Region Of CH Research Articles

Vibrational Markers of a Model Circulating Metastatic Cells LLC-R9

Metastasis in oncological diseases remains one of the main reasons for negative prognosis regarding treatment. Any new data on the biophysical and biochemical characteristics of circulating metastatic cells will help to develop a concept for antimetastatic therapy. In this study, we found a number of differences in the spectroscopic and morphological features of circulating metastatic cells. FT-IR and Raman spectra cultivated by adhesive and de-adhesive methods (with the latter used as a model for metastatic cells) have shown spectroscopic features, namely in FT-IR spectra in the region of CH stretching vibrations, which are associated with structural rearrangements in the cell membrane, as well as changes in the intensity and position of the PO2− group vibration bands correlated with proliferative activity. The spectral features in the regions of OH stretching and Amide I vibrations as well as other spectral markers of the metastatic cells grown under different cultivation conditions were derived. Raman spectra showed a redistribution of the amino acid Tyr/Trp (tryptophan to tyrosine) ratio and in Tyr doublet intensity in the region of 500–900 cm−1, as well as varying glycogen levels in different cells. The spectroscopic markers are in accordance with biochemical data. CARS and confocal optical microscopy were applied to determine the state of the cells and the F-actin expression level, which turned out to be higher for adhesive cells in comparison with de-adhesive cells. The shape and the morphological properties of the cells differ drastically. The correlation of vibrational markers with biochemical data and the cytofluorometric method was discussed.

HD 121135: FEATURES OF ITS CHEMICAL COMPOSITION

Low metallicity star HD121135 ([Fe/H] =-1.5) have been investigated spectroscopically. Its atmos-pheric parameters and elemental abundances have beendetermined, including elements of neutron (n-) captureprocesses, which are the keys in the study of early Galaxyenrichment. Na, Mg, Ni, Co, Sr, Y, Zr, Mo, Ba, La, Ce, Pr,Sm, Eu, Gd, Dy, Ho, Os, Th abundances were calculatedusing the synthetic spectrum method, factoring in the hy-perfine structure (HFS) for the Eu II lines. Si, Ca, Sc abun-dances were determined using the equivalent widths oftheir lines. The carbon content was computed by the molec-ular synthesis fitting for the region of CH (4300-4330 AA).For the abundances determinations of C, Na, Mg, Ba, andTh the NLTE corrections have been applied.We have determined for the first time the abundancesof several n-capture elements and found that the behaviorsof these elements do not show a significant trend withincreasing atomic number. The elements ratios of [Eu/Fe]= 0.06, [Ba/Eu] = 0.13, [Sr/Ba] = - 0.05 do not support theHD121135 status as a r-process enrichment star. We haveobtained the thorium abundance [Th/Fe] = 0.26. The car-bon content confirms the effect of canonical additionalmixing in this star.

IR cryospectroscopic manifestation of complex formation between methoxyflurane and dimethyl ether in liquid Xe

The IR spectra of mixtures of methoxyflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Xe. The region of CH3 and CH stretching vibrations is examined taking into account the Fermi resonance effect. Comparative analysis of the experimental data and results of ab initio calculations show that the Cl2CH group of methoxyflurane is involved in complex formation which is stabilized by H-bond between H atom of this group and O atom of dimethyl ether predominantly.

Modulation of IgG1 immunoeffector function by glycoengineering of the GDP-fucose biosynthesis pathway.

Cross-linking of the Fcγ receptors expressed on the surface of hematopoietic cells by IgG immune complexes triggers the activation of key immune effector mechanisms, including antibody-dependent cell mediated cytotoxicity (ADCC). A conserved N-glycan positioned at the N-terminal region of the IgG CH 2 domain is critical in maintaining the quaternary structure of the molecule for Fcγ receptor engagement. The removal of a single core fucose residue from the N-glycan results in a considerable increase in affinity for FcγRIIIa leading to an enhanced receptor-mediated immunoeffector function. The enhanced potency of the molecule translates into a number of distinct advantages in the development of IgG antibodies for cancer therapy. In an effort to significantly increase the potency of an anti-CD20, IgG1 molecule, we selectively targeted the de novo GDP-fucose biosynthesis pathway of the host CHO cell line to generate >80% afucosylated IgG1 resulting in enhanced FcγRIIIa binding (13-fold) and in vitro ADCC cell-based activity (11-fold). In addition, this effective glycoengineering strategy also allowed for the utilization of the alternate GDP-fucose salvage pathway to provide a fast and efficient mechanism to manipulate the N-glycan fucosylation level to modulate IgG immune effector function.

