Biofuels From Glycerol By Etherification: Suitable Bio-Oalkylant Agents, Solid-Acid Catalysts And Technologies To Achieve High Yields To Poly-Ethers

Recent growth in biodiesel production by transesterification reaction has produced a significant surplus of glycerol, it being the main byproduct of such process, thus destabilizing the market and making necessary to find new glycerol applications to support the eco-sustainability of the global process of biomass transformation. An appealing strategy is represented by the transformation of glycerol into oxygenated fuel additives to gain benefits both in terms of environmental compliance and efficiency of diesel engines. Etherification of glycerol in presence of an O-alkylant agent, like isobutene (IB), leads to a mixture of tert-butylglycerol ethers, but only poly-ethers are suitable additives due to their good miscibility with diesel. In presence of tert-butyl alcohol (TBA), to overcome thermodynamic constraints related to the water formation, the use of a proper catalyst based on Hyflon ionomer and a permselective membrane coupled with a batch reactor allows to reach a poly-ethers yield of about 80%, a value threefold higher than that reported in literature. The use of bio-ethanol or bio-butanol which are renewable reactants could be an interesting alternative to valorize derived glycerol. Anyway, they are less activated alcohols than TBA, thus the reaction results to be thermodynamically more difficult.