DFT Study on the Dibenzothiophene Pyrolysis Mechanism in Petroleum
DFT Study on the Dibenzothiophene Pyrolysis Mechanism in Petroleum
复制标题
石油中二苯并噻吩热解机理的DFT研究
DOI：
10.1021/acs.energyfuels.9b01498
复制
发表时间：
2019-09-01
期刊：
影响因子：
5.3
通讯作者：
Xiao, Jin
中科院分区：
文献类型：
--
作者：
Li, Tianshuang;Li, Jie;Xiao, Jin
二苯并噻吩硫（DBT）是石油中最稳定的含硫物质，在石油中的含量非常高. DBT的去除对环境保护具有重要意义。采用密度泛函理论方法研究了DBT的热解机理。发现DBT的热解可能是由氢迁移或S-C键断裂引发的。发现了三条主要的反应途径，其中硫醇中间体裂解和DBT卡宾直接裂解是两条主要的裂解途径。主要产物为不含硫原子的2-乙炔基苯并噻吩、3-乙炔基苯并噻吩、乙炔、联苯和1，8-二氢环戊二烯，并含有一定量的苯并噻吩和SH自由基。对于DBT、BT和噻吩，最困难的步骤是初始步骤。DBT的最高能垒比BT和噻吩高约17 kcal/mol，表明DBT的热解需要更强烈的反应条件。噻吩在极端条件下是稳定的，这可能是由于初始反应步骤的高能量势垒造成的。在初始反应步骤之后，BT和DBT可以更容易地通过硫醇中间体脱硫。寻找能降低起始反应能垒的催化剂和能将噻吩直接转化为硫醇的试剂是噻吩脱硫的一条潜在途径。
Dibenzothiophene sulfur (DBTs), the most stable sulfur species, is present in remarkable concentration in petroleum. Removal of DBTs is with profound significance in environmental protection. In this work, a density functional theory method was adopted to investigate the pyrolysis mechanism of DBT. It was found that the pyrolysis of DBT is possibly started by H-migration or S-C bond rupture. Three main reaction pathways were found. Two dominating pyrolysis pathways are through thiol intermediate pyrolysis and another is through DBT carbene direct dissociation. The dominating products are sulfur-free atoms, 2-ethynyl-benzothiophene, 3-ethynyl-benzothiophene, ethyne, biphenylene, and 1,8-dihydrocyclopentaindene, with a certain amount of benzothiophene and SH radicals. For DBT, BT, and thiophene, the most difficult step is the initial step. The highest energy barrier of DBT is about 17 kcal/mol higher than BT and thiophene, indicating that pyrolysis of DBT needs more intense reaction conditions. Thiophenes can be stable in extreme conditions, which is possibly caused by the high energy barrier of the initial reaction step. After the initial reaction steps, BT and DBT can be desulfurized more easily through thiol intermediates. Searching the catalyst that could lower the energy barrier of the initial step and the reagent that could convert thiophenes directly into thiols may be a potential desulfurization approach for thiophenes.