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1.
The effects of gas composition on hybrid gas–water gliding arc discharge plasma reactor have been studied. The voltage cycles
are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and
a current peak in the half period (10 ms). Emission spectrum measurements revealed that •OH hydroxyl radicals are present in the discharge with feeding any gas. The H 2O 2 concentrations reach 38.0, 15.0, 10.0, and 8.0 mg/l after 25 min plasma treatment with oxygen, argon, air, and nitrogen,
respectively. O 3 was produced when oxygen and air are used, but not when nitrogen and argon. The O 3 concentration reached the highest value 1.0 mg/l after 25 min plasma treatment with oxygen feeding gas, but gradually decreased
to 0.2 mg/l after that. With feeding nitrogenous gas, NO 2
− and NO 3
− byproducts were formed by the plasma chemical process. 相似文献
2.
The decomposition by electron beam (EB) irradiation of 1-chloronaphthalene in different gas matrices (air, N 2) was studied. Over 80% 1-chloronaphthalene was decomposed in air at 58 kGy dose when the initial concentration of 1-chloronaphthalene was 12–30 mg/Nm 3. Over 50% 1-chloronaphthalene was decomposed in nitrogen when the initial concentration of 1-chloronaphthalene was 15–42 mg/Nm 3. 相似文献
3.
Laboratory-scale experiments were performed to evaluate the humidity effect on toluene decomposition by using a wire-plate dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. The toluene decomposition efficiency as well as the carbon dioxide selectivity with/without water in a gas stream of N 2 with 5% O 2 was investigated. Under the optimal humidity of 0.2% the characteristics of toluene decomposition in various background gas, including air, N 2 with 500 ppm O 2, and N 2 with 5% O 2 were observed. In addition, the influence of a catalyst on the decomposition was studied at selected humidities. It was found that the optimum toluene removal efficiency was achieved by the gas stream containing 0.2% H 2O, since the presence of water enhanced the CO 2 selectivity. In addition, the toluene removal efficiency increased significantly in a dry gas stream but decreased with an increase in the humidity when the Co 3O 4/Al 2O 3/nickel foam catalyst was introduced into the discharge area. 相似文献
4.
Data on the selective oxidation of methane to synthesis gas on a 9% NiCuCr/2% Ce/(ϑ + α)-Al 2O 3 catalyst in dilute mixtures with Ar at short residence times (2–3 ms) are presented. The composition, structure, morphology,
and adsorption properties of the catalyst with respect to oxygen and hydrogen before and after reaction were studied using
XRD, BET, electron microscopy with electron microdiffraction, TPR, TPO, and TPD of oxygen and hydrogen. The following optimum
conditions for the preparation and pretreatment of the catalyst for selective methane reduction were found: the incipient
wetness impregnation of a support with aqueous nitrate solutions; drying; and heating in air at 873 and then at 1173 K (for
1 h at either temperature) followed by reduction with an H 2-Ar mixture at 1173 K for 1 h. At a residence time of 2–3 ms (space velocity to 1.5 × 10 6 h −1) and 1073–1173 K, the resulting catalyst afforded an 80–100% CH 4 conversion in mixtures with O 2 (CH 4/O 2 = 2: 1) diluted with argon (97.2–98.0%) to synthesis gas with H 2/CO = 2: 1. The selectivity of CO and H 2 formation was 99.6–100 and 99–100%, respectively; CO 2 was almost absent from the reaction products. The catalyst activity did not decrease for 56 h; carbon deposition was not
observed. A possible mechanism of the direct oxidation of CH 4 to synthesis gas is considered. 相似文献
5.
The thermal decomposition process of mixtures of CoC 2O 4⋅2H 2O (COD) or Co(HCOO) 2⋅2H 2O (CFD) or [Co(NH 3) 6] 2(C 2O 4) 3⋅4H 2O (HACOT) with activated carbon was studied with simultaneous TG–DTG–DTA measurements under non-isothermal conditions in argon
and argon/oxygen admixtures. The results show that the thermal decomposition of the studied mixtures in Ar proceeds in the
same manner. It begins with the salt decomposition to Co met+CoO mixture followed by ( T>680 K) the simultaneous reduction of CoO to Co metand carbon degasification. The final product of the thermal decomposition of COD-C and CFD-C mixtures, identified by XRD,
is β-Co. Cobalt contents determined in the final products fall in the range 71–78 mass%. The rest is amorphous residual carbon.
