Chemistry: A European Journal 2015-11-09

State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media.

Zizwe A Chase, Stanislav Kasakov, Hui Shi, Aleksei Vjunov, John L Fulton, Donald M Camaioni, Mahalingam Balasubramanian, Chen Zhao, Yong Wang, Johannes A Lercher

Index: Chemistry 21 , 16541-6, (2015)

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Abstract

The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was studied during aqueous-phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM-5 supports, NiO and Ni(OH)2 were readily reduced to Ni(0) under reaction conditions (≈35 bar H2 in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). In contrast, Ni supported on SiO2 was not stable in a fully reduced Ni(0) state. Water enables the formation of Ni(II) phyllosilicate, which is more stable, that is, difficult to reduce, than either α-Ni(OH)2 or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni(0) particles on HZSM-5 were stable even in presence of 15 wt. % acetic acid at 473 K and 35 bar H2 . © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.