Hydrodechlorination of CCl2FCClF2 over NiOCr2O3 catalysts

Abstract Among various metal oxides and mixed metal oxides, NiOCr 2 O 3 containing 70 atom.% of Cr(Cr-70) exhibited the highest catalytic activity for the vapor-phase hydrodechlorination of CCl 2 FCClF 2 shown as CCl 2 FCClF 2 + H 2 →CClF=CF 2 , CHF=CF 2 + HCl Furthermore, the catalytic activity was well maintained, and about 100% conversion was observed even after a long running time(5.25h). Whereas, the reaction was not promoted by Cr 2 O 3 , and CH 4 -formation and deactivation due to carbon deposition were remarkably promoted by NiO or NiOCr 2 O 3 composed of higher amount of NiO. The selectivity of the product was controlled by the reaction temperature. Thus, the molar ratio(CClF=CF 2 /CHF=CF 2 ) for the reaction promoted by Cr-70 was decreased from 78.2/4.1 to 52.1/27 with raising the reaction temperature from 350 to 450°C. The XRD pattern of Cr-70 was similar to that of Cr 2 O 3 , except for the presence of a faint or weak peak ascribable to Ni. Thus, the Ni component finely dispersed on Cr 2 O 3 , or NiCr 2 O 4 was considered to be active species for the reaction.