Microwave-assisted valorization of glycerol to solketal using biomass-derived heterogeneous catalyst

Abstract

The increase in biodiesel production worldwide makes valorisation of the by-product of this process (glycerol) essential for economic sustainability. Hence, conversion of bioglycerol to platform chemicals such as (2,2-dimethyl-1,3-dioxolan-4-yl)methanol (solketal), a fuel additive, is highly desirable. In this study, glycerol is converted to solketal using a sulfonic acid-functionalized aromatic carbonaceous material (SAFACAM) bearing ancillary hydrophilic groups and acting as a heterogeneous catalyst under microwave irradiation. For the production of solketal by acetalization, an optimal glycerol: acetone molar ratio of 1:5 was recorded. Using a catalyst dosage of 8 wt. % at 70 °C for just 10 mins under microwave irradiation (50 W, 100 psi) returned a 98.1±0.4 % conversion of bioglycerol with 100 % selectivity to solketal. The activation energy of the acetalization reaction was determined to be 35.8 kJ mol–1. Catalyst recovery was probed to over six cycles, with a modest loss in activity (82.3±0.2 % conversion in the sixth cycle) resulting from limited active site leaching, as confirmed by EDX data.