Preparation of a Carbon-Based Solid Acid Catalyst by Sulfonating Activated Carbon in a Chemical Reduction Process

摘要

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.