Binary Gas Research Articles

Experimental study of the formation and decomposition of mixed gas hydrates in water-hydrocarbon system

The phase transition of gas hydrate with two or more guests is associated with gas recovery, storage and separation. In this work, the formation and decomposition of binary and ternary gas hydrates containing CH4, C2H6 and C3H8 were investigated experimentally in high-pressure reactors equipped with visual windows. The gas compositions during mixed hydrates formation and decomposition were analyzed to track the occupation of guests in hydrate structures and the release of guests from hydrate cages. It was found that of CH4 was adsorbed in the hydrate cages constructed by C2H6 and C3H8 in the initial stage. In the depressurized decomposition of CH4-C3H8 hydrates and CH4-C2H6-C3H8 hydrates slurry, CH4 and C2H6 molecules were preferentially released from hydrate structures while more C3H8 molecules were able to stay in hydrate phase, which was in accordance with the order of the diameter ratio of guest molecule to hydrate cage. The preservation of CH4-C3H8 hydrates and CH4-C2H6-C3H8 hydrates above 0 ℃ was observed under a low pressure. It was proposed that the reconstitution or reformation of hydrate layer rich of C3H8 may encrust the remaining hydrate particles, preventing hydrate from further quick decomposition. In-situ Raman spectra confirmed the enrichment of C3H8 molecules at the surface of CH4-C3H8 hydrates, which revealed that the metastable hydrate layer rich of C3H8 molecules may act as mass transfer resistance of gas release from hydrate decomposition. Differently, the decompositions of CH4-C2H6 hydrates and C2H6-C3H8 hydrates were uniform as different guests were produced concurrently without preservation. The new insights into mixed hydrates decomposition in this work may provide a new basis for mixed gas production from gas hydrate, and gas storage and separation with hydrate.

Molecular simulation of adsorption behaviors of methane and carbon dioxide on typical clay minerals

Knowledge of the interaction mechanisms between shale and CH4/CO2 is crucial for the implementation of CO2 sequestration with enhanced CH4 recovery (CS-EGR) in shale reservoir. As one of the main constituents of shale, clay minerals can profoundly affect the storage capacity of gases in nanopores. In this paper, the adsorption behaviors of both CO2 and CH4 on montmorillonite, illite as well as kaolinite under dry condition are investigated by Grand Canonical Monte Carlo (GCMC) simulation. The results exhibit that the maximum adsorption capacity of single-component CH4 and CO2 is associated with the types of clay crystals. Specifically, the montmorillonite has the strongest adsorption capacity for CO2, followed by illite and kaolinite, while the sequence in maximum adsorption capacity of CH4 is predicted in the order of kaolinite > montmorillonite > illite. These discrepancies are closely related to the characteristics of adsorbate molecules as well as the different structures of clay crystals. Meanwhile, the maximum adsorption capacity of CH4 in studied clay minerals gradually decreases as pore size increases, while nanopores with 2-nm basal spacing demonstrate the highest adsorption capacity for CO2. In addition, it is observed that the studied clay minerals tend to preferentially adsorb CO2 rather than CH4 during binary gas mixtures simulation. The selectivity of CH4/CO2 mixtures in montmorillonite and kaolinite exhibits various performances as the adsorption pressure increases, with the selectivity in montmorillonite being the largest, especially at low pressure. The cation exchange significantly enhances the electrostatic interaction with CO2 molecules, leading to a higher loading of CO2 as well as larger value of selectivity. These findings can provide basis and guidance for the CS-EGR project in shale reservoirs.

