Propane dry reforming over cerium promoted catalyst: enhancement of synthesis gas production under reduced carbon deposition

Abstract

Among others, the light hydrocarbon (C1-C4 alkanes) dry reforming process has attracted considerable attention with increasing global oil price, for developing sustainable environmentally-compatible synthesis gas (H2/CO mixtures) production and utilisation technologies. However, the foremost advantage of immediate suitability for gas-to-liquids (GTL) fuels’ conversion has been prevented by severe carbon deposition, the main challenge that rapidly deactivates the catalyst and the attendant economic implications. As a result, the principal goal of this study was to improve the dry reforming process through two main strategies, namely: carbon-resilient catalyst design, and reactor operation. In particular, a bimetallic catalyst which is based on Ni, the key ingredient in industrial reforming catalysts, was promoted by cerium as a rare earth metal that is well known for its high capacity for oxygen storage as well as its flexibility in redox state. Catalysts were prepared by co-impregnation using cobalt, nickel and cerium nitrate on γ-alumina support. Bimetallic catalyst of 5wt%Co-10wt%Ni was promoted with 0-2.5wt% cerium in 0.5wt% increments. Catalyst physicochemical properties were measured via various techniques including N2-physisorption, H2-chemisorption, temperature programmed desorption of NH3, CO2, C3H8, CH4 and CO, UV–vis diffuse reflectance spectroscopy. Morphological examination such as XRD, TEM and SEM and thermogravimetric analysis for calcination, reduction and oxidation were also undertaken. CO2-TPD results demonstrated the basicity of the promoted catalyst was nearly doubled. XRD analysis confirmed the presence of CeO2 and TEM images verified the metal dispersion data obtained from H2-chemisorption. Catalyst evaluation, reaction kinetics studies and O2-co-feeding investigation were performed in a fixed-bed reactor of 15 mm ID at 798–923 K under atmospheric pressure. The increase in catalyst basicity was reflected in catalyst activity as syngas production was successfully increased with Ce content before attaining a plateau at 1.5wt% while total carbon in spent catalysts was reduced to almost zero beyond this critical Ce loading. Conversely, reforming kinetic and deactivation coefficients that estimated from transient data over longevity runs of 72 h, validated the improvement in the promoted catalyst. Nevertheless, reactor operational studies indicated the ability to enhance syngas production under O2-co-feeding and fluidisation approaches.