Variations in the surface chemistry of methanol with CeO2(100) at low and elevated pressures

The reactions of methanol with and without O₂ were studied on a flat, highly crystalline CeO₂(100) thin‐film surface with ambient pressure XPS. In the absence of O₂, the ambient pressure XPS results indicate that in both low‐pressure (≤10⁻⁵ Torr) and high‐pressure regimes (≥10⁻¹ Torr), the dominant surface species is methoxy. Methanol decomposition substantially reduces the ceria and C_X deposit build‐up on the surface. When O₂ is present, C_X does not accumulate on the surface and the dominant surface species is different in the low‐pressure and high‐pressure regimes. Methoxy dominates at low pressure, while formate dominates at the higher pressure. The type of surface species appears to be related to the ability of O₂ to fully oxidize the ceria surface during the methanol reaction.     

Influence of Tourmaline on Negative Air Ion Emitting Property of Poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) fibers containing 2 wt% tourmaline powder were found to emit an average 5100 particles/cc negative air ions under frictional conditions, much higher than that of pure poly(ethylene terephthalate) fibers which emitted an average 200 particles/cc negative air ions, but the emitted negative air ions were reduced to 4400 particles/cc when poly(ethylene terephthalate) fibers contained 4 wt% tourmaline powder. In order to understand the influence of tourmaline powder on the negative air ion emitting property of the poly(ethylene terephthalate) fibers, scanning electron microscopy (SEM) morphology, energy dispersive X‐rays (EDX) and wide angle X‐ray diffraction (WAXD) analysis of the PET/tourmaline fiber specimens were performed. Possible reasons are proposed to account for the interesting negative air ion emitting property of the PET/tourmaline fiber specimens. Aggregates of tourmaline powder occurred in the PET matrix, which caused a reduction of the breaking tenacity of the PET/tourmaline fibers.     

Preparation and characterization of plasma polymerized (ethylene + oxygen) thin films

This report describes the preparation and characterization of plasma polymerized (ethylene + oxygen) (PPEO) thin films. The PPEO films described herein represent a unique class of materials from the standpoint of stoichiometry, chemical functionality, and crosslink density. It will be shown that PPEO deposition rate and structure, evidenced both at the surface and in the bulk, are strongly dependent upon the flow rate of O₂ in the ethylene/O₂ feed gas mixture. High O₂ flow rates produce films with relatively high oxygen concentrations. Furthermore, increasing O₂ flow rates lead to film structures which increasingly favor the incorporation of highly oxidized carbon functionalities. These effects (increasing film concentrations of oxygen and highly oxidized carbon functionalities) appear to show no further increase for O₂ flow rates greater than or equal to ca. 10% of the ethylene flow rate.     

X‐ray photoelectron spectroscopic chemical state quantification of mixed nickel metal,oxide and hydroxide systems

Quantitative chemical state X‐ray photoelectron spectroscopic analysis of mixed nickel metal, oxide, hydroxide and oxyhydroxide systems is challenging due to the complexity of the Ni 2p peak shapes resulting from multiplet splitting, shake‐up and plasmon loss structures. Quantification of mixed nickel chemical states and the qualitative determination of low concentrations of Ni(III) species are demonstrated via an approach based on standard spectra from quality reference samples (Ni, NiO, Ni(OH)₂, NiOOH), subtraction of these spectra, and data analysis that integrates information from the Ni 2p spectrum and the O 1s spectra. Quantification of a commercial nickel powder and a thin nickel oxide film grown at 1‐Torr O₂ and 300 °C for 20 min is demonstrated. The effect of uncertain relative sensitivity factors (e.g. Ni 2.67 ± 0.54) is discussed, as is the depth of measurement for thin film analysis based on calculated inelastic mean free paths. Copyright © 2009 John Wiley & Sons, Ltd.     

Plasma deposition of silicon nitride-like thin films from organosilicon precursors

Plasmas containing hexamethyldisilazane or hexamethylcyclotrisilazane and nitrogen or ammonia were used to deposit silicon nitride-like films at low substrate temperature (T<60°C). Optical properties (refractive index and absorption coefficient), chemical composition of the deposit and film growth rate were examined with respect to the deposition parameters (rf power, pressure and feed composition). As deposited films from ammonia containing mixtures were silicon nitride-like, contained carbon, and were nearly oxygen free. Furthermore, only Si−N, Si−H, and N−H bonds were identified in as-deposited films. The reactive Si−H bonds progressively transformed into Si−O bonds as the films were exposed to air. Films deposited from highly ammonia-diluted mixtures, high RF power and low pressure showed the highest stability with refractive indices as high as 1.8.     

