High‐Impact Polyamide Composites with Linear Ethylene–Norbornene Anhydride Copolymers from Insertion Polymerization

Toughening of polyamide 66 with novel linear norbornene anhydride functionalized polyethylenes leads to an impact performance in the Charpy‐notch impact testing at 23 °C and ?30 °C as high as a_CN = 18.0 ± 1.0 and 13.7 ± 0.8 kJ m^?2, respectively, which compares favorably to a state of the art functional low density polyethylene (LDPE) from high‐pressure copolymerization with a Charpy‐notch impact strength of a_CN = 16.8 ± 0.0 and 13.8 ± 2.1 kJ m^?2 at 23 and ?30 °C, respectively. The linear copolymers are obtained by insertion polymerization at mild ethylene pressures of 5 to 15 bars with phosphinesulfonato Pd (II) catalysts, to yield linear copolymers with norbornene anhydride incorporations as high as 4.8 mol% along with a polymer molecular weight of >10⁵ g mol^?1. Furthermore, the norbornene anhydride functionality serves as a reaction site for postpolymerization functionalization with alcohols to obtain the respective half‐ and diesters of the anhydride functionality. Notably, the impact performance is improved with the increase of the alkyl chain length and degree of branching of the ester functionality in the order methanol < n‐butanol < 2‐ethyl hexanol from 10.0 to 13.8 kJ m^?2.     

Comparative energy barriers for hydrogen activation by homogeneous and heterogeneous metal oxide catalysts

Triethylene glycol solutions of alkali and alkaline earth metal hydroxide complexes are well-defined soluble oxide water-gas shift catalysts which equilibrate the reaction of carbon monoxide and water to yield hydrogen and carbon dioxide at temperatures ranging from 150 ° to 250 °C and carbon monoxide pressures of 1 to 300 atm. Significantly, catalysis proceeds cleanly, even in the complete absence of a metal center in the soluble oxide system. Thus, the rate of hydroxide ion catalyzed hydrogen evolution is highest in the presence of a noncoordinating organic cation: Bu_ΔN⁺>Cs⁺>Na⁺>H⁺>Ca⁺². Furthermore, the activation energy for the homogeneous sodium hydroxide catalyst in triethylene glycol solution, 26±1 kcal, is comparable to that exhibited by a commercially used heterogeneous iron oxide catalyst, 27±0.2 kcal. The alkali metal hydroxide system may be modified for metal cocatalysis. Thus, lead (II) oxide dissolves in the triethylene glycol solutions to yield a new species which exhibits a²⁰⁷Pb NMR resonance shifted 3350 ppm downfield from lead perchlorate. The activity of this lead modified system is improved by three orders of magnitude. Yet, the activation energy is unchanged, 26±1 kcal, suggesting that entropic factors may be important in these homogeneous metal oxide hydrogen evolution/activation systems.     

Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer

The size-dependent particle transmission efficiency of the aerodynamic lens system used in the Aerodyne Aerosol Mass Spectrometer (AMS) was investigated with computational fluid dynamics (CFD) calculations and experimental measurements. The CFD calculations revealed that the entire lens system, including the aerodynamic lens itself, the critical orifice which defines the operating lens pressure, and a valve assembly, needs to be considered. Previous calculations considered only the aerodynamic lens. The calculations also investigated the effect of operating the lens system at two different sampling pressures, 7.8 × 10⁴ Pa (585 torr) and 1.0 × 10⁵ Pa (760 torr). Experimental measurements of transmission efficiency were performed with size-selected diethyl hexyl sebacate (DEHS), NH₄NO₃, and NaNO₃ particles on three different AMS instruments at two different ambient sampling pressures (7.8 × 10⁴ Pa, 585 torr and 1.0 × 10⁵ Pa, 760 torr). Comparisons of the measurements and the calculations show qualitative agreement, but there are significant deviations which are as yet unexplained. On the small size end (30 nm to 150 nm vacuum aerodynamic diameter), the measured transmission efficiency is lower than predicted. On the large size end (> 350 nm vacuum aerodynamic diameter) the measured transmission efficiency is greater than predicted at 7.8 × 10⁴ Pa (585 torr) and in good agreement with the prediction at 1.0 × 10⁵ Pa (760 torr).     

Studies on the mechanism of the hydrogen electrode reaction by means of deuterium tracer—II. The reaction mechanism

The exchange reaction between deuterium gas and light water was conducted with Ni, Rh, and Pt catalyst. Through analysis of isotopic composition of the gaseous hydrogen during the exchange reaction, the exchange rates of the individual steps, H₂ ? 2H(a) and H(a) + B ? H⁺B + e, of the hydrogen electrode reaction were determined at various hydrogen pressures and solution pH's, where H(a) is a hydrogen adatom and B = H₂O or OH^?. The rates of the steps were widely different among the metals studied but, throughout these metals, the hydrogen pressure dependence of the rate of the first step was with the power of 1·0–0·9, and that of the second step, 0·2–0·5. Both the rates were independent of solution pH. Generally, the former step is virtually rate-determining under low hydrogen pressures, whereas the latter takes over the role with increasing hydrogen pressure. Under ordinary pressures, the first step is virtually rate-determining on Pt but neither step is singly rate-determining on Rh and Ni.     

