Catalytically Modified Pt/Catalysed TiO_2/SiC Devices for Hydrogen and Hydrocarbon Gas Sensing

In this paper the hydrogen and hydrocarbon gas sensing performance of the Pt/Catalysed TiO_2/SiC devices have been studied.The TiO_2 metal oxide thin films were catalytically modified employing Pt and Pd.The electrical properties of the fabricated devices were studied by measuring their capacitance-voltage (C-V),conductance-voltage (G-V) and dynamic response characteristics.The sensor's response as a function of operating temperature (25℃to 700℃) and concentrations less than 1% of the analyte gases have been investigated.The sensitivity of the Pt catalysed TiO_2 sensor was found to be superior when compared to TiO_2 catalysed with Pd.A voltage shift of 3.2 V for 1% propene at 420℃and 2.8 V for 1% hydrogen at 250℃in an ambient containing synthetic air was recorded for the Pt catalysed TiO_2 sensor.The response of Pt catalysed TiO_2 sensor was found to be approximately 4 times larger when compared to the non catalysed counterpart.

Tin stearate organometallic precursor prepared SnO_2 quantum dots nanopowder for aqueous- and non-aqueous medium photocatalytic hydrogen gas evolution

Current study reports a rapid one-pot non-hydrolytic condition in the synthesis of Sn O2QDs nanopowder using tin(II) stearate(Sn(St)2) as environmentally-benign organometallic precursor,which is an unprecedentedly employed-compound in preceding Sn O2nanopowder productions.The as-synthesized Sn O2QDs that are hydrophobic can be easily transferred from organic solvent to aqueous solution through a robust ligand exchange method.The stearate-capping ligands on the surface of QDs can be replaced by beta-cyclodextrin(β-CD) and eventually render the QDs highly water soluble,which ultimately make it exhibit bi-functionality for different liquid medium applications.Structural characterizations reveal that the bi-functional QDs are indeed well-matched with the standard rutile Sn O2cassiterite phase without the presence of any impurities.The QDs can be interchangeably used as photocatalyst for both aqueous and non-aqueous phase,where it shows significant enhancement of hydrogen gas production as compared to that of commercial Sn O2nanopowder.

2-Ethyl-9,10-anthraquinone assisted sol–gel synthesis of Pd/γ-Al2O3 nanorods with enhanced catalytic performance in 2-ethyl-9,10-anthraquinone hydrogenation

A series of nanorod-like porous Pd/γ-Al2 O3 catalysts with controllable textural properties and enhanced catalytic performance in 2-ethyl-9,10-anthraquinone(eAQ) hydrogenation for H2 O2 preparation were successfully prepared via a facile sol-gel method using aluminum isopropoxide as aluminum precursor and eAQ as structure directing agent,sequential calcination and impregnation process with Na2 PdCl4 solution.The physicochemical properties of the catalysts obtained with different addition amounts of eAQ.were comparatively characterized by XRD,TG-DSC,BET,TEM,CO-TPR,H2-TPR and H2-O2 titration.The results show that addition of eAQ can not only effectively control the textural properties(surface area,pore volume and average pore size) of the catalysts,but also lower their reduction temperature of active metal.Importantly,the catalyst obtained with an addition amount of 4 wt% eAQ shows the highest hydrogenation efficiency of 10.28 g·L^-1,which is 37.3% higher than 7.49 g·L^-1 of the catalyst obtained without eAQ.

H_2S Gas Sensitivity of Nanocrystalline Tin Dioxide Doped with Ytterbium (Yb) and Praseodymium (Pr)

<正>The influence of Yb_2O_3 and Pr_2O_3 doping on electrical and gas sensing properties of tin dioxide was studied.A doping content of 0.5wt%～5wt% was investigated by mechanical mixing.The significant improvement on sensitivity and selectivity to 200μg/g hydrogen sulphide gas has been achieved by 3wt% Pr_2O_3 and 5wt% Yb_2O_3 adding.The better response and revovery properties of Pr or Yb doped tin dioxide sensor for 200μg/g hydrogen sulphide gas were found.The maximum sensitivity to H_2S gas is observed at about 120℃.Pr has stronger catalysis than Yb for H_2S reaction on SnO_2 surface.S~ 2-) was oxidized to S~ 6+) on the SnO_2 surface according to XPS.

