Presence Of CH Research Articles

The Habitability of Proxima Centauri b: Environmental States and Observational Discriminants.

Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and use instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b but to other terrestrial planets orbiting M dwarfs. Thermal phase curves may provide the first constraint on the existence of an atmosphere. We find that James Webb Space Telescope (JWST) observations longward of 10 μm could characterize atmospheric heat transport and molecular composition. Detection of ocean glint is unlikely with JWST but may be within the reach of larger-aperture telescopes. Direct imaging spectra may detect O4 absorption, which is diagnostic of massive water loss and O2 retention, rather than a photosynthetic biosphere. Similarly, strong CO2 and CO bands at wavelengths shortward of 2.5 μm would indicate a CO2-dominated atmosphere. If the planet is habitable and volatile-rich, direct imaging will be the best means of detecting habitability. Earth-like planets with microbial biospheres may be identified by the presence of CH4—which has a longer atmospheric lifetime under Proxima Centauri's incident UV—and either photosynthetically produced O2 or a hydrocarbon haze layer. Key Words: Planetary habitability and biosignatures—Planetary atmospheres—Exoplanets—Spectroscopic biosignatures—Planetary science—Proxima Centauri b. Astrobiology 18, 133–189.

Stringent upper limit of CH4 on Mars based on SOFIA/EXES observations

Discovery of CH4 in the Martian atmosphere has led to much discussion since it could be a signature of biological and/or geological activities on Mars. However, the presence of CH4 and its temporal and spatial variations are still under discussion because of the large uncertainties embedded in the previous observations. We performed sensitive measurements of Martian CH4 by using the Echelon-Cross-Echelle Spectrograph (EXES) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) on 16 March 2016, which corresponds to summer (Ls = 123.2∘) in the northern hemisphere on Mars. The high altitude of SOFIA (~13.7 km) enables us to significantly reduce the effects of terrestrial atmosphere. Thanks to this, SOFIA/EXES improves our chances of detecting Martian CH4 lines because it reduces the impact of telluric CH4 on Martian CH4, and allows us to use CH4 lines in the 7.5 μm band which has less contamination. However, our results show no unambiguous detection of Martian CH4. The Martian disk was spatially resolved into 3 × 3 areas, and the upper limits on the CH4 volume mixing ratio range from 1 to 9 ppb across the Martian atmosphere, which is significantly less than detections in several other studies. These results emphasize that release of CH4 on Mars is sporadic and/or localized if the process is present.

Chromium isotope fractionation during Cr(VI) reduction in a methane-based hollow-fiber membrane biofilm reactor

Chromium (Cr) isotope fractionation analysis is a promising tool for monitoring Cr(VI) reduction in natural aqueous systems. In addition, large amounts of CH4 in natural aqueous sediments are oxidized to CO2 through methanotrophs, thereby mitigating emissions to the atmosphere. However, the investigations on the Cr(VI) reduction process with methanotrophs, and the associated Cr isotope fractionation patterns are scarce. In this study, we have shown that Cr(VI) reduction can occur in the presence of CH4 as the sole electron donor in a hollow-fiber membrane reactor (HfMBR) after direct bacteria enrichment from sediment samples. Products of the methane oxidation by the methanotrophs are used by microbes to reduce Cr(VI) as shown by the progressive increase in δ53Cr with time in the CH4 feed reactor. The isotope fractionation factor (ε) of −2.62 ± 0.20‰ was obtained from the application of the Rayleigh distillation model. The results of Cr isotope fractionation analysis also explained the decrease of Cr(VI) concentration in the N2 feed reactor, where the δ53Cr values remained steady in the first two weeks but significantly increased in the last two weeks, indicating that physical adsorption and subsequent Cr(VI) reduction occurred. This study extended the application of Cr isotope fractionation, showing the suitability of this method for clarifying different Cr(VI) removal processes.

