Atm Pressure Research Articles

Effect of ion size disparity on the thermal hysteresis of ionic liquids

By means of computer simulations, the effect of varying anion to cation size ratio on the liquid–solid transition and on the thermal hysteresis behavior of a model ionic liquid is investigated. Constant pressure molecular dynamics simulations are carried out by considering different values of anion to cation size ratios at the same number density and 1 atm pressure. In this study, we find that changing ion size ratio affects the solidification or melting temperatures, latent heat, of the model ionic liquid. Within the considered range of anion to cation size ratios, solidification/melting temperature as well as area of thermal hysteresis loop decreases with increasing size ratio and thus illustrates the possibility to fine tune thermal hysteresis loop, which is relevant for phase change materials based thermal energy storage applications.

DEVELOPMENT OF NOVEL FLOW FIELDS FOR PEM FUEL CELLS: NUMERICAL SOLUTION AND EXPERIMENTAL VALIDATION

In the present study, the main purpose is to design flow channels with less pressure drop and higher performance compared to single serpentine flow channels which are found in the literature for PEM fuel cells. Within the scope of the present study, a numerical and experimental research was conducted on the design of the flow channels on bipolar plates. The fuel cell with a serpentine flow field was experimentally tested under conditions of 70°C temperature, 1 atm pressure, 100% humidification and 0.25 l/min anode/cathode flow rates, and analyzed numerically. This way, a numerical model verified with experimental data was obtained. 4 models (Models 1-4) with unique flow fields were designed and numerically analyzed to compare with the verified numerical model. The flow field percentages (channel to rib ratio) of the 5 models designed were fixed at a value of approximately 55.4%. For all designs, the channel width was set to 1.5 mm and the channel depth was set to 1 mm. Results indicate that the experimental data obtained were in accordance with the numerical results with an error margin of 5.3%. Based on the numerical analysis results at 0.6 V, current density increased by 23.9% in Model 1, 26.9% in Model 2, and 13.8% in Model 3 compared to the reference model while a 12% decrease was observed in Model 4.

Inside Back Cover: Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO 2 and Epoxides: From High Pressure and Temperature to Ambient Conditions (Angew. Chem. Int. Ed. 4/2022)

The synergetic binary phosphazene/triethylborane (TEB) system is highly active and selective towards the ring-opening alternating copolymerization of CO2 with different epoxides to prepare diverse CO2-based polycarbonates (CO2-PCs). In their Research Article (e202111197), Shaofeng Liu, Zhibo Li, and co-workers report that this metal-free organocatalyst can efficiently copolymerize CO2 with cyclohexene oxide under ambient conditions (1 atm pressure and room temperature), which is an environmentally friendly and more carbon-balanced way toward CO2 utilization.

Diffusion anisotropy of Ti in zircon and implications for Ti-in-zircon thermometry

Ti-in-zircon thermometry has become a widely used tool to determine zircon crystallization temperatures, in part due to reports of extremely sluggish Ti diffusion perpendicular to the crystallographic c-axis in this mineral. We have conducted Ti-in-zircon diffusion experiments, focusing on diffusion parallel to the c-axis, at 1 atm pressure between 1100 and 1540°C, with oxygen fugacities equivalent to air and the Ni-NiO buffer. There is no resolvable dependence of Ti diffusion in zircon upon silica or zirconia activity, or upon oxygen fugacity. The diffusion coefficient of Ti in zircon is found to be a weak function of its own concentration, spanning less than 0.5 log units across any profile induced below 1300°C. Ti diffusion in zircon, parallel to the c-axis at 1 atm pressure, is well described using:log10⁡DTi=[1.34(±1.44)−555425(±44820)Jmol−12.303RT(K)]m2s−1 where R is the gas constant in J/(mol⋅K). In conjunction with diffusion coefficients for Ti in zircon perpendicular to the c-axis reported by Cherniak and Watson (2007), strong diffusion anisotropy for Ti in zircon is observed. Diffusion parallel to the c-axis is ∼4-5 orders of magnitude faster than diffusion perpendicular to the c-axis within the experimentally constrained temperature range shared between these two studies (1540-1350°C). This difference increases if the data are extrapolated to lower temperatures and reaches ∼7.5-11 orders of magnitude between 950-600 °C, a typical range for zircon crystallization. Diffusion of Ti in natural zircons will predominantly occur parallel to the c-axis, and the Ti-in-zircon thermometer appears susceptible to diffusive modification under some crustal conditions. Temperatures calculated using this system should therefore be evaluated on a case-by-case basis, particularly when considering high-T, slowly cooled, reheated and/or small zircons.

