Amino-Sulfonated Graphene as a Catalyst for Efficient Production of Biodiesel from Fatty Acids and Crude Vegetable Oils.

Climate change and the depletion of fossil fuels increase the demand for sustainable energy. Biodiesel, synthesized with heterogeneous acid catalysts, is a promising chemical carrier of clean energy, adhering to circular carbon economy . Here, we report the particularly effective synthesis of biodiesel using a reusable, solid-state acid graphene catalyst functionalized with a natural aminosulfonic acid. Experimental and theoretical studies unveil the key role of the functionalities containing simultaneously an amino and sulfonate group, ascribing superior acidity. Excellent activity and selectivity for oleic acid conversion to oleic acid methyl esters (a sustainable biofuel) were obtained, offering a strategy for achieving improved catalytic performance compared to earlier or benchmark catalysts in the field. Notably, the catalyst is also highly effective in converting commonly available vegetable oils to biodiesel through trans-esterification, and in carbohydrate dehydration to value-added chemicals, demonstrating its general applicability. Two more variants of aminosulfonic acid‑functionalized graphenes demonstrated very similar activities, validating the key role of such functionalities on the high acidity and activity. The development of such potent, recyclable catalysts is crucial since acid catalysis is arguably the most general and versatile approach for organic reactions, ubiquitous in an extraordinary range of biological and synthetic transformations.