Water–gas shift reaction over gold deposited on NiAl layered double hydroxides

• DOI: 10.1007/s11144-019-01572-2
• Publication Date: 2019-04-05T15:47:01Z
• Authors: Margarita Gabrovska; Tatyana Tabakova; Ivan Ivanov; Daniela Kovacheva
• Keywords: Water-gas shift reaction; Layered double hydroxides; Physisorption; Coprecipitation

Three samples of NiAl layered double hydroxides with takovite-like structure were prepared by a co-precipitation method at Ni2+/Al3+ molar ratios of 1.5, 2.5 and 4.0. The samples were investigated as catalysts for hydrogen production by means of water–gas shift reaction (WGSR). The properties and catalytic behavior of the unmodified as-synthesized materials are compared with those of the same materials used as a support on which gold particles have been deposited. All samples were characterized by N2 physisorption, Powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) techniques. Catalytic activity of all materials was studied towards conversion of CO at atmospheric pressure within the temperature interval 140–300 °C. The dependence of WGS activity on the Ni2+/Al3+ molar ratio and the presence of gold were investigated. The promotional role of Au on the WGS performance was clearly demonstrated by Au–NiAl2.5 catalyst, which reached equilibrium conversion value of 97.6% at 240 °C. The stability test of the most active Au–NiAl2.5 catalyst resulted in the same CO conversion degree within 32 h under stream at 260 °C. A plausible scheme for the reaction mechanism, including the redox Ni2+ ↔ Ni3+ transition on the catalyst surface as well as adsorption and activation of the CO molecule on the Au particles, is proposed.