1. Non-oxidative calcination enhances the methane dry reforming performance of ▫$Ni/CeO_{2−x}$▫ catalysts under thermal and photo-thermal conditionsKristijan Lorber, Vasyl Shvalya, Janez Zavašnik, Damjan Vengust, Iztok Arčon, Matej Huš, Andraž Pavlišič, Janvit Teržan, Uroš Cvelbar, Blaž Likozar, Petar Djinović, 2024, original scientific article Abstract: We analyzed the effect of the calcination atmosphere and visible-light contribution to an accelerated
reaction rate and improved H2 selectivity over 2 wt% Ni/CeO2−x nanorod catalysts. Spectroscopic and
structural characterization was performed by operando DRIFTS, in situ Raman, UV-vis and XAS
techniques, which were complemented by DFT calculations. Calcination in an argon or H2 atmosphere
yields 15% more active catalysts in the thermally driven reaction, which are also more susceptible to
light-induced rate acceleration compared to the catalyst calcined in air. The most active 2Ni/CeO2
catalyst calcined in hydrogen converts methane with a rate of 7.5 mmol (gcat min)−1 and produces a H2/
CO ratio of 0.6 at 460 °C when stimulated by a combination of visible light and thermal energy. In the
absence of visible light illumination and at an identical catalyst temperature, the achieved methane rate
was 4.2 mmol (gcat min)−1 and the H2/CO ratio was 0.49. The non-oxidative calcination improves nickel
dispersion and the formation of subnanometer sized Ni clusters, together with a higher abundance of
surface and bulk oxygen vacancies in ceria nanorods. The Ni–Ov–Ce3+components constitute the
catalytically active sites under visible light illumination, which enable the DRM reaction to proceed with
an Ea value of 20 kJ mol−1. Visible light also induces the following changes in the 2Ni/CeO2−x catalyst
during the DRM reaction: (1) decomposition and desorption of carbonates from the nickel–ceria
interface sites, (2) reduced population of nickel surface with carbonyl species and (3) promoted
adsorption and dissociation of methane.
Keywords: methane dry reforming performance, calcination
Published in RUNG: 05.07.2024; Views: 1712; Downloads: 18
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2. Atmospheric peroxyacetyl nitrate (PAN) : a global budget and source attributionE. V. Fischer, D. J. Jacob, R. M. Yantosca, M. P. Sulprizio, D. B. Millet, Jiandong Mao, F. Paulot, H. B. Singh, A. Roiger, Katja Džepina, 2014, original scientific article Abstract: Peroxyacetyl nitrate (PAN) formed in the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) is the principal tropospheric reservoir for nitrogen oxide radicals (NOx = NO + NO2). PAN enables the transport and release of NOx to the remote troposphere with major implications for the global distributions of ozone and OH, the main tropospheric oxidants. Simulation of PAN is a challenge for global models because of the dependence
of PAN on vertical transport as well as complex and uncertain NMVOC sources and chemistry. Here we use an improved representation of NMVOCs in a global 3-D chemical
transport model (GEOS-Chem) and show that it can simulate PAN observations from aircraft campaigns worldwide.
The immediate carbonyl precursors for PAN formation include acetaldehyde (44 % of the global source), methylglyoxal (30 %), acetone (7 %), and a suite of other isoprene and
terpene oxidation products (19 %). A diversity of NMVOC
emissions is responsible for PAN formation globally including isoprene (37 %) and alkanes (14 %). Anthropogenic
sources are dominant in the extratropical Northern Hemisphere outside the growing season. Open fires appear to play
little role except at high northern latitudes in spring, although
results are very sensitive to plume chemistry and plume rise.
Lightning NOx is the dominant contributor to the observed
PAN maximum in the free troposphere over the South Atlantic.
Keywords: peroxyacetyl nitrate, non-methane volatile organic compounds, global 3-D chemical transport model, GEOS-chem
Published in RUNG: 11.04.2021; Views: 3954; Downloads: 0
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3. Viable methanotrophic bacteria enriched from air and rain can oxidize methane at cloud-like conditionsTina Šantl Temkiv, Kai Finster, Bjarne Munk Hansen, Lejla Pašić, Ulrich Gosewinkel Karlson, 2013, original scientific article Keywords: Air microbiology, Methane, Methanotrophs, Methylocystis, Aerial dispersal, Airborne bacteria
Published in RUNG: 04.01.2021; Views: 3354; Downloads: 0
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