WO1993024433A1

WO1993024433A1 - Process producing a hydrofluorocarbon having at least one trifluoro group

Info

Publication number: WO1993024433A1
Application number: PCT/US1993/005282
Authority: WO
Inventors: Michael Van Der Puy
Original assignee: Allied-Signal Inc.
Priority date: 1992-06-03
Filing date: 1993-06-02
Publication date: 1993-12-09

Abstract

The present invention relates to a process for the reductive dechlorination of a hydrochlorofluorocarbon having at least one trifluoromethyl group and at least one chlorine in the presence of a catalyst selected from platinum, palladium and rhodium to produce a hydrofluorocarbon in a single step under neutral conditions. The present invention further relates to a two step process wherein the hydrochlorofluorocarbon to be reductively dehalogenated is synthesized by reacting an olefin with 1,1,1-trichlorotrifluoroethane and the novel addition products produced thereby.

Description

PROCESS PRODUCING λ HYDROFLϋOROCARBON HAVING AT

LEAST ONE TRIFLUORO GROUP

Background of the Invention

The preparation of partially fluorinated organic compounds, particularly those containing at least one trifluoro group, has received much attention. Such compounds find use in a variety of applications including pharmaceutical and agricultural intermediates. Recently, interest in hydrofluorocarbons has increased because of their potential use as stratospherically safe materials for use as solvents, refrigerants, blowing agents, and sterilant gases.

The production of hydrofluorocarbons (HFCs) via selective hydrogenation of a commercially available hydrochlorofluorocarbon (HCFC) or chlorofluorocarbon (CFC) is a desirable method for the production of hydrofluorocarbons (HFCs). DE 3,917,573 discloses the preparation of 1,1,1,2-tetrafluoroethane by the selective hydrogenation of l,l-dichloro-l,2,2,2,- tetrafluoroethane in the presence of a Pd on alumina catalyst. Selective hydrogenation of HCFCs having more than two carbons, or of non-primary chlorines is not disclosed. Many HFCs containing at least one trifluoromethyl group have no commercially available HCFC counterparts. However, general processes for producing such HCFCs counterparts are known in the art. For example, the synthesis of HCFCs containing a trifluoromethyl group via the reaction of 1-octene with a variety of trifluoropolyhaloalkanes (including CF₃CC1₃) in the presence of a copper chloride catalyst and an ethanola ine cocatalyst was disclosed by D. Burton and L. J. Kehoe (J. Org. Chem. , 1970, 35, 1339). The addition of polyhalogenated alkane (including CF₃CC1₃) to alkyl substituted butenes (including 3-methylbut-l- ene) in the presence of a metal halide catalyst and an a ine cocatalyst to prepare intermediates for insecticides is disclosed in U.S. Patent 4,228,107. Also disclosed are polyhalogenated hydrocarbons of the general formula:

wherein R is hydrogen or a lower alkyl group, R¹ is lower alkyl, X is chloro, bromo or iodo, Y is fluoro, chloro or bromo, Z is ϊ or Q, and Q is a group of formula W(CF₂)__. where is hydrogen, fluoro or chloro and m is 1 or 2, provided that X is always bromo or iodo when at least one of Y and Z is bromo. No method for converting the HCFC to the HFC is disclosed.

Thus, there remains a need in the art for a process for converting HCFCs containing at least one trifluoromethyl group to the corresponding HFC, and also for producing hydrofluorocarbons containing at least one trifluoro group from starting materials which are readily available.

Detailed Description

The present invention relates to a process for the reductive dechlorination of a hydrochlorofluorocarbon having at least three carbons, at least one trifluoromethyl group and at least one non-primary chlorine hydrochlorofluorocarbon in the presence of a catalyst selected from platinum, palladium and rhodium to produce a hydrofluorocarbon in a single step under neutral conditions. The present invention further relates to a two step process wherein the hydrochlorofluorocarbon to be reductively dehalogenated is synthesized by reacting an olefin with 1,1,1- trichlorotrifluoroethane. Also disclosed are novel addition products having the general formula: H Cl

