Study on tri-component Ru/NbOPO4/TiO2 catalyst for the hydrodeoxygenation of depolymerized lignin products into valuable products

Lignin, a complex and abundant biopolymer, represents a significant challenge in the paper industry as it is often considered waste material. However, lignin possesses immense potential as the first natural source of aromatic components, which can be harnessed to produce valuable dehydrogenated products. The focus of this study is the synthesis of a three-component acidic heterogeneous catalyst containing Nb, Ti, and Ru and its application in the lignin conversion into valuable dehydrogenized products. The catalyst preparation was first carried out at different acidity conditions in the preparation solutions. Afterwards, the structure of the support and of the loaded particles were characterized with analytical techniques. N2-phisysisorption was used to understand the surface area of the catalysts, NH3-TPD for determining the acidity of the catalyst, XRD, SEM-EDX, FT-IR and TEM to understand the structure the catalyst had after the preparation at different acidity conditions. The catalytic activity was studied in a batch reactor at different temperatures and reaction times to have a complete knowledge on the efficiency of the catalyst itself, using eugenol as reference reactant. It showed a good breaking of the methoxy group in the reactant, as well as the hydrogenation of the unsaturated C-C and -OH bonds. Regarding the structure of the catalyst: metallic Ru contributed to the increase of the acidity of the catalyst with a correspondent increase in Lewis’s acid sites; TiO2 contributed increasing the stability in the different reaction conditions while NbOPO4 improved the selectivity towards the cleavage of the -OH and the hydrogenation of the aromatic ring. A kinetic study was carried out to identify the reaction mechanism, a rate law, and compute the partial reaction order.