Processes for hydrofluorination of 2-chloro-3,3,3-trifluoropropene to 2-chloro-1,1,1,2-tetrafluoropropane

The present application claims priority based upon U.S. Provisional Application Ser. No. 61/073,186, filed Jun. 17, 2008, which is incorporated herein by reference in its entirety.

1. Field of the Invention

The invention relates to processes for the hydrofluorination of 2-chloro-3,3,3-trifluoropropene(1233xf) to 2-chloro-1,1,1,2-tetrafluoropropane(244bb).

2. Description of the Related Art

Antimony halides have previously been described as useful as catalysts in the hydrofluorination of 1233xf to 244bb. Antimony pentachloride has been observed to be particularly active in catalyzing the hydrofluorination reaction (as disclosed in U.S. Provisional Patent Application 61/021,121, filed Jan. 22, 2008) but sometimes induces overfluorination of 1233xf to form pentafluoro compounds, such as 1,1,1,2,3-pentafluoropropane(245cb). 245cb has a lower boiling point than the desired 244bb product, which makes it difficult and costly to separate and remove. Antimony pentachloride can still be employed as a catalyst, but a lengthy induction or conditioning period is necessary to allow the catalyst to age.

It would be desirable to have a process for hydrofluorination of 1233xf to 244bb in which the induction period would be substantially reduced or eliminated. It would also be desirable to have a process for hydrofluorination of 1233xf to 244bb with improved yield and selectivity.

According to the present invention, there is a process for hydrofluorinating 2-chloro-3,3,3-trifluoropropene to 2-chloro-1,1,1,2-tetrafluoropropane. The process has the step of contacting the 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride in the presence of a catalyst having about 25 to about 99.9 mole percent antimony pentachloride and about 0.1 to about 75 mole percent of a metal of a Lewis acid under conditions sufficient to form the 2-chloro-1,1,1,2-tetrafluoropropane. The metal of a Lewis acid is preferably selected from among SbCl 3 , TiCl 4 , SnCl 4 , TaCl 5 , NbCl 5 , NbCl 3 , ZrCl 4 , and HfCl 4 .

Further according to the present invention, there is a process for making 2-chloro-1,1,1,2-tetrafluoropropane. The process has the step of hydrofluorinating about 75 to about 99.9 mole percent 2-chloro-3,3,3-trifluoropropene and about 0.1 to about 25 mole percent of one or more other hydrocarbons having at least one chlorine atom in the presence of a catalyst of fluorinated antimony pentachloride under conditions sufficient to form the 2-chloro-1,1,1,2-tetrafluoropropane.

Still further according to the present invention, there is process for hydrofluorinating 2-chloro-3,3,3-trifluoropropene to 2-chloro-1,1,1,2-tetrafluoropropane, comprising contacting the 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride in the presence of a vapor phase catalyst under conditions sufficient to form the 2-chloro-1,1,1,2-tetrafluoropropane.

In the present invention, the problem of an overactive fluorinated antimony pentachloride (SbCl 5 ) catalyst is addressed by two techniques. The first technique is to intermix with the SbCl 5 a minor proportion of a fluorinated Lewis acid catalyst to moderate the reaction rate. The second technique is to admix a minor proportion of one or more other hydrocarbons having at least one chlorine atom with the 1233xf starting material. The hydrocarbons are underfluorinated relative to 1233xf and reduce the effective activity of the catalyst. Essentially, in the first technique, the composition of the catalyst is modified, and, in the second technique, the composition of the starting reactant is modified. The two techniques can be employed separately or in combination.

In the first technique, the fluorinated Lewis acid catalyst is intermixed with antimony pentachloride prior to fluorination such that the catalyst composition has about 25 mole percent to about 99.9 mole percent antimony pentachloride and about 0.1 mole percent to about 75 mole percent fluorinated Lewis acid catalyst. Preferably, the catalyst composition is about 50 mole percent to about 98 mole percent antimony pentachloride and about 2 mole percent to about 50 mole percent fluorinated Lewis acid catalyst. The fluorinated Lewis acid is preferably selected from among SbCl 3 , TiCl 4 , SnCl 4 , TaCl 5 , NbCl 5 , NbCl 3 , ZrCl 4 , and HfCl 4 . Most preferably, the catalyst composition is about 75 mole percent to about 95 mole percent antimony pentachloride and about 5 mole percent to about 25 mole percent fluorinated Lewis acid catalyst. The fluorinated Lewis acid is preferably selected from among SbCl 3 , TiCl 4 , SnCl 4 , TaCl 5 , NbCl 5 , NbCl 3 , ZrCl 4 , and HfCl 4 . Mixing of the antimony pentachloride and the fluorinated Lewis acid catalyst can be accomplished by any means known in the art.

