Behavior Of Ethylene Research Articles

Insights into the behavior of ethylene oxide-1,2-epoxybutane diblock copolymers in water as a function of temperature and the presence of colloidal silica

HypothesisNonionic surfactants have been widely used for many consumer products and industrial processes, and their applications often involve temperature-cycling across cloud point temperature (Tcloud). To explore the behavior of nonionic surfactants across Tcloud and when mixed with colloidal silica at a very dilute concentration around 0.1 wt%, a series of 1,2-epoxybutane-capped alcohol ethoxylates (BAEs) with various cloud points is used as a model system. ExperimentsBAEs with cloud points from 15 to 64 °C were successfully prepared by varying the lengths of 1,2-epoxybutane (BO) and ethylene oxide (EO) blocks and their phase behavior across Tcloud was studied using nuclear magnetic resonance spectroscopy (NMR), dynamic light scattering (DLS) and differential scanning calorimetry (DSC). FindingsIn the absence of silica, the NMR signals are not greatly affected by the cloud point transition, but both the water and surfactant exhibit a decrease in spin-spin relaxation time once the temperature reaches the Tcloud. In the presence of silica, the NMR spectra indicate significantly reduced mobility of the EO portion relative to the alkyl and BO segments. Furthermore, our results suggest that the BAE surfactants are not fractionally clouding out or precipitating with a portion of the compositional distribution during the cloud point transition.

Study on the Influence of the Weak Effect of Benzyl Benzene Ring on the Polymerization Behavior of Ethylene

Study on the Influence of the Weak Effect of Benzyl Benzene Ring on the Polymerization Behavior of Ethylene

Adsorption measurements on a CrOx/γ-Al2O3 catalyst for parameter reduction in kinetic analysis

This work presents an attempt to include more detailed descriptions of adsorption equilibria into the analysis of the rates of heterogeneously catalyzed reactions. The adsorption behavior of ethylene, propylene, oxygen, carbon monoxide and carbon dioxide was studied on a CrOx/γ-Al2O3 catalyst in a broader concentration and temperature range. Dynamic measurements were performed in a tubular reactor applying the Frontal Analysis method, to estimate adsorption isotherms for single components and mixtures individually. The classical Langmuir model and a bi-adsorption model consisting of a Langmuir and a Henry term were parameterized. The temperature dependence of the isotherm model parameters was described via an Arrhenius approach. Using the Multi-Langmuir model and the Ideal Adsorbed Solution Theory, competitive adsorption isotherms for ethylene and propylene were predicted based on the estimated single component parameters. However, the experimental evaluation of the predicted mixture isotherms offered no effect in the concentration range considered. In a higher concentration range the experimental competitive adsorption isotherms were significantly affected. Thus, the considered competitive adsorption models work well. Consequently, the Multi-Langmuir adsorption model is sufficient to describe the investigated model system. With the reliable mathematical description of the adsorption isotherms a more profound description of the reaction rates is possible by separating kinetic and thermodynamic effects.

Grand Canonical Monte Carlo Simulations of Olefins Adsorption in Zeolite ZSM-5

The adsorption behavior of ethylene and propylene in zeolite ZSM-5 was studied by Grand Canonical Monte Carlo (GCMC) simulations. It is found that ethylene and propylene molecules show different adsorption behaviors in the zeolite cavum. The adsorption isotherms of ethylene and propylene in ZSM-5 at 298K and 823K were simulated. The results exhibit that the molecular adsorption is influenced at various temperatures and pressures, leading to different rules for the adsorption of ethylene and propylene molecules in zeolite. At low temperature, when the pressure is enhanced from 100kpa to 1000 kpa, the adsorption amounts of olefin molecule increase obviously and the loading of ethylene are significantly larger than those of propylene. The adsorption of propylene has a preferential adsorption site in cross position, and nearly reaches saturation at pressure higher than 300kPa. While at 823K the adsorption of ethylene is inhibited with lower loading than those of propylene.

