Efficient and Highly Selective Production of 5-Hydroxymethylfurfural (HMF) from Fructose Using Hybrid Ce-Al Oxide Catalysts: Probing the Role of Calcination Temperature and Crystallinity of Catalyst

The current work demonstrates the fabrication of cerium-aluminum oxide (CAO) catalysts for the dehydration of fructose to the platform chemical 5-hydroxymethylfurfural (5-HMF). CAO materials with varying chemical compositions and textural properties were obtained through calcination at different temperatures. The fructose conversion and yield of 5-HMF of the catalysts were determined in a dimethyl sulfoxide system. The CAO catalysts were thoroughly characterized, and their catalytic performances evaluated to uncover the origins of their fructose conversion efficiency and product selectivity. The CAO catalyst obtained by calcination at 500 °C (CAO-500) registered remarkably high fructose conversions (~ 95%) and 5-HMF yields (~ 91%) with no side product generation which means that under the optimal process conditions (120 °C, 120 min) determined in the study, the catalyst produces 5-HMF almost exclusively. The exceptional catalytic performance of CAO-500 was intimately linked to the physical and chemical synergies emerging from the co-existence of crystalline (CeO₂) and amorphous (Al(OH)₃) components in its matrix resulting from the calcination process. This unique composition makes CAO-500 structurally robust and with the necessary abundance of Lewis and Bronsted acid sites that facilitate highly selective fructose conversion to 5-HMF.