0.3 to 0.8M, more preferably 0.4 to 0.6M;
2) isovolumetrically impregnating said porous carbon with said metal halide salt solution;
3) drying the impregnated porous carbon matrix at the drying temperature of 80-150 ℃, preferably 90-140 ℃, more preferably 100-130 ℃; the drying time is 2-12 hours, preferably 3-10 hours, more preferably 4-8 hours;
optionally repeating the above impregnation and drying steps until a desired excess amount of metal halide is achieved;
4) the dried solid is calcined at 300-700 deg.C, preferably 350-650 deg.C, more preferably 400-600 deg.C under the protection of inert gas (such as nitrogen) for 0.5-8 hours, preferably 1-7 hours, more preferably 2-6 hours.
In one example of the present invention, the sol-gel method comprises the steps of:
1) a soluble halide metal alkoxide, a surfactant, and water are formed into a sol solution. In one embodiment of the present invention, the concentration of the halide metal alkoxide is 0.01 to 1M, preferably 0.03 to 0.8M, more preferably 0.04 to 0.6M; the concentration of the surfactant is 0.01-1M, preferably 0.05-0.95M, more preferably 0.1-0.9M, and preferably 0.15-0.85M;
the surfactant to be used is not particularly limited, and may be a conventional surfactant known in the art. In one embodiment of the present invention, the surface adsorbent is selected from CTAB (cetyltrimethylammonium bromide) of the national reagent group ltd;
2) dropwise adding the sol solution into a dispersion liquid formed by a porous carbon substrate and water, wherein the solid content of the dispersion liquid is 10-60%, preferably 15-55%, more preferably 20-50% by weight, further dropwise adding hydrofluoric acid or hydrochloric acid under continuous stirring until the pH value is less than 2, and continuously stirring for 1-10 hours, preferably 2-9 hours, more preferably 3-8 hours;
3) filtering, washing and drying the mixed solution, wherein the drying temperature is 80-150 ℃, preferably 90-140 ℃, more preferably 100-130 ℃; the drying time is 2-12 hours, preferably 3-10 hours, more preferably 4-8 hours;
4) the dried solid is calcined at 300-700 deg.C, preferably 350-650 deg.C, more preferably 400-600 deg.C under the protection of inert gas (such as nitrogen) for 0.5-8 hours, preferably 1-7 hours, more preferably 2-6 hours.
4. Preparation of hydrodehalogenation catalyst
The hydrodehalogenation catalyst of the present invention may be formed by placing the procatalyst and the cocatalyst (i.e., the catalyst active component) on the support using methods known in the art. The method for supporting the catalyst active component on the catalyst support is not particularly limited, and may be a conventional method known in the art, for example, a method of supporting the catalyst component on a support which has been formed, using an excess impregnation method and an equivalent-volume impregnation method, using a one-step impregnation and a multi-step impregnation, etc., and then drying, calcining and reducing the support on which the main catalyst and the co-catalyst are supported to obtain the desired catalyst.
In the present invention, the drying, calcination and reduction are all conventional methods for preparing a catalyst. In one embodiment of the present invention, the drying temperature is 100-150 ℃, preferably 110-; the roasting temperature is 300-500 ℃, preferably 320-480 ℃, more preferably 340-450 ℃; the reduction temperature is 100-450 ℃, preferably 150-400 ℃. More preferably 200 ℃ to 350 ℃.
In one embodiment of the present invention, the drying atmosphere at the time of drying is an inert atmosphere, and preferably nitrogen gas from the viewpoint of cost.
In one embodiment of the present invention, the reducing atmosphere is hydrogen or hydrogen diluted gas, the concentration of hydrogen is in the range of 0.25 to 100%, and the balance is nitrogen.
In one embodiment of the present invention, the impregnation solution (containing the procatalyst and the cocatalyst component) is prepared by using soluble salts of the procatalyst and the cocatalyst component, for example, palladium and ruthenium may be prepared by using palladium nitrate, palladium chloride and ruthenium chloride, ruthenium acetate, and for other cocatalyst component, soluble metal salts thereof may be prepared by using nitrate, chloride, oxychloride, acetate, lactate, etc.
