论文部分内容阅读
利用周期性密度泛函理论研究了SAPO-34分子筛催化转化卤代甲烷制取低碳烯烃反应的碳池主要成分多甲基苯分子的偕甲基化反应.氯甲烷和溴甲烷分子在SAPO-34分子筛内的吸附能分别是–18和–22 kJ/mol,由于氯和溴原子相似的电负性,氯甲烷和溴甲烷分子的吸附能并未被精确区分.以氯甲烷和溴甲烷为甲基化试剂,得到了几种多甲基苯分子的偕甲基化反应能及能垒,结果表明,六甲基苯分子(HMB)的偕甲基化反应为放热反应,而其余甲基苯分子的偕甲基化反应为吸热反应.对于上述两种甲基化试剂,体积最大的HMB均表现出最低的偕甲基化反应能垒,这可能是由于分子筛骨架与多甲基苯分子之间的静电相互作用增强了HMB的反应活性所致.
The cyclodemethylation of polymethylbenzene, the main component of the carbon pool, catalyzed by SAPO-34 molecular sieve for the conversion of methyl halide to light olefins was studied by periodic density functional theory The adsorption energies in the molecular sieve are -18 and -22 kJ / mol, respectively, and the adsorption energies of methyl chloride and methyl bromide molecules are not precisely distinguished due to the similar electronegativity of chlorine and bromine atoms. Methyl chloride and methyl bromide are methylated The results showed that the geminal methylation of hexamethylbenzene (HMB) was an exothermic reaction, while the rest of the methylbenzene molecules Was the endothermic reaction.For both of the above two methylating agents, the largest volume of HMB showed the lowest energy base for the geminisomethylation reaction, which may be due to the molecular sieve skeleton and polymethylbenzene molecules Electrostatic interaction between the enhanced HMB reactivity caused.