Co-production of biodiesel and hydrogen from rapeseed and Jatropha oils with sodium silicate and Ni catalysts

Calcined sodium silicate was used to rapidly catalyze the transesterification of rapeseed and Jatropha oils to biodiesel under microwave irradiation. Biodiesel yields of 95.8% and 92.8% were achieved from rapeseed and Jatropha oils, respectively (microwave power of 400 W, methanol/oil molar ratio of 11/1, catalyst amount of 4 wt.% and reaction time of 5 min). The catalyst was recycled, and biodiesel yield reduced to 83.6% at the fourth cycle. Fresh and reused sodium silicate catalysts were charaterized by BET (Brunauer, Emmett and Teller) surface area, XRD (X-ray diffraction), SEM (scanning electron microscope) and CO2-TPD (temperature programmed desorption), and it was found that the agglomeration and leaching of basic species resulted in the loss of catalytic activity. The reused catalyst was collected and utilized for hydrothermal gasification of glycerol to hydrogen. A maximum H2 yield of 82.8% with a concentration of 73.6% was obtained in the presence of the fourth-cycled sodium silicate and Ni catalysts at 350 °C. Sodium silicate was an effective catalyst for the microwave-irradiated production of biodiesel and hydrothermal production of hydrogen from by-product glycerol combined with Ni catalyst.