CoCuAl layered double hydroxides – efficient solid catalysts for the preparation of industrially important fatty epoxides

Abstract

CoCuAl ternary layered double hydroxides (LDHs) with a (Co + Cu)/Al atomic ratio of 3.0 and varying Co/Cu atomic ratios were synthesized by co-precipitation. Catalytic epoxidation of ethyl linoleate was carried out over these materials using aqueous tert-butyl hydroperoxide (70 wt.%) as the oxidant. Co₃₀Cu₇₀Al-LDH (Co : Cu atomic ratio of 30 : 70) showed maximum conversion of 85% with 100% selectivity for epoxide at 110 °C in 4 h. Higher activity of this catalyst was attributed to synergism between cobalt and copper as inferred through physicochemical techniques. The catalyst was reusable six times without significant loss. The study was extended to vegetable oils (edible, non-edible and used cooking oils) and showed 50–70% conversion with 100% selectivity. Comparison of the activity between oils and fatty acid methyl esters (FAME) showed lesser activity for the former probably due to hindered access. The process was successfully scaled up (50 g) for sunflower oil and the physical properties were markedly varied for epoxidized oil, suggesting promise for industrial applications.