One-step preparation of sulfonated carbon-based solid acid from distillers’ grain for esterification

A carbon-based solid acid catalyst was prepared by simultaneous carbonization and sulfonation of distillers’ grain with concentrated sulfuric acid. Response surface methodology was adopted to determine the optimal preparation conditions such as sulfuric acid concentration, preparation temperature and preparation time. This catalyst was characterized by XRD, FT-IR, TG, XPS, elemental analysis, N2 adsorption/desorption and acid-base titration methods. The catalytic performance was evaluated under a certain condition in the esterification of acetic acid and n-butanol as a probe reaction. The conversion of acetic acid was 97.6% when the sulfuric acid concentration of 85 wt%, preparation temperature of 20 °C, and preparation time of 1.4 h. The high catalytic activity of this catalyst may be attributed to the higher acid density of 1.73 mmol/g by NaOH titration. The catalyst performance will weaken with the increase of reuse times, but it could be regenerated by treatment with concentrated sulfuric acid (85 wt%).