In one embodiment of the present invention, the method for preparing the catalyst of the present invention comprises the steps of:
a) preparing an aqueous solution of metal halide salt, providing an activated carbon substrate subjected to oxidation treatment, spraying and impregnating the activated carbon substrate with a metal halide salt solution for multiple times by using a coating machine, so that the amount of the impregnated metal halide salt accounts for 0.3-3%, preferably 0.5-2.5%, more preferably 0.8-2% of the total weight, drying the impregnated metal halide salt at 95-150 ℃, preferably 100-;
b) forming an acidic aqueous solution of soluble palladium salt, dipping the acidic aqueous solution into the activated carbon-metal halide compound carrier, standing at room temperature, drying, further dipping the acidic aqueous solution of the cocatalyst by the same method, and roasting the dried catalyst precursor for 2-4 hours, preferably 2.5-3.5 hours under nitrogen at 350-.
In one embodiment of the invention, the catalyst of the invention is dried and reduced prior to use. The drying and reduction can be carried out using conventional methods: for example, the drying atmosphere is nitrogen, the reducing atmosphere is hydrogen or hydrogen diluent gas, the concentration range of the hydrogen is 0.25-100%, and the rest is nitrogen; the drying temperature is 100-300 ℃, preferably 120-220 ℃. The reduction temperature is 100-450 ℃, preferably 200-350 ℃.
In the hydrodehalogenation catalyst, the amount of the palladium element serving as a main catalyst accounts for 0.01-1%, preferably 0.02-0.9%, more preferably 0.03-0.8%, preferably 0.04-0.7%, and preferably 0.05-0.6% by weight; the amount of the cocatalyst is 0-5%, preferably 0.3-4.8%, more preferably 0.8-4.2%, preferably 1.2-3.8%, and most preferably 2-3.5%.
B. Hydrodehalogenation reaction
The hydrogenation dehalogenation catalyst is particularly suitable for the hydrogenation dechlorination reaction of 1,1, 2-trifluorotrichloroethane to obtain chlorotrifluoroethylene and trifluoroethylene. The catalyst of the invention can ensure that 1,1, 2-trifluorotrichloroethane is subjected to hydrogenation dechlorination reaction to obtain higher selectivity of chlorotrifluoroethylene and trifluoroethylene, avoid undesirable impurities of fluorine-containing olefin, ensure mild reaction conditions, effectively improve the stability of the reaction and prolong the service life of the catalyst.
In one embodiment of the present invention, the hydrodechlorination of 1,1, 2-trifluorotrichloroethane comprises reacting at a temperature of 100-300 ℃, preferably 130-200 ℃, under the action of the catalyst of the present invention; the molar ratio of the hydrogen to the 1,1, 2-trifluorotrichloroethane is 0.5-10, preferably 0.7-5, more preferably 1-3; the mass liquid hourly space velocity of the 1,1, 2-trifluorotrichloroethane is 0.1-10 h-1Preferably 0.5 to 7 hours-1More preferably 1 to 4 hours-1(ii) a The hydrogen pressure is 0.1-1 MPaG, preferably 0.1-0.8 MPaG, more preferably 0.1-0.5 MPaG, and the high selectivity of the fluorine-containing olefin (chlorotrifluoroethylene and trifluoroethylene) is obtained by continuous catalytic hydrogenation, so that the undesirable impurities of the fluorine-containing olefin are avoided.
In one embodiment of the invention, the 1,1, 2-trifluorotrichloroethane hydrodechlorination reaction adopts a fixed bed continuous reaction process, the fixed bed reactor can be an isothermal bed or an adiabatic bed, and the catalyst is filled in the fixed bed reactor with or without dilution. In the hydrogenation reaction, inert gas such as nitrogen can be introduced or not introduced during feeding as diluent gas, and the molar ratio of nitrogen to hydrogen in the diluent gas formed during introducing the diluent gas is 0.5-5: 1, preferably 0.8-4.5: 1, more preferably 1 to 4: 1, preferably 1.5 to 3.5: 1. in addition, the hydrogenation raw material 1,1, 2-trifluorotrichloroethane used in the invention can be sourced from industrial production devices.
