CaO-loaded alginate capsule modified with silane coupling agents for transesterification of rapeseed oil with methanol

The methanolysis of rapeseed oil to fatty acid methyl esters (FAME) using CaO-loaded alginate capsules modified with silane coupling agents is reported. A FAME yield of 87% was obtained with CaO-loaded alginate capsules after 6 h at 333 K. However, capsule breakage reached 18.8% after the first run. In contrast, the breakage was reduced to 2.6% by extra alginate shells modified with n-butyltrimethoxysilane. Consequently, the amount of Ca leaching into the FAME phase was decreased substantially, whereas the reaction induction and completion times were increased. Static diffusion experiments and analyses of the liquid phases inside and outside the capsules at each time interval indicated that the permeability of methanol is the most important factor for determining the induction and completion times.