The green metric evaluation and synthesis of diesel-blend compounds from biomass derived levulinic acid in supercritical carbon dioxide

•Use of biomass feedstock, biocatalyst & SC-CO2 as a green renewable reaction system.•Greener metric evaluation (E-factor, carbon efficiency and mass productivity).•Excellent mass yield of the levulinate compounds can be obtained in SC-CO2.•Broad applicability of protocol to synthesize of various levulinates in SC-CO2.

Levulinate compounds are the biomass derived important energy products which are primarily used as diesel-blending components. These levulinates are the oxygenated fuel additive which promote complete combustion of fuel and reduces emission of pollutants like particulate matters and nitrogen oxides. In the present study, we have investigated sustainable synthesis of biomass derived levulinate compounds catalyzed by Cal B lipase in supercritical carbon dioxide (SC-CO2) as a green biocatalyst in green reaction media which provided an excellent mass yield. Various reaction parameters were optimized in details such as butanol, levulinic acid, biocatalyst, co-solvent, temperature and pressure to obtain 99% mass yield of the desired product. Moreover various green metric parameters (e.g. E-factor, carbon efficiency and mass productivity) of present methodology were evaluated. The green metrics evaluation suggested that developed procedure is a promising and a greener alternative as compared to various reported conventional synthetic protocols. The biocatalyst was efficiently recycled up to the five cycles. Moreover, the developed protocol can be used for synthesis of various industrially important levulinate compounds which also provided excellent mass yield. Thus, the present protocol demonstrated (i) robust biocatalytic application for transformation of renewable biomass derived levulinic acid (LVA) into value added chemicals and (ii) various green metric evaluation study for the sustainability.

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