Polar Gases Research Articles

Comparison of Automated Extraction Techniques for Volatile Analysis of Whole Milk Powder.

Volatile profiling of whole milk powder is valuable for obtaining information on product quality, adulteration, legislation, shelf life, and aroma. For routine analysis, automated solventless volatile extraction techniques are favored due their simplicity and versatility, however no single extraction technique can provide a complete volatile profile due to inherent chemical bias. This study was undertaken to compare and contrast the performance of headspace solid phase microextraction, thermal desorption, and HiSorb (a sorptive extraction technique in both headspace and direct immersion modes) for the volatile analysis of whole milk powder by gas chromatography mass spectrometry. Overall, 85 unique volatiles were recovered and identified, with 80 extracted and identified using a non-polar gas chromatography column, compared to 54 extracted, and identified using a polar gas chromatography column. The impact of salting out was minimal in comparison to gas chromatography column polarity and the differences between the extraction techniques. HiSorb extracted the most and greatest abundance of volatiles, but was heavily influenced by the number and volume of lactones extracted in comparison to the other techniques. HiSorb extracted significantly more volatiles by direct immersion than by headspace. The differences in volatile selectivity was evident between the techniques and highlights the importance of using multiple extraction techniques in order to obtain a more complete volatile profile. This study provides valuable information on the volatile composition of whole milk powder and on differences between extraction techniques under different conditions, which can be extrapolated to other food and beverages.

NO2‐Affinitive Amorphous Conjugated Polymer for Field‐Effect Transistor Sensor toward Improved NO2 Detection Capability

AbstractThree conjugated polymers (CPs) containing indolocarbazole‐based similar conjugated frameworks are designed to investigate the NO2 detection capability of field‐effect transistor (FET) sensors. The partly linear aliphatic side chain strengthens the crystallization tendency of the CPs, but the crystallinity is critically degraded when introducing an ethylene oxide (EO)‐modified side chain to the same conjugated framework. Although the highly crystalline morphology of the CP helps to achieve high hole mobility, the NO2 response rate of the CP‐based FET sensor is severely deteriorated because of the suppression of NO2 diffusion into the CP matrix. The polar and flexible EO‐modified side chain is helpful to improve the NO2‐affinity of the CPs and induce favorable pathways for NO2 diffusion, ultimately providing enhanced detectivity with better NO2‐response characteristics. As a result, despite low charge carrier mobility due to pure amorphous nature, the CP with EO‐modified side chains provides an exceptional sensitivity of 180%/ppm upon NO2 (100 ppb) exposure for 50 s, including distinct detectivity toward other environmentally abundant harmful polar gases, such as SO2, NO, and NH3.

Drastically boosting volatile acetone capture enabled by N-doping activated carbon: An interesting deep surface digging effect

Affording the ultrahigh structural properties and rich surface groups in traditional activated carbon (AC) together to enable the efficient control of polar volatile organic chemicals (VOCs) is significant but challenged. Herein, we report the skilled construction of super activated carbon (AC) adsorbent (SBET = 4402 m2 g−1) via N-doping tactic to trigger the deep surface digging effect for banana peel-derived AC (SBET = 3897 m2 g−1) and remarkably reinforced the multilayer adsorption behavior by the post-implanted surface N species. Impressively, the resultant optimized adsorbent UC-5 shows nearly 1.83 folds enhancement of polar VOCs(volatile organic chemicals) that acetone adsorption capacity (44.89 mmol g−1) under 30 kPa of acetone partial pressure compared to the original AC (24.57 mmol g−1), which is known as the record acetone adsorption capacity. Besides, the boosting adsorption effect was well inherited and enlarged under a higher saturated vapor pressure of acetone in the static adsorption process, which was further evidenced by dynamic adsorption breakthrough experiments. The intensive studies revealed that the surface digging of the used urea dopant not only contributed to the enriching of surface N and improved the structural properties and thermal stability (575 °C) but also reserved more oxygen content of original AC compared to the resulted counterparts using melamine, which were together responsible for the drastic increase of acetone adsorption. This work provides the new possibility for the adsorption of polar VOCs gas via exploiting the outstanding structural properties and surface N interaction.