Molecular Simulations of the Gas Diffusion through the Two-Dimensional Graphyne Membrane

Owing to the unified and tunable pore size, two-dimensional graphyne membranes show excellent performance in the realm of gas transport and separations. The impacts of environmental conditions on the pore size of a porous membrane are ignored in previous studies. Using molecular modeling techniques, we here probe the accessible pore size of the γ-graphyne membrane under various pressure and temperature conditions. First, by assessing the gas permeation through the two-dimensional γ-graphyne membrane at a constant temperature, the accessible pore size of this membrane is shown to be proportional to the driving force—the pressure difference between the two sides of the porous membrane. Such a driving force dependence is found to be well described by a simple asymptotic model. Then, by determining such pressure dependence at two different temperatures, temperature is found to show a weak influence on the accessible pore size. Finally, by considering the binary mixed gases of various mole fractions, the accessible pore size measured using one of the two species is shown to be dependent on its partial pressure difference. These findings for the accessible pore size, which highlight the tunable pore size by altering the driving force, can be expected to provide a practical strategy to rationalize/refine the pore size of the porous membrane for gas transport and separations, especially for two molecules with similar diameters.

High-Pressure Gravimetric Measurements for Binary Gas Adsorption Equilibria and Comparisons with Ideal Adsorbed Solution Theory (IAST).

Measurements of gas mixture adsorption equilibria at high pressures are important for assessing actual adsorbent selectivities but are often out of reach, given the challenging nature of the required experiments. Here, we report a high-pressure gravimetric binary gas adsorption equilibrium measurement system based on simultaneous gas density and mixture adsorption measurements in a single gas cell coupled to a magnetic-suspension balance. Compared to traditional techniques which rely on analytical measurements of gas composition, this approach does not require any sampling. Adsorption measurements of two gas mixtures (0.500 N2 + 0.500 CH4 and 0.400 N2 + 0.600 CO2, mole fraction) on a commercially available molecular sieve (NaY, sodium molecular sieve type Y) were carried out in the temperature range 282 to 325 K with a pressure up to 10 MPa. A prediction method for the gas mixture adsorption equilibria in a closed system using the ideal adsorbed solution theory (IAST) model was used to compare the experimental results. For binary mixtures of components with similar adsorption capacities (here N2 and CH4), the system can measure the adsorption equilibria at pressures higher than 1.0 MPa and the result agrees well with the IAST model prediction. For two gases with very different adsorption capacities, the uncertainty in the adsorption equilibrium measurement is much larger. The dominant uncertainty source is the gas density measurement, whose uncertainty could potentially be cut to half if the current titanium sinker is replaced with a sinker made of single-crystal silicon and with a larger volume.

Competitive adsorption law of multi-component gases during CO2 displacement of CH4 in coal seams

The CO2 enhanced coal bed methane recovery technology provides an excellent way to mitigate the greenhouse effect and energy crisis. The features and mechanism of CO2/CH4 competitive adsorption in the coal rock matrix have a critical impact on the production of CBM. For CO2/CH4 competitive adsorption process components and pressure changes, a multi-component gases competitive adsorption experiment was carried out with CO2 and CH4 binary gases as the study objects, and a multi-component adsorption model was developed by the expanded Langmuir equation. Based on the principles of molecular dynamics and thermodynamics, important parameters such as the average free range of gas molecules and adsorption potential are introduced to explain the competitive adsorption behavior from multiple perspectives and explore the competitive adsorption law of CH4 and CO2 under multiple component conditions, so as to provide some theoretical basis and field guidance for improving the extraction effect of CH4 in coal seams. The results show that: Under two critical conditions (100%CO2 +0%CH4 and 0%CO2 +100%CH4), the Langmuir volumes of CO2 for HN 1/3 coking coal and HL weakly caking coal respectively are 2.21 and 3.01 times higher than those of CH4; the overall adsorption capacity of binary gas is in between the adsorption capacities of both critical conditions and increases with increasing CO2 concentration in the gas source ratio; using E-L equation for binary gas component partitioning, the CH4 partition curves were all below CO2, the concentration of free-phase CH4 was always higher than that in the adsorbed phase, and coal samples had stronger adsorption ability for CO2 than CH4. CO2 has a stronger adsorption potential at the surface for HL weakly caking coal. CH4 has a slightly stronger adsorption potential at the surface for HN 1/3 coking coal. The higher coalification degree of the coal sample, the stronger the adsorption ability for CH4 and the weaker the adsorption ability for CO2. The slope of the overall adsorption curve of multi-component gases is analogous to the slope of the component with a high ratio of gas or strong adsorption capacity; the capacity of one-component adsorption for dual gas is closely related to the partial pressure of the free-phase gas and the separation factor α21. When the concentration ratio of CH4/CO2 in free phase is y2/y1 =α21, the concentration of both gases in adsorption phase is 50%, and α21 correlation is weakened, then the free phase gas partial pressure is dominant and there is a threshold value makes CH4 and CO2 adsorption capacity equal; when y2/y1 <α21, the coal preferentially adsorbs CO2 in the binary gas; when y2/y1 >α21, the coal preferentially adsorbs CH4 in the binary gas.

