Preparation method of pentafluoroethane

Abstract

This invention relates to a preparation method of pentafluoroethane (HFC-125). It takes hydrogen fluoride (HF) and tetrachloroethene (PCE) as raw material, used two reaction vessel through two-step gaseous phase fluoridation to prepare HFC-125. The first reactor mainly fluorate PCE to synthesize 2,2 - dichloro-1 ,1,1 - halothane (HCFC-123) and 2-chloro-1 ,1,1,2 - tetrafluoroethane (HCFC-124); the second reaction mainly fluorate at least one of HCFC-123, HCFC-124 to synthesize HFC-125. Using distillation column to take PCE from the products of first reactor, and then circulate to first reactor. Take phase separator to separate HF, HCFC-123 and HCFC-124 from products of first and second reactor, HF can circulate to first and second reactor for continues reaction, HCFC-123 and HCFC-124 can be recycled to the second reactor continued reaction, but also can through distillation and separation to obtain HCFC-123 and HCFC-124 products. The invention mainly for prepare pentafluoroethane.

Description

technical field [0001] The invention relates to a method for preparing pentafluoroethane, in particular to a method for preparing HCFC-123 and HCFC-124 through the catalytic reaction of tetrachloroethylene and hydrogen fluoride, and then making HCFC-123 and HCFC-124 further catalyzed by fluorination to produce pentafluoroethane. Fluoroethane method. This method is mainly used for the preparation of pentafluoroethane and the preparation of HCFC-123 and HCFC-124. Background technique [0002] Pentafluoroethane (abbreviated as HFC-125) is a fluorinated hydrocarbon compound that is safe for the atmospheric ozone layer and is currently mainly used as a substitute for 1-chloro-1,1-difluoromethane (HCFC-22) refrigerant , In addition, it is also widely used as foaming agent, solvent, propellant, fire extinguishing agent and dry etchant. [0003] There are three known methods for the industrial synthesis of HFC-125. One approach is to fluorinate a suitable precursor with HF in the...

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Problems solved by technology

The third method has more steps, and each step has different reaction types and requires different catalysts, and the process and actual operation are relatively complicated.

[0007] In the above-mentioned patents, a single fluorination reactor is used. Due to the difference in boiling point and phase between the intermediate products HCFC-123, HCFC-124 and unreacted PCE and HF recycled to the fluorination reactor, and HCFC-123, HCFC Both -124 and HF have an azeotropic phenomenon, which can easily lead to unstable material ratio entering the fluorination reactor, resulting in unstable fluorination reaction and difficult operation; even resulting in the phenomenon that the reaction system material does not have HF, which will cause rapid coking of the catalyst. Live, seriously affect the life of the catalyst

Simultaneously, since PCE, HCFC-123 and HCFC-124 carry out the fluorination reaction in the same reactor, the conversion rate of PCE is relatively low due to the restriction of the reaction balance influenced by the presence of HCFC-123 and HCFC-124, and the reaction temperature is relatively low. High, aggravated the coking speed of the catalyst

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