Total Mole Fraction Research Articles

LIBS analysis of tritium in thin film-type samples

Evaluating the mole fraction of hydrogen isotopes in a solid is a difficult task. Few methods allow it to be achieved. LIBS is a laser method based on the electronic excitation of elements and the spontaneous emission of characteristic optical lines. On a sample containing hydrogen isotopes, α-type lines can allow the estimate of their total mole fraction. In addition, LIBS is a discriminating method because it can separate the contributions of isotopes. This paper reports the implementation of this method on thin film-type samples containing hydrogen and tritium.They consist of nanometric layers of palladium and titanium on a silicon substrate. Under irradiation of nanosecond laser pulses reaching a fluence of the order of 200 J cm−2, LIBS was performed in argon at atmospheric pressure. A detailed spectroscopic study is performed around the Tα line of wavelength 656.039 nm of the Balmer series (n=3→2) of tritium. An analysis based on the reconstruction of the spectrum under conditions of local thermodynamic equilibrium is carried out. This leads to the estimate of the tritium mole fraction.

Effect of ammonia addition on nanostructure of soot in laminar coflow diffusion flames of ethylene diluted with nitrogen

The effect of ammonia addition on the nanostructure of soot particles was studied experimentally for ethylene diffusion flames. To compensate the thermal effect and nitrogen-containing species production when ammonia was added, the total mole fraction of ammonia and nitrogen was fixed in the fuel stream. Soot particle size, fringe length, and fringe tortuosity were measured through transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). A complementary X-ray photoelectron spectroscopy (XPS) analysis provided information about the chemical bonding of soot. A significant delay in soot growth was observed and the particle size increased with the addition of ammonia. While there was no obvious correlation between the fractal dimension of soot and ammonia mole fraction (XNH3) or sampling location. With the addition of ammonia, the mean fringe length increased reasonably linearly with XNH3 and the fringe tortuosity increased up to XNH3 ≈ 0.17 and then decreased with XNH3, which suggested that ammonia addition led to higher graphitization and lower oxidative activity. The soot from ammonia diluted flame exhibited lower reactivity, implying the delay of soot surface growth. With the addition of ammonia, the value of sp2/sp3 (indication of the graphitization degree of soot particles) did not change much for XNH3 from 0 to 0.17 then increased significantly, which indicated the degree of graphitization of soot particles significantly increased with ammonia addition. The intensity of the N1s peak (indication of the N-containing species in soot) increased with the addition of ammonia. This study confirmed that the addition of NH3 promotes the graphitization of soot.

Analytical first-principles-based model for sprays-based CO2 capture

CO2 removal from flue gases or air is directly proportional to the overall contact area between the solvent and gas flow. Spraying the solvent offers possibilities for large area/volume ratios resulting from the small size of solvent droplets. The overall mass transfer (KGAv) is a crucial indicator of the performance of the system and indicates the overall CO2 capture rate per unit volume at given working pressure. The maximum capture rate of spray systems considered in this study is 608 kmol/m3-hr. This study develops an analytical model to predict mass transfer in spray-based systems for CO2 capture by evaluating KGAv and capture efficiency. Model predictions are validated using two experimental studies for a range of liquid flow rate, inlet solvent loading, different nozzle types, and inlet CO2 partial pressure. The relative importance of the incorporation of equilibrium partial pressure of CO2 (P*) into amine with respect to CO2 partial pressure is also studied. It is found that its effect on KGAv is prominent in high liquid flow rate and low solvent loading regimes where the overall CO2 capture is high. Finally, the variation of key parameters such as KGAv, total mass transfer coefficient (KG), effective area (Av), solvent loading (α), and mole fraction of CO2 in the gas stream (XCO2) along the channel height is studied, which gives insights on optimization of the channel height for specified operating conditions.

