WO2016078225A1 - Trans-1,1,1,4,4,4-hexafluoro-2-butene synthesis method - Google Patents

Abstract

Provided is a method for synthesising trans-1,1,1,4,4,4-hexafluoro-2-butene, said method using 1,1,1-trifluoro-2,2-dichloroethane and a chlorinated ethene CH₂=CX₂ as raw materials, and being divided into three steps: (a) the reaction of 1,1,1-trifluoro-2,2-dichloroethane with CH₂=CX₂ in the presence of a telomerisation catalyst and a catalytic additive to synthesise CF₃CHClCH₂CClX₂; (b) the photochlorination of CF₃CHClCH₂CClX₂ to synthesise CF₃CHClCH₂CCl₃; (c) the gas phase fluorination of CF₃CHClCH₂CCl₃ in the presence of a fluorination catalyst to synthesise trans-1,1,1,4,4,4-hexafluoro-2-butene. CH₂=CX₂ is ethene, chloroethene or 1,1-dichloroethene. The present invention has the features of high trans selectivity and inexpensive raw materials.

Description

Method for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene Technical field

The present invention relates to a process for the synthesis of hydrofluoroolefins, and more particularly to a process for the synthesis of trans-1,1,1,4,4,4-hexafluoro-2-butene.

Background technique

Since the first and second generation of blowing agents (monofluorotrichloromethane CFC-11, monofluorodichloroethane HCFC-141b, etc.) destroy the ozone layer, it has been banned from use, and the third generation of blowing agent (1, 1, 1,3,3-pentafluoropropane HFC-245fa, etc.) will produce a strong greenhouse effect. With the increasing impact of global warming on the Earth's ecology, there is an urgent need to find green and environmentally friendly foaming agents.

As a hydrofluoroolefin (HFO) substance, cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336) has zero ozone depletion potential (ODP), greenhouse effect potential The value (GWP) is extremely low and has little impact on the environment. Because its performance is similar to that of previous generations of foaming agents, it is regarded as a new generation of green foaming agent, and the anti-HFO-1336 transformation synthesis cis-HFO-1336 has The route is short, green and pollution-free.

There are existing methods for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene, some of which have higher raw materials and some have lower trans selectivity. For example, WO 2009117458 reports that a chemical amount of copper powder reacts with HCFC-123 to synthesize HFO-1336. The ratio of cis to trans in the product is close to 1:1, which is not only low in selectivity but also highly polluted.

WO 2011119370 reports the catalytic synthesis of trichloropropene and carbon tetrachloride to synthesize tetrachlorotrifluorobutane, catalyzing the fluorination of the synthesis product 1,1,1,4,4,4-hexafluoro-2-butene, using raw materials Trifluoropropene has not been produced on a large scale and is expensive, and the sum of the selectivity of cis-HFO-1336 and trans-HFO-1336 in the product is 93%.

Summary of the invention

In view of the deficiencies or deficiencies of the prior art, it is an object of the present invention to provide a high trans selectivity. A method for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene which is inexpensive and readily available.

In order to solve the above problems, the present invention provides a method for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene, trans-1,1,1,4,4,4 - The structural formula of hexafluoro-2-butene is as shown in formula (I):

Includes the following steps:

(a) a molar ratio of 1,1,1-trifluoro-2,2-dichloroethane to CH ₂ =CX _{2 of} from 1 to 10:1 in the presence of a telomerization catalyst and a catalytic aid in a polar solvent , the reaction temperature is 80-180 ° C, the reaction pressure is 0.8-5.0 MPa, the reaction is 1-48 h, and CF ₃ CHClCH ₂ CClX _{2 is obtained} , wherein X is Cl or H, and the telomerization catalyst is 0, 1 or 2 Copper salt

(b) The molar ratio of chlorine gas to CF ₃ CHClCH ₂ CClX ₂ is 1 to 3:1, and under the illumination, the temperature is -40 to 80 ° C, and the reaction is carried out for 5 to 48 hours to obtain CF ₃ CHClCH ₂ CCl ₃ ;

(c) controlling the molar ratio of HF to CF ₃ CHClCH ₂ CCl ₃ in the presence of a fluorination catalyst from 1:3 to 20, through a tubular fixed-bed reactor, a reaction temperature of 100 to 500 ° C, and a contact time of 0.1 to 10 s, Synthesis of trans-1,1,1,4,4,4-hexafluoro-2-butene.

