Excellent product selectivity towards 2-phenyl-acetaldehyde and styrene oxide using manganese oxide and cobalt oxide NPs for the selective oxidation of styrene

• Published in: Applied catalysis. A, General General, 2018-06, Vol.559, p.175-186
• Main Authors: Masunga, Ngonidzashe, Doyle, Bryan P., Carleschi, Emanuela, Meijboom, Reinout
• Format: Article
• Language: English
• Subjects: 2-Phenyl-acetaldehyde; Catalysis; Catalysts; Chemical synthesis; Cobalt; Cobalt oxide nanoparticles; Cobalt oxides; Hydrogen peroxide; Manganese compounds; Manganese dioxide; Manganese oxide nanoparticles; Mesoporous metal oxides; Metal oxides; Nanoparticles; Oxidation; Phenylacetaldehyde; Recyclability; Selectivity; Styrene oxidation; Styrene oxide; Styrenes; X ray photoelectron spectroscopy
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.04.027

[Display omitted] •Metal oxide nanoparticles were synthesized and immobilized on mesoporous metal oxide.•High catalytic activities were obtained during styrene oxidation.•Excellent selectivity towards styrene oxide was obtained using Co3O4 NPs.•MnOx NPs gave higher selectivity towards 2-phenyl-acetaldyde.•Catalyst recycles tests and other variables were investigated. MnOx and Co3O4 nanoparticles (NPs) were synthesized using the temperature controlled co-precipitation method and were immobilized on the mesoporous metal oxide supports that were synthesized using the inverse surfactant micelle method. The synthesized catalysts were characterized using TEM, SEM, pXRD, N2-sorption, XPS, and H2-TPR. From TEM the well-dispersed metal oxide NPs were observed and the interaction of the NPs with the support was confirmed with H2-TPR. These metal oxide NPs and immobilized metal oxide NPs were employed in the selective oxidation of styrene using tert-butyl hydrogen peroxide (TBHP) as an oxidant. Higher selectivity towards styrene oxide was obtained using Co3O4 NPs. MnOx NPs gave higher selectivity towards 2-phenyl-acetaldehyde while the immobilized metal oxide NPs gave a mixture of products. The catalytic activities of the compared catalysts followed the following decreasing order of MnOx NPs (646.9 h−1) > Co3O4 NPs (338.1 h−1) > Co-MnO2_350 (54.1 h−1) > Mn-Co3O4_350 (44.1 h−1) ˃ MnO2_350 (35.8 h−1) > Co3O4_350 (21.3 h−1) after 8 h of reaction. The catalytic activities and selectivity profiles under various reaction conditions such as solvent type, catalyst amount, styrene to TBHP ratio and temperature are discussed. The catalytic recyclability of immobilized metal oxide NPs on mesoporous metal oxides showed that they are stable, and the structure of the catalyst was retained.