N-hydroxyphthalimide (NHPI) is a promising catalyst in aerobic oxidation of hydrocarbons to corresponding hydroperoxides. We have found that a trace amount of Fe(benz)
3
or Fe(acac)
3
(in ...concentration of less than 10
−1
mmol/l and with the ratio of Fe(III): NHPI = 1:500) considerably accelerates the oxidation of cyclohexene and ethylbenzene, while retaining the selectivity to hydroperoxides at a level of 90%. As a consequence, the reaction temperature could be lowered down to 50–60 °C. The promoting effect of the additives was attributed to the ability of Fe(III) complexes to generate phthalimido-N-oxyl radicals (PINO) without participation in any transformations of hydrocarbon intermediates and hydroperoxides, thus ensuring selective formation and stability of the hydroperoxides.
Graphic Abstract
Numerous wildfires provoked by an unprecedented intensive heat wave caused continuous episodes of extreme air pollution in several Russian cities and densely populated regions, including the Moscow ...region. This paper analyzes the evolution of the surface concentrations of CO, PM10 and ozone over the Moscow region during the 2010 heat wave by integrating available ground based and satellite measurements with results of a mesoscale model. The CHIMERE chemistry transport model is used and modified to include the wildfire emissions of primary pollutants and the shielding effect of smoke aerosols on photolysis. The wildfire emissions are derived from satellite measurements of the fire radiative power and are optimized by assimilating data of ground measurements of carbon monoxide (CO) and particulate matter (PM10) into the model. It is demonstrated that the optimized simulations reproduce independent observations, which were withheld during the optimisation procedure, quite adequately (specifically, the correlation coefficient of daily time series of CO and PM10 exceeds 0.8) and that inclusion of the fire emissions into the model significantly improves its performance. The model results show that wildfires are the principal factor causing the observed air pollution episode associated with the extremely high levels of daily mean CO and PM10 concentrations (up to 10 mg m−3 and 700 μg m−3 in the averages over available monitoring sites, respectively), although accumulation of anthropogenic pollution was also favoured by a stagnant meteorological situation. Indeed, ozone concentrations were simulated to be episodically very large (>400 μg m−3) even when fire emissions were omitted in the model. It was found that fire emissions increased ozone production by providing precursors for ozone formation (mainly VOC), but also inhibited the photochemistry by absorbing and scattering solar radiation. In contrast, diagnostic model runs indicate that ozone concentrations could reach very high values even without fire emissions which provide "fuel" for ozone formation, but, at the same time, inhibit it as a result of absorption and scattering of solar radiation by smoke aerosols. A comparison of MOPITT CO measurements and corresponding simulations indicates that the observed episodes of extreme air pollution in Moscow were only a part of a very strong perturbation of the atmospheric composition, caused by wildfires, over European Russia. It is estimated that 2010 fires in this region emitted ~10 Tg CO, thus more than 85% of the total annual anthropogenic CO emissions. About 30% of total CO fire emissions in European Russia are identified as emissions from peat fires.
Abstract
The article examines the effect of a nanofiller addition, produced from activated quartz waste, on general porosity of cement stone. It contributes to the uniform distribution of micropores ...and reduction of the cement stone porosity. This improves the physical and mechanical properties of the cement stone. The porosity of the cement stone reduces by 17%, while its density and strength increases.
Theoretical problems of modifying physicochemical and biophysical properties of perfluorocarbons (PFCs) and phospholipids (PLs) are substantiated. PFCs and PLs are components of nanoparticles that ...govern their structural integrity. Ways of modifying the physiochemical properties of perfluorodecalin (PFD) and the strength of liposomal structure of PLs are specified. Examples are given of how to preserve the stability of resulting PFD/PL nanoparticles when stored in a nonfrozen state for up to two years.
Chemistry transport models (CTMs) are an indispensable tool for studying and predicting atmospheric and climate effects associated with carbonaceous aerosol from open biomass burning (BB); this type ...of aerosol is known to contribute significantly to both global radiative forcing and to episodes of air pollution in regions affected by wildfires. Improving model performance requires systematic comparison of simulation results with measurements of BB aerosol and elucidation of possible reasons for discrepancies between them, which, by default, are frequently attributed in the literature to uncertainties in emission data. Based on published laboratory data on the atmospheric evolution of BB aerosol and using the volatility basis set (VBS) framework for organic aerosol modeling, we examined the importance of taking gas-particle partitioning and oxidation of semi-volatile organic compounds (SVOCs) into account in simulations of the mesoscale evolution of smoke plumes from intense wildfires that occurred in western Russia in 2010. Biomass burning emissions of primary aerosol components were constrained with PM10 and CO data from the air pollution monitoring network in the Moscow region. The results of the simulations performed with the CHIMERE CTM were evaluated by considering, in particular, the ratio of smoke-related enhancements in PM10 and CO concentrations (ΔPM10 and ΔCO) measured in Finland (in the city of Kuopio), nearly 1000 km downstream of the fire emission sources. It is found that while the simulations based on a "conventional" approach to BB aerosol modeling (disregarding oxidation of SVOCs and assuming organic aerosol material to be non-volatile) strongly underestimated values of ΔPM10/ΔCO observed in Kuopio (by a factor of 2), employing the "advanced" representation of atmospheric processing of organic aerosol material resulted in bringing the simulations to a much closer agreement with the ground measurements. Furthermore, taking gas-particle partitioning and oxidation of SVOCs into account is found to result in a major improvement of the agreement of simulations and satellite measurements of aerosol optical depth, as well as in considerable changes in predicted aerosol composition and top-down BB aerosol emission estimates derived from AOD measurements.