Fluidization at mean pressures less than 30 torr

The article presents some results obtained during fluidization of glass balls with nitrogen and hydrogen flows at mean pressures of between 30 and 4 torr.The classical model used shows that it is possible to deduce the gas flow at incipient fluidization and the pressure drop across the bed from the physical characteristics of the particles and of the gas.     

Diffusion and equilibrium properties of hydrogen in palladium measured by the stripping potentiostatic method

Theory and experiments on the (non-equilibrium) stripping potentiostatic method for evaluation of the diffusion coefficient and desorption isotherms of hydrogen in α-Pd are discussed. Diffusion coefficient of hydrogen D can be evaluated either under transient conditions, from the anodic stripping current (I_a) or under steady-state condition, from the anodic charge corresponding to the stripping of hydrogen held initially in Pd membrane (Q_a). Following data are reported: D = (3.60±0.06) × 10⁻⁷ cm² s⁻¹ (transient) and D = 3.41 × 10⁻⁷ cm² s⁻ (steady-state) at 20°C in 0.1 N H₂SO₄. Equilibrium concentration and equivalent pressure of hydrogen at the entrance side of Pd membrane can be calculated from the steady-state permeation current (I^∞_a or the anodic stripping charge (Q_a) and its open-circuit potential just after stopping hydrogen generation, E⁰_c. Reliable Sieverts' constants (K_s) have been calculated within 15 and 60°C, and the following thermodynamic values obtained: ΔH^o = −(2.6±0.1) kcal (mol H)⁻¹ and ΔS^o = −(14.5±0.4) cal K⁻¹ (mol H)⁻¹. These data agree well with those obtained in gas phase measurements.     

The solubility of hydrogen in aliphatic amines

The solubility of hydrogen in ammonia, monomethylamine, monoethylamine and n-propylamine was determined at temperatures from ?70°C to 25°C and in 1,2-propanediamine and 1,2-ethanediamine over the temperature ranges ?25°C to 11°C and 25°C to 34°C respectively. Measurements were made at total pressures up to 300 psig. The solubility data were correlated in terms of Henry's law and the solubilities are in the range 1 × 10^?5 to 3 × 10^?4 mole fraction at a hydrogen partial pressure of 1 atmosphere. The measured solubility data were used to extend a correlation proposed by Yen and McKetta. This revised correlation may be used to estimate the solubility of hydrogen in polar, associated amines.     

Experimentally defining the safe and efficient,high pressure microwave plasma assisted CVD operating regime for single crystal diamond synthesis

The detailed experimental behavior of a microwave plasma assisted chemical vapor deposition (MPACVD) reactor operating within the high, 180–300 torr, pressure regime is presented. An experimental methodology is described that first defines the reactor operating field map and then enables, while operating at these high pressures, the determination of the efficient, safe and discharge stable diamond synthesis process window. Within this operating window discharge absorbed power densities of 300–1000 W/cm³ are achieved and high quality, single crystal diamond (SCD) synthesis rates of 20–75 μm/h are demonstrated. The influence of several input experimental variables including pressure, N₂ concentration, CH₄ percentage and substrate temperature on SCD deposition is explored. At a constant pressure of 240 torr, a high quality, high growth rate SCD synthesis window versus substrate temperature is experimentally identified between 1030 and 1250 °C. When the input nitrogen impurity level is reduced below 10 ppm in the gas phase the quality of the synthesized diamond is of type IIa or better.     

Gas-liquid equilibria in mixtures of hydrogen and thianaphthene

Gas-liquid equilibrium conditions in binary mixtures of hydrogen and thianaphthene were experimentally determined at temperatures of 190 to 430°C and pressures to 250 atm in a flow apparatus. The same apparatus was also employed to measure the vapor pressure of thianaphthene. Comparisons of the new mixture data with Chao-Seader and Grayson-Streed correlations show that both correlations predict the thianaphthene equilibrium ratios well but are in error by up to about 45 and 35% respectively for K-values of hydrogen.     