Step (a): CF ₃ CHCl ₂ + CX ₂ = CH ₂ → CF ₃ CHClCH ₂ CClX ₂

The starting material CH ₂ =CX ₂ is CH ₂ =CH ₂ , CH ₂ =CHCl or CH ₂ =CCl ₂ , CF ₃ CHClCH ₂ CClX ₂ is CF ₃ CHClCH ₂ CH ₂ Cl, CF ₃ CHClCH ₂ CHCl ₂ or CF ₃ CHClCH ₂ CCl ₃ .

The telomerization catalyst uses a zero, one or two valent copper salt, including elemental copper, halogenated copper, cuprous halide, copper salicylate, copper oxalate or copper acetylacetonate, preferably cuprous chloride or copper chloride. .

The catalytic auxiliary agent is an organic amine or a polypyridine compound, and the addition of a catalytic auxiliary agent can improve the solubility of the telomerization catalyst and lower the redox potential, although the reaction can be carried out without adding a catalytic aid, but To achieve higher conversion and selectivity, preferably the catalytic aid 2,2-bipyridine, pentamethyldiethylenetriamine, tris(2-pyridylmethyl)amine or tris(2-dimethylaminoethyl) amine.

The solvent is a polar solvent, including: alcohols, ketones, nitriles, amides, sulfones, the reaction can also be carried out without adding a solvent in the reaction, and the addition of a polar solvent can effectively increase the reaction rate and product selectivity, so it is preferred. The solvent is acetonitrile, methanol, acetone, dimethylformamide or dimethyl sulfoxide.

The reaction conditions are as follows: the catalyst is used in an amount of 0.01% to 50% by moles of 1,1,1-trifluoro-2,2-dichloroethane, preferably 0.5% to 20% by mole, more preferably 1% by mole. ～5%; the molar ratio of the telomer is 1 to 10:1, preferably 2 to 5:1; the reaction temperature is 80 to 180 ° C, preferably the temperature is 100 to 130 ° C; the reaction time is 1 to 48 h, preferably 5 to 24 h; The pressure is 0.8 to 5.0 MPa, preferably the pressure is 1.2 to 2.0 MPa. After the reaction, the product is transferred to a rectification column for purification.

Step (b): CF ₃ CHClCH ₂ CClX ₂ + Cl ₂ → CF ₃ CHClCH ₂ CCl ₃

The reaction can be carried out in both the gas phase and the liquid phase, but in order to achieve better selectivity, the reaction is carried out in a low temperature liquid phase.

The reaction needs to be carried out under ultraviolet light conditions of 250 nm to 400 nm. The light source is a mercury lamp or a halogen lamp. The reactor selects a material having a certain light transmittance to ensure that the light can be transmitted to CF ₃ CHClCH ₂ CClX ₂ and reacted with chlorine gas. For a period of time, CF ₃ CHClCH ₂ CClX _{2 can be} at least partially converted to the product CF ₃ CHClCH ₂ CCl ₃ .

The reaction may be carried out by adding a solvent containing no active H atom to increase the selectivity of the product, and the solvent is preferably carbon tetrachloride, 1,1,2-trichlorotrifluoroethane, chlorobenzene or fluorobenzene.

The reaction conditions are as follows: a molar ratio of chlorine gas to CF ₃ CHClCH ₂ CClX _{2 of} 1 to 3:1, preferably 1.2 to 1.4:1; a reaction temperature of -40 to 80 ° C, -10 to 40 ° C; and a reaction time of 5 to 48 hours, 12 to 36h.

