Effect of Fe promotion on the performance of V2O5/MgF2 catalysts for gas-phase dehydrofluorination of 1,1,1,3,3-pentafluoropropane
A series of 3V-xFe/MgF 2 catalysts with different V/Fe molar ratios were prepared by a sol-gel method, and the effect of Fe promotion on the catalytic performance of gas-phase dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) was investigated. It was found that proper V/Fe ratio was helpful to improve the activity. The 3V-0.5Fe/MgF 2 catalyst (with a V/Fe ratio of 6/1) gave a HFC-245fa conversion of 76.6% at 320 °C, which was 13.4% higher than that on the 3V/MgF 2 (63.2%). The synergy between V and Fe species resulted in enhanced surface acidity which accounts for the enhanced activity. The VO x and FeO x species in the fresh catalyst could be transformed to VOF x and FeF 3 species during the reaction, which were regarded as the active sites. However, higher content of Fe in the catalyst resulted in the partial coverage of V species, which led to decline of surface acidity and thus the suppressed activity. Also, surface carbon deposition was responsible for the slight catalyst deactivation .
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