The response surface optimization of steryl glucosides removal in palm biodiesel using silica adsorption

A critical disadvantage of palm biodiesel is the presence of precipitates above the cloud point temperature. Gas chromatography with flame ionization detector (GC-FID) and Fourier transform infrared spectroscopy (FTIR) were employed to identify the composition of the precipitates. The results showed that steryl glucosides (SGs), mono-, and diglycerides were the major precipitates, even when contamination by mono- and diglycerides in biodiesel was in accordance with the ASTM D 6751 and EN 14214 standards. Therefore, this research investigated the optimal removal conditions for SGs in palm biodiesel through response surface design. Three independent parameters were studied: silica concentration, adsorption temperature and adsorption time. The optimal conditions for SGs removal was 3 wt% silica concentration, 112 °C adsorption temperature and 72 min adsorption time. Under these removal conditions, it was found that SGs were completely removed using GC-FID and FTIR analysis. Moreover, this removal treatment provided a higher quality of biodiesel, comprising 99.72% fatty acid methyl ester, 0.38% monoglycerides, 0.09% diglycerides and 0.14% triglycerides.