High-temperature hydrodechlorination of ozone-depleting chlorodifluoromethane (HCFC-22) on supported Pd and Ni catalysts
- High-temperature hydrodechlorination of ozone-depleting chlorodifluoromethane (HCFC-22) on supported Pd and Ni catalysts
- 하정명; 김대우; 김재훈; 안병성; 김연제; 강정원
- catalyst; HFC-32; HCFC-22; refrigerant; hydrogenolysis; Pd; Ni; hydrodechlorination; HFC-23; catalysis
- Issue Date
- Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering
- VOL 46, NO 9, 989-996
- 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 gasphase
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.
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