CO2 methanation over Ni/Al2O3-ZrO2 catalysts: Optimizing metal-oxide interfaces by calcinating-induced phase transformation of support

Abstract

A new strategy to prepare the NiO/Al2O3-ZrO2 catalyst with various interfacial structures by inducing different phase transitions of Al2O3 and ZrO2 via varying the precursor calcination temperature was proposed, and their CO2 methanation performance was subsequently investigated. The characterization of the catalyst showed that Ni was prone to bonding with Al ion during the calcination process and forming NiAl2O4 or strong interaction between Al2O3 and NiO. The reduced metallic nickel (Ni0) and partially unreduced NiAl2O4 exist in the state of Ni-NiAl2O4/Al2O3-ZrO2, forming a multi-interface system of Ni-O-Al, Al-O-Zr, and Ni-O-Zr. Moreover, this supplies medium-strength adsorption sites that play a key role in CO2 activation. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) analysis and catalytic activity revealed that the CO2 methanation was completed in a two-step coupling route of Reverse Water Gas Shift (RWGS) and CO methanation. The abundant interfaces of the catalyst effectively suppressed the sintering of Ni.