Greener Epoxidation Reaction of Macaw Palm Oil Using Metal Oxides and Niobium Phosphate as Catalysts

The present work focused on the screening process of different inorganic oxides and different temperatures for the epoxidation reaction of macaw palm vegetable oil without using solvent, a promising Brazilian biomass that can substitute other vegetable oils (e.g., soybean oil) in technological applications. This oil has an iodine value of 108.48 g of I₂ per 100 g being categorized as a semi-dry oil. The epoxidized vegetable oil can be applied in manifold areas in polymer science. The epoxidation reaction here presented avoided organic solvents and organic acids and aimed to produce a greener route using metal oxides or niobium phosphate as a peroxide-activating catalyst. The experimental parameters were maintained as 10 mol% of catalyst loading and a time of 24 h; however, the temperature for some catalysts was changed to improve the epoxide conversion. Experiments were measured by proton nuclear magnetic resonance (¹H NMR). Experiments using titanium oxide (TiO₂) as a catalyst reached a conversion greater than 84.7%, while experiments using aluminium oxide (Al₂O₃) or lanthanum oxide (La₂O₃) achieved conversions of 22.6 and 30.1%, respectively. Furthermore, it was observed that both niobium compounds instantly react with hydrogen peroxide to form peroxy derivatives.

Keywords:
green chemistry; metal oxide; epoxidation; Acrocomia aculeata; renewable monomer