Impact of Sr Addition on Zirconia–Alumina-Supported Ni Catalyst for CO<i><sub>x</sub></i>-Free CH<sub>4</sub> Production via CO<sub>2</sub> Methanation
Abdulaziz A.M. Abahussain, Ahmed S. Al‐Fatesh, Yuvrajsinh B. Rajput, Ahmed I. Osman, Salwa B. Alreshaidan, Hamid Ahmed, Anis H. Fakeeha, Abdulrhman S. Al‐Awadi, Radwa A. El‐Salamony, Rawesh Kumar
Abstract
High Resolution Image Download MS PowerPoint Slide Zirconia-alumina-supported Ni (5Ni/10ZrO 2 +Al 2 O 3 ) and Sr-promoted 5Ni/10ZrO 2 +Al 2 O 3 are prepared, tested for carbon dioxide (CO 2 ) methanation at 400 °C, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, surface area and porosity, infrared spectroscopy, and temperature-programmed reduction/desorption techniques. The CO 2 methanation is found to depend on the dispersion of Nickel (Ni) sites as well as the extent of stabilization of CO 2 -interacted species. The Ni active sites are mainly derived from the reduction of ‘moderately interacted NiO species’. The dispersion of Ni over 1 wt % Sr-promoted 5Ni/10ZrO 2 +Al 2 O 3 is 1.38 times that of the unpromoted catalyst, and it attains 72.5% CO 2 conversion (against 65% over the unpromoted catalyst). However, increasing strontium (Sr) loading to 2 wt % does not affect the Ni dispersion much, but the concentration of strong basic sites is increased, which achieves 80.6% CO 2 conversion. The 5Ni4Sr/10ZrO 2 +Al 2 O 3 catalyst has the highest density of strong basic sites and the highest concentration of active sites with maximum Ni dispersion. This catalyst displays exceptional performance and achieves approximately 80% CO 2 conversion and 70% methane (CH 4 ) yield for up to 25 h on steam. The unique acidic–basic profiles composed of strong basic and moderate acid sites facilitate the sequential hydrogenation of formate species in the CO x -free CH 4 route.