Decomposition Of Ethylbenzene Research Articles

Simultaneous ethylbenzene decomposition by ozone in a liquid–solid–gas three-phase system

The aim of this study is to analyse the simultaneous decomposition of ethylbenzene (ETB), in a three-phase system (liquid–solid–gas) using ozone. Ozone was injected in the liquid phase (10 mg of ETB dissolved in water) and then, the gas flow transferred this compound by stripping to the solid phase (calcinated commercial sand or CS, and calcinated agricultural soil or AS). This transferring yields ETB adsorption in the solid phase, where it is decomposed by the residual ozone. The rest of the ETB is transferred to the gas phase over the solid phase, where the remaining ozone mass reacts with the released ETB. In this reaction system, after 20 min, 96% of ETB was decomposed during ozonation. ETB elimination from the liquid phase attains 29% of the initial concentration due to the simultaneous processes: Stripping and decomposition by ozone. Meanwhile, 53% and 58% of ETB were degraded in the CS and AS, respectively. Thus, the rest of ETB was degraded in the gaseous phase (14% and 9%, with the presence of CS and AS respectively). In the proposed treatment scheme, most of the ozone mass is used, minimizing the residual ozone at the reactor outlet, and achieving the almost complete decomposition of the contaminant. The identified intermediates and final products of ETB decomposition at each reaction phase (malonic, maleic, oxalic as well as formic acids) are less toxic than ETB (demonstrated by the seed germination test in the liquid phase). This reaction strategy yields improving ozone consumption along with the decomposition of ETB. • The decomposition of the ethylbenzene in a three-phase system (liquid–solid–gaseous) by ozone is studied. • The gas was injected in the liquid phase and then, the gas flow transferred this compound by stripping to the solid phase. • This transferring yields the ETB adsorption on the solid phase, where it is decomposed by the residual ozone. • The rest of ETB is transferred to the gas phase over the solid phase, where the remaining ozone reacts with the ETB. • The intermediates and final products from the ETB decomposition are less toxic than the ETB.

Comparative study on ignition characteristics of styrene and ethylbenzene behind reflected shock waves

Experimental and numerical research is performed on the ignition delay times for both styrene and ethylbenzene at reflected pressures of 2, 4, and 10 atm; temperature range of 1165 K ∼ 1670 K, equivalence ratios of 0.5, 1.0, and 1.5; and fuel concentrations of 0.25, 0.5, and 1.0 in a shock tube. The experimental results show that styrene is more reactive at high temperatures, but the oppsite is true at low temperatures. The chemical kinetic mechanisms for styrene and ethylbenzene are modified based on three kinetic models as proposed by MetacYuan et al., Comandini et al., and LLNL. The modified mechanism gives a good prediction to the presented experimental data. The reaction pathway analysis reveals that ethylbenzene is consumed primarily by the unimolecular decomposition of ethylbenzene to benzyl at high temperatures, while H-abstraction reactions are dominated in the consuming routes of ethylbenzene at low temperatures. For styrene, the H-abstraction reaction is dominated in both high and low temperatures. It is found that the reactions relevant to benzyl have significant inhibitor effects on the ignition delay times for the two test fuels using sensitivity analyses. It is concluded that different concentrations of benzyl radicals result in various ignition delay times of styrene and ethylbenzene.