Structural Study of Methylated and Non-Methylated Duplexes by IR Fourier Spectroscopy

Structure of the duplex consisting of 23 pairs of bases was studied before and after the methylation of two cytosine molecules from different chains of the duplex. The study was performed in a buffer solution using an IR Fourier spectrometer. The absorption bands corresponding to the duplex backbone were found to change their characteristics after the methylation. Firstly, the integrated intensity ratio of the absorption bands, S1044/S1085, decreased by a factor of 1.5. The absorption band at 1044 cm-1 corresponds to the COC bond of deoxyribose, and the band at 1085 cm-1 to the PO2symm.vibr bond. Secondly, a substantial shift of the absorption band 1085→1112 cm-1 (Δν = 27 cm-1) was observed. In addition, pronounced changes in the absorption region of CH stretching vibrations took place. In particular, shifting of some absorption bands assigned to the stretching vibrations of CH bonds; the 2979→2945.7 shift was equal to 33.3 cm-1. In addition to the indicated changes, some bands corresponding to the Z structure appeared in the methylated duplex. Thus, methylation of two cytosine molecules in the duplex leads to the order→order structural transition, most likely to the B→Z transition.

IR and FTMW-IR Spectroscopy and Vibrational Relaxation Pathways in the CH Stretch Region of CH3OH and CH3OD

Infrared spectra of jet-cooled CH(3)OD and CH(3)OH in the CH stretch region are observed by coherence-converted population transfer Fourier transform microwave-infrared (CCPT-FTMW-IR) spectroscopy (E torsional species only) and by slit-jet single resonance spectroscopy (both A and E torsional species, CH(3)OH only). Twagirayezu et al. reported the analysis of ν(3) symmetric CH stretch region (2750-2900 cm(-1); Twagirayezu et al. J. Phys. Chem. A 2010, 114, 6818), and the present work addresses the more complicated higher frequency region (2900-3020 cm(-1)) containing the two asymmetric CH stretches (ν(2) and ν(9)). The additional complications include a higher density of coupled states, more extensive mixing, and evidence for Coriolis as well as anharmonic coupling. The overall observed spectra contain 17 interacting vibrational bands for CH(3)OD and 28 for CH(3)OH. The sign and magnitude of the torsional tunneling splittings are deduced for three CH stretch fundamentals (ν(3), ν(2), ν(9)) of both molecules and are compared to a model calculation and to ab initio theory. The number and distribution of observed vibrational bands indicate that the CH stretch bright states couple first to doorway states that are binary combinations of bending modes. In the parts of the spectrum where doorway states are present, the observed density of coupled states is comparable to the total density of vibrational states in the molecule, but where there are no doorway states, only the CH stretch fundamentals are observed. Above 2900 cm(-1), the available doorway states are CH bending states, but below, the doorway states also involve OH bending. A time-dependent interpretation of the present FTMW-IR spectra indicates a fast (∼200 fs) initial decay of the bright state followed by a second, slower redistribution (about 1-3 ps). The qualitative agreement of the present data with the time-dependent experiments of Iwaki and Dlott provides further support for the similarity of the fastest vibrational relaxation processes in the liquid and gas phases.

Structure of host–guest complexes between dibenzo-18-crown-6 and water, ammonia, methanol, and acetylene: Evidence of molecular recognition on the complexation

