A simple strategy for the preparation of chlorine functionalized coal-based solid acid with rich carboxyl to improve the activity for hydrolysis of cellulose

Abstract In order to solve the problem that loading chlorine could reduce the density of -SO3H group and inhibit the increase of catalytic activity, three strategies were adopted to realize the simultaneous chlorination and oxidation modification of carbon-based solid acid, using cheap and easily available NaClO and highly reactive coal as raw materials. The results show that the involvement of NaClO changes the structure of coal-based solid acid from three aspects: loading of chlorine, increase of −COOH group and improvement of aromaticity. It is worth mentioning that −COOH group plays a dual role in both adsorption and hydrolysis, which has a compensation effect on -SO3H group and -Cl group. The structural improvement prominently enhances the hydrolysis of cellulose. Moreover, −COOH group and -Cl group with induced effect can significantly improve the stability of solid acid.