In the second technique, the 1233xf reactant is admixed with a minor proportion of one or more other hydrocarbons containing at least one chlorine atom such that 1233xf is present from about 75 to about 99.9 mole percent and the one or more hydrocarbons are present from about 0.1 to about 25 mole percent. Preferably, the 1233xf is present from about 85 to about 99.5 mole percent and the one or more hydrocarbons are present from about 0.5 to about 15 mole percent. Most preferably, the 1233xf is present from about 90 to about 99 mole percent and the one or more hydrocarbons are present from about 1 to about 10 mole percent.

Useful other hydrocarbons include those containing at least one chlorine atom. Examples of hydrocarbons having at least one chlorine atom; 1,1,2,3-tetrachloropropene; 2,3-dichloro-3,3-difluoropropene; 2,3,3-trichloro-3-fluoropropene; and 1,1,1,2,3-pentachloropropane (HCC-240db). Also useful are those generating 2-chloro-3,3,3-trifluoropropene or 2-chloro-1,1,1,2-tetrafluoropropane. These compounds are particularly useful as they will all result in the desired 2-chloro-1,1,1,2-tetrafluoropropane or an intermediate that will convert to 2-chloro-1,1,1,2-tetrafluropropane.

For either technique, the hydrofluorination reaction is carried out under conditions sufficient to form 244bb (2-chloro-1,1,1,2-tetrafluoropropane). The reaction is preferably carried out at a temperature of about 30° C. to about 200° C., more preferably about 50° C. to about 150° C., and most preferably about 75° C. to about 125° C. The reaction is preferably carried out at a pressure of about 5 psia (pounds per square inch absolute) to about 200 psia, more preferably about 30 psia to about 175 psia, and most preferably about 60 psia to about 150 psia. The reaction is preferably carried out for a residence time of about 1 second to about 300 seconds, more preferably about 30 seconds to about 240 seconds, and most preferably about 40 seconds to about 120 seconds for a continuous process. The reaction can also be carried out in batch process. In case of using batch process, the reaction is preferably carried out for a residence time of about 15 second to about 3600 seconds, more preferably about 60 seconds to about 1800 seconds, and most preferably about 120 seconds to about 300 seconds. Residence time is the reactor volume that contains the liquid phase reactant mixture divided by the volumetric flow rate of the products.

For either technique, the by-product selectivity, i.e., selectivity for products other than the desired 244bb (2-chloro-1,1,1,2-tetrafluoropropane), is less than 15 mole percent, preferably less than 5 mole percent, and most preferably less than 1.5 mole percent.

When reaction is conducted in a vapor phase process, the catalyst may be supported or in bulk form (unsupported). Useful catalyst supports include carbon, alumina, fluorinated alumina, aluminum fluoride, alkaline earth metal oxides, fluorinated alkaline earth metals, zinc oxide, zinc fluoride, tin oxide, and tin fluoride.

The catalyst optionally may be activated prior to and during use. Useful activating agents include anhydrous hydrogen fluoride and chlorine. The catalyst is kept activated by the continuous or batch addition of an oxidizing agent such as Cl 2 .

The hydrofluorination reaction may be carried out in the liquid phase or the vapor phase. Liquid-phase reactions are preferred.

The following are examples of the present invention and are not to be construed as limiting.

