Semihydrogenation of acetylene in
an ethylene-rich stream is an
industrially important process. Conventional supported monometallic
Pd catalysts offer high acetylene conversion, but they suffer from
very low selectivity to ethylene due to overhydrogenation and the
formation of carbonaceous deposits. Herein, a series of Ag alloyed
Pd single-atom catalysts, possessing only ppm levels of Pd, supported
on silica gel were prepared by a simple incipient wetness coimpregnation
method and applied to the selective hydrogenation of acetylene in
an ethylene-rich stream under conditions close to the front-end employed
by industry. High acetylene conversion and simultaneous selectivity
to ethylene was attained over a wide temperature window, surpassing
an analogous Au alloyed Pd single-atom system we previously reported.
Restructuring of AgPd nanoparticles and electron transfer from Ag
to Pd were evidenced by in situ FTIR and in situ XPS as a function
of increasing reduction temperature. Microcalorimetry and XANES measurements
support both geometric and electronic synergetic effects between the
alloyed Pd and Ag. Kinetic studies provide valuable insight into the
nature of the active sites within these AgPd/SiO2 catalysts,
and hence, they provide evidence for the key factors underpinning
the excellent performance of these bimetallic catalysts toward the
selective hydrogenation of acetylene under ethylene-rich conditions
while minimizing precious metal usage.
Dry reforming of methane (DRM) is an attractive route to utilize CO2 as a chemical feedstock with which to convert CH4 into valuable syngas and simultaneously mitigate both greenhouse gases. Ni-based DRM catalysts are promising due to their high activity and low cost, but suffer from poor stability due to coke formation which has hindered their commercialization. Herein, we report that atomically dispersed Ni single atoms, stabilized by interaction with Ce-doped hydroxyapatite, are highly active and coke-resistant catalytic sites for DRM. Experimental and computational studies reveal that isolated Ni atoms are intrinsically coke-resistant due to their unique ability to only activate the first C-H bond in CH4, thus avoiding methane deep decomposition into carbon. This discovery offers new opportunities to develop large-scale DRM processes using earth abundant catalysts.
a b s t r a c tThe selective liquid phase hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on SiO 2 , ZnO, ␥-Al 2 O 3 , CeO 2 is reported under extremely mild conditions. Ambient hydrogen pressure, and temperatures as low as 50 • C are shown sufficient to drive furfural hydrogenation with high conversion and >99% selectivity to furfuryl alcohol. Strong support and solvent dependencies are observed, with methanol and n-butanol proving excellent solvents for promoting high furfuryl alcohol yields over uniformly dispersed 4 nm Pt nanoparticles over MgO, CeO 2 and ␥-Al 2 O 3 . In contrast, non-polar solvents conferred poor furfural conversion, while ethanol favored acetal by-product formation. Furfural selective hydrogenation can be tuned through controlling the oxide support, reaction solvent and temperature.
Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air and long charge-carrier lifetimes. However, most double perovskites, including Cs2AgBiBr6, have wide bandgaps,...
Synergistic effects between alkali-free hydrotalcites and gold nanoparticles afford efficient heterogeneous catalysts for the cascade oxidation of 5-HMF to 2,5-FDCA.
Dithiine
linkage formation via a dynamic and self-correcting nucleophilic
aromatic substitution reaction enables the de novo synthesis of a
porous thianthrene-based two-dimensional covalent organic framework
(COF). For the first time, this organo-sulfur moiety is integrated
as a structural building block into a crystalline layered COF. The
structure of the new material deviates from the typical planar interlayer
π-stacking of the COF to form undulated layers caused by bending
along the C–S–C bridge, without loss of aromaticity
and crystallinity of the overall COF structure. Comprehensive experimental
and theoretical investigations of the COF and a model compound, featuring
the thianthrene moiety, suggest partial delocalization of sulfur lone
pair electrons over the aromatic backbone of the COF decreasing the
band gap and promoting redox activity. Postsynthetic sulfurization
allows for direct covalent attachment of polysulfides to the carbon
backbone of the framework to afford a molecular-designed cathode material
for lithium–sulfur (Li–S) batteries with a minimized
polysulfide shuttle. The fabricated coin cell delivers nearly 77%
of the initial capacity even after 500 charge–discharge cycles
at 500 mA/g current density. This novel sulfur linkage in COF chemistry
is an ideal structural motif for designing model materials for studying
advanced electrode materials for Li–S batteries on a molecular
level.
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