Characterization of a Nickel / Gadolinia Doped Ceria Fuel Electrode for Co-Electrolysis

Modelling of the high temperature co-electrolysis process requires understanding of the underlying reaction pathways. These include the electrochemical steam reduction, the electrochemical CO2 reduction and their coupling via the catalytic (reverse-)water-gas-shift reaction (RWGS). The assumption of a very fast water-gas-shift reaction and therefore neglectable CO electro-oxidation is widely used. The validity of this assumption has been previously investigated and proven to be sufficient by Kromp et al. [1] for an anode supported cell (ASC) with a nickel / yttria-stabilized zirconia (Ni/YSZ) fuel electrode.Within this contribution we aim to extend the approach by Kromp et al. [1] towards an electrolyte-supported cell (ESC) with a nickel / gadolinium-doped ceria (Ni/CGO) fuel electrode. Previously, it has been proposed, that the electro-oxidation /-reduction of CO / CO2 can be present under reformate gas mixtures [2,3] on Ni/CGO fuel electrodes. However, a detailed comparison of pure activation resistance contributions during different operating modes has not been performed yet.We present results from a complex variation of operating parameters (such as various gas compositions, exemplarily shown in fig. 1) for process identification by the use of electrochemical impedance spectroscopy and the subsequent impedance analysis by the distribution of relaxation times (DRT). Visualization and deconvolution of gas diffusion impedance contributions is done via the evaluation of the polarization resistance differences with different inert gases. This has been successfully applied for binary gas mixtures of hydrogen and steam [4] and also CO2 and CO. [5] The applicability of this method towards more complex multicomponent gas mixtures incorporating hydrogen, steam, CO2 and CO will be shown. By subtracting the gas diffusion impedance contributions, it is possible to evaluate reaction kinetics of the underlying activation polarization and a meaningful comparison of operation modes is facilitated. The ratio of direct CO2electro-reduction and CO2-conversion by RWGS will be discussed for different compositions and temperatures to show a non-neglectable influence of the CO2 electroreduction at even lower pCO2 / pH2 ratios than previously reported. Furthermore, we compare our results with ones obtained from Ni/YSZ fuel electrodes, to investigate the influence of fuel electrode structure and material.

Mass Transfer Theory Based Analysis of Influencing Factors on Component Gradient of Near-surface Atmosphere on Venus

The atmosphere of Venus differs completely from that of Earth despite the planets’ similarity in size and mass. At Venus's surface, the atmosphere is hot and dense, with a temperature of approximately 735 K and a pressure of approximately 92 bar. The temperature profile from the Soviet VeGa-2 probe shows high instability of the near-ground potential temperature, which, according to relevant research, can be explained by the vertical gradient of N2 mole fraction. Based on the Maxwell–Stefan mass transfer theory, we propose a theoretical model of binary gas component for a quantitative discussion of influencing factors for the N2 vertical concentration gradient, which consist of temperature, gravity, specific heat ratio, mass relative factor, thermal diffusion factor, and CO2 flux. Our model shows that the 0%–3.5% N2 concentration gradient cannot be generated without CO2 flux in the near-ground atmosphere of Venus. And the result with CO2 source indicates that the 0.000001%–3.5% N2 concentration gradient at 0–7 km atmosphere can be generated by the 2.7 × 10−6 mol m−2 s−6 CO2 flux on Venusian surface, which is in agreement of gradient reckoned by VeGa-2's data. This magnitude of CO2 flux is close to the one produced by volcanic eruptions on Earth, indicating possible existence of volcanic activities on the surface of Venus. This work has provided the community a new vision to understand the influencing factors of Venusian atmospheres composition distribution.

