Synthesis of K+/MgO heterogeneous catalysts derived from MgCO3 for biodiesel production

New basic catalysts were produced by alkali activation of mesoporous MgCO3 using KOH. A crystalline MgO was obtained when the pure amorphous carbonate was heat-treated at 800 degrees 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 degrees 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 MgCO3 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. (C) 2019 Elsevier B.V. All rights reserved.