On the enormous enhancement in water evaporation rates obtained by employing a different polar ambient

AbstractEnhancing evaporation rates are of great practical interest in many technological applications, such as water desalination or drying in industry. Evaporation mass flux is a function of ambient temperature, relative humidity, and velocity of the air passing over it. Since the conventional methods of increasing evaporation, namely increasing temperature, surface area, and so on, may not be always practically feasible or economical, novel methods of evaporation enhancement are necessary. The current study proposes that the introduction of a polar gas ambient above an evaporating liquid can drastically enhance its evaporation rate when the dipole moments of the evaporating liquid and the ambient gas are comparable. Thus, we explore the possibility of evaporation enhancement of water by introducing a polar Tetrafluoroethane gas ambient. The weight loss of water due to evaporation as well as the ambient temperature and air circulation conditions were measured. For each case, a companion experiment was carried out simultaneously under the same ambient conditions but without the presence of polar gas ambient. Each experiment lasted for 4 h. The evaporation rate has been found to be crucially dependent upon the polar gas ambient, the temperature as well as circulation conditions. Depending upon the temperature and circulation conditions, an enhancement of 59%–373% in evaporation rate has been recorded by the introduction of tetrafluoroethane gas ambient over the water surface. Some insights into the underlying mechanisms have been suggested in light of the physics of the evaporation process. Finally, some comparisons in the measured enhancement in evaporation rates under different experimental conditions are observed to concur with the suggested physical mechanism.

An equation of state based on the intermolecular potential and the radial distribution function to estimate the virial coefficients by using PvT chaotic data

We derive a new equation of state (EOS) for any non-polar, polar or quantum gas and any intermolecular potential through an approximation of the radial distribution function based on the Ornstein-Zernike equation. Such EOS is applied to estimate the virial coefficients B and C using two approaches. On one hand, B and C are directly computed from the proposed EOS considering the Mie potential for neon and water steam, which leads to values in very good agreement with the experimental data. On the other hand, the proposed EOS is applied in the context of a thermodynamic model to estimate B and C by fitting the simulated chaotic PvT data at an almost constant temperature. Such estimations of B and C are compared with the experimental values, which allows elucidating if B and C have a significant contribution on the virial equation at the considered pressures and temperatures. This methodology is applied to nitrogen and helium4 considering the intermolecular potentials of Mie, Morse, Kihara and Buckingham. For the considered gases and intermolecular potentials, the calculated values of B and C are in very good agreement with experimental data in a wide range of pressures and temperatures.

Vapour-liquid equilibria (VLE) and gas hydrate phase equilibria predictions using the cubic-plus association equation of state: CSMGem extension to association EoS model

Inaccurate predictions of the vapour-liquid equilibria of polar gas hydrate formers and organic inhibitors can lead to erroneous hydrate phase equilibrium predictions for these associating components. In this work, parameters of the cubic plus association equation of state (CPA-EoS) were optimized for associating components by simultaneous minimization of absolute errors of saturated liquid densities and vapour pressures compared to experimental data. Model prediction accuracies were compared with experimental data after optimizing binary interaction parameters. The proposed association equation of state (based on CPA-EoS) was employed to predict vapour-liquid equilibria of water/N2/H2+non-associating hydrate formers. Water was modelled using a 4C association scheme, i.e., comprising two proton donor and acceptor sites on each water molecule, which has been used previously (Chapman, 1989; Hammerschmidt, 1934; Kontogeorgis, 2006a; Tsivintzelis, 2010; Tsivintzelis et al., 2014; Wichterle and Kobayashi, 1972; Williams and Katz, 1954). For model development and validation, phase envelopes were predicted and validated with experimental solubility data for several systems. Furthermore, the CPA-EoS was also coupled with the Colorado School of Mines Gibbs Energy Minimization (CSMGem) algorithm for hydrate phase equilibria predictions. The predictions were in close agreement with experimental hydrate phase equilibria measurements.

