Liquid-vapor distribution of amines and acid ionization constants of their ammonium salts in aqueous systems at high temperature

Ammonia and volatile organic amines are used to treat the water in steam generating systems to afford protection of the steam- and feedwater circuits from corrosion by acidic condensate. The base strength and the volatility of the reagent used are two important parameters that have bearing on its ability to inhibit corrosion; they determine the pH of the solution produced from condensing steam. The distribution of thirteen amines between water and steam in the temperature range 150 to 325°C was studied. The amines were chosen on the basis of their known room-temperature base strength. The acid ionization constant of the ammonium salts of seven of these amines was determined by conductivity measurement in the temperature range 25 to 275°C. Amines with high room-temperature base strength and distribution coefficient in the optimum range were chosen for the high-temperature base strength determination. The results of these studies were used to estimate the effectiveness of these amines in raising the pH of the condensate from steam containing carbon dioxide and acetic acid, to provide the basis for further studies on the corrosion inhibition properties of the amines.     

Solubility phenomena in industrial and natural system

The importance of solubility phenomena in industrial and natural systems is illustrated mainly by examples related to nuclear energy development. Illustrative examples are given of the consequences of changes in solubility due to gradients of temperature (hydrothermal mass transport), chemical composition (hydrothermal alteration of minerals) electrochemical potential (corrosion) and mechanical stress (fracture mechanics). The chemical systems of interest are primarily insoluble oxides in high temperature water, for example: transition metal oxides on surfaces of structural metal alloys of power plant steam generators; actinide and other heavy metal oxides of nuclear fuels; silicate glasses for immobilizing fission product wastes, and minerals in the rocks of an underground waste vault in contact with heated ground water. Requirements for improved solubility measurement equipment and techniques, experimental data and theoretical methods are noted. Some recent solubility data and their shortcomings are outlined for specific examples, including UO₂, basic lead carbonates, potassium aluminosilicate (feldspars), three to five component borosilicate glasses and zirconium hydride (in Zr metal).Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Cu/ZrO2催化剂上乙醇水蒸气重整反应的研究Ⅱ反应条件的影响

采用沉淀法或醇凝胶法、浸渍法制备Cu/ZrO2催化剂,在常压微型固定床石英管反应器上进行乙醇水蒸气重整反应,采用程序升温还原（TPR）技术表征催化剂的还原特性。考察了催化剂还原温度、反应温度、水醇比、空速等对反应的影响以及催化剂的稳定性。结果表明,在300℃～500℃,随反应温度升高,乙醇转化率增大,H2选择性下降。不同还原温度对转化率的影响不是很大,对于H2选择性,300℃、400℃还原的催化剂优于500℃还原的催化剂。高水醇比有利于提高转化率和H2选择性。随空速增大,转化率和H2选择性呈现下降的趋势。8%Cu/ZrO2催化剂在400℃或450℃反应22h显示出良好的稳定性。     

Temperature dependencies of amide 1H- and 15N-chemical shifts in hyaluronan oligosaccharides

Temperature coefficients (Deltadelta/DeltaT) of amide chemical shifts of N-acetylglucosamine residues have been measured in a range of oligosaccharides of the important vertebrate polysaccharide hyaluronan. Odd- and even-numbered oligosaccharides with glucuronic acid, Delta-4,5-unsaturated glucuronic acid and N-acetylglucosamine at the termini were investigated. All amide proton temperature coefficients were only slightly less negative (-6.9 to - 9.1 ppb/ degrees C) than those of amide protons in free exchange with water (approximately equal to -11 ppb/ degrees C), indicating an absence of persistent intramolecular hydrogen bonds. With the exception of amide groups in reducing-terminal N-acetylglucosamine rings, all amide proton environments have the same temperature coefficient (-6.9 ppb/ degrees C), irrespective of differences in amide group chemical shifts and (3)J(HH) coupling constants, i.e. they do not sense subtle differences in orientation of the amide group. Amide nitrogen temperature coefficients report the same phenomena but with greater sensitivity. These data provide a set of reference values for temperature coefficients measured in other carbohydrates with acetamido sugars.     

