To study the substituent effects of 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) on the direct hydrodesulfurization (DDS) routes catalyzed on a Ni-Mo-S nanocluster, a non-periodic computational Ni-Mo-S model is established, and density functional theory (DFT) is used to comparatively calculate the adsorption and the conversion of the dibenzothiophene (DBT) and 4,6-DMDBT on the Ni-S-edge, Ni-Mo-edge and corner sites of the Ni-Mo-S active nanocluster. The calculation results show that on the Ni-Mo-S active nanocluster, the Ni-S-edge could stably provide active hydrogen, whereas the CS bond cleavage on this active site required higher activation energy. The Ni-Mo-edge could not stably provide active hydrogen, and this active site has the highest activity of CS bond cleavage. The corner site shows favorable ability of hydrogen activation and CS bond cleavage. The methyl group of 4,6-DMDBT weakens the NiS bonds caused by the adsorption on the Ni-S-edge, where the decrease of the adsorption energy is compensated by an additional dispersion provided by two methyl groups. The two methyl groups also decrease the adsorption angle between the 4,6-DMDBT and the CUS sites on the Ni-Mo-edge and corner sites. The flat adsorption of 4,6-DMDBT will further hinder the hydrogen activation and transfer on the Ni-Mo-edge. Moreover, the methyl group of 4,6-DMDBT decreases the energy difference between the reactant and the intermediate of the DDS route, increasing the reaction energy of the CS bond cleavage. The dominant DDS route of the DBT and 4,6-DMDBT involves the interaction between active hydrogen and the α-C followed by the movement of the newly formed aromatic ring away from the S atom of the sulfur compounds. During this process, the methyl groups of the 4,6-DMDBT will hinder the CS bond cleavage on all CUS sites on the Ni-S-edge, Ni-Mo-edge and corner sites of the Ni-Mo-S nanocluster. Therefore, the activation energy of the CS bond cleavage of 4,6-DMDBT is higher than that of DBT, and this is the main reason for the lower DDS rate of the former compared to the latter.

为了研究4,6-二甲基-二苯并噻吩（4,6-DMDBT）在Ni-Mo-S纳米团簇上催化的直接加氢脱硫（DDS）路线上的取代基效应，采用非周期性计算的Ni-Mo-S模型建立并使用密度泛函理论（DFT）来比较计算二苯并噻吩（DBT）和4,6-DMDBT在Ni-S边缘，Ni-Mo边缘和Ni拐角部位的吸附和转化-Mo-S活性纳米簇。计算结果表明，在Ni-Mo-S活性纳米簇上，Ni-S-edge可以稳定地提供活性氢，而在该活性位点上的C S键断裂需要更高的活化能。Ni-Mo-edge无法稳定地提供活性氢，并且该活性位点具有最高的C活性S键裂解。拐角部位显示出有利的氢活化和CS键裂解的能力。4,6-DMDBT的甲基弱化了由于在Ni-S边缘上的吸附而引起的Ni S键，其中吸附能的下降被两个甲基提供的额外分散所补偿。两个甲基还降低了4,6-DMDBT与Ni-Mo边缘和拐角部位CUS部位之间的吸附角。4,6-DMDBT的平整吸附将进一步阻碍氢的活化和在Ni-Mo边缘的转移。此外，4,6-DMDBT的甲基减少了反应物与DDS路线中间体之间的能量差，从而增加了C的反应能。S键裂解。DBT和4,6-DMDBT的主要DDS路线涉及活性氢与α-C之间的相互作用，然后是新形成的芳环从硫化合物的S原子移开。在此过程中，4,6-DMDBT的甲基将阻碍在Ni-Mo-S纳米簇的Ni-S边缘，Ni-Mo边缘和角落位置的所有CUS位点上的C S键断裂。因此，4,6-DMDBT的C S键断裂的活化能比DBT高，这是前者的DDS速率比后者低的主要原因。