Mesoporous activated carbon from sunflower shells modified with sulfonic acid groups as solid acid catalyst for itaconic acid esterification.

[Display omitted] • Mesoporous activated carbon from sunflower shells was obtained (SAC). • SAC was modified with different amount sulfonic acid groups (SO 3 H). • The acid strength and the number of acid sites increased with the SO 3 H content. • They were tested as catalyst in the esterification of itaconic acid with ethanol. • SACSO3H-20 and SACSO3H-15 catalysts were very active and led to very good yields. Mesoporous activated carbon from sunflower shells (SAC) modified with sulfonic acid groups (SACSO 3 H-XX) was synthesized by grafting the sulfonic groups on the carbon surface to produce novel heterogeneous and reusable solid acid catalysts. The mesoporous carbon was prepared by chemical (H 3 PO 4) and thermal (600 °C) activation of sunflower seed shells. Four materials with increasing SO 3 H content (SACSO 3 H-5, SACSO 3 H-10, SACSO 3 H-15, and SACSO 3 H-20) were obtained using rising chlorosulfonic acid:SAC ratios. They were texturally and physicochemically characterized by SEM-EDX, BET, FT-IR, and TGA-DSC. Potentiometric titration with n-butylamine technique was used to evaluate their acidic properties. The results showed that both the acid strength and the number of acid sites increased with the SO 3 H content in the SACSO 3 H-XX samples. The FT-IR spectra of SACSO 3 H-XX samples confirmed the successful functionalization of SAC with the sulfonic acid group. TGA-DSC diagrams of SACSO 3 H-20 showed that the elimination of the sulfonic groups takes place in the range 250–350 °C. The activity and selectivity of SACSO 3 H-XX in the esterification reaction of itaconic acid with absolute ethanol to form the diester derivative depended strongly on their acidic properties. Furthermore, the effective separation of the product combined with the use of a recyclable catalyst resulted in a clean and environmentally friendly strategy for the synthesis of diethyl itaconate, a bioproduct of relevance to the biorefinery industry. [ABSTRACT FROM AUTHOR]