Benign-by-Design Orange Peel-Templated Nanocatalysts for Continuous Flow Conversion of Levulinic Acid to N-Heterocycles

In this work, two different strategies have been employed to explore the potential valorization of biomass waste. A TiO2-based sample was prepared by a dry-milling strategy, involving orange peel valorization toward nano structured materials. Subsequently, ruthenium deposition was accomplished by a chemical reduction method to obtain different ruthenium loadings on the titania support. The prepared catalysts were characterized using a multitechnique approach in terms of chemical, structural, and morphological properties. Levulinic acid, a typical model molecule associated with lignocellulosic biomass, was subsequently converted into N-heterocycles in a continuous flow reactor. The prepared Ru-TiO2 systems exhibited outstanding catalytic performance in terms of conversion and selectivity in comparison with Ru/P25 and Ru/C catalytic references. Maximum activity (79% conversion, 85% selectivity to 1-ethyl-2-(ethylideneamino)-5-methylpyrrolidin-2-ol) was achieved for the sample containing 3 wt % Ru, homogeneously deposited on the titania surface. The obtained results were interpreted with the help of a complete postreaction characterization analysis of the most active sample.