Step (c): CF ₃ CHClCH ₂ CCl ₃ + HF → CF ₃ CH=CHCF ₃

The reaction can obtain the product in the liquid phase and the gas phase, but in order to achieve a better conversion rate, the reaction is selected in the reaction. In the higher temperature gas phase, due to problems such as bio-toxicity, environmental pollution, and low temperature, the Fe-based gas phase fluorination catalyst with less toxicity and less pollution is used in this step. .

The Fe-based vapor phase fluorination catalyst is composed of a compound containing an iron element, a compound containing a rare earth metal element, a compound containing an element A, wherein the rare earth element is La or Ce, and the element A is selected from one of Ca, Al, Mg, and Ti. The ratio of the three elements is 10 to 50% of iron, 48 to 89.5% of A, and 0.5 to 2% of rare earth.

The precursor is subjected to calcination and fluorination treatment to obtain a chromium-free gas phase fluorination catalyst. The various Fe-based gas phase fluorination catalysts of the present invention can be synthesized by a dipping method, a coprecipitation method or a blending method, and the Fe-based gas phase fluorination catalyst precursor after high-temperature calcination is treated with hydrogen fluoride at 400 ° C for gas phase fluorination reaction. .

The type of reactor for the fluorination reaction is preferably a tubular fixed bed reactor made of a material resistant to hydrogen fluoride corrosion such as nickel and its alloys including Hastelloy, Inconel, Incoloy and Monel. During the reaction, the HF gas is continuously passed to the catalytic fixed bed. After a period of time, CF ₃ CHClCH ₂ CCl _{3 is} continuously introduced, and the CF ₃ CHClCH ₂ CCl ₃ /HF molar ratio is controlled to be 1:3 to 20, preferably 1:6 to 10. The reaction temperature of CF ₃ CHClCH ₂ CCl ₃ and HF is 100 to 500 ° C, preferably 300 to 400 ° C, and the reaction contact time is 0.1 to 10 s, preferably 3 to 8 s, to obtain trans-1, 1, 1, 4, 4, 4 - hexafluoro-2-butene.

The advantages of the invention:

(1) The present invention uses a synthetic trans-1,1,1,4,4,4-hexafluoro-2-butene having a trans selectivity of not less than 95%, and the comparative file cis and trans product selectivity is 93. %. (2) The present invention uses 1,1,1-trifluoro-2,2-dichloroethane and vinyl chloride as raw materials, wherein 1,1,1-trifluoro-2,2-dichloroethane is a synthetic refrigeration. HFC-125 has a wide range of raw materials and low cost. Vinyl chloride is also a common raw material for chemical industry, so the cost of raw materials is low. The method reported in the comparative document uses trifluoropropene and carbon tetrachloride as raw materials, of which trifluoropropene has not been mass produced. It is expensive and not easy to get.

detailed description

Example 1

(a) Adding 1.4 g of copper chloride, 3.2 g of 2,2-bipyridine to a 500 mL titanium alloy stirred high pressure autoclave, dissolving in 20 mL of methanol, replacing the air in the autoclave with nitrogen, and pressing 312 g of R123 with nitrogen. 63 g CH ₂ = CHCl, reaction temperature 120 ° C, reaction pressure 1.2 MPa, reaction time 10 hours, the crude product after reaction was removed by atmospheric distillation to remove R123 and methanol, R123 and methanol were recycled, and the distillation was continued to collect CF ₃ CHClCH _{2 under} reduced pressure. CHCl _{2 had a} conversion of 91.3% and a selectivity of 87.6%.

(b) Adding 150 g of CF ₃ CHClCH ₂ CHCl _{2 to a} solution of 300 mL of carbon tetrachloride in a 500 mL quartz photochemical reactor, slowly introducing about 140 g of chlorine gas under stirring, reacting at 0 ° C for 24 hours, and decompressing. After separation of carbon tetrachloride by distillation, the product CF ₃ CHClCH ₂ CCl ₃ was continuously collected with a conversion of 90.5% and a selectivity of 78.7%.

