Effects of Ce/Ca/Mg-compound supports on KF catalyst and reaction kinetics of ethylene carbonate transesterification

Abstract

Heterogeneous catalysts can avoid the problem of difficult separation and recovery of homogeneous catalysts in transesterification reactions, but there is a lack of basis for process optimization because the quantitative influence mechanism of supports is not clear. In this work, we firstly attempt to make a comprehensive comparation on the effect of potassium fluoride (KF) catalysts on various supports (carbonates and oxides of cerium, magnesium and calcium) on the transesterification reaction, especially on the kinetics. According to the results, oxide-supported catalysts are significantly more active than carbonate-supported catalysts because they have more active sites. When oxides were used as supports, KF/MgO exhibited good activity because of its stronger basicity and higher number of active sites on the surface. Under the same process conditions, the stability time of KF/CeO₂, KF/CaO and KF/MgO catalysed transesterification reaction was 240 min, 90 min and 30 min, respectively. KF/MgO achieved a conversion of 68.0 %. The activation energies of the KF/CeO₂, KF/CaO and KF/MgO catalysed transesterification reaction were 22.22 kJ/mol, 15.93 kJ/mol and 15.80 kJ/mol, respectively. The surface alkalinity of KF/MgO increased the frequency of molecular collisions of the reactants and exhibited a faster reaction rate.