Effect of CH4 on the CO2 breakthrough pressure and permeability of partially saturated low-permeability sandstone in the Ordos Basin, China

The behavior of CO2 that coexists with CH4 and the effect of CH4 on the CO2 stream need to be deeply analyzed and studied, especially in the presence of water. Our previous studies investigated the breakthrough pressure and permeability of pure CO2 in five partially saturated low-permeability sandstone core samples from the Ordos Basin, and we concluded that rocks with a small pore size and low permeability show considerable sealing capacity even under unsaturated conditions. In this paper, we selected three of these samples for CO2-CH4 gas-mixture breakthrough experiments under various degrees of water saturation. The breakthrough experiments were performed by increasing the gas pressure step by step until breakthrough occurred. Then, the effluent gas mixture was collected for chromatographic partitioning analysis. The results indicate that CH4 significantly affects the breakthrough pressure and permeability of CO2. The presence of CH4 in the gas mixture increases the interfacial tension and, thus, the breakthrough pressure. Therefore, the injected gas mixture that contains the highest (lowest) mole fraction of CH4 results in the largest (smallest) breakthrough pressure. The permeability of the gas mixture is greater than that for pure CO2 because of CH4, and the effective permeability decreases with increased breakthrough pressure. Chromatographic partitioning of the effluent mixture gases indicates that CH4 breaks through ahead of CO2 as a result of its weaker solubility in water. Correlations are established between (1) the breakthrough pressure and water saturation, (2) the effective permeability and water saturation, (3) the breakthrough pressure and effective permeability, and (4) the mole fraction of CO2/CH4 in the effluent mixture gases and water saturation. These results deepen our understanding of the multi-phase flow behavior in the porous media under unsaturated conditions, which have implications for formulating emergency response plans for gas leakage into unsaturated zones. Finally, knowing the flow characteristic of gas mixture can guide CO2 storage, CO2-EOR and CO2-ECBM projects. Future studies should pay attention to the effects of saline water with different salt types and concentrations on the multi-phase flow behavior with applications to geological CO2 storage and energy storage using CH4.

Geochemistry, fluid inclusion and stable isotope constraints (C and O) of the Sivrikaya Fe-skarn mineralization (Rize, NE Turkey)

The Sivrikaya Fe-skarn mineralization is hosted by dolomitic limestone layers of Late Cretaceous volcano-sedimentary unit, comprised of andesite, basalt and their pyroclastites, including, sandstone, shale and dolomitic limestone layers. Intrusion of the Late Cretaceous–Eocene İkizdere Granitoid in the volcano–sedimentary unit resulted in skarn mineralization along the granitoid–dolomitic limestone contact. The ore is associated with exoskarns, and mineralization is characterized by early anhydrous garnet and pyroxene with late hydrous minerals, such as epidote, tremolite, actinolite and chlorite. The ore minerals are mainly magnetite and hematite, with minor amounts of pyrite and chalcopyrite. The composition of garnet and pyroxene in the exoskarn is Adr79.45−99.03Grs0−17.9Prs0.97−2.65 and Di69.1−77.1Hd22.2−29.8Jhn0.6−1.4, respectively, and abundances of magnetite in the ore suggest that the Fe-skarn mineralization formed under relatively oxidized conditions.Homogenization temperatures (Th) of all fluid inclusions and calculated salinity content are in the range of 166 °C–462 °C and 0.35–14.3 wt% NaCl equ., respectively. Well-defined positive correlation between Th and salinity values indicates that meteoric water was involved in the hydrothermal solutions. Eutectic temperatures (Te) between −40.8 °C and −53.6 °C correspond to the presence of CaCl2 in the early stage of fluid inclusions. On the other hand, the Te temperatures of later-stage fluid inclusions, in the range of −38 °C and −21.2 °C, correspond to the presence of MgCl2, FeCl2, KCl and NaCl type salt combinations. None of the fluid inclusions were found to contain separated gas phases in microscopy observations. However, a limited amount of dissolved CH4 was identified in the early stage, high temperature fluid inclusions using Raman spectroscopic studies.Δ18O values in both dolomitic limestone (10.8–12.5‰) and skarn calcite (7.6–9.8‰) were highly depleted compared to the typical δ18O values of marine limestones. Decreases in δ18O values are accepted as an indication of dilution by meteoric water because retrograde brecciation of garnet, magnetite and breccia filling epidote and quartz in volcanic host rocks are an indication of increasing permeability, allowing infiltration of meteoric water. Highly depleted δ13C isotopes (up to −6.5‰) of dolomitic limestone, indicate that organic matter in carbonates had an effect on the decreasing isotopic ratios. The presence of CH4 and CH2 in fluid inclusions can be explained by the thermal degradation of these organic materials.