Preparation of supported palladium membrane and separation of hydrogen

Palladium acetate was sublimed at a reduced pressure at 400°C., carried into the macropores of the porous wall of an α-alumina support tube and was decomposed there. A thin palladium membrane which was thus formed showed a hydrogen permeance of 10⁶ mol·m²·s¹.-Pa¹ and a hydrogen/nitrogen permselectivity higher than 1000. The membrane was stable against hydrogen embrittlement even when the permeation temperature was varied between 100 and 300°C., and it was stable to sulfur or chlorine. To test the ability of this system for the separation of hydrogen and deuterium, a palladium disk was used instead of the prepared membrane since a definite membrane thickness was necessary for calculation. When H₂ and D₂ permeated through the membrane independently, the H/D permselectivity was approximately 7 at 150–200°C under a feed side pressure of 0.4 MPa and a permeate side pressure of 0.1 MPa. When a mixture of H₂ and D₂ was fed, the H/D permselectivity was reduced to 1.2–1.6.     

States of surface hydrogen under reaction conditions of the Fischer-Tropsch synthesis

The reaction of hydrogen with Fe surfaces was observed by the ellipsometric method at 77 K to 500 ° C under H₂ pressures of 10^–3 Torr (0.1 Pa) to 500 Torr (7×10⁴ Pa). The ellipsometric analysis reveals no existence of adsorbed hydrogen on the surface above 400 °C; hydrogen seems to be alternatively absorbed into the subsurface region of two to three atomic layers. It is concluded that the subsurface hydrogen is specific to the high temperature and the high pressure owing to strained and roughened Fe surfaces as well as the equilibrium with gas phase hydrogen. Absence of adsorbed hydrogen is indicated as well in the ellipsometric response to the hydrogenation reaction of surface carbon species on Fe surfaces.     

Effect of pressure on the hydropyrolysis of Manvers coal

Manvers weakly-coking coal was pyrolysed to 500 °C in a stirred autoclave under varying pressures of hydrogen and nitrogen. As expected the major changes produced by increase in nitrogen pressure were a decrease in tar yield accompanied by increases in gas and, to a smaller extent, in coke yields. Total pressures and hydrogen :coal ratios were altered to obtain maximum yields of tar, gases and liquor. All products were investigated. Tar fractions, separated into neutral, phenolic and basic components, were analysed by g.c.-m.s. Short-chain hydrocarbons were detected in the gas sample. Methanol densities and micropore surface areas the cokes were related to the conditions of pyrolysis. At the relatively low rates of heating employed, pressure had effects on tar composition similar to increasing the temperature of pyrolysis.     

The solubility of carbon dioxide and hydrogen sulfide in a 35 wt% aqueous solution of methyldiethanolamine

The solubility of hydrogen sulfide and carbon dioxide in an aqueous solution containing 35 wt% methyldiethanolamine (MDEA) (3.04 kmol/m³, 4.52 mol/kg) has been measured at 40° and 100°C at partial pressures of the acid gas up to 530 kPa. Some data for hydrogen sulfide in a 50 wt% solution of MDEA (4.38 kmol/m³, 8.39 mol/kg) were also obtained. Also, densities of CO₂-aqueous MDEA solutions were measured at 40°C.     

Glycerol dehydroxylation in hydrogen on a Raney cobalt catalyst

Glycerol dehydroxylation on a Raney cobalt catalyst in hydrogen was studied. It was found that with an increase in temperature from 140 to 200°C at a hydrogen pressure of 30 MPa, glycerol conversion increases from 14 to 97%. The glycerol is completely converted in 20 h, and the yield of 1,2-propanediol is 40%. With an increase in H₂ pressure from 3 to 8 MPa, the glycerol conversion increases from 34 to 95%, and the yield of 1,2-propanediol increases from 18 to 38%. The maximum yield of 1,2-propanediol is 44% at 200°C and a hydrogen pressure of 3 MPa. The glycerol dehydroxylation in hydrogen on heterogeneous catalysts can be considered a promising method of glycerol conversion when glycerol is a byproduct of biodiesel manufacture from vegetable oil and animal fats.     

Effect of pH on microbial hydrogen fermentation

The influence of initial pH of the culture medium on hydrogen production was studied using sucrose solution and a mixed microbial flora from a soybean‐meal silo. Hydrogen production was not observed at pH values of 3.0, 11.0 and 12.0 but low production was observed at pH values 5.0 and 5.5. The pH of the experimental mixture decreased rapidly and produced hydrogen gas within 30 h. Methane was not detected at initial pH values between 6.0 and 10.0. The sucrose degradation efficiency increased as the initial pH value increased from 3.0 to 9.0. The maximum sucrose degradation efficiency of 95% was observed at pH 9.0. The maximum specific production yields of hydrogen, VFAs and alcohols were 126.9 cm³ g^?1 sucrose (pH of 9.0), 0.7 gCOD g^?1 sucrose (pH of 8.0) and 128.7 mgCOD g^?1 sucrose (pH of 9.0), respectively. The relationship between the hydrogen ion concentration and the specific hydrogen production rate has been mathematically described. The best kinetic parameters on the specific hydrogen production rate were K_OH = 1.0 × 10^?7 mol dm^?3 and K_H = 1.1 × 10^?4 mol dm^?3 (r² = 0.86). The maximum specific hydrogen production rate was 37.0 cm³ g^?1 VSS h^?1. © 2002 Society of Chemical Industry     

