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采用沉淀法和浸渍法制备了2种铬基(Cr_2O_3和CrO_3/Cr_2O_3)催化剂,用于气相氟化2-氯-1,1,1-三氟乙烷合成1,1,1,2-四氟乙烷。研究发现含有低价铬(Cr3+)物种的Cr_2O_3催化剂上2-氯-1,1,1-三氟乙烷的稳态转化率为18.5%,而含有高价铬(Cr6+)物种和低价铬(Cr3+)物种的CrO_3/Cr_2O_3催化剂初始转化率达到30.6%,然而存在明显的失活。含有Cr6+物种的CrO_3/Cr_2O_3催化剂的2-氯-1,1,1-三氟乙烷氟化反应初始TOF值为1.71×10-4 molHCFC-133a·molCr髩-1·s-1,高于含有Cr3+物种的Cr_2O_3催化剂(4.16×10-5 molHCFC-133a·molCr髥-1·s-1)。Cr_2O_3催化剂在氟化反应前后催化剂的物相结构保持不变;而含有高价铬物种的CrO_3/Cr_2O_3催化剂经HF反应后生成了CrO_xF_y活性物种。然而,CrO_xF_y物种在反应中挥发或转化成稳定但无活性的CrF_3,从而导致催化剂失活。
Two kinds of chromium-based (Cr_2O_3 and CrO_3 / Cr_2O_3) catalysts were prepared by precipitation and impregnation method for gas phase fluorination of 2-chloro-1,1,1-trifluoroethane to synthesize 1,1,1,2-tetra Fluoroethane. It was found that the steady state conversion of 2-chloro-1,1,1-trifluoroethane was 18.5% on Cr 2 O 3 catalyst containing Cr (Ⅵ) and Cr (Ⅵ) The initial conversion of CrO_3 / Cr_2O_3 catalyst reached 30.6% for Cr3 + species, however, there was obvious deactivation. The initial TOF value of CrO 3 / Cr 2 O 3 catalyst containing Cr 6 + species was 1.71 × 10-4 mol HCFC-133a · molCr 髩 -1 · s-1, higher than Cr_2O_3 catalyst containing Cr3 + species (4.16 × 10-5 mol HCFC-133a · molCr · -1 · s-1). The phase structure of Cr_2O_3 catalyst remained the same before and after the fluorination reaction. However, the CrO_3 / Cr_2O_3 catalyst containing high-valent chromium species produced the CrO_xF_y active species by HF reaction. However, CrO_xF_y species volatilize or convert to stable but inactive CrF_3 during the reaction, resulting in catalyst deactivation.