(c) In a fixed-tube tubular reactor of nickel tube having an inner diameter of 38 mm, 60 ml of a fluorination catalyst was introduced, and HF and 1,1,1-trifluoro-2,4,4,4-tetrachlorobutane were introduced. CF ₃ CHClCH ₂ CCl ₃ was reacted, the molar ratio of HF/CF ₃ CHClCH ₂ CCl ₃ was controlled to 6:1, the contact time was 6.9 seconds, the reaction temperature was 350 ° C, and the reaction was continuously carried out for 20 hours, and the reaction product was washed with water and alkali. After washing with HCl and HF, the conversion of CF ₃ CHClCH ₂ CCl ₃ was analyzed by gas chromatography to be 100%, and the trans selectivity was 95.8%.

Examples 2 to 20 were synthesized according to the same synthesis method in the step (a) as CF ₃ CHClCH ₂ CClX ₂ except that the conditions of the reaction temperature, the pressure, the reaction time and the olefin type were optimized for each of Examples 2 to 20.

Table 1 reaction temperature effect

Example	catalyst(%)	temperature reflex	Conversion rates(%)	Selectivity (%)
					2	2	100	94.7	96.6
3	2	120	97.0	90.3
					4	2	140	85.7	80.6
5	2	80	32.9	86.4

6

2

180

89.3

38.7

Table 2 pressure on the reaction

Table 3 reaction time on the reaction

Table 4 Effect of olefin species on reaction

Example	Olefins	temperature reflex	Conversion rates(%)	Selectivity (%)
					18	CH 2 =CH 2	130	100	94.5
19	CHCl=CH 2	130	96.3	89.2
					20	CCl 2 =CH 2	130	74.3	63.1

From the results of Examples 2 to 20, the optimum conditions for the reaction of the step (a) are: a reaction temperature of 100 to 130 ° C, a reaction pressure of 1.2 to 2.0 MPa, and a reaction time of 5 to 24 hours.

Examples 21 to 42 were synthesized according to the same synthesis method in the step (b) as CF ₃ CHClCH ₂ CCl ₃ , except that the reaction temperature, reaction time, reaction solvent and material ratio of the steps (b) of Examples 21 to 42 were respectively carried out. Condition optimization was performed.

Table 5 reaction temperature effects

Table 6 reaction time on the reaction

Table 7 Effect of reaction solvent on the reaction

Table 8 Effect of chlorine gas consumption on reaction

Example	Solvent	Chlorine molar ratio	Conversion rates(%)	Selectivity (%)
					38	CCl 4	1:1	43.6	78.7

39	CCl 4	1.2:1	98.6	80.2
					40	CCl 4	1.5:1	96.2	75.9
41	CCl 4	2.0:1	96.9	68.3
					42	CCl 4	3.0:1	97.8	57.8

From the results of Examples 21 to 42, the optimum conditions for the reaction of the step (b) are: the reaction temperature is -10 to 40 ° C, the reaction time is 12 to 36 h, and the molar ratio of chlorine gas to CF ₃ CHClCH ₂ CClX ₂ is 1.2 to 1.4:1. .

Examples 43 to 58 were synthesized according to the same synthesis method as in the step (c): trans-1,1,1,4,4,4-hexafluoro-2-butene, except that the examples 43 to 58 were respectively The reaction temperature, molar ratio and contact time of step (c) were conditionally optimized.

Table 9 reaction temperature effect

Table 10 molar ratio on the reaction

Example	temperature reflex	The molar ratio of	Conversion rates(%)	Selectivity (%)
					48	350	1:3	70.5	84.7
49	350	1:5	94.6	90.3
					50	350	1:10	100	95.7
51	350	1:15	100	92.1
					52	350	1:20	100	90.7

Table 11 Contact time impact on the reaction

From the results of Examples 43 to 58, the optimum conditions for the reaction of the step (c) are: a reaction temperature of 300 to 400 ° C, a molar ratio of HF to CF ₃ CHClCH ₂ CCl _{3 of} 1:6 to 10, and a contact time of 3 to 8 s.

