The Influence of High-Energy Faceted TiO2 Supports on Co and Co-Ru Catalysts for Dry Methane Reforming.

The reforming of methane from biogas has been proposed as a promising method of CO2 utilization. Co-based catalysts are promising candidates for dry methane reforming. However, the main constraints limiting the large-scale use of Co-based catalysts are deactivation through carbon deposition (coking) and sintering due to weak metal-support interaction. We studied the structure-function properties and catalytic behavior of Co/TiO2 and Co-Ru/TiO2 catalysts using two different types of TiO2 supports, commercial TiO2 and faceted non-stoichiometric rutile TiO2 crystals (TiO2 *). The Co and Ru metal particles were deposited on TiO2 supports using a wet-impregnation method with the percentage weight loading of Co and Ru of 5% and 0.5%, respectively. The materials were characterized using SEM, STEM-HAADF, XRD, XPS and BET. The catalytic performance was studied using the CH4 : CO2 ratio of 3 : 2 to mimic the methane-rich biogas composition. Our results indicate that the addition of Ru to Co catalysts supported on TiO2 * reduces carbon deposition and influences oxygen mobility. Co and Co-Ru catalysts supported on TiO2 * has superior activity with the highest conversion of CO2 and CH4 of 34.7% and 23.5%, respectively. Despite the improved performance, the Co-Ru/TiO2 * catalyst has limited stability due to the proliferation of nanoparticle growth and TiOx layers on the surface of the nanoparticles indicating the prevalence of the strong-metal support interaction.

Heterogeneous Catalyst Design Principles for the Conversion of Lignin into High-Value Commodity Fuels and Chemicals.

Lignin valorization has risen as a promising pathway to supplant the use of petrochemicals for chemical commodities and fuels. However, the challenges of separating and breaking down lignin from lignocellulosic biomass are the primary barriers to success. Integrated biorefinery systems that incorporate both homo- and heterogeneous catalysis for the upgrading of lignin intermediates have emerged as a viable solution. Homogeneous catalysis can perform selected chemistries, such as the hydrolysis and dehydration of ester or ether bonds, that are more suitable for the pretreatment and fractionation of biomass. Heterogeneous catalysis, however, offers a tunable platform for the conversion of extracted lignin into chemicals, fuels, and materials. Tremendous effort has been invested in elucidating the necessary factors for the valorization of lignin by using heterogeneous catalysts, with efforts to explore more robust methods to drive down costs. Current progress in lignin conversion has fostered numerous advances, but understanding the key catalyst design principles is important for advancing the field. This Minireview aims to provide a summary on the fundamental design principles for the selective conversion of lignin by using heterogeneous catalysts, including the pairing of catalyst metals, supports, and solvents. The review puts a particular focus on the use of bimetallic catalysts on porous supports as a strategy for the selective conversion of lignin. Finally, future research on the valorization of lignin is proposed on the basis of recent progress.