A method for preparing cis-hexafluoro-2-butene

Abstract

The present invention discloses a method for preparing cis-hexafluoro-2-butene. The disclosed solution uses trifluoropropyne and trifluoroiodomethane as raw materials, and prepares cis-hexafluoro-2-butene through two steps of gas-phase coupling and gas-phase hydrogenation. The present invention has the characteristics of few by-products and few three wastes.

Description

Technical Field

[0001] The present invention belongs to the field of fluorinated foaming materials and relates to a method for preparing cis - hexafluoro - 2 - butene. Background Art

[0002] The destruction of the ozone layer and global warming have become two major focus issues of concern to the international community. To protect the atmospheric ozone layer, the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987, an international convention aimed at phasing out ozone - depleting substances (ODS), and decided to replace chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) that damage the atmospheric ozone layer with hydrofluorocarbons (HFCs).

[0003] However, HFCs have an extremely high global warming potential (GWP), which can reach 15,000 times that of an equal amount of carbon dioxide (CO2). They have become the most concerned greenhouse gases in the Kyoto Protocol and are one of the main substances causing global warming in the future. According to the statistical data of the Intergovernmental Panel on Climate Change (IPCC), if no emission reduction measures are taken, by 2050, the annual emissions of HFCs will reach 5.5 - 8.8 billion tons of carbon dioxide equivalent, accounting for 28 - 45% of the total greenhouse gas emissions.

[0004] Facing the potential risks of HFCs to global warming, the international community has decided to gradually phase out HFCs. In December 2015, the international community reached the Paris Agreement and reached a consensus on accelerating the phase - out process of HFCs. In October 2016, the international community adopted the Kigali Amendment to the Montreal Protocol, which formulated an emission reduction schedule for HFCs, stipulating that developed countries will phase out HFCs starting from 2019, and developing countries will start phasing out HFCs in 2024.

[0005] Blowing agents are one of the main application fields of HFCs. HCFC - 141b and HFC - 245fa are currently commonly used blowing agents.

[0006] The ODP of HCFC - 141b is 0.2 and the GWP is 725. Due to its ozone - depleting effect, it has been banned in developed countries such as Europe and the United States, and China has completely banned it since January 1, 2020.

[0007] The ODP of HFC - 245fa is 0. Developed countries use it as a substitute for HCFC - 141b. Since its GWP is 1020, developed countries have entered the phase - out stage.

[0008] Cis-hexafluoro-2-butene (Z-HFO-1336mzz, the structural formula is shown in Ⅰ) has a boiling range similar to that of HCFC-141b and HFC-245fa, and its properties such as heat insulation and compatibility with foaming materials are also very close. It can replace HCFC-141b and HFC-245fa in the general foaming material products industry without upgrading the foaming equipment, and its ODP is 0 and GWP is only 9. It is the most direct and economical solution to replace HCFC-141b and HFC-245fa and has been approved by the U.S. Environmental Protection Agency's Significant New Alternatives Policy (SNAP). In August 2016, in the "Recommended List of Key Alternatives to Hydrochlorofluorocarbons (HCFCs)" released by the Foreign Economic Cooperation Center (FECO) of China's Ministry of Environmental Protection, Z-HFO-1336mzz was listed as a recommended alternative to HCFC-141b and HFC-245fa blowing agents.

[0009]

[0010] DuPont applied for patent CN106536462A in 2015 to prepare HFO-1336mzz by reacting HCFC-113a with hydrogen. The selectivity of the products of this route is low, and a large amount of greenhouse gas HFCs is produced as a by-product.

[0011] Honeywell prepared HFO-1336mzz from carbon tetrachloride and 3,3,3-trifluoropropene in 2009. The main product of this route is trans-hexafluoro-2-butene. Since it is difficult to prepare cis-hexafluoro-2-butene from trans-hexafluoro-2-butene through isomerization reaction, the economy of this route is greatly reduced.

[0012] In 2013, Juhua Group, Yujitech, and Dechemos, Inc. Florida, etc. focused on process development using hexachlorobutadiene (HCBD) as a raw material and applied for multiple related patents. This route has problems such as limited raw material output, difficult fluorination reaction, and easy deactivation of the catalyst, and its industrial prospect is not good.

