A new environmentally friendly method for the production of 2,3,5-trimethyl-p-benzoquinone

A new environmentally friendly method for the production of 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, Vitamin E precursor) based on the oxidation of 2,3,6-trimethylphenol (TMP) with aqueous H2O2 over various Ti-containing mesoporous silicate materials is reported. Both well-organized Ti-containing mesoporous mesophase silicate (Ti-MMM), having hexagonal arrangement of uniform mesopores, and amorphous TiO2-SiO2 mixed oxides (aerogels and xerogels) produced TMBQ with good to high yield. All the materials studied have been proved to operate as truly heterogeneous catalysts. No titanium leaching occurred from the solid matrixes during the oxidation process. Titanium dispersion and its accessibility were found to be crucial factors determining the catalytic properties. For samples with similar titanium loading, both the catalytic activity and TMBQ yield appeared to fall in the order TiO2-SiO2 aerogel > Ti-MMM > TiO2-SiO2 xerogel and correlate with average mesopore diameter and mesopore volume. The best results (96-98% selectivity to TMBQ at 99-100% TMP conversion) were obtained with TiO2-SiO2 aerogels, containing 1.7-6.5 wt.% Ti. (C) 2002 Elsevier Science B.V. All rights reserved.