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Fluorinated Pd/Al2O3 촉매를 이용한 CFC-12의 탈염소수소화 반응
Hydrodechlorination of CFC-12 over Fluorinated Pd/Al2O3 Catalyst
HWAHAK KONGHAK, February 1999, 37(1), 103-107(5), NONE
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Abstract
본 연구에서는 HCFC-22(CHF2Cl)로 전처리하여 불화시킨 Pd/Al2O3, 촉매를 사용하여 CFC-12(CF2Cl2)의 탈염소수소화반응을 수행하였다. 수소로 전처리하여 환원시킨 촉매와 반응활성 및 HFC-32(CH2F2)로의 선택도를 비교 검토하고, BET, XRD, TEM등의 분석기기를 사용하여 반응전후 촉매의 특성을 분석하였다. 불화과정을 거친 촉매가 통상적인 환원과정을 거친 촉매보다 활성 및 선택도에서 우수한 성능을 보였으며 비활성화의 원인인 Pd의 소결을 방지하는 효과도 확인하였다. 불화과정에서 Al2O3가 AlF3로 변화하며 Pd-F결합을 형성하여 Pd촉매의 소결을 방지하는 역할을 하는 것으로 추측되지만 본 연구의 실험조건에서는 Pd-F결합을 확인하지 못하였다. 또한 불화과정에서 Pd carbide 생성을 확인하였으며 Pd carbide가 CFC-12의 Cl만을 선택적으로 환원시켜 반응의 선택도를 높이는 것으로 판단된다.
The hydrodechlorination of CFC-12(CF2Cl2) has been studied with Pd/Al2O3 catalysts. The catalysts were fluorinated by HCFC-22(CHF2Cl) or reduced by hydrogen before the reaction. And they were characterized by BET, XRD, and TEM before and after the reaction. The activities and selectivities to HFC-32(CH2F2) were compared in the fluorinated and the reduced catalysts. The fluorinated catalyst has shown better performance in activity and selectivity rather than the conventional reduced one, as well as in prevention of Pd sintering which causes deactivation of the catalyst. It is presumed that formation of Pd-F bond in the fluorination prevents sintering of Pd while the formation of AlF3 from Al2O3. Also, Pd carbide was observed in the fluorinated catalyst and this carbide is thought to enhance the partial dehalogenation(dechlorination) in CFC-12.
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