N2 Pressure Research Articles

Catalytic transfer hydrogenation of biomass-derived levulinic acid to γ-valerolactone over Sn/Al-SBA-15 catalysts

The synthesized inexpensive catalysts show high catalytic transfer hydrogenation activity at ambient N2 pressure under non-corrosive conditions. The Sn/Al-SBA-15 (25) catalyst exhibited the highest catalytic activity with 99% conversion of levulinic acid and 100% selectivity towards GVL.

Microporosity of a Guanidinium Organodisulfonate Hydrogen‐Bonded Framework

AbstractGuanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate (p‐G2BDS). p‐G2BDS is obtained from its acetone solvate, AcMe@G2BDS, by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N2 sorption isotherm (SABET=408.7(2) m2 g−1, 77 K). SC‐SC sorption of N2, CO2, Xe, and AcMe by p‐G2BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO2 sorption isotherms. Though p‐G2BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np‐G2BDS, a sample of p‐G2BDS survived for almost two decades under ambient conditions. np‐G2BDS reverts to zCO2@p‐G2BDS or yXe@p‐G2BDS (y,z=variable) when pressure of CO2 or Xe, respectively, is applied.

Morphological design of complex oxides during pulsed-laser deposition: The role of plasma-plume expansion

Complex oxides such as tin-doped indium oxide (ITO) are widely utilized as transparent conductors in a variety of functional devices. Typically, they are fabricated by sputtering, which often requires additional annealing to achieve high transparency and conductivity. Using pulsed laser deposition (PLD), both high transparency and high conductivity have been achieved without annealing, using instead selected gas species and pressures. However, the relative roles of Stranski-Krastanov-like and vapor-liquid-solid (VLS) growth modes during morphological transitions remain controversial. Here, we report on PLD of ITO in an inert-gas environment, identifying the role of plasma-plume expansion in the selection of VLS vs vapor-solid (VS) growth. For the lowest N2 pressure, indium-tin droplet formation, followed by self-catalyzed VLS growth, is observed. With increasing N2 pressure, a transition from VLS to VS growth is apparent. It is hypothesized that oxygen scattering at the lowest N2 pressure induces a metal-rich plume, which leads to metal droplet formation, followed by VLS growth. As the N2 pressure is increased, the plasma-plume and its metal-rich core are compressed, resulting in a transition to VS growth. This tunable compression of the plasma-plume offers a route to the morphological design of a wide range of functional complex oxide devices with tunable optical and electronic performance.

Habitable Zone Boundaries for Circumbinary Planets

We use a one-dimensional (1D) cloud-free climate model to estimate habitable zone (HZ) boundaries for terrestrial planets of masses 0.1 ME and 5 ME around circumbinary stars of various spectral type combinations. Specifically, we consider binary systems with host spectral types F-F, F-G, F-K, F-M, G-G, G-K, G-M, K-K, K-M and M-M. Scaling the background N2 atmospheric pressure with the radius of the planet, we find that the inner edge of the HZ moves inwards toward the star for 5 ME compared to 0.1 ME planets for all spectral types. This is because the water-vapor column depth is smaller for larger planets and higher temperatures are needed before water vapor completely dominates the outgoing longwave radiation. The outer edge of the HZ changes little due to competing effects of the albedo and greenhouse effect. While these results are broadly consistent with the trend of single star HZ results for different mass planets, there are significant differences between single star and binary star systems for the inner edge of the HZ. Interesting combinations of stellar pairs from our 1D model results can be used to explore for in-depth climate studies with 3D climate models. We identify a common HZ stellar flux domain for all circumbinary spectral types.