CO2 adsorption over modified AC samples: A new methodology for determining selectivity

Activated carbon (AC) based adsorbents having high and stable CO2 adsorption capacity with enhanced CO2 selectivity in presence of CH4 were developed. Alkali modified AC samples were prepared, their CO2 adsorption capacities were measured, a new methodology for selective adsorption capacity determination under multicomponent gas mixture flow was developed, and the results were analyzed to determine the preparation procedure yielding optimum adsorbent design. Two groups of adsorbents were prepared by K2CO3 impregnation on air and HNO3 oxidized forms of a commercial AC followed by calcination at various temperatures. The resulting adsorbents were named according to calcination temperatures as ACxK-calT. The highest CO2 adsorption capacity was measured on AC3K-300 sample as 110mg/g adsorbent at 1000mbar CO2 and 25°C. CO2 adsorption was confirmed reversible, whereas CH4 adsorption was found partially irreversible. The highest mass based CO2:CH4 selectivity, ca. 3.7, was achieved over AC2K-200 at 25°C for the 50%CO2-50%CH4 mixture. AC2K-200 was further tested at higher total pressures, for 0–5000mbar pressure range, at 25°C. CO2 adsorption capacity was measured as 197mg/g adsorbent at 5000mbar CO2. Among Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models, D-R was found to be the most successful one explaining CO2 adsorption behavior of AC samples.

Presence of π…π and C[sbnd]H…π interactions in the new Schiff base 2-{(E)-[(3-tert-butyl-1-phenyl-1H-pyrazol-5-yl)imino]methyl}phenol: Experimental and DFT computational studies

A combined theoretical and experimental study on the structure, infrared and UV–Vis data of 2-{(E)-[(3-tert-butyl-1-phenyl-1H-pyrazol-5-yl)imino]methyl}phenol (3), is presented. Theoretical geometry optimization and its IR spectrum were carried out using the Density Functional Theory (DFT), while for the theoretical UV–Vis spectrum, the Time-Dependent DFT (TD-DFT) method was used. The supramolecular analysis of the compound evidenced the presence of π … π interactions between the phenol and pyrazole rings and the presence of CH … π interactions between the methyl group and the phenyl rings which form chains of molecules parallel to the plane (100).

Combined fast selective reduction using Mn-based catalysts and nonthermal plasma for NOx removal.

In this study, the concept of fast SCR for NO reduction with NH3 as reducing agent is realized via the combination of nonthermal plasma (NTP) with Mn-based catalyst. Experimental results indicate that 10% wt. Mn-Ce-Ni/TiO2 possesses better physical and chemical properties of surface, resulting in higher NO removal efficiency if compared with 10% wt. Mn-Ce/TiO2 and 10% wt. Mn-Ce-Cu/TiO2. Mn-Ce-Ni/TiO2 of 10% wt. achieves 100% NOx conversion at 150°C, while 10% wt. Mn-Ce/TiO2 and 10% wt. Mn-Ce-Cu/TiO2 need to be operated at a temperature above 200°C for 100% NOx conversion. However, NO conversion achieved with 10% wt. Mn-Ce-Ni/TiO2 is significantly reduced as H2O(g) and SO2 are introduced into the SCR system simultaneously. Further, two-stage system (SCR with DBD) is compared with the catalyst-alone for NOx conversion and N2 selectivity. The results indicate that 100% NOx conversion can be achieved with two-stage system at 100°C, while N2 selectivity reaches 80%. Importantly, NOx conversion achieved with two-stage system could maintain >95% in the presence of C2H4, CO, SO2, and H2O(g), indicating that two-stage system has better tolerance for complicated gas composition. Overall, this study demonstrates that combining NTP with Mn-based catalyst is effective in reducing NOx emission at a low temperature (≤200°C) and has good potential for industrial application.

