Effects of M-promoter (M = Y, Co, La, Zn) on Cr2O3 catalysts for fluorination of perchloroethylene

• Promoter M (M = Y, Co, La, Zn) can change the catalytic performance of Cr2O3 catalyst.
• La-Cr2O3(F) catalyst exhibited the highest activity and selectivity and it showed a good reaction stability.
• Surface acid sites density of M-Cr2O3 catalysts have a larger impact on the activity of the catalyst.

The vapor phase fluorination of perchloroethylene (PCE) to synthesize 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) and pentafluoroethane (HFC-125) was carried out on M-Cr2O3 catalysts with different promoters (M = Y, Co, La, Zn). The catalysts were characterized by X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), Raman spectrum, Ammonia temperature-programmed desorption (NH3-TPD) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that in the pre-fluorination process CrOx (x ≥ 1.5) in M-Cr2O3 catalysts could be transformed into CrOxFy species. The highest activity was obtained on La-Cr2O3(F) catalyst with 90.6% of PCE conversion and 93.7% to total selectivity (HCFC-123 + HCFC-124 + HFC-125) at 300 °C. The decline in surface acid sites density of the catalyst could improve the specific reaction rate, and the formation of surface CrOxFy species could enhance the selectivities to HCFC-123, HCFC-124 and HFC-125 for gas phase fluorination of PCE.

The conversion of PCE is 90.6% and selectivity to effective product is 93.7% at 300 °C over La-Cr2O3(F) catalyst.Figure optionsDownload as PowerPoint slide