Influence of bed material on biomass gasification in fluidized beds via a TFM-DEM hybrid model

In the biomass gasification process, mixing and segregation behaviors of fuel particles and bed materials greatly influence the performance. In this work, the Two-Fluid Model-Discrete Element Method (TFM-DEM) hybrid model is employed to evaluate the impact of bed material on biomass gasification in a fluidized bed reactor, where fuel particles and bed material particles are described by the Lagrangian method and Eulerian method respectively. The biomass particle size distribution is taken into consideration. The kinetic theory of rough sphere (KTRS) is employed to consider the rotation impact of bed materials. Flow behaviors of binary mixture and gas composition distribution are analyzed. The results reveal that the bed materials with greater size can hinder the particle mixing behaviors and make the biomass particles concentrate on the bed surface so as to increase the non-uniformity of temperature distribution in the bed. A good fluidization with smaller bed material particles is beneficial to hydrogen production.

The Condensation Characteristics of Propane in Binary and Ternary Mixtures on a Vertical Plate

Natural gas is one of the most common forms of energy in our daily life, and it is composed of multicomponent hydrocarbon gas mixtures (mainly of methane, ethane and propane). It is of great significant to reveal the condensation mechanism of multicomponent mixtures for the development and utilization of natural gas. A numerical model was adopted to analyze the heat and mass transfer characteristics of propane condensation in binary and ternary gas mixtures on a vertical cold plate. Multicomponent diffusion equations and the volume of fluid method (VOF) are used to describe the in-phase and inter-phase transportation. The conditions of different wall sub-cooled temperatures (temperature difference between the wall and saturated gas mixture) and the inlet molar fraction of methane/ethane are discussed. The numerical results show that ethane gas is more likely to accumulate near the wall compared with the lighter methane gas. The thermal resistance in the gas boundary layer is one hundred times higher than that of the liquid film, revealing the importance of diffusion resistance. The heat transfer coefficients increased about 11% (at ΔT = 10 K) and 7% (at ΔT = 40 K), as the molar fraction of ethane increased from 0 to 40%. Meanwhile, the condensation heat transfer coefficient decreased by 53~56% as the wall sub-cooled temperature increased from 10 K to 40 K.

High-frequency measurement of concentration in an isothermal methane–air gas mixture using spontaneous Raman spectroscopy

A high-frequency (1.5 kHz) spontaneous Raman spectroscopy measurement technique is developed and applied to measure external fluctuations generated in the local concentration of an isothermal binary gas mixture of methane and air. Raman excitation is provided by a high-frequency laser at 527 nm in dual-pulsed mode. The Stokes Raman signal is collected using an EMCCD camera coupled to a high-frequency intensifier as a shutter. The emitted signal is collected over the 596–627 nm wavelength range, which allows for the simultaneous tracking of methane and nitrogen Stokes Q-branch mode signals. Calibration curves are initially obtained for each species ({text{CH}}_{4} and {mathrm{N}}_{2}) based on steady-state concentrations, and further corrected during use to detect local unsteady mixture fluctuations at gas pulsation frequencies up to 250 Hz. The main novelty is the demonstration of Raman spectroscopy for the simultaneous multispecies measurement of unsteady concentrations of gas-phase methane and air mixtures using a laser beam with a high-repetition rate, low energy per pulse, combined with a high-frequency intensifier and a single camera.

Highly Efficient Propyne/Propylene Separation in a "Flexible-Robust" and Hydrolytically Stable Cu(II)-MOF.

