Scheme 4.4 Steps for the formation of TAG using SO3H-C derived from glycerol [30].
Malaika and co-workers have prepared SO3H-modified carbon xerogels and spheres using glucose as a carbon source. These catalysts were explored for acetylation of glycerol and the optimum catalyst shows 75% selectivity for both diacetin (DA) and triacetin (TA), and almost complete glycerol conversion (About 97%). The results are comparable with commercially available ion exchange resin (Amberlyst 15) [26].
Ellis and coworkers have investigated the use of sulfonated carbon catalysts for transesterification and esterification reactions of glycerol. The active catalyst was synthesized by pyrolysis and sulfonation of the sugar char in a tube furnace. The reaction of glycerol with tert-butanol over sulfonated carbon leads to the formation of mono-glyceryl ethers isomers and di-glyceryl ether isomers [33].
Khayoon et al. have explored the potential of sulfated activated carbon catalysts (AC-SA5) for the transformation of glycerol into oxygenated fuel additives by glycerol acetylation. The AC-SA5 was prepared by functionalization of activated carbon with sulfuric acid by hydrothermal method. The catalyst shows 92% of the glycerol conversion into mono, di, and triacetyl glyceride