Sulfonic acid-functionalized carbon coated red mud as an efficient catalyst for the direct production of 5-HMF from d-glucose under microwave irradiation.

[Display omitted] • Red mud (RM) derived catalyst for the direct glucose conversion to 5-HMF. • Red mud composition provided the suitable Lewis acid sites. • Carbon coating followed by -SO 3 H grafting produced the Bronsted acid sites. • Low reaction time owing to the microwave-induced fast catalytic reaction. • Appreciable activity and stability of the RM-based catalyst. Though suitable for the fructose conversion to 5-hydroxymethylfurfural (5-HMF), sulfonated carbon catalysts are inefficient for the direct glucose transformation to 5-HMF due to the lack of appropriate Lewis acids. Here, we have reported an efficient and inexpensive catalyst by suitably modifying red mud (RM), a by-product from the aluminum industry. The AD-1:1/SO 3 H catalyst produced by the acid (HCl) treatment, carbon coating, and SO 3 H grafting on RM exhibited enhanced surface area, mesoporous characteristics, and suitable Lewis and Bronsted acid sites. The XRD, FTIR, and XPS analysis suggested Fe 2 (SO 4) 3 , Fe 2 O 3 , and various carbon functionalities as the major active components in the AD-1:1/SO 3 H catalyst. The NH 3 -TPD analysis revealed an appreciable acid site density of 6.8 mmol g−1. Under microwave heating at 180 °C, 30 min, and 90:10 DMSO/water weight percentage ratio, the catalyst produced a d -glucose conversion and 5-HMF yield of 93.05 % and 51.5 %, respectively. [ABSTRACT FROM AUTHOR]