Heteropolyacid Nanoreactor with Double Acid Sites as a Highly Efficient and Reusable Catalyst for the Transesterification of Waste Cooking Oil

Abstract

A solid zirconiumdodecatungstophosphate Zr0.7H0.2PW12O40 (abbreviated as ZrHPW) with nanotube structure has been synthesized using natural cellulose fiber as a template. The structure and morphology were characterized to show that the primary Keggin structure remained intact in a nanotube with large surface area (256 m2/g). On the basis of the research of acidity, ZrHPW exhibited higher acid strength, both Brønsted acidity and Lewis acidity in one to show higher efficiency, and reusable catalytic activity in biodiesel production from low-quality feedstocks. A synergistic effect results from the channels in the nanotube and doubly catalytic sites to provide an efficient approach to acidic sites for reactants, as well as enough space for subsequent recycling.