An In Situ TEM Study of the Influence of Water Vapor on Reduction of Nickel Phyllosilicate - Retarded Growth of Metal Nanoparticles at Higher Rates.

Unavoidable water formation during the reduction of solid catalyst precursors has long been known to influence the nanoparticle size and dispersion in the active catalyst. This in situ transmission electron microscopy study provides insight into the influence of water vapor at the nanoscale on the nucleation and growth of the nanoparticles (2-16 nm) during the reduction of a nickel phyllosilicate catalyst precursor under H/Ar gas at 700 °C. Water suppresses and delays nucleation, but counterintuitively increases the rate of particle growth.

Direct Observation of Ni Nanoparticle Growth in Carbon-Supported Nickel under Carbon Dioxide Hydrogenation Atmosphere.

Understanding nanoparticle growth is crucial to increase the lifetime of supported metal catalysts. In this study, we employ gas-phase transmission electron microscopy to visualize the movement and growth of ensembles of tens of nickel nanoparticles supported on carbon for CO hydrogenation at atmospheric pressure (H:CO = 4:1) and relevant temperature (450 °C) in real time. We observe two modes of particle movement with an order of magnitude difference in velocity: fast, intermittent movement ( = 0.

Silicalite-1 Layer Secures the Bifunctional Nature of a CO Hydrogenation Catalyst.

Close proximity usually shortens the travel distance of reaction intermediates, thus able to promote the catalytic performance of CO hydrogenation by a bifunctional catalyst, such as the widely reported InO/H-ZSM-5. However, nanoscale proximity (, powder mixing, PM) more likely causes the fast deactivation of the catalyst, probably due to the migration of metals (, In) that not only neutralizes the acid sites of zeolites but also leads to the reconstruction of the InO surface, thus resulting in catalyst deactivation. Additionally, zeolite coking is another potential deactivation factor when dealing with this methanol-mediated CO hydrogenation process.

Insight into the Nature of the ZnO Promoter during Methanol Synthesis.

Despite the great commercial relevance of zinc-promoted copper catalysts for methanol synthesis, the nature of the Cu-ZnO synergy and the nature of the active Zn-based promoter species under industrially relevant conditions are still a topic of vivid debate. Detailed characterization of the chemical speciation of any promoter under high-pressure working conditions is challenging but specifically hampered by the large fraction of Zn spectator species bound to the oxidic catalyst support. We present the use of weakly interacting graphitic carbon supports as a tool to study the active speciation of the Zn promoter phase that is in close contact with the Cu nanoparticles using time-resolved X-ray absorption spectroscopy under working conditions.

New mechanism for the nucleation and growth of large zeolite X crystals in the presence of triethanolamine.

Large octahedral zeolite X crystals nucleate inside preformed spherical particles at the interface between an amorphous core and a shell of zeolite P nanorods. Triethanolamine enhances the sphere formation and is involved in the growth of zeolite X crystals.