Selective oxidation of benzyl alcohol to benzaldehyde over Co-metalloporphyrin supported on silica nanoparticles

Heterogenation of the metalloporhyrin ligand, [tetrakis(o-chlorophenyl)porphyrinato]Co(11) was effected by immobilizing the complex onto inorganic silica support to form spherical nanoparticles of RHAC-CoPor. This insoluble mesoporous hybrid showed a high specific surface area of 114 m(2) g(-1) and a pore volume of 0.177 cm(3) g(-1). The prepared catalyst possessed a narrow pore size distribution centered at around 4.17 nm. The C-13 MAS NMR showed that RHAC-CoPor had three chemical shifts at 12.60, 26.60 and 45.18 ppm consistent with the three carbon atoms of the propyl group and a series of chemical shifts in the range of delta= 108-167 ppm consistent with the presence of the metalloporphyrin complex. Elemental analysis showed the successful immobilization of metalloporphyrin complex onto functionalized RHA silica support. RHAC-CoPor appeared to be an active catalyst in the oxidation of benzyl alcohol, producing 97.1% conversion and 97.7% selectivity for benzaldehyde under an ambient temperature of 70 degrees C. RHAC-CoPor could be regenerated and reused several times by washing with water, followed by drying at 100 degrees C. (C) 2012 Elsevier B.V. All rights reserved.