(Invited) Multi-Site, Multi-Reaction Model for the Simulating Intercalation and Alloy Electrodes

We overview enabling research for the characterization and design of cells using intercalation and alloy electrodes. Specifically, we have recently developed and implemented a multi-site, multi-reaction (MSMR) model. We shall demonstrate the approach with various chemistries of interest today, and the creation of reduced order models to simply calculations.We first discuss some of the similarities and differences between the MSMR model and the original Doyle-Fuller-Newman model [1, 2], which we shall refer to as the DFN model, first published in 1993. This model represents an intercalation electrode using porous electrode theory, but it also includes a detailed description of transport of Li ions in the electrolyte, transport of lithium in the solid phase, and the kinetics of the intercalation reaction as a Butler-Volmer equation. The MSMR model is based on the same porous electrode theory used in the original DFN model, and it uses the same treatment of transport in the electrolyte. However, the MSMR model introduces significant changes in the representation of both transport in the solid phase and the kinetics of the intercalation reaction. The main reason for the changes in the MSMR model is because it hypothesizes that intercalated lithium consists of not just one species, but multiple species. There is significant evidence to support this point of view, both from cyclic voltammetry experiments as well as X-ray diffraction analyses [4].The DFN model, as originally described and often used today, represents solid phase diffusion as a linear equation with a constant diffusion coefficient. This representation is known to be highly inaccurate, for example, in the case of graphite, where measurements have shown that the diffusion coefficient can vary by several orders of magnitude depending on the mole fraction of intercalated lithium [3,4]. More sophisticated treatments of solid phase diffusion use the chemical potential as the driving force for diffusion and because the chemical potential can be written in terms of the OCV, this explains how the Open Circuit Voltage now plays a role in the diffusion equation. Since the MSMR model uses multiple species, the solid phase diffusion problem should also involve multiple species, but the entire system of multi-species diffusion equations simplifies to a single equation, if one assumes that the various species of lithium are locally equilibrated with each other within the active material particles. The details of this analysis are given in [6].The DFN model uses a Butler-Volmer equation to represent the kinetics of the intercalation reaction, whereas the MSMR model uses a Butler-Volmer equation for each species; the intercalation reaction rate thus becomes the sum of these multiple Butler-Volmer equations, which are formulated using activities instead of concentrations, as is done in the original DFN model.Finally, the MSMR model proposes a simple empirical relationship, based on a generalized Nernst equation, to describe the relationship between the mole fraction of each intercalated species and the OCV. This formulation provides a systematic way to derive analytical formulas to represent the OCV relationship x(U), where x is the total mole fraction of intercalated species and U is the corresponding OCV. Several examples [5,6] show that this formalism suffices to provide accurate fits of x(U) to experimental data for many different electrode materials in common use, and it also provides analytical expressions for the derivative dx/dU, which shows up in the expressions for the solid phase diffusion equation.In summary, the MSMR model attempts to give a more accurate representation of solid phase diffusion and a more complete representation of intercalation interfacial kinetics, and, in this context, our hope is that the MSMR model provides a useful complement to the original DFN model. M. Doyle, T. F. Fuller, and J. Newman, J. Electrochem. Soc., 140(1993)1526.T. F. Fuller, M. Doyle, and J. Newman, J. Electrochem. Soc., 141(1994)1.D. Levi, E. A. Levi, and D. Aurbach, Journal of Electroanalytical Chemistry, 421, 89 (1997).D. R. Baker and M.W. Verbrugge, J. Electrochem. Soc., 159 (8) A1341-A1350 (2012).M. W. Verbrugge, D. R. Baker, and X. Xiao, J. Electrochem. Soc., 163(2016)A262-A271.M. W. Verbrugge, D. R. Baker, B. J. Koch, X. Xiao, and W. Gu, J. Electrochem. Soc., 164(2017)E3243-E3253.D. R. Baker, M. W. Verbrugge and W. Gu, J. Electrochem. Soc., 166 (4) A521-A531 (2019).

Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts

The energy potential of pig manure (PM) has garnered attention. Supercritical water gasification (SCWG) is proposed to convert PM to H2-enriched syngas without the drying process for wet materials. This paper studied the effect of diverse parameters on H2-enriched syngas production. The results revealed that higher temperatures and alkaline catalysts elevated total gas yield and H2 yield, with the addition of K2CO3 at 620 °C, 30 min, and 6 wt% feed concentration generating the highest total gas yield (36.55 mol/kg), H2 yield (18.89 mol/kg), and mole fraction (51.55%), accompanied by a high gasification efficiency (87.59%). Based on product characterization and thermodynamic analysis, reaction mechanisms were proposed to provide insight into enhancing syngas production, indicating that the suppression of polymerization reactions between cyclic compounds and the promotion of CH4, C2H6, and long-chain alkanes conversion were essential. Further, the environmental impact evaluation showed that heavy metals (Cu, Cr, As, and Zn) were concentrated in solid products by adsorption and passivation. The solid products exhibited negligible environmental hazards. This work showed that PM SCWG realized syngas production as well as heavy metals enrichment and stabilization, which could provide an alternative solution to the clean conversion of other types of organic wastes, especially with high heavy metals content, such as oily sludge and sewage sludge.