Influence of chlamydia infection on DNA damage in patients with cervical cancer.

e17020 Background: The role of Chlamydia trachomatis (Ch. tr.) in development of cervical neoplasia is widely discussed. However, molecular mechanisms of Ch. tr. contribution to carcinogenesis are poorly studied. The purpose of the study was to analyze degrees of DNA damage in blood leucocytes in patients with cervical cancer with Ch. tr. infection and in non-infected patients and healthy women. Methods: DNA damage was assessed by the comet assay, the alkaline single-cell gel electrophoresis (20 min, 300 mA, 20 V, 2 V/cm, 4°C) allowing detection of DNA base modifications leading to alkali-labile sites. The preparations were stained with ethidium bromide solution and microscoped (Axio Imager M2, Zeiss) at the excitation wavelength 520 nm and emission wavelength 640 nm. 200 cells were analyzed in each preparation. Percentage of DNAs in the comet tail (T%DNA) was used as an indicator of DNA damage. DNA damage was assessed in 14 patients with cervical cancer and in 13 healthy women. The data were analyzed using Exsel and Statistika 6.0 programs and Mann-Whitney U test and Student's t-test. Results: Mean T%DNA in 8 cervical cancer patients non-infected with Ch. tr. was 4.35±0.63, being significantly (р=0.012580) higher (by 53.7%) than in women without oncopathology (2.83±0.20). The value in infected patients was 10.44±0.11 which was significantly higher than in non-infected patients (by 2.4 times, р=0.000056) and in healthy women (by 3.7 times, р=0.000000). Thus, presence of Ch. tr. was associated with more than 2 times increase in DNA damage in cervical cancer patients. The results are consistent with previously reported data of cell culture studies according to which chlamydia causes histone modification and DNA double strand breaks [Chumduri C. et al., 2013]. Conclusions: The results confirm the role of chlamydia infection in DNA damage in blood cells in cervical cancer patients which promotes malignant development in organs of the female reproductive system.

Synthesis of hybrid paper sheets with enhanced air barrier and antimicrobial properties for food packaging

Paper sheets made from bagasse pulp have been modified using nanocellulose (NC) obtained from the same raw material. Modification of paper sheets have been carried out either through loading of paper with different concentrations of NC and antibacterial agent, Chitosan (Ch) during making sheets, or by surface coating of the paper. Crystals of NC extracted using concentrated sulfuric acid from bagasse pulp were found to have crystallinity index (CrI) 90%. Morphology of obtained NC has been confirmed by TEM and images revealed formation of NC crystals with large size distribution ranges from 4 to 60nm. Mechanical properties and air permeability of paper sheets loaded with different ratios of NC and Ch have been investigated. The results showed that presence of NC did not negatively affect the obtained modified paper sheets, while air permeability decreased with adding 8% NC to paper matrix. On the other hand, surface coverage of paper sheets with NC greatly reduced air permeability. Antimicrobial investigations carried out by optical density method indicated that presence of Ch in the paper sheets as an additive or in a coating formulation enhanced paper resistance to different microorganisms especially those causing food poisoning. The current study confirms that the modified paper can have potential application in food packaging.

Determination of pressure in aqueo-carbonic fluid inclusions at high temperatures from measured Raman frequency shifts of CO2

