Selective Dehydrofluorination of 1,1,1,3,3‐Pentafluoropropane to Synthesize Tetrafluoropropylene and Trifluoropropyne over the ZnO/Cr₂O₃ Catalysts

Abstract

A series of ZnO/Cr 2 O 3 catalysts were prepared by an impregnation method, and the promoted role of ZnO on the activity for selective dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF 3 CH 2 CHF 2) to tetrafluoropropylene (CFH=CHCF 3 and CH 2 =CFCF 3) and 3,3,3-trifluoropropyne (CH�CCF 3) was investigated. The ZnO/Cr 2 O 3 catalysts were characterized by XRD, Raman, BET, NH 3-TPD and XPS. As more Zn was loaded, both the crystallite size of the Cr 2 O 3 and the surface area of catalysts both increased. The surface acidity of catalysts was the highest (1.02 μmol g À 1) when 2 mol % of ZnO was added. Surface Cr species on the surface of ZnO/Cr 2 O 3 catalysts were identified, including Cr 2 O 3 , Cr(OH) 3 and CrO 3. As the ZnO content increased, the relative content of Cr 2 O 3 elevated, while the relative contents of Cr(OH) 3 and CrO 3 decreased. It was found that the selectivities to four products (EÀ CFH=CHCF 3 , Z-CFH=CHCF 3 , CH 2 =CFCF 3 and CH�CCF 3) were greatly affected by the ZnO loading and reaction temperature. For the 2ZnO/Cr 2 O 3 catalyst, the lowest selectivities to E-and Z-CFH=CHCF 3 were 61.2 and 15.7 %, respectively, while CH 2 =CFCF 3 and CH�CCF 3 achieved the highest selectivity (11.7 % and 9.8 %, respectively) at 450°C due to the highest surface acidity.