I I CF₃-CC1₂-C-C-Y I i Z X wherein Z is selected from H and lower alkyl, X is selected from H, alkyl, alkenyl, halogenated alkyl and halogenated alkenyl, Y is selected from alkyl, alkenyl, halogenated alkyl and halogenated alkenyl, and where Z and X are H, Y is not isopropyl or hexyl. Hydrochlorofluorocarbons which may be reductively dechlorinated according to the present invention comprise at least three carbons, at least one trifluoro group and at least one non primary chlorine. A non- primary chlorine is one which is bonded to a non¬ terminal carbon. Preferably the hydrochlorofluorocarbon has at least 4 carbon atoms. More preferably the hydrochorofluorocarbon has between 4 and 25 carbon atoms and most preferably between 4 and 15 carbons. The hydrochlorofluorocarbons may be straight chained, branched, or cyclic and may have any substitution on the main chain which does not interfere with, and is reduced by the reductive dechlorination, such as H, saturated or unsaturated hydrocarbyl or halohydrocarby1 , saturated or unsaturated hydroxy, carbonyl, cyano or nitro groups.

The reductive dechlorination is carried out in the presence of a catalyst comprising a metal selected from the group comprising platinum, palladium, and rhodium on an inert supj -rt. Typically the metal is deposited on the support as an oxide or a salt. The catalyst may be pretreated with hydrogen or used without pretreat ent. The metal oxide or salt is converted to the metal via the pretreatment and during use. The support may be carbon granules, alumina or any other support may be carbon granules, alumina or any other form generally practical in flow systems. For reasons of economy, palladium over carbon is preferred over Pt/C. Commercially available Pd/C is available at concentrations ranging from about 0.5% to 10% by weight palladium.

The chlorofluorocarbon and H₂ are passed over the catalyst. At least 3 moles of H₂ per mole chlorofluorocarbon are required by the reaction stoichiometry. Preferably an excess is used. Most preferably, about 9 moles of H₂ per 1 mole chlorofluorocarbon is used.

Hydrogen is used in excess of the stoichiometric requirement of 3 moles hydrogen per mole of chlorofluorocarbon, to increase conversion, and may be adjusted as necessary to control the residence time in the reactor. The residence time depends on the reaction temperature; as the reactor temperature decreases the residence time required to insure complete reaction increases. Generally residence times between 1 and 60 seconds are sufficient.

Prior to the present invention dehalogenations carried out in neutral media in the presence of palladium on carbon, platinum or rhodium did not proceed completely ("halogen was not removed from primary and secondary alkyl chlorides and bromides", M. Freifelder, "Practical Catalytic Hydrogenation", Wiley, New York, 1971, p 446-449) or resulted in reduction to the alkane (isopropyl fluoride reduced to the corresponding alkane, using neutral palladium on carbon at temperatures as low as 155*C, Lacher et. al., J. Physical Chem. , 1956, 60, 1454). It has been surprisingly found that the reductive dehalogenation of the present invention replaces all of the chlorines in the chlorofluorocarbon without reducing any of the fluorines. Thus, environmentally undesirable HCFCs containing at least one trifluoro group may be selectively reduced to non-ozone depleting HFCs containing at least one trifluoromethyl group in a single step. Unsaturated substituents may be saturated, oxygen may be replaced with hydrogen and nitriles may be converted to amines. The resulting HFCs containing at least one trifluoromethyl group and have utility as non-ozone depleting refrigerants, sterilant gases, blowing agents and solvents.

Hydrochlorofluorocarbons (HCFCs) which may be dechlorinated via the present invention may be made via any method known in the art. For example, HCFCs may be made by reacting an olefin with 1,1,1- trichlorotrifluoroethane (HCFC-113a) . Olefins can be straight chain, branched or cyclic. Examples of suitable olefins are ethylene, butene, propylene, isomeric pentenes, isomeric hexenes, 1,1,1- trifluoropropene, 2-trifluoromethylpropene, cyclopentene, cyclohexene, and 2-trifluoromethyl-l,1,1- trifluoropropene. Because the rate of reaction decreases with substitution on the unsaturated carbon atoms, terminal olefins (RCH=CH₂) are preferred. Thus, the number of halogens or haloalkyl groups on the unsaturated carbon-, is preferably less than two, and is most preferably zero.

The reaction between the olefin and 1,1,1- trichlorotrifluoroethane is carried out in a suitable solvent. Any solvent may be used so long as all of the reactants are soluble therein. Suitable solvents include lower alcohols, nitriles and dimethylforma ide. Preferred solvents are t-butanol, isopropanol, acetonitrile and 1,1,1-trichlorotrifluoroethane. The preferred solvent for olefins having four carbons is t- butanol. Various catalysts may be used for the addition of 1,1,1-trichlorotrifluoroethane to substituted and unsubstituted olefins. Preferably the catalyst is a metal salt such as cuprous/cupric salts or ferrous/ferric salts. Copper salts are the more preferred catalysts, with CuCl being most preferred. Mixtures of copper salts may also be used, with equal weight mixtures of CuCl and cupric chloride dihydrate being preferred. Usually between about 1:100 to about 1:10 catalyst to olefin mole ratio is necessary to insure production of the desired chlorofluorocarbon. Preferably the catalyst to olefin mole ratio is about 1:50.

