Effect of the size of Cu clusters on selectivity and activity of acetylene selective hydrogenation

• Published in: Applied catalysis. A, General General, 2017-09, Vol.546, p.111-121
• Main Authors: Zhao, Bo, Zhang, Riguang, Huang, Zaixing, Wang, Baojun
• Format: Article
• Language: English
• Subjects: Acetylene; Activity; Catalysis; Catalysts; Clusters; Copper; Copper cluster; Density functional theory; Ethane; Hydrogenation; Selectivity; Size effect; Size effects
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2017.08.001

[Display omitted] •Cu13, Cu38, Cu55 clusters and Cu(111) surface are used to model different sizes of Cu cluster.•The preferable path of C2H2 selective hydrogenation depends on the size of Cu catalyst.•The larger the Cu cluster size is, the higher the selectivity of C2H4 is.•Beginning with Cu55 cluster, Cu cluster size is beneficial to form C2H4.•The activity of C2H4 formation is related to the d-band center of Cu catalysts. In order to probe into the size effect of Cu catalyst on the selectivity and activity of ethylene formation in acetylene selective hydrogenation, different sizes of Cu catalysts including Cu13, Cu38, Cu55 clusters and the periodic Cu(111) surface have been employed to systematically investigate the selective hydrogenation of C2H2 using density functional theory calculations. The results show that the adsorption ability of C2H2 is stronger than that of C2H4 on different sizes of Cu catalysts, which is in favor of C2H2 activation and hydrogenation. On Cu13 and Cu38 clusters, C2H2 easily undergoes over-hydrogenation to form ethane via CHCH2 and CHCH3 intermediates, namely, both clusters exhibit a poor selectivity towards C2H4 formation. However, on Cu55 cluster, C2H2 is easily hydrogenated to form C2H4via CHCH2 intermediate, and C2H4 prefers desorption over its hydrogenation, suggesting that Cu55 cluster exhibits a good selectivity towards C2H4 formation. Further, the periodic Cu(111) surface regarded as the large Cu particle sizes has the same results with Cu55 cluster. Therefore, among different sizes of Cu cluster, the size of Cu cluster affects the preferred pathway of C2H2 selective hydrogenation, and alters the selectivity towards C2H4 formation; moreover, beginning with Cu55 cluster, Cu cluster is beneficial to C2H2 hydrogenation to C2H4. The activity of C2H4 formation follows the order of Cu(111) > Cu38> Cu55 >> Cu13, which corresponds to the d-band center of these catalysts. The identifications about the relationship of the intrinsic selectivity and activity with cluster size effect would provide a clue for designing highly-efficient Cu-based catalysts in C2H2 hydrogenation to C2H4.