The present invention is further illustrated by the following examples.
Example 1
Preparing a catalyst:
weighing a certain amount of ferric fluoride, adding into 70 ℃ water to prepare a solution, spraying and soaking the ferric fluoride solution on 10g of porous coal carbon (cylindrical activated carbon, phi 2mm, purchased from national chemical reagent Co., Ltd.) treated by nitric acid for multiple times by using a coating machine according to the mass content of the ferric fluoride in the carrier of 1%, drying at 120 ℃ for 4 hours, treating the dried sample at 350 ℃ for 4 hours in a nitrogen atmosphere to obtain an activated carbon-ferric fluoride compound carrier, and testing the specific surface area of the carrier to be 960m by adopting nitrogen adsorption desorption2Per g, average poreThe diameter is 3.5 nm.
0.083g of palladium chloride was added to 10mL of deionized water, hydrochloric acid was added dropwise to form an acidic solution of palladium chloride (pH 2), and the carrier was immersed in the palladium chloride solution in an equal volume, allowed to stand at room temperature for 12 hours, and then dried at 130 ℃ for 5 hours. And further impregnating ruthenium trichloride, copper chloride and zinc nitrate by adopting the impregnation step of the palladium chloride. In the finally formed catalyst, the mass content of palladium is-0.4%, the mass content of ruthenium is-0.05%, the mass content of copper is-3%, and the mass content of zinc is-0.3%. The impregnated catalyst was calcined at 450 ℃ under nitrogen for 3 hours and designated as S1.
Example 2
Preparing a catalyst:
0.58g of calcium nitrate (4 crystal waters) and 0.13g of chromium nitrate (9 crystal waters) are weighed and dissolved in 50mL of deionized water to prepare a mixed solution 1; 0.77g of potassium hydroxide and 0.38g of potassium fluoride are weighed and dissolved in 50mL of deionized water to prepare a mixed solution 2; 10g of Carbon aerogel (synthetic reference Pekala, R.W.and C.T.Alviso (1992). "Carbon Aerogels and Xelogels." MRS one Proceedings Library 270(1):3-14.) was dispersed in 50mL of deionized water with continuous stirring, while dropwise adding solution 1 and solution 2, and stirring was continued for 2 hours after completion of the dropwise addition. Then adjusting the pH value to 2 by hydrofluoric acid, heating to 80 ℃, and continuing stirring for 2 hours. Then the mixture is filtered and washed, and is dried for 4 hours at 120 ℃, and the dried solid sample is treated for 4 hours at 300 ℃ under the nitrogen atmosphere, so as to obtain the composite carrier of calcium fluoride, chromium fluoride and carbon aerogel. The mass contents of calcium fluoride and chromium fluoride in the elemental analysis are respectively 0.8 percent and 0.2 percent, and the specific surface area of the carrier in the nitrogen adsorption and desorption test is 580m2In g, the mean pore diameter is 12 nm.
0.1g of palladium chloride was weighed, 10mL of deionized water was added, hydrochloric acid was added dropwise to an acidic solution (pH 2) of palladium chloride, the carrier was immersed in a solution of palladium chloride in an equal volume, and the solution was allowed to stand at room temperature for 10 hours, followed by drying at 140 ℃ for 3 hours. And continuing to adopt the impregnation step of the palladium chloride to further impregnate the copper chloride and the cesium nitrate. In the finally formed catalyst, the mass content of palladium is-0.5%, the mass content of copper is-3% and the mass content of cesium is-0.1%, and the catalyst is calcined at 380 ℃ for 3 hours under nitrogen and is named as S2.
