Executive Summary : | Chitin is the second most abundant biopolymer in nature that can be converted into renewable biofuels and biochemicals by selective catalytic processes. Over the past several years, there have been significant advances in the chemical-catalytic value addition of chitin into nitrogen-based small organics. However, for broader applications and markets of chitin-based biorefinery, nitrogen-free compounds must also be accessed in satisfactory yield and process scalability. Chitin has been converted to 5-(hydroxymethyl)furfural (HMF) by acid-catalyzed hydrolysis and dehydration steps. However, generally low yield of HMF (around 30 mol%) is obtained due to the inherent instability of HMF in aqueous acid. In this regard, the esters of HMF, such as 5-(acetoxymethyl)furfural (AcMF), has received much attention in recent years as hydrophobic, halogen-free, and stable congener of HMF. AcMF has been produced from simple sugars in good yield and selectivity. The major challenge in producing AcMF directly from chitin is the weak acidity of acetic acid. The biopolymers remain largely insoluble during the reaction and lead to undesired side products like humin. Metal salts, such as ZnCl2, dissolve biopolymers like cellulose in the right concentration. Interestingly, metal salts have been shown promise as Lewis acid catalysts for producing HMF from chitin. Therefore, a combination of acetic acid and ZnCl2 may be used to solubilize chitin during the hydrolysis reaction for a better yield of AcMF. A non-nucleophilic, strong Brønsted acid catalyst may also be used to make the reaction conditions milder. Under these conditions, acetic acid will primarily act as the reagent to convert the HMF intermediate into AcMF as soon as it forms. Acetic acid is a non-toxic, inexpensive, stable, and renewable organic acid that can be easily purified by fractional distillation. In this proposal, the preparation of AcMF will be attempted from purified chitin as well as crude chitin isolated from the exoskeleton of crustaceans (e.g., shrimp and crab shell waste). The AcMF preparation step will be optimized the process will be scaled up. The derivative chemistry of AcMF is much less explored than HMF. The derivatives of AcMF are of both academic and commercial significance. In this project proposal, AcMF prepared from chitin will be used as a chemical platform for synthesizing several novel furanic and levulinic derivatives following catalytic steps. For example, AcMF will be hydrogenated to 5-methylfurfural and 2,5-dimethylfuran that have potential applications as biofuel and chemical feedstock. AcMF will be converted to novel substituted angelica lactone and substituted γ-valerlactone derivatives. AcMF will be decarbonylated to form 2-acetoxymethylfuran, a potential fuel oxygenate and chemical intermediate. Moreover, AcMF will be converted to novel diesters of HMF with potential applications as neutral surfactants and plasticizers. |