CO2-N2 Mixtures Research Articles

Variations in the strength of the infrared forbidden 2328.2 cm−1 fundamental of solid N2 in binary mixtures

We present the 2335–2325 cm−1 infrared spectra and band positions, profiles and strengths (A values) of solid nitrogen and binary mixtures of N2 with other molecules at 12 K. The data demonstrate that the strength of the infrared forbidden N2 fundamental near 2328 cm−1 is moderately enhanced in the presence of NH3, strongly enhanced in the presence of H2O and very strongly enhanced (by over a factor of 1000) in the presence of CO2, but is not significantly affected by CO, CH4, or O2. The mechanisms for the enhancements in N2–NH3 and N2–H2O mixtures are fundamentally different from those proposed for N2–CO2 mixtures. In the first case, interactions involving hydrogen-bonding are likely the cause. In the latter, a resonant exchange between the N2 stretching fundamental and the 18O=12C asymmetric stretch of 18O12C16O is indicated. The implications of these results for several astrophysical issues are briefly discussed.

Modified van der Waals Equation for the Prediction of Multicomponent Isotherms

A modified two-dimensional van der Waals equation model was proposed for the prediction of multicomponent gas–solid adsorption isotherms from corresponding single-component adsorption equilibrium data. The model was used to predict adsorption isotherms of CO–CO2mixtures and CO2–N2mixtures on Cu(I)–NaY zeolite. Experimental adsorption equilibrium data of the two systems were compared with results calculated from the model and three other models in the literature: the ideal adsorbed solution model, the vacancy solution theory of adsorption using the Flory–Huggins activity coefficient equation, and the two-dimensional van der Waals equation. The results indicated that the modified van der Waals equation predicted the experimental results better than the three other models for the two systems studied, especially for the CO–CO2system, which involved chemical reaction during adsorption and exhibited azeotropic behavior.

Amino acid synthesis from an amorphous substance composed of carbon, nitrogen, and oxygen

Hydrogen cyanide, formaldehyde, and ammonia are considered important intermediates in amino acid synthesis by electric discharge. In this study, however, amino acid precursors were synthesized from a CO–N2 mixture free of hydrogen atoms. An amorphous film composed of carbon, nitrogen, and oxygen was given from a highly activated plasma. When exposed to atmospheric moisture, this film incorporated hydrogen atoms to yield amino acid. This is a mechanism for amino acid synthesis without involving hydrogen cyanide, formaldehyde, and ammonia.

R and D Note: Separation of a Nitrogen-Carbon Dioxide Mixture by Rapid Pressure Swing Adsorption

A N2-CO2 mixture is separated in a rapid pressure swing adsorption apparatus, which consists of single or double adsorbent beds filled with silica gel and operates in the sequence of adsorption, backflow and desorption. Nitrogen-rich gas is produced at the top of the bed, and carbon dioxide-rich gas at the bottom. Carbon dioxide purity of 89.5% and recovery of 70% were obtained in the single-bed apparatus, while purity of 93.5% and recovery of 72.3% were obtained in the double-bed apparatus. The feed in both cases consisted of 81% N2 and 19% CO2.

Line-Mixing Effects inQBranches of CO2

A theoretical model based on the energy corrected sudden (ECS) approximation is used in order to account for line-mixing effects in Δ ↔ Π infraredQbranches of12C16O2. Its quality is demonstrated by comparisons with numerous laboratory spectra of CO2–He and CO2–N2mixtures: threeQbranches in the 4 and 17 μm regions are investigated at room temperature in a wide pressure range. The influence of mixing betweenQ(J) lines associated with odd and even values of the rotational quantum numberJis demonstrated and analyzed in detail. It is shown that, in contrast to available fitting law approaches, the ECS model correctly predicts the influence of the parity of the rotational quantum numbersJandJ′ on coupling between theQ(J) andQ(J′) lines. Comparisons between the effects of collisions of CO2with N2and He are made and analyzed. They show that these two systems involve different line couplings within theQbranch.

