Etherification of glycerol with isobutene on sulfonated graphene: reaction and separation

A sulfonated graphene catalyst (SG) prepared by grafting sulfonic acid-containing aryl radicals onto the two-dimensional surface of graphene was used for the etherification of glycerol with isobutene, and a reaction–extraction process was developed for easy realization of product isolation and catalyst recycling. With its ultra thin two-dimensional open substrate, stable sulfonic acid sites, amphiphilic properties and light texture, SG exhibited excellent catalytic performance in the etherification reaction. At 60–70 °C with 4 wt% catalyst loading and a molar ratio of isobutene/glycerol 4, a nearly complete conversion of glycerol in 7 h and a selectivity of more than 90 mol% to desired multi-butyl glycerol ethers were achieved. Moreover, undesired oligomerization of isobutene was successfully suppressed. When extracted with fresh glycerol, the mixture after reaction was successfully layered to two phases, with a transparent liquid containing no less than 96 wt% di- and tri-butyl glycerol ethers in the top phase as a product and a black mixture consisting of glycerol and SG in the bottom phase which can be used to start a new run with fresh isobutene addition. During six consecutive reaction–extraction cycles the catalyst maintained its robust performance.