Electrodes for Potential Measurements in Aqueous Systems at High Temperatures and Pressures

The measurement of pH, redox potentials, and corrosion potentials at high temperatures and pressures is often desirable for the control and monitoring of industrial processes; e.g., for controlling water chemistry in conventional and nuclear power generators, for process control in the chemical industry, and for monitoring performance in petroleum extraction and refining. Such measurements are also needed for research on the thermodynamics of high-temperature aqueous solutions including those associated with geothermal and hydrothermal reactions. Zirconia electrodes for these purposes are described, and their application is illustrated with examples. While not yet routinely available on a commercial basis, useful versions can be readily fabricated in the laboratory. Some of the pitfalls encountered in making such measurements at elevated temperatures are also discussed because great care is often required to assure that valid and useful data are being obtained.     

Pd/ZnO催化甲醇水蒸气重整理论研究

随着化石能源的日渐枯竭和人们对环境保护的日益重视,发展清洁高效的新能源成为世界各国高度关注的战略课题。甲醇水蒸气重整是生产氢能的有效方法之一,Pd/ZnO催化剂热稳定性好、选择性高,是可能替代Cu/ZnO的催化剂。本文综述了近十年来采用理论方法对Pd/ZnO催化甲醇水蒸气重整制氢机理的研究工作。文章首先论述了催化剂的研究进展,然后对水在单体和聚集状态下在单层及多层平整的和阶梯状的合金表面的吸附和解离进行了总结;接着对甲醇、甲氧基和甲醛在合金表面的吸附和化学反应的热力学和动力学作了介绍;随后基于计算结果,对甲醇反应机理给予了详细的描述。最后对全文进行了总结并对未来的研究作了展望。     

甲醇POSR制氢的反应网络热力学分析和有效因子的估算

在Cu/ZnO/Al2O3催化剂上对甲醇部分氧化蒸汽重整制备氢气反应的动力学过程进行了研究。在常压和473 K～1 073 K温度范围内对该反应网络中的甲醇部分氧化、甲醇蒸汽重整、甲醇分解和水煤气反应的化学平衡进行了分析。在对这些反应的催化剂Cu/ZnO/Al2O3动力学研究的基础上，根据有效因子的基本概念，考虑催化剂颗粒内的扩散限制，对每个反应沿反应器床层的有效因子进行了估算。     

Surface composition of materials used as catalysts for methanol steam reforming: a theoretical study.

PdZn (1:1) alloy is assumed to be the active component of a promising catalyst for methanol steam reforming. Using density functional calculations on periodic supercell slab models, followed by atomistic thermodynamics modeling, we study the chemical composition of the surfaces PdZn(111) and, as a reference, Cu(111) in contact with water and hydrogen at conditions relevant to methanol steam reforming. For the two surfaces, we determine similar maximum adsorption energies for the dissociative adsorption of H(2), O(2), and the molecular adsorption of H(2)O. These reactions are calculated to be exothermic by about -40, -320, and -20 kJ mol(-1), respectively. Using a thermodynamic analysis based on theoretically predicted adsorption energies and vibrational frequencies, we determine the most favorable surface compositions for given pressure windows. However, surface energy plots alone cannot provide quantitative information on individual coverages in a system of coupled adsorption reactions. To overcome this limitation, we employ a kinetic model, from which equilibrium surface coverages of H, O, OH, and H(2)O are derived. We also discuss the sensitivity of our results and the ensuing conclusions with regard to the model surfaces employed and the inaccuracies of our computational method. Our kinetic model predicts surfaces of both materials, PdZn and Cu, to be essentially adsorbate-free already from very low values of the partial pressure of H(2). The model surfaces PdZn(111) and Cu(111) are predicted to be free of water-related adsorbates for a partial H(2) pressure greater than 10(-8) and 10(-5) atm, respectively.     

频哪醇重排反应的研究进展

频哪醇重排反应是由1,2-二醇在酸催化下发生分子内重排脱水,生成频哪酮的反应。频哪酮是一种重要的有机化工中间体,广泛应用于农药、医学、染料等领域。本文综述了频哪醇重排反应的研究进展,主要包括频哪醇在高温液态水和超临界水中的重排反应;无机酸、路易斯酸和分子筛催化的反应;固相条件下的反应;以及光化学、电化学重排等方面的研究...     