Claims (9)

1. Method for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene, trans-1,1,1,4,4,4-hexafluoro-2-butene The structural formula is as shown in formula (I):

   

   Includes the following steps:

   (a) a molar ratio of 1,1,1-trifluoro-2,2-dichloroethane to CH ₂ =CX _{2 of} from 1 to 10:1 in the presence of a telomerization catalyst and a catalytic aid in a polar solvent , the reaction temperature is 80-180 ° C, the reaction pressure is 0.8-5.0 MPa, the reaction is 1 to 48 h, and CF ₃ CHClCH ₂ CClX _{2 is obtained} , wherein X is Cl or H, and the telomerization catalyst is 0-valent, monovalent or divalent. Copper salt

   (b) chlorine gas and CF ₃ CHClCH ₂ CClX ₂ molar ratio of 1 ~ 3: 1 under light, temperature -40 ~ 80 ° C, reaction 5 ~ 48h, to obtain CF ₃ CHClCH ₂ CCl ₃ ;

   (c) controlling the molar ratio of HF to CF ₃ CHClCH ₂ CCl ₃ in the presence of a fluorination catalyst from 1:3 to 20 through a tubular fixed-bed reactor at a reaction temperature of 100 to 500 ° C and a contact time of 0.1 to 10 s. Trans-1,1,1,4,4,4-hexafluoro-2-butene was obtained.
2. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein the raw material CH ₂ =CX ₂ is CH ₂ =CH ₂ , CH ₂ =CHCl Or CH ₂ =CCl ₂ .
3. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein CF ₃ CHClCH ₂ CClX ₂ is CF ₃ CHClCH ₂ CH ₂ Cl, CF ₃ CHClCH ₂ CHCl ₂ or CF ₃ CHClCH ₂ CCl ₃ .
4. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein the telomerization catalyst in the step (a) is elemental copper or halogenated copper. , cuprous halide, copper salicylate, copper oxalate or Copper acetylacetonate.
5. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein the catalytic auxiliary in the step (a) is 2,2-bipyridine. , pentamethyldiethylenetriamine, tris(2-pyridylmethyl)amine or tris(2-dimethylaminoethyl)amine.
6. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein the polar solvent in the step (a) is acetonitrile, methanol or acetone. , dimethylformamide or dimethyl sulfoxide.
7. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein the fluorination catalyst described in the step (c) is a compound containing an iron element A compound containing a rare earth metal element, wherein the rare earth metal is La or Ce, and the A element is selected from one of Ca, Al, Mg, and Ti.
8. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 7, wherein the fluorination catalyst is composed of 10 to 50% of iron, 48 to 89.5% of A element and 0.5-2% of rare earth element.
9. The method for synthesizing 1,1,1,4,4,4-hexafluoro-2-butene according to claim 1, wherein:

   (a) a molar ratio of the starting material CH ₂ =CX ₂ to 1,1,1-trifluoro-2,2-dichloroethane of 2 to 5:1 in the presence of a copper salt and an organic amine ligand in methanol, The reaction is carried out for 5 to 24 hours in acetonitrile or dimethyl sulfoxide, the reaction temperature is 100 to 130 ° C, the reaction pressure is 1.2 to 2.0 MPa, and CF ₃ CHClCH ₂ CClX _{2 is} synthesized, wherein X is Cl or H;

   (b) Under a high pressure mercury lamp, the molar ratio of chlorine gas to CF ₃ CHClCH ₂ CClX ₂ is 1.2 to 1.4:1 in carbon tetrachloride, 1,1,2-trichlorotrifluoroethane or chlorobenzene, -10~ 40 ° C, the reaction 12 ~ 36h, the synthesis of CF ₃ CHClCH ₂ CCl ₃ ;

   (c) In the presence of Fe-based gas phase fluorination catalyst, control the molar ratio of HF to CF ₃ CHClCH ₂ CCl ₃ 1:6-10 through a tubular fixed-bed reactor, the reaction temperature is 300-400 ° C for fluorination reaction, contact time 3 to 8 s, trans-1,1,1,4,4,4-hexafluoro-2-butene is obtained.