Sulfonated carbon derived from the residue obtained after recovery of essential oil from the leaves of using Brønsted acid ionic liquid, and its use in the preparation of ellagic acid and gallic acid.

A Brønsted acid ionic liquid, 3-methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate ([HOS(CH)mim]HSO), was used for the first time for the preparation of a sulfonated carbon catalyst. The catalyst was prepared from the residue obtained after recovery of the essential oil from the leaves of . The sulfonated carbon catalyst with an amorphous structure attained high acidic efficiency at a sulfonation temperature of 200 °C for 2 h of sulfonation time, and was characterised.