Numerical analysis and experimental study of hydrogen production from dimethyl ether steam reforming

An experimental and theoretical study of steam reforming of dimethyl ether was carried out in a processor for fuel cell vehicles to explore the effect of temperature gradient and hydrogen content of the processor.A steady-state,laminar,two-dimensional axi-symmetric model was proposed to investigate the fluid flow,heat transfer and chemical reactions in the dimethyl ether steam reforming processor using porous medium approach.The numerical model was established with Star-CD program using SIMPLE algorithm and finite volume method.Experimental verification of the two-dimensional mathematical model was conducted.The numerical results coincided well with the experimental data.The effects of the parameters on the temperature gradient and hydrogen content of the processor were studied using the numerical model.     

Ab initio surface phase diagram of the {104} calcite surface

Electronic structure calculations, performed at the density functional theory level, were employed to study the surface termination of the {104} calcite surface in contact with a gaseous phase containing water and carbon dioxide. A surface phase diagram was generated to investigate the change in surface termination as a function of temperature, pressure, and gas-phase composition. This diagram revealed that a nonstoichiometric termination could occur in atmospheric conditions at high relative humidity, hence suggesting that nonstoichiometric surfaces can play a major role in the chemistry of calcite surfaces.     

Reduced Graphene Oxide/Carbon Fiber Composite Membrane for Self-floating Solar-thermal Steam Production

Solar-thermal water evaporation has attracted increasing attention owing to the promising potential to solve the global clean water and energy crisis. But, the development of this strategy is limited by the lack of materials with high solar-thermal conversion efficiency, local heating of superficial water, easy preparation and low cost. Herein, we proposed a facile strategy to prepare a reduced graphene oxide/carbon fiber composite membrane, denoted as RGO/CF membrane. The surface of the RGO/CF membrane was highly hydrophobic, endowing the composite membrane with the self-floating ability on the water without any assistance. The light absorbance ability achieved as high as ca. 98% in the wavelength range of 300-1200 nm. The steam evaporation efficiency under the illumination of 3-sun was 97%, generating water steam at a rate of 4.54 kg·m^-2·h^-1. Moreover, the solar-thermal steam production rate showed high stability during successive 30 cycle tests.     

Direct detection of polyaromatic hydrocarbons, estrogenic compounds and pesticides in water using desorption chemical ionisation membrane inlet mass spectrometry

This paper describes the use of desorption chemical ionisation membrane inlet mass spectrometry (DCI-MIMS) for the detection of a broad range of common contaminants in water. In addition, we discuss the advantages/disadvantages of two different types of chemical ionisation reagent gases, i-butene (a Broensted acid reagent) and argon (a charge exchange reagent). We found that polyaromatic hydrocarbons was detectable at ppt levels, the estrogenic compounds diethyl phthalate and octylphenol at high ppt levels, steroid hormones at ppb levels, hydrophobic pesticides at low ppb levels, whereas hydrophilic pesticides and bisphenol A were not detectable at all. With the exception of the polyaromatic hydrocarbons and pentachlorophenol, none of the reported compounds have to our knowledge been detected previously by other MIMS systems. In most cases the Broensted acid reagent gave characteristic ions at high mass/charge ratio, whereas the charge exchange reagent gave less characteristic ions at low m/z ratio. However, the sensitivity was generally not as good with the Broensted acid reagent as with the charge exchange reagent, since the Broensted acid reagent, i-butene, gave a large chemical background.     

Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming

Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.     

Modeling the acid-base surface chemistry of montmorillonite

Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we show that the apparent discrepancy between titration data sets results in large part from the widespread use of an erroneous assumption of zero specific net proton surface charge at the onset of titration. Using a novel simulation scheme involving a surface chemistry model to simulate both pretreatment and titration, we find that montmorillonite edge surface chemistry models that account for the "spillover" of electrostatic potential from basal onto edge surfaces and for the stabilization of deprotonated Al-Si bridging sites through bond-length relaxation at the edge surface can reproduce key features of the best available experimental titration data (the influence of pretreatment conditions on experimental results, the absence of a point of zero salt effect, buffer capacity in the acidic pH range). However, no combination of current models of edge surface structure, reactivity and electrostatics can quantitatively predict, without fitted parameters, the experimental titration data over the entire range of pH (4.5 to 9) and ionic strength (0.001 to 0.5 mol dm(-3)) covered by available data.     

