Controllable synthesis of Ir(Rh)-Sn/SiO bimetallic catalysts surface organometallic chemistry for the production of ethanol from hydrogenolysis of ethyl acetate

• Published in: Catalysis science & technology Vol. 1; no. 4; pp. 186 - 195
• Main Authors: Xu, Rui, Lian, Kunbo, Xu, Zhikang, Yue, Yuanyuan, Yuan, Pei, Bao, Xiaojun, Yuan, Xiaohong, Zhu, Haibo
• Format: Journal Article
• Published: 24.02.2020
• DOI: 10.1039/c9cy02071c
• ISSN: 2044-4753

Ethanol as an alternative to traditional fossil fuels has recently attracted much attention all over the world, because ethanol is proven to be a clean, green and efficient fuel. Ethanol production from indirect syngas synthesis via the catalytic hydrogenolysis of esters has become one of the most competitive and sustainable routes. Ir-Sn and Rh-Sn bimetallic materials constitute the most effective catalysts for this reaction, because they exhibit high activity, selectivity and stability in the long-term reaction. A grafting approach based on the surface organometallic chemistry concept is developed for the synthesis of Ir(Rh)-Sn/SiO 2 catalysts via the direct generation of Ir(Rh)-Sn bimetallic particles at the surface of SiO 2 . The formation of bimetallic particles at the surface of SiO 2 was achieved by hydrogenolysis of the well-defined surface compounds &z.tbd;SiOIr(COD)/&z.tbd;SiOSnBu 3 or &z.tbd;SiORh(COD)/&z.tbd;SiOSnBu 3 , which were obtained from sequential grafting of [(COD)IrCl] 2 (or Rh(acac)(COD)) and HSnBu 3 complexes at the surface of dehydroxylated SiO 2 . This molecular synthesis methodology enables in situ generation of Ir-Sn or Rh-Sn clusters at the surface of SiO 2 under mild conditions, and affords highly dispersed Ir-Sn/SiO 2 and Rh-Sn/SiO 2 catalysts. The detailed structure of these two catalysts was systematically studied by STEM, XRD, N 2 adsorption, CO-IR and XPS techniques, which reveal that the Ir-Sn and Rh-Sn particles of around 1.2 nm are homogeneously distributed at the surface of the SiO 2 . The Ir-Sn/SiO 2 and Rh-Sn/SiO 2 catalysts with a Sn/Ir(Rh) ratio of 1 show the best performance in the hydrogenolysis of ethyl acetate for the production of ethanol, which can deliver a selectivity to ethanol of up to 99%. Moreover, these two catalysts show excellent stability in the catalytic reaction, and their high conversion and selectivity can be completely kept for a long-term run of 120 hours. A series of highly active Ir-Sn/SiO 2 and Rh-Sn/SiO 2 catalysts for ethyl acetate hydrogenolysis to ethanol were prepared from the grafting synthesis based on the surface organometallic chemistry concept.