The oxidative dehydrogenation (ODH) of propane on single-crystal V(2)O(5)(001) is studied by periodic density functional theory (DFT) calculations. The energetics and pathways for the propane to propene conversion are determined. We show that (i) the C-H bond of propane can be activated by both the terminal and the bridging lattice O atoms on the surface with similar activation energies. At the terminal O site both the radical and the oxo-insertion pathways are likely for the C-H bond activation, while only the oxo-insertion mechanism is feasible at the bridging O site. (ii) Compared to that at the terminal O site, the propene production from the propoxide at the bridging O site is much easier due to the weaker binding of propoxide at the bridging O. It is concluded that single-crystal V(2)O(5)(001) is not a good catalyst due to the terminal O being too active to release propene. It is expected that an efficient catalyst for the ODH reaction has to make a compromise between the ability to activate the C-H bond and the ability to release propene.
In comparison to the traditional
petroleum-based plastics, polylactic
acid, the most popular biodegradable plastic, can be decomposed into
carbon dioxide and water in the environment. However, the natural
degradation of polylactic acid requires a substantial period of time
and, more importantly, it is a carbon-emitting process. Therefore,
it is highly desirable to develop a novel transformation process that
can upcycle the plastic trash into value-added products, especially
with high chemical selectivity. Here we demonstrate a one-pot catalytic
method to convert polylactic acid into alanine by a simple ammonia
solution treatment using a Ru/TiO2 catalyst. The process
has a 77% yield of alanine at 140 °C, and an overall selectivity
of 94% can be reached by recycling experiments. Importantly, no added
hydrogen is used in this process. It has been verified that lactamide
and ammonium lactate are the initial intermediates and that the dehydrogenation
of ammonium lactate initiates the amination, while Ru nanoparticles
are essential for the dehydrogenation/rehydrogenation and amination
steps. The process demonstrated here could expand the application
of polylactic acid waste and inspire new upcycling strategies for
different plastic wastes.
Direct selective oxidation of light alkanes, such as ethane, into value-added chemical products under mild reaction conditions remains a challenge in both industry and academia. Herein, the iridium cluster and atomically dispersed iridium catalysts have been successfully fabricated using nanodiamond as support. The obtained iridium cluster catalyst shows remarkable performance for selective oxidation of ethane under oxygen at 100 °C, with an initial activity as high as 7.5 mol/mol/h and a selectivity to acetic acid higher than 70% after five in situ recycles. The presence of CO in the reaction feed is pivotal for the excellent reaction performance. On the basis of X-ray photoelectron spectroscopy (XPS) analysis, the critical role of CO was revealed, which is to maintain the metallic state of reactive Ir species during the oxidation cycles.
Surfaces with solute responsive wettability can be prepared by covalent layer-by-layer assembly of PNIPAM-c-PNASI with 10 and 100 nm diameter aminated silica nanoparticles. These surfaces are found to exhibit reversible changes in surface wetting in response to solute anion identity and concentration, allowing surfaces to be switched from hydrophilic (advancing water contact angle 68 degrees ) to hydrophobic (advancing water contact angle 145 degrees ). The extent of the response to solute salts is found to be consistent with the Hofmeister series and with associated changes in surface roughness which result from varying degrees of polymer swelling in response to solute ion identity and concentration. The observed wettability changes on these surfaces are reversible.
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