Propyne/propylene separation is important in the petrochemical industry but challenging due to their similar physical properties and close molecular sizes. Metal-organic frameworks (MOFs) are a class of promising adsorbents for light hydrocarbon separations. Among them, the so-called "flexible-robust" MOFs combine the advantages of flexibility and rigidity in structure and could show enhanced gas separation selectivity as well as improved gas uptake at low pressure. Interpenetrated MOFs offer a platform to explore the "flexible-robust" feature of MOFs based on their subnetwork displacement in the process of gas adsorption. Herein, we present two hydrolytically stable MOFs (BUT-308 and BUT-309) with interpenetrated structures and fascinating propyne/propylene separation performance. BUT-308 is composed of interpenetrated 2D Cu(BDC-NH2)BPB layers (H2BDC-NH2 = 2-aminobenzene-1,4-dicarboxylic acid; BPB = 1,4-bis(4-pyridyl)benzene), while BUT-309 consists of twofold interpenetrated 3D pillared-layer Cu2(BDC-NH2)2(BPB-CF3) nets (BPB-CF3 = 2-trifluoromethyl-1,4-bis(4-pyridyl)benzene). Gas adsorption measurements showed that BUT-309 was a "flexible-robust" adsorbent with multistep adsorption isotherms for C3H4 rather than C3H6 at a wide temperature range. The guest-dependent pore-opening behavior endows BUT-309 with high potential in the C3H4/C3H6 separation. The C3H4 adsorption measurements of BUT-309 at 273-323 K showed that the lowering of the temperature induced the pore-opening action at lower pressure. Column breakthrough experiments further confirmed the capability of BUT-309 for the efficient removal of C3H4 from a C3H4/C3H6 binary gas, and the C3H6 processing capacity at 273 K (15.7 cm3 g-1) was higher than that at 298 K (35.2 cm3 g-1). This work shows a rare example of "flexible-robust" MOFs and demonstrated its high potential for C3H4/C3H6 separation.

Mixed matrix iongel membranes containing azo-porous organic polymers: Influence of temperature, pressure and water vapour on CO2 separation

The effect of temperature, pressure, and humidity content in the gas separation performance of iongel membranes are crucial parameters that should be assessed to determine the real potential of these materials to be used in CO2 separation processes. In this work, we present a detailed study on the impact of temperature (303, 323 and 353 K), pressure (2 and 4 bar), gas composition and water vapour content (between 11 and 21% of relative humidity) on the performance of iongels containing azo-porous organic polymers (azo-POPs), for CO2/N2 and CO2/CH4 binary gas separations. The iongels combining 80 wt% of the ionic liquid (IL) [C2mim][TFSI], 20 wt% of poly(ethylene glycol) diacrylate (PEGDA) and 0.5 wt% of different azo-POPs were prepared by a solvent-free UV curing method. At the lower temperature, the pressure increase seems to have a negative impact on the CO2 permeability of the prepared mixed matrix iongel membranes (MMIMs). However, the opposite behaviour was found when the temperature increases. Moreover, the presence of humidity in the feed gas stream affects the gas separation performance of the studied iongels, since the CO2 permeability greatly increases with increasing humidity in the gas mixture, while the selectivity decreases, for both gas separations under study. In general, the high pressure and temperature, and the presence of humidity have a significant influence on the separation performance of the studied iongel membranes, due to induced alterations in their structure and overall stability.

Determination of Concentration-Dependent Effective Diffusivity of Each Gas Component of a Binary Mixture in Porous Media Saturated with Heavy Oil under Reservoir Conditions

