Nanocatalysis in continuous flow: supported iron oxide nanoparticles for the heterogeneous aerobic oxidation of benzyl alcohol

Abstract

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.

Important Industrial Procedures Revisited in Flow: Very Efficient Oxidation and N-Alkylation Reactions with High Atom-Economy

“…The reaction mixture is then cooled through a heat exchanger before eluting into a collection vessel. Reaction coils and cartridges for solid supported materials are available in various sizes [32]. The mixture was analyzed with GC-MS. HCl in dioxane was added to the solution, and it was stirred for an hour.…”

“…The H-Cube Pro™ can be linked with Gas Module [16]. Another application using molecular oxygen as oxidant will be reported elsewhere [32].…”

“…We started to investigate other commercial catalysts in the CatCart™ [32] system (the entire list is provided in the Supplementary Material). Based on literature references, 14 catalysts were screened including 4-6 conditions for each CatCart™.…”

Charge effect of superparamagnetic iron oxide nanoparticles on their surface functionalization by photo-initiated chemical vapour deposition

“…Among many applications, superparamagnetic nanosystems can be used for magnetic data storage (Eigler et al 2014), polluting agent removal (Nethaji et al 2013), or, more recently as catalysts for organic reactions (Gawande et al 2013, Obermayer et al 2013. Beside these numerous applications, SPIONs are widely used nanomaterials for biomedical purposes, such as magnetic resonance imaging (MRI) , hyperthermia for cancer therapy (Jin et al 2008), cell targeting (Das et al 2008), drugs or gene delivery (Namvari and Namazi 2014).…”

Crystalline-phase-dependent catalytic performance of MnO2 for aerobic oxidation reactions

“…However, many conventional reactions require oxidants such as chromium trioxide (i.e., the Sarret reagent) or oxalyl chloride, which are dangerously toxic and lead to the formation of large amounts of byproducts [19][20][21]. Therefore, intense efforts have been devoted to developing efficient heterogeneous catalysts that employ molecular oxygen as the primary oxidant in order to meet the requirements of green synthesis [14][15][16]18,[22][23][24][25][26][27].…”