Adsorption Equilibrium Parameters of Trace Impurities

Atmospheric air contains various trace impurities which include oxides of nitrogen, carbon, sulphur, and light hydrocarbons. Prior to cryogenic distillation of air to produce oxygen, nitrogen, and argon, these trace impurities have to be removed since many of these compounds constitute a safety hazard in the plant. In this study, adsorption has been considered for their removal and adsorption behavior of ethylene, acetylene, nitrous oxide, acetonitrile, methyl tert-butyl ether, methyl sulfoxide, dimethyl sulfoxide, and methanol have been studied in the Henry's Law low concentration region with several different adsorbents. Adsorption equilibrium parameters have been determined with samples of Alcan pure alumina, Alcan alumina/13X composites Actiguard 600/650PC, CABSORB Chabazite, Ceca13X, and Clinoptilolite by using the concentration pulse chromatographic technique. Heat of adsorption values and van't Hoff plots have been presented.

Behavior of ethylene and ethane within single-walled carbon nanotubes. 1-Adsorption and equilibrium properties

Endohedral adsorption properties of ethylene and ethane onto single-walled carbon nanotubes were investigated using a united atom (2CLJQ) and a fully atomistic (AA-OPLS) force fields, by Grand Canonical Monte Carlo and Molecular Dynamics techniques. Pure fluids were studied at room temperature, T=300 K, and in the pressure ranges 4×10−4<p<47.1 bar (C2H4) and 4×10−4<p<37.9 bar (C2H6). In the low pressure region, isotherms differ quantitatively depending on the intermolecular potential used, but show the same qualitative features. Both potentials predict that ethane is preferentially adsorbed at low pressures, and the opposite behavior was observed at high loadings. Isosteric heats of adsorption and estimates of low pressure Henry’s constants, confirmed that ethane adsorption is the thermodynamically favored process at low pressures. Binary mixtures of C2H4/C2H6 were studied under several (p,T) conditions and the corresponding selectivities towards ethane, S, were evaluated. Small values of S<4 were found in all cases studied. Nanotube geometry plays a minor role on the adsorption properties, which seem to be driven at lower pressures primarily by the larger affinity of the alkane towards the carbon surface and at higher pressures by molecular volume and packing effects. The fact that the selectivity towards ethane is similar to that found earlier on carbon slit pores and larger diameter nanotubes points to the fact that the peculiar 1-D geometry of the nanotubes provides no particular incentive for the adsorption of either species.

Secondary Reactions of Ethylene As Studied in a Laboratory-Scale Recycle Slurry Reactor

Data from a recycle laboratory slurry reactor were considered to investigate the secondary reactions of ethylene in Sasol’s commercial iron-based low-temperature Fischer–Tropsch synthesis. In particular, the behavior of ethylene was compared to that of propylene. No evidence could be found for significant reincorporation of either of these two olefins. Propylene was hydrogenated to a very small extent, whereas ethylene was substantially hydrogenated. The estimated primary olefin/paraffin ratio for the C2 fraction was higher than for the C3 fraction, in line with the prediction of our recently proposed chain length dependent desorption model.

Simultaneous measurement of rheological and conductive properties of carbon black filled ethylene–tetrafluorothylene copolymer

