Current developments and future trends in photocatalytic glycerol valorization: process analysis
The rapid advances in biodiesel technologies in recent years and the generation of huge amounts of glycerol as a by-product have led to a glycerol glut in the market and a significant drop in its price. The development of suitable techniques for glycerol valorization has recently attracted considerable attention and the photocatalytic process emerged as a forefront technology that integrates solar energy with glycerol conversion at ambient temperature and atmospheric pressure. The present review focusses on the analysis of this photocatalytic process to address the challenges and opportunities for its implementation. In this regard, the mechanisms of glycerol photoreforming and photo-oxidation as well as their gaseous (like hydrogen) and value-added liquid products are first analyzed. The developed kinetic and empirical models are then discussed to evaluate the prospects in the analysis of this process through a modeling approach. Finally, a thorough critical assessment is performed on the research related to synthesis parameters like cocatalyst percentage and calcination conditions, as well as the most critical operating parameters such as the hydrogen source, reaction time, glycerol concentration, solution pH, photocatalyst loading, photocatalyst stability, source and intensity of light, and reaction temperature.