Effect of microwave irradiation on the etherification of biodiesel-derived glycerol in a solvent free process

Abstract

This study revolves mainly about the effect of etherification of glycerol to polyglycerols using a heterogeneous catalyst under microwave radiation. Microwave radiation serves as a purpose to shorten the reaction time of the procedure. Cerium Nitrate and Lithium Nitrate was used to modify montmorillonite K-10 clay (MK-10) which was then used to catalyze the etherification process. They were several reaction parameters that were observed for this study which were: catalyst concentration and reaction time. The parameter that played a vital role was the catalyst concentration which affected the percentage conversion of glycerol, selectivity of pentaglycerols, selectivity of cyclic diglycerols and undesired cyclic diglycerols. It was observed that with a high temperature and high reaction time, the amount of undesired cyclic glycerol was increased. Optimum amount of catalyst conversion promoted higher amount of desired cyclic glycerol. Longer reaction time is needed to produce higher yield and selectivity. The production of undesired cyclic diglycerol can be removed with the help of vacuum distillation. The highest glycerol conversion was found of 94% with highest yield of desired products of 70% polyglycerol at 260 °C and 5 h of reaction time. The selectivity towards undesired high order polyglycerol was found 24% at same reaction conditions.