Line-Mixing Effects inQBranches of CO2

A theoretical model based on the energy corrected sudden (ECS) approximation is used to account for line-mixing effects in infraredQbranches of parallel bands of CO2. Measurements have been made using a tunable difference frequency spectrometer system in a Π–Π transition: spectra of the 1111II← 0110IQbranch near 3580.3 cm−1have been recorded at room temperature for CO2–He and CO2–N2mixtures in the 0.1–1 atm total pressure range. Comparisons of experimental and computed spectra prove the quality of the ECS approach. It is shown that the influence of line mixing on the shape of parallelQbranches is very weak and much smaller than in perpendicular transitions. This result is analyzed in detail and explained in terms of the effects of the vibrational angular momenta on the dipole transition moments and vector coupling coefficients involved in the relaxation operator elements. The effects of collisions of CO2with N2and He are compared and discussed.

Pulsed CO laser based on the first vibrational overtone

A description is given of the apparatus and calculation method used in experimental and theoretical determination of the characteristics of an electron-beam-controlled CO laser operating exclusively on the basis of the transitions corresponding to the first vibrational overtone. The results of the experimental and theoretical studies are analysed and compared. The adopted model gives results in good agreement with the experimental data for CO—N2 mixtures. A study is reported of the influence of the optical cavity selectivity on the lasing characteristics. Calculations demonstrate that a change from a narrow-band cavity used in our experiments to a broad-band nonselective cavity should improve the energy characteristics of the laser by about an order of magnitude.

Characteristics of Clay Materials for the Separation of Carbon Dioxide from N2-CO2 Mixture by Gas Chromatography.

Characteristics of clay materials for the separation of carbon dioxide from N2-CO2 mixture have been investigated by gas chromatography. The separation ability is evaluated by the difference in the reten tion times for carbon dioxide and nitrogen. Zeolite and sepiolite exhibit the separation ability up to 673k, while montmorillonite, saponite and silica gel show no separation ability above 573 K. The relatively higher separation ability of zeolite and sepiolite is attributed to the relatively higher heats of adsorption for carbon dioxide than those for nitrogen and their higher surface areas.

セピオライトの二酸化炭素分離特性

セピオライトの二酸化炭素分離特性

フェニル基を有するシランで化学修飾した多孔質シリカ膜におけるＣＯ２選択透過性

Porous silica membrane was modified with phenyltriethoxysilane and was used to separate N2-CO2 and N2-CO2-H2O mixtures. The experiment of the separation for N2-CO2 mixture, the separation factor for CO2 (α CO2/N2) was 0.9 in the case of using porous silica membrane (S membrane), however, when the silica membrane modified with phenyl silane coupling reagents (SC membrane) was used, the highest separation factor for CO2 (α CO2/N2) reached 1.19. This was due to the fact that the phenyl group modified the surface of porous, and increased affinity of CO2. So, CO2 was easy to condense on the surface of porous, and N2 become difficult to permeate. For this reason, the separation factor for CO2 can be improved. Further, the experiment of SC membrane in the separation for N2-CO2-H2O mixture, the highest separation factor for CO2 (α CO2/N2) was 1.66, which is higher than that for N2-CO2 mixture.

Thermodynamic model for aqueous Cd2+?CO 3 2? ionic interactions in high-ionic-strength carbonate solutions, and the solubility product of crystalline CdCO3

