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镍掺杂对Fe催化剂上CO_2加氢制烃影响的理论计算研究
引用本文:梁志铭,聂小娃,郭新闻,宋春山.镍掺杂对Fe催化剂上CO_2加氢制烃影响的理论计算研究[J].分子催化,2020,34(4):293-303.
作者姓名:梁志铭  聂小娃  郭新闻  宋春山
作者单位:大连理工大学,大连理工大学,大连理工大学,美国宾州州立大学
摘    要:为研究镍掺杂对铁基催化剂上二氧化碳加氢生成C_1和C_2烃类产物的影响,应用密度泛函理论进行了相关计算.在Fe(110)和Ni-Fe(110)表面上, CH~*物种是最有利的生成CH_4和C_2H_4的C_1物种(CH_x~*),其最可能的生成路径为CO_2→HCOO~*→HCO~*→CH~*.尽管CO_2直接解离为CO~*在动力学上相较于加氢生成HCOO~*和COOH~*是较为有利的,但CO~*进一步加氢生成HCO~*在能量上是不利的,其倾向于逆向解离回到CO~*. CH~*物种可以通过三步加氢反应生成CH_4或者经C—C耦合及两步加氢生成C_2H_4.在Fe(110)表面上,对甲烷和乙烯产物选择性起决定作用的基元反应能垒之间差异仅为0.10 eV,因此两者选择性相近.在将Ni原子引入Fe(110)表面后,生成甲烷与乙烯的选择性差异变大,导致乙烯的选择性提高.计算结果表明,添加少量金属Ni能够促进CO_2转化为CH~*,及两个CH~*物种发生C—C耦合和进一步加氢转化为乙烯.

关 键 词:二氧化碳加氢  烃类  Ni-Fe双金属催化剂  密度泛函理论    反应机理
收稿时间:2020/6/22 0:00:00
修稿时间:2020/7/2 0:00:00

DFT Insight into the Effect of Ni Doping on Hydrocarbons Synthesis from CO2 Hydrogenation over Fe Catalyst
LIANG Zhi-ming,NIE Xiao-w,GUO Xin-wen and SONG Chun-shan.DFT Insight into the Effect of Ni Doping on Hydrocarbons Synthesis from CO2 Hydrogenation over Fe Catalyst[J].Journal of Molecular Catalysis (China),2020,34(4):293-303.
Authors:LIANG Zhi-ming  NIE Xiao-w  GUO Xin-wen and SONG Chun-shan
Institution:Dalian University of Technology,Dalian University of Technology,Dalian University of Technology,The Pennsylvania State University
Abstract:Density functional theory (DFT) calculations were performed to investigate the effect of Ni doping on C1 and C2 hydrocarbons production from CO2 hydrogenation on the Fe catalyst. The CH* species was found to be the most favorable monomeric CHx* species leading to both CH4 and C2H4 formation on Fe(110) and Ni-Fe(110) surfaces. The plausible pathway went through CO2-->HCOO*-->HCO*-->CH*. Although CO* formation from direct dissociation of CO2 was kinetically more favorable than CO2 hydrogenation to HCOO* and COOH* intermediates on the two surfaces, the subsequent hydrogenation of CO* to HCO* was energetically detrimental, resulting in the reverse conversion of HCO* to CO* preferred. Further conversion of CH* species led to either CH4 via several hydrogenation steps or C2H4 through C-C coupling followed by two hydrogenation steps. On monometallic Fe(110), the barrier difference associated with the selectivity determining step was only 0.10 eV, suggesting similar selectivity to CH4 and C2H4. In contrast, when a Ni atom was doped onto Fe(110), the selectivity difference became more pronounced, leading to an enhanced C2H4 production on Ni-Fe(110). These results revealed that adding a small amount of Ni could promote CH* formation from CO2 hydrogenation, C-C coupling of two CH* species and the further hydrogenation of C2 intermediates to ethylene.
Keywords:CO2 hydrogenation  Hydrocarbons  Ni-Fe bimetallic catalysis  Density functional theory  reaction mechanism
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