The selective hydrogenation
of acetylene has been studied over
AgPd and CuPd catalysts. Controlled surface reactions were used to
synthesize these bimetallic nanoparticles on both TiO2 and
SiO2 supports. Chemisorption measurements of the bimetallic
catalysts indicate that Pd prefers to be on the nanoparticle surface
with a Cu parent catalyst, while Pd prefers to be subsurface with
a Ag parent catalyst. From energy-dispersive X-ray spectroscopy analysis,
the composition of the nanoparticles is determined to be more uniform
on the SiO2 support compared to that on the TiO2 support. X-ray absorption spectroscopy results indicate that, after
reduction, the CuPd bimetallic catalysts have some Pd–Pd bonds,
but the average number of Pd–Pd bonds decreases after reaction.
Infrared spectra of the adsorbed CO show that an increased fraction
of isolated Pd species are present on the bimetallic catalysts compared
to those on the monometallic catalysts. Adsorption of acetylene and
ethylene, however, indicates adsorbed surface species that require
contiguous Pd ensembles. These results suggest that the surface structure
of the catalyst is highly dynamic and influenced by the gas environment,
as well as the support. The catalysts are active for the selective
hydrogenation of acetylene in an ethylene-rich environment under mild
conditions. Over all catalysts, the ethylene selectivity is greater
than 92%; however, improved selectivity is observed over the bimetallic
catalysts compared to that over the monometallic Pd catalysts. An
ethylene selectivity of 100% is observed over the CuPd0.08/TiO2 catalyst. The highest acetylene conversion rate
per gram of Pd is observed over the CuPd0.02/TiO2 catalyst, while the highest turnover frequency is found over the
AgPd0.64/TiO2 catalyst. The bimetallic SiO2-supported catalysts have lower rates than Pd/SiO2 but still show improved selectivity. The combined characterization
measurements and reaction kinetics studies indicate that the performance
improvements of the bimetallic catalysts may be attributed to both
electronic and geometric modifications of Pd by the parent Cu or Ag
metal.
We studied the hydrogenation at temperatures from 313 – 393 K of a biomass-derived platform molecule, 5-hydroxymethyl furfural (HMF)-Acetone-HMF (HAH) over Pd, Ru, and Cu based catalysts. HAH was selectively...
Synthetic platform for production of biomass-derived monomers and performance-advantaged polymers with renewability, upgradability, and economic viability.
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