Vinyl acetate formation by the reaction of ethylene with acetate species on oxygen-covered Pd(111)

The reaction pathway of vinyl acetate synthesis is scrutinized by reacting gas-phase ethylene (at an effective pressure of 1 x 10-4 Torr) with eta2-acetate species (with a coverage of 0.31 +/- 0.02 monolayer) on a Pd(111)-O(2x2) model catalyst surface in ultrahigh vacuum. It is found that the 1414 cm-1 infrared feature due to the symmetric OCO stretching mode of the acetate species decreases in intensity due to reaction with gas-phase ethylene, while temperature-programmed desorption experiments demonstrate that vinyl acetate is formed. The formation of ethylidyne species is detected when almost all of the acetate species have been removed. The experimental removal kinetics are reproduced by a model in which adsorbed acetates react with an ethylene-derived (possibly ethylene or vinyl) species, where ethylene adsorption is blocked by the acetate present on the surface.     

Natural compounds obtained through centrifugal molecular distillation

Soybean oil deodorized distillate (SODD) is a byproduct from refining edible soybean oil; however, the deodorization process removes unsaponifiable materials, such as sterols and tocopherols. Tocopherols are highly added value materials. Molecular distillation has large potential to be used in order to concentrate tocopherols, because it uses very low levels of temperatures because of the high vacuum and short operating time for separation and, also, it does not use solvents. However, nowadays, the conventional way to recover tocopherols is carrying out chemical reactions prior to molecular distillation, making the process not so suitable to deal with natural products. The purpose of this work is to use only molecular distillation in order to recover tocopherols from SODD. Experiments were performed in the range of 140–220°C. The feed flow rate varied from 5 to 15 g/min. The objective of this study was to remove the maximum amount of free fatty acids (FFA) and, so, to increase the tocopherol concentration without add any extra component to the system. The percentage of FFA in the distillate stream of the molecular still is large at low feed flow rates and low evaporator temperatures, avoiding thermal decomposition effects.     

Some aspects of stability of multiple emulsions in personal cleansing systems

The two dominant factors that were found to affect the stability of multiple emulsions in high HLB surfactant systems are the osmotic pressure imbalance between the internal aqueous phase and the external aqueous phase, and the adsorption/desorption characteristics of the emulsifier/surfactant film at the oil/water interface. Synergistic interaction between the low HLB emulsifier and the high HLB surfactant that produces very low interfacial tension of the order of 10(-2) mN/m at the oil/water interface was found to occur in some of the systems investigated. Long term stability was observed in multiple emulsion containing these systems. However, no synergy was observed in systems in which either the oil or the emulsifier, or both, contained unsaturated chains. In fact, desorption of the adsorbed surfactant film was observed in systems containing unsaturated chains. The observed desorption from the interface of the emulsifier in these systems was attributed mainly to the inability of the unsaturated chains to form a close packed, condensed interfacial film. Presence of closely packed, condensed interfacial film is necessary to prevent solubilization of the adsorbed low HLB emulsifier by the high HLB surfactant. Multiple emulsions prepared using systems containing unsaturated hydrocarbons were highly unstable.     

Natural compounds obtained through centrifugal molecular distillation

Soybean oil deodorized distillate (SODD) is a byproduct from refining edible soybean oil; however, the deodorization process removes unsaponifiable materials, such as sterols and tocopherols. Tocopherols are highly added value materials. Molecular distillation has large potential to be used in order to concentrate tocopherols, because it uses very low levels of temperatures because of the high vacuum and short operating time for separation and, also, it does not use solvents. However, nowadays, the conventional way to recover tocopherols is carrying out chemical reactions prior to molecular distillation, making the process not so suitable to deal with natural products. The purpose of this work is to use only molecular distillation in order to recover tocopherols from SODD. Experiments were performed in the range of 140-220 degrees C. The feed flow rate varied from 5 to 15 g/min. The objective of this study was to remove the maximum amount of free fatty acids (FFA) and, so, to increase the tocopherol concentration without add any extra component to the system. The percentage of FFA in the distillate stream of the molecular still is large at low feed flow rates and low evaporator temperatures, avoiding thermal decomposition effects.     

