Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

High pressure vapour-liquid equilibrium data for the C₂H₆ + N₂, C₂H₄ + N₂, C₃H₈ + N₂, and C₃H₆ + N₂ systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.     

Ionization gauge sensitivities of N2, O2, N2O, NO, NO2, NH3, CClF3 and CH3OH

A Bayard-Alpert (BA) gauge was used to determine apparent relative sensitivites S_rel,X for O₂, N₂O, NO, NO₂, NH₃, CClF₃ and CH₃OH from gauge calibration measurements in the range 1.3×10^–1 Pap1.3·10^–3Pa. Nitrogen was used as a calibration standard.     

Synthesis of meso-furyl porphyrins with N4, N3S, N2S2 and N3O porphyrin cores

A series of meso-furyl porphyrins with four different porphyrin cores (N₄, N₃S, N₂S₂ and N₃O) were synthesized and characterized. The comparison of NMR, optical and fluorescence properties of meso-furyl porphyrins with porphyrins with six-membered aryl groups indicates that electronic properties of porphyrins were changed drastically on the introduction of furyl groups at meso positions. The maximum shifts in spectral bands were observed for meso-furyl porphyrins with N₂S₂ core. On protonation, the absorption bands of meso-furyl porphyrins were further red shifted. All these changes were ascribed to the possibility of more planarity of the meso-furyl porphyrins due to the small size of the furyl groups which results in extending the π-delocalisation of the porphyrin ring in to the furyl groups.     

PVTx measurements for N2O + CH3F, N2O + CH2F2, and N2O + CHF3 binary systems

Isochoric PVTx measurements have been performed for the binary system of nitrous oxide + CH₃F (R41), +CH₂F₂ (R32), and +CHF₃ (R23) using a new experimental set-up. The experiments covered both the two-phase region and the superheated vapor region and were performed within the temperature range 214–358 K and within a pressure range from 270 to 5600 kPa. Data have been collected for not less than four compositions for each system. The vapor–liquid equilibrium data were derived correlating the experimental data by means of the Carnahan–Starling–De Santis equation of state. The studied systems show a positive deviation from the Raoult's law. The results obtained were compared with the Burnett PVTx data. The two methods showed a mutual consistency within an acceptable margin of error. No other experimental PVTx data were found in the literature for these binary systems.     

Evidence for kinetic and oxidative stabilization of Rh on Mo-promoted Rh/Al2O3

Carbon monoxide hydrogenation studies on silica- and alumina-supported Rh catalysts conducted in our laboratories as well as those reported in the literature suggest that the addition of early transition-metal oxides to the catalyst surface exerts a promotional influence on active Rh centers. This promotion leads to enhanced oxygenate selectivity. Explanations of the promotional influence of the early transition-metal oxides fall into three categories: (i) kinetic stabilization of small Rh aggregates, (ii) wetting and spreading of the transition-metal oxide, leading to decoration of the surface of Rh crystallites, and (iii) oxidative stabilization of Rh aggregates, altering Rh interactions with sub-carbonyls during reaction. Characterization of the Rh---Mo/γ-Al₂O₃ system provides supporting evidence for both kinetic stabilization and oxidative stabilization of Rh aggregates and suggests that these processes contribute to the enhanced oxygenate selectivity of these materials. Hydrogen and carbon monoxide chemisorption results provide evidence for highly dispersed and oxidatively stabilized Rh aggregates. Even after extended on-stream testing (> 10 h), where metal aggregation is unavoidable, high-resolution transmission electron microscopy, associated energy dispersive spectroscopy, and the use of fast-Fourier transform post-processing to produce optical diffractograms highlight differences in the metal-aggregate morphology.     

TPR studies on steam reforming of 2-propanol on Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3

Reaction pathways for steam reforming of 2-propanol (isopropyl alcohol, IPA) on Rh/Al₂O₃, Ru/Al₂O₃ and Pd/Al₂O₃ have been studied by temperature-programmed reactions (TPRs) of IPA and acetone in the presence of steam. The results of TPRs suggest that that of IPA on Rh/Al₂O₃ and Ru/Al₂O₃ proceeds via acetone, while the steam reforming of IPA on Pd/Al₂O₃ takes place via propene from acetone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Atomistic Mechanisms for Catalytic Transformations of NO to NH3, N2O,and N2 by Pd

