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

• A series of AlSBA-15 silica supported potassium salt catalysts were prepared.
• AlSBA-15 silica was found to be suitable support material for K supported catalyst.
• The K2SiO3/AlSBA-15 silica catalyst showed superior catalytic activity.
• The improved catalytic activity is due to the increase of basicity and BET value.
• Reuse of the catalyst indicated that it had relatively steady catalytic activity.

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 30 wt.% of K2SiO3 loading on AlSBA-15 support, methanol/Jatropha oil molar ratio 9, reaction temperature 60 °C, reaction time 150 min 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 5 cycles, 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.

The CO2 desorption peak of the catalyst K2SiO3(35%)/AlSBA-15 (c) shifted to a higher temperature and their intensities were stronger than those of SBA-15 (a) and AlSBA-15 (b). This suggested that K2SiO3/AlSBA-15 presented a superior basicity, which would lead to a better catalytic activity.Figure optionsDownload as PowerPoint slide