Water–Gas Shift and CO Methanation Reactions over Ni–CeO2(111) Catalysts

Abstract

X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO2(111) surfaces. Upon adsorption on CeO2(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500–800 K) leads to partial reduction of the ceria substrate with the formation of Ni2+ species that exists as NiO and/or Ce1−xNixO2−y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO2(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce+3 cations, CO dissociates on the surface at 300 K forming NiCx compounds that may be involved in the formation of CH4 at higher temperatures. At medium and large Ni coverages (>0.3 ML), the Ni/CeO2(111) surfaces are able to catalyze the production of methane from CO and H2, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (<0.3 ML), the Ni/CeO2(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water–gas shift reaction

Ni-CeO2/C Catalysts with Enhanced OSC for the WGS Reaction

“…In both cases, long term and start-up/shut-down, the deactivation is related to the well-known phenomenon of Ni particles sintering. Actually, as previously proposed, the presence of water potentiates Ni particles agglomeration especially at high temperatures [22,23]. TEM images presented in Figure 5, corresponding to the Ni-CeO2/C catalyst, evidences the Ni sintering process.…”

Ambient pressure XPS and IRRAS investigation of ethanol steam reforming on Ni–CeO2(111) catalysts: an in situ study of C–C and O–H bond scission

“…16,[20][21] Hydroxyl groups generated from these strong metal-support interactions could play an important role in redox chemistry such as in the water-gas shift (WGS) reaction and for suppressing coke formation with subsequent deactivation. 21 …”

Anthracene aquacracking using NiMo/SiO2 catalysts in supercritical water conditions

“…Again, as observed for the liquid fraction, the gas product distribution varies with catalyst composition. In fact, simultaneous reactions such as water gas shift, reforming, CO and CO 2 methanation are plausible since Ni is a typical active phase for them [42][43][44] and may have had influence on the gases obtained. In particular the relatively high hydrogen concentrations observed may have resulted from the excess of water in the media favoring reforming and shift reactions in addition to the capacity of the catalysts to promote water splitting.…”