Summary One frequently used enhanced heavy oil recovery technique is gas injection, during which heavy oil viscosity is reduced due to diffusion of gaseous components and heavy oil swelling in porous media. Effective diffusivities of gas components are generally assumed to be constants, while no attempts have been made to determine both the concentration-dependent effective diffusivity in porous media saturated with heavy oil and the preferential contribution of each component in a binary/ternary gas mixture. In this study, a pragmatic and robust technique has been proposed to determine the concentration-dependent effective diffusivity of each gas component by reproducing the experimental measurements during pressure decay tests for CO2-C3H8-heavy oil systems in porous media. Experimentally, CO2 and C3H8 are utilized to diffuse into sandpacks fully saturated with heavy oil. Under a constant temperature within a thermostatic chamber, the pressures of the aforementioned gas(es)-heavy oil systems are consistently tracked and saved while gas samples are taken at the start and end of the diffusion tests for gas chromatography analyses. Theoretically, a mass transfer model is formulated to determine effective gas diffusivity in heavy oil as a concentration-dependent function by incorporating Fick’s second law and the modified Peng-Robinson equation of state (PR EOS). The concentration-dependent effective diffusivity for each gas component is ascertained when the measured pressure profiles and gas compositions are matched well to their correspondingly calculated values with minimum deviations. Compared to either a constant assumption or a linear concentration-dependent relation with respect to diffusivity, an exponential concentration-dependent relation leads to more accurately reproducing the measured pressure profiles. Compared with pure CO2, its effective diffusivity in a binary (i.e., CO2 and C3H8) gas system is found to be larger, indicating that C3H8 accelerates the CO2 mass transfer into heavy oil under the same circumstances. Furthermore, this study confirms that a larger tortuosity of a porous medium leads to a longer diffusion path with less contact between gas and liquid phases and that a lower concentration of a gaseous component yields a lower effective diffusivity.

Inversion in binary gas mixtures in rarefied flow conditions: Direct simulation Monte Carlo solution and comparison with the analytical solutions at free molecular regime

This paper analyzes the mixing of gases in a plane channel at rarefied conditions. The direct simulation Monte Carlo method is employed to simulate gas mixing in parallel mixers working at different Knudsen numbers and having different values of wall accommodation coefficient. Results show that the normal-to-wall component of the mole fraction gradient may have the same sign as the corresponding component of the diffusive mass flux vector near the diffuse solid walls in contrast to the predictions of Fick's law for continuum conditions. This non-continuum behavior, which is called “inversion” in the present study, will become more pronounced at higher Knudsen numbers, whereas it will become less evident for smaller wall accommodation coefficients. To confirm that the observed phenomenon is consistent with the basic physical laws governing the rarefied gas dynamics and it is not an artifact of the numerical method, a new analytical model based on the kinetic theory of gases is developed for the parallel mixers that have diffuse walls and are working in the free-molecular regime. Excellent agreement is observed between the analytical and direct simulation Monte Carlo results in the free molecular flow regime. Both methods predict the occurrence of inversion near the diffuse walls at highly rarefied flow conditions.

Ab Initio Prediction of Adsorption Selectivities for Binary Gas Mixtures on a Heterogeneous Metal–Organic Framework Surface

<i>Ab Initio</i> Prediction of Adsorption Selectivities for Binary Gas Mixtures on a Heterogeneous Metal–Organic Framework Surface

Impurity Analysis of 5.5 N Nitrogen Gas and Its Impact on the Preparation of Class I Type Calibration Gas Mixtures

AbstractKnowledge of impurities in matrix gas is one of the critical requirements for the preparation of class I type calibration gas mixtures (primary reference gas mixtures, PRGMs) as per ISO 6142‐1. PRGMs are prepared gravimetrically using high‐purity component gas and high‐grade nitrogen, here 99.9995 % (5.5 N) as matrix gas. In this study, quantification of gaseous impurities such as moisture (H2O), methane (CH4), and carbon monoxide (CO) in 5.5 N nitrogen is performed using CRDS (cavity ring down spectroscopy). Carbon dioxide (CO2) and total hydrocarbons (THC) are analyzed using gas chromatography flame ionization detector (GC‐FID), while the determination of nitrogen dioxide (NO2) impurity is conducted colorimetrically using a UV‐Vis spectrophotometer. Total impurities in 5.5 N nitrogen are found to be (2945±21.5) ppb. The impact of utilizing this nitrogen is examined through the stability study of ambient range binary component gas mixtures of CH4 and CO in nitrogen and found that 5.5 N nitrogen can be used as matrix gas for preparing PRGMs of CH4 and CO. However, the component gas impurity present in nitrogen potentially affect the accuracy of gravimetrically prepared gas mixture.