Example 3
Preparing a catalyst:
0.7g of aluminum isopropoxide is weighed, 15mL of CTAB aqueous solution of 0.02M/L is added, 10g of mesoporous carbon molecular sieve (synthetic reference J.Am.chem.Soc.2000,122,10712-10713.) is dispersed in 20mL of deionized water, the CTAB solution of aluminum isopropoxide is added dropwise under stirring, and after 2 hours of continuous stirring, aqueous solution of hydrofluoric acid (until pH is adjusted to be equal to<1) And after stirring for 2 hours, filtering, drying at 120 ℃ for 4 hours, and treating the dried sample at 350 ℃ for 4 hours in a nitrogen atmosphere to finally form the compound of aluminum fluoride and activated carbon. The mass content of the aluminum fluoride in the elemental analysis is 2.5 percent, and the specific surface area of the nitrogen adsorption and desorption test is 850m2G, average pore diameter 6.5 nm.
0.13g of palladium chloride was added to 10mL of deionized water, hydrochloric acid was added dropwise to form an acidic solution of palladium chloride (pH 2), and the carrier was immersed in the solution of palladium chloride in an equal volume, allowed to stand at room temperature for 12 hours, and then dried at 110 ℃ for 5 hours. And (3) continuing to adopt the impregnation step of the palladium chloride to further impregnate the ruthenium trichloride, the nickel nitrate and the lanthanum nitrate. The mass content of palladium, ruthenium, nickel and lanthanum in the finally formed catalyst is-0.7%, 0.1%, 2% and 0.1%. The catalyst obtained above was calcined at 420 ℃ under nitrogen for 4 hours and named S3.
Example 4
And (3) reaction evaluation:
a fixed bed reactor was charged with 10mL of catalyst S1 (example 1), and 100mL/min of nitrogen was introduced, heated to 120 ℃ and dried for 12 hours, and then cooled to room temperature. Introducing 5mL/min of hydrogen, programming to 380 ℃ and keeping for 4 hours, then switching to 100mL/min of hydrogen to replace nitrogen in the reactor with hydrogen, then reducing to the reaction temperature, and observing the hydrogenation reaction performance of the 1,1, 2-trifluorotrichloroethane. The operating reaction conditions are that the pressure is 0.2MPaG, the temperature is 180 ℃, and the mass liquid hourly space velocity of 1,1, 2-trichlorotrifluoroethane is 2.0h-1The molar ratio of hydrogen to 1,1, 2-trifluorotrichloroethane was 3. The reaction results were as follows: the conversion rate of 1,1, 2-trifluorotrichloroethane is 65.2 percent, the selectivity of chlorotrifluoroethylene is 75.1 percent, the selectivity of trifluoroethylene is 23.1 percent, the selectivity of trifluorodichloroethane (including 1,1, 2-trifluoro-2, 2-dichloroethane and 1,1, 2-trifluoro-1, 2-dichloroethane, bp of the two is 18-29 ℃) is 1.2 percent, and the others are 0.6 percent.
Example 5
And (3) reaction evaluation:
a fixed bed reactor was charged with 10mL of catalyst S2 (example 2), and 100mL/min of nitrogen was passed through the reactor, and the reactor was heated to 120 ℃ to dry for 12 hours and then cooled to room temperature. Introducing 5mL/min of hydrogen, programming to 300 ℃, keeping the temperature for 4 hours, then switching to 100mL/min of hydrogen to replace nitrogen in the reactor with hydrogen, then reducing the reaction temperature, and observing the hydrogenation reaction performance of the 1,1, 2-trifluorotrichloroethane. The reaction conditions were the same as in example 4, and the reaction results were as follows: the conversion rate of 1,1, 2-trifluorotrichloroethane is-90%, the selectivity of chlorotrifluoroethylene is-86.0%, the selectivity of trifluoroethylene is-12.3%, the selectivity of trifluorodichloroethane is-1.2%, and the others are-0.5%.