[0013] So far, the preparation of cis-hexafluoro-2-butene mainly relies on the hydrogenation of hexafluorobutyne, and the preparation of hexafluorobutyne often requires a saponification reaction (as shown in the following reaction route). Due to the existence of many side reactions in the saponification reaction, the economy of this route is poor.

[0014] SUMMARY OF THE INVENTION

[0015] Aiming at the defects or deficiencies of the prior art, the present invention provides a method for preparing cis-hexafluoro-2-butene.

[0016] Therefore, the preparation method provided by the present invention includes:

[0017] (a) In the presence of a gas-phase coupling catalyst at a reaction temperature of 50 - 150 °C, hexafluorobutyne is prepared by the reaction of trifluoropropyne and trifluoroiodomethane; the preparation method of the gas-phase coupling catalyst is as follows: an aluminum-magnesium composite oxide is impregnated in an aqueous solution of a K or Cs element precursor, dried after impregnation and then calcined at 700 - 900 °C, and then the calcined product is treated with hydrogen fluoride gas or a mixed gas of hydrogen fluoride and an inert gas; the precursor of the K or Cs element is selected from one or more of nitrates, carbonates, acetates, and oxides of K or Cs elements;

[0018] (b) In the presence of a gas-phase hydrogenation catalyst at a reaction temperature of 50 - 150 °C, hexafluorobutyne undergoes a hydrogenation reaction to prepare cis-hexafluoro-2-butene; the active components of the gas-phase hydrogenation catalyst are one or two of nickel, palladium, and copper, and the carrier is activated carbon or magnesium fluoride.

[0019] Optionally, the molar ratio of trifluoropropyne to trifluoroiodomethane is 1:1 - 1:5.

[0020] Optionally, the molar ratio of hexafluorobutyne to hydrogen is 1:1 - 1:3.

[0021] Optionally, the aluminum-magnesium composite oxide is synthesized by reacting an aluminum source, a magnesium source, and polyethylene glycol; the aluminum source is aluminum hydroxide, pseudo-boehmite, hydrated alumina, or aluminum isopropoxide; the magnesium source is magnesium oxide, magnesium nitrate, magnesium acetate, or metallic magnesium.

[0022] Optionally, the reaction in step (a) is carried out in a fixed-bed reactor.

[0023] Optionally, the residence time of the reaction in step (a) is 1 - 10 s.

[0024] Optionally, the contact time of the reaction in step (b) is 3 - 8 s.

[0025] The present invention adopts a reaction route different from the traditional process, avoiding the problems of many by-products and a large amount of three wastes existing in the saponification reaction; both two-step reactions are carried out in the gas phase, and the degree of process continuity is high. Description of the Drawings

[0026] Figure 1 It is the GC spectrum of the hexafluorobutyne prepared in the embodiment of the present invention.

[0027] Figure 2 It is the MS spectrum of the hexafluorobutyne prepared in the embodiment of the present invention.

[0028] Figure 3 It is the 1 H NMR spectrum of Z-HFO-1336mzz prepared in the embodiment of the present invention.

[0029] Figure 4 13C NMR spectrum of Z-HFO-1336mzz prepared in the embodiment of the present invention 13 13C NMR spectrum

[0030] Figure 5 19F NMR spectrum of Z-HFO-1336mzz prepared in the embodiment of the present invention 19 19F NMR spectrum Detailed implementation mode

[0031] Unless otherwise specified, scientific and technical terms and methods in this article are understood or implemented according to the understanding of those of ordinary skill in the relevant field or using existing relevant methods. It should also be understood that the temperatures and concentrations involved in this article are approximate values for illustrative purposes. Although methods and materials similar or equivalent to those described in this article can be used in the implementation of this disclosure, some suitable methods and materials are described below. Publications, patent applications, patents and other references mentioned in this article are incorporated herein by reference in part. In case of conflict, this article shall prevail. In addition, the materials, methods, solution concentrations and examples described above are merely illustrative and are not intended to be limiting. In specific embodiments, those skilled in the art can optimize the material ratios, concentrations, operating parameter values, and reactant addition sequences involved in the methods by using conventional experimental periods according to the content disclosed in the present invention to achieve the purpose of the present invention.