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions

AbstractOrganophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6‐Tris[tri(1‐pyrrolidinyl)‐iminophosphorane]‐1,3,5‐triazine (C3N3‐Py‐P3) with a relatively low basicity (pKa=26.5 in CD3CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2‐based polycarbonates (CO2‐PCs) with high molar masses (Mn up to 275.5 kDa) at 1 MPa of CO2 and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO2/CHO copolymerization with TOF up to 95 h−1 at 1 atm pressure and room temperature.

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions.

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C3 N3 -Py-P3 ) with a relatively low basicity (pKa =26.5 in CD3 CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2 -based polycarbonates (CO2 -PCs) with high molar masses (Mn up to 275.5 kDa) at 1 MPa of CO2 and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO2 /CHO copolymerization with TOF up to 95 h-1 at 1 atm pressure and room temperature.

Effect of ionic liquid in a pressurized reactor to enhance CO2 photocatalytic reduction at TiO2 modified by gold nanoparticles

This work describes the synergic effect of gold nanoparticles as co-catalyst on TiO2 nanotubes (TNT/AuNP) in aqueous medium containing the ionic liquid (IL) 1-Butyl-3-methylimidazolium tetrafluoroborate, in a pressurized photocatalytic reactor, as a good strategy to enhance CO2 conversion into value-added products. The surface plasmon resonance of the gold NPs improve the photoexcitation under visible light and slightly change the TNT band gap from 3.2 to 2.9 eV. Methanol production using TNT/AuNP in aqueous medium containing 2% (v/v) BMIM-BF4, 1 g L−1 Na2SO3 as a hole scavenger, under 5 atm pressure and solar irradiation, produce up to 279.6 µM (µmol L−1) of methanol and 98.8 µM of methane, with the quantum yield of 1.12% at 440 nm. Isotope-labeled studies by GC/MS proved that 13CO2 is the source for photoproduction of 13CH3OH. The results indicate that the combination of the Au co-catalyst size, high pressure, and IL can provide efficient modulation of CO2 conversion.

Numerical investigation of a high-pressure gas medium preionization by runaway electrons

A comparative simulation of the generation and acceleration of runaway electrons in the discharge gap during the initiation of the discharge by nanosecond and subnanosecond pulses is carried out. We used a numerical model based on the PIC-MCC method. Calculations were carried out for N2 6 atm pressure. Numerical simulation of a formation process of the electron avalanche initiated by an electron field-emitted from the top of the cathode microspike was carried out taking into account the motion of each electron in the avalanche. Characteristic runaway electron trajectories, runaway electron energy gained during the motion through the discharge gap, times required for runaway electrons to reach the anode were calculated. We compared our results with calculations using well-known differential equation of electron acceleration using braking force in Bethe approximation. We solved this equation also for braking force based on real (experimental) ionization cross section. The reasons for the discrepancy in the calculation results are discussed.

“Electrical wind” in CO2–laser mixtures at superatmospheric pressures

This article presents the results of “electrical wind” investigations in CO2–laser mixtures at superatmospheric (1–12 atm) pressures. It is established that for a fixed value of the unipolar corona discharge current, the gas flow velocity does not depend on the pressure, but is determined by the chemical composition of the working mixture. The maximum values of the “electrical wind” velocity are achieved in carbon dioxide and molecular nitrogen and their values are 3.2 and 2.9 ms−1. In typical laser mixtures CO2:N2:He = 1:1:1 – 1:1:3 the velocity of the “electrical wind ” are in the range from 2.5 to 1.5 ms−.

Designing and application of a new medical instrument sterilization system using reactive oxygen species.

The aim of this study is to designand test a new medical sterilization system as an alternative to the techniques used in the sterilization of medical instruments. The designed system, which uses a new oxygen molecule allotrope (NOMA) in the reactive oxygen species, is developed as an alternative to the sterilization systems using other gases. The test was conducted on 12 different materials, each having a surface of 2cm2, sterilized under 120 °C at 1 atm pressure for 20minin the NUVE-OT 4060 sterilizer, and all surfaces were contaminated with a biological indicator Geobacillus stearothermophilus cultured in an incubator at 37 °C. Test samples in sterile Petri dishes were placed in a desiccator, and a sample was taken at 30-, 45-, and 60-mintest periods and were placed on an agar medium and put in a Memmert incubator IN75 at 37 °C; in the controls conducted following 16-18 h of incubation period, no bacterial growth was observed in the newly designed system tested with gram positive bacilli; moreover, it was observed that the new system was 100% effective in sterilizing the microbes as no growth was observed on the samples. Within the scope of this study, a faster, low-cost, low-temperature, residue-free, and human and environmental friendly system was developed and tested for sterilization of medical devices compared to existing sterilization methods using NOMA.