Complexes of dibenzo-18-crown-6 (DB18C6, host) with water, ammonia, methanol, and acetylene (guest) in supersonic jets have been characterized by laser induced fluorescence (LIF), UV-UV hole-burning (UV-UV HB), and IR-UV double resonance (IR-UV DR) spectroscopy. Firstly, we reinvestigated the conformation of bare DB18C6 (species m1 and m2) and the structure of DB18C6-H(2)O (species a) [R. Kusaka, Y. Inokuchi, T. Ebata, Phys. Chem. Chem. Phys., 2008, 10, 6238] by measuring IR-UV DR spectra in the region of the methylene CH stretching vibrations. The IR spectral feature of the methylene CH stretch of DB18C6-H(2)O is clearly different from those of bare DB18C6 conformers, suggesting that DB18C6 changes its conformation when forming a complex with a water molecule. With the aid of Monte Carlo simulation for extensive conformational search and density functional calculations (M05-2X/6-31+G*), we reassigned species m1 and m2 to conformers having C(1) and C(2) symmetry, respectively. Also, we confirmed the DB18C6 part in species a of DB18C6-H(2)O to be "boat" conformation (C(2v)). Secondly, we identified nine, one, and two species for the DB18C6 complexes with ammonia, methanol, and acetylene, respectively, by the combination of LIF and UV-UV HB spectroscopy. From the IR spectroscopic measurement in the methylene CH stretching region, a similar conformational change was identified in the DB18C6-ammonia complexes, but not in the complexes with methanol or acetylene. The structures of all the complexes were determined by analyzing the electronic transition energies, exciton splitting, and IR spectra in the region of the OH, NH, and CH stretching vibrations. In DB18C6-ammonia complexes, an ammonia molecule is incorporated into the cavity of the boat conformation by forming "bifurcated" and "bidentate" hydrogen-bond (H-bond), similar to the case of the DB18C6-H(2)O complex. On the other hand, in the DB18C6-methanol and -acetylene complexes, methanol and acetylene molecules are simply attached to the C(1) and C(2) conformations, respectively. From the difference of the DB18C6 conformations depending on the type of the guest molecules, it is concluded that DB18C6 distinguishes water and ammonia from methanol and acetylene when it forms complexes, depending on whether guest molecules have an ability to form bidentate H-bonding.

The fine scale variability of dissolved methane in surface peat cores

Peat forming wetlands are globally important sources of the greenhouse gas CH 4. The variability of flux recordings from peatlands is however considerable and the distribution of CH 4 below the water table poorly described. Surface peat (0–500 mm below the water table) is responsible for the bulk of emissions and a localised region of intense CH 4 concentration may exist within this region but the structure of peat and presence of gas bubbles make the determination of in situ gas distributions problematic. We report on the in situ distribution and concentrations of CH 4, CO 2 and O 2 in surface bog peat cores using Quadrupole Mass Spectrometry and relate this to peat physical structure. Replicate cores collected in spring and autumn from both hollows and hummocks are used ( n = 10). CH 4 recorded in almost every profile was localised in intense peaks reaching concentrations up to 350 μM at depths where O 2 was absent. Each CH 4 peak had a coincident CO 2 peak with a minimum mean ratio of ∼20:1 (CO 2:CH 4) and we found more CH 4 beneath hollows than hummocks. In statistical comparisons CH 4 concentration and distribution differed significantly between profiles for each depth. We demonstrate that variability found within a single core is at least as great as that between cores collected across the bog. The distribution of CH 4 was negatively correlated with bulk density and in some cases the location of roots matched those of intense CH 4 concentration where bubbles had formed and been trapped. Our comparisons suggest variability in gas distribution is caused by a heterogenous peat structure that controls the movement of gas bubbles and contains localised hotspots of gas production. The small and fine root systems of vascular plants on the peatland surface may cause high levels of methanogenic activity in their vicinity and also represent a physical barrier capable of trapping CH 4 bubbles.

Growth and characterization of boron-doped [formula omitted] CVD homoepitaxial diamond films

The CH 4/H 2 ratio (growth rate) dependence of B-doped ( 1 1 1 ) homoepitaxial diamond film quality was investigated in the region of CH 4/H 2 ratio ⩽ 1 % and 10 ppm B 2H 6/H 2 ratio in terms of surface morphology, crystallinity, incorporation of impurities and electrical and optical properties. It was found that there are two different growth regimes, which depend on CH 4/H 2 ratio, in B-doped ( 1 1 1 ) film growth. In the region of low CH 4/H 2 ratio growth ⩽ 0.25 % , as CH 4/H 2 ratio increased, film quality was improved in spite of the same incorporation efficiency. This result is different from that of ( 0 0 1 ) diamond film growth. On the other hand, for high ( ⩾ 0.5 % ) CH 4/H 2 ratio growth, significant deterioration in the film quality was observed. Differences between ( 1 1 1 ) and ( 0 0 1 ) in B-doped film growth are discussed.

