Catalytic gas-phase fluorination of 1,1,2,3-tetrachloropropene to 2-chloro-3,3,3-trifluoropropene over the fluorinated Cr2O3-based catalysts

• The effects of reaction conditions on product distribution for gas-phase fluorination of 1,1,2,3-tetrachloropropene are investigated.
• The formation of HCFO-1233xf is discussed.
• The thermodynamics parameters of continuous fluorination reactions are calculated.
• The formed CrOxFy species are active sites for fluorination of 1,1,2,3-tetrachloropropene to HCFO-1233xf.

Gas-phase fluorination of 1,1,2,3-tetrachloropropene to 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) was investigated over the fluorinated Cr2O3 catalysts with and without promoters. The reaction conditions showed significantly effects on product distribution including temperature, molar ratio of reactants and contact time. The selectivity to HCFO-1233xf was favored under relative higher temperature, larger HF/1,1,2,3-tetrachloropropene ratio and shorter contact time. Based on the data of product distribution over the fluorinated Cr2O3 catalyst, a possible reaction path involving complicated consecutive steps was proposed including the addition/elimination and the direct Cl/F exchange. The XRD, XPS and Raman results indicated that introducing Mg, Ca and La onto Cr2O3 promoted the formation of highly dispersed CrOxFy species during the pre-fluorination process, whereas the presence of Y inhibited the formation of CrOxFy. The BET results showed that the addition of La and Y into Cr2O3 enhanced the surface area of fluorinated samples. The fluorinated Cr2O3 promoted by La (La/F-Cr2O3) catalyst displayed the best activity and lifetime among the prepared catalysts, which can be attributed to its rich CrOxFy species and high surface area.

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