Interaction of Plasma Jet With Methanol as Fundamental Processes in Solution

Plasma depollution is a relatively new field that investigates potential applications of atmospheric pressure plasma in environmental engineering, such as microorganism inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of degradation of organic matter at molecular or atomic levels, the interaction between He, N2, O2, and air plasma jet and methanol in water was analyzed by gas chromatography–mass spectrum and Fourier transform infrared spectroscopy. Results show that the efficiency of methanol degradation is strongly dependent on the working gas and plasma treatment time. Compared to atmospheric pressure N2, O2, and air plasma jet, the He plasma jet may be utilized to degrade methanol more efficiently in aqueous solution. The efficiencies of degradation of methanol in water can be well described by using the chemical reaction rate model, where reactive oxygen and hydroxyl radical species play crucial roles in the degradation process. This paper provides an insight into the mechanism of degradation of organic pollutant in water by plasma.

Temperature and Pressure Dependent Kinetics of QOOH Decomposition and Reaction with O2: Experimental and Theoretical Investigations of QOOH Radicals Derived from Cl + (CH3)3COOH

QOOH radicals are key species in autoignition, produced by internal isomerizations of RO2 radicals, and are central to chain branching reactions in low-temperature combustion. The kinetics of QOOH radical decomposition and reaction with O2 have been determined as a function of temperature and pressure, using observations of OH radical production and decay following H-atom abstraction from t-butyl hydroperoxide ((CH3)3COOH) by Cl atoms to produce QOOH (CH2(CH3)2COOH) radicals. The kinetics of QOOH decomposition have been investigated as a function of temperature (251-298 K) and pressure (10-350 Torr) in helium and nitrogen bath gases, and those of the reaction between QOOH and O2 have been investigated as a function of temperature (251-304 K) and pressure (10-100 Torr) in He and N2. Decomposition of the QOOH radical was observed to display temperature and pressure dependence, with a barrier height for the decomposition of (44.7 ± 4.0) kJ mol-1 determined by master equation fitting to the experimental data. The rate coefficient for the reaction between QOOH and O2 was determined to be (5.6 ± 1.7) × 10-13 cm3 s-1 at 298 K, with no significant dependence on pressure, and can be described by the Arrhenius parameters A = (7.3 ± 6.8) × 10-14 cm3 s-1 and Ea = -(5.4 ± 2.1) kJ mol-1 in the temperature range of 251-304 K. This work represents the first measurements of any QOOH radical kinetics as a function of temperature and pressure.

Selective Catalytic Transfer Hydrogenolysis of Glycerol to 2-Isopropoxy-Propan-1-Ol over Noble Metal Ion-Exchanged Mordenite Zeolite

This study investigated the selective conversion of glycerol to 2-isopropoxy-propan-1-ol over noble metal ion-exchanged mordenite zeolites (RuMOR, RhMOR, and PdMOR) as heterogeneous catalysts via catalytic transfer hydrogenolysis (CTH) using propan-2-ol as the solvent, hydrogen supplier, and reactive coupling reagent with glycerol. The catalytic reactions were performed at 140 °C under inert conditions with a 0.5 MPa initial pressure of N2. A single product, 2-isopropoxy-propan-1-ol, was catalytically generated without any appreciable by-products. The catalytic results were reproducible, and the catalysts exhibited good recyclability.

N2 and H2 broadened isobutane infrared absorption cross sections and butane upper limits on Titan

High resolution infrared absorption cross sections of isobutane, (CH3)3CH, were measured in the 1050–1900 cm−1 spectral range by Fourier transform spectroscopy. Four sample temperatures (210, 234, 265 and 296 K) were used with three pressures (10, 30 and 100 Torr) of N2 and H2 broadening gas. Spectra of pure isobutane samples were also recorded. These cross sections are useful for the interpretation of infrared spectra of the Giant Planets and Titan. The isobutane cross sections give an upper limit of 3.91e-8 for its fractional abundance on Titan based on CIRS/Cassini infrared spectra. Using n-butane, CH3(CH2)2CH3, cross sections from the literature, we obtain an upper limit of 5.13e-7 for its abundance on Titan. The combined upper limit for both isomers of butane, C4H10, on Titan of 5.52e-7 is consistent with the lower limit of recent model predictions.

