Effects of yttrium-doping on the performance of Cr2O3 catalysts for vapor phase fluorination of 1,1,2,3-tetrachloropropene

The synthesis of 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) from 1,1,2,3-tetrachloropropene was performed over a series of Y2O3-Cr2O3(F) catalysts and the effect of yttrium-doping on the performance of Cr2O3 catalysts was investigated. Various characterization results showed that the addition of yttrium in the Cr2O3 led to the formation of high valent Cr species in the samples, which could be consequently converted to catalytically active CrOxFy species during the pre-fluorination process. Although the Cr2O3 catalyst with or without yttrium-doping showed very high 1,1,2,3-tetrachloropropene conversion in long term reaction, the addition of yttrium in the Cr2O3 helped to maintain the high selectivity to HCFC-1233xf, with the highest selectivity (97%) obtained on a 1 mol% yttrium-doped Cr2O3 after 100 h reaction. X-ray photon spectroscopy results on the spent Cr2O3(F) and 1Y2O3-Cr2O3(F) catalysts indicated that the content of the active CrOxFy species declined after 70 h reaction, which was responsible for the loss of selectivity (from 97% to 88%), while it remained almost unchanged on the spent 1Y2O3-Cr2O3(F) catalyst.