The industrial pollutant NO is a potential threat to the environment and to human health. Thus, selective catalytic reduction of NO into harmless N\begin{document}$_2$\end{document}, NH\begin{document}$_3$\end{document}, and/or N\begin{document}$_2$\end{document}O gas is of great interest. Among many catalysts, metal Pd has been demonstrated to be most efficient for selectivity of reducing NO to N\begin{document}$_2$\end{document}. However, the reduction mechanism of NO on Pd, especially the route of N\begin{document}$-$\end{document}N bond formation, remains unclear, impeding the development of new, improved catalysts. We report here the elementary reaction steps in the reaction pathway of reducing NO to NH\begin{document}$_3$\end{document}, N\begin{document}$_2$\end{document}O, and N\begin{document}$_2$\end{document}, based on density functional theory (DFT)-based quantum mechanics calculations. We show that the formation of N\begin{document}$_2$\end{document}O proceeds through an Eley-Rideal (E-R) reaction pathway that couples one adsorbed NO\begin{document}$^*$\end{document} with one non-adsorbed NO from the solvent or gas phase. This reaction requires high NO\begin{document}$^*$\end{document} surface coverage, leading first to the formation of the trans-(NO)\begin{document}$_2$\end{document}\begin{document}$^*$\end{document} intermediate with a low N\begin{document}$-$\end{document}N coupling barrier (0.58 eV). Notably, trans-(NO)\begin{document}$_2$\end{document}\begin{document}$^*$\end{document} will continue to react with NO in the solvent to form N\begin{document}$_2$\end{document}O, that has not been reported. With the consumption of NO and the formation of N\begin{document}$_2$\end{document}O\begin{document}$^*$\end{document} in the solvent, the Langmuir-Hinshelwood (L-H) mechanism will dominate at this time, and N\begin{document}$_2$\end{document}O\begin{document}$^*$\end{document} will be reduced by hydrogenation at a low chemical barrier (0.42 eV) to form N\begin{document}$_2$\end{document}. In contrast, NH\begin{document}$_3$\end{document} is completely formed by the L-H reaction, which has a higher chemical barrier (0.87 eV). Our predicted E-R reaction has not previously been reported, but it explains some existing experimental observations. In addition, we examine how catalyst activity might be improved by doping a single metal atom (M) at the NO\begin{document}$^*$\end{document} adsorption site to form M/Pd and show its influence on the barrier for forming the N\begin{document}$-$\end{document}N bond to provide control over the product distribution.     

Intermolecular forces for D2, N2, O2, F2 and CO2

The intermolecular potentials for D₂, N₂, O₂, F₂ and CO₂ are determined on the basis of the second virial coeffincients, the polarizabilities parallel and perpendicular to the molecular axes, and the electric quadrupole moment. The repulsive parts of the potentials are taken from the corresponding Kihara core-potentials. Effects of the octopolar induction are taken into consideration in a unique way. The potential depends on relative orientations of the two molecules as well as the distance r between the molecular centers. This dependence is shown in graphs. A measure of the anisotropy of the potential depth is 0.72 for CO₂ 0.36 for D₂, and smaller than 0.27 for N₂ O₂ and F₂. The remarkable anisotropy for CO₂ and D₂ is due to strong electrostatic quadrupole interactions.     

Vibrational Spectra of the Cyclic SN-Compounds S4N4, S4N4H4 and S3N3Cl3

The IR and Raman spectra of solid and dissolved S₄N₄, S₄N₄H₄, S₄N₄D₄ and S₃N₃Cl₃ have been recorded and are assigned according to D_2d, C_4v and C_3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

The pure rotational Raman spectra of cyanogen, C2N2 and C2N2

The pure rotational Raman spectra of C₂¹⁴N₂ and C₂¹⁵N₂ have been recorded photographically using a 3-metre spectrograph with a reciprocal linear dispersion of 1.4 cm⁻¹ mm⁻¹ at 488.0 nm and analysed to give the rotational and centrifugal distortion constants for both species. Corrections were applied to compensate for the effect of molecules in excited vibrational states on the pure rotational spectra. Comparisons are made with previous infrared vibration—rotational studies on these species and with previous Raman studies on C₂¹⁴N₂. The following bond lengths were calculated: r₀(C---N) = 116 ± 1 pm; r₀(C---C) = 138 ± 2 pm.     

Ru催化N2与H2反应合成氨的两态反应机理

采用密度泛函理论(DFT)UB3LYP方法对Ru在单重态、三重态及五重态势能面上催化N_2与H_2反应合成氨的两态反应机理进行理论研究,发现该反应为典型的两态反应。计算得到最低能量交叉点(MECP)处自旋-轨道耦合常数(H_(soc))及双程系间窜越几率(P~(ISC)),MECP1:H_(soc)=508.34 cm~(-1),P_2~(ISC)=0.85,MECP9:H_(soc)=269.21 cm~(-1),P_2~(ISC)=0.27。运用能量跨度模型(energetic span model)确定Ru催化合成氨反应的转化频率(TOF)决速过渡态(TDTS)为~3TS2-3,TOF决速中间体(TDI)为~3IM9。     

35Cl NQR in N3P3Cl4Ph2 and N3P3Cl4(NMe2)2

³⁵Cl NQR has been investigated in two cyclotriphosphazene derivatives N₃P₃Cl₄Ph₂ and N₃P₃Cl₄(NMe₂)₂. The observed frequencies are assigned to the various chlorines and the temperature variation of the NQR frequencies studied in the range from 77 K to 300 K. The results are analysed using the Bayer-Kushida-Brown approach. Torsional (librational) frequencies are found to fall in the range 10–25 cm^?1 and are found to be only slightly temperature dependent.     