Iron and hydrogen electrodes in liquid ammonia

Equilibrium potentials of the iron(II)—iron electrode vs TlTlCl; 0.1 M NH₄Cl in liquid ammonia are determined from intersections of Tafel lines for iron deposition and dissolution. The hydrogen electrode is shown to behave reversibly at palladium hydride, but not at platinum with respect to the dependence of hydrogen pressure. The standard potential of iron at 293 K is estimated at E° = ?0,356 (±0,010)V in 0.1 M NH₄NO₃. Standard potentials of other electrodes are reevaluated and shown to be consistent with earlier measurements except for the standard potential of lead. Steady state and transient polarization curves indicate in simple mechanism of the iron electrode involving transfer of iron(II) in one step. The temperature-independent anodic transfer coefficient is α₊ = 0.41 (±0.02), the cathodic transfer coefficient α_? = 0.61 (±0.03). The standard exchange current density at E° is j°_° = 7.10^?7 Acm^?2 for 293 K. Exchange current densities of the hydrogen electrode are j_° = 1.6·10^?9 Acm^?2 at platinized platinum in 0.1 M NH₄Cl both for 293 K.     

The production and properties of filamentous carbon

Carbon filaments have been produced by the cobalt catalysed decomposition of 60 torr acetylene at 725°C. An upper pressure limit of 200 torr is set by polymerisation of acetylene. Pre-heating the acetylene increases filament yield, particularly at either 550 or 650°C. Addition of hydrogen to the acetylene produced a similar but somewhat smaller effect when it was pre-heated to these temperatures. The surface areas of many batches of filaments have been measured by adsorption of radioactive xenon at ?196°C. The values range from 9 to 153 m² · g^?1 depending on the preparation conditions and whether the measurement is made on filaments still bonded to the steel mesh support or on base filaments (when there is access to the inner cores of the filaments). The densities, 2°48 g · cm^?3, indicate that a significant amount of catalyst metal is retained in the filaments. Controlled atmosphere electron microscopy has been used to follow the absorption of water vapour by filaments at ambient temperature.     

A method for correlating and extending vapour pressure data to lower temperatures using thermal data: Vapour pressure equations for some n-alkanes at temperatures below the normal boiling point

Vapour pressures for many liquids are available in the range 50–760 torr but accurate determinations at lower pressures are frequently absent. Extrapolation based on purely empirical equations is hazardous and a convenient method is proposed for extrapolating such data to lower temperatures by utilizing readily available thermal data. The method is based on thermodynamically exact relationships. It has the advantage over previous such approaches that it makes greatest use of data, such as ideal gas and liquid heat capacities at around the temperature at which the vapour pressure is required, which are likely to be available. When applied to the n-alkanes C₆–C₁₆ from the normal boiling temperature down to a reduced temperature of 0·41 the method leads to a convenient vapour equation of the form ln p⁰ = alnT + bT ? (d/T) + E.The constants in this equation have been obtained in a systematic way from the available thermal, volumetric and vapour pressure data for these alkanes. These constants, together with vapour pressures and latent heats at 25°C calculated from them, are listed. Agreement between the calculated quantities at 25°C and experimental values (where available) is good.     

Solubility study for the purification of hydrogen from high pressure hydrocracker off-gas by an absorption-stripping process

Experiments were carried out to identify a solvent which has a high solubility and selectivity for methane relative to hydrogen at 295 K and pressures from 13.88 to 20.78 MPa. Binary solubilities with pure hydrogen and methane, and ternary solubilities with 73 mol% H₂ and 27 mol% CH₄ were measured at 295 K and for pressures from 6.99 to 20.78 MPa in various organic solvents. This gas mixture simulates hydrocracker and hydrotreater off-gases which are candidates for purification with an absorption-stripper. Of the solvents tested, 2,2,4-trimethylpentane (iso-octane), which showed very high methane solubility and a reasonable selectivity, and methylcyclohexane, which showed a very high selectivity and a reasonable solubility, are the best solvents for methane absorption. Correlations for hydrogen and methane as a function of pressure and solvent solubility parameter were developed with the experimental solubilities. Binary interaction parameters for Peng-Robinson (Peng and Robinson, 1976) and Soave-Redlich-Kwong (Soave, 1972) equations of state were calculated with experimental solubility results. Prediction of gas solubility in a ternary system was compared with experimental and found to be satisfactory when experimental binary interaction parameters were used.