Fabrication and catalytic assessment of Ni/Ce–Zr–O catalyst for enhanced hydrogen production via steam reforming of glycerol

Abstract

The valorization of glycerol, a plentiful byproduct derived from the biodiesel industry, for green hydrogen production via steam reforming (GSR) has attracted considerable attention. Nevertheless, catalysts developed for GSR encounter critical obstacles related to thermal stability and coke deposition during prolonged operations. In this study, we strategically employed thermally stable ZrO2 as a support along with redox-active Ce as a promoter for Ni to optimize both the preparation method and constituent content of the Ce-promoted Ni/ZrO2 catalyst for GSR. The physicochemical properties of both fresh and GSR-used catalysts were investigated using a range of characterization techniques, including XRD, H2-TPR, SEM-EDS/TEM, N2 adsorption/desorption, and TGA. The results demonstrate that the sol-gel method yields a Ni/Ce–Zr–O catalyst with smaller Ni crystals and a higher surface nickel content compared to the step impregnation and co-precipitation methods, thereby achieving enhanced catalytic activity. Moreover, the catalyst prepared by the sol-gel method exhibited excellent activity stability at elevated feedstock concentrations. Furthermore, it has been determined that there is an optimized amount of Ce doping for the Ni/ZrO2 catalyst, which allows the catalyst to achieve the highest pore parameters and surface nickel content. Among the studied catalysts, the one containing 30/50 wt% of designed CeO2/ZrO2 achieved the highest and most stable H2 yield (4.32 mol⋅mol−1) and carbon gasification efficiency (70.28 %) during a 24-h's GSR with a feedstock concentration of 15 wt% at 500 °C (with a WHSV of 45 h−1). Importantly, this optimized Ni/Ce–Zr–O catalyst effectively eliminates the deposition of filamentous/crystallized coke during long-term GSR operation due to enhanced oxygen vacancies created by the formed CexZr1-xO2 species, making it highly promising for large-scale applications.