Operando DRIFT-MS study of oxidative steam reforming of ethanol (OSRE) on Ni-Co mixed oxides under non-equilibrium conditions

Abstract

The oxidative steam reforming of ethanol (OSRE) reaction to produce hydrogen under non-equilibrium conditions was successfully achieved using mixed oxides (MO) of Ni and Co. The catalysts were synthesized with hydrotalcite (HT) type as a precursor by simultaneous coprecipitation assisted by microwaves. The solids were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The OSRE reaction was also implemented under operando conditions by diffuse reflectance infrared spectroscopy with Fourier transform coupled to mass spectrometry (DRIFT-MS) to study the path of molecules on the surface of these solids. The results confirmed the presence of the reduced phases of Ni and Co for all the systems and revealed that the OII/OI ratio increased for the samples containing Co, indicating that the greatest number of oxygen vacancies is present in these solids, which explains their high capacity to oxidize CO to CO2 in the catalytic test. It was possible to show that the NiCo bimetallic phase presents better catalytic performance for the production of hydrogen by effectively breaking the C-C bond and oxidizing the CHx species on the surface, which is reflected in the complete conversion of ethanol and a high selectivity to CO2 and H2 over other products such as CO, CH4, and acetaldehyde.