Biodiesel production from Jatropha oil using mesoporous molecular sieves supporting K2SiO3 as catalysts for transesterification

Abstract

A series of solid base catalysts based on potassium salts (K2CO3, K2SiO3 and KAc) supported on mesoporous silicas (SBA-15 and AlSBA-15) were prepared by impregnation method and used to catalyze the transesterification of Jatropha oil with methanol. The prepared catalysts were characterized by several techniques such as X-ray diffraction (XRD), Brunauer–Emmet–Teller method (BET), transmission electron microscopy (TEM) and temperature-programmed desorption of CO2 (CO2-TPD). In addition, various parameters affecting catalytic activity and biodiesel yield were investigated. The results showed that Al element dopant in SBA-15 could protect the pore structure of supported catalyst. The basicity and catalytic activity of AlSBA-15 silica were improved significantly after loading potassium compounds. The activity of K2SiO3 impregnated catalyst was superior to those of K2CO3 and KAc impregnated catalysts. A biodiesel yield of 95% was obtained (using the K2SiO3/AlSBA-15 catalyst) with 30wt.% of K2SiO3 loading on AlSBA-15 support, methanol/Jatropha oil molar ratio 9, reaction temperature 60°C, reaction time 150min and catalyst/oil mass ratio 3%. Reuse of the catalyst indicated that the K2SiO3/AlSBA-15 had steady catalytic activity compared with traditional KOH and K2CO3 catalysts. After being reused for 5cycles, a modest decrease of its activity led to a reduction of about 6% in the biodiesel yield. This decrease of catalytic activity was mainly caused by the potassium leaching and the adsorption of organic deposits on the catalyst surface.