Recoverable aqueous-ionic liquid biphasic catalyst system for the oxidation of n-octane

This study seeks to address the need for the development of highly active paraffin activation catalysts that are reusable and based on cheap earth abundant metals. Hence, a series of related halide-free 1,3,4-trisubstituted-1,2,3-triazolium ionic liquids (IL)(3a-3f) bearing a variety of substituents were synthesized and fully characterized by spectroscopic and analytical techniques. Crystal structure of the halide derivative, compound 2f is also reported. With the IL as solvents for the dissolution of FeCl2, FeCl3, CoCl2, and NiCl2, a series of catalyst systems were developed and used to activate the catalytic oxidation of n-octane in the presence of H2O2 as the oxidant in a biphasic IL/H2O system. All systems tested were found to be active under optimum conditions yielding oxygenated products (mainly octanones). The role of the substituents around the triazole ring was to influence catalytic efficiency in terms of conversion of the substrate n-octane and selectivity to oxygenated products (octanols, octanal, octanones, and octanoic acid). In a test for recyclability, recovered IL dissolved catalysts were found to be effective up to three cycles without any significant loss of catalytic activity before leaching to the aqueous phase resulted in loss of activity.