Elastic loading enhanced NH3 sensing for surface acoustic wave sensor with highly porous nitrogen doped diamond like carbon film

We proposed a surface acoustic wave (SAW) NH3 gas sensor based on nitrogen doped diamond like carbon (N-DLC) film. The N-DLC film, prepared using a microwave electron cyclotron resonance plasma chemical vapor deposition (ECR-PECVD) method, is highly porous and physically and chemically stable, and have active polar groups on its surface, which can selectively absorb polar NH3 gas molecules. These features of the film lead to the high sensitivity, low noise and excellent stability of the sensor. The sensor can achieve capabilities of in-situ monitoring NH3 in a concentration range from 100 ppb to 100 ppm with fast response (∼5 s) and recovery (∼29 s) at room temperature. The NH3 sensing mechanism is attributed to the decreased porosity of the N-DLC film caused by adsorbed NH3 molecules on its polar groups, which leads an increase of the elastic modulus of the film.

Competitive and Synergistic Adsorption of Mixtures of Polar and Nonpolar Gases in Carbonaceous Nanopores.

Most adsorption applications involve mixtures, yet accurate predictions of the adsorption of mixtures remain challenging, in part due to the inability to account for the interplay between adsorbate-adsorbate and adsorbate-adsorbent interactions. This study involves a comprehensive Monte Carlo simulation of the adsorption of two groups of mixtures (namely, supercritical and subcritical ones) in carbon nanopores and quantifies Henry's constants, isotherms, energetics, and density distributions in the pores. When interadsorbate interactions are negligible (e.g., in supercritical mixtures such as mixtures of nonpolar gases), adsorbates behave like ideal gases and the adsorption isotherm can be predicted with the ideal adsorbed solution theory (IAST). However, when interadsorbate interactions become significant, IAST fails. This study reveals that (1) in mixtures of polar and nonpolar gases, the stronger intermolecular interaction for the polar constituent leads to synergistic adsorption that causes the nonpolar adsorbate to desorb and (2) for mixtures of polar gases, such as ethanol and water, the adsorbate-adsorbate interactions are so dominant that the unfavorable adsorbate-adsorbent interactions are overcome, such that water adsorbs onto the hydrophobic adsorbent. The competitive and synergistic interactions highlighted here are expected to be valuable in enhancing gas separations.

Detection of the organic solvent vapors by the optical gas sensors based on polyaminoarenes

The important problem to ensure the safety of life is the development of effective methods for monitoring of toxic gases in the atmosphere and industrial premises. To ensure such control, various gas sensors are developed that work on the effects of changes in electrical resistance, optical absorption or radiation in a certain spectral range. Most known gas sensors have high operating temperatures, which creates some difficulties in their operation, so more and more attention is paid to sensors based on conjugated electrically conductive polymers, in particular, polyaminoarenes. In result of absorption of inorganic polar gases such as ammonia, nitrogen oxide, hydrogen chloride and others the significant changes in conductivity, optical absorption and morphology of polyaminoarene films are observed. However influence of organic solvent vapors on the optical spectra of polyaminoarene films for today is poorly studied. In the present work the functional polymer films of polyanisidine (PoA) and polytoluidine (PoTI) are proposed as sensitive elements of optical sensors operating at room temperatures. The sensitive films on the transparent SnO2 surface were prepared by electrodeposition. The influence of vapors of organic solvents (dimethylformamide, tetrahydrofuran, chloroform, nitrobenzene, toluene) on the optical characteristics of PoTi and PoA films was established. The optical absorption spectra investigated PoA film was characterized by two band with maximum near 360–410 nm (π–π* transition) and broad band in the range of 620–950 nm which is a superposition of the second and third bands. Influence of organic vapors causes the changes in films coloration. The maximum of sensitivity to the organic vapors for PoTI films in all cases is observed at λ > 550 nm and extends to near-infra-red area indicating a formation of free charge carriers of polaron type. Nonpolar solvent vapors insignificantly affect the optical properties of polyaminoarene films responсes to spectral changes in the visible and NIR range of spectrum. A highest gas sensitivity of optical signal was observed under influence of dimethylformamide and tetrahydrofuran vapors. The time to establish the steady-state value of the optical response is 30–60 s for PoTi, while for PoA reaches 120–180 s depending on the nature of organic vapors.

