Preparation of a sulfonated activated carbon fiber catalyst with γ-irradiation-induced grafting method

A sulfonated activated carbon fiber catalyst (SACF) was prepared through γ-irradiation-induced grafting of styrene onto the surface of activated carbon fiber (ACF) with an irradiation dose of 0.837 kGy/h for 48 h that was then sulfonated with chlorosulfonic acid under mild reaction conditions. Scanning electron microscopy observation showed that the ACF was wrapped by a thin layer of copolymer, and Fourier transfer infrared spectroscopy analysis indicated that sulfonic acid groups were successfully introduced onto the ACF. Pore structure analysis based on nitrogen adsorption isotherms at 77 K demonstrated that pore parameters of ACF were well maintained after the process of grafting and sulfonation modification. Proper conditions for the SACF preparation were sulfonated at 80 °C for 1.5 h in the 20% mass percentage of chlorosulfonic acid solution using ACF precursor, whose acid density could reach 1.47 mmol/g. The sulfonated ACF was used as catalyst for the esterification of acetic acid and ethanol. Evaluation of the catalytic activity of SACF showed evident advantages over other typical catalyst, with a turnover frequency value of 0.780 min−1, about five times higher than Nafion.