D-山梨醇醚化过程的热力学计算与分析

Thermodynamic calculation and analysis of the etherification process of D-sorbitol

D-山梨醇在酸催化下会发生醚化反应,生成失水山梨醇的混合物。为便于了解各反应特性,采用Benson法、Myrdal-Krzyzaniak-Yalkowsky法、Joback法等基团贡献法和Marrero-Pardillo键贡献法估算了D-山梨醇醚化反应中所涉及物质的标准摩尔生成焓、标准摩尔熵和摩尔定压热容等热力学参数。并根据估算数据计算了不同温度下各反应的标准摩尔反应焓变、标准摩尔反应Gibbs自由能变和平衡常数。计算结果表明:D-山梨醇醚化过程中,各个反应均为吸热反应,升高温度有利于醚化反应进行,标准摩尔反应Gibbs自由能变均小于0,反应为自发过程,反应能正向完全进行。产物中1,4-失水山梨醇的平衡常数较大,会进一步生成异山梨醇。这些数据为失水山梨醇的高效制备提供理论参考。

D-sorbitol undergoes etherification reaction under the catalysis of acid to form a mixture of dehydrated sorbitol.For the convenience of understanding the characteristics of each reaction,group contribution methods such as Benson method,Myrdal-Krzyzaniak-Yalkowsky method,Joback method and Marrero-Pardillo bond contribution method were used to estimate the thermodynamic parameters such as standard molar enthalpy of formation,standard molar entropy and molar constant pressure heat capacity of the substances involved in the D-sorbitol etherification reaction.The standard molar reaction enthalpy change,standard molar reaction Gibbs free energy change and equilibrium constant of each reaction were calculated at different temperatures.The calculation results indicate that all reactions during the etherification process of D-sorbitol are endothermic and it is beneficial for the etherification reaction when the temperature increased.The Gibbs free energy change of the standard molar reaction is all less than zero,indicating that the reaction is spontaneous and can proceed completely in a forward direction.The equilibrium constant of 1,4-sorbitan in the product is relatively large,which further leads to the formation of isosorbide.These datas provide theoretical reference for the efficient preparation of sorbitans.