Amine co-catalysts may also be added to the reaction mixture. Suitable amine co-catalysts include butylamine, N,N-dimethylethylene-diamine and ethanolamine with ethanolamine being especially preferred.

Conditions vary with the olefin used, since the reaction rates differ. Generally the reaction is monitored by the decrease in pressure of the system. Temperature limits vary with the solvent. For example temperatures below about 120*C are preferred for reactions in t-butanol; while temperatures up to about 170"C and higher can be used for reactions in acetonitrile. Temperatures between about 50^βC and about 100° are preferred.

The HCFC produced may be isolated by any common purification means known in the art such as extraction with a suitable solvent. Hydrochlorofluorocarbons are useful intermediates for the production of reduced and non-ozone depleting HFCs which have utility as non- ozone depleting refrigerants, sterilant gases, blowing agents and solvents. Example 1

A 300 mL glass pressure bottle was charged with 0.5 g of catalyst (50:50 weight mixture of CuCl and CuCl₂«H₂0) , 75 mL t-butanol, 3.0 g ethanolamine, and 50 g CF3CCI3, and evacuated briefly. Isobutylene (14.6 g) was then added, and the contents heated with an oil bath to and maintained at 85'C for 2 1/2 days. At this time the pressure in the vessel was 0 psig (lxlO³ kPa) . The cooled reaction mixture was poured into 200 L water and the lower organic layer separated. The aqueous layer was extracted with two 50 mL portions of CH₂C1₂, and the combined organic layers were washed with two 100 mL portions of water. After drying in Na₂S0_<, the volatiles were removed by rotary evaporation. Vacuum distillation (6" packed column) of the residue gave 44.4 g of a colorless liquid having a boning point of 78-82^*C at 52 mm Hg. Elemental analysis calculated for C₆H_βCl₃F₃ is C, 29.60; H, 3.31 %. The elemental analysis for the reaction product was: C, 29.59; H, 3.20%. Thus, the recovered product was shown to be 1,1,l-trifluoro-2,2,4-trichloro-4- methylpentane (98 % purity) , which was confirmed by NMR analysis.

C∑ φl^β 2

The hydrogenation reactor used in this example was a 1 inch glass tube having an internal volume of approximately 100 cc. Heat was applied by electrical heating tape wrapped around the outside of the tube. The tube was mounted vertically and packed with small glass rings in the lower one-third of the tube, followed by 25 cc of a mixture of 0.5% platinum on carbon (4 to 7 mesh, 10 cc) , 3 mm glass helices (15 cc) and the remainder of the tube was packed with glass rings. The reactor exit was connected to two dry- ice/acetone baths and a water scrubber. The reactor was purged with N₂, heated to about 230^βC near the center of the reactor (skin temperature) and then purged with H₂. The 1,1,1-trifluoro-2,2,4-trichloro-4- methylpentane produced in Example 1 was fed into the top of the reactor by means of a syringe pump at a rate of 1 cc every 9 minutes (total 32.6 g) . The reactor temperature increased to about 250"C, and was maintained at about 250^βC throughout the dechlorination. The hydrogen flow rate was adjusted to maintain a slow bubble rate in the water scrubber to insure that an excess of hydrogen is present. The gas flow was maintained for one half hour. After warming the cold traps to room temperature, 14.9 g crude product was collected. The product was analyzed via gas chromatography and found to be about 87 % 1,1,1- trifluoro-4-methylpentane and about 5% under-reduced (monochlorinated) material. Distillation of the 1,1,1- trifluoro-4-methylpentane gave 10.6 g (57%) of 1,1,1- trifluoro-4-methylpentane (99% purity) , having a boiling point of about 65-7^βC. The composition was confirmed via NMR.

gy aplf 3 A mixture of 80.5 g of CF₃CC1₃, 75 mL t-butanol, 3 g ethanolamine, 1.0 g cuprous chloride and 13.0 g cis- 2-butene was heated in a glass pressure bottle for 17 hours at about 90*C. The product, which had a boiling point of about 77-85*C at 48 mm Hg, was analyzed by 1H NMR (CDC13) which indicated that the product was a mixture of diasteromers in a ratio of about 4.6/1. The elemental analysis for the reaction product was: C, 29.31; H, 3.33%. The elemental analysis for C₆H₈C1₃F₃ was calculated as: C, 29.60%; H, 3.31 %. Thus, the recovered product was 1,1,1-trifluoro-2,2,4-trichloro- 4-methylpentane (98 % purity) , which was confirmed by NMR.