Fabrication and characterization of Pebax-1657 mixed matrix membrane loaded with Si-CHA zeolite for CO2 separation from CH4

Polymeric membranes performance in gas separation can be improved by using zeolites as the filler in the polymer matrix to form mixed matrix membranes (MMMs). Pure-silica Si-CHA zeolite and Pebax-1657 copolymer are individually capable of separating acid gases from natural gas. However, the corresponding MMM has not been investigated in the literature. Therefore, in this work, Si-CHA zeolite was incorporated in the Pebax-1657 copolymer by solvent evaporation method to evaluate its performance in CO2 separation from CH4. The fillers distribution in the polymeric matrix, structural characteristics, and interaction of fillers with the polymer in MMMs were characterized via SEM, FTIR, DSC, XRD, and stress-strain analyses. Moreover, the CO2/CH4 separation tests of the membrane as a function of zeolite content and applied feed pressure was explored. The structural analyses of the membranes showed the best filler distribution and the filler-polymer interaction in the membrane for the sample containing 10 wt% of the filler. Furthermore, pure gas permeation tests revealed that the best separation performance was obtained for the same membrane at an applied gauge pressure of 4 bar. In this membrane, 103% improvement in CO2 permeability, and 71% increase in CO2/CH4 ideal selectivity was achieved compared to the neat polymeric membrane. The separation performance of the MMM 10% was evaluated using CO2–CH4 mixed gas. In this situation, decreased CO2/CH4 separation factor was observed due to the plasticization of PEO chains with polar CO2 gas.

Wind, Convection and Fetch Dependence of Gas Transfer Velocity in an Arctic Sea‐Ice Lead Determined From Eddy Covariance CO2 Flux Measurements

AbstractThe air‐water exchange of trace gases such as CO2 is usually parameterized in terms of a gas transfer velocity, which can be derived from direct measurements of the air‐sea gas flux. The transfer velocity of poorly soluble gases is driven by near‐surface ocean turbulence, which may be enhanced or suppressed by the presence of sea ice. A lack of measurements means that air‐sea fluxes in polar regions, where the oceanic sink of CO2 is poorly known, are generally estimated using open‐ocean transfer velocities scaled by ice fraction. Here, we describe direct determinations of CO2 gas transfer velocity from eddy covariance flux measurements from a mast fixed to ice adjacent to a sea‐ice lead during the summer‐autumn transition in the central Arctic Ocean. Lead water CO2 uptake is determined using flux footprint analysis of water‐atmosphere and ice‐atmosphere flux measurements made under conditions (low humidity and high CO2 signal) that minimize errors due to humidity cross‐talk. The mean gas transfer velocity is found to have a quadratic dependence on wind speed: k660 = 0.179 U102, which is 30% lower than commonly used open‐ocean parameterizations. As such, current estimates of polar ocean carbon uptake likely overestimate gas exchange rates in typical summertime conditions of weak convective turbulence. Depending on the footprint model chosen, the gas transfer velocities also exhibit a dependence on the dimension of the lead, via its impact on fetch length and hence sea state. Scaling transfer velocity parameterizations for regional gas exchange estimates may therefore require incorporating lead width data.