[0032] The present invention relates to a method for preparing cis-hexafluoro-2-butene, and the chemical formula of cis-hexafluoro-2-butene is shown as (I).

[0033]

[0034] The present invention uses trifluoropropyne and trifluoroiodomethane as raw materials, and prepares cis-hexafluoro-2-butene through two-step reactions of gas-phase coupling and gas-phase hydrogenation. The reaction equation is as follows:

[0035]

[0036] The preparation method of the gas-phase coupling catalyst of the present invention includes: impregnating the aluminum-magnesium composite oxide in an aqueous solution of a K or Cs element precursor, drying after impregnation and then calcining at 700-900 °C, and then treating the calcined product with hydrogen fluoride gas or a mixed gas of hydrogen fluoride and an inert gas; the K or Cs element precursor is selected from one or more of nitrates, carbonates, acetates and oxides of K or Cs elements.

[0037] The aluminum-magnesium composite oxide therein can be prepared by existing methods. For example, using an aluminum source and a magnesium source as raw materials and adding polyethylene glycol as a templating agent for synthesis. The aluminum source is aluminum hydroxide, pseudo-boehmite, hydrated alumina or aluminum isopropoxide; the magnesium source is magnesium oxide, magnesium nitrate, magnesium acetate or metallic magnesium. Specific example: After completely dissolving 120 g of pseudo-boehmite and 142 g of magnesium acetate in deionized water, slowly drop into an aqueous solution of polyethylene glycol (a small amount of nitric acid can be added when the dissolution is incomplete). After complete dissolution, let the solution stand for 48 hours. After evaporating a large amount of water in a steam bath, the residual solid is calcined in a muffle furnace at 500 °C for 14 hours to obtain the aluminum-magnesium composite oxide.

[0038] Specific preparation example of the catalyst of the present invention (the catalyst used in Example 1): After dissolving 5 g of cesium nitrate, add 100 g of the prepared aluminum-magnesium composite oxide above. After impregnation for 48 hours, dry the solution, and then calcine it in a muffle furnace at 800 °C for 24 hours to prepare the used catalyst. The BET of the prepared catalyst is 317 m 2 / g. Place the catalyst in a rotary furnace and continuously pass a mixed gas of HF and N2 through it to treat the catalyst, and then the aluminum-magnesium composite fluoride loaded with Cs ions, 5Cs / Al x Mg y F z (It means made from 5 g of Cs nitrate and 100 g of aluminum-magnesium composite oxide. The following examples are similar, that is, the corresponding mass number of elemental nitrate and 100 g of aluminum-magnesium composite oxide are made). AlxMgyF in the following examples Z refers to the aluminum-magnesium composite fluoride. According to the disclosure of the present invention, those skilled in the art can obtain other catalysts suitable for the present invention through conventional experimental methods.

[0039] The following further details the present invention in conjunction with examples, but does not limit the scope of the present invention.

[0040] Example 1:

[0041] (a) Measure 50 mL of the catalyst 5Cs / Al x Mg y F z Transfer it into a fixed-bed tubular reactor, heat it to 100 °C and dry for 2 h, then introduce trifluoroiodomethane, and then introduce trifluoropropyne. The molar ratio of trifluoropropyne to trifluoroiodomethane is 1:3, and the residence time is 1 s. After the product is absorbed by ice water, it is subjected to GC-MS analysis, and the results are as Figure 1 and 2 shown.