Example 4 The product of Example 3 (36.5 g) was hydrogenated as in Example 2 to give 17.7 g crude product which from GC analysis was determined to be comprised of 42% of 1,1,1-trifluoro-3-methylpentane and 40% under-reduced material (but essentially no trichlorinated material) . Distillation gave 5 g pure product, having a boiling point of about 64-7^βC (mainly 66^βC) . The presence of 1,1,1-trifluoro-3-methylpentane was confirmed by NMR analysis.

Exam l S

A glass pressure bottle was charged with 1.0 g 1:1 (wt) CuCl:CuCl₂*2H₂0, 3.0 g ethanolamine, 55 g CF₃CC1₃ and 75 mL t-butanol, and evacuated briefly. 1-Butene (16.7 g) was then added and the mixture stirred and heated to 85^*C for 15 hours, at which time the pressure in the vessel was 0 psig. The solution was extracted and dried as in Example 1. Crude product (63.5 g) was recovered, which on vacuum distillation (47-48 mm Hg) gave 44.0 g (62% yield) of product having a boiling point of about 82'C-91*C (89'C-91'C), which was believed to be 97.5 % pure 1,1,1-trifluoro-2,2,4- trichlorohexane. NMR analysis and boiling point data indicated that the product was 1,1,1-trifluoro-2,2,4- trichlorohexane. The elemental analysis calculated for C₆H₈C1₃F₃ is C, 29.60; I, 3.31 %. The elemental analysis of the product was C, 29.50; H, 3.26%.

K am la 6

The reactor in this Example was similar to that described in Example 2, except that 10 cc of 1% palladium on (4-8 mesh) carbon was used instead of platinum on carbon, and the temperature was measured internally using a thermocouple in the center of the catalyst bed. A total of 40.7 g of the 1,1,1- trifluoro-2,2,4-trichlorohexane produced in Example 5 was passed over the bed with hydrogen gas over a period of 4 2/3 hours. The temperature inside the reactor was 220*C before the organic flow was started, but increased to 244*C with organic and hydrogen passing over the catalyst bed. It was determined by GC analysis that the crude product consisted of 86 % of 1,1,1-trifluorohexane and about 12% under-reduced material. Distillation gave 15.6 g (67 % yield) 1,1,1- trifluorohexane, having a boiling point of about 74- 76*C. The infrared spectrum of the product was taken and was identical to that of 1,1,1-trifluorohexane made by the reaction of SF» with hexanoic acid.

60 g CF₃CC1₃, and 10.6 g 3-methyl-l-butene were added to t-butanol (75 mL) , 0.5 g of a 1:1 mixture of CuCl and CuCl₂H₂0 and 3 g ethanolamine and heated to 75-90*C for 20 hours. Work-up and distillation afforded 22.6 g of 2,2,4-chloro-l,l,1-trifluoro-5- methylhexane (58% yield) , which displayed a boiling point of 70-80 'C (mainly 75^*C) at 20 mm Hg (94% purity). Redistillation provided 98% pure material, having a boiling point of 75-76^*C at 20 mm Hg. Elemental analysis calculated for C₇H₁₀C1₃F₃ was: C, 32.65; H, 3.91. The elemental analysis observed for the addition product was: C, 32.48 H, 4.22. The ^~~i NMR analysis also confirmed the presence of the desired product. Example 8

A 300 mL glass pressure bottle was charged with 75 mL t-butanol 1 g CuCl, 3 g ethanolamine, 50 g CF₃CC1₃, and 16.6 g 1-hexene. After evacuating briefly, the mixture was stirred and heated to 95-100 *C for 21 hours. Workup as described in Example 1 gave 54.8 g crude material, which on distillation at 15 mm Hg gave 33.7 g of 96 % pure 2,2,4-trichloro-l,1,1- trifluorooctane (structure confirmed via NMR) , having a boiling point between 88-88.5 "C (63% yield). The elemental analysis calculated for C₈H₁₂C1₃F₃ was: C, 35.39; H, 4.45. The elemental analysis for the addition product was: C, 35.35; H, 4.55 %.