Thermodynamic and structural properties of water adsorbed film on MgO (100) ionic surface

We have investigated by adsorption isotherms and neutron diffraction measurements, respectively the thermodynamic and structural properties of water physisorbed film on MgO (100) powder. Thanks to a high temperature thermal treatment, under vacuum, our MgO powder samples are characterized by a highly homogeneous (100) MgO surface. We have determined the structure of the (2D) water film physisorbed on such an ionic surface. This one is a commensurate P(2×3) structure which is very similar to the (110) planes of ice-VII. Recall that ice VII, which is stable at very high pressure, is characterized by a quite large density (d = 1.6).     

Radiation-Induced Solid-State Polymerization of Derivatives of Methacrylic Acid. VII. A Differential Scanning Calorimetric Investigation of the Dehydration and Polymerization of Barium Methacrylate

Abstract

Barium methacrylate monohydrate showed two dehydration steps (at 80 and 110°C), in small crystals, but only one step (at 80° C) in fine powder. The equilibrium water vapor pres-sure was independent of the degree of hydration and its temperature dependence was found to be log₁₀ p_H2O (Torr)=10.70 - 2858/T, giving ΔH (dehyd)=54 ±4 kJ mole^?1. Small doses of γ-irradiation at 78° C suppressed the second de-hydration endotherm and shifted the first to higher temperatures. Larger radiation doses caused the endotherm to diminish and be re-placed by a polymerization exotherm. The variations in position with scan rate gave E_a=163 kJ mole^?1, similar to the value from isothermal polymerization rate measurements. There was no evidence of polymerization in the anhydrate except at the decompo-sition temperature.     

Thermal decomposition of ethanol. 4. Ab initio chemical kinetics for reactions of H atoms with CH3CH2O and CH3CHOH radicals

The potential energy surfaces of H-atom reactions with CH(3)CH(2)O and CH(3)CHOH, two major radicals in the decomposition and oxidation of ethanol, have been studied at the CCSD(T)/6-311+G(3df,2p) level of theory with geometric optimization carried out at the BH&HLYP/6-311+G(3df,2p) level. The direct hydrogen abstraction channels and the indirect association/decomposition channels from the chemically activated ethanol molecule have been considered for both reactions. The rate constants for both reactions have been calculated at 100-3000 K and 10(-4) Torr to 10(3) atm Ar pressure by microcanonical VTST/RRKM theory with master equation solution for all accessible product channels. The results show that the major product channel of the CH(3)CH(2)O + H reaction is CH(3) + CH(2)OH under atmospheric pressure conditions. Only at high pressure and low temperature, the rate constant for CH(3)CH(2)OH formation by collisonal deactivation becomes dominant. For CH(3)CHOH + H, there are three major product channels; at high temperatures, CH(3)+CH(2)OH production predominates at low pressures (P < 100 Torr), while the formation of CH(3)CH(2)OH by collisional deactivation becomes competitive at high pressures and low temperatures (T < 500 K). At high temperatures, the direct hydrogen abstraction reaction producing CH(2)CHOH + H(2) becomes dominant. Rate constants for all accessible product channels in both systems have been predicted and tabulated for modeling applications. The predicted value for CH(3)CHOH + H at 295 K and 1 Torr pressure agrees closely with available experimental data. For practical modeling applications, the rate constants for the thermal unimolecular decomposition of ethanol giving key accessible products have been predicted; those for the two major product channels taking place by dehydration and C-C breaking agree closely with available literature data.     

Sodium hydroxide-assisted dechlorination of a poly(vinylidene chloride)-containing wrapping film in ethylene glycol solution

Poly(vinylidene chloride) (PVDC) wrapping film was dechlorinated using solutions of NaOH in ethylene glycol (EG) at temperatures between 150 and 190 °C. The reaction was comparable to that for PVDC powder; however, it occurred at a lower NaOH concentration, which can be explained by the dissolution of additives present in the wrapping film. Therefore, the best results for the dechlorination of the wrapping film were obtained at a temperature of 190 °C and NaOH concentrations of 0.1 M and 0.5 M, resulting in dechlorination yields of almost 90% after 135 min. For the dechlorination reaction, the activation energy of the PVDC wrapping film (185 kJ mol⁻¹) was determined to be higher than that of PVDC powder; this finding could be attributed to the presence of a stabilizer and the smaller surface area of the PVDC wrapping film.     