Polar Offshore Engineering Equipment: Development Status and Key Technologies

Polar offshore engineering equipment provides a major platform and symbolizes the strength of China to participate in Arctic offshore oil and gas development. Currently, the design, construction, and support capacities of China’s polar offshore engineering equipment are not internationally recognized, which does not match with the large shipbuilding sector of China. In this article, we analyze the development demand for polar offshore engineering equipment in China, present the application status of these equipment, investigate the key technologies, and summarize the existing problems regarding these equipment in China. Furthermore, we propose the establishment of a research and application innovation project of common key technologies for Arctic offshore oil and gas exploration and development, an international research and development center for polar offshore oil and gas engineering technologies, and a China–Russia Arctic energy joint venture company. This study centers on the coordination of the Arctic development and environmental protection capabilities, and aims to provide a reference for developing the polar offshore engineering equipment in China and provide guidance for China’s participation in Arctic oil and gas development.

CO2/CH4 mixed gas separation using graphene oxide nanosheets embedded hollow fiber membranes: Evaluating effect of filler concentration on performance

Graphene oxide (GO) nanosheets-based composite polymeric membranes are being explored for the effective separation of gases owing to hydrophilic nature and abundant oxygen moieties on their surface that attracts the polar gases. In this study, the effect of GO nanosheets concentration on the CO2/CH4 mixed gas separation performance of polysulfone (Psf) hollow fiber mixed matrix membranes (HFMMMs) was examined. The different concentration of GO, i.e., 0.25, 0.5, and 0.75 wt% of the polymer dope solution, was used. Hollow fiber membranes (HFMs) were prepared using dry/wet quench method with water as non-solvent, and physicochemical properties were evaluated. Morphological changes were observed in the Psf/GO HFMMMs. The gas separation performance study of the HFM samples was carried out using pure CO2 and CH4 gases at 1–5 bar transmembrane pressure and 25 ± 2 °C. It was found that HFMMMs with 0.25 wt% GO nanosheets (PG25) showed 137% higher ideal CO2/CH4 selectivity than the pristine HFMs. In case of the mixed gas permeation studies using feed consisting of 50:50 vol% of CO2 and CH4, the PG25 HFMMMs showed 201% higher CO2/CH4 selectivity than that of the pristine HFMs. Moreover, the PG25 HFMMMs showed separation performance stability when they were applied for the long-term stability study. These results indicate that 0.25 wt% GO nanosheets in Psf is the optimum concentration which gives improved CO2/CH4 mixed gas separation performance.

Quench dynamics of two-component dipolar fermions subject to a quasiperiodic potential

Motivated by recent experiments in fermionic polar gases, we study the non-equilibrium dynamics of two-component dipolar fermions subject to a quasiperiodic potential. We investigate the localization of charge and spin degrees of freedom time evolving with a long-range spin-SU(2) symmetric fermionic Hamiltonian, by calculating experimentally accessible dynamical observables. To study the non-equilibrium dynamics, we start the time evolution with two initial states at half-filling: (i) product state with doublons $|\uparrow \downarrow 0 \uparrow \downarrow 0 \uparrow \downarrow 0 \uparrow \downarrow 0 \uparrow \downarrow \rangle$ and (ii) product state with singlons $|\uparrow \ \downarrow \ \uparrow \ \downarrow \ \uparrow \ \downarrow \ \uparrow \ \downarrow \ \uparrow \ \downarrow \ \rangle$. We carried out the real-time evolution via the fermionic Hamiltonian using exact diagonalization(ED) and the time-dependent variational principle (TDVP) for finite Matrix product states(MPSs), within experimentally relevant time scales. For the product state with doublons, we observe a delocalized to localized phase transition varying disorder strengths, by monitoring the decay of charge imbalance with time. For the long-range interacting Hamiltonian of our focus, and in the presence of strong enough disorder, starting the time evolution with singlons we find a strong reduction in the spin delocalization, contrary to results of previous studies using the disordered short-range (on-site) Hubbard model with SU(2) symmetry. Our predictions for localization of both charge and spin should be observable in ultra-cold experiments with fermionic dipolar atoms subject to a quasiperiodic potential.

