Catalytic Dehydration of Glycerol Over Silica and Alumina‐Supported Heteropoly Acid Catalysts

With the increase in biodiesel production and owing to the excess market supply as well as the decline in the pricing of glycerol, it can easily be one of the important building blocks for biorefineries. However, from an industrial viewpoint, it is very important to produce value-added chemicals from glycerol. It is not only because of the high availability of glycerol but also due to the significant roles played by its physicochemical properties like nontoxicity, edibility, bio-sustainability, and biodegradability. Furthermore, owing to its high functionality, glycerol can be utilized for different types of fine chemical synthesis by different catalytic reactions. In this context, catalytic dehydration of glycerol to acrolein is one of the promising ways of valorization as the product is an important chemical intermediate in the preparation of polyurethane, polyester, propylene glycol, dl -methionine, and many other industrially important compounds. Although heteropoly acids (HPAs) are considered suitable candidates for this purpose owing to their strong and tunable (Brønsted) acidity, they lack thermal stability, possess low specific surface area (<10 m 2 g −1 ), and most of the materials are soluble under reaction conditions. On the other hand, dispersing and stabilizing these solid acids onto suitable high- surface-area silica, alumina, activated carbon, etc., is important for the catalytic application. The key aspects of glycerol dehydration reaction, such as the effect of textural property, catalyst loading, type of HPA, nature of acid sites, and influence of catalyst support on acrolein product selectivity, were discussed in detail.