Example 6
And (3) reaction evaluation:
a fixed bed reactor was charged with 15mL of catalyst S3 (example 3), and 100mL/min of nitrogen was passed through the reactor, and the reactor was heated to 120 ℃ to dry for 12 hours and then cooled to room temperature. Introducing 5mL/min of hydrogen, programming to 450 ℃, keeping the temperature for 4 hours, then switching to 100mL/min of hydrogen to replace nitrogen in the reactor with hydrogen, then reducing the reaction temperature, and observing the hydrogenation reaction performance of the 1,1, 2-trifluorotrichloroethane. The reaction conditions were the same as in example 4, and the reaction results were as follows: the conversion rate of 1,1, 2-trifluorotrichloroethane is-99%, the selectivity of chlorotrifluoroethylene is-70.0%, the selectivity of trifluoroethylene is-28.5%, the selectivity of trifluorodichloroethane is 1.1%, and the others are-0.4%.
Example 7
The fixed bed reactor was loaded with 10ml of catalyst S1 (example 1), and the drying, reduction and reaction procedures of example 4 were followed to examine the effects of the hydrogenation temperature of 1,1, 2-trifluorotrichloroethane, the mass liquid hourly space velocity of 1,1, 2-trifluorotrichloroethane and the molar ratio of hydrogen to 1,1, 2-trifluorotrichloroethane (abbreviated as hydrogen/alkane ratio), as shown in table 1 below:
TABLE 1 results of investigating hydrogenation reaction performance of catalysts
Temperature of
Liquid hourly space velocity
Hydrogen to alkyl ratio
Conversion rate
Chlorotrifluoroethylene selectivity
Selectivity to trifluoroethylene
190℃
2h-1
3
75.8％
78.3％
20.1％
200℃
2h-1
3
88.2％
77.3％
21.4％
200℃
3h-1
1.5
70.5％
85.1％
14.2％
220℃
2h-1
3
98.2％
76.1％
22.5％
220℃
2h-1
1.8
98.1％
80.2％
18.3％
230℃
1h-1
4
99.9％
68.5％
30.2％
240℃
1h-1
5
99.9％
60.0％
38.0％
Example 8
A fixed bed reactor was charged with 20mL of catalyst S1 (example 1), and after introducing 200mL/min of nitrogen, the reactor was heated to 120 ℃ and dried for 12 hours, and then cooled to room temperature. Introducing 5mL/min of hydrogen, programming to 380 ℃ and keeping for 4 hours, then switching to 200mL/min of hydrogen to replace nitrogen in the reactor with hydrogen, then reducing to the reaction temperature, and observing the hydrogenation reaction stability of the 1,1, 2-trifluorotrichloroethane. The operation reaction conditions are that the pressure is 0.2MPaG, the temperature is 170 ℃, and the mass liquid hourly space velocity of 1,1, 2-trichlorotrifluoroethane is 1.0h-1The molar ratio of hydrogen to 1,1, 2-trifluorotrichloroethane was 1.5. The reaction results are shown in table 2 below.
Comparative example 1
Preparing a catalyst:
control example 1, the support was prepared without iron fluoride, but the support was subsequently impregnated with iron fluoride.
10g of coal carbon (cylindrical activated carbon, 2mm in diameter, available from national chemical agents Co., Ltd.) treated with nitric acid was dried at 120 ℃ for 4 hours, the dried sample was further treated at 350 ℃ for 4 hours in a nitrogen atmosphere, and the specific surface area of the test carrier was 982m by desorption of nitrogen2In terms of/g, the mean pore diameter is 3.6 nm.
0.083g of palladium chloride was added to 10mL of deionized water, hydrochloric acid was added dropwise to form an acidic solution of palladium chloride (pH 2), and the carrier was immersed in the palladium chloride solution in an equal volume, allowed to stand at room temperature for 12 hours, and then dried at 130 ℃ for 5 hours. And further impregnating ruthenium trichloride, copper chloride and zinc nitrate by adopting the impregnation step of the palladium chloride.
