Alkoxide-intercalated Mg-Al layered double hydroxides as selective catalysts for the synthesis of monoglycerides

A series of magnesium-aluminum layered double hydroxides (MgAl LDHs) intercalated with various alkoxide ions (methoxide, ethoxide, iso-propoxide and tert-butoxide) were prepared via ion exchange and then applied as heterogeneous catalysts in the transesterification of methyl laurate (ML) with glycerol to selectively synthesize monolaurins under batch conditions. The initial reaction rate varied with the alkoxide content of the intercalated LDHs and essentially depended on the molecular size of the alkoxide ions, while the monolaurins yield was determined by the basic strength of the intercalating alkoxide ions. The MgAl LDH intercalated with butoxide ion (t-C4H9O--MgAl LDH) was the most suitable catalyst and exhibited a superior performance to that of the rehydrated MgAl LDH. The highest yield and selectivity of monolaurins (86.6 and 87.3 %, respectively) with a ML conversion of 99.0 % was obtained over t-C4H9O- -MgAl LDH when using a 4 wt% catalyst loading and a 6:1 glycerol: ML molar ratio at 150 A degrees C for 3 h.