Electrochemical Reduction of CO2 on Au Electrocatalysts Under Commercially Relevant Condition

Much effort has been devoted for development of effective catalysts for the electrochemical reduction of CO2 (CO2RR). For CO2RR, performing H-cell experiments is the most common catalyst screening method where the reactant CO2 gas is usually dissolved in an aqueous bicarbonate-based electrolyte1. However, the low solubility of CO2 in aqueous solutions (∼35 mM at 298 K and 1 atm pressure) causes mass transport limitations when using dissolved CO2 as the reactant. Based on H-cell measurements gold (Au) is one of the most selective catalysts for CO2RR to CO2. However, preparation of shape-controlled Au nanoparticles (NPs) based on conventional synthesis methods requires the use of surfactants and capping agents such as polyvinylpyyrolidone (PVP). Here, we report the electroreduction of CO2 on ligand-free Au NPs (Au-PVP-free NPs) and Au NPs with PVP (Au-PVP NPs) that were produced by laser ablation3. For this purpose, we used our recently introduced gas diffusion electrode (GDE) setup1 which supplies a continuous CO2 stream at the electrode−electrolyte interface to circumvent CO2 mass transport limitations of the conventional liquid cells4. Moreover, we performed same experiments in the H-cell setup to compare between these two screening methods. In both measurement setups, the presence of PVP favors hydrogen evolution reaction (HER). However, we also observed differences in performance of the same catalyst at same experimental conditions in these two setups, which highlights the importance of having commercially relevant conditions for catalyst screening.Finally, we investigated the influence of different binders and membranes on selectivity and activity of Au-PVP-free NPs that led to more robust electrodes performance for CO2RR. Figure 1

Shock tube investigation of high-temperature, extremely-rich oxidation of several co-optima biofuels for spark-ignition engines

To reduce the reliance on fossil fuels in the transportation sector and increase combustion efficiency, the Co-Optima initiative from US Department of Energy identified the top 10 biofuels for downsized, boosted, spark-ignition engines. Most of these biofuels have detailed reaction mechanisms available in literature developed based on studies at temperatures lower than 1700 K and an equivalence ratio of less than five. As such, the performance of these detailed mechanisms at high temperature and extremely rich conditions are unknown. It is important to validate kinetic mechanisms at these conditions because they are conducive to soot formation. Prediction of soot by chemical kinetic models relies on the prediction of underlying benchmark species like carbon monoxide and ethylene. In this work, we conduct high temperature (1700–2050 K) and high equivalence ratio(Φ=8.6) oxidation of these biofuels, namely 2,4,4-trimethyl-1-pentene (α-diisobutylene), ethanol, cyclopentanone, methyl acetate, and 2-methylfuran, blended in ethylene behind reflected shock waves at 4–4.7 atm pressure. Carbon monoxide and ethylene time histories are measured simultaneously using a continuous feedback quantum cascade laser near 4.9 µm and a tunable CO2 gas laser at 10.532 nm, respectively. Results show that ethanol blend forms more carbon monoxide than other biofuels and consumes ethylene faster than the biofuel blends in the temperature range considered. The performance of different mechanisms in literature are evaluated against the experimental results. The novel reaction mechanism ‘the Co-Optima model’, which includes the sub mechanisms for all the biofuels in this study, was found to be the best mechanism for the experimental conditions studied.

High Turnover Pd/C Catalyst for Nitro Group Reductions in Water. One-Pot Sequences and Syntheses of Pharmaceutical Intermediates.

Commercially available Pd/C can be used as a catalyst for nitro group reductions with only 0.4 mol % Pd loading. The reaction can be performed using either silane as a transfer hydrogenating agent or simply a hydrogen balloon (∼1 atm pressure). With this technology, a series of nitro compounds was reduced to the desired amines in high chemical yields. Both the catalyst and surfactant were recycled several times without loss of reactivity.