Fenchone, Camphor, 2-Methylenefenchone and 2-Methylenecamphor: A Vibrational Circular Dichroism Study

We report and discuss the infrared (IR) vibrational circular dichroism (VCD) spectra of the enantiomeric pairs of the olefin derivatives of fenchone (1,3,3-trimethyl-2-methylenebicyclo[2.2.1]heptane) and camphor (1,7,7-trimethyl-2-methylenebicyclo[2.2.1]heptane), respectively, together with those of the parent molecules. The VCD spectra were taken in three spectral regions: the mid-IR region, encompassing the fundamental deformation modes, the region of CH-stretching fundamental modes and the NIR-region between 1100 and 1300 nm, which corresponds to the second CH-stretching overtone. The VCD and absorption spectra in the first two regions are analyzed by use of current density functional theory (DFT) calculations. The NIR region is analyzed by a protocol that consists of the use of DFT-based calculations and in assuming local mode behavior: the local mode approach is found appropriate for interpreting the absorption spectra and, for the moment, acceptable for calculating NIR-VCD spectra. The analysis of the first region allows us to track the contribution of the C=O group in the vibrational optical activity of C-C stretching modes; notable differences are indeed found in olefins and ketones. On the contrary, in the other two regions the VCD spectra of olefins and ketones are more similar: in the normal mode region of CH stretching fundamentals the spectra are determined by the mutual orientation of the CH bonds; in the second overtone local mode region olefins and ketones signals show some differences.

Application of near Infrared Spectroscopy to Assessments of Colour Change in Plantation-Grown Eucalyptus Grandis Wood Subjected to Heat and Steaming Treatments

The relationships between colour parameters and chemical components of Eucalyptus grandis wood under a steaming and a heating process were examined by near infrared (NIR) spectroscopy to assess the best drying conditions. The results indicated that: 1) under steaming conditions, the second derivatives of absorption bands due to OH in the crystalline region of cellulose and CH in hemicellulose presented statistically significant positive correlation values for L* or b* and a decrease in lignin might be the reason leading to the colour changes; 2) under heat-treated conditions, the colour darkening process in wood was often accompanied by a severe collapse phenomena, especially at the 100°C condition. It was found spectroscopically that the concentrations of cellulose and hemicellulose were increased relatively by the collapse occurring and that lignin decreased with the elevated drying temperature. The crystalline regions in cellulose and hemicellulose were related to “blueness” (partial darkness) of E. grandis caused by the drying process.

Novel and global approach of the complex and interconnected phenomena related to the contact line movement past a solid surface from hydrophobized silica gel

In this work a generalized hydrodynamic theory for water flow into a mesoporous matrix from hydrophobized silica gel is suggested. Although we examine a fluid dynamics problem, the motion of the water–gas–solid contact line past a hydrophobized silica gel surface, motivation for such research derives from the investigation of a novel principle of mechanical energy dissipation, called surface dissipation, and its attached machine element, named a colloidal damper (CD). Similar to a hydraulic damper, this absorber has a cylinder–piston structure, but oil is replaced by a colloid consisting of a mesoporous matrix and a lyophobic liquid. Here, the mesoporous matrix is from silica gel modified by linear chains of alkyldimethylchlorosilanes and water is the associated lyophobic liquid. Mainly, the colloidal damper energy loss can be explained by the dynamic contact angle hysteresis in advancing (liquid displaces gas) and receding motion (gas displaces liquid); such hysteresis occurs due to the geometrical and chemical heterogeneities of the solid surface. Although this new kind of dissipation could be attractive for many applications, the subject remains almost unexplored in the scientific literature. Many different, complex, and interconnected aspects are related to this subject: capillary hydrodynamics, slippage effect, contact angle hysteresis, estimation of dissipated energy, thickness optimization of the grafted layer on the surface of the mesoporous matrix, etc. For this reason, a novel and global approach to all the complex and interconnected phenomena related to the contact line movement past a solid surface from hydrophobized silica gel is proposed. Our approach has a modest experimental basis but this is compensated for with rich references to other experimental and theoretical work oriented to the study of surface phenomena in such systems. We tried to sort the existing results and to find the right place for each in building our global view of the problem. This work is structured as follows. The measurement technique of the hysteresis loop is described. From experimental data one calculates the dissipated energy versus length of the grafted molecule on the silica gel surface. These results are justified by flow analysis. Generalized hydrodynamic theory means here that the basic structure of the Navier–Stokes equations is kept, but in order to include the relation between macroscopic flow and molecular interactions, slip is allowed on the solid wall. The nanopillar architecture of the silica gel hydrophobic coating is described. Concepts of slip and contact angle hysteresis are detailed and their connection is revealed. During adsorption, water penetrates the pore space by maintaining contact with the top of the coating molecules (region of CH 3 groups); after that, water is forced into and partially or totally fills the space between molecules (region of CH 2 groups). In such circumstances, at the release of the external pressure, desorption occurs. An original energetic-barriers approach is proposed to understand the filling of the nanosize canals which occur in the hydrophobic grafted layer. Employing this energetic-barriers approach, one finds the optimum length of the grafted molecule which maximizes the dissipated energy of the CD reversible cycle. Such results are useful for the appropriate design of ultrahydrophobic surfaces in general, and for the optimal design of a hydrophobic coating of a mesoporous matrix destined for CD use.

