Glycerol Transformation over Zeolite-Based Catalysts into Diverse Valuable Chemicals: A review

The utilization of fossil fuels has been the leading choice in the industrial revolution despite its negative environmental impact. Biodiesel is a well-known alternative to replace fossil fuels because it is a renewable and environmentally friendly fuel. The use of biodiesel increases every year, causing new problems. The transesterification reaction to produce biodiesel also produces a by-product of glycerol. Glycerol is among the world's 12 most essential chemical raw materials. The abundance of glycerol has not been followed by the level of consumption, so it is necessary to increase the value of the glycerol. The transformation of glycerol into high-value-added chemicals is a promising solution to utilizing abundant glycerol. Glycerol transformation can be done through several reaction pathways catalyzed by zeolite. Zeolite is a heterogeneous catalyst with acid-base sites and good framework selectivity, making it suitable for catalytic glycerol transformation. Zeolite can be used to catalyze glycerol through various reactions into high-value-added chemicals such as glycerol oxidation to produce dihydroxyacetone, glycerol hydrogenolysis to produce propylene glycol, glycerol dehydration to produce acrolein, glycerol transesterification with dialkyl carbonate to produce glycerol carbonate, glycerol pyrolysis to produce syngas, and glycerol etherification to produce glycerol ethers. This review highlights the current approaches to upgrade the value of glycerol, a by-product of biodiesel production, through catalytic transformation using zeolite as a heterogeneous catalyst. The catalytic processes of glycerol over zeolite with unique nanopore architectures with abundant acid sites could address the surplus glycerol problem enabling the production of high-value-added chemicals. Moreover, based on the current development, this review also provides areas of future research.