Hydrogenolysis of Glycerol to Propylene Glycol: Energy, Tech-Economic, and Environmental Studies

Hydrogenolysis of glycerol to propylene glycol represents one of the most promising technologies for biomass conversion to chemicals. However, conventional hydrogenolysis processes are often carried out under harsh H₂ pressures and temperatures, leading to intensive energy demands, fast catalyst deactivation, and potential safety risks during H₂ handling. Catalytic transfer hydrogenolysis (CTH) displays high energy and atom efficiency. We have studied a series novel solid catalysts for CTH of glycerol. In this work, detailed studies have been conducted on energy optimization, tech-economic analysis, and environmental impact for both processes. The key finding is that relatively less energy demands and capital investment are required for CTH process. CO₂ emission per production of propylene glycol is much lower in the case of transfer hydrogenolysis. The outcome of this study could provide useful information for process design and implementation of novel hydrogenolysis technologies for other energy and environmental applications.

CrOx decoration on Fe/TiO2 with tunable and stable oxygen vacancies for selective oxidation of glycerol to lactic acid

Non-noble metal-based catalysts catalyze the conversion of glycerol to lactic acid.

Catalytic Transfer Hydrogenolysis of Glycerol over Heterogeneous Catalysts: A Short Review on Mechanistic Studies

Catalytic transfer hydrogenolysis, using liquid H-donors in the absence of pressurized H₂ under mild temperatures, is regarded as the most important technology to substitute traditional hydrogenation processes in industry. Despite decade development with several breakthroughs in catalyst design, the reaction mechanism involved in H₂ generation and subsequent hydrogenolysis reactions is still under debate. In this review, transfer hydrogenolysis of glycerol, as a representative example, on metallic catalysts is revised critically with respect to surface reaction mechanism and catalyst design. The detailed reaction pathways for propanol, methanol, formic acid and ethanol for H₂ generation have been discussed systematically. In particular, reaction mechanism for catalytic C-H cleavage, H spillover/transfer and C-O cleavage reaction steps will be critically revised with experimental and theoretical results in literature. Insights into reaction pathways, mechanism and H₂ transfer efficiency and structure-performance relation for Pd, Cu and Ni catalysts will be provided for future development of catalyst manufacture and process development. The outcome of this work is useful for successful implementation of bio-refinery.

Recent Advances in Glycerol Catalytic Valorization: A Review

Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.