A safe and efficient process for the preparation of difluoromethane in continuous flow

Abstract

Difluoromethane is typically produced via liquid-phase fluorination as performed in a batch reactor. However, this process suffers from some problems, e.g. , severe corrosion of the reactor, high safety risk, and the regeneration of the catalyst. In this paper, a flow process as performed in the tubular reactor was designed. The optimum conditions for continuous synthesis of difluoromethane were obtained as follows: the reaction temperature was 100 °C, the molar ratio of dichloromethane to hydrogen fluoride was 1.6:1 and the reaction time was 300 s. The operation of the cyclic process was stable for 24 h with the conversion per pass of hydrogen fluoride up to 16.2%. The unreacted raw materials were easily reused. The deactivation of the common catalyst, antimony pentachloride, was investigated by catalyst concentration curve and XPS analysis. The approach proposed in this work is proven to be safe, efficient and low amount of catalyst. A safe and efficient fluorination process for the preparation of difluoromethane continuous flow methodology was developed. The mechanism on the deactivation of the catalyst SbCl 5 was clarified.