Due to the presence of additional volatiles and/or electrolytes in CO 2 -H 2 O fluids, the total pressure of many natural aqueo-carbonic fluid inclusions at high temperatures as determined using microthermometry is usually made with considerable uncertainty. In this paper, we present the results of our high P - T in situ Raman scattering study of high-density aqueo-carbonic fluids, with and without a small amount of CH 4 and NaCl, whose objective is to derive a new method for pressure determination in aqueo-carbonic fluid inclusions at high temperatures. The measurement of the Fermi dyad bands at temperatures up to 400 °C and pressures up to 1200 MPa is described. The manner in which the frequency shifts and intensity of Raman bands are governed by pressure, temperature, presence of CH 4 in carbonic and NaCl in aqueous fluids is discussed. From the monotonic dependence of the frequency shifts of the lower Fermi dyad band ν − and the Fermi resonant splitting D ( D = ν + − ν − ) with pressure and temperature, the pressure (in MPa) in aqueo-carbonic fluid inclusions at elevated temperatures can be determined directly by using the following two polynomial equations: P ( MPa ) = − 16 + 1 . 232 × T − 53 . 72 × ( Δ ν − ) − 1 . 83 × 10 − 3 × T 2 + 24 . 46 × ( Δ ν − ) 2 − 0 . 292 × T × ( Δ ν − ) , P ( MPa ) = − 26 + 1 . 501 × T + 193 . 24 × ( Δ D ) − 1 . 61 × 10 − 3 × T 2 + 5 . 436 × ( Δ D ) 2 + 0 . 158 × T × ( Δ D ) , where T is in °C, Δ ν − and Δ D represent frequency shifts (in cm −1 ) of the lower band and the resonant splitting relative to the reference values measured at 23 °C and 6 MPa, respectively. Based on the attainable accuracy of the fitted peak positions and the results from fitting of Raman frequency shifts’ dependence with pressure and temperature, the uncertainty in pressure determination is about 50 MPa for pressures determined from ν − and 40 MPa from that determined from D .

Gate opening effect of zeolitic imidazolate framework ZIF-7 for adsorption of CH4 and CO2 from N2

Measurements of S-shaped adsorption isotherm as evidence of ZIF-7 gate opening in the presence of CH4 at 1245 kPa.

A Geochemical Model of Fluids and Mineral Interactions for Deep Hydrocarbon Reservoirs

A mutual solubility model for CO2-CH4-brine systems is constructed in this work as a fundamental research for applications of deep hydrocarbon exploration and production. The model is validated to be accurate for wide ranges of temperature (0–250°C), pressure (1–1500 bar), and salinity (NaCl molality from 0 to more than 6 mole/KgW). Combining this model with PHREEQC functionalities, CO2-CH4-brine-carbonate-sulfate equilibrium is calculated. From the calculations, we conclude that, for CO2-CH4-brine-carbonate systems, at deeper positions, magnesium is more likely to be dissolved in aqueous phase and calcite can be more stable than dolomite and, for CO2-CH4-brine-sulfate systems, with a presence of CH4, sulfate ions are likely to be reduced to S2−and H2S in gas phase could be released after S2−saturated in the solution. The hydrocarbon “souring” process could be reproduced from geochemical calculations in this work.

Inclusion and point defect characteristics of Marange graphite-bearing diamonds after high temperature annealing

This study gives an analysis of the effect of low-pressure, high-temperature annealing on the infrared, Raman, and photoluminescence (PL) features, as well as the inclusion characteristics, of cubo-octahedral diamond plates from the Marange deposits in Zimbabwe. The samples showed strong inclusion-related zoning which consists of micron-sized particles identified as graphite and these grew noticeably larger with annealing at temperatures of 300°C to 1700°C. Within the natural diamonds, the graphite inclusions (detected by Raman spectroscopy) had a grain size of approximately 1μm, which increased to 3μm after 1200°C and 14μm after 1700°C annealing and their hexagonal morphology was discernible. From the geometry of these grains, we determined that they were oriented within the {111} family of planes. The infrared absorption and PL spatial maps were collected after every temperature step to study the effects of annealing on the defects, and photomicrographs and Raman spectra were collected to study the graphite inclusions. The graphitic inclusions grew much larger as the stressed diamond surrounding them converted to graphite. Many nitrogen-related optical centers, including NV− and H3 are no longer detected after high temperature annealing within the cuboid regions as these may have been transformed to hydrogen-bearing complexes such as NVH and N2VH. The presence of CH4 is detected in the unannealed Marange diamonds, but was no longer observed in Raman spectra after 1200°C annealing. This CH4 disappearance along with changes in inclusion morphology could provide a method to detect heat treatment if these mixed-habit samples are sourced to create treated black gem diamond.