In Ar/O 2 admixtures the end product is Co 3O 4 with ash admixture.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
The rates of heat release in the nitrogen dioxide— n-decane system at a molar ratio of nitrogen oxides to n-decane (β) from 2.4·10 −3 to 3.1 and gaseous volumes per mole of n-decane ( V(g)) equal to 0.05–4.5 were studied in the 55.2–92.8 °C temperature range. The initial rate of the process is determined by
the interaction of NO 2 with n-decane. The equilibrium constants of dissociation of N 2O 4 in n-decane and Henry's constants of NO 2 and N 2O 4 in an n-decane solution were determined by complex analysis of the thermodynamic equilibrium in the NO 2— n-decane system and dependences of the initial rates on V(g) and β. The experimentally observed self-acceleration of the process in the region of high β and low T values was suggested to be due to the reaction of N 2O 4 with intermediate oxidation products. The rate constants of the reaction of NO 2 with n-decane were compared with analogous values determined in its mixtures with HNO 3 solutions.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1789–1794, October, 1997. 相似文献
7.
Catalytic activities exerted by the lanthanide oxides Ln 2O 3 ( Ln=La, Sm, Gd and Dy) (0.25 mol%) on the thermal decomposition of barium perchlorate were studied gasometrically at 718 K. The
α vs. t plot for the salt alone displays (i) initial gas evolution (ii) an induction period, (iii) a short acceleratory stage and
(iv) a long decay stage. For the mixtures with Ln 2O 3, phenomena (i) and (ii) are not observed. Ln 2O 3 enhances the rate of reaction in both the acceleratory and the decay stage, and increases the fraction decomposed, α, in
the sequence La 2O 3>Gd 2O 3>Sm 2O 3,>Dy 2O 3.
The influence of Dy 2O 3 (0.25–2.0 mol%) on the decomposition of Ba(ClO 4) 2 at 718 K indicates that such admixture facilitates the process and the effect increases with increasing concentration.
The salt alone and the mixtures decompose through the same stages in the temperature range 703–733 K as at 718 K. The data
on both types of samples fit well to the Prout-Tompkins and the Avrami-Erofeev mechanism, suggesting that nucleation takes
place in a chain-branching manner and that the two-dimensional growth of the nuclei occurs during the process. Admixture enhances
the rate of reaction marked without affecting the energy of activation
.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
The thermal behaviour of CrO 3 on heating up to 600°C in dynamic atmospheres of air, N 2 and H 2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy
(DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i)
melting of CrO 3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr 2(CrO 4) 3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr 2O 3 at 415–490°C (significantly dependent). The decomposition CrO 3 → Cr 2(CrO 4) 3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr 2(CrO 4) 3 → Cr 2O 3 involves endothermic reductive deoxygenation reactions in air (or N 2) which are greatly accelerated and rendered exothermic in the presence of H 2. TG measurements as a function of heating rate (2–50°C min −1) demonstrated the acceleratory role of H 2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H 2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function
of the heating rate (2–50°C min −1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
In this study, thermogravimetric analysis (TG) testing is used to measure the mass loss of polished Al–6Zn–XMg ( X = 0 and 2 mass%) alloy samples heated at 773 K for 6 h in dry air or nitrogen gas. The progressive development of thermally
formed oxides on an Al–6Zn–XMg ( X = 0 and 2 mass%) alloy as shown by X-ray diffractometer analyses is discussed. Zn-spinel and Mg-spinel are detected on the
Al–6Zn and Al–6Zn–2Mg alloy samples, respectively, and then heated in the dry air atmosphere; AlN and Mg 3N 2 are detected in alloy samples heated in nitrogen gas. The chain reactions that cause the serrated change in the mass loss
curve are proposed and discussed. 相似文献
10.
The decomposition of dimethyl sulfide (DMS) at initial concentrations of 4.5–18.0 ppmv in air was studied under electron-beam
(EB) irradiation. Doses to decompose 90% of input DMS were 2.5 kGy for 4.5 ppmv, 3.4 kGy for 10.6 ppmv, and 3.9 kGy for 18.0 ppmv.
HCOOH, (CH 3) 2SO, and trace CH 3OH and (CH 3) 2SO 2 were produced as irradiation products in addition to CO 2 and CO. Application of an O 3 decomposition catalyst to an irradiated sample gas led to an enhancement in the oxidation of DMS and its products into CO 2 and the decomposition of O 3. For 10.6 ppmv DMS/air, the mineralization ratio increased from 41% via only EB irradiation to 100% via the combination treatment
at 6.3 kGy. The yield of CO 2 to CO x increased from 5.3 to 87.6% by combination with catalytic oxidation. This combination treatment enables the irradiation energy
used to deodorize gas streams containing DMS to be reduced. 相似文献
11.