Atmospheric biogenic volatile organic compounds in the Alaskan Arctic tundra: constraints from measurements at Toolik Field Station.

The Arctic is a climatically sensitive region that has experienced warming at almost 3 times the global average rate in recent decades, leading to an increase in Arctic greenness and a greater abundance of plants that emit biogenic volatile organic compounds (BVOCs). These changes in atmospheric emissions are expected to significantly modify the overall oxidative chemistry of the region and lead to changes in VOC composition and abundance, with implications for atmospheric processes. Nonetheless, observations needed to constrain our current understanding of these issues in this critical environment are sparse. This work presents novel atmospheric in situ proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) measurements of VOCs at Toolik Field Station (TFS; 68°38' N, 149°36' W), in the Alaskan Arctic tundra during May-June 2019. We employ a custom nested grid version of the GEOS-Chem chemical transport model (CTM), driven with MEGANv2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) biogenic emissions for Alaska at 0.25° × 0.3125° resolution, to interpret the observations in terms of their constraints on BVOC emissions, total reactive organic carbon (ROC) composition, and calculated OH reactivity (OHr) in this environment. We find total ambient mole fraction of 78 identified VOCs to be 6.3 ± 0.4 ppbv (10.8 ± 0.5 ppbC), with overwhelming (> 80 %) contributions are from short-chain oxygenated VOCs (OVOCs) including methanol, acetone and formaldehyde. Isoprene was the most abundant terpene identified. GEOS-Chem captures the observed isoprene (and its oxidation products), acetone and acetaldehyde abundances within the combined model and observation uncertainties (±25 %), but underestimates other OVOCs including methanol, formaldehyde, formic acid and acetic acid by a factor of 3 to 12. The negative model bias for methanol is attributed to underestimated biogenic methanol emissions for the Alaskan tundra in MEGANv2.1. Observed formaldehyde mole fractions increase exponentially with air temperature, likely reflecting its biogenic precursors and pointing to a systematic model underprediction of its secondary production. The median campaign-calculated OHr from VOCs measured at TFS was 0.7 s-1, roughly 5 % of the values typically reported in lower-latitude forested ecosystems. Ten species account for over 80 % of the calculated VOC OHr, with formaldehyde, isoprene and acetaldehyde together accounting for nearly half of the total. Simulated OHr based on median-modeled VOCs included in GEOS-Chem averages 0.5 s-1 and is dominated by isoprene (30 %) and monoterpenes (17 %). The data presented here serve as a critical evaluation of our knowledge of BVOCs and ROC budgets in high-latitude environments and represent a foundation for investigating and interpreting future warming-driven changes in VOC emissions in the Alaskan Arctic tundra.

Quantification of n-heptane low temperature oxidation products by proton-transfer-reaction mass spectrometry

While studies on the low temperature oxidation of organic compounds have been in depth, fast and accurate quantitative analysis of oxidation products, especially for those without standard samples, remains challenging and requires analytical developments. This work studied n-heptane low temperature oxidation in a jet-stirred reactor (JSR) using proton-transfer-reaction mass spectrometry (PTR-MS). The oxidation products were also analyzed by a synchrotron vacuum ultraviolet radiation photoionization mass spectrometer (SVUV-PIMS) for comparison. The results showed that PTR-MS was able to measure most oxygenated intermediates compared to SVUV-PIMS. Furthermore, the method for the quantification of low temperature oxidation products was studied. By employing a series of calibration gases, the sensitivities of PTR-MS were confirmed to be linearly related to proton-transfer reaction rates, which were calculated using the trajectory parameterization theory. Mole fraction profiles of oxidation products measured by PTR-MS were compared to SVUV-PIMS and literature gas chromatography data, and in most cases, the results showed good consistency. Special attention is needed for some molecules, such as carboxylic acids, formaldehyde, and peroxides. The effect of the humidity of the reaction environment and the fragment on the quantification need to be considered. Overall, PTR-MS is a promising instrument for the quantitative analysis of combustion products and has the potential to measure the total mole fraction of complex isomers (could not distinguish isomers) and to predict the mole fraction of products without a standard sample.

