Mechanochemical synthesis of supported cobalt oxide nanoparticles on mesoporous materials as versatile bifunctional catalysts

Abstract

Supported Co3O4 nanoparticles on SBA-15 aluminosilicates (Al-SBA-15) with different cobalt loadings (0.5, 1, 5, 10 wt %) were synthesized by ball-milling. The synthesized materials were characterized by different techniques including, N2 adsorption measurements, XRD, TEM, EDX, ICP-MS, DRIFTs of pyridine among others. The catalysts were studied in the microwave assisted benzyl alcohol oxidation as well as in the akylation of toluene with benzyl chloride. Co3O4 catalysts exhibited moderate conversions in the selective oxidation of benzyl alcohol, with a high selectivity towards benzaldehyde. Lewis acidity increases upon the incorporation of cobalt nanoparticles onto the surface of the support which was found to significantly influence the materials in the alkylation of toluene with benzyl chloride. The high active sites accessibility of ball-milling prepared materials leads to high conversions to alkylated derivatives in short periods of time (>99 mol %, 30 min). A direct correlation acidity/activity could not be obtained in the systems, for which nanoparticle sizes and distribution could influence the observed activities.