TMr-im la Q

82 g CF₃CC1₃ and 19.1 g 2-trifluoromethylpropene were combined in 75 mL t-BuOH, 1 g CuCl, and 3 g ethanolamine, and heated to 90-95^*C for 22 h. The addition product was separated as in the previous examples. Distillation of crude product gave 20.6 g

(40%) of material having a bp 61-74*C (mainly 71-73 ^βC) at 60 mm Hg. The elemental analysis calculated for C₆H_sCl₃F_β was: C, 24.23; H, 1.69. The elemental analysis for the addition product was: C, 24.17; H, 1.64, indicating that 2,2,4-trichloro-l,l,l-trifluoro- 4-trifluoromethylpentane was produced, which was confirmed by NMR.

Example 10 A mixture of 25 mL (39.6 g, 0.211 ol) CF₃CC1₃, 75 mL t-BuOH, 0.5 g of a 1:1 mixture of CuCl:CuCl₂ ^«2H₂0, 3 g ethanolamine, and 29.2 g (0.214 mol) li onene were heated to 70-75 *C for 4.5 days. Workup as in the previous examples gave 59.9 g crude material. Distillation at 2.2 mm Hg gave 5.0 g limonene and 42.1 g 2,2,4-trichloro-l,1,1-trifluoro-4-(4-methylcyclohex- 3-ene)heptane (confirmed via NMR) of about 88% purity. Redistillation at 2.2 mm Hg did not improve the purity due to partial decomposition, but distillation at 0.3 mm Hg gave 26.3 g of the addition product at 97% purity, which displayed a boiling point of 88-91°C at 0.3 mm Hg (47% based on unrecovered limonene). The elemental analysis calculated for C₁₂H₁₆C1₃F₃ was: C, 44.54; H, 4.98. The elemental analysis for the recovered addition product was: C, 44.32; H, 5.01. The main impurity had no vinylic proton (NMR) and was therefore not the isomeric product derived from addition to the endocyclic double bond. Examples 11 and 12 Even mole amounts of each of either CHCHCH₂OCH₃ or CH₂CHCN are mixed with CF₃CC1₃ and 75 mL t-butanol 1 g CuCl, 3 g ethanolamine. The mixture is heated and allowed to react until the desired products (CF₃CC1₂CH₂CHC1CH₂0CH₃ or CF₃CC1₂CH₂CHC1CN respectively) are formed. The desired products are isolated as in Examples 7 through 10. Eyap e 13-18

The chlorofluorocarbons produced in Examples 7 through 12 and listed in Table 1 below are selectively reductively dechlorinated under the conditions of

Example 2 to produce the hydrofluorocarbons listed in Table 2 below. TABLE 1

* at 745 mm Hg * at 5 mm Hg

Claims

WE CLAIM:

1. A process comprising the step of: reacting H₂ and a hydrochlorofluorocarbon having at least three carbons, at least one trifluoromethyl group and at least one non-primary chlorine over a catalyst selected from the group consisting of palladium, platinum, rhodium and mixtures thereof on an inert support under conditions sufficient to produce a hydrofluorocarbon having at least one trifluoromethyl group.

2. The process of claim 1 wherein said hydrochlorofluorocarbon is produced by reacting an olefin with 1,1,1-trichlorotrifluoroethane in the presence of a catalyst.

3. The process of claim 2 wherein said catalyst comprises at least one copper salt.

4. Polyhalogenated hydrocarbons comprising the general formula:

H Cl

Z X wherein Z is selected from H and lower alkyl, X is selected from H, alkyl, alkenyl, halogenated alkyl and halogenated alkenyl, Y 1s selected from alkyl, alkenyl, halogenated alkyl and halogenated alkenyl, and where Z and X are H, Y is not isopropyl or hexyl .

5. A composition of matter having the formula CF₃CC1₂CH₂CC1(CH₃)₂.

6. A composition of matter having the formula CF₃CCl₂CH₂CHClCH₂CHj.

7. A composition of matter having the formula CF₃CC1₂CH(CH₃)CHC1CH₃.

8. A composition of matter having the formula CF₃CC1₂CH₂CHC1(CH₂)₃CH₃.

9. A composition of matter having the formula CF₃CC1₂CH₂CC1(CF₃)CH₃.

10. A composition of matter comprising 2,2,4-trichloro-

1 , 1 , 1 - tri f 1 uoro-4- (4-methyl cycl ohex-3-ene) heptane .