Application of a catalyst in the preparation of 1,1-difluoroethane via ethylene oxide

Abstract

The present invention relates to an application of a catalyst in preparing 1,1-difluoroethane via ethylene oxide. Specifically, the preparation of 1,1-difluoroethane uses ethylene oxide as a reactant, and the catalyst is AlF 3 、MoCl 5 and Cr 2 O 3 The molar ratio of the three is (1.5-3):(5-20):(0.05-0.5); compared with the prior art, the present invention reduces production costs, improves reaction activity and greatly improves the yield of 1,1-difluoroethane.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and in particular to application of a catalyst in the preparation of 1,1-difluoroethane. Background Art

[0002] 1,1-Difluoroethane (R152a, HFC-152a, F152a, molecular structure CH3-CHF2) is an important fluorine-containing organic compound, with an ozone depletion potential of OPD = 0 and a global warming coefficient of GWP = 0.03. It is an excellent variety among the two-carbon substitutes for Freon. R152a is generally mixed with other refrigerants to form a mixed refrigerant, which is widely used in refrigeration systems.

[0003] At present, catalysts are generally used to prepare R152a. The types of catalysts include mercury-containing compounds, chromium-containing compounds, cadmium-containing compounds, cuprous cyanide, aluminum-containing compounds, etc. Mercury-containing catalysts are expensive, difficult to prepare, short-lived, and highly toxic; cadmium-containing catalysts and cyanide catalysts are also highly toxic; large-scale use of chromium-containing catalysts causes serious environmental pollution; single-component aluminum-based or zinc-based catalysts have a short catalyst life.

[0004] Prior art Molybdenum (VI) fluoride (By: Mathey, Francois, e-EROS Encyclopedia of reagents for Organic Synthesis, 1-2, 2001) discloses a reaction of generating 1,1-difluoroethane using ethylene oxide as a reactant in the presence of molybdenum hexafluoride. However, molybdenum hexafluoride is very expensive and the yield of 1,1-difluoroethane is only 42%.

[0005] Therefore, improving the yield of 1,1-difluoroethane and reducing the cost are issues that need to be addressed urgently. Summary of the invention

[0006] To solve at least one of the above problems, the present invention provides an application of a catalyst in the preparation of 1,1-difluoroethane via ethylene oxide, wherein the preparation of 1,1-difluoroethane uses ethylene oxide as a reactant, and the catalyst is a mixture of AlF3, MoCl5 and Cr2O3, and the molar ratio of the three is (1.5-3):(5-20):(0.05-0.5).

[0007] Catalysts play an important role in the preparation process of 1,1-difluoroethane. For the reaction of the present invention, selecting a suitable catalyst is conducive to improving the yield. In the present invention, the types of metals constituting the catalyst are optimized. The present application preferably uses metal aluminum, metal molybdenum and metal chromium. Combinations of other metals such as aluminum / tin / neodymium, chromium / cobalt / aluminum, chromium / cobalt / lanthanum, chromium / cobalt / magnesium, chromium / zinc / aluminum, etc., cannot achieve the effect of the catalyst of the present invention in improving the yield of 1,1-difluoroethane.

[0008] Furthermore, the metal constituting the catalyst is preferably present in the form of metal fluorides, chlorides and oxides; the present invention preferably uses AlF3, MoCl5 and Cr2O3 as components of the catalyst.

[0009] Furthermore, the molar ratio of AlF3, MoCl5 and Cr2O3 is also optimized.

[0010] In some embodiments, the molar ratio of AlF3, MoCl5 and Cr2O3 is (1.5-2.5):(8-20):(0.1-0.3).

[0011] In other embodiments, the molar ratio of AlF3, MoCl5 and Cr2O3 is (1.8-2.2):(8-15):(0.1-0.3).

[0012] AlF3 catalyst has a wide range of sources and is green and environmentally friendly. The present invention has no special requirements for the specific surface area of ​​AlF3. The present invention preferably has a specific surface area of ​​150 m 2 ·g -1 -200m 2 ·g -1 Further preferably, the specific surface area of ​​AlF3 of the present invention is 150m 2 ·g -1 -180m 2 ·g -1 The AlF3 of the present invention can be prepared by methods known in the art.

[0013] For example, AlF3 of the present invention can be prepared by the following method:

[0014] The aluminum source is added to the mixed solvent and stirred to obtain a mixed liquid; then the fluorination reagent is added under stirring, and after the addition is completed, stirring is continued to obtain a liquid sol; the liquid sol is subjected to atmospheric distillation and reduced pressure distillation in sequence to obtain a solid gel; the solid gel is dried and calcined to obtain aluminum fluoride.

