Unusual Oxidation Behaviour of Mesoporous Silicates towards Lignin Model Phenolic Monomer

Abstract

Oxidation of the lignin model monomer apocynol, 1-(4-hydroxy-3-methoxyphenoxy)-ethanol catalysed by mesoporous silica catalysts i.e. MCM-41, MCM-48, SBA-15 using H2O2 as an oxidant has been studied. Selectively, 2-methoxybenzoquinone was obtained along with acetovanillone. Such unprecedented oxidation behaviour of these metal free siliceous catalysts is attributed to the polar internal surface, high surface area as well as the pore architecture. On the other hand, the studied reaction was found to be non-selective when a commercial grade mesoporous silica i.e. Silica-5 was used as catalyst for comparison. Among the various silica catalysts studied, MCMs gave highest conversion and selectivity towards 2-methoxybenzoquinone under very mild reaction conditions.