Synthesis of Magnetic Solid Catalysts and Their Application for Biodiesel Manufacturing

In order to avoid the impact of climate change, the need for a global transition toward a low carbon energy system in urgent. This promotes the use of renewable energy sources for the future development. In this study, transesterifications of soybean oil and jatropha oil to biodiesel using magnetic solid alkali catalysts were examined. The nanometer magnetic catalysts were prepared by loading CaO and SrO onto the SiO2/Fe3O4 (CA/SM, SrO/SM). The magnetic catalyst can be separated easily by exerting magnetic field after transesterification reaction for further recovery, regeneration and reuse. This can simplify the process and decrease costs. A series of transesterification experiments were conducted to find proper operating conditions. The properties of biodiesel produced wewe measured and elucidated. The results indicated that CA/SM catalysts prepared from calcium acetate were unevenly dispersed with CaO and lost magnetism when Ca concentration in Ca-containg catalyst (CCa) is higher than 40 wt%. In contrast, for the catalyst using calcium nitrate as precursor (CN/SM), calcium oxide was coated on the support SM more uniformly. However, the low melting point of calcium nitrate precursor lead to agglomeration resulting in low catalytic activity after calcination. The catalysts SrO/SM prepared from strontium nitrate by impregnation and precipitation methods lost magnetism easily and exhibited no catalytic capability for transesterification. This maybe attributed to the reactions of Sr and Fe3O4 forming other substances in the calcination process, thus inhibiting the catalytic ability of SrO. The proper operating conditions for manufacturing soybean-oil biodiesel (SOB) are 12:1 molar ratio of methanol to oil (M : O), 6 wt% of catalyst loading relative to oil (MC) and 10 wt% CaO at 338 K (TT) for 7 h (tT). However, CA/SM reusability was not promising with yield declined from 94% to 60% for the second reuse. The main cause may be due to the dissolution of calcium and deposition of organic matter on catalyst surface. Jatropha-oil biodiesel (JOB) was producted by using a two-stage transesterification process, i.e., pre-esterification followed by post transesterification. The transesterification reaction approached equilibrium after 7 h, achirving yield of 90%. Properties of soybean-oil biodiesel (SOB) and jatropha-oil biodiesel (JOB) of acid value, density and cold filter plugging point complies with standards (CNS 15072). However, the water contents are higher than the standard. The water in oil can be removed by distillation or magnesium sulfate. Furthermore the iodine value of SOB and kimetic viscosity of JOB are slightly higher than the standards and can be improved by blending with other biodiesel.