Abstract
Sulfonated (SO3H-bearing) activated carbon (AC-SO3H) was synthesized by an aryl diazonium salt reduction process. The obtained material had a SO3H density of 0.64 mmol·g−1 and a specific surface area of 602 m2·g−1. The catalytic properties of AC-SO3H were compared with that of two commercial solid acid catalysts, Nafion NR50 and Amberlyst-15. In a 10-h esterification reaction of acetic acid with ethanol, the acid conversion with AC-SO3H (78%) was lower than that of Amberlyst-15 (86%), which could be attributed to the fact that the SO3H density of the sulfonated carbon was lower than that of Amberlyst-15 (4.60 mmol·g−1). However, AC-SO3H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acid and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon. The disadvantage of AC-SO3H is the leaching of SO3H group during the reactions.
Highlights
IntroductionSulfonated (SO3H-bearing) carbon materials have been reported to act as strong solid acid catalysts
Sulfonated (SO3H-bearing) carbon materials have been reported to act as strong solid acid catalysts.Hara’s group first prepared sulfonated carbon catalysts via the sulfonation and carbonization of polycyclic aromatic hydrocarbons [1]
There is no noticeable difference in the XRD patterns between Activated carbon (AC) and AC-SO3H, suggesting that the chemical reduction process does not affect the microstructure of carbon materials
Summary
Sulfonated (SO3H-bearing) carbon materials have been reported to act as strong solid acid catalysts. Hara’s group first prepared sulfonated carbon catalysts via the sulfonation and carbonization of polycyclic aromatic hydrocarbons [1] These catalysts showed excellent activity in a series of acidcatalyzed reactions, they were not stable enough and the aromatic molecules leached out above 100 oC [2]. The controlled carbonization and sulfonation of these materials resulted in stable carbon structures with a high SO3H group density. Another paper from Hara’s group described the preparation of a porous sulfonated carbon catalyst with high specific surface area by carbonization and sulfonation of ZnCl2-impregnated wood powders [15]. Feng et al reported the preparation of carbon-based solid acid catalysts by covalent attachment of SO3H radicals on the surface of ordered mesoporous carbon in a chemical reduction process [17,18]. The structure and catalytic properties of the obtained material were examined
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