The aqueous solubility of CdCO3(c) was studied in 0.01M NaClO4, in solutions equilibrated with N2-CO2(g) mixtures that contained 0.0003, 0.001, or 0.138 atmospheres of CO2(g). The pH ranged from about 4.5 to 9, and the studies were conducted from both the oversaturation and the undersaturation directions, with the equilibration periods ranging from 6 to 57 d. To determine the carbonato complexes of Cd(II), the solubility of CdCO3(c) was also studied in 0.0016 to 1.00M Na2CO3 solutions at fixed hydroxide ion concentration, and in solutions with fixed aqueous C concentrations (0.1 and 0.01M C) over a range of OH− from 1×10−5 to 1.0M. The equilibrium Cd concentrations were reached in less than about 6 d. Pitzer's ion-interaction model was used to interpret these solubility data, as well as CdCO3(c) solubility data reported in the literature, which extended to 5.0M K2CO3 with an ionic strength of approximately 18.6 m. Our thermodynamic model required the introduction of two aqueous Cd2+-CO32− complexes, CdCO3(aq) and Cd(CO3)22−, as well as ion-interaction parameters for Cd(CO3)22− with the bulk cations Na+ and K+. This model gave excellent agreement with all available experimental data extending to 5.0M K2CO3. The logarithms of the thermodynamic equilibrium constants for the reactions: $$\begin{gathered} CdCO_3 \left( c \right) \rightleftarrows Cd^{2 + } + CO_3^{2 - } \hfill \\ Cd^{2 + } + CO_3^{2 - } \rightleftarrows CdCO_3 \left( {aq} \right) \hfill \\ Cd^{2 + } + 2CO_3^{2 - } \rightleftarrows Cd\left( {CO_3 } \right)_2^{2 - } \hfill \\ \end{gathered} $$ were found to be −12.24±0.1, 4.71±0.1, and 6.49±0.1, respectively. The β0 ion-interaction parameters for Cd(CO3)22−−Na+ and Cd(CO3)22−−K+ were found to be −0.14 and −0.06, respectively.

Separation of COCO2N2 gas mixture for high-purity CO by pressure swing adsorption

A pressure swing adsorption (PSA) process for separating CO from a COCO2N2 mixture is proposed. The adsorbent used in this process is active carbon supported copper, which has been developed by this laboratory. By cycling the pressure of a bed of this adsorbent between ambient pressure and 20–30 Torr at room temperature, high purity CO can be obtained from the COCO2N2 gas mixture with a high recovery. The CO product purity depends crucially on the step of CO cocurrent purge after adsorption in the cycle and the regeneration of sorbent.

Effects of temperature and composition on the viscosity of respiratory gases

The steady-state sensitivity of resistance pneumotachographs is proportional to viscosity. Dynamic characteristics of pneumotachographs, pressure transducers, and mass spectrometers are also viscosity dependent. We derive linear equations to approximate the viscosities of O2, N2, CO2, H2O, He, N2O, and Ar for temperatures between 20 and 40 degrees C by using published viscosity data and a nonlinear extrapolation equation. We verify the accuracy of the extrapolation equation by comparison with published data. Our linear equations for pure gas viscosities yield standard errors less than 0.35 microP. We also compare a nonlinear equation for calculating the viscosities of mixtures of gases with published measured viscosities of dry air, humid air, and He-O2 and N2-CO2 mixtures. The maximum difference between published and calculated values is 1.3% for 10% CO2 in N2. All other differences are less than 0.38%. For saturated humid air at 35 degrees C, a linear concentration-weighted combination of viscosities differs from our nonlinear equation by 4.9, 2.1, and 1.7% at barometric pressures of 32, 83, and 100 kPa, respectively. By use of our method, the viscosity of normal respiratory gases can be calculated to within 1% of measured values.

Discharge energy balance in the nitrogen-containing active medium of an electron-beam-controlled CO laser

Numerical methods were used to investigate theoretically the dynamics of the energy balance of a discharge in a CO–N2 mixture, taking into account the mutual influence of the distributions of the electron energy and of the populations of the molecules over the vibrational levels. It was shown that this influence plays a decisive part in substantially redistributing the pump energy between the vibrational levels of the CO and N2 molecules in favor of the N2 molecules. A stabilizing action of the nitrogen on the thermal regime of the CO laser-active medium was discovered and the range of optimal CO:N2 ratios was determined.