The adsorption structure of NO on Pd(111) at high pressures studied by STM and DFT

Using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we study the adsorption structure of NO on Pd(111) at pressures of up to 720 Torr. From atomically resolved STM images, we identify, at high pressures, only the (2 x 2)-3NO structure, which is identical with the highest NO-coverage structure found at low pressure and low temperature. DFT calculations confirm that the (2 x 2)-3NO structure is indeed the most stable adsorption structure at high pressures. Contrary to recent suggestions in the literature, we therefore conclude that we find no evidence for a (3 x 3)-7NO structure on Pd(111) at high NO pressure.     

Ethylene Epoxidation in an AC Dielectric Barrier Discharge Jet System

In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C₂H₄) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C₂H₄ cracking and further reactions, while the oxygen (O₂) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O₂/C₂H₄ feed molar ratio, applied voltage, input frequency, and C₂H₄ feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 × 10^?21 and 6.0 × 10^?21 Ws/molecule C₂H₄ converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm³/min (corresponding to a residence time of 0.022 s), an O₂/C₂H₄ feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C₂H₄ feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.     

Degeneration of β-glucosidase activity in a foam fractionation process

Foam fractionation is a promising technique for concentrating proteins because of its simplicity and low operating cost. One such protein that can be foamed is the enzyme cellulase. The use of inexpensively purified cellulase may be a key step in the economical production of ethanol from biomass. We conducted foam fractionation experiments at total reflux using the cellulase component β-glucosidase to study how continuous shear affects β-glucosidase in a foam such as a fermentation or foam fractionation process. The experiments were conducted at pH 2.4, 5.4, and 11.6 and airflow rates of 3, 6, 15, 20, and 32 cc/min to determine how β-glucosidase activity changes in time at these different conditions. This is apparently a novel and simple way of testing for changes in enzyme activity within a protein foam. The activity did not degenerate during 5 min of reflux at pH 5.4 at an airflow rate of 10 cc/ min. It was established that at 10 min of refluxing, the β-glucosidase denatured more as the flow rate increased. At pH 2.4 and a flow rate of 10 cc/min, the activity remained constant for at least 15 min.     

Acetylene Pyrolysis in Tubular Reactor

Pyrolysis of acetylene was investigated in a tubular reactor of graphite with an internal lining of alumina. The temperature range was 850–1650 °C, and the pressure was about 0.133 bar (100 Torr). Pure acetylene and acetylene diluted with argon or hydrogen were used as feed. Carbon and hydrogen are the main products from acetylene pyrolysis particularly at higher conversion. At lower conversion of acetylene, other gas products were formed; the amount of these depended on temperature, dilution, and conversion. Benzene and vinyl acetylene are the main gas products from pyrolysis of pure acetylene below 1000 °C and at low conversion. Diacetylene increases with increasing temperature. Dilution with hydrogen changes the composition of the gas product, decreases the selectivity of vinyl acetylene and benzene, and increases the formation of methane and ethylene. Gas‐phase equilibrium may be approached between some components. The conversion of acetylene with argon dilution and low conversion was found to be of second order. Pyrolysis of pure acetylene at lower temperature and low conversion gave the rate constant k = 3.1 × 10⁹ · exp(?34.8/RT) L mol^?1 s^?1 with an activation energy of 34.8 kcal mol^?1. The initial reaction at 864 °C is a molecular formation of vinyl acetylene. The initial activation of acetylene in gas phase seems to be rate determining and of second order in acetylene. Decomposition of acetylene can take place both homogeneously and heterogeneously. Above a critical partial pressure of acetylene, the decomposition is apparently explosive with instant plugging of the reactor with carbon.     

