Visible-light mediated sustainable route for conversion of biomass derived levulinic acid to value added compounds by porphyrin photocatalyst

Abstract

Photocatalytic esterification of levulinic acid to different levulinates by reaction with ROH (R=CH3, CH3CH2, CH3CH2CH2- CH3-CH2-CH2CH2-) and to tri-, di, and monoglycerides of levulinic acid, was studied by porphyrin-based photocatalyst. The influence of various reaction conditions including loading of photocatalyst, time of reaction, the intensity of light, and the ratio of the reactants on the model reaction was scrutinized, by exposure to visible light in a homemade photo-catalytic reactor. Using optimization reactions, an admirable yield of the alkyl levulinates (76%) and glycerides (81%) of levulinic acid, were achieved under visible light irradiations. Moreover, ethyl levulinate was further converted to γ-valerolactone under photocatalytic conditions using a 5 W LED light. The porphyrin photocatalyst was further explored for etherification of biomass-derived glycerol with alcohols (methanol/ethanol) (88%) under photocatalytic conditions. Both esterification and etherification reactions carried out under ambient conditions furnished appreciable product formation, illustrating the importance of porphyrin as a highly reactive, steady, and reusable heterogeneous photocatalyst.