Natural albite as a novel solid basic catalyst for the effective synthesis of biodiesel: Characteristics and performance

Abstract

Abstract The characteristics and performance of natural albite as a solid basic catalyst was investigated in the transesterification of rapeseed oil to produce biodiesel. TEM images and the BET results indicate that natural albite has a small surface area (0.1601 m2·g−1) with non-porous structure. XRD analysis indicated that the catalyst comprises two crystalline phases: quartz (SiO2) and albite (NaAlSi3O8), at proportions of 27% and 73%, respectively. Crystal structure analysis showed that the basic sites of NaAlSi3O8 are bridge oxygens that connect silicon-oxygen tetrahedron [SiO4] and aluminium-oxygen tetrahedron [AlO4] or [SiO4]. The basicity of all bridge oxygens under the same chemical environment is almost identical, as identified by XPS analysis. The catalyst has high catalytic activity and good water resistance, and it also immunes from the free fatty acids (FFA) in raw materials. High fatty acid methyl ester (FAME) conversion of 95.15% and 97.42% was obtained with rapeseed oil and mixture oils (rapeseed oil with 10 wt% oleic acid) under the optimized conditions of 10 wt% catalyst dosage, methanol/oil molar ratio 12:1, at 200 °C for 8 h. Furthermore, it remained above 94.33% and 94.53% in rapeseed oil and mixture oil, respectively, after reusing the catalyst for five cycles without catalyst compensation.