The transformation of organic matter in the soil is largely determined by hydrolytic enzymes. Under the conditions of climate change, understanding the mechanisms of microbial response is of ...particular importance for predicting the carbon cycle. Until now, the effect of drought duration and frequency on soil hydrolytic enzymes has been little studied. A multifactorial field manipulation experiment was carried out, simulating in the presence of plants and without them: two short-term droughts, a long-term drought, and an optimal level of soil moisture. The maximum reaction rate
V
max
, Michaelis constant
K
m
, and catalytic efficiency
K
a
of five groups of enzymes involved in the carbon cycle (cellobiase, glucosidase, xylanase), phosphorus (phosphatase), and nitrogen (chitinase) were determined. In phosphatases, glucosidases, and xylanases,
V
max
decreased during short-term drought. During prolonged drought, the
V
max
value of phosphatases, cellobiohydrolases, and xylanases decreased and increased in chitinases, while remaining unchanged in glucosidases. Both long-term and short-term droughts led to an increase in
K
m
and a decrease in catalytic efficiency (
K
a
) for almost all enzymes. Short-term droughts were not a “weakened version” of a long-term drought, but had their own specifics—a decrease in
K
m
of glucosidases, which led to an increase in
K
a
. Long-term drought was characterized by an increase in
V
max
of chitinases and spatial variability of
V
max
of phosphatases and glucosidases. The influence of the presence of plants was secondary and manifested itself only during short droughts. The reversibility of the effect of drought on
V
max
,
K
m
, and
K
a
decreased in the series first short-term drought > second short-term drought > long-term drought due to an increase in the total duration of the stress impact.
Approaches to increase the efficiency of Pt/C–heteropoly acid catalyst in a liquid-phase oxidation of cyclohexane using an O
2
–H
2
mixture were studied. It was shown that small additives of ionic ...liquid (BMImBr, Bu
4
NBr, or Bu
4
NHSO
4
) significantly improve the catalytic effect of the Pt/C–H
3
PMo
12
O
40
–CH
3
CN system at 35°C, by slowing the rate of side reactions resulting in water formation, increasing the rate of oxygenate formation, and inhibiting their secondary oxidation reactions. The efficiency of H
2
consumption increases from 2 to 18–25%, while the selectivity of cyclohexane conversion is 92–98%. The substitution of one or two Mo(VI) ions by V(V) in the structure of the heteropoly acid decreases these parameters. In the presence of Bu
4
NHSO
4
, a Pt/C catalyst can be used many times. During the reaction, the heteropoly acid present in the solution is in a reduced state under the action of the reaction medium and undergoes reversible redox transformations. The nature of the catalytic action of the studied system is explained from the viewpoint of the effect of ionic liquids on the properties of a Pt/C catalyst in activating O
2
, heteropoly molybdate chemistry, and the known mechanisms of the peroxide oxidation of hydrocarbons.
Cyclooctene and alkylbenzenes are subjected to co-oxidation in oxygen and a system of two catalysts. Radical catalyst Fe(acac)
3
/NHPI mediates the formation of alkylbenzene hydroperoxides, which are ...consumed in situ during the MoO
3
/SiO
2
-catalyzed epoxidation of cyclooctene. The chain oxidation rate is limited in cyclooctene and MoO
3
/SiO
2
, but radical catalyst Fe(acac)
3
/NHPI retains fairly high activity in the oxidation of alkylbenzene in hydroperoxide. It is found that isopropylbenzene is a better co-reducing agent than ethylbenzene because it ensures more vigorous and selective formation of epoxycyclooctane. At optimized amounts of components and a temperature of 80°C, selectivity toward epoxycyclooctane reaches 92 and 96% in ethylbenzene or isopropylbenzene, respectively, with more than 70% conversion of cyclooctene.
The issues of obtaining fireproof textile materials that do not cause negative effects upon contact with human skin using surface treatment are covered. The basic formulations of the compositions ...most frequently used to produce fireproof fabrics are considered. The possibility of developing a composition with optimal properties based on well-known flame retardants by selecting the type and amounts of stabilizers has been studied. The optimal formulation of a flame-retardant impregnating composition is developed, providing resistance to ignition and safe when in contact with human skin. The results of experimental studies of fabrics treated with the developed composition are given, namely: assessment of ignition resistance, smoke-forming ability, toxicity of combustion products, toxicological and hygienic characteristics of the effects on a living organism.
Hydrogen peroxide and Pt activated mixture of gaseous O
2 and H
2 have been applied to oxidation of aromatic compounds in the presence of redox active heteropoly compounds in the form of acid H
4PMo
...11VO
40 and tetrabuthylammonium (TBA) salts TBA
4PMo
11VO
40 and TBA
4HPW
11Fe(OH)O
39. Benzene, toluene and phenol were subjected to hydroxylation of the ring, which was accompanied by secondary oxidation in the reaction with hydrogen peroxide. Oxygenation of toluene was equally directed to the ring and to methyl group. The total reactivity of substrates was increased in the order of benzene
<
toluene
<
phenol in oxidation by both O
2/H
2 and H
2O
2. Analysis of products yield and composition indicated the identical nature of active intermediates for both oxidants. It was suggested that HPC bonded radical species are responsible for the oxidation of hydrocarbons.
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