Pd/Alumina Catalysts for Beneficial Transformation of Harmful Freon R-22

Monika Radlik,Wojciech Juszczyk,Erhard Kemnitz,Zbigniew Karpiński

doi:10.3390/catal11101178

Abstract

Chlorodifluoromethane (R-22), the most abundant freon in the atmosphere, was subjected to successful hydrodechlorination in the presence of palladium supported on γ-alumina, at a relatively low reaction temperature (180 °C). The combination of catalytic actions of alumina (performing freon dismutation) and Pd nanoparticles (catalyzing C–Cl bond splitting in the presence of hydrogen) results in the transformation of freon into valuable, chlorine-free products: methane and fluoroform, the mixture of which is used in plasma etching of silicon and silicon nitride. Very highly metal dispersed Pt/Al2O3 catalysts, with metal particles of ~1.3 nm in size, are not as effective as Pd/Al2O3, resulting in only partial dechlorination. A long-term dechlorination screening (3–4 days) showed good catalytic stability of Pd/alumina catalysts.

Highlights

Hydrochlorofluorocarbons (HCFCs) have been selected as the first, albeit still provisional, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs).Since 2015, it has been illegal in the European Union to use any HCFCs to run refrigeration and air-conditioning equipment [1]
It is imperative to note the significant use of CHClF2 in the manufacture of polytetrafluoroethylene (TeflonTN ), the process potentially involved in R-22 emission
The dual-functional behavior of Pd/alumina catalysts appeared beneficial in catalytic transformation of chlorodifluoromethane, resulting in nearly total chlorine removal (>98%) from the CHClF2 molecule at a relatively low reaction temperature (180 ◦ C)

Summary

Introduction

Hydrochlorofluorocarbons (HCFCs) have been selected as the first, albeit still provisional, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs).Since 2015, it has been illegal in the European Union to use any HCFCs to run refrigeration and air-conditioning equipment [1]. Hydrochlorofluorocarbons (HCFCs) have been selected as the first, albeit still provisional, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs). The Montreal Protocol and its 2007 amendment targeted a 97.5–100% reduction of the total production of HCFCs by 2030 for all countries. R-22 is by far the most abundant HCFC in the atmosphere, so it is imperative to continue to monitor the evolution of its atmospheric concentration [2,3,4,5]. South-East Asia have been a substantial source of R-22 emission for a number of years [5]. It is imperative to note the significant use of CHClF2 in the manufacture of polytetrafluoroethylene (TeflonTN ), the process potentially involved in R-22 emission. Huge stocks of R-22 must be destroyed or, preferably, converted to other valuable chemicals

Methods

Results

Conclusion