Nickel “hairy” foam,
consisting of carbon nanofibers
(CNFs) grown on the surface of nickel foam, were synthesized and tested
for nitrite hydrogenation. The results showed that nickel “hairy”
foam is catalytically active in the absence of any noble metal, which
is attributed to the formation of nickel particles with high carbon
content during CNF growth. These C-doped nickel particles showed catalytic
properties similar to those of noble metals, but were easily deactivated
as a result of oxidation treatments. This deactivation is partially
attributed to nickel passivation, which is reversible by reducing
with H2 at room temperature in the gas or liquid phase.
In addition, oxidation treatment also caused partial removal of the
carbon dissolved in the nickel particles, causing irreversible deactivation.
Increasing severity of the oxidation treatment induced slower reactivation
via reduction, as well as lower steady-state activities after reactivation.
This irreversible deactivation is attributed to the decreased concentration
of dissolved carbon. Therefore, nickel “hairy” foam
is a promising hydrogenation catalyst, provided it is protected against
oxygen.
Nitrite hydrogenation is studied in steady‐state as well as transient operation using a Pd catalyst in a tubular membrane contactor reactor. A negative reaction order in hydrogen in steady state operation proofs that hydrogen and nitrite adsorb competitively. In transient operation, feeding nitrite to the Pd surface fully covered with hydrogen results initially in very low conversion of nitrite, speeding up once hydrogen is removed from part of the Pd surface. Additional proof for competitive adsorption between hydrogen and nitrite is provided by the observation that exposure of a nitrite‐covered catalyst to hydrogen induces desorption of nitrite. Formation of ammonia in these experiments proceeds via two pathways, first via a fast reaction followed by extremely slow hydrogenation of adsorbed N atoms, which is kinetically not relevant. This information is relevant for designing effective and selective catalysts when operating at very low nitrite concentration.
H2O2 decomposition experiments on Pt were performed in a glass microreactor, simulating arrays of catalyst pores. Both suppression as well as enhancement of the catalytic reaction is observed.
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.