Mechanistic Insights into Ethylene Transformations on Ir(111) by Density Functional Calculations and Microkinetic Modeling

Xue-Rong Shi; Haijuan Kong; Shengguang Wang; Hui Wang; Zhangfeng Qin; Jianguo Wang

doi:10.1002/cphc.201700051

Mechanistic Insights into Ethylene Transformations on Ir(111) by Density Functional Calculations and Microkinetic Modeling

Chemphyschem. 2017 Apr 19;18(8):906-916. doi: 10.1002/cphc.201700051. Epub 2017 Mar 1.

Authors

Xue-Rong Shi^{1

2}, Haijuan Kong¹, Shengguang Wang³, Hui Wang⁴, Zhangfeng Qin⁵, Jianguo Wang⁵

Affiliations

¹ College of Materials Engineering, Shanghai University of Engineering Science, Shanghai, 201620, P.R. China.
² Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, Innsbruck, Austria.
³ Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204-4004, USA.
⁴ Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, P.R. China.
⁵ State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi, 030001, P. R. China.

PMID: 28195415
DOI: 10.1002/cphc.201700051

Abstract

Ethylidyne, ethane, and carbon monomer formations from ethylene over Ir(111) at different coverages are investigated using density functional theory methods. Two possible reaction mechanisms for ethylidyne formation are investigated. The calculations show that vinyl prefers the dehydrogenation to yield vinylidene (M2) over the hydrogenation to produce ethylidene (M1) kinetically and thermodynamically at 1/9 (1/3) ML. Ethylidyne formation could be a competitive side reaction of ethylene hydrogenation, however, the ethylidyne species does not directly participate in the ethylene hydrogenation mechanism. The mechanism for C monomer formation is also studied. Microkinetic modeling shows that the ethylene hydrogenation reactivity decreases in the sequence Ir(111)>Rh(111)>Pd(111)>Pt(111) under typical hydrogenation conditions. The catalytic activity of ethylene hydrogenation decreases with increased stability of ethylene adsorption and reaction barrier of the rate-limiting step.

Keywords: Ir(111); carbon monomers; density functional theory; ethylene; microkinetic modeling.