Highly sensitive gas sensing material for polar gas molecule based on Janus group-III chalcogenide monolayers: A first-principles investigation

Gas sensors play an indispensable role in industrial, personal safety and environmental protection, and have been widely investigated by researchers. In some cases, the sensitivity of a two-dimensional material sensor can be enhanced by generating vacancies or applying an external electric field. Similar results can be achieved using Janus 2D materials, which have an inherent electric field and are good candidates for high-sensitivity gas sensors. In this study, the electronic and transport properties of Janus group-III chalcogenide monolayers (Ga2SSe, In2SSe) were investigated for detecting CO2 and NO2 using first-principles calculations. For several parameters that affect the performance of gas sensors, such as adsorption distances, adsorption energies, charge transfers and density of states (DOS), a detailed comparison of Janus group-III chalcogenide monolayers has been provided with their pristine systems, Janus group-III chalcogenide monolayers (Ga2SSe, In2SSe) have high selectivity. It was mainly ascribed to the built-in electric field caused by the out-of-plane asymmetric structure of Janus monolayer which enhances the dipole-dipole interaction between the polar gas molecule and the 2D materials. And the variation of transmission spectra of the Janus group-III chalcogenide monolayer before and after adsorbing molecules further proves the feasibility of this kind of material as a high-sensitivity gas sensor.

VOCs adsorption of resin-based activated carbon and bamboo char: Porous characterization and nitrogen-doped effect

The objective of this study was to assess the VOCs (methanol and toluene) adsorption capacity of doped porous carbon materials (resin-based carbon and bamboo char) by experiments and theoretical calculations. Results showed N-doped porous carbon material exhibited a high specific area (2293.2 m2 g−1), a desirable microporocity (0.90 cm3 g−1), and a large adsorption capacity for methanol (915.3 mg g−1) and toluene (622.9 mg g−1), which were better than those derived from bamboo char. According to the density functional theory calculation, in terms of different N-containing functional groups, the results showed that methanol adsorption was dominated by the electrostatic interaction between the carbon surface and methanol, while toluene was mainly trapped through π-π dispersive interaction with the aromatic ring moving to the carbon surface. This study gave us hints to conduct the doping of polarized element to adsorb polar gases.

Precise determination of LJ parameters and Eucken correction factors for a more accurate modeling of transport properties in gases

The kinetic gas theory, in particular the equations of Chapman and Enskog, proved to be good and widely applicable approximations for modeling transport properties like diffusion coefficients, viscosities and thermal conductivities. However, these equations rely on at least the Lennard-Jones parameters and for polar gases also the dipole moment. In the scientific literature, the Lennard-Jones parameters are fitted to only one experimentally determined transport coefficient. This approach leads to good agreement between the Chapman Enskog equations employing the so obtained parameters with the experimental data for this specific transport property. However, utilizing the same parameters for modeling different transport properties oftentimes leads to distinct deviations. In this work, it is shown that the subset of Lennard-Jones parameters with which the Chapman Enskog equations can predict the experimental results with deviations comparable to the experimental uncertainty are not identical for each transport property. Hence, fitting towards one property doesn’t necessarily yield parameters that are suited to describe the other transport properties. In this publication, the Lennard-Jones parameters and a temperature dependent Eucken correction factor, leading to a significantly higher accuracy than the classical Eucken correction and also its modification by Hirschfelder, are therefore fitted towards all three transport properties simultaneously for seven exemplary gases. This approach leads to a significantly better agreement with experimental data for the three transport properties than the classical approach that relies on fitting to one single transport property and can be utilized to determine accurate sets of Lennard-Jones parameters and Eucken correction factors for any gas species. It provides a computationally inexpensive and practical method for the precise calculation of transport properties over a wide range of temperatures relevant for processes in the chemical industry.