Extent of raft composition in a model plasma membrane

“Rafts” are nanometer-size inhomogeneities in the plasma membrane that, in the outer leaflet, are enriched in sphingomyelin and cholesterol. They are thought to provide a platform for proteins to carry out biological processes. Here, we employ a model asymmetric plasma membrane to address the question of the range of sphingomyelin and cholesterol compositions in which one would expect the formation of rafts. We define a weight for the likelihood of raft formation and evaluate it as a function of the sphingomyelin mole fraction in the outer leaflet for three bilayers with total cholesterol mole fractions of 0.30, 0.40, and 0.50. Not surprisingly, the weight decreases when there is little sphingomyelin. Less expected, we find that the weight also decreases when there is a large mole fraction of sphingomyelin. The weight is largest in the bilayer with a total cholesterol mole fraction of 0.30 and decreases rapidly with increasing total cholesterol. We explicate the reasons for these behaviors. In the 0.30 cholesterol bilayer, the largest weight occurs at a sphingomyelin mole fraction in the outer leaflet of approximately 0.23. The weight falls to one half its maximum value at sphingomyelin mole fractions of 0.15 and 0.33. In terms of the sphingomyelin mole fraction of the asymmetric bilayer, the maximum weight occurs at 0.12 and falls to half maximum at 0.08 and 0.17.

Interannual variability in the Australian carbon cycle over 2015–2019, based on assimilation of Orbiting Carbon Observatory-2 (OCO-2) satellite data

Abstract. In this study, we employ a regional inverse modelling approach to estimate monthly carbon fluxes over the Australian continent for 2015–2019 using the assimilation of the total column-averaged mole fractions of carbon dioxide from the Orbiting Carbon Observatory-2 (OCO-2, version 9) satellite. Subsequently, we study the carbon cycle variations and relate their fluctuations to anomalies in vegetation productivity and climate drivers. Our 5-year regional carbon flux inversion suggests that Australia was a carbon sink averaging −0.46 ± 0.08 PgC yr−1 (excluding fossil fuel emissions), largely influenced by a strong carbon uptake (−1.04 PgC yr−1) recorded in 2016. Australia's semi-arid ecosystems, such as sparsely vegetated regions (in central Australia) and savanna (in northern Australia), were the main contributors to the carbon uptake in 2016. These regions showed relatively high vegetation productivity, high rainfall, and low temperature in 2016. In contrast to the large carbon sink found in 2016, the large carbon outgassing recorded in 2019 coincides with an unprecedented rainfall deficit and higher-than-average temperatures across Australia. Comparison of the posterior column-averaged CO2 concentration with Total Carbon Column Observing Network (TCCON) stations and in situ measurements offers limited insight into the fluxes assimilated with OCO-2. However, the lack of these monitoring stations across Australia, mainly over ecosystems such as savanna and areas with sparse vegetation, impedes us from providing strong conclusions. To a certain extent, we found that the flux anomalies across Australia are consistent with the ensemble means of the OCO-2 Model Intercomparison Project (OCO-2 MIP) and FLUXCOM (2015–2018), which estimate an anomalous carbon sink for Australia in 2016 of −1.09 and −0.42 PgC yr−1 respectively. More accurate estimates of OCO-2 retrievals, with the addition of ocean glint data into our system, and a better understanding of the error in the atmospheric transport modelling will yield further insights into the difference in the magnitude of our carbon flux estimates.

Effect of boundary conditions and n-heptane on methyl decanoate HCCI combustion and emission based on two-stroke diesel engine

The initial boundary conditions, combustion, and emission characteristics of methyl decanoate (MD) mixed with different proportions of n-heptane (N-Hep) for homogeneous charge compression ignition (HCCI) are studied in this work. MAN B&W 6S70MC two-stroke diesel engine was used as the engine model of the reactor. The results showed that, when the equivalence ratio is 0.48, the NO emissions in the MD and N-Hep HCCI combustion process decrease with the decrease of the initial temperature. The initial temperature is determined to be 380 K. At the same time, NO emissions decrease with the increase of initial pressure, and the initial pressure is determined to be 1.3 atm. The results also indicate that, at a certain initial temperature, the initial pressure and total mole fraction of fuel, CO2, NOx reaction rates, and emissions are reduced significantly with the increase of N-Hep percentage in MD and N-Hep mixing combustion.

