CO methanation over Ni/SiO-AlO catalysts: effect of Ba, La, and Ce addition.

One of the most technologically and financially feasible methods for managing anthropogenic CO emissions is CO hydrogenation to methane. However, the high efficiency of mostly used nickel-based catalysts is still a challenge in the CO methanation process. Herein, 10% silica-90% alumina, commercially known as SIRAL-10, was used as a support for nanostructured Ni catalysts. Modified SIRAL-supported nickel catalysts (Ni/SA) with Ba, La, and Ce metals as promoters were prepared by a simple wet impregnation method. These catalysts were tested for atmospheric CO methanation reaction in a 250-500 °C temperature range in a tubular fixed bed reactor with a H/CO molar ratio of 4. As prepared samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, hydrogen temperature-programmed reduction (H-TPR), carbon dioxide temperature-programmed desorption (CO-TPD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). CO methanation was found to be highly dependent on surface basic sites and Ni dispersion. Ni active sites were mainly obtained from the reduction of strongly interacted NiO at temperatures >700 °C. All promoted catalysts showed better catalytic activity than unpromoted nickel catalysts. Maximum CO conversion of 85.6% was obtained on the Ba-promoted sample at 400 °C, while low-temperature catalyst activity was achieved in the case of Ce-Ni/SA. The catalysts exhibited CH selectivity in the following order: Ce-Ni/SA > Ba-Ni/SA > La-Ni/SA > Ni/SA. The Ce-containing sample showed exceptional catalytic performance with about 78.4% CO conversion and 98% CH selectivity at 350 °C. Both Ba and Ce-promoted catalysts exposed the best stability for 24 hours. Unique features of the SIRAL support and the addition of basic promoters facilitated the sequential hydrogenation of CO to produce almost CO-free CH.