A constitutive model for predicting the solubility of gases in water at high temperature and pressure

In the drilling and development of gas fields, gas exhibits good solubility in drilling fluids and in the formation water under high temperatures and pressures. Therefore, the prediction of the amount of dissolved gas in water plays a vital role in the development of natural gas. In this work, the principle of equal fugacity in a gas-liquid equilibrium, a non-iterative gas solubility prediction model was established. The gas-phase fugacity coefficient was calculated by the Peng-Robinson equation of state combined with the non-random mixing rule, and the liquid phase was calculated by Henry's law. The model can predict the solubility of CO2, CH4 and C2H6 in pure water at temperatures of 273–448 K and pressures of 0–100 MPa, with an error of less than 5.5%; however, the calculation accuracy for H2S was low. It is found that the effect of moisture in the gas phase of gas-liquid equilibrium cannot be ignored. Compared with the existing mixed gas solubility experimental data, this model could accurately calculate the solubility of non-polar mixed gases, such as CO2 + CH4, and CH4 + C2H6 mixture. For the mixtures containing a polar gas, the lower the polar gas content, the smaller was the prediction error of the model for the non-polar gas in the mixture. On the contrary, the higher the content of polar gas, the larger was the deviation in the prediction of non-polar gas in the mixture, but lower was the deviation in the prediction of polar gas. Finally, the ability of Krichevsky-Kasarnovsky equation to predict the solubility of pure gas was evaluated.

Adsorption effect of nitrogen, sulfur or phosphorus surface functional group on formaldehyde at ambient temperature: Experiments associated with calculations

Abstract The objectives of this study were to assess the formaldehyde (HCHO) adsorption capacity of doped porous carbon by experiments and theoretical calculations. Nitrogen, sulfur or phosphorus containing porous carbons were prepared with different precursors by activation with KOH at 700 °C and compared with commercial activated carbon (CAC), and used as the low HCHO concentration adsorbents in dry (dynamic) and wet (static) conditions. Results showed that the HCHO adsorption capacity of AC-N (2418.20 m2 g−1) for dynamic (13.60 mg g−1) and static (1.43 mg g−1) was greater than that of AC-S, CAC and AC-P. The specific surface area and the micropores volume were expected to markedly influence the adsorption capacity of HCHO. According to the DFT calculation, the adsorption energy of surface functional groups of phosphorus (−0.53296 eV) was the highest, followed by sulfur (−0.52646 eV) and nitrogen (−0.41246 eV), which indicated hydrogen bond interaction played an important role in the adsorption. In the GCMC slit model, the size of slit pores was positively correlated with the adsorption amount of HCHO. With the increase of the adsorption pressure, the surface functional groups had little effect on the adsorption of HCHO under the same size of the slit pores. Accordingly, for the high HCHO adsorption capacity, specific surface area and pore volume are the primary determinant, while surface functional group is the secondary determinant. This would provide a useful theoretical reference for the doping of polarized activated carbon to adsorb polar gases.

Optimization Methodology of Artificial Neural Network Models for Predicting Molecular Diffusion Coefficients for Polar and Non-Polar Binary Gases

In this study, an artificial neural network (ANN) is used to develop predictive models for estimating molecular diffusion coefficients of various gases at multiple pressures over a large field of temperatures. Two feed-forward neural networks NN1 and NN2 are trained using six physicochemical properties: molecular weight, critical volume, critical temperature, dipole moment, temperature, and pressure for NN1 and molecular weight, critical pressure, critical temperature, dipole moment, temperature, and pressure for NN2. The diffusion coefficients are regarded as the output. A set of 1252 gases (941 non-polar gases and 311 polar gases) is used for training and testing the ANN performance, and good correlations are found (R = 0.986 for NN1 and R = 0.988 for NN2). The result of the sensitivity analysis shows the importance of the six input parameters selected for modeling the diffusion coefficient. Moreover, the present ANN model provides more accurate predictions than other models.