Hydrogen and Ozone SAW Based Gas Sensors with RF Magnetron Sputtered InO_x and Electron Beam Evaporated SiN_y

Layered Surface Acoustic Wave (SAW) devices with an InO_x/SiN_u/36°YX LiTaO_3 structure were investigated for sensing low concentrations of hydrogen (H_2) and ozone (O_3) at different operating temperatures.The sensor consists of a 1μm thick silicon nitride (SiN_y) intermediate layer deposited by electron beam evaporation on a 36°Y-cut X-propagating piezoelectric lithium tantalate (LiTaO_3) substrate and a 100 nm thin indium oxide (InO_x) sensing layer deposited by R.F.magnetron sputtering.The device fabrication is described and the performance of the sensor is analyzed in terms of response magnitude as a function of operating temperature.Large frequency shifts of 360 kHz for 600μg/g of H_2 and 92 kHz for 40 ng/g O_3 were recorded.In addition,the surface morphology of the deposited films were investigated by Atomic Force Microscopy (AFM) and the chemical composition by X-Ray Photoelectron Spectroscopy (XPS) to correlate gas-sensing behavior to structural characteristics of the thin film.

Theoretical Studies on the Stabilities and Hydrogen Bond Actions of (H_2O)_n Clusters

The stable configurations and hydrogen bond nature of （H2O）n clusters （n = 3-6） have been investigated by the B3LYP method at the 6-31＋＋g^＊＊ level. Upon calculation, four conclusions have been drawn： （1） In the （H2O）3-5 clusters, cyclic configurations were confirmed to be the most stable. But in the （H2O）3-4 ones, only cyclic configurations could be observed. From n = 5 （（H2O）5 clusters）, three-dimensional configuration could be found： （2） In the （H2O）6 clusters, all configurations are inclined to be three-dimensional except the most stable configuration which is cyclic; （3） The stable order of （H2O）6 clusters indicates that it is the arrangement of hydrogen bond that plays a decisive role in the cluster stabilities, the zero-point energy is also important, and cluster stabilities are independent on the number of hydrogen bonds; （4） There exist strong cooperativity and superadditivity in the （H2O）n clusters.

Corrosion Rate of Hydrogenation to C110 Casing in High H_2S Environment

The corrosion behavior of C110 bushing at high temperature and high pressure with a high H2S / CO2 was studied, and a basis for the materials selection of sour gas well bushing was provided in H2S, CO2 and saline coexisting environment. Under acidic condiction, hydrogen atoms greatly entered into the material and caused the material properties changed. Weight loss method was used to study the corrosion rate of hydrogen charging samples and original untreated samples in simulated oil field environment. PAR2273 electrochemical workstation was used to examine the electrochemical performance of samples untreated, hydrogen charging after reacting in autoclave. The corrosion product film was observed through SEM. The experimental results show that sample with hydrogen charging has a much more obvious partial corrosion and pitting corrosion than the untreated blank sample even the downhole corrosion speed of bushing is increased after being used for a period of time. Polarization curve shows the corrosion tendency is the same between sample with or without hydrogen charging and corrosion tendency is reduced by corrosion product film. A layer of dense product film formed on the surface of samples provides a certain protective effect to the matrix, but cracked holes which will accelerate partial corrosion of the sample were also observed.

Zinc Oxide Nanostructure Thick Films as H₂S Gas Sensors at Room Temperature

The ZnO nanostructures have been synthesized and studied as the sensing element for the detection of H2S. The ZnO nanostructures were synthesized by hydrothermal method followed by sonication for different interval of time i.e. 30, 60, 90 and 120 min. By using screen printing method, thick films of synthesized ZnO nanostructure were deposited on glass substrate. Gas sensing properties of ZnO nanostructure thick films were studied for low concentration H2S gas at room temperature. The effects of morphology of synthesized ZnO nanostructure on gas sensing properties were studied and discussed. ZnO nanostructure synthesized by this method can be used as a promising material for semiconductor gas sensor to detect poisonous gas like H2S at room temperature with high sensitivity and selectivity.

The Effect of Pressure on the Dissociation of H_2/CH_4Gas Mixture during Diamond Films Growth via Chemical Vapor Deposition

Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.

C-H…O Hydrogen Bonds and π…π Interaction and the Crystal and Molecular Structures of 3-Nitro-benzylideneaniline-methyl-2’

The title compound (C14H12N2O2, Mr = 240.26) crystallizes in the monoclinic system, space group P21/a with a = 7.394(1), b = 21.334(3), c = 7.423(1) ? b = 89.82(1)? V = 1170.8(3) ?, Z = 4, Dc = 1.363 g/cm3, m(MoKa) = 0.93 cm-1 and F(000) = 504.00. The final R and wR are 0.0440 and 0.1370 for 2153 observed reflections (I > 2s(I)), respectively. The dihedral angle between the two phenyl rings is 52.9 and that between the NO2 group and its attached ring is 3.0. In the crystal, molecules are stacked along [100] through p…p interactions. The CH…O hydrogen bond (3.403 ? 120.4? laterally connects the stacks along [010] to form networks (001) which are further anti- parallelly connected by CH…O (3.382 ? 142.9) and p…p interactions extending along [001]. Also presented here is a brief study on the CH…O hydrogen bonds in nitro-substituted benzyl-ideneanilines which can be classified into five types, namely, )5(12R, )4(21R, )8(22R, )6(12R and )7(22R, with the first three occurring more often.

