Nanorod-like
phosphorus-doped ordered mesoporous γ-alumina
(OMA), which has abundant ordered pore channels in the nanorods, was
rapidly synthesized through a modified sol–gel strategy without
use of any mineral acids. Highly dispersed Pd-based catalysts were
synthesized by taking as-obtained phosphorus-doped OMA materials as
carriers for methane combustion. The crystallization temperature of
γ-Al2O3 was increased by phosphorus doping.
The surface acidity properties of γ-Al2O3 were modified upon phosphorus incorporation, which had a significant
effect on catalyst activities, and this influence was much more conspicuous
for the supports calcined at high temperature. The incorporation of
phosphorus adjusted the distribution of palladium active species and
the reducibility of catalysts, synergistically affecting the low-temperature
catalytic performance. Pd/6P-OMA catalyst demonstrated enhanced low-temperature
catalytic properties and stability in the 13-cycle stability and long-term
stability tests. During the reaction cycles, the total CH4 conversion temperature for Pd/6P-OMA catalyst was as low as 345
°C, which could be reduced to 321 °C via hydrogen reduction
treatment. In comparison with the catalyst without dopant, the Pd/6P-OMA
catalyst also exhibited higher hydrothermal stability in the presence
of excess water vapor in the feed.
CeO2-based
catalysts are potentially suitable for H2S-selective oxidation,
but their practical application is
limited due to the problem of sulfate formation. Herein, we report
a facile citric acid-assisted hydrothermal process for the fabrication
of porous Fe-doped CeO2 with flower-like morphology that
can drastically promote the catalytic activities of CeO2 with high durability. Among the synthesized catalysts, the one with
well-defined (110) and (100) planes is highly active for H2S-selective oxidation with H2S conversion and sulfur selectivity
of almost 100% at 220 °C, superior to most of the reported Ce-based
catalysts. Meanwhile, outstanding catalytic stability is achieved
because the presence of Fe ions alleviates ceria deactivation due
to sulfation. The results of systematic investigation prove that the
doping of Fe not only raises the density of oxygen vacancies but also
promotes the redox ability and oxygen activity of the catalyst. We
conducted in situ DRIFTS (diffuse reflection infrared
Fourier transform spectroscopy) experiments and density functional
theory (DFT) calculations to disclose the reaction mechanism of H2S oxidation. The derived insights are important for the design
of efficient ceria-related catalysts for practical applications.
A series of graphitic
carbon nitride (CN) in the form of nanosheets
with porous structure have been prepared through thermal treatment
of bulk CN in air. Compared with the bulk counterpart, the as-generated
holey CN nanosheets are larger in specific surface area. Endowed with
more active sites and enhanced mass transport ability, the latter
display catalytic performance substantially superior to the former,
exhibiting higher H2S conversion and S selectivity in the
oxidation of H2S to S. Moreover, the CN nanosheets show
much better durability than traditional catalysts. It is envisaged
that the strategy is a general technique that can be extended to produce
porous CN nanosheets from other nitrogen-rich precursors, as well
as to prepare other 2D carbon-based materials for potential applications.
An efficient protocol for the synthesis of hydroxyl-containing quinoxalin-2(1H)-ones has been developed via the copper-catalyzed cross-coupling reaction of quinoxalin-2(1H)-ones with alcohols with moderate to good yields.
A facile TBHP-mediated direct oxidative coupling of quinoxalin-2(1H)-ones with arylaldehydes has been developed under metal-free conditions. This method provided a convenient and efficient approach to various 3-acylated quinoxalin-2(1H)-ones from readily available starting materials with excellent regioselectivity. This reaction proceeded efficiently under mild conditions over a broad range of substrates and with functional group tolerance.
An efficient protocol for the synthesis of 3-alkyl quinoxalin-2(1H)-ones has been developed via the transition-metal-free cross-coupling reaction of quinoxalin-2(1H)-ones with ethers with moderate to good yields under relatively mild conditions.
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