2-氯-1,1,1,2-四氟丙烷脱氯化氢合成2,3,3,3-四氟丙烯的热力学分析

摘要

采用密度泛函理论(DFT)方法,在B3LYP/6-311++G(d,p)水平下估算了2-氯-1,1,1,2-四氟丙烷(HCFC-244bb)气相脱氯化氢合成2,3,3,3-四氟丙烯(HFO-1234yf)反应体系中部分物质的标准生成焓△fH(-)m、标准生成吉布斯自由能△fG(-)m和等压热容Cp.m,计算了不同温度下各独立反应的反应热△rH(-)m、吉布斯自由能变△rG(-)m和平衡常数In K,考察了温度、压力和原料摩尔比对反应化学平衡的影响.结果表明:HCFC-244bb脱HC1合成HFO-1234yf的反应为吸热反应,△rG(-)m随着温度的增加而减小；高温、低压、高原料摩尔比有利于HFO-1234yf的生成.%The method of density functional theory (DFT) at B3LYP/6-311++G(d,p) level was employed to estimate the standard enthalpy of formation △fH(-)m,the standard Gibbs free energy of formation △fG(-)m,and the isobaric heat capacity Cp,m of some compounds during the synthesis of 2,3,3,3-tetrafluoropropene (HFO-1234yf)by vapor-phase dehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb).The heat of reaction △rH(-)m,the change of Gibbs free energy △rG(-)m and equilibrium constant InK respectively as the function of temperature for each independent reaction were calculated.The effects of temperature,pressure and the molar ratio of feed on the chemical equilibrium of reaction were analyzed.The results show that the synthesis of HFO-1234yf by dehydrochlorination of HCFC-244bb is an endothermic reaction,and the △fG(-)m reduces with the increase of reaction temperature.High temperature,low pressure and the addition of HF and HFC-245cb to feed material are favorable for the formation of HFO-1234yf.