Tailoring the catalytic performance of sol-gel encapsulated tetra n-propylammonium perruthanate (TPAP) in aerobic oxidation of alcohols

Sol-gel nanohybrid silica particles organically modified and doped with the ruthenium species tetra-n-propylammonium perruthenate (TPAP) are highly efficient catalysts for the selective oxidation of alcohols to carbonyls with O2 at low pressure in toluene. The materials are easily prepared by a one-step sol-gel process and their catalytic performance can be optimised tailoring the conditions of their synthesis by hydrolytic co-polycondensation of tetramethoxysilane (TMOS) and alkyltrimethoxysilanes R-Si(OMe)3 in the presence of TPAP. Eventually, heterogeneous catalysts are obtained that are considerably more active than the unsupported perruthenate while being leach-proof and recyclable. The correlation between the materials activity, surface polarity and textural properties suggests valuable information on the chemical behaviour of sol-gel catalytic materials in oxidation catalysis which is of relevant interest considering the importance of efficient solid catalysts for the selective oxidation of alcohols with O2.