MXPA00005646A - Fluorination catalyst - Google Patents

Abstract

A supported Lewis acid catalyst such as antimony V on a fluorine-treated moisture-free activated carbon support is provided, as are fluorination processes using such a catalyst.

Description

CATALYSTS FOR FLUORINATION BACKGROUND OF THE INVENTION This invention relates to novel catalysts useful in processes for the fluorination of hydrocarbons (halogenated or unsaturated), especially to supported Lewis acid catalysts such as antimony on fluorinated carbon which are useful at higher temperatures in such processes of fluorination. The technique (e.g., U.S. Patents 5,449,842; 5,208,395; and 2,749,374) has described the use of Lewis acid catalysts such as antimony (V) to catalyze fluorination processes involving the electrophilic addition of HF to unsaturated hydrocarbons or the replacement of halogen atoms (non-fluorine) of halogenated hydrocarbons with fluorine atoms. However, in processes where the reaction temperature is higher than 150 ° C, the antimony V is reduced to antimony I I I resulting in deactivation of the catalyst. Attempts to solve this problem (as in the U.S. Patent 2,749,374 mentioned above) have involved the continuous feeding of low levels of chlorine to maintain the antimony catalyst in the +5 oxidation state; this, however, causes the formation of undesirable chlorinated coproducts, which require separation and hence additional processing complications. What is desired is a catalyst for use in fluorination processes that can withstand higher temperatures without the need to introduce additional co-feeds such as chlorine.

BRIEF DESCRIPTION OF THE INVENTION A supported metal catalyst useful in fluorination processes is provided, the metal being selected from one or more of antimony, titanium, tin, niobium and tantalum (preferably antimony), the support which is an activated carbon free of fluorine-treated moisture and the catalyst that is activated with hydrogen fluoride before use, as are fluorination processes catalyzed using such supported metal catalysts.

DETAILED DESCRIPTION It has now been discovered that the incorporation of a Lewis acid catalyst in a fluoride-treated, moisture-free activated carbon support results in a catalyst which favors fluorination to occur at higher temperatures (eg, 185 °). C) without deactivation of the catalyst and without the need to introduce additional reagents such as chlorine to the fluorination process. Although the preferred catalyst metal is antimony in the +5 oxidation state, the metal can also be IV titanium, IV tin, niobium V or tantalum V. Mixtures of one or more of the metals can also be used. The metal concentration typically ranges between 0.0001 and 0.1 moles per gram of catalyst, preferably 0.001 -0.1 moles / gram. The activated carbon support is heated to dry (typically at about 180 ° C in a stream of an inert gas such as nitrogen) and treated with fluorine. By "fluorinated" is meant that the dry activated carbon is contacted with a fluorinating agent such as hydrogen fluoride, SF4, SeF4, fluorine diluted with an inert gas such as nitrogen, or an interhalogen fluorine compound such as CIF, IF or BrF3. The fluorinating agent can be added in the gas or liquid phase, batch or continuously. The addition temperature is not critical and can be, for example, varied between room temperature (about 20 ° C) and 200 ° C. An inert gas with the fluorinating agent can be used, but it is not critical. The concentration of the fluorination agent used is typically between 0.01 and 10 grams per gram of catalyst. The catalyst is subjected to normal activation procedures before being used in a fluorination process, such as feeding H F over the catalyst at about 50 ° C for 24 hours. The catalysts of this invention are useful in standard processes of fiuorination, such as gas phase fluorinations, with a typical contact time of 0.1 to 60 seconds, and fluorinations per batch in liquid phase, with a typical contact time of 1 to 5. hours, except that the use of higher temperatures is now possible, as illustrated below in the following non-limiting examples.

EXAMPLE 1 . Preparation of Antimony Catalyst in Activated, Dry, Fluorinated Carbon Support: Activated carbon (Calgon CPG, 25 grams) was charged in a reactor and heated at 180 ° C in a nitrogen stream for 24 hours. The reactor temperature was then lowered to 120 ° C and liquid HF was fed at a rate of 0.1 1 grams / minute, along with nitrogen gas (100 ccm), for 24 hours, after which the reactor temperature was lowered to 50 ° C. Nitrogen was then fed at 40 ccm, along with 0.53 ccm of antimony chloride (V) for 10 minutes (12.6 grams). The catalyst was then activated at 50 ° C with HF to prepare it for use in a fluorination process.

EXAMPLE 2. Fluorination of 142b (1-chloro-1,1-difluoroethane) to 143a (1,1,1-trifluoroethane) at low and high temperatures using the activated catalyst of Example 1: The activated catalyst was fed to a gaseous mixture of HF (285 ccm) and 142b (36 ccm) at 1 10 ° C during a contact time of 3.5 seconds. The conversion was stable (90%) and the selectivity for 143a was 100%. When the temperature was increased to 185 ° C (contact time of 7.5 seconds), the conversion was 98% and the selectivity for 143a remained 100%. When the temperature was then lowered to 1 10 ° C with a contact time of 3.5 seconds, the conversion fell again to 90%, indicating that there was no loss of antimony V from the catalyst source or reduction of antimony V to antimony III as a result of the use of higher temperatures. Also, when opening the reactor and examining the catalyst, no evidence of deposited SbF3 was found.

Claims (2)

1. CLAIMS 1. A supported metal catalyst useful in fluorination processes, the metal being selected from one or more of the group consisting of antimony V, titanium IV, tin IV, niobium V and tantalum V, the support which is an activated carbon , treated with fluorine, free of moisture, and the catalyst that is activated with hydrogen fluoride before use. 2. A supported antimony V catalyst useful in fluorination processes, the support which is an activated carbon, treated with fluorine, free of moisture, and the catalyst that is activated with hydrogen fluoride before use. 3. In processes for the catalyzed fluorination of hydrocarbons, the use as said catalyst of the supported metal catalyst of claim 1. 4. In processes for the catalyzed fluorination of hydrocarbons, the use as said catalyst of the supported antimony V catalyst of claim
2. 2.