Researches on biofuels have attracted more and more attention from all around the world. While the increasingly serious environmental problems caused by the burning of fossil fuels also make the development of biofuels imminent. Currently, little work about bifunctional magnetic solid acid catalysts with both Lewis and Brønsted acid sites for biodiesel production is reported because the balance of the magnetism and activity of the catalyst is very difficult to control. So, new catalyst synthesis methods and suitable materials are very required to develop.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted production of biodiesel experiments in a sealed glass bottle for esterification and micro autoclave for transesterification. They aimed to directly produce biodiesel or pretreat raw oils with high acid value (AV) by synthesizing magnetic solid acid catalysts with high acidity and strong magnetism through loading bothLewis and Brønsted acid sites, as well as magnetic particles in a carbonaceous support.
They optimized reaction variables for biodiesel production by single-factor and orthogonal experiments. They characterized catalysts before and after reaction by various analytic techniques.
Biodiesel production via esterification or transesterification reaction can be successfully catalyzed by the synthesized magnetic Zr-CMC-SO3H@3Fe-C400 catalyst. The catalyst was active to produce biodiesel by esterification with maximum yield of 97.39% at 90 °C and was easily separated by a magnet for ten cycles (biodiesel yield > 90%) if regeneration step was applied.
For transesterification reaction, biodiesel yield could reach 95.40% from high AV oils. Catalyst had very high activity on pretreatment of high AV Jatropha oil with five cycles (AV reduced to 1.64 mg KOH/g).