[0042] Mass spectrometry results (m / z): 162 (M), 143 (M - F), 143 (M - CF3), 69 (-CF3). From the analysis of the fragmentation results, it is speculated that the product is hexafluorobutyne (CF3C≡CCF3); and the yield of hexafluorobutyne analyzed by chromatography is 71%;

[0043] (b) Measure 10 mL of catalyst 3Pd / 7Cu / 90C (the mass ratio of each component of Pd, Cu, and C is 3:7:90, and the representation of the corresponding catalyst in the following examples is similar), transfer it into a fixed - bed tubular reactor, heat it to 50 °C and introduce hydrogen, then introduce the hexafluorobutyne prepared in step (a). The molar ratio of hydrogen to hexafluorobutyne is 2:1, the contact time is 3 s, and after reacting for 6 hours, analyze the gas - phase composition by chromatography; at the same time, conduct nuclear magnetic resonance analysis on the product.

[0044] See Figures 3 - 5 As shown, the nuclear magnetic data of the obtained product are as follows: 1 1H NMR (500 MHz, CDCl3) δ6.12 (m, 2H). 13 13C NMR 127.9 (m), 120.3 (q, J = 270.5 Hz). 19 19F NMR (470.0 MHz, CDCl3) δ - 60.7 (s, CF3), indicating that it is cis - 1,1,1,4,4,4 - hexafluoro - 2 - butene;

[0045] Chromatographic analysis result: The yield of cis - hexafluoro - 2 - butene is 82%.

[0046] Examples 2 - 8:

[0047] Synthesize hexafluorobutyne using the same method as in (a) of Example 1, except that the catalyst - loaded elements, reaction temperature, molar ratio of propargyl trifluoride to trifluoromethyliodide, and residence time are changed. The reaction results are shown in Table 1.

[0048] Table 1

[0049]

[0050] Examples 9 - 15:

[0051] Synthesize cis - hexafluoro - 2 - butene using the same method as in (b) of Example 1, except that the catalyst, reaction temperature, molar ratio of hexafluorobutyne to hydrogen, and residence time are changed. The reaction results are shown in Table 2.

[0052] Table 2

[0053]

[0054]

Claims

1. A method for preparing cis - hexafluoro - 2 - butene, characterized in that the method Comprising: (a) At a reaction temperature of 50 - 150 °C and in the presence of a gas-phase coupling catalyst, hexafluorobutyne is prepared by reacting trifluoropropyne and trifluoroiodomethane; the preparation method of the gas-phase coupling catalyst is as follows: an aluminum-magnesium composite oxide is impregnated in an aqueous solution of a K or Cs element precursor, dried after impregnation, then calcined at 700 - 900 °C, and then the calcined product is treated with hydrogen fluoride gas or a mixed gas of hydrogen fluoride and an inert gas; the precursor of the K or Cs element is selected from one or more of nitrates, carbonates, acetates, and oxides of K or Cs elements; (b) At a reaction temperature of 50 - 150 °C and in the presence of a gas-phase hydrogenation catalyst, hexafluorobutyne undergoes a hydrogenation reaction to prepare cis-hexafluoro-2-butene; the active components of the gas-phase hydrogenation catalyst are one or two of nickel, palladium, and copper, and the carrier is activated carbon or magnesium fluoride.

2. The method for preparing cis-hexafluoro-2-butene according to claim 1, wherein The molar ratio of trifluoropropyne to trifluoroiodomethane is 1:1 - 1:

5.

3. The method for preparing cis-hexafluoro-2-butene according to claim 1, characterized in that, The molar ratio of hexafluorobutyne to hydrogen is 1:1 - 1:

3.

4. The method for preparing cis-hexafluoro-2-butene according to claim 1, wherein, The aluminum-magnesium composite oxide is synthesized by reacting an aluminum source, a magnesium source, and polyethylene glycol; the aluminum source is aluminum hydroxide, pseudo-boehmite, hydrated alumina, or aluminum isopropoxide; the magnesium source is magnesium oxide, magnesium nitrate, magnesium acetate, or metallic magnesium.

5. The preparation method of cis-hexafluoro-2-butene according to claim 1, characterized in that, The reaction in step (a) is carried out in a fixed-bed reactor.

6. The preparation method of cis-hexafluoro-2-butene according to claim 1, wherein, The residence time of the reaction in step (a) is 1 - 10 s.

7. The method for preparing cis-hexafluoro-2-butene according to claim 1, characterized in that, The contact time of the reaction in step (b) is 3 - 8 s.

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