Solubility and mass transfer of H2, CH4, and their mixtures in vacuum gas oil: An experimental and modeling study

In this work,the solubility data and liquid-phase mass transfer coefficients of hydrogen(H2),methane(CH4)and their mixtures in vacuum gas oil(VGO)at temperatures(353.15-453.15 K)and pressures(1-7 MPa)were measured,which are necessary for catalytic cracking process simulation and design.The solubility of H2 and CH4 in VGO increases with the increase of pressure,but decreases with the increase of temperature.Henry’s constants of H2 and CH4 follow the relation of In H=-413.05/T+5.27 and In H=-990.67/T+5.87,respectively.The molar fractions of H2 and system pressures at different equilibrium time were measured to estimate the liquid-phase mass transfer coefficients.The results showed that with the increase of pressure,the liquid-phase mass transfer coefficients increase.Furthermore,the solubility of H2 and CH4 in VGO was predicted by the predictive COSMO-RS model,and the predicted values agree well with experimental data.In addition,the gas-liquid equilibrium(GLE)for H2+CH4+VGO system at different feeding gas ratios in volume fraction(i.e.,H285%+CH415%and H290%+CH410%)was measured.The selectivity of H2 to CH4 predicted by the COSMO-RS model agrees well with experimental data.This work provides the basic thermodynamic and dynamic data for fuel oil catalytic cracking processes.

H_2S Gas Sensor Based on Nanocrystalline ZnO Synthesized by Electrochemical-Deposition

ZnO nanocrystals were prepared by a direct current electrochemical deposition process under 3.0V working voltage and 30A/m^2 current density using zinc sulfate as raw materials.The nanocrystals were characterized by X-ray diffraction (XRD)and transmission electron microscopy(TEM).The results indicated that the nanocrystals are hexagonal wurtzite ZnO with particle size range of 25nm～40nm without any treating.Gas sensing properties of the sensors were tested by mixing a gas in air at static state;the tested results showed that the sensors based on nanocrystalline ZnO had satisfied gas sensing properties to H_2S gas at rather low temperature.

Hydrogen Permeation Behaviors of X52 Pipeline Steel in NACE A Solution with Saturated H_2S/CO_2

With the aid of hydrogen permeating devices, the hydrogen permeation behaviors of X52 pipeline steel in NACE A solution with saturated H2S/CO2 were studied under the conditions of different ambient temperatures and pH values, and the hydrogen permeation behaviors of X52 pipeline steel in weld seam zone were comparatively studied. The experimental results show that the hydrogen permeation coefficient value is directly proportional to the time required for reaching the saturation anode current and inversely proportional to the saturation anode current, and the hydrogen permeation coefficient is influenced by the corrosion scales; the temperature is directly proportional to the saturation anode current, and the hydrogen permeation coefficient is influenced by the temperature and corrosion scales, heat-affected zone and matrix zone in NACE A solution with saturated H2S/CO2 at normal temperature. The hydrogen permeation coefficient in weld seam zone is larger than that in heat-affected zone which is further larger than that in matrix zone.

Effects of pretreatment and reduction on the Co/Al_2O_3 catalyst for CO hydrogenation

The purpose of this study was to investigate the effect of preadsorbed CO at different temperatures, calcination temperatures, the combined influence of reduction temperature and time, and pretreatment using hydrogen or syngas as reduction agents on the F-T synthesis （FTS） activity and selectivity of Co/Al2O3 catalyst. The reactivity of the carbon species at higher preadsorption temperature with H2 in TPSR decreased, whereas the carbon-containing species showed higher reactivity over Co/Al2O3 catalyst with low calcination temperature. This agreed well with the order of catalytic activity for F-T synthesis on this catalyst. The catalytic activity of the catalyst varied with reduction temperature and time remarkably. CODEX optimization gave an optimum reduction temperature of 756 K and reduction time of 6.2 h and estimated C5＋ yield perfectly. The pretreatment of Co/Al2O3 catalyst with different reduction agents （hydrogen or syngas） showed important influences on the catalytic performance. A high CO conversion and C5＋ yield were obtained on the catalyst reduced by hydrogen, whereas methane selectivity on the catalyst reduced by syngas was much higher than that on the catalyst reduced by hydrogen.

