The hydrodechlorination of chlorodifluoromethane (HCFC-22) was performed by a catalytic reaction and noncatalytic thermal decomposition at high temperatures of 400-800°C. After 47 h of time-on-stream on a supported palladium (Pd) catalyst, the gas-phase composition of difluoromethane (HFC-32) is 41.0%, with 4.9% of the HCFC-22 remaining, indicating the conversion of up to 95.1% of HCFC-22. The supported nickel catalyst's deactivation is significant as it exhibits the low conversion of HCFC-22 under the same reaction conditions. The deactivation of the catalyst is caused by the polymerization of adsorbed methyl radicals, which competes with the formation of HFC-32. With concentrated reactants at high reaction temperatures, there was an increase in the catalytic activity; however, unwanted tar, methane, and trifluoromethane (HFC-23) by-products are also produced. The use of catalyst suppresses the formation of these by-products. Considering the compositions of the products of the catalytic and noncatalytic reactions, we demonstrate that the use of the supported-metal catalysts and hydrogen flow suppresses tar formation and lowers the required reaction temperature.
|Number of pages
|Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering
|Published - 2011 Jan
Bibliographical noteFunding Information:
The authors are grateful to the Korea Environmental Industry and Technology Institute for funding. The authors appreciate Professor Sang Heup Moon and Dr. Ara Cho (Seoul National University, Seoul, Republic of Korea) for the active site measurement of the catalysts.
Copyright 2012 Elsevier B.V., All rights reserved.
ASJC Scopus subject areas
- Environmental Engineering