Hydroxylamine Oxidation on Polycrystalline Gold Electrodes in Aqueous Electrolytes: Quantitative On‐Line Mass Spectrometry under Forced Convection

Herein, a method is presented that allows quantitative determination of faradaic efficiencies for dinitrogen (N2 ) generation during the electrochemical oxidation of hydroxylamine (NH2 OH), , on a polycrystalline gold Au(poly) disk electrode in aqueous electrolytes over a wide pH range. This tactic involves the use of an impinging jet electrolyte configuration incorporating a gas porous ring connected in turn to a mass spectrometer. The actual amount of N2 generated at the Au(poly) disk was assayed using the oxidation of hydrazine (N2 H4 ) in aqueous phosphate buffer (pH 7). This redox process yields N2 as the only product, allowing a direct correlation to be established between the changes in the partial pressures of N2 and the current flowing through the disk electrode. An analysis of the data collected revealed a strong dependence of both on pH and the applied potential. Although values of as high as 20 to 30 % were found in acid and neutral media over a narrow potential region, those in alkaline solution were far smaller in the entire potential range examined.

Effect of vibrationally excited N2(v) on atomic nitrogen generation using two consecutive pulse corona discharges under atmospheric pressure N2

Herein, we report on experimental results showing that vibrationally excited N2(v) plays an important role in producing nitrogen atoms in successive two-pulsed corona discharges. To investigate the effect of vibrationally excited N2(v) on the generation of atomic nitrogen, two pulses were generated such that their pulse intervals could be varied in a controlled manner. The resulting nitrogen atoms were measured using TALIF under atmospheric pressure N2 at different time points after each pulse. Firstly, the effect of pulse-to-pulse intervals (Δt) on the streamer formation of the second pulse discharge was observed. The results suggest that a decrease of Δt cause a reduction in the consumption of energy and inhibit streamer formation and propagation of a second pulse discharge. The energy efficiency of atomic nitrogen generation in the second pulse discharge near the anode tip was a maximum of approximately three times that of the first pulse. This efficiency decreases with increasing Δt and eventually became approximately equivalent to the value of the first pulse within Δt = 300 µs. This behavior is correlated with the temporal profile of the vibrational temperature after pulse discharge, which indicates that vibrationally excited N2(v) generated by the first pulse discharge plays a significant role in atomic nitrogen generation in the second pulse. The local densities of atomic nitrogen in the streamer channel for the first and second pulse discharges were estimated from their decay rate. The results suggest that the second pulse discharge generates atomic nitrogen while maintaining the local density of the first discharge pulse in the streamer channel, irrespective of Δt. Moreover, it indicates that the main generation region of atomic nitrogen in the second pulse discharge is different from that of the first pulse, although the second pulse discharge uses vibrationally excited N2(v) to generate atomic nitrogen.

ANTICORROSIVE PROPERTIES OF CHROMIUM COATINGS ON AISI H13 STEEL BY GASEOUS NITRIDING IN VACUUM

This paper shows the results of this process through the performance of a duplex treatment that combines the application a single chromium hard coating Cr(VI) on a AISI H13 steel with a thermochemical treatment of vacuum gas nitriding. The thickness of the electroplated coating was 15 μm, and N2 was used as precursor gas, with a flow of 100 ml/min at a pressure of 1.2 kPa to produce a CrxNy coating. The existing phases were determined by means of X-ray diffraction, and the corrosion resistance was evaluated via potentiodynamic polarization and electrochemical impedance spectroscopy techniques in a three-electrode electrochemical cell. Characterization via XRD determined the presence of chromium nitrides of type Cr2N, with an important orientation along the plane (300) associated with the partial pressure of N2 and the thermodynamic behavior. The corrosion resistance results showed a significant decrease in the corrosion current density compared with those exhibited by samples chromed by electroplating with AISI H13 steel without nitriding. These results, coupled with the sealing of characteristic microcracks of the electroplated chrome coating, could improve the corrosion resistance, because of the existence of the CrxNy phase.

