Biphasic Phase-Transfer Catalysis: Epoxidation of Vegetable Oils by Surface Active Ionic Liquids in Water

Abstract

Vegetable oils (VOs) are an environmentally benign alternative and sustainable carbon feedstock for various industrially relevant compounds, e.g. the epoxidized products (EVOs). The commercial production of EVOs is a heterogeneous liquid-liquid reaction with low reaction rates and a limited epoxide selectivity. Furthermore, the separation of the EVOs from the reaction mixture is very intricate, limiting a large-scale applicability. In this work, we introduce surface-active imidazolium tungstate ionic liquids (SAILs) as sustainable catalysts for the epoxidation of VOs in water using hydrogen peroxide as green oxidant. Micelle formation and substrate uptake into the aqueous phase depend on the nature of the cation of the SAIL catalyst, studied by dynamic light scattering (DLS), transmission electron microscopy (TEM) and cryo-TEM at various concentrations and temperatures. Recycling studies demonstrate that the catalyst remains in the aqueous phase and can be recovered completely. The absence of catalyst and additive in the product phase is verified by inductively coupled plasma mass spectrometry (ICP-MS) and 31P-NMR spectroscopy.