Effect of Combustion Boundary Conditions and n-Butanol on Surrogate Diesel Fuel HCCI Combustion and Emission Based on Two-Stroke Diesel Engine

The combustion and emission characteristics of surrogate diesel fuel homogeneous charge compression ignition (HCCI) with different combustion boundary conditions and n-butanol (NB) mixing ratios are studied in this work. Engine data of a two-stroke low-speed direct-injection marine diesel engine were selected for the reactor. HCCI combustion was achieved by compressing a completely homogeneous mixture of fuel and air. The results show that NO emissions decrease slightly with the increase of initial boundary pressure at a constant equivalence ratio and initial temperature. In addition, the different initial boundary temperature has little effect on NO emission. The results also indicate that the ignition delay time of the mixed fuel rises with the increase of n-butanol mixing ratio. The emissions and reaction rate of NOx reduce significantly with the increase of n-butanol percentage in surrogate diesel fuel and n-butanol mixing combustion at a constant equivalence ratio and total mole fraction. Meanwhile, CO2 emissions also decrease significantly with the increase of n-butanol mixing ratio.

Optimisation of syngas production from a novel two-step chemical looping reforming process using Fe-dolomite as oxygen carriers

The production of syngas from hydrogen carbon feedstocks such as natural gas and biomass is of high importance to the chemical industry. In conventional chemical looping steam reforming(CLSR), the composition of the syngas produced is limited by the chemical equilibrium of the water-gas-shift reaction. In this study, we demonstrate that a two-step chemical looping reforming (TS-CLR) process is capable of alleviating the equilibrium limit to produce syngas of higher CO and H2 contents. For example, the total mole fraction of H2 and CO in the syngas produced from the conventional CLSR of toluene at 900 °C is limited to below 89.4 vol% (dry basis), whereas TS-CLR could produce syngas with >94 vol% of CO and H2 under the same condintions. The TS-CLR process is best carried out in a bed of Fe-dolomite oxygen carriers with a Ca:Fe ratio of 1:1 (denoted as C1F1). Compared to the pure Ca2Fe2O5 and Fe2O3/Al2O3 oxygen carriers, the C1F1 affords improvements in syngas yield, carbon conversion and syngas purity. The superior performance of C1F1 is attributed to the promotion of the lattice oxygen activities of Ca2Fe2O5 by MgO, as well as its excellent phase reversibility over redox cycles.

Effects of blending 2,5-dimethylfuran and dimethyl ether to toluene primary reference fuels: A chemical kinetic study

In the present work, renewable oxygenates 2,5-dimethylfuran (DMF) and dimethyl ether (DME) are considered as alternatives to fossil fuels for gasoline engines. The effects of blending DMF and DME on the combustion of gasoline surrogate are numerically studied. The gasoline surrogate is toluene primary reference fuel (TPRF) mixtures containing iso-octane, n-heptane, and toluene. Two skeletal mechanisms are proposed for the analysis: mechanism A with 504 species and 4212 reactions and mechanism B with 153 species and 740 reactions. These mechanisms are validated against a wide range of experimental data on ignition delay times and 1-D flames. The main findings of the present work are: 1) The ignition inhibiting effect of DMF dominates over the promoting effect of DME at 750 K and 25 bar when the total mole fraction of DMF and DME is less than 20 %. On the contrary, DME augments ignition with greater strength than the inhibition effect of DMF at 825 K and 25 bar. These observations are made for equimolar mixture of DMF and DME blended with TPRF in varying proportions. 2) The laminar burning velocity change stays within 10% of TPRF-air values for 50% TPRF/25%DMF/25%DME-air mixture for 0.6 ≤ φ ≤ 1. 6. 3) DME mitigates additional soot emission caused by DMF blending with TPRF. 4) For the first time in literature, it is shown that the laminar burning velocity and the maximum slope of OḢ mole fraction in the stoichiometric flames vary linearly with the research octane number (RON) for TPRF-air mixtures.