Composites composed of carbon black (CB) filled polymers have been widely applied in many areas such as electromagnetic/radio-frequency interference shielding, electrostatic discharge, conductive adhesives for die attachment in electronic packaging applications, and electroactive polymeric sensors in hand prostheses [1, 2]. It is well known that the morphology and properties of filled polymer composites are greatly influenced by the state of filler dispersion [3]. Due to the small size and high specific surface, the filler particles are favorable to form a three-dimensional flocculation structure [4]. Even though scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations can give us a lot of information on structure and morphology involving fillers, they only reflect the dispersion localized within a two-dimensional microscopic site and thereby are easily misinterpreted with respect on the correlation of the information to the real dispersion space and its contribution to the target properties [5, 6]. It is accepted that dynamic rheological measurements are effective for dealing with the structure and morphology of filled polymers as well as the filler dispersion because the structure of samples tested is indestructible under small strain (c) amplitudes [7]. The rheological properties of highly filled polymer composites may provide essential information about the flocculation structure of the filler that contributes to the physical properties such as mechanical strength, electrical resistivity, and heat conductivity [8]. Much work has been performed on the rheological behavior of various filled polymers. Krishnamoorti and Giannelis [9] observed nonterminal low-frequency rheological behavior in nanocomposites containing layered silicates. Zhang and Archer [10] reported a transition to solid-like response at low oscillation frequencies due to the presence of a filler network in poly(ethyl oxide)/silica nanocomposites. Simultaneous measurement of rheological and conductive behaviors under c has been made on CB-filled natural rubbers [11] or vulcanizates [12] to study the carbon black structure inside these materials. It was found that shear moduli and electrical conductivity vary in an approximately similar way as the amplitude of dynamic oscillation increases. In the aforementioned literatures, small strain oscillation was achieved by using spring while the large one is controlled using machine driving or hand wheel. Recently, Pan and Mckinley [13] studied viscoelasticity and conduction behaviors of an electrorheological fluid suspension using simultaneous measurement technique. To our knowledge, few work has been reported to study filled semicrystalline polymers at temperatures above melting point (Tm) using simultaneous measurement of rheological and conductive behaviors. In a previous paper [14], we examined the conductive behavior of ethylene–tetrafluorothylene (ETFE) copolymer/CB composites and found that the switching characteristic show a reproducible stability at the upper limit of the percolation transition. Here we present some unique results from simultaneous measurements of the dynamic storage modulus (G0) and electrical resistance (R) for ETFE/CB melt. It is noted that the modified rheometer allows us to obtain the data of measuring G0 and R for ETFE/CB composites in a relative wide strain range in one mode. The composites were prepared by mixing ETFE (ETFE750 from DuPont, density 0.942 g cm , melting point Z. Liu Y. Song J. Zhou Q. Zheng (&) Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P.R. China e-mail: zhengqiang@cmsce.zju.edu.cn

Clouding Behavior of Ethylene Oxide‐Propylene Oxide Block Copolymer P85: The Effect of Additives

The characteristic feature of nonionic poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymers is that at higher temperatures they undergo clouding and liquid‐liquid phase separation. The clouding temperature of such block copolymers can be profoundly altered in the presence of various additives. In this work the effect of various additives on the clouding phenomenon of triblock copolymer P85[(EO)26(PO)39(EO)26] is discussed.

Effect of Long-chain Branching and Microgels in the Viscoelastic Behavior of Ethylene—Propylene—Diene Copolymers

Ethylene—propylene-diene (EPDM) terpolymers with different amounts of microgel and long-chain branching have been characterized by dynamic mechanical experiments. Low frequency measurements were found particularly useful for revealing differences in viscoelastic properties of the samples Loss factor values were of limited use, as they are influenced by sample molecular weights. Modified Cole—Cole plots were verified to be molecular weight independent, and could therefore be employed to detect molecular architecture variations. It was determined that long-chain branching and microgels are almost entirely localized in the higher molecular weight fractions of the investigated EPDM samples.

Thermal stability of ethylene-vinyl acetate and ethylene-propylene-diene (EVA-EPDM) blends

The thermal behavior of ethylene–vinyl acetate (EVA) and ethylene propylene–diene (EPDM) blends have been studied by thermogravimetry in nitrogen. The activation energy, preexponential factor, and lifetime have been calculated using software-based on the Flynn and Wall isoconversional procedure. The maximum thermal stability in nitrogen atmosphere was observed for the EV80–EP20 blend. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1829–1835, 1998

Thermally stimulated shape‐memory behavior of ethylene oxide‐ethylene terephthalate segmented copolymer

Thermally stimulated shape‐memory behavior of ethylene oxide‐ethylene terephthalate segmented copolymer

On the association and adsorption behaviour of ethylene oxide/propylene oxide block copolymers in the processes of steel corrosion protection

On the association and adsorption behaviour of ethylene oxide/propylene oxide block copolymers in the processes of steel corrosion protection

Structure and behaviour of SiO2/MgCl2 bisupported Ziegler‐Natta catalysts for olefin polymerization