Cinética del secado de las hojas de las especies Zanthoxylum sprucei (Rutaceae) y Melampodium divaricatum (Asteraceae)

The study of the drying of the plants is important for the extraction methods of the active principles, since it provides benefits both for the efficiency and for the stability. The objective of this research is to study the drying kinetics of the leaves of Zanthoxylum sprucei (Rutaceae) and Melampodium divaricatum (Asteraceae) species from the Manabí province. Eight empirical models derived from Fick's law with adjustment and the STATISTICA software as modeler was used. The model was made by applying the ORIGIN Pro fit curve. The kinetic results were obtained experimentally in a laboratory scale tunnel dryer with a temperature of 40°C, at 1 atm of pressure and a speed air of 8.47 m.s-1. To determine the model that best fits the experimental data, it relies on the correlation coefficient (R2), mean square error (ERMS) and chi-square (X2). The mathematical model that best describes the drying process is the logarithmic for Zanthoxylum sprucei and the Wang and Singh model for Melampodium divaricatum.

Oxidation state of iron and Fe-Mg partitioning between olivine and basaltic martian melts

AbstractWe performed a series of experiments at 1 atm pressure and temperatures of 1300–1500 °C to determine the effect of oxygen fugacity on the oxidation state of Fe in a synthetic martian basalt. Ferricferrous ratios were determined on the quenched glasses using Mössbauer spectroscopy. Following the conventional doublet assignments in the spectrum, we obtain a Fe3+/ΣFe value of 0.19 at 1450 °C and an oxygen fugacity corresponding to the QFM buffer. If we apply the Berry et al. (2018) assignments the calculated Fe3+/ΣFe drops to 0.09, and the slope of log(XFeO1.5melt/XFeOmelt) vs. log(fO2) changes from 0.18 to 0.26.Combining oxidation state data together with results of one additional olivine-bearing experiment to determine the appropriate value(s) for the olivine (Ol)-liquid (liq) exchange coefficient, KD,Fe2+-Mg = (FeO/MgO)Ol/(FeO/MgO)liq (by weight), suggests a KD,Fe2+-Mg of 0.388 ± 0.006 (uncertainty is one median absolute deviation) using the traditional interpretation of Mössbauer spectroscopy and a value of 0.345 ± 0.005 following the Mössbauer spectra approach of Berry et al. (2018).We used our value of KD,Fe2+-Mg to test whether any of the olivine-bearing shergottites represent liquids. For each meteorite, we assumed a liquid composition equal to that of the bulk and then compared that liquid to the most Mg-rich olivine reported. Applying a KD,Fe2+-Mg of ~0.36 leads to the possibility that bulk Yamato 980459, NWA 5789, NWA 2990, Tissint, and EETA 79001 (lithology A) represent liquids.

Short‐term hypobaric treatment enhances chilling tolerance in peaches

Peach fruit quickly shows symptoms of chilling injury (CI) during shelf life after storage under inadequate temperatures. We found that short-term hypobaric treatment (SHT) was effective in reducing the CI index to maintain the quality of peaches (Prunus persica L. Batsch cv. Yingshuanghong) during shelf life after cold storage. The respiration rate of peaches was inhibited, and the climacteric peak was delayed during storage after being treated at 0.45 atm pressures for 4 hr at 20°C. Meanwhile, SHT fruits maintained higher disaccharide concentrations and lower monosaccharide concentrations. SHT fruits also exhibited higher antioxidant enzyme activity that likely reduced the production of ROS. In addition, SHT suppressed membrane oxidation effectively by inhibiting phospholipase D (PLD) and lipoxygenase (LOX) activity to prevent malondialdehyde (MDA) accumulation. These results indicated that SHT performed effectively to alleviate CI in peaches by modulating respiration and sugars metabolism, oxidative stress, and membrane oxidation. Practical applications Unlike hypobaric storage for long periods of time, short-term hypobaric treatment (SHT) is a short-term application of subatmospheric pressure. This paper suggests that SHT is an effective method to alleviate CI and to maintain quality of peaches after cold storage. This work will help to expand chilling-sensitive fruit storage life to satisfy market and consumer demands.

Efficient CO2 Separation Using a PIM‐PI‐Functionalized UiO‐66 MOF Incorporated Mixed Matrix Membrane in a PIM‐PI‐1 Polymer

