Zn1.2H0.6PW12O40 Nanotubes with Double Acid Sites as Heterogeneous Catalysts for the Production of Biodiesel from Waste Cooking Oil

摘要

Zinc dodecotungstophosphate (Zn1.2H0.6PW12O40; ZnPW) nanotubes, which feature Lewis acid and Bronsted acid sites, were prepared using cellulose fibers as templates. The structure, acid properties, and catalytic activity of the nonotubes as heterogeneous catalysts for biodiesel production were then studied in detail. The ZnPW nonocatalyst exhibited higher catalytic activities for the simultaneous esterification and transesterification of palmitic acid than the parent acid catalyst 12-tungstophosphoric acid (H3PW12O40). Moreover, the doubly acidic nanotubes led to markedly enhanced yields of methyl esters in the conversion of waste cooking oil (containing 26.89 wt% free fatty acids and 1% moisture) to biodiesel. The catalyst could be recycled and reused with negligible loss in activity over five cycles. The ZnPW nonocatalyst is acid- and water-tolerant and is an environmentally benign heterogeneous catalyst for the production of biodiesel from low-quality feedstocks.