This paper reports the formation and characterization of large (Ar)
n
, (N 2)
n
, and mixed binary (Ar)
n
(N 2)
m
van der Waals clusters produced at room temperature in the process of supersonic expansion. The average cluster size is determined
by the buffer gas induced beam-broadening technique. For both Ar and N 2 clusters, power variations of the average cluster size
with the gas stagnation pressure P
0 give size scaling as . The average cluster sizes of argon vary from 2950 to more than 30900 atoms per cluster with the argon gas stagnation pressures
ranging from 4 to 14 bars, and of nitrogen vary from 600 to more than 10400 molecules per cluster with the nitrogen gas stagnation
pressures ranging from 8 to 38 bars. The mixed binary (Ar)
n
(N 2)
m
cluster is produced by supersonic expansion of an Ar–N 2 mixture. The large mixed binary (Ar)
n
(N 2)
m
clusters with the average sizes n + m between 1000 and 16000 are obtained. In coexpansion of Ar–N 2 mixture, we find that the argon concentration becomes higher in the beam than before the expansion. This finding is discussed
and may be helpful for further insight into the phenomenon of clustering. 相似文献
12.
One of the methods for the synthesis of peroxy-radical condensates is the condensation at liquid nitrogen temperature of an
H 2+O 2 mixture dissociated in an electrical discharge at low pressure. Peroxy-radical condensates are thought to contain substantial
quantities of higher hydrogen peroxides H 2O 3 and H 2O 4. The present work investigates the influence of experimental parameters on the synthesis of peroxy-radical condensates from
an H 2+O 2 mixture, analyses the relevant literature, and recommends the optimal experimental conditions for the synthesis. The synthesis
is carried out in a U-tube electrical discharge reactor (inner diameter ∼15 mm), immersed in liquid nitrogen, at rather low
pressure (0.5–1 Torr). The maximum conversion of initial O 2 into higher hydrogen peroxides was observed at a composition of initial gas mixture of 66.7% H 2 + 33.3% O 2. 相似文献
13.
The decomposition of carbon tetrachloride was investigated in an RF inductively coupled thermal plasma reactor in inert CCl 4–Ar and in oxidative CCl 4–O 2–Ar systems, respectively. The exhaust gases were analyzed by gas chromatography-mass spectrometry. The kinetics of CCl 4 decomposition at the experimental conditions was modeled in the temperature range of 300–7,000 K. The simulations predicted
67.0 and 97.9% net conversions of CCl 4 for CCl 4–Ar and for CCl 4–O 2–Ar, respectively. These values are close to the experimentally determined values of 60.6 and 92.5%. We concluded that in
RF thermal plasma much less CCl 4 reconstructed in oxidative environment than in an oxygen-free mixture. 相似文献
14.
The decomposition of chlorinated volatile organic compounds by non-thermal plasma generated in a dielectric barrier discharge
was investigated. As model compounds trichloroethylene (TCE) and 1,2-dichloroethane (DCE) were chosen. It was found that TCE
removal exceeds 95% for input energy densities above 0.2 eV/molecule, regardless of the initial concentration of TCE, in the
range 100–750 ppm. On the other hand, DCE was more difficult to decompose, the removal rate reached a maximum of 60% at the
highest input energy used. For both investigated compounds the selectivity towards carbon dioxide was significantly influenced
by their initial concentration, increasing when low concentrations were used. The gas flow rate had also an effect on CO 2 selectivity, which is higher at low flow rate, due to the higher residence time of the gas in the plasma. The best values
obtained in these experiments were around 80%. 相似文献
15.
The catalytic activity of dioxo-molybdenum(VI)-dichloro[4,4′-dicarboxylato-2,2′-bipyridine] covalently anchored through the
carboxylate function to the surface of TiO 2 has been tested for the oxidative degradation of 1-chloro-4-ethylbenzene in MeCN solution under argon and UV irradiation
(λ = 254 nm). After 4–5 h of photochemical reaction, the Mo complex was reoxidized in the presence of O 2 in the dark, and then the reaction was continued under argon. The reaction proceeds by the intermediate formation of 4′-chloroacetophenone
that undergoes further decomposition to chlorobenzene, plus small amounts of oxygen-containing organochlorine compounds, CO 2 and H 2O. Similar results were obtained for the decomposition of 4′-chloroacetophenone under the same conditions, which also gave
chlorobenzene as one of the main products. The ratio of [final product]/[Mo complex] increases during the decomposition of
1-chloro-4-ethylbenzene (up to 350–400% for 30–35 h of reaction), which provides evidence of a catalytic process. The probable
photochemical reactions are discussed. 相似文献
16.