Sorptive reconstruction of the CuAlCl(4) framework upon reversible ethylene binding

Three ethylene adducts to CuAlCl(4) have been characterized by single crystal and/or powder X-ray diffraction, (13)C, (27)Al and (63)Cu MAS NMR and diffuse reflectance UV-vis spectroscopy. (C(2)H(4))(2)CuAlCl(4), a = 7.1274(5) b = 12.509(1) c = 11.997(3) beta = 91.19 degrees, Pc, Z = 4; alpha-(C(2)H(4))CuAlCl(4), a =7.041(3) b = 10.754(8) c =11.742(9) beta = 102.48(6), P2(1), Z = 4 and beta-(C(2)H(4))CuAlCl(4), a = 7.306(2), b = 16.133(3), c = 7.094(1), Pna2(1), Z = 4. Up to 2 equiv of ethylene ( approximately 200 cm(3)/g relative to stp) are sorbed at room temperatures and pressures as low as 300 Torr. The ethylene ligands are bound to copper (I) primarily through a sigma-interaction, because the AlCl(4)(-) groups also bound to copper prevent any significant pi-back-bonding. The olefin binding is reversible and has been characterized by gravimetric and volumetric adsorption analysis and by time and pressure resolved synchrotron powder X-ray diffraction. Comparison of the parent crystal structure to those of the adduct phases provide an atomistic picture of the sorptive reconstruction reactions. These are proposed to proceed by a classic substitution mechanism that is directed by the van der Waals channels of the parent crystalline lattice.     

Deposition of Ethylene-Hexafluoropropene Gradient Plasma-Copolymer Using Dielectric Barrier Discharge Reactor at Atmospheric Pressure: Application to Release Coatings on Pressure-Sensitive Tape

Plasma-polymerized hexafluoropropene (PPHFP) film deposited using a dielectric barrier discharge reactor at atmospheric pressure had low enough adhesive strength, 22.2 Nm^–1, for use as a release coating of pressure-sensitive adhesive tapes, but the bond strength between PPHFP film and a poly (ethylene terephthalate) (PET) substrate film was slightly weak: some part of the PPHFP deposits could be peeled from the PET substrate. Since the XPS results indicated that the bond strength between plasma-polymerized ethylene (PPE) film and PET substrate was strong enough, we tried to deposit PPE and plasma-polymerized ethylene - hexafluoropropene gradient plasma-copolymer between the PET substrate and the PPHFP film. This multi-layer film (MLF) had low enough adhesive strength, 36.6 Nm^–1, for use as the release coating; this value was near that of a control sample, Teflon sheet, 21.6 Nm^–1. Moreover, the bond strength between MLF and PET substrate became stronger than that between PPHFP and PET films.     

Temperature‐ and Pressure‐Dependent Kinetics of CH2OO + CH3COCH3 and CH2OO + CH3CHO: Direct Measurements and Theoretical Analysis

The rate coefficients of the gas‐phase reactions CH₂OO + CH₃COCH₃ and CH₂OO + CH₃CHO have been experimentally determined from 298–500 K and 4–50 Torr using pulsed laser photolysis with multiple‐pass UV absorption at 375 nm, and products were detected using photoionization mass spectrometry at 10.5 eV. The CH₂OO + CH₃CHO reaction's rate coefficient is ～4 times faster over the temperature 298–500 K range studied here. Both reactions have negative temperature dependence. The T dependence of both reactions was captured in simple Arrhenius expressions: The rate of the reactions of CH₂OO with carbonyl compounds at room temperature is two orders of magnitude higher than that reported previously for the reaction with alkenes, but the A factors are of the same order of magnitude. Theoretical analysis of the entrance channel reveals that the inner 1,3‐cycloaddition transition state is rate limiting at normal temperatures. Predicted rate‐coefficients (RCCSD(T)‐F12a/cc‐pVTZ‐F12//B3LYP/MG3S level of theory) in the low‐pressure limit accurately reproduce the experimentally observed temperature dependence. The calculations only qualitatively reproduce the A factors and the relative reactivity between CH₃CHO and CH₃COCH₃. The rate coefficients are weakly pressure dependent, within the uncertainties of the current measurements. The predicted major products are not detectable with our photoionization source, but heavier species yielding ions with masses m/z = 104 and 89 are observed as products from the reaction of CH₂OO with CH₃COCH₃. The yield of m/z = 89 exhibits positive pressure dependence that appears to have already reached a high‐pressure limit by 25 Torr.