Lithium Doping Y2O3: A Highly Efficient Solid Base Catalyst for Biodiesel Synthesis with Excellent Water Resistance and Acid Resistance

Abstract

A series of nLi–Y2O3 catalysts with different proportion of lithium oxide were prepared by wet impregnation method, the 0.1Li–Y2O3 catalyst exhibited highly efficient catalytic activity in biodiesel synthesis. The as-prepared catalysts were characterized by XRD, SEM, TEM, CO2–TPD and XPS techniques. The results indicated that the significant change in the basicity of Y2O3 with the addition of Li was attributed to the strong interaction produced by electron transfer between the components of the 0.1Li–Y2O3 catalyst and the distortion areas formed at the interface of crystal grains (grain boundaries) in Y2O3 nanocrystals. The load of lithium enhanced electron pair donating ability of the surface oxygen atom which made the catalyst easier to capture H+ from CH3OH, and promoted the yield of biodiesel eventually. At the same time, the experiment verified that the catalyst had outstanding reusability and universality on transesterification of different oils into biodiesel. When the acid value was 8.1 mg KOH/g, the yield of biodiesel still exceeded 80%. Furthermore, the yield of biodiesel was maintained above 90% after adding 2 wt% of water to palm oil, which indicated that 0.1Li–Y2O3 catalyst had good water resistance. The 0.1Li–Y2O3 catalyst was believed as an exceptional competitive catalyst for future commercial biodiesel production applications.