Synthesis and spectral properties of N4, N3S, and N2S2 porphyrins containing one, two, three, and four meso-furyl groups

Porphyrins with N₄, N₃S, and N₂S₂ cores having one, two, three, and four furyl groups at the meso-positions were synthesized by following various methodologies and characterized by using mass spectrometry, NMR spectroscopy, elemental analysis, absorption, and fluorescence spectroscopic techniques. NMR studies indicated that by replacing the meso-aryl groups with meso-furyl groups, the β-pyrrole and β-thiophene protons of porphyrins experienced considerable downfield shifts, supporting the alteration of π-delocalization of porphyrins on the introduction of meso-furyl groups. The absorption and emission bands of porphyrins experienced red shifts on the introduction of meso-furyl groups and the magnitude of red shifts vary linearly with the number of meso-furyl groups. Thus, the spectral studies supported a systematic alteration in spectral properties on successive introduction of meso-furyl groups.     

Bestimmung von N2O3, NO2 und HNO2 in Salpeters?ure

Ohne Zusammenfassung     

Zur Trennung von H2, O2, N2, NO, CO, N2O, CO2, C2H6, C2H4, C2H2, NO2(N2O4) und Feuchtigkeit

Ohne Zusammenfassung     

Kinetics of O(1D) interactions with the atmospheric gases N2, N2O,H2O,H2, CO2, and O3

Rate coefficients for collisional removal of O(¹D) by six atmospheric gases have been measured by monitoring the appearance of O(³P) following photolytic production of O(¹D). The measured values, k_M±2σ, in units of 10^?11 cm^?3 molecule ^?1 s^?1 are k_O3 = 22.8±2.3, k_N2 = 2.52 ± 0.25, k_CO2 = 10.4 ± 1.0,k_H2O 195± 2.0, k_N2O = 11.7 ± 1.2, and k_H2, = 11.8±1.2.     

Fe,V-co-doped C2N for electrocatalytic N2-to-NH3 conversion

Designing providential catalyst is the key to drive the electrochemical nitrogen reduction reactions(NRR),which is referring to multiple intermediates and products. By means of density functional theory(DFT)calculations, we studied heteronuclear bi-atom electrocatalyst(HBEC) for NRR. Our results revealed that compared to homonuclear bi-atom electrocatalyst(Fe_2@C_2N, V_2@C_2N), Fe, V-co-doped C_2N(Fe V@C_2N)had a smaller limiting potential of-0.17 V and could accelerate N_2-to-NH_3 conversion through the enzymatic pathway of NRR. Importantly, N–N bond length monotonically increases with increasing the Bader charges of adsorbed N_2 molecule but decreases with increasing the Bader charge difference of two adsorbed N atoms. Additionally, the Fe V@C_2N could suppress the production of H_2 by the preferential adsorption and reduction of N_2 molecule. Thus, the as-designed HBEC may have the outstanding electrochemical NRR performance. This work opens a new perspective for NRR by HBECs under mild conditions.     

Rate constants for: OH + NO2 (+ N2) → HNO3 (+ N2) between 220 and 358 K

Rate constants have been determined for the reaction OH + NO₂ (+ N₂) → HNO₃ (+ N₂), using time-resolved resonance absorption to follow the removal of OH radicals produced by flash photolysis of HNO₃. The measurements cover the ranges: 220 ? T ? 358 K and 3.2 × 10¹⁷ ? [N₂] ? 4.0 × 10¹⁸ molecule cm^?3.     

A parametric study of CO2/N2 gas separation membrane processes for post-combustion capture

Capture of CO₂ from flue gases produced by the combustion of fossil fuels and biomass in air is referred to as post-combustion capture. Chemisorbent processes are considered to be the most feasible method and are already at an advanced stage of development, but gas separation membranes are attracting more and more attention as a possible alternative. This paper describes a detailed parametric study of mass and energy balances for a simulated single membrane process. Typical operating conditions (CO₂ concentration in the flue gas, pressure and temperature, etc.) together with the influence of the membrane quality (permeability, selectivity) and membrane area on membrane performance (CO₂ separation degree and CO₂ purity) are simulated over a wide range of parameters.