Recent advances on the conversion of glycerol to acrolein, 1,3-propanediol, propanol and propylene using acidic heterogeneous catalysts
Glycerol, a by-product of biodiesel process, emerged recently as a renewable feedstock for chemical production instead of petroleum based chemicals. The conversion of glycerol to higher value chemicals will enhance the economic viability of the biodiesel industry. This has generated much interest in developing new catalysts and technologies to produce high value added chemicals from glycerol. The current trend sees majority of researchers focused on heterogeneous catalyst application for glycerol conversion. In the recent years, a number of researchers studied the conversion of glycerol to acrolein, 1,3-propanediol (1,3-PD), 1-propanol (1-PO) and propylene over acidic heterogeneous catalysts in particular with heteropolyacids (HPAs) as active compounds. In the catalytic area, HPAs are promising green solid acids to replace environmentally harmful liquid acid catalysts. The main purpose of this paper is to highlight the recent developments in the conversion of glycerol into value-added products, including acrolein, 1,3-PD, 1-PO and propylene using acidic heterogeneous catalysts. The key aspects of this reaction system, such as the nature of acid sites, influences of reaction variables, overall catalyst performance, reaction mechanisms, which control the product selectivity and yield, are reviewed. The major challenges confronting the selective production of these chemicals are discussed. Up to now, such a discussion is still missing, and we intend to cover this gap in this review.