文献类型：会议论文

英文题名：Structure sensitivity of ammonia decomposition over Ni catalysts: A computational and experimental study

作者：Duan, Xuezhi[1];Qian, Gang[1];Liu, Yan[1];Ji, Jian[1];Zhou, Xinggui[1];Chen, De[2];Yuan, Weikang[1]

机构：[1]E China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China;[2]Norwegian Univ Sci & Technol, Dept Chem Engn, N-7491 Trondheim, Norway

会议论文集：6th Asia Pacific Chemical Reaction Engineering Symposium (APCRE)

会议日期：SEP 18-21, 2011

会议地点：Beijing, PEOPLES R CHINA

语种：英文

外文关键词：Ammonia decomposition; Ni catalysts; Density functional theory; Ni step-blocking; Structure sensitivity

摘要：Ni catalysts are widely used to catalyze ammonia decomposition. In this study, first-principles calculations are performed to investigate the preferred adsorption sites and the adsorption energies of NHx (x=0-3) and H, and the transition states, activation energies and rate constants of NH3 stepwise dehydrogenation and associative desorption of N on the stepped Ni(211) and the close-packed Ni(111) surfaces. The results show that the barrier of associative desorption of N, which is higher than those of NH3 stepwise dehydrogenation, on Ni(211) are 1.10 eV higher than that on Ni(111), indicating that the associative desorption of N on Ni(211) is difficult to take place. Hence the strongly adsorbed N atoms would block some of the step sites of Ni(211). The N-blocking Ni(211) surface is constructed, and then NH3 decomposition on 2N-Ni(211) is investigated. The results indicate that Ni catalysts with too many or too few step sites, which can be associated with Ni particle sizes, show low ammonia decomposition activities. Therefore, different sized Ni-based catalysts are employed to catalyze ammonia decomposition, and TOFH2 as a function of Ni particle size is correlated. Finally, the structure sensitivity of ammonia decomposition over Ni catalysts is rationally interpreted. (C) 2012 Elsevier B.V. All rights reserved.