Rovibrational analysis of the $nu;4 and $nu;5+$nu;9 bands of CHCl2F

The infrared spectrum of CHCl 2 F has been measured with a new, very high resolution Fourier transform infrared spectrometer, the Bruker IFS 120 HR Zürich Prototype (ZP) 2001. The spectrum was recorded with a resolution of 0.0007 cm −1 in the range 600–2300 cm −1 at room temperature. The assignment of the rovibrational transitions has been carried out with the Giessen interactive Loomis–Wood program developed by Winnewisser et al. [J. Mol. Spectrosc. 136 (1989) 12] and the least squares adjustment has been performed with the Zürich wang program. The spectrum has been analyzed in the ν 4 region of CH 35 Cl 2 F ( ν ̃ 0 =744.474 cm −1 ) and the ν 5 + ν 9 regions of CH 35 Cl 2 F ( ν ̃ 0 =829.084 cm −1 ) and CH 35 Cl 37 ClF ( ν ̃ 0 =825.027 cm −1 ) using an effective Hamiltonian. Both bands are important to understand the absorption behavior of the fluorochlorohydrocarbon CHCl 2 F, important in the context of atmospheric pollution as well as in laser chemistry. Local perturbations have been identified in both bands. The results are discussed in relation to molecular parity violation in the case of the chiral isotopomer CH 35 Cl 37 ClF.

The coronal hole creation: theory and simulation

The possibility, that sufficiently fast plasma flows may be able to create channels (coronal holes, hereafter - CH) for their escape from the solar magnetic field network is investigated. Using a dissipative two-fluid code in which the flows are treated at par with the currents, we have studied the expected CH formation for representative test cases. We give the simulation results for: 1) the interaction of primary flows with 2 neighboring arcade-like ambient magnetic field structures, and 2) the primary flow interaction with 4 neighboring arcade-like structures. For the former case, though there is some dissipation of flow energy, the coronal hole is cold and practically empty compared to the closed coronal structures. In the latter case, the combined effect of the structure-structure and flow-structure interaction creates a highly divergent, and multiple looped stretched 2-dimensional coronal hole with a hot base: the velocity field is maximum in the central region of CH at some distance away from the base unlike the coronal hole formed out of the two arcade structure.

Chromium in amorphous hydrogenated carbon based thin films prepared in a PACVD process

The deposition of Cr-containing amorphous hydrogenated carbon (a-C:H) thin films on Si and Cu substrates in a radio frequency (rf) and middle frequency (mf) plasma activated chemical vapour deposition (PACVD) process is described. Negative DC bias voltage at the substrate and the composition of the process gas are two significant parameters in the deposition process. By applying a higher bias voltage the growth rate is increased. The dependence on the ratio of CH 4 to Ar shows a saturation effect in the region of high CH 4 concentration. This shows the significant contribution of an ion current to the film growth and a rf/mf power limited ion current in the selected parameter range. A decrease of the Cr content in the a-C:H films by increasing the CH 4 to Ar flow ratio is measured by XPS while a correlation of the density of the electronic states at the Fermi level with the metal content in the a-C:H matrix is observed by UPS. No significant change in the ratio of sp 2 to disordered bonded carbon atoms in the films deposited with the two methods is observed by Raman spectroscopy. Ageing tests of the samples at 250°C in air showed the increase of the solar absorption as well as the reduction of the thermal emission after 80 h treatment. These results show a total suppression of the copper diffusion through the diffusion barrier in the multilayer system.

Two-dimensional temperature determination in the exhaust region of a laminar flat-flame burner with linear Raman scattering

For planar temperature measurements in combusting flows, the well-established laser Raman technique has been further developed to provide two-dimensional local resolution. After excitation with a frequency-doubled Nd:YAG laser, the anti-Stokes and the Stokes Raman signals of the vibrational Q branch of molecular N(2) were detected at 473.3 and 607.3 nm, respectively. From the ratio of the two images, two-dimensional temperature distributions have been obtained by application of an analytical function, which was determined from theoretically calculated Raman spectra. Time-averaged measurements have been performed in the exhaust region of an atmospheric-pressure laminar CH(4)/air flat-flame burner for different equivalence ratios. The accuracy and precision of the results are discussed in combination with the prospects for time-resolved single-pulse measurements.

