Christian Doppler Laboratory for Microwave Chemistry (CDLMC) and Institute of Chemistry, Karl-Franzens-Unwersity Qraz, Heinrichstrasse 28, A-8010 Graz, Austria.;Departamento de Quimica Organica, Universidad de Cordoba, Edificio Marie-Curie (C-3), Campus de Rabanales, Ctra. Nnal IV-A, Km 396, E14014 Cordoba, Spain.;Departamento de Quimica Organica, Universidad de Cordoba, Edificio Marie-Curie (C-3), Campus de Rabanales, Ctra. Nnal IV-A, Km 396, E14014 Cordoba, Spain.;
David Obermayer;Alina M. Balu;Antonio A. Romero;
Investigations on heterogeneous iron catalysis in the selective aerobic oxidation of a primary alcohol are presented. Continuous flow technology was used in combination with an iron oxide nanoparticle catalyst stabilized in a mesoporous aluminosilicate support ("flow nanocatalysis") as a process intensification tool to maximize catalyst efficiency. Using 5 mol% 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a co-catalyst, up to 42% benzyl alcohol as a simple model substrate was selectively converted to benzaldehyde in a single pass of the reactor. Full conversion was achieved by continuous recirculation, simulating an extension of the catalyst bed. ICPMS analysis indicated that the catalyst is highly stable and does not leach under the investigated conditions, providing solid evidence for the participation of a heterogeneous iron species in the catalytic cycle.