[0015] The aluminum source is one or more of aluminum oxide, aluminum nitrate or aluminum sulfate; the mixed solvent is water and ethylene glycol; the fluorination agent is hydrogen fluoride or ammonium fluoride; the drying temperature is 90-120°C; the drying time is 8-16h; the calcination temperature is 400°C-550°C; and the calcination time is 4-10h.

[0016] MoCl5 is biocompatible and does not form any toxic byproducts in the reaction system. The present invention has no special requirements for MoCl5. The MoCl5 used in the present invention can be prepared by the method of the prior art or can be commercially obtained.

[0017] Compared with the prior art, the amount of Cr used in the catalyst of the present invention is small, and the environmental pollution is small. The Cr2O3 used in the present invention can be obtained by the method of the prior art, or it can be obtained commercially. In order to further improve the catalytic activity of Cr2O3, the present invention uses Cr2O3 in nano form, and the present invention has no special requirements for the average particle size of nano Cr2O3 particles. Preferably, the average particle size of the nano Cr2O3 particles is ≤50nm; more preferably, the average particle size of the nano Cr2O3 particles is 10-30nm or 10-20nm.

[0018] The method for preparing nano Cr2O3 of the present invention comprises the following steps: dissolving K2CrO4 and glucose in water, adjusting pH value, placing in a microwave reactor for reaction, cooling, centrifuging, washing, separating and drying to obtain nano chromium oxide.

[0019] Wherein, the regulating agent for adjusting the pH value is nitric acid or hydrochloric acid; the magnitude of the adjusted pH value is 3-5; the reaction time in the microwave reactor is 50-120 min; the reaction time in the microwave reactor is 60-100 min, for example: 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min or 100 min, etc.; the power during the reaction in the microwave reactor is 400-700 W, for example: 400 W, 450 W, 500 W, 550 W, 600 W, 650 W or 700 W, etc.

[0020] After effectively compounding AlF3, MoCl5 and Cr2O3, a catalyst with low cost, high activity and low environmental impact is obtained.

[0021] In some embodiments, HF is further included in the reaction.

[0022] In other embodiments, the molar ratio of ethylene oxide to HF is 1:(2-5). Within this material ratio range, there is no waste due to excessive materials, and the reaction can be fully carried out, further improving the yield. Specifically, the molar ratio of ethylene oxide to HF is 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0023] In some embodiments, the molar amount of catalyst is 35% to 75% of the molar amount of HF.

[0024] In other embodiments, the molar amount of the catalyst is 40%-70% of the molar amount of HF. Specifically, the molar amount of the catalyst is 40.8%, 50%, 55.6% or 68.8% of the molar amount of HF.

[0025] The molar dosage of the catalyst described in the present invention is the sum of the molar dosages of AlF3, MoCl5 and Cr2O3.

[0026] In some embodiments, the reaction of the present invention can be carried out in a single solvent or a mixture of different solvents. The suitable solvent can be a polar or non-polar solvent, and is preferably DMF.

[0027] In some embodiments, the reaction temperature of the present invention is preferably 25-250° C., and the reaction pressure is preferably 0.5-3 MPa.

[0028] Preferably, the present invention can be produced by a batch process or a continuous process.

[0029] Compared with the prior art, the present invention has the following advantages: (1) expensive MoF6 is not used, thereby reducing production costs; (2) a catalyst of a specific type and ratio is used to improve reaction activity; and (3) the yield of 1,1-difluoroethane is increased by at least 35%. DETAILED DESCRIPTION

[0030] The present invention can be better understood by the following examples, but the present invention is by no means limited to the following examples. The reagents, solvents, etc. used in the present invention are commercially available, or can be prepared by methods known in the art or methods described in the prior art.

[0031] Preparation of aluminum fluoride

[0032] Alumina (5.10 g, 0.05 mol) was added to a mixed solvent of water (18 mL) and ethylene glycol (40 mL), and the mixture was stirred to obtain a mixed solution; under continued stirring, an aqueous solution of ammonium fluoride (10 mol / L, 60 mL) was added dropwise to the mixed solution for fluorination, and after the addition was completed, stirring was continued for 8 h to obtain a liquid sol; the liquid sol was subjected to atmospheric distillation and reduced pressure distillation in sequence to obtain a solid gel; the solid gel was dried at 110 ° C for 16 h, and finally calcined at 450 ° C for 8 h to obtain aluminum fluoride. The specific surface area of ​​the obtained aluminum fluoride was 160 m 2 / g.