Improvement in the transience and mechanical performance of flexible Poly(phthalaldehyde) substrates

Cyclic poly(phthalaldehyde) (PPHA) is a metastable polymer that depolymerizes to ortho-phthalaldehyde (o-PHA) at ambient temperatures. Both high molecular weights and a long shelf-life can be achieved. After an external stimulus trigger has been activated to break polymer backbone bonds, PPHA undergoes rapid depolymerization from the solid state. Flexible PPHA substrates can be made by mixing the polymer with traditional non-volatile plasticizers, however the solubility of plasticizers in PPHA is sometimes poor, and any solid products left behind after depolymerization can hinder the transience of the mixture. Hansen solubility parameters for PPHA were obtained and used to predict the solubility of plasticizers in PPHA. The freezing point of the degraded remnants is proportional to the total mole fraction of additives present in any given PPHA formulation. The colligative properties of o-PHA were obtained and used to estimate the freezing point depression of the transient remnants for multi-component mixtures. A single additive approach to plasticizing PPHA is presented in this study using diethyl adipate (DEA). Mechanical properties of PPHA films containing DEA were characterized. Glass transition temperature (Tg) values between 99.5 °C and 12.5 °C can be achieved using THF solvent to cast the PPHA-DEA film. A Tg of 187 °C was extrapolated for pure PPHA with no residual solvent. The flexibility of the DEA loaded PPHA films greatly improved at high DEA loadings. DEA also improved the transient depolymerization performance of DEA loaded PPHA resulting in complete liquification after depolymerization.

Effect of Engine Speeds and Dimethyl Ether on Methyl Decanoate HCCI Combustion and Emission Characteristics Based on Low-Speed Two-Stroke Diesel Engine

Abstract The combustion and emission characteristics of homogeneous charge compression ignition (HCCI) fuelled by methyl decanoate (MD) with different engine speeds and dimethyl ether (DME) mixing ratios are investigated in this work. Engine data of a MAN B&W 6S70MC low-speed two-stroke marine diesel engine were used for the reactor. The results show that a decrease of engine speed has little effect on the in-cylinder temperature and pressure of the engine at constant excess air coefficient of 1.5. Meanwhile, NOx emissions decrease with a decrease of engine speed in pure MD HCCI combustion. The results also indicate that NOx and CO2 emissions decrease significantly with an increase in the percentage of DME in MD and DME mixing combustion at a constant total mole fraction and engine speed of 85 revolutions per minute (r/min).

Nonprimitive Model Electrolyte Solutions: Comprehensive Data from Monte Carlo Simulations

We report molecular simulation data for the Helmholtz energy, the internal energy, and the constant-volume heat capacity of nonprimitive model electrolyte solutions, that is, mixtures of charged and nonpolarizable dipolar hard spheres. We consider model electrolyte solutions where positively and negatively charged particles and the dipolar solvent particles all have the same hard-sphere diameter. For a range of dimensionless density, 0.05 ≤ ρ* ≤ 1.0, we consider fluids with dimensionless dipole moments up to μ*2 ≤ 4. The dimensionless charge has a range of 25 ≤ q*2 ≤ 150, and the total mole fraction of ions covers a range of 0.002 ≤ x ≤ 0.12.

Probing hydraulically-fractured wells in unconventional shale reservoirs under cyclic CO2 injection: Variation of thermophysical properties

Despite the recent growth in oil production from unconventional reservoirs, existing hydraulically-fractured horizontal wells face challenges of poor recovery with the rapid production decline over a short life span. Enhanced recovery techniques, such as cyclic CO2 injection can be a solution to this impending problem and lead to energy independence for the foreseeable future. However, mechanisms occurring around the hydraulically fractured wells are far from fully understood. The primary motivation of this study revolves around addressing this limitation. Specifically, we explored the evolution of various thermophysical properties occurring around hydraulically-fractured wells in liquid-rich unconventional reservoirs using a holistic, integrated modeling framework.Available well-logs and other data from Howard County in the Midland Basin formed the basis for constructing representative 3D structural models that capture the Midland Basin stratigraphy. We used a simulator to create multistage hydraulic fractures that allowed integration into numerical reservoir-flow simulation models. Then, both convective and diffusive flow within a multicomponent compositional simulation modeling paradigm is used to examine the role of molecular diffusion in performance under cyclic CO2 injections in hydraulically-fractured well.The simulation results indicate that molecular diffusion yields an incremental oil recovery of 6% compared to models that do not. Our analysis reveals different thermophysical properties transition from near wellbore regions to outer regions into the rock matrix. Changes in total mole fractions of CO2, methane, and hydrocarbons with C7+ fraction, pressure and saturation variation, viscosity reduction and the surface tension over 14 injection-soaking-production cycles are tracked. The analyses of the evolution of these thermophysical properties provide us with means to evaluate the efficiency of the solvent injection process. The simulation results explain how, when, and where CO2 disperses into the reservoir.

