Novel Ni-ZrO2 catalyst doped with Yb2O3 for ethanol steam reforming

A type of Yb2O3 doped Ni-ZrO2 catalyst for ethanol steam reforming was developed, and displayed excellent catalyzing performance for the selective formation of H-2 and CO2. Over a Ni1.25Zr1Yb0.8 catalyst, STY(H-2) can maintain stable at the level of 0.396 mol h(-1) g(-1) (data taken 120 h after the reaction started) under the reaction conditions of 0.5 MPa and 723 K, which was 1.6 times that (0.247 mol h(-1) g(-1)) of the Yb-free counterpart Ni1.25Zr1. Characterization of the catalyst revealed that dissolution of an appropriate amount of Yb3+ ions in the zirconia host resulted in the formation of the Zr-Yb composite oxide with cubic-ZrO2 structure, c-(Zr-Yb)O-z, which inhibited effectively the transformation of c-ZrO2 to thermodynamically more stable m-ZrO2, thus avoiding sintering of the (Zr-Yb)O-z composite. It was demonstrated that the doping of Yb2O3 to Ni-ZrO2 changed also the valence states or the micro-environments of the Ni-species at the quasi-active surface of the tested catalyst, which was conducive to inhibiting agglomeration of the Ni-x(0)-Nin+ species active catalytically, with resulting in maintaining the high metallic nickel dispersion and inhibiting coking. The aforementioned two factors both contributed to improving the activity and operating stability as well as heat-resistant quality of the catalyst. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.