Method for preparing 1,1,1,3,3-pentafluoropropane

Abstract

A process for the production of C2-C4 hydrofluorocarbon, such as 1,1,1,3,3-pentafluoropropane, by contacting a non-fluorinated hydrochlorocarbon with a fluorinating agent, such as hydrogen fluoride, in a liquid catalyst system preferably comprising fluorinated superacid catalyst prepared from SbF5, NbF5, TaF5 or TaF5 / SnF4 and HF.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to method of producing hydrofluorocarbons, and particularly lower alky hydrofluorocarbons, from hydrochlorocarbons. [0003] 2. Description of Related Art [0004] It is known that when certain halocarbons are released into the atmosphere, they undergo reactions that result in the depletion of the Earth's ozone layer. Examples of environmentally harmful halocarbons include certain hydrochlorocarbons (HCCs), hydrochlorofluorocarbons (HCFCs), and chlorofluorocarbons (CFCs). One such CFC is trichlorofluoromethane (CFC-11), a compound that conventionally has been used in foam insulation applications. Due to CFC-11's potential for environmental damage, replacements for this compound have been sought. One proposed substitute for CFC-11 in foaming application is 1,1-dichloro-1-fluoroethane (HCFC-141b). Although HCFC-141b also adversely affects the ozone layer, its impact is significantly less than...

AI Technical Summary

Benefits of technology

[0010] Although not wanting to be bound to any particular theory, it is thought that when a fluorinating agent, particularly HF, reacts in the presence of metal halide catalyst, such as SbF5, TaF5, and NbF5, an exothermic reaction occurs to form a superacid system. It is believed that this reaction may occur according to the following reaction scheme: 2HF+MF5→[H2F](+)[MF6](−) The higher Lewis acidity of super-acids such as anhydrous hexafluoroantiminic acid (HSbF6), anhydrous hexafluorotantalic acid (HTaF6), or anhydrous hexafluoroniobic acid (HNbF6) relative to conventional acid catalysts such as “HSbCl5F” and “HSbF4Cl2” (as measured by the Hammet scale) allow for lower concentrations of catalyst to be employed while still achieving similar productivity. In addition, the reaction mechanism may be different than the “Swarts” reaction based systems which are presumably dominant under conditions of high SbCl5 concentration and low HF concentration. Moreover, compared to conventional acid catalysts, fully fluorinated superacids require much less, if any, oxidants (such as chlorine) to maintain their activity, thus further lowering yield losses due to the presence of Cl2 in the reaction system and further lowering the corrosive tendency of the reaction system. The corrosion of reactors which use lower concentrations of fully fluorinated superacid catalyst is considerably less compared to conventional high SbCl5 concentration system. The latter has been demonstrated to be very corrosive to metals such as Hastelloy C and Monel 400. Also, the low catalyst concentration system of certain preferred aspects of the present invention has other benefits, such as the low viscosity and the presence of only one liquid phase in the reactor.

Problems solved by technology

It is known that when certain halocarbons are released into the atmosphere, they undergo reactions that result in the depletion of the Earth's ozone layer.

Unfortunately, the reaction conditions (e.g. reactant and catalyst concentrations, temperatures, pressures and the need for oxidants such as chlorine to maintain catalyst activity) required to promote this halogen exchange process can be extremely corrosive to metals commonly used for liquid phase reactors, such as Monel, Inconel and Hastelloy C. As a result of the extremely corrosive reaction environment most reactors used for fluorination processes must be lined with fluoropolymers.

However, these lined reactors suffer from poor heat transfer and HF permeation of the liner.

In addition, the use of Cl2 as an oxidant results in a yield loss due to chlorination of various raw materials, intermediates, and reactants.

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