Real-Time Photoacoustic Signal Analysis in a Gas-Phase Spectrophone: A Feasibility Study

A digital signal processing (DSP) system has been constructed for the acquisition of intracavity dye laser photoacoustic spectra (ICL-PAS). The DSP system permits observation of the real-time PA pulse, an arrangement which facilitates the adjustment of all spectral acquisition parameters as well as signal processing for noise reduction. Sample spectra of the real-time PA pulse illustrate the improvements possible with Fourier filtering and time-averaging. Spectra of the region of the fifth CH stretching overtone of ethene, benzene, and propane in the gas phase are presented. The system offers significant potential advantages in signal quality, signal processing, and construction cost over the more conventional lock-in amplifier detection method.

Absolute photoabsorption (6–350 eV) and photoionization (11–80 eV) of methyl chloride using dipole electron scattering and synchrotron radiation spectroscopies

Abstract Absolute oscillator strenghts (cross sections) have been measured for the photoabsorption of CH 3 Cl at low resolution (1 eV fwhm) in the equivalent photon energy range from 6 to 350 eV and at high resolution (0.05 eV fwhm) from 6 to 50 eV using dipole (e,e) spectroscopy. In the valence shell region of CH 3 Cl, from the first ionization threshold to 80 eV, the photoionization efficiency, ionic photofragmentation branching ratios and absolute partial oscillator strengths for molecular and dissociative photoionization have been determined by dipole (e,e+ion) spectroscopy. The major ionic pathways of the dipole induced breakdown scheme of CH 3 Cl are predicted from these results and the partial photoionization oscillator strengths for production of the valence shell electronic states of CH 3 Cl + are estimated. The photoabsorption data have been combined with photoelectron branching ratios for Ch 3 Cl, measured using monochromated synchrotron radiation at photon energies from 21 to 72 eV, to obtain partial photoionization oscillator strengths for production of the electronic states of CH 3 Cl + , which are compared with the partial oscillator strength estimates derived from the (e,e+ion) data.

The valence shell photoabsorption of the linear alkanes, C nH 2 n+2 ( n=1–8): absolute oscillator strengths (7–220 eV)

The absolute valence shell photoabsorption spectra of the first eight members of the homologous linear (normal) alkane series, CH 4 to C 8H 18, have been obtained from electron energy loss measurements using dipole (e, e) spectroscopy at a resolution of 1 eV fwhm in the equivalent photon energy range 7–220 eV. Absolute oscillator strengths (transition probabilities) for discrete and continuum photoabsorption transitions have been determined throughout the entire energy range. The lower energy regions (7–50 eV) of the spectra have also been studied at high resolution (0.048 eV fwhm), and essentially all the features observed in the discrete excitation region of CH 4, C 2H 6, C 3H 8, and C 4H 10 can be reasonably assigned to Rydberg transitions by using quantum defects and the transferability of term values. The quite good agreement between the present results and the constrained dipole oscillator strength distribution (DOSD) values computed by Jhanwar, Meath, and MacDonald [Can. J. Phys. 59 (1981) 185] shows that the techniques utilized in constructing the DOSDs provide a reasonably satisfactory estimate of the absolute photoabsorption oscillator strengths for the linear alkanes.

Near-critical-region equilibria of the CH 4-CO 2-H 2S system

Morris J.S. and Byers C.H., 1991. Near-critical-region equilibria of the CH 4-CO 2-H 2S system. Fluid Phase Equilibria, 66: 291-308. To acquire data for assessing a proposed syngas purification system, an apparatus has been built to measure vapor-liquid equilibria of binary and multicomponent systems in the critical region of CH 4-CO 2-H 2S mixtures. To test the experimental device and supplement existing data, binary systems were studied between 270.0 and 288.2 K. Predictions of the Peng-Robinson (PR) and Redlich-Kwong-Soave (RKS) equations of state were compared with binary and ternary data using the ASPEN simulator parameter regression utilities to determine binary interaction parameters from binary data. Calculated phase equilibria for CH 4-CO 2 mixtures based on both equations agree to within 3.5%, while the difference in either case with experimental liquid phase compositions is less than 15%. Similar results were obtained for CO 2-H 2S mixtures. Experimental values were less reliable for CH 4-H 2S binary interaction parameters. In predicting the ternary mixtures, total pressure is generated using both equations of state. Estimates by the PR equation were significantly better than those generated by the RKS equation (12% deviation versus 29% deviation) for the temperature and pressure range of the study.