Catalytic Preparation and Value Addition of Renewable Chemical Intermediates from Carbohydrates

Abstract

Adopting biomass-derived fuels and chemicals could help to relieve the economic and environmental distresses triggered by the excessive use of petrofuels and petrochemicals. Moreover, the suitable integration of biomass carbon in the chemical industry would be a giant step toward their long-anticipated sustainability. Carbohydrate-derived furfural (FUR), 5-(hydroxymethyl)furfural (HMF), and levulinic acid (LA) have received significant attention over the past three decades as renewable chemical platforms for the synthesis of a variety of biofuels and chemicals of commercial significance. The elegant acid-catalyzed processes allow the selective removal of excess oxygen atoms from the parent sugar molecules in the form of water under energy-efficient conditions. The inherent instability in aqueous acid, hydrophilicity, and poor thermal stability of HMF complicates its isolation from the aqueous/polar reaction media and challenges the scalability of the process. In this regard, the hydrophobic analogs of HMF have received significant interest as the functional equivalent of HMF. 5-(Chloromethyl)furfural has also gained considerable interest as a substitute for HMF and has shown promise as the hydrophobic congener of HMF. Similarly, the esters of HMF, such as 5-(acyloxymethyl)furfural, are particularly interesting since they are halogen-free, hydrolytically stable, and hydrophobic analogs of HMF. The functionalities present in platform molecules are exploited for selective synthetic transformations, preferably under catalytic conditions, to make products of desired structural and functional characteristics. For example, the Baeyer-Villiger oxidation of furanics, especially FUR to 2-furanone, remains largely underexplored. The catalytic esterification or transesterification of biomass-derived intermediates will lead to corresponding esters with potential applications as green solvents, novel oxygenates, plasticizers, surfactants, and chemical reagents. Carbohydrate-derived renewable chemicals are of academic and commercial interest. Even incremental improvement in their yields and simplification of the processes for their production will significantly benefit this area of research.