AbstractBisupported catalysts for olefin polymerization were prepared by mixing a butyl alcoholate solution of MgCI2 with pretreated SiO2 in heptane, and further treating with TiCI4 solution. The silica pretreating conditions and their effects on the composition of the catalysts were studied. The interaction mechanism of the two supports, MgCI2 and SiO2, is discussed. The effect of the composition and the structure of the catalyst on the behaviour of ethylene and propylene polymerization is described. The calcination temperature of SiO2 has a significant effect on composition, structure and properties of the catalysts. There exist both chemical bonding and physical absorption between SiO2 and MgCI2 supports. The activities for propylene polymerization remarkably increase with increasing mole ratio Mg/Ti of the catalysts, while for ethylene polymerization, the activities mainly depend on the Ti content of the catalysts and the calcination temperature of SiO2 used.

The mechanism of the high‐pressure free radical polymerization of ethylene

AbstractThe reaction path of the free radical polymerization of ethylene is usually considered identical to the polymerization mechanism of other vinyl monomers. Available experimental data on the polymerization of ethylene, however, hardly fitted the well‐established path of free radical polymerization. Obviously the mechanism of ethylene polymerization is more complex and not well understood. One reason for this, in our opinion, is insufficient knowledge of the physicochemical state of ethylene under high pressure. A model that described the behavior of ethylene under compression has been proposed. According to the model, and increase in pressure causes the formation of various supermolecular forms of ethylene, each accompanied by transition of the second order. By proposing a stereochemical shape for each supermolecular form calculation of activation volumes for each of these transitions was made. Good agreement was obtained when calculated volumes of activation were compared with corresponding experimental values in the literature.

Reactions on ZSM-5-type zeolite catalysts

Catalytic reactions and sorption measurements have been carried out with ZSM-5 and silicalite catalysts which are distinguished by variation in skeletal heteroatom concentration. The catalysts were used in both the hydrogen-exchanged and sodium-exchanged forms. Sorption measurements were made with the hydrocarbons n-hexane, 3-methylpentane, and 2,2-dimethylbutane, and with the bases ammonia, n-butylamine, t-butylamine, and 4-methylquinoline. Catalytic reactions were carried out on both unpoisoned and base-poisoned catalysts using methanol, propylene, and 3-methylpentane reactants. In addition, the behavior of ethylene and ethanol reactants was also explored. The ease of base sorption and hydrocarbon sorption has been assessed in terms of effective molecular size in relation to the channel size of the catalyst, and this factor is also used as a basis for explaining the effectiveness of bases for poisoning the catalytic reactions. Temperature-programmed desorption (TPD) measurements with ammonia have been used to assess the energetic distribution of sorption sites for bases, and very strong binding sites with a TPD maximum for ammonia at about 780 °K have been identified as the probable sites used in the conversion processes. The main features of the catalytic conversion process are discussed. It is concluded that sorbed C 3,C 4 olefinic residues are general intermediates leading to aromatic formation. Under most circumstances, ethylene was relatively unreactive, and it is inferred that a sorbed C 2 residue, which is related to ethylene by sorption and desorption, is an unlikely general intermediate. A mechanism is suggested for the formation of sorbed C 3,C 4 olefinic residues, and for initial carbon-carbon bond formation from methanol. Catalyst self-poisoning was observed with all catalysts except hydrogen-exchanged ZSM-5.

General conclusions about the copolymerization of ethylene with other monomers by free radical catalysis

AbstractThe behavior of ethylene in copolymerization with methyl acrylate, methyl methacrylate, vinyl acetate, diethyl fumarate, and diethyl maleate was investigated, and reactivity ratios for these systems reported. Significant deviations of all systems investigated, except ethylene–vinyl acetate, from the conventional copolymerization equation are noted and interpreted on the basis of substantial penultimate and penpenultimate effects. The consistency of the reactivity ratios developed in the systems ethylene–methyl acrylate and ethylene–methyl methacrylate with reported values for methyl acrylate–methyl methacrylate is shown by application of the relationship PabPbcPca = PacPcbPba.

LXXV.—The behaviour of ethylene on explosion with less than its own volume of oxygen

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