Study of Nonsteady-State Continuous Membrane Column for Gas Separation

Abstract The permeation and transport processes occurring in a continuous membrane column (CMC) are quite complex, and the system will exhibit inverse response behavior in a certain operating regime. To understand the complex interaction of system variables, this work developed a mathematical model for the CMC and solved the model equations. Dynamic responses of a CMC for the separation of N2-CO2, CO2-O2, and O2-N2 gas mixtures with capillary silicone rubber membranes are presented. The effect of the membrane permeabilities on the CMC dynamics is examined. Responses of system variables to various disturbances, together with the start-up transient of the system, are discussed. The knowledge of the unsteady-state behavior of the CMC will enable us to predict the performance of the CMC and to control the CMC in a dynamic environment.

Influence of easily ionizable substances on the stability of a volume self-sustained discharge in working CO2laser mixtures

The main mechanisms of instabilities in a volume self-sustained discharge were identified by investigating the influence of easily ionizable substances and of other impurities on the duration of stable burning of such a discharge in N2 and in CO2–N2 mixtures when the initial electron density depended weakly on the gas composition. The results obtained demonstrated the dominant role played by multistage ionization in the development of instabilities in volume self-sustained discharges in working CO2 laser mixtures and the need to use easily ionizable substances for the suppression of these instabilities.

Collisional broadening of CO2 IR lines. I. Diode laser measurements for CO2–N2 mixtures in the 295–815 K temperature range

We present first diode–laser measurements of N2-broadened linewidths and strengths of 12C16O2 at high temperature. A T−N dependence of linewidths on temperature is deduced from measurements in the 295–815 K temperature range for the R38, R42, and R54 lines of the ν3 band. The measured line strengths are 21.48±0.49, 12.84±0.28, and 1.82±0.04 cm−2 atm−1 at 300 K for the R38, R42, and R54 lines, respectively. The corresponding half-widths are 71.02, 70.05, and 67.81×10−3 cm−1 atm−1. The N exponent takes the values 0.73±0.05, 0.72±0.02, and 0.72±0.04.

Phase transitions and molar volumes of CO2-CH4-N2 inclusions

The combined application of Raman microspectroscopy and the cooling stage to the study of fluid inclusions opens the possibility determining the molar volumes (v) of fluid mixtures in rocks. Isochoric XT-diagrams are introduced and it is demonstrated that the equations of state presently available (for example the Heyen equation for CO2-N2 mixtures) are not valid outside the range of experimental data used for their calibration. Measurements on CO2-N2 inclusions of extremely low molar volume (about 40 cm3/mole) from the Furua Granulite Complex (Tanzania) are used as an example. Studies on fluid inclusions may therefore contribute, in a semi-quantitative way, to the improvement of equations of state for multi-component systems.

Surface desublimation of carbon dioxide from binary gas mixtures

The results of an experimental investigation of the time evolution of the main characteristics of the process of surface desublimation of carbon dioxide from N2-CO2 and He-CO2 gas mixtures are given.

Column Dynamics for Adsorption of Bulk Binary Gas Mixtures on Activated Carbon

Abstract Dynamics of adsorption from bulk N2-He, CH4-He, CO2-He, CO2-N2, and CO2-CH4 binary mixtures were measured in a column packed with the BPL activated carbon. The data were analyzed using an adiabatic, isobaric, constant pattern model of column adsorption in conjunction with a linear driving force model for the adsorbate mass transfer. It was found that the mass transfer coefficients for adsorption of CO2, CH4, and N2 were significantly lower during binary co-adsorption in the presence of each other than the corresponding pure component mass transfer coefficients in the presence of nonadsorbing helium. The reduction was more pronounced for the less strongly adsorbed species of the binary mixture. This kinetic interaction between the adsorbates could not be predicted a priori. Equilibrium isotherms for adsorption of pure N2, CH4, and CO2 and for adsorption of CO2-N2 and CO2-CH4 binaries were also measured on the carbon. The isotherms obeyed the Langmuir equation.