Hierarchical Zeolites as Catalysts for Glycerol Upgrading Reactions

Resumo

In a context where society has a strong dependence on fossil fuels, research in biofuels is necessary to offer a more sustainable future. In this perspective, biodiesel has attracted much attention due to its high applicability. As a byproduct of biodiesel synthesis, glycerol is one of the main concerns in this field because its demand is lower than the offer, and also due to the accumulation in the industry may transform it into waste. To overcome this issue, several studies have proposed investing in glycerol chemical conversion. These reactions allow many industrial products such as acrolein, solketal, toluene, xylene, alcohols, and many others. Acid groups catalyze most glycerol conversion reactions, and zeolites are quite promising since they have intrinsic acidic properties. However, their microporous structure might offer diffusional limitations, preventing the access of glycerol molecules to acidic sites in the internal surface, causing a decrease in their performances or even deactivation. Studies have reported different methods to produce mesopores in the zeolite structure (hierarchical zeolites) and how they can affect its properties, including glycerol conversion and yields to several products. This paper discusses how hierarchical zeolites can produce value-added compounds from glycerol and resist deactivation.