AbstractMetal–organic framework (MOF) incorporated mixed–matrix membranes (MMMs) attract great interest for gas separation applications because they overcome limitations faced by typical polymer membranes, including permeability–selectivity trade‐off, aging effect, and plasticization phenomenon. However, optimal MOF–polymer interface compatibility is the key challenge in fabricating defect‐free high‐performance gas‐separation MMMs. Here, a surface modification strategy of the UiO‐66‐NH2 MOF using a covalently bound PIM‐PI‐oligomer is developed to engineer interface compatibility with the polymer that has an identical chemical structure (PIM‐PI‐1) in the MMMs. A series of MMMs are prepared with different loadings of homogeneously distributed PIM‐PI‐functionalized MOFs (PPM). Significant improvements in CO2/N2 and CO2/CH4 selectivity and permeability are achieved with these MMMs, ranging from 5 to 10 wt% of the PPM loadings. The MMM with 10 wt% loading (PPM‐10@MMM) shows a CO2 permeability of 3827.3 Barrer and a CO2/N2 and CO2/CH4 selectivity of 24 and 13.4, respectively. This surpasses the 2008 Robeson upper bound for CO2/N2 and is very close to the 2008 upper bound for CO2/CH4. The experimental results are further compared using Maxwell's equation for MMMs. The resulting MMMs show a plasticization resistance against CO2 up to 25 atm pressure and anti‐aging performance for 180 h.

Development of convolutional neural networks for an electron-tracking Compton camera

Abstract The Electron-Tracking Compton Camera (ETCC), which is a complete Compton camera that tracks Compton scattering electrons with a gas micro time projection chamber, is expected to open up MeV gamma-ray astronomy. The technical challenge for achieving several degrees of the point-spread function is precise determination of the electron recoil direction and the scattering position from track images. We attempted to reconstruct these parameters using convolutional neural networks. Two network models were designed to predict the recoil direction and the scattering position. These models marked 41$^\circ$ of angular resolution and 2.1 mm of position resolution for 75 keV electron simulation data in argon-based gas at 2 atm pressure. In addition, the point-spread function of the ETCC was improved to 15$^\circ$ from 22$^\circ$ for experimental data from a 662 keV gamma-ray source. The performance greatly surpassed that using traditional analysis.

Substituent Effects on Electride Characteristics of Mg2(η5-C5H5)2: A Theoretical Study.

An ab initio study has been carried out on the substituted binuclear sandwich complexes of Mg2(η5-C5H5)2. We have checked whether the substitution destroys the electride properties of a complex, as it needs to satisfy several stringent criteria to obtain the status of an electride. The thermochemical results show that the complexes are stable at room temperature and 1 atm pressure. From the analysis of the various electron density descriptors and the natural bond orbital (NBO) for all the complexes, it is confirmed that the Mg-Mg bonds are covalent and the metal-ligand bonds are ionic in nature. The charges on each Mg atom in the studied complexes are +1. Analysis of the electron density descriptors shows the presence of a non-nuclear attractor (NNA) at the middle of the bond formed by the two Mg atoms when attached to the ligands. The electride characteristics are exhibited by all of the designed complexes. We also report the aromaticity behavior and reactivity descriptors of these complexes. The electride characteristics of Mg2(η5-C5H5)2 complex get affected on substitution, as both the NNA population and the nonlinear optical properties (NLO) of the complexes are changed.

Study of Fischer–Tropsch-type reactions on chondritic meteorites

Context.How simple organic matter appeared on Earth and the processes by which it transformed into more evolved organic compounds, which ultimately led to the emergence of life, is still an open topic. Different scenarios have been proposed, the main one assumes that simple organic compounds were synthesized, either in the gas phase or on the surfaces of dust grains, during the process of star formation and they were incorporated into larger bodies in the protoplanetary disk. The transformation of these simple organic compounds in more complex forms is still a matter of debate. Recent discoveries have pointed to catalytic properties of dust grains present in the early stellar envelope, which can nowadays be found in the form of chondrites. The significant infall of chondritic meteorites during the early periods of Earth suggests that the same reactions could have taken place in certain environments on the Earth’s surface, with conditions more favorable for organic synthesis.Aims.This work attempts to synthesize simple organic molecules, such as hydrocarbons and alcohols via Fischer–Tropsch-type reactions supported by different chondritic materials under early-Earth conditions, to investigate if organic synthesis can likely occur in this environment and to determine what the differences are in selectivity when using different types of chondrites.Methods.Fischer–Tropsch-type reactions are investigated from mixtures of CO and H2at 1 atm of pressure on the surfaces of different chondritic samples. The different products obtained are analyzed in situ by gas chromatography.Results.Different Fischer–Tropsch reaction products are obtained in quantitative amounts. The formation of alkanes and alkenes being the main processes. The formation of alcohols also takes place in a smaller amount. Other secondary products were obtained in a qualitative way.Conclusions.Chondritic material surfaces have been proven as good supports for the occurrence of organic synthesis. Under certain circumstances during the formation of Earth, they could have produced a suitable environment for these reactions to occur.