A Thermoelectric Transducer Based on Bismuth Telluride Thin Films for H_2 Gas Sensing

We have developed a novel thermoelectric gas sensors based on bismuth telluride thin films.These sensors were employed for sensing different concentrations of H_2 gas.Radio frequency (R.F.) magnetron sputtering was employed to deposit the bismuth telluride (Bi_2Te_3) thin films.The morphology of such thin films was investigated and responses of the thermoelectric devices to H_2 were studied.

Structural Characterization of Nanocrystalline La_1-xSr_xCrO₃Thick Films for H₂S Gas Sensors

The nanocrystalline of La1-xSrxCrO3 (x = 0.0, 0.1, 0.2, 0.3 & 0.4) were prepared by sol-gel method and their crystal structures & morphology were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). XRD patterns indicate that the average particle size of the nanocrystalline La0.7Sr0.3CrO3in the range of 30 - 35 nm. The gas sensing properties were studied towards reducing gases like Ammonia gas (NH3), liquefied petroleum gas (LPG), hydrogen sulphide (H2S) and H2 gas and it is observed that undoped LaCrO3 shows response to H2S gas at relatively high operating temperature 300°C. The La1-xSrxCrO3 based sensor with x = 0.3 shows better sensitivity towards H2S gas at an operating temperature 210°C. The effect of Sr doping on sensitivity, response time and recovery time of the sensor in the presence of H2S and other reducing gases were studied and discussed.

Simulation of CO₂and H₂S Removal Using Methanol in Hollow Fiber Membrane Gas Absorber (HFMGA)

Application of methanol solvent for physical absorption of CO2 and H2S from CO2/H2S/CH4 mixture in gas–liquid hollow fiber membrane gas absorber (HFMGA) was investigated. A computational mass transfer (CMT) model for simulation of HFMGA in the case of simultaneous separation of CO2 and H2S was developed. The membrane gas absorber model explicitly calculates for the rates of mass transfer through the membrane and components concentration profiles. Due to the lack of experimental data in the literature, the model was validated using available individual components’ water absorption data. The numerical predictions were in good agreement with the experimental data. The effects of operating conditions such as liquid velocity, gas velocity, temperature and pressure were analyzed. It is shown that methanol solvent can successfully be used for CO2 and H2S removal in membrane gas absorber. Also it is found that the concentration distribution of CO2 and H2S in the gas phase along the fiber length obeys plug flow model whereas in the methanol absorbent deeply affected by the interface concentration, absorbent velocity and diffusivity. In addition, it is shown that application of membrane gas absorber using methanol absorbents for H2S removal and at higher flow rate is more efficient. Moreover, at operating pressures above 10 atm even at low absorbent rate, H2S concentration depletion is relatively complete while at 1 atm this value is about 30%. This means that removal efficiency decreases with an increase in temperature and it is more important especially for H2S.

碳钢在CO_2-H_2S体系中的腐蚀规律研究

采用氢扩散法、交流阻抗法和电子探针分析研究碳钢在弱酸条件下的 Na Cl溶液中 ,通入 CO2 ,以及加入微量 H2 S的腐蚀过程和渗氢量之间的关系 ,CO2 以及 H2 S的浓度在不同 p H值对这个过程的影响 ,研究其腐蚀机理。实验表明 ,p H值在 4～ 6.5之间时 ,CO2 以及 H2 S对腐蚀过程和渗氢过程有着明显的加速作用 ,并且 ,随着p H值的降低 ,CO2 和 H2 S对渗氢量的增加有明显的促进作用。

O_3、O_3/H_2O_2降解TNT的实验研究

利用自制装置 ,实验研究了不同反应条件下 ,O3 、O3 /H2 O2 对 TNT的降解规律。结果表明 ,O3 对 TNT具有一定降解功效 ,提高体系的 p H值或添加 H2 O2 均利于 TNT的降解。O3 降解 TNT,可能产生抗氧化性更强的中间产物及其积累 ,而 O3 /H2 O2 作用过程中则没有发生。p H从 1升到 1 2 ,利于 O3 对 TNT降解 ,但超过 1 2时 ,对 O3 作用的影响不再明显 ,p H的最适范围是 1 0～ 1 2 ;O3 /H2 O2作用时 ,1 0为其 p H的临界值 ,当提高或降低 p H都会降低其对 TNT降解能力。维持体系的 p H稳定 ,有利于 O3 降解 TNT,但对 O3 /H2 O2 作用功效的影响不明显。尽管温度对 O3 、O3 /H2 O2 降解 TNT功效的影响较小 ,但温度的提高不利于两者功效的发挥 ,尤其是