Calorimetric and structural studies of organic compound of tris(pentafluorophenyl)-4-pyridylethylgermane

In the present research, the temperature dependence of heat capacity of tris(pentafluorophenyl)-4-pyridylethylgermane (C6F5)3Ge–CH2–CH2–C5H4N was studied by precise adiabatic vacuum calorimetry and differential scanning calorimetry over the temperature range from 6 to 450 K. The temperature and enthalpy of fusion of tris(pentafluorophenyl)-4-pyridylethylgermane and the total mole fraction of impurities have been determined. The thermal stability of the sample was investigated by thermogravimetric analysis. The experimental data were used to calculate the standard thermodynamic functions: heat capacity, enthalpy, entropy, and the Gibbs energy over the range from T → 0 to 420 K for crystalline and liquid states. For the compound under study, the standard entropy of formation in the crystalline state was calculated at T = 298.15 K. In addition, the structure of the investigated compound was established, and corresponding structural parameters were determined.

Hydrogen production by gasification of Kenaf under subcritical liquid‒vapor phase conditions

In this study, Kenaf biomass was gasified under subcritical liquid-vapor conditions and effect of initial water amount on gas composition and hydrogen production was evaluated at different temperatures. Gasification was carried out in a batch type reactor, with various initial water volumes (0, 12, 25, 50, 75 mL), at different temperatures (250, 275, 300, 325 °C) and with different catalysts (Ru/C, Pt/C, Na2CO3, Fe2O3, CaO, CaCO3 and RuCl3). The results revealed that the gasification efficiency and hydrogen selectivity are dramatically varied with initial water percentage that was fed to the reactor. The gaseous products obtained from hydrothermal gasification of kenaf were mainly H2, CO2, and in lower but varying amounts, CH4 and C2H4. Water soluble RuCl3 was found to be more effective than water insoluble Ru/C catalyst on biomass gasification. RuCl3 catalyst has a high catalytic activity for kenaf gasification with greater H2 selectivity. Maximum total gas (462.5 mL) and H2 mole fraction in the gaseous product (44.5%) were obtained at 250 °C with RuCl3 catalyst. The maximum carbon conversion (%) was also obtained with RuCl3 as 71.3%. Water behaves as both the reaction medium and the second main reactant beside biomass, during the subcritical liquid-vapor phase gasification process.

An Approach to Estimate Atmospheric Greenhouse Gas Total Columns Mole Fraction from Partial Column Sampling

This study presents a new conceptual approach to estimate total column mole fractions of CO2 and CH4 using partial column data. It provides a link between airborne in situ and remote sensing observations of greenhouse gases. The method relies on in situ observations, external ancillary sources of information (e.g., atmospheric transport models), and a regression kriging framework. We evaluate our new approach using National Oceanic and Atmospheric Administration’s (NOAA’s) AirCore program—in situ vertical profiles of CO2 and CH4 collected from weather balloons. Our paper shows that under the specific conditions of this study and assumption of unbiasedness, airborne observations up to 6500–9500 m altitude are required to achieve comparable total column CO2 mole fraction uncertainty as the Total Carbon Column Observing Network (TCCON) network provides, given as a precision of the ratio between observed and true total column-integrated mole fraction, assuming 400 ppm XCO2 (2σ, e.g., 0.8 ppm). If properly calibrated, our approach could be applied to vertical profiles of CO2 collected from aircraft using a few flask samples, while retaining similar uncertainty level. Our total column CH4 estimates, by contrast, are less accurate than TCCON’s. Aircrafts are not as spatially constrained as TCCON ground stations, so our approach adds value to aircraft-based vertical profiles for evaluating remote sensing platforms.