噻吩及其衍生物裂化脱硫反应比较

采用半经验的AM1量子化学计算方法和静态理论，分别考察了噻吩、3-甲基噻吩和2,5-二甲基噻吩分子结构特性的不同，从偶极矩、各自垂直于芳香环平面的二维电势能分布曲线和整个分子周围三维电势能分布情况等方面分析了它们在分子筛催化剂表面吸附速度的快慢和生成正碳离子稳定性的高低，进一步比较了噻吩及其衍生物所生成的正碳离子进一步反应的能量变化，从而可判断噻吩及其衍生物裂化脱硫速度的快慢，噻吩及其衍生物裂化脱硫的速度由大到小分别为：2,5-二甲基噻吩、3-甲基噻吩、噻吩。这与在实验室固定床微反装置上以噻吩、3-甲基噻吩和2,5-二甲基噻吩为模型化合物进行实验所得到的结果是一致的。

COMPARISON BETWEEN THIOPHENE AND ITS DERIVATIVE IN DESULFURIZATION BY CATALYTIC CRACKING

The molecular conformations of thiophene, 3-methylthiophene and 2,5-bimethylthiophene were investigated by using the semi-empirical calculation AM1 method and the static theory. Their adsorption rate on the molecular sieve catalysts surface and the stability of their carbonium ions were then obtained based on the molecular simulation on these molecules from their dipole moment, 2-dimensional electrostatic potential energy contours and 3-dimensional electrostatic potential energy isosurface. Also the curves of total potential energies for the further reactions of the carbonium ions of thiophene, 3-methylthiophene and 2,5-bimethylthiophene were obtained by this way. This could be used as a criterion to determine which cracking desulfurization rate is faster than others among thiophene, 3-methylthiophene and 2,5-bimethylthiophene. The results showed that the fastest one is 2,5-bimethylthiophene,and secondly 3-methylthiophene. This was in good agreement with the experimental data obtained in a fixed bed micro-reactor for catalytic cracking of thiophene, 3-methylthiophene and 2,5-bimethylthiophene.