蔗糖-6-乙酸酯氯化过程热力学及动力学研究

Thermodynamic Analysis and Kinetic Study on the Sucrose-6-Acetate Chlorination Process

蔗糖-6-乙酸酯(S-6-A)氯化制备三氯蔗糖-6-乙酸酯(TGS-6-A)是合成三氯蔗糖(TGS)的关键步骤。采用基团贡献法对氯化反应进行热力学计算,结果表明,在372~389 K的温度范围内,该反应为放热且不可逆反应;同时对目标产物TGS-6-A的水解反应进行了热力学计算,获得了不同温度下的平衡常数计算值,与平衡常数实验值的对比进一步验证了该计算方法的可靠性;通过间歇实验研究了温度对反应速率的影响,建立了氯化连串反应动力学模型。在所研究温度范围内,主反应生成二氯蔗糖-6-乙酸酯和目标产物TGS-6-A的活化能分别为103.87 kJ/mol、153.87 kJ/mol;副反应生成四氯蔗糖-6-乙酸酯的活化能为87.09 kJ/mol。动力学实验结果表明主反应受温度的影响更大,升高温度并且控制反应时间能有效提高目标产物TGS-6-A的收率。

The chlorination of sucrose-6-acetates(S-6-A)to produce sucralose-6-acetate(TGS-6-A)is a key step in the synthesis of sucralose.In this work,a thermodynamic calculation of the chlorination reaction was carried out using the group contribution method.The results show that the reaction is exothermic and irreversible in the temperature range of 372 K to 389 K.The thermodynamic calculations were performed on the hydrolysis reaction of TGS-6-A.The equilibrium constants at different temperatures obtained agree well with the experimental values,confirming the reliability of the calculation methods used in this work.Then,the effect of temperature on reaction rate was studied by batch experiments,and a chain reaction kinetic model of chlorination reaction was established.The activation energies of the main reactions producing Dichlorosucrose-6-acetic acid ester and TGS-6-A were determined to be 103.87 kJ/mol and 153.87 kJ/mol,respectively,and the activation energy of the side reaction 87.09 kJ/mol.A kinetic study suggests that the main reaction is dependent on reaction temperature,and increasing the temperature and controlling the reaction time can effectively improve the yield of the target product,TGS-6-A.