Effect of supercritical water on the stability of WO X /TiO 2 and NbO X /TiO 2 catalysts during glycerol dehydration

Heterogeneous Catalysts for Conversion of Biodiesel-Waste Glycerol into High-Added-Value Chemicals

The valuable products produced from glycerol transformation have become a research route that attracted considerable benefits owing to their huge volumes in recent decades (as a result of biodiesel production as a byproduct) as well as a myriad of chemical and biological techniques for transforming glycerol into high-value compounds, such as fuel additives, biofuels, precursors and other useful chemicals, etc. Biodiesel has presented another challenge in the considerable increase in its byproduct (glycerol). This review provides a recent update on the transformation of glycerol with an exclusive focus on the various catalysts’ performance in designing reaction operation conditions. The different products observed and cataloged in this review involved hydrogen, acetol, acrolein, ethylene glycol, and propylene glycol (1,3-propanediol and 1,2-propanediol) from reforming and dehydration and hydrogenolysis reactions of glycerol conversions. The future prospects and critical challenges are finally presented.

Gas phase dehydration of glycerol to acrolein over WO3-based catalysts prepared by non-hydrolytic sol–gel synthesis

Solid acid catalysts based on WO₃–SiO₂ and WO₃–ZrO₂–SiO₂ were prepared by one-pot non-hydrolytic sol–gel method and tested in the gas phase glycerol dehydration to acrolein. Their structural and textural characteristics were determined by X-ray diffraction (XRD), N₂ adsorption, X-ray energy dispersive spectroscopy (XEDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Their acid characteristics were studied by both temperature programmed desorption of ammonia (NH₃-TPD) and FTIR of adsorbed pyridine. Under our operating conditions, all the catalysts were active and selective in the transformation of glycerol to acrolein, which was always the main reaction product. The high selectivity to acrolein is achieved on catalysts presenting a higher proportion of Brønsted acid sites. In addition, the role of oxygen in the feed on catalytic performance of these catalysts is also discussed.

Active and selective W–Si–(Zr)–O catalysts for glycerol dehydration to acrolein have been successfully prepared by non-hydrolytic sol gel method.