Abstract
BACKGROUND: Catalytic oxidation of toluene with dioxygen is a fundamental industrial technology because the oxidized products are important intermediates for many fine chemicals. In this study, phenyl modification was utilized to alter catalyst surface characteristics in order to enhance activity.
RESULTS: Phenyl groups were successfully immobilized on the surface of Mnโcontaining hexagonal mesoporous silica (HMS) through a oneโstep synthesis route, as demonstrated by detailed characterization. As a result, the surface of the catalyst Ph๏ฃฟMn๏ฃฟHMS was more hydrophobic with a water droplet contact angle of 96ยฐ. In the oxidation of toluene to benzoic acid with dioxygen under solventโfree conditions, this new catalyst showed higher activity and selectivity than nonโorganomodified Mn๏ฃฟHMS, and the conversion and selectivity increased by a factor of 40% and 9%, respectively.
CONCLUSION: Modification of the catalyst surface with phenyl groups was an effective strategy to increase activity in the oxidation of toluene. Both conversion and selectivity were improved and this is linked to the hydrophobic character of the surface. This organic modification strategy may also be extended for oxidation of other hydrocarbons. Copyright ยฉ 2009 Society of Chemical Industry