Gram-negative bacteria viable in ultrapure water: identification of bacteria isolated from ultrapure water and effect of temperature on their behavior

This study describes the effect of temperature on the behavior of bacteria viable in ultrapure water and the contamination of ultrapure water by bacteria. Three species of bacteria were isolated from ultrapure water (total organic carbon, 60 ppb and 5 ppb; effluent resistivity > 18 MΩ cm at 25°C) and identified by morphological and physiological characteristics. The three isolates were incubated in water for injection and PYG broth to check the growth profile at various temperatures. In PYG broth, temperature influenced the behavior of bacteria directly; however, it did not in water for injection. By checking both viable and non-viable bacterial numbers and endotoxin concentration in pure water, the water was found to be contaminated with non-viable bacteria and newly generated endotoxins besides viable bacteria. A column treatment, a mixed bed of fully regenerated strong acid cation exchange resin (SACER) and strong base anion exchange resin (SBAER), was used to remove bacteria from pure water. Bacteria could not grow on the surfaces of ion exchange resins in the mixed bed. The removal of bacteria was more effective as pure water was circulated through the mixed bed more rapidly.     

生物油水蒸气气化实验研究

利用固定床反应器对生物油的水蒸气非催化气化性能进行了实验研究,考察了温度和水蒸气的加入量对气化过程的影响,对气化所得粗合成气的组成分布进行了分析。结果表明,升高温度有利于生物油向合成气转化,1 200 ℃时,生物油的碳转化率可达97.8%,合成气有效成分(H₂+CO)的产率可达77%,其中H₂/CO摩尔比为1.19;水蒸气的加入可以提高合成气中的H₂/CO摩尔比,当S/C(水碳比)=4时,合成气中的H₂/CO摩尔比可达3.69,与此同时,水蒸气的加入不利于合成气有效成分产率的提高;生物油气化所得气体为中热值气体。     

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single‐mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave‐transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high‐temperature fluorine–chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors.     

Heat capacity and thermodynamical properties of the crystal of [RE2(Glu)2(H2O)8](ClO4)4·H2O (RE = Nd, Eu, Dy)

Thermodynamical data of rare earth complexes with amino acid are important for engineering chemistry and fundamental chemistry. However, they have rarely been reported. In this work, a series of crystalline complexes of rare earth perchlorate coordinated with glutamic acid have been synthesized in water medium, and their thermodynamical data, including the heat capacity in low temperature range and the standard enthalpy of formation, were determined. These complexes were identified to be [RE₂(Glu)₂(H₂O)₈](ClO₄)₄·H₂O (RE = Nd, Eu, Dy) by using thermogravimetric analysis (TG), differential thermal analysis (DTA), and chemical and elementary analyses. Their purity has been determined. No melting points were observed for all the three complexes. The heat capacity of the complexes was measured by an adiabatic calorimeter from 79 to 370 K. Abnormal heat capacity values were detected for two of the complexes and the decomposition range of one complex was found. The temperature, enthalpy change and entropy change of the decomposition processes of the three complexes were calculated. The polynomial equations of heat capacity in the experimental temperature range have been obtained by least squares fitting. The standard enthalpy of formation was determined by an isoperibol reaction calorimeter at 298.15 K. Supported by the Research Fund of Beijing Institute of Petro-Chemical Technology (N06-06)     

A Metallic Surface Corrosion Study in Aqueous NaCl Solutions Using Atomic Force Microscopy (AFM)

We report an upper-division undergraduate solid-state materials chemistry experiment involving the pit and crevice corrosion of a copper surface caused by an aqueous NaCl solution simulating a seawater environment. Surface corrosion of the copper can be shown quite dramatically using atomic force microscopy (AFM) within only hours of exposure to the saline solution. The copper surfaces can also be treated with an alkanethiol solution to form a self-assembled monolayer (SAM) on the surface. When exposed to the salt-water solution, the SAM layer is shown by AFM to protect the surface from corrosion. We have also shown that several different AFM analysis methods are needed to adequately quantify the surface features including roughness and power spectral density. This experiment enables students to not only see how AFM can be used to observe changes in surface morphology, but also learn to develop an understanding of the analysis techniques used to quantify AFM data.