Weighing a certain amount of ferric fluoride, adding the ferric fluoride into 70 ℃ water to prepare a solution, and spraying and dipping the ferric fluoride solution for multiple times by a coating machine according to the mass content of the ferric fluoride in the carrier as 1% to finally form the catalyst, wherein the mass content of palladium is-0.4%, the mass content of ruthenium is-0.05%, the mass content of copper is-3%, the mass content of zinc is-0.3%, and the mass content of iron is-1%. The catalyst was calcined at 450 ℃ under nitrogen for 3 hours and named D1.
And (3) reaction evaluation: the same procedure as in example 8 was employed.
Comparative example 2
Preparing a catalyst:
comparative example 3, a carrier was prepared without fluoride containing calcium and chromium.
Weighing 0.75g of potassium hydroxide and 0.4g of potassium fluoride, dissolving in 50mL of deionized water, and preparing into a mixed solution; 10g of Carbon aerogel (synthetic reference Pekala, R.W.and C.T.Alviso (1992). "Carbon Aerogels and Xelogels." MRS one Proceedings Library 270(1):3-14.) was dispersed in 50mL of deionized water with continuous stirring, and the above-mentioned mixed solution of potassium hydroxide and potassium fluoride was added dropwise thereto, and stirring was continued for 2 hours after completion of the addition. Then adjusting the pH value to 2 by hydrofluoric acid, heating to 80 ℃, and continuing stirring for 2 hours. The mixture was then filtered and washed and dried at 120 ℃ for 4 hours, and the dried solid sample was further treated at 300 ℃ for 4 hours under a nitrogen atmosphere to give the desired carrier. The specific surface area of the carrier is 620m in the nitrogen adsorption and desorption test2(ii)/g, average pore diameter 13 nm.
0.1g of palladium chloride was weighed, 10mL of deionized water was added, hydrochloric acid was added dropwise to an acidic solution (pH 2) of palladium chloride, the carrier was immersed in a solution of palladium chloride in an equal volume, and the solution was allowed to stand at room temperature for 10 hours, followed by drying at 140 ℃ for 3 hours. And continuing to adopt the impregnation step of the palladium chloride to further impregnate the copper chloride and the cesium nitrate. In the finally formed catalyst, the mass content of palladium is-0.55%, the mass content of copper is-2.8%, and the mass content of cesium is-0.07%. The catalyst was calcined at 380 ℃ under nitrogen for 3 hours and named D2.
And (3) reaction evaluation: the same procedure as in example 8 was employed.
Table 2 stability test results of the catalysts
Catalyst and process for preparing same
Reaction time
Average conversion
Chlorotrifluoroethylene selectivity
Selectivity to trifluoroethylene
S1
100h
78.2％
80.1％
18.5％
300h
77.9％
80.3％
18.3％
500h
78.1％
79.7％
17.9％
1000h
78.3％
80.2％
18.1％
1500h
78.3％
80.1％
18.1％
D1
100h
82.3％
60.5％
15.3％
300h
56.3％
47.9％
20.1％
500h
20.5％
45.0％
23.2％
S2
100h
95.1％
91.2％
8.0％
300h
95.2％
91.2％
7.9％
500h
95.4％
91.3％
7.9％
D2
100h
98.1％
90.2％
5.2％
300h
90.3％
88.7％
5.3％
500h
85.2％
86.3％
4.2％
From the above implementation effects, it can be seen that, by the hydrodechlorination of trifluorotrichloroethane, the method and the catalyst for simultaneously preparing fluorine-containing olefins (chlorotrifluoroethylene and trifluoroethylene) provided by the invention can obtain different fluorine-containing olefin selectivities by adjusting reaction parameters, and the total selection of the chlorotrifluoroethylene and the trifluoroethylene can be still maintained above 95%, and the contents of other byproducts are low, so that the subsequent separation is easy. Meanwhile, as can be seen from the comparison effect of the catalyst, the catalyst of the invention can show higher selectivity of the fluorine-containing olefin and longer reaction life compared with the method of directly taking porous carbon as a carrier to load an active component and a cocatalyst and taking a composite of the porous carbon and metal fluoride as the carrier.