Synthesis of K + /MgO heterogeneous catalysts derived from MgCO 3 for biodiesel production

Abstract

New basic catalysts were produced by alkali activation of mesoporous MgCO 3 using KOH. A crystalline MgO was obtained when the pure amorphous carbonate was heat-treated at 800 °C, meanwhile a material formed by a mixture of crystalline structures containing K and Mg was obtained when 50 wt% KOH was added to the mesoporous carbonate before heating. The solid reordering was confirmed by XRD, FTIR and N 2 adsorption-desorption porosimetry measurements. The catalytic activity of the samples was tested for the transesterification of sunflower oil with methanol for FAME production. The reactions were carried out at 65 °C, with a methanol: oil weight ratio of 3:10 and a catalyst concentration of 3 wt% referred to the oil weight. The original mesoporous carbonate showed no catalytic activity, while the MgO obtained by MgCO 3 heating reached 45% conversion after 15 h of reaction time. Interesting results were obtained using the K-doped sample, which attained 98% oil conversion in 30 min. The K catalyst was recovered and reused, giving 50% oil conversion after 120 min of reaction time.