Opportunities for Electrochemical and Catalytic Processes That Support Human Activity on Mars

Supporting human activity on Mars requires working with available resources, which include low-pressure CO2 (P CO2 » 5.8 mbar) even lower pressure N2 (P N2 » 0.12 mbar), sub-surface ice, and solar insolation (up to 300 W/m2 at the surface). Supporting life on Mars requires sustained production of O2, liquid H2O, food, heat, and fuel for rockets and mobility. This presentation explores electrochemical and chemical processes based on catalytic membrane reactors that can enable production of value-added products and/or their precursors from the in-situ resources. Many practical chemical technologies require H2 as a feedstock, which can be produced by steam electrolysis that also produces O2. An attractive approach to electrolysis uses proton-conducting ceramic membrane such as (BCZYYb) at intermediate temperatures (between 450 and 650 °C) [1-3]. Proton-conducting ceramics electrochemical cells (PCEC) provide advantages compared to liquid-based polymer electrolyte membrane electrolysis in that they can operate without the need for high-purity liquid H2O and they can incorporate carbonaceous feedstocks for combining electrolysis with other chemistries. In addition to producing H2, the electrolysis cell can be operated as an integrated H2 electrochemical compressor. Several viable catalytic hydrogenation processes can react H2 from the electrolysis cell with CO2 to produce fuels and chemicals. The Sabatier reaction for producing CH4 from CO2 and electrolysis derived H2 has been well studied with an optimal operating temperature around 400 °C [4]. More selective catalysts and novel membrane reactors can be developed to produce valuable fuels and chemicals that include methanol, ethylene, dimethyl ether, formic acid, etc. The desired product streams depend on selective catalysts and on operating pressures and temperature. In some cases, process performance may depend on the development of novel bi-functional catalysts and/or selective membranes. In addition to carbon-based products, applications such as fertilizers need ammonia. Available N2 in the atmosphere could react with H2 to synthesize NH3 via Haber-Bosch process. Many of these relevant catalytic processes require high pressure (at least tens of bar) and modest elevated temperature (300-500 ˚C). Depending on the product yield, downstream separations and purifications may be needed. Assuming limited space and need to high efficiency, process intensification [5] will likely play important roles in the development of in-situ resource utilization. This paper explores the opportunities and challenges for developing critical electrochemical processes for production of a variety of chemicals to support future human Martian activity. Fig.1. Cartoon illustration of a H2 membrane coupled catalytic reactor for CO2 hydrogenation to chemicals References C. Duan, J. Tong, M. Shang, S. Nikodemski, M. Sanders, S. Ricote, A. Almansoori, and R. O’Hayre. Science, 349:1321–1326, 2015.H. Zhu, S. Ricote, C. Duan, R.P. O’Hayre, and R.J. Kee. J. Electrochem. Soc., 165:F845–F853, 2018.C. Duan, R.J. Kee, H. Zhu, N. Sullivan, L. Zhu, L. Bian, D. Jennings, and R.P. OHayre. Nature Energy, 4:230240, 2019.K.P. Brooks, J. Hu, H. Zhu, R.J. Kee, “Methanation of carbon dioxide by hydrogen reduction using the Sabatier process in microchannel reactors”, Chem. Eng. Sci., 62(4):1161-1170, 2007.R.J. Kee, C. Karakaya, H. Zhu, “Process intensification in the catalytic conversion of natural gas to fuels and chemicals,” Proc. Combust. Inst., 36:51–76, 2017 Figure 1

Molecular simulation of flue gas and CH4 competitive adsorption in dry and wet coal

