Effect of transition metals (Cr, Mn, Fe, Co, Ni, Cu and Zn) on the hydrogenation properties of benzene over Ru-based catalyst

Authors: Hai-Jie Sun, Ya-Jie Pan, Hou-Bing Jiang, Shuai-Hui Li, Yuan-Xin Zhang, Shou-Chang Liu, Zhong-Yi Liu

Abstract:
The influence of transition metals on the hydrogenation properties of benzene over Ru-based catalysts had been investigated in the presence of ZnSO₄ acting as the reaction modifier. It was found that the (Zn(OH)₂)₃(ZnSO₄)(H₂O)_x salt (x = 1 or 3) chemisorbed on Ru surface played a key role in improving the selectivity of Ru catalysts to cyclohexene. The promoter Cr in Ru–Cr(x) catalysts existed as Cr₂O₃. The amount of the (Zn(OH)₂)₃(ZnSO₄)(H₂O)_xsalt (x = 1 or 3) chemisorbed on Ru surface slightly decreased with the increase of the amount of Cr2O3, resulting in a slight decrease of the selectivity to cyclohexene for the Ru–Cr(0.42) catalyst. Co and Ni promoters were present as Co₃O₄ and Ni(OH)₂ in the Ru–Co(x) and Ru–Ni catalysts, respectively. Increasing amounts of Co₃O₄ and Ni(OH)2 increased the chemisorption of (Zn(OH)₂)₃(ZnSO₄)(H₂O)_x salt (x = 1 or 3), leading to a slight decrease in activity and a slight increase in selectivity of the Ru–Co(x) and Ru–Ni(x) catalysts to cyclohexene. The promoters Mn, Fe and Zn existed as Mn₃O₄, Fe₃O₄ and ZnO, respectively, in the Ru–Mn(x), Ru–Fe(x) and Ru–Zn(x) catalysts. These could react with ZnSO₄ to form the (Zn(OH)₂)₃(ZnSO₄)(H₂O)_x salt (x = 1 or 3). The amount of chemisorbed (Zn(OH)₂)₃(ZnSO₄)(H₂O)_x salt (x = 1 or 3) was significantly increased with the content of Mn₃O₄, Fe₃O₄ and ZnO, resulting in a prominent decrease in activity and a significantincrease in cyclohexene selectivity ofthe Ru–Mn(x), Ru–Fe(x) and Ru–Zn(x) catalysts. The Ru–Mn(0.23),the Ru–Fe(0.47) and the Ru–Zn(0.27) catalysts provided maximum cyclohexene yields of 55.3%, 56.7% and 53.4%, respectively. The Cu promoter in the Ru–Cu(0.49) catalyst was present as CuO. Part of the CuO could react with the ZnSO4 in the slurry to form a Cu4(SO4)(OH)6(H2O) salt. The presence of the chemisorbed Cu₄(SO₄)(OH)₆(H₂O) and (Zn(OH)₂)₃(ZnSO₄)(H₂O)_x(x = 1 or 3) salts improved the selectivity of the Ru–Cu(0.49) catalyst to cyclohexene.

Keywords:
Transition metals
Benzene
Hydrogenation
Cyclohexene
Ruthenium

Published in: Applied catalysis A: General  (Volumes 464–465, Pages 1-384, 15 August 2013)

Publisher: Elsevier  

ISSN Information: 0926-860X

Effect of transition metals (Cr, Mn, Fe, Co, Ni, Cu and Zn) on the hydrogenation properties of benzene over Ru-based catalyst

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