In the following examples, 2-chloro-3,3,3-trifluoropropene(1233xf) was fluorinated to 244bb. In Comparative Example 1, using a catalyst system of 100% antimony pentafluoride (SbCl 5 ). In Examples 1 and 2, a catalyst system of antimony pentachloride/antimony trichloride in a 5:1 mole ratio was substituted for the antimony pentafluoride catalyst system of Comparative Example 1. In Example 3, a 2% mix of 1,1,2,3-tetrachloropropene in 98% 2-chloro-3,3,3-trifluoropropene by weight is used early in the run to reduce the activity of the catalyst system, and thereby the formation of 1,1,1,2,2-pentafluoropropane. Example 4 demonstrates the use of vapor phase fluorination of 2-chloro-3,3,3-trifluoropropene to produce 244bb.

In Examples 1 and 2, the mixing of the antimony pentachloride/antimony trichloride was accomplished by adding a weighed amount of antimony pentachloride (liquid) first to a round-bottom flask equipped with a heating mantle, stirring bar, and condenser. A weighed amount of antimony trichloride (solid) was then added to the same flask. The flask was then heated to accomplish dissolution of the trichloride into the mixture and to exceed the melting point of the mixture (40-50 degrees Celsius). The molten catalyst mixture was then transferred to a heated (to prevent selective precipitation) cylinder. Nitrogen was added under pressure to the heated cylinder. The cylinder was connected to the reactor using a flexible tube. The contents of the cylinder was transferred to the reactor by opening a cylinder valve. The cylinder was weighed and compared to the cylinder's empty weight to ascertain that the desired weight transfer had been achieved. Hydrogen fluoride is added to the catalyst to achieve a fluorinated catalyst, which analysis will reveal is a mix of fluoride and chloride.

Comparative Example 1

Comparative Example 1 (Run #38) was a liquid phase fluorination of 2-chloro-3,3,3-trifluoropropene(1233xf) to 244bb using a catalyst system of antimony pentafluoride (SbCl 5 ). Comparative Example 1 demonstrated the effect of a long induction period when the run produced the 1,1,1,2,3-pentafluoropropane(245cb) byproduct in quantities of up to mole 50% by mole early in the Run, decreasing to reasonable levels (below ˜1.5%) by mole after about 60 hours. Production of 245cb byproduct decreased with the age of the catalyst.

About 4175 grams of new SbCl 5 were added into Reactor R11. R11is a Teflon™-lined liquid phase reactor (Teflon is a trademark of E.I. duPont de Nemours & Co) equipped with a 2-inch ID (inside diameter) catalyst stripper (a packed column to keep catalyst from escaping from the reactor system). The reactor is 2.75-inch ID×36-inch L (length). The reactor was heated to about 85° C.-87° C. HF feed was started first. After 1.3 lbs (pounds) of HF had been added to fluorinate the catalyst charge, the 2-chloro-3,3,3-trifluoropropene feed was started. The purity of the 2-chloro-3,3,3-trifluoropropene feed stock was about 98 GC Area % (gas chromatograph). The experiment ran continuously for about 136 hours. For this run, Cl 2 was fed batchwise about every 4 hours throughout the run in case needed to keep the catalyst active. The HF and 2-chloro-3,3,3-trifluoropropene feeds were varied during the run. The feeds averaged 0.495 lbs/hr (pounds/hour) HF, and 0.408 lbs/hr 2-chloro-3,3,3-trifluoropropene (chlorine was 5.4% by weight of organic) for a 7.9/1 ratio of HF/2-chloro-3,3,3-trifluoropropene, and 135 seconds residence time. In the middle of the run, the feeds averaged 0.843 lbs/hr HF and 0.66 lbs/hr 2-chloro-3,3,3-trifluoropropene (chlorine was 3.3% by weight of organic) for a 8.33/1 ratio of HF/2-chloro-3,3,3-trifluoropropene, and 80 seconds residence time. For the end of the run, the rate was increased. The feeds for this period averaged 1.42 lbs/hr HF and 1.24 lbs/hr 2-chloro-3,3,3-trifluoropropene (chlorine was 2% by weight of organic) for a 7.5/1 ratio of HF/2-chloro-3,3,3-trifluoropropene, and 47 seconds residence time. The reactor temperature range for the experiment was 78-91° C. and the pressure range was 85 psig-115 psig (pounds per square inch gauge). Results on a molar basis are set forth in Table 1 below.