According to our knowledge, single-atom Pd catalysts
supported
on covalent triazine frameworks (CTF) have not been studied in the
production of hydrogen from formic acid. Therefore, we synthesized
1 wt % Pd single-atom catalysts based on CTF-1, pyCTF, and bipyCTF
supports and tested them in the gas-phase decomposition of formic
acid. The results were compared with those obtained for a Pd catalyst
supported on mesoporous graphitic-type carbon (Pd/C) with nanoparticles
(∼2.3 nm). The catalysts were characterized by high-angle annular
dark-field/scanning transmission electron microscopy (HAADF/STEM),
extended X-ray absorption fine structure/X-ray absorption near-edge
structure (EXAFS/XANES), and X-ray photoelectron spectroscopy (XPS)
methods. The following order of catalytic activity was obtained: Pd/CTF-1
> Pd/C > Pd/pyCTF ≥ Pd/bipyCTF. The best performance
of the
Pd/CTF-1 catalyst was associated with Pd2+–C2N2 sites. Pd2+–N4 sites
formed on pyCTF and bipyCTF supports showed lower catalytic activity.
The selectivity trend at temperatures above 500 K was as follows:
Pd/bipyCTF > Pd/pyCTF > Pd/CTF-1 > Pd/C. For the Pd/bipyCTF
catalyst,
the selectivity reached 99.8%, which is very high for this temperature
range. These results may be important for the development of CTF-based
catalysts for hydrogen production reactions.
A pair
of mesoporous and hierarchical macro/mesoporous alumina-supported
catalysts having distinct textural parameters have been chosen to
elucidate the effect of texture on activity in hydrodesulfurization
(HDS) and hydrodemetallization (HDM) of heavy tatar oil possessing
extremely high viscosity and sulfur content. For monitoring catalyst
properties, the samples have been investigated by XRD, XFS, XPS, EXAFS,
SEM, TEM, FTIR, TPD-NH3, mercury porosimetry, and N2 adsorption methods. Among different factors such as support
acidity, active component dispersion, and texture, the last one has
been found to play the most significant role in this process. The
hierarchical macro/mesoporous catalyst shows lower coking rate of
the hydrotreated products, as well as higher HDS and HDM conversions
despite its lower active component dispersion and decreased support
acidity.
Mountain lakes in East Siberia have been studied for recent changes in water chemistry, turbidity and diatom assemblages preserved in bottom sediments. We performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes. We analysed sediment records from East Siberian glacier lakes using geochemical and diatoms proxies. We found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the Northern Hemisphere. Our evidences show that diatoms have been gradually decreased since ca. the 1880s. A significant tendency towards diatom reducing occurred at high summer regional temperatures. This tendency may be attributed to the fact that glaciers and snow patches thawed actively in East Siberia during ca. 1880-1958, which was induced by the beginning of the Recent Warming (ca. 1850-1860) and a long period of relatively warm regional climate from ca. 1900 to 1960.
The comprehensive study of the lanthanide-doped solid solutions CuCr0.99Ln0.01S2 (Ln = La…Lu) magnetic properties was carried out using static magnetochemistry and differential scanning calorimetry techniques. It was shown that magnetic properties of CuCr0.99Ln0.01S2 are significantly affected by the magnetic properties of the lanthanide ion. The magnetic susceptibility and the effective magnetic moment were found to deviate from the Curie-Weiss law in the temperature 90 K below and 50 K above the order-disorder transition at 695 K. The observed behavior of the temperature dependence of the effective magnetic moment in the order-disorder transition temperature region was described as a result of copper atoms redistribution over different types of the crystallographic sites.
We studied the biodistribution of luminescent octahedral rhenium cluster complex K4[Re6S8(CN)6], a promising agent for photodynamic therapy. It was shown that rhenium complex [Re6S8(CN)6](4-)is mainly accumulated in the liver, the central organ of metabolism, and can be excreted by the kidneys. The cluster complex was also accumulated in the spleen in significant amount, which makes it a promising agent for creation of preparations for diagnostics and treatment of lymphoproliferative disorders. The mean lethal dose of the cluster complex was 0.38 g/kg.
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