Selective synthesis of glycerol monolaurate with zeolitic molecular sieves

The purpose of this work, is to study the selective synthesis of glycerol monolaurate from lauric acid and glycerol as starting materials, employing commercial Beta, Y and Mordenite zeolites with different Si/Al ratio as catalysts. Reaction conditions such as the stirring rate, temperature, glycerol/lauric acid ratio and catalyst mass in the reaction medium were optimized to diminish homogeneous reaction and reaction limitations due to diffusive effects. In the case of zeolite Y, an increase in glycerol monolaurate yield and selectivity for the monoester were verified at high Si/Al ratio. This behavior seems to be related to the presence of stronger acid sites present in the material with low Al content and probably also because of the higher hydrophobicity exhibited by zeolites having higher Si/Al ratio. Mordenite catalyst, on the contrary, presented low activity and selectivity to glycerol monolaurate, which can be attributed to the diffusional limitations imposes by the monodimensional channel system to the organic substrate accessing the inner catalyst sites, restricting the reaction to the sites present at the external particle surface. Zeolite Beta exhibited the best results as catalyst to obtain the mono-derivative, presenting selectivities higher than 60% at 20% yield. (C) 2000 Elsevier Science B.V. All rights reserved.