Dynamic and equilibrium-based investigations of CO2-removal from CH4-rich gas mixtures on microporous adsorbents

The removal of CO2 from CH4-rich gas mixtures is one of the key technologies for CH4-production and purification (Silva et al., Microporous Mesoporous Mat 158:219, 2012; 187:100, 2014). For this purpose, different techniques like adsorption on porous solids, membrane technologies or absorptive methods are employed (Scholes et al., Fuel 96:15, 2012; Sridhar et al., Sep Purific Rev, 2007). In any case, the appropriate separation technique as well as the optimal separation active material must be found. However, the choice of the optimal ensemble depends on many parameters, particularly CO2-concentration, the presence of other components i.e., water, the content of higher hydrocarbons, the pressure of the raw gas and the gas throughput (Andriani et al., Appl Biochem Biotechnol 172:4, 2014). In this work the focus is put on adsorption technologies. Therefore, three different commercially available adsorbents were investigated in the context of their applicability in separation processes by adsorption. One zeolite, a commercial activated carbon and a carbon molecular sieve were chosen as adsorbents. The classification of the materials is based on the characterization with N2 at 77 K, a series of adsorption isotherms and breakthrough curves (CO2 in the presence of CH4). Isotherms were measured by a volumetric method at temperatures of 293–333 K and pressures up to 2 MPa. Due to very long equilibration times in case of CH4 on the carbon molecular sieve, isotherm data for 313–353 K up to 1 MPa were taken from reference (Moller et al., Chem. Ing. Tech 86:1–2, 2014). Dynamic experiments were carried out with a ternary mixture of He/CH4/CO2 (molar fractions: 0.80/0.15/0.05) at 0.5 MPa and 293 K. A simplified mathematical model, based on mass- and energy balances, was applied to simulate breakthrough curves on packed adsorbent beds. The suitability of the investigated adsorbents for CO2-removal by adsorption was classified with the help of the obtained experimental data. It can be shown, that an evaluation of the separation performance of such materials, based only on textural parameters like the BET surface area or N2-isotherms at 77 K is limited in its confidence and can cause a substantial misinterpretation of the whole separation process.

Effective diffusion coefficients of gas mixture in heavy oil under constant-pressure conditions

We develop a method to determine the effective diffusion coefficient for each individual component of a gas mixture in a non-volatile liquid (e.g., heavy oil) at high pressures with compositional analysis. Theoretically, a multi-component one-way diffusion model is coupled with the volume-translated Peng-Robinson equation of state to quantify the mass transfer between gas and liquid (e.g., heavy oil). Experimentally, the diffusion tests have been conducted with a PVT setup for one pure CO2-heavy oil system and one C3H8–CO2-heavy oil system under constant temperature and pressure, respectively. Both the gas-phase volume and liquid-phase swelling effect are simultaneously recorded during the measurement. As for the C3H8–CO2-heavy oil system, the gas chromatography method is employed to measure compositions of the gas phase at the beginning and end of the diffusion measurement, respectively. The effective diffusion coefficients are then determined by minimizing the discrepancy between the measured and calculated gas-phase composition at the end of diffusion measurement. The newly developed technique can quantify the contributions of each component of mixture to the bulk mass transfer from gas into liquid. The effective diffusion coefficient of C3H8 in the C3H8–CO2 mixture at 3945 ± 20 kPa and 293.85 K, i.e., \(18.19 \times 10^{ - 10} {\text{m}}^{ 2} / {\text{s}}\), is found to be much higher than CO2 at 3950 ± 18 kPa and 293.85 K, i.e., \(8.68 \times 10^{ - 10} {\text{m}}^{ 2} / {\text{s}}\). In comparison with pure CO2, the presence of C3H8 in the C3H8–CO2 mixture contributes to a faster diffusion of CO2 from the gas phase into heavy oil and consequently a larger swelling factor of heavy oil.

Adsorption of CO2, CH4, C3H8, and H2O in SSZ-13, SAPO-34, and T-Type Zeolites

Single-component adsorption isotherms for CO2, CH4, C3H8, and H2O on SAPO-34, SSZ-13, and zeolite T were measured, and isosteric heats of adsorption were estimated. Long equilibration times were required for C3H8 adsorption in SAPO-34 and SSZ-13 because C3H8 diffuses slowly in these zeolites, but C3H8 isotherms were obtained quickly on zeolite T. Thus, when CO2 and C3H8 coadsorption loadings were measured by temperature-programmed desorption on SSZ-13, CO2 loadings were higher than C3H8 loadings at short times, whereas at long times, C3H8 loadings were higher as C3H8 displaced adsorbed CO2. In contrast, adsorption of CO2/C3H8 mixtures equilibrated quickly in zeolite T because of the fast C3H8 diffusion. These adsorption measurements may explain previously reported zeolite membrane behavior where C3H8 decreased CO2 permeances for SAPO-34, SSZ-13, and zeolite T membranes under most conditions, and steady state was only slowly obtained for SAPO-34 and SSZ-13 membranes in the presence of C3H8.

