The fabrication of carbon-shell protected cobalt nanoparticles and hollow graphitic shells has been achieved via a pyrolysis process by using monodispersed cobalt nanoparticles as a template. These materials are mesoporous and highly stable under strong acidic and basic conditions.
Aromatic
alcohols are essential components of many solvents, coatings,
plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing
processes involving the oxidation of petroleum-derived aromatic hydrocarbons
suffer from low selectivity due to facile overoxidation reactions
which produce aromatic aldehydes, acids, and esters. Here we report
a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol
directly to methylbenzyl alcohols (MB–OH, predominantly 2-MB–OH)
at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which
is catalyzed by Co2+, has the highest reaction barrier.
Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms
the key intermediate, 2-butenal, which yields aromatic aldehydes through
self-condensation and then MB–OH via hydrogenation. In the
presence of Co2+, 2-butenal is selectively hydrogenated
to 2-butenol. This reaction does not hinder aromatization because
cross-coupling between 2-butenal and 2-butenol leads directly to MB–OH
without passing through MBO. Using these insights a dual-bed
catalyst configuration was designed for use in a single reactor to
improve the aromatic alcohol selectivity. Its successful use supports
the proposed reaction mechanism.
SummaryMagnetic γ-Fe2O3 nanoparticles with a mean diameter of 20 nm and size distribution of 7% were chemically synthesized and spin-coated on top of a Si-substrate. As a result, the particles self-assembled into a monolayer with hexagonal close-packed order. Subsequently, the nanoparticle array was coated with a Co layer of 20 nm thickness. The magnetic properties of this composite nanoparticle/thin film system were investigated by magnetometry and related to high-resolution transmission electron microscopy studies. Herein three systems were compared: i.e. a reference sample with only the particle monolayer, a composite system where the particle array was ion-milled prior to the deposition of a thin Co film on top, and a similar composite system but without ion-milling. The nanoparticle array showed a collective super-spin behavior due to dipolar interparticle coupling. In the composite system, we observed a decoupling into two nanoparticle subsystems. In the ion-milled system, the nanoparticle layer served as a magnetic flux guide as observed by magnetic force microscopy. Moreover, an exchange bias effect was found, which is likely to be due to oxygen exchange between the iron oxide and the Co layer, and thus forming of an antiferromagnetic CoO layer at the γ-Fe2O3/Co interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.