Design of heterogeneous catalysts for the conversion of glycerol and lactic acid to value-added N-containing compounds

Glycerol and lactic acid are two of the most promising bio-based platform chemicals. Their conversion with NH3 into value-added N-containing compounds over heterogeneous catalysts has attracted increasing attention in recent years. In her dissertation, Jiachen Li explores the catalytic conversion of glycerol and lactic acid into nitrogen-containing compounds, with alanine and lactamide as the main products. 

Li designed several catalytic systems, optimized to achieve high yield of alanine from glycerol. She explored both Ru- and Ni-based catalysts supported on TiO2 with different crystal structures, which revealed that TiO2-rutile is an especially effective support due to its structural compatibility with metal species and thermal stability (Chapters 2 and 3). Strong interfacial interactions between metal species and the rutile phase promoted the formation of ultra-small, well-dispersed nanoparticles or nanoclusters, enabling excellent catalytic performance. In contrast, catalysts supported on TiO2-anatase produced larger, aggregated particles and exhibited poor activity. 

Notably, the conversion of glycerol/lactic acid to alanine proceeded without external H2, relying instead on in-situ H2 generated during dehydrogenation of substrates and intermediates. Mechanistic investigations for the conversion of lactic-acid-related chemicals with NH3, clarified the reaction pathway, showing how solvent, substrate identity, and gas atmosphere influence the distribution of N containing products. Li also synthesized a high-surface-area TiO2-rutile (247 m2/g) and used it as a support for both Ru- and Ni-based catalysts. Li compared their structural properties and catalytic performance with those of catalysts supported on commercial low-surface-area TiO2-rutile (27 m²/g). Finally, the dissertation concludes with conclusive remarks and perspectives for future research.