Equilibrium prediction of acid gas partial oxidation with presence of CH4 and CO2 for hydrogen production

Thermodynamic study of equilibrium condition for the partial oxidation of acid gas (AG consisted of 7.7%N2/61.7%H2S/20.1%CO2/9.3%H2O/1.2%CH4) was carried out using minimum Gibbs free energy strategy. The equilibrium calculation was fulfilled by Gibbs reactor model in the Aspen Plus software and sensitivity analysis about ER (Equivalent Ratio), addition ratio of CH4 and CO2 were conducted to investigate the favorable working condition for various parameters. Three cases that partial oxidation of the sole AG, AG/CH4 and AG/CH4/CO2 were studied. The results of the first case revealed that significant H2 and S2 yields and low SO2 selectivity were achieved at 1600K with ER of about 4 under pure oxygen application. Extra CH4 addition conducts a negative effect on equilibrium temperature for a fixed ER compared to the former case and acts as oxidation inhibitor for H2S while promising H2 yield is attainable at high ER. Excess CO2 can be converted to valuable CO at the expense of H2 yield via reverse water-gas shift reaction. Its oxidation medium characteristic also propels oxidation of H2S and S2 to improve SO2 selectivity at high temperature.

Experimental study on high-pressure rheology of water/crude oil emulsion in the presence of methane

ABSTRACTThe crude oil is in most cases accompanied with water and natural gas. For this reason, it is important to understand the rheology of the oil emulsion. There are already many works relating to rheology of the oil/water emulsion. However, studies on high-pressure rheology of water/crude oil emulsion in the presence of CH4 are rare. In this work, light crude oil with characteristics of high wax content, which is typical in Northwest China, was studied. The rheology of water/crude oil emulsion in the presence of CH4 under various conditions were fully studied. The results show that the crude oil emulsion showed obvious characteristics of non-Newtonian fluid at a lower temperature. Before water fraction reached a certain limit, the viscosity increases with the increase of water fraction, when water fraction reaches and exceeds the limit the emulsion viscosity drops with the increase of water fraction. The shear stress–shear rate curves become similar as the increase of temperature, indicating the decreasing effect of temperature on the relation between shear stress and shear rate. When the pressure reaches 8 MPa, the shear stress measured with CH4 in the system surpasses that measured without CH4. At higher pressure, CH4 shows obvious influence on the rheology.

Methane, Propene and Toluene Oxidation by Plasma-Pd/γ-Al2O3 Hybrid Reactor: Investigation of a Synergetic Effect

The combination of a sub-microsecond pulsed dielectric barrier discharge with Pd/gamma-Al2O3 catalyst was investigated for the oxidation of low concentration of methane, propene, and toluene in air at atmospheric pressure. The systematic comparison of the plasma-catalysis with the thermal-catalysis and the plasma-alone have been made for temperature window of 20–400 C and energy deposition in the range 23–148 J L-1. To emphasis the reactivity of plasma produced species on the activation of the catalyst, two reactor configurations were used [in-plasma catalysis (IPC), and post-plasma catalysis (PPC)]. Fourier transform infrared spectrometer was used to follow the VOCs conversion and to quantify the mineralized products. The plasma-catalyst combination leads to higher VOCs conversion and decreases the catalyst activation temperature in both IPC and PPC configurations. For hybrid system, the light-off temperature is always lower than those observed for catalytic oxidation. In addition, the formation of the by-products such as formaldehyde, formic acid, and ozone was reduced significantly. A significant synergetic effect of hybrid plasma-catalytic system is not really observed in the presence of CH4 and C3H6. However, for C7H8 oxidation the synergetic effect was demonstrated at low temperature (\150 C) for the IPC configuration.