The ecological transition of the extreme energy events experiment

The need for reducing the emission of gases, potentially contributing to the greenhouse effect and climate change, has impacted many fields, including scientific research. The Extreme Energy Event (EEE) collaboration started, already several years ago, a series of tests aiming at finding a more eco-friendly replacement for the gases used in the Multigap Resistive Plate Chambers (MRPCs) of its network.These tests identified a promising binary gas mixture, and data taking has begun with a subset of the telescopes of the EEE network, making EEE the first experiment in the world completely implemented with MRPCs and operating with an eco-friendly gas mixture. Here the results of the tests and a preliminary comparison of the telescope performance measured with the standard (non eco-friendly) and the new eco-friendly gas mixtures are presented and discussed.

On the identity of the phase behavior in the simplest model of a binary gas mixture for square, honeycomb, and one-dimensional lattices

A complete analysis of the phase diagram of the adsorption lattice gas model of a binary gas mixture on one-dimensional and honeycomb lattices in the ground state with nearest neighbor interactions between particles was carried out. We found that in the parameter space of the lateral interactions for one-dimensional and honeycomb lattices, their division into regions with different topologies of phase diagrams is the same as for a square lattice.

Multicomponent Gas Detection Method via Dynamic Temperature Modulation Measurements Based on Semiconductor Gas Sensor

Leakage of organic gas in industrial environment can easily cause fire and explosion accidents. Rapid detection of gases type and concentration is the premise for emergency treatment of these situations. Typically, the single semiconductor sensor cannot detect multi-component gas. Here, a new multi-component gas detection method was proposed based on the temperature-response relationship of sensor. This method has low power consumption, low cost and long-term monitoring, which can guide the future exploration of deployable sensors. Firstly, the parameters were optimized according to cosine distance to reflect the maximum difference of temperature-response relationship. Then coordinate system transformation was carried out to further magnify the difference between gases. Finally, the multi-component gas was recognized by using rational taylor function fitting. As a proof-of-concept, we measured the type and concentration of toluene and butanone multi-component gas with mean error of 6.34&#x0025; and 4.32&#x0025; respectively. We analyzed the gas-sensing response mechanism, the theoretical support of the optimized parameters and the causes of local errors. As a universal method, binary component gas detection was <b>explored</b> containing toluene, butanone, acetic anhydride, acetone and diethyl ether.

Fruit waste (pomelo peels)-derived activated carbons for biogas upgradation and capture of green house gases from flue gas and low concentration coalbed methane

Rising emissions of greenhouse gases, such as CO2 and CH4, due to anthropogenic activities cause several adverse environmental impacts and encourage technological development for their effective capture and separation. The present work addresses a facile hydrothermal approach to impregnate K2CO3 and K2C2O4 into pomelo peels (fruit waste), followed by thermochemical activation for preparing activated carbons, i.e., PKC and PKOX, respectively, as adsorbents for biogas upgradation (CO2/CH4) and capture of greenhouse gases from flue gas (CO2/N2) and low concentration coalbed methane (CH4/N2). The high CO2 sorption capacity of PKC (4.67 mmol.g-1) and PKOX (3.96 mmol.g-1) at 298 K and 1 bar is attributed to their high surface area (1224–1371 m2.g-1), excellent microporosity, nitrogen-based functionalities, and turbostratic structural features. The ideal adsorbed solution theory (IAST) model is applied to estimate separation selectivity for binary gas mixtures, i.e., CO2/N2 (15:85), CO2/CH4 (45:55), and CH4/N2 (30:70) using PKC and PKOX adsorbents. The adsorption selectivity of PKC and PKOX for CO2/CH4 is found to be 143% and 296% higher compared to a widely used commercial activated carbon, signifying the potential of PKOX for biogas upgradation via adsorptive separation of CO2. The adsorption selectivity of PKC and PKOX for CO2/N2 is estimated to be 124% and 119% higher than commercial activated carbon, revealing the potential of both PKC and PKOX for capturing CO2 from flue gas to minimize its release in the atmosphere.