Reusable TsOH-HSO Mixed Catalysis for Tandem Synthesis of Biodiesel and Oxygenated Fuel Additives, tert-Butyl Glycerol Ethers.

A mixture of p-toluenesulfonic acid and sulfuric acid (TsOH-HSO) was used as a catalyst with a good performance in transesterification of palm oil (PO) with methanol and etherification of crude glycerol with isobutylene (tandem synthesis). For TsOH-HSO catalyzed biodiesel production, the reaction noticeably ran faster in comparison with TsOH or HSO alone and also gave up to 99.9% of the conversion using MeOH/PO molar ratio 9:1 at 80℃, in the period of 4 h. After the whole transesterification process, the crude glycerol phase was separated and then reacted with isobutylene in the etherification process using isobutylene/glycerol molar ratio 9:1 at 80℃, in the period of 5 h reaction time, to give DTBG and TTBG (91.14%). In the case of the etherification in biodiesel, higher selectivity of DTBG and TTBG (99.39%) was obtained in comparison with an absence of biodiesel as the solvent. Furthermore, the catalyst could be reused for 6 cycles of tandem synthesis (transesterification and etherification). The TsOH-HSO catalyst showed a good catalytic performance in tandem synthesis similar to TsOH and it could be recovered for reuse while TsOH could not be recovered. This process offers an attractive route for reuse homogeneous catalyst of tandem synthesis, the main by-product of biodiesel, to tert-butyl glycerol ethers - a value-added in applications as a valuable fuel additive.