CrOx-Y2O3催化剂中Cr物种对氟氯交换反应性能的影响

用沉积-沉淀法制备了CrOx-Y2O3催化剂, 考察焙烧气氛及温度对1,1,1-三氟-2-氯乙烷(HCFC-133a)气相氟化合成1,1,1,2-四氟乙烷(HFC-134a)催化性能的影响. 采用拉曼光谱、X射线粉末衍射(XRD)等表征手段观察了催化剂中铬物种价态的变化情况. 结果表明, 先氮气后空气中不同温度(T)焙烧的催化剂(NAT), 随着空气中焙烧温度的升高, Cr物种由CrO3向YCrO4、YCrO3转变. 500 ℃焙烧的NA500催化剂虽然活性低于直接在空气中350 ℃焙烧的催化剂(A350), 然而前者的反应稳定性明显高于后者. 这归因于YCrO4物种在氟化过程中生成的活性物种既不易流失并且表面不容易结炭.

Effect of Cr Species in CrOx-Y2O3 Catalyst on Chlorine/Fluorine Exchange Reactions

CrOx-Y2O3 catalystswere prepared by a deposition-precipitationmethod and tested by fluorinating 2-chloro-1,1,1-trifleuoroethane (HCFC-133a) to synthesize 1,1,1,2-tetrafluoroethane (HFC-134a). Using Raman spectrum and X-ray powder diffraction (XRD) technique, we found that the atmosphere and the temperature during the calcination process greatly influenced the CrOx species in the catalysts. When the catalyst was calcined in nitrogen and then in air at different temperatures (T) (NAT), the Cr species changed fromCrO3 to YCrO4 and YCrO3 with increasing calcination temperature. The NA500 catalyst showed better stability than the catalyst calcined in air at 350 ℃ (the A350 catalyst), because the YCrO4 species formed during calcination could transform into an active species during the pre-fluorination process and the coke deposition was inhibited on the catalyst surface during the reaction.