Reactive species generated in the gas and in water by cold air plasma of the transient spark discharge in various N2/O2 gas mixtures (including pure N2 and pure O2) have been examined. The discharge was operated without/with circulated water driven down the inclined grounded electrode. Without water, NO and NO2 are typically produced with maximum concentrations at 50% O2. N2O was also present for low O2 contents (up to 20%), while O3 was generated only in pure O2. With water, gaseous NO and NO2 concentrations were lower, N2O was completely suppressed and HNO2 increased; and O3 was lowered in O2 gas. All species production decreased with the gas flow rate increasing from 0.5 to 2.2 L/min. Liquid phase species (H2O2, NO2 ̄, NO3 ̄, ·OH) were detected in plasma treated water. H2O2 reached the highest concentrations in pure N2 and O2. On the other hand, nitrites NO2 ̄ and nitrates NO3 ̄ peaked between 20 and 80% O2 and were associated with pH reduction. The concentrations of all species increased with the plasma treatment time. Aqueous ·OH radicals were analyzed by terephthalic acid fluorescence and their concentration correlated with H2O2. The antibacterial efficacy of the transient spark on bacteria in water increased with water treatment time and was found the strongest in the air-like mixture thanks to the peroxynitrite formation. Yet, significant antibacterial effects were found even in pure N2 and in pure O2 most likely due to high ·OH radical concentrations. Controlling the N2/O2 ratio in the gas mixture, gas flow rate, and water treatment time enables tuning the antibacterial efficacy. 相似文献
17.
Abnormally high heats, exceeding 2000 kJ/mol (20 eV) per molecule of O 2, are generated by interaction of the oxygen with the hydrogen absorbed on palladium, gold and nickel particles at 25 °C to 220 °C. The highest heats were observed when the metals were treated with micromole quantities of argon, prior to absorption of hydrogen, as well as its interactions with metal particles reaching nanometer size. In the latter case the heat evolutions due to the interactions with hydrogen were approaching 5000 kJ/mol. The interactions with oxygen in inert gas environments, such as that of argon, yielded higher heat evolutions than those given by pure O 2 pulses injected into nitrogen carrier gas. The results revealed an important role of argon in increasing the intensity of atomic hydrogen-oxygen reactions to a level several times higher than the heat of water formation from molecular hydrogen and oxygen. 相似文献
18.
Computer simulations of benzene and toluene decomposition in air (79% N 2+21% O 2) and in flue gas (87% N 2+10% O 2+3% H 2O+160 ppm SO 2+80 ppm NO) under electron beam (EB) irradiation were carried out using computer code KINETIC and GEAR method. 285 reactions involving 73 species and 294 reactions involving 78 species were considered for simulation of benzene and toluene decomposition, respectively. Calculation results of benzene and toluene decomposition in air under electron beam agree well with the published experimental results. OH radicals play a main role in benzene or toluene decomposition. 相似文献
19.
To identify the decomposition characteristics of trimethylamine (TMA) by electron beam (EB), we conducted an experiment based on process parameters, including absorbed dose (2.5–10 kGy), background gas (air, O 2, N 2 and He), water content (1,200, 14,300, and 27,500 ppm), initial concentration (50, 100, and 200 ppm) and reactor type (batch or continuous flow system). Air background gas showed a maximum TMA removal efficiency of 86 % at 10 kGy and that was the highest efficiency of all background gases. Energy efficiencies were higher when the absorbed dose was lower (e.g., 2.5 kGy). Decomposition efficiencies of all initial TMA concentrations were approximately >90 % at 10 kGy. Removal efficiencies increased up to 30 % as water vapor increased. As a by-product, it is observed that CH 3 radical formed by EB irradiation was converted into CH 4 by reaction with residual TMA, (CH 3) 2NH, and H. These results suggest that EB technology can be applied for TMA treatment under low concentration and high flow rate conditions. 相似文献
20.
The surface and in-depth compositions of sputter-deposited Cu 0.57Ni 0.42Mn 0.01 thin films were studied by Auger electron depth profiling after thermal treatment. The samples were thermally cycled to maximum
temperatures of 300 °C to 550 °C in air, argon and forming gas (N 2, 5 vol. % H 2). Linear least-squares fit to standard spectra and factor analysis were applied to separate the overlapping Auger transitions
of Cu and Ni.
Under bombardment by 4 keV argon ions, CuNi(Mn) layers display bombardment-induced surface enrichment of Ni in the same extent
as binary CuNi alloys. At sufficiently high oxygen partial pressures, a duplex oxide layer is formed and a thick surface copper
oxide overgrows the initial nickel oxide. In reducing atmosphere selective oxidation of manganese takes place.
A capping NiCr layer prevents CuNi(Mn) from being oxidized, but the film configuration is degraded with increasing annealing
temperature due to formation of a surface chromium oxide and diffusion of Ni from the CuNi(Mn) layer into the NiCr/CuNi(Mn)
interface. 相似文献
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