Sulfonated graphenes: Efficient solid acid catalyst for the glycerol valorization

Abstract

Heterogeneous acid catalysts were obtained based on the functionalization of reduced graphene oxide. The synthesis involves i) the obtaining of graphene oxide by the modified Hummers method ii) the reduction of graphene oxide by three different routes, through the use of hydrazine dihydrochloride, Zn/HCl and ascorbic acid, and iii) the grafting of sulfonic groups in the surface of graphene oxides with 4-diazonium benzenesulfonate. These solids were characterized and evaluated in the etherification of glycerol with tert-butyl alcohol, finding in general glycerol conversions higher than those obtained with a sulfonic resin (Amberlyst® 15). In addition, the selectivity depends on the reduction route used to obtain the catalyst; A larger amount of oxygen groups remaining after the reduction, helps the formation of poly-substituted ethers. These solids also showed stability in their use, converting them into highly efficient catalysts in the valorization of glycerol.