Microwave versus conventional promoted synthesis of fuel additives using graphitic carbon nitride supported catalysts†
Abstract
Microwave (MW) and conventional heating (CH) strategies were compared for the synthesis of fuel additives (alkyl levulinates) obtained from levulinic acid. Phosphomolybdic acid (PMA) and phosphotungstic acid (PTA)-containing graphitic carbon nitride (GCN) were synthesized and optimized to achieve 98% and 93% yield after 24 h (CH) as compared to 99% and 68% conversion at 150 °C after 10 min (MW) using GCN–PMA and GCN–PTA, respectively. Microwave irradiation significantly reduced reaction times, being a more sustainable approach for the synthesis of fuel additives including ethyl, isopropyl, butyl and allylic levulinates. Scale-up experiments were also performed by increasing the concentration from 0.28 M and up to 0.71 M of LA and a high productivity was obtained for optimum GCN–PMA under MW (226.31 mmol gCat−1 h−1) with respect to CH conditions (0.538 mmol gCat−1 h−1).
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