[0033] Preparation of Nano-Chromium Oxide

[0034] K2CrO4 (10.00 g) and glucose (15.00 g) were dissolved in deionized water (100 mL), nitric acid (68%) was added to adjust the pH value of the solution to 4, the mixed solution was transferred to a 250 mL flask, and then the flask was placed in a microwave reactor and reacted at a power of 650 W for 90 min. After the reaction was completed, the reaction was cooled to room temperature, the material was discharged and washed and separated by a centrifuge, and dried to obtain nano chromium oxide. The average particle size of the obtained nano chromium oxide particles was 15.3 nm.

[0035] Example 1

[0036] The equipment used is composed of a 1-liter stirred autoclave made of stainless steel, with a simple condenser and a pressure regulating valve on the top of the autoclave. The autoclave is immersed in an ice bath and first introduced with ethylene oxide (440 g, 10 mol), AlF3 (168 g, 2 mol) and MoCl5 (4100 g, 15 mol), then immersed in an oil bath and heated to 200°C and stirred for 3 hours before introducing DMF (2 L), HF (500 g, 25 mol) and Cr2O3 (20 g, 0.2 mol). The autoclave temperature is then controlled to 240°C, while the condenser temperature is maintained at 15°C. The pressure is set to 1.0 MPa (absolute pressure). At this pressure, the medium temperature is about 155°C on average. During the reaction, the volatile reaction products are continuously discharged and collected in a stainless steel collector cooled with liquid nitrogen, and the product is allowed to enter a 1-liter water-filled washing bottle and then into a dryer. After 20 hours of reaction, the autoclave was cooled by water circulation. After returning to ambient temperature, the autoclave was degassed and the reaction product was washed and dried as described above. The yield of 1,1-difluoroethane was determined to be 77%.

[0037] The same method as in Example 1 was used to change the amounts of AlF3, MoCl5 and Cr2O3 to obtain the results of Examples 2-4 and Comparative Examples 1-3.

[0038] Table 1

[0039] Examples <![CDATA[Dosage of AlF3]]> <![CDATA[Dosage of MoCl5]]> <![CDATA[Amount of Cr2O3]]> Yield of 1,1-difluoroethane Example 2 1.8mol 12mol 0.1mol 80％ Example 3 2.2mol 10mol 0.3mol 80％ Example 4 2mol 8mol 0.2mol 83％ Comparative Example 1 2.2mol 10mol 0mol 35％ Comparative Example 2 2.2mol 0 0.3mol 12％ Comparative Example 3 0 10mol 0.3mol 5％

[0040] It can be seen from the results in Table 1 that the dosage of AlF3, MoCl5 and Cr2O3 has a great influence on the yield of 1,1-difluoroethane. The lack of any one of AlF3, MoCl5 and Cr2O3 is not conducive to the formation of 1,1-difluoroethane.

[0041] In summary, it can be seen from Examples 1-4 and Comparative Examples 1-3 that the catalyst of the present invention has a high yield of 1,1-difluoroethane, which provides a new idea for the preparation of R152a and has a good prospect for industrial application.

[0042] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0043] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0044] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. Use of a catalyst in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The preparation of 1,1-difluoroethane uses ethylene oxide as a reactant, and the catalyst is AlF 3 、MoCl 5 and Cr 2 O 3 A mixture of the three, the molar ratio of which is (1.5-3):(5-20):(0.05-0.5); The AlF 3 The specific surface area is 150m 2 ·g -1 -200m 2 ·g -1 ; The Cr 2 O 3 Nano-Cr 2 O 3 , the average particle size of the particles is ≤50nm; The reaction for preparing 1,1-difluoroethane further comprises HF; The molar ratio of ethylene oxide to HF is 1:(2-5); The preparation of 1,1-difluoroethane comprises: reacting at a temperature of 155 to 240° C. and a pressure of 0.5 to 3 MPa, collecting discharged volatile products, cooling, washing, and drying to obtain the 1,1-difluoroethane.

2. Use of the catalyst according to claim 1 in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The AlF 3 、MoCl 5 and Cr 2 O 3 The molar ratio is (1.5-2.5):(8-20):(0.1-0.3).

3. Use of the catalyst according to claim 2 in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The AlF 3 、MoCl 5 and Cr 2 O 3 The molar ratio is (1.8-2.2):(8-15):(0.1-0.3).

4. Use of the catalyst according to claim 1 in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The molar amount of the catalyst is 35%-75% of the molar amount of HF.

5. Use of the catalyst according to claim 4 in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The molar amount of the catalyst is 40%-70% of the molar amount of HF.

6. Use of the catalyst according to any one of claims 1 to 3 in the preparation of 1,1-difluoroethane via ethylene oxide, It is characterized in that The reaction for preparing 1,1-difluoroethane is carried out in DMF.