For further understanding the microcosmic mechanism of CO2 storage and CH4 recovery during coal-fired power plants flue gas injecting into the coal seams, the dry and wet macromolecular models of coal were established. Then Grand Canonical Monte Carlo (GCMC) molecular simulations were performed to state multicomponent (single, binary, ternary and quaternary systems among flue gas and CH4) and competitive adsorption behaviors. The results show that the adsorption amount of individual gas in the mixed components adsorption systems increases with the pressures and bulk mole fractions increasing. While the advantages of selective separation for competitive ones, especially for CO2, decrease. The order of adsorption amount of gases in the mixture depends on not only adsorption ability but also bulk mole fraction. With the same bulk mole fraction of CH4, the selectivities of CO2/CH4 that in the systems injecting flue gas are larger than that injecting pure CO2. With the same 0.99 mmol/g adsorption amount of CO2, injection of flue gas is more beneficial to desorption of CH4 than injection of CO2 due to the large partial pressure of N2. The advantages of competitive adsorption for CO2 can be explained by stronger favorable adsorption sites therefore stronger van der Waals energy and electrostatic energy between CO2 and coal. Water in coal goes against the gases adsorption, especially for CO2, because the preferential adsorption sites are occupied by water. The conclusions of this research lay a theoretical foundation for the application of flue gas-ECBM technology.

Combustion synthesis of MgSiN2 powders and Si3N4‐MgSiN2 composite powders: Effects of processing parameters

AbstractIn the present work, high‐quality MgSiN2 powders were prepared by a combustion synthesis method, based on Mg‐Si3N4‐N2 system. The effects of additive content (NH4Cl or NH4F) and N2 pressure on phase composition and crystal morphology of products were investigated. The results suggested that both NH4Cl and NH4F additives alleviated agglomeration and decreased the grain size of MgSiN2. In addition, NH4Cl did not result in the formation of an extra impurity, while MgF2 residue was found when NH4F was introduced. Therefore, NH4Cl additive was considered as a better choice for the preparation of MgSiN2 powders in comparison with NH4F additive. According to the observation of some MgSiN2 whiskers and notably increased Si content under low N2 pressure, the pressure of N2 over 0.5 MPa was essential to have a complete reaction in the present work. Finally, MgSiN2‐Si3N4 composite powders with quasi‐spherical morphology were prepared by adding excessive Si3N4 and NH4Cl additive in reactant. The formation and growth mechanism of MgSiN2 grains was reasonably speculated based on the experimental results. Because of the remarkable merits, the as‐prepared Si3N4‐MgSiN2 composite powders showed great potential for alternative sintering aid in the sintering of Si3N4‐based ceramics.

Preparation and crystal structure of ζ-Cr2(C,N) powders

In this work, the influence parameters, including synthesis temperature, nitrogen pressure, and isothermal dwell time, were systematically investigated during carbothermal preparation of ζ-Cr2(C,N) solid solution powders by using thermogravimetry differential scanning calorimetry, X-ray diffraction, scanning electron microscope, and composition analysis. The results showed that Cr2O3 began to be carbonized at ~ 1000 °C firstly and then was nitrided with the formation of Cr2(C,N) at elevated temperature, and finally ζ-phase Cr2(C,N) particles were obtained at the optimal condition of 1200 °C for 1 h under the N2 pressure of 0.02 MPa, which showed lowest oxygen (0.82 wt%) and highest nitrogen (6.25 wt%) content with the diameter of ~ 3 μm. Increasing temperature, N2 pressure, and dwell time facilitates the reduction of oxygen. However, these parameters must be carefully controlled under reasonable ranges to preventing quality deterioration. In addition, the crystal structure of ζ-Cr2(C,N) was characterized by transmission electron microscope and neutron powder diffraction (NPD). Based on the selected area diffraction and NPD patterns, the crystal structure of Cr2(C,N), prepared in this work, was confirmed to be orthorhombic (Pbcn) as well as the interstitial atoms (C and N) were ζ-type occupational ordering.

In situ surface formation of TiO2/Ti(NO2) hybrid nanocomposites with N2 APPJ treatment for efficient C2H4 photodegradation.

