利用密度泛函理论研究了γ-Mo2N(100)表面上的噻吩加氢脱硫(HDS)过程.噻吩在γ-Mo2N(100)表面上不同作用形式的结构优化结果显示,η5-Mo2N吸附构型最稳定,具有最大的吸附能(-0.56 eV),此时噻吩通过S原子与Mo2原子相连平行表面吸附在四重空位(hcp位). H原子和噻吩在hcp位发生稳定共吸附, hcp位是噻吩HDS的活性位点.噻吩在γ-Mo2N(100)表面进行直接脱硫反应, HDS过程分为S原子脱除和C4产物加氢饱和两部分.过渡态搜索确定了HDS最可能的反应机理及中间产物,首个H原子的反应需要最大的活化能(1.69 eV),是噻吩加氢脱硫的控速步骤.伴随H原子的不断加入,噻吩在γ-Mo2N(100)表面上优先生成―SH和丁二烯,随后―SH加氢生成H2S,丁二烯加氢饱和生成2-丁烯和丁烷.由于较弱的吸附, H2S、2-丁烯和丁烷很容易在γ-Mo2N(100)表面脱附成为产物.%The hydrodesulfurization (HDS) of thiophene on anγ-Mo2N(100) surface was investigated by density functional theory (DFT) and different configurations of thiophene onγ-Mo2N(100) surface were considered. After geometric optimization, it was confirmed that theη5-Mo2N configuration was the most stable adsorption model with an adsorption energy of-0.56 eV, where thiophene absorbed on 4-fold hcp vacant sites paral el to the surface with the S atom bonded to a Mo2 atom. The stable coadsorption of H atoms and thiophene on hcp sites showed that the hcp site is the active site for thiophene HDS onγ-Mo2N(100). A direct desulfurization reaction pathway in HDS of thiophene dominated the process on theγ-Mo2N(100) surface, which could be divided into the removal of the S atom and the hydrogenation saturation of C4 species. To identify the intermediate products and the most probable reaction mechanism of thiophene HDS, a transition state search was carried out. The results indicated that the reaction of the first H atom required an activation energy of 1.69 eV, which was the rate-determining step in the HDS of thiophene. The thiol group (―SH) and butadiene were preferential y formed after hydrogenation of thiophene, and―SH detached from mercaptan was the intermediate of H2S. 2-Butene and butane were the products of the hydrogenation saturation of butadiene. H2S, 2-butene, and butane were easily desorbed fromγ-Mo2N(100) to give the products because of weak adsorption.
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