TiO2/Ti(NO2) hybrid films were prepared using N2 atmospheric pressure plasma jet treatment on TiO2 coating. The film structure and morphology have been investigated using optical emission spectra, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The formed TiO2/Ti(NO2) photocatalystic thin films were applied for C2H4 photodegradation under UV irradiation. The results showed that the composite films exhibited superior photocatalytic activity over the untreated TiO2 film. The C2H4 concentration after 120min varied from 12 to 6.2mg/L, 6.7mg/L, 7mg/L for TiO2 with 1min, 2min and 3min plasma treatment, respectively. In the banana storage experiment, the concentration of C2H4 was reduced from 15 to 9ppm after 36h with TiO2/Ti(NO2) nanocomposite film illuminated by UV light. The photocatalytic mechanism has been discussed. The composite film is able to more effectively separate the photo-excited electrons and holes, thus leading to the much high activity in C2H4 degradation. The current work has paved a way towards postharvest fruit preservation.

Preparation of novel cross-linked graphene oxide membrane for desalination applications using (EDC and NHS)-activated graphene oxide and PEI

A novel cross-linked graphene oxide (GO) membrane was prepared by vacuum filtration using a two-step method, including activation of GO carboxyl groups by a mixture of 1-Ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC) and N -Hydroxysuccinimide (NHS) and then cross-linking with polyethyleneimine (PEI). In the cross-linking process, the activated carboxyl groups of GO react with amine groups of PEI through a simple and efficient method. GO cross-linking with PEI significantly improves membrane dimensional stability and salt rejection. The rejection of the cross-linked GO membrane was evaluated by NaCl, Na2SO4 and MgCl2 solutions, and the obtained results followed the order of R (MgCl2) > R (NaCl) > R (Na2SO4). The prepared cross-linked GO membrane was characterized by FTIR, XRD, SEM, FESEM, EDS, WCA, AFM and BET analysis. Also, the effects of operating parameters such as N2 pressure, feed temperature and pH on the cross-linked GO membrane performance were investigated.

Optimization of Titanium Nitride Film for High Power RF MEMS Applications

In this paper, TiN film has been deposited and optimized at room temperature for high power radio-frequency microelectromechanical system (RF-MEMS) applications. Being hard, titanium nitride is used in the contact area. The contact material should have low resistance and high hardness. TiN thin films were deposited by DC magnetron reactive sputtering using a four inch high purity titanium target in a nitrogen (N2) environment. X-ray diffraction (XRD) analysis is used to confirm crystal structure and purity of TiN film. The effect of various N2 pressure on resistivity and hardness of TiN thin film is investigated. The resistivity of the film decreases and hardness increases with N2 pressure.

PtII -Catalyzed Hydroxylation of Terminal Aliphatic C(sp3 )-H Bonds with Molecular Oxygen.

The practical application of Shilov-type Pt catalysis to the selective hydroxylation of terminal aliphatic C-H bonds remains a formidable challenge, due to difficulties in replacing PtIV with a more economically viable oxidant, particularly O2 . We report the potential of employing FeCl2 as a suitable redox mediator to overcome the kinetic hurdles related to the direct use of O2 in the Pt reoxidation. For the selective conversion of butyric acid to γ-hydroxybutyric acid (GHB), a significantly enhanced catalyst activity and stability (turnover numbers (TON)>30) were achieved under 20 bar O2 in comparison to current state-of-the-art systems (TON<10). In this regard, essential reaction parameters affecting the overall activity were identified, along with specific additives to attain catalyst stability at longer reaction times. Notably, deactivation by reduction to Pt0 was prevented by the addition of monodentate pyridine derivatives, such as 2-fluoropyridine, but also by introducing varying partial pressures of N2 in the gaseous atmosphere. Finally, stability tests revealed the involvement of PtII and FeCl2 in catalyzing the non-selective overoxidation of GHB. Accordingly, in situ esterification with boric acid proved to be a suitable strategy to maintain enhanced selectivities at much higher conversions (TON>60). Altogether, a useful catalytic system for the selective hydroxylation of primary aliphatic C-H bonds with O2 is presented.

Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N2 gas-passing, electrical conductivity enhances significantly. Therefore, N2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.