Study of PAH formation in laminar premixed toluene and C8H10 aromatics flames

Toluene and C8H10 aromatic fuels are widely proposed as components of surrogate mixtures and usually employed as the prototypical fuels to investigate the combustion properties of aromatic fuels. In this study, the PAH formation of pure C8H10 aromatics (xylenes and ethylbenzene) and toluene was studied in a laminar premixed flame at atmospheric pressure using laser-induced fluorescence (LIF) diagnostic. The experimental results indicated the aromatic structure has a significant influence on the PAH tendency, and the observed LIF intensities were sequenced by toluene < xylenes < ethylbenzene. A detailed kinetic model was employed to validate against the experimental results based on the ROP analysis. The predicted mole fraction profiles of PAHs were consistent with the measured PAH tendency for toluene, o-xylene, and ethylbenzene. The chemical kinetic analysis indicated that benzyl is the most dominant intermediate product in toluene decomposition and precursor in PAH formation, corresponding to methylbenzyl in o-xylene flame, styrene and benzyl in ethylbenzene flame. In the comparison of o-xylene and toluene, the increased methylated groups on the benzenoid ring make the yield of benzylic radicals (mostly methylbenzyl) enhanced, increasing the probability of radical–radical recombination on PAH formation. In the ethylbenzene flame, two secondary CH bonds in the ethyl site are much easier to be abstracted than primary CH bonds in methyl sites of o-xylene. The different bond dissociation energies (BDEs) depended on the aromatic structure can change the distribution of the intermediate species in fuel decomposition, which can result in either an increase or decrease of PAH formation. Additionally, the weak benzylic CC bond makes the initiation of ethylbenzene decomposition easier, which could also explain the fated PAH formation in contrast with toluene and o-xylene. The experimental and kinetic analysis for C8H10 aromatics and toluene conducted in the present study contributed a deep insight into the PAH formation of aromatics fuels.

Predictive kinetics on the formation and decomposition of ethylbenzene

The kinetics of reactions over the ethylbenzene surface were studied by using ab initio transition state theory (TST) based master equation methodologies. The variable reaction coordinate TST (VRC-TST) approach was employed to obtain high pressure limit rates for barrierless channels, including C7H7+CH3, C6H5+C2H5, C6H5CHCH3+H, and C6H5CH2CH2+H. Interaction potentials between each pair of fragments were simply simulated with CASPT2/cc-pVDZ calculations and scaled by reference to QCISD(T)/CBS energies. The larger basis set, cc-pVTZ, was tested to have only a very limited improvement on the final kinetics. For benzyl+CH3 recombination, addition to benzylic-site forming ethylbenzene dominates overwhelmingly over addition to ortho- and para-sites forming o-methylbenzyl and p-methylbenzyl, respectively. For C6H5CHCH3+H recombination, addition to benzylic-site also dominates over addition to sites at the aromatic ring. Present predictions, from a theoretical perspective, demonstrate strong preference for the CC dominance in ethylbenzene decomposition. The quite good agreement with earlier studies lend confidence to present predictions. More importantly, our kinetic predictions imply that it could probably introduce large uncertainties if simply using kinetic parameterizations of toluene in modeling study of larger alkylbenzenes. The ethylbenzene system should serve as a better and safer reference.

Gas-phase photocatalytic decomposition of ethylbenzene over perlite granules coated with indium doped TiO2

Doped indium–TiO2 mesoporous photocatalysts were synthesized by a controlled sol–gel process. The catalysts were characterized by XRD, N2 physisorption, UV–Vis-DRS, Photoluminescence and Raman spectroscopies. The indium–TiO2 semiconductors were immobilized on perlite granules by a simple coating method and examined by SEM-EDS. Photocatalytic activity of the In–TiO2/perlite materials was evaluated by the decomposition of ethylbenzene in moist air in a plug-flow photoreactor with a concentric cylindrical configuration, under 254 or 365nm irradiation. Ethylbenzene was substantially decomposed by oxidation in an air steam flowing over the In-doped coated/perlite granules. The decomposition rate of ethylbenzene may be attributed to the presence of indium, which can increase surface phenomena and sensitize the response of the semiconductors to the 365nm UV irradiation. The materials with indium content show enhanced decomposition rates in contrast to the undoped materials. The study indicates that the immobilized In–TiO2/perlite photocatalysts may be a practical way to decompose volatile organic compounds in a stream of moist gas.

Study for Pyrolysis of Ethylbenzene and Xylene under Supercritical Pressure

Under the supercritical pressure, the pyrolysis reactions of ethylbenzene and xylene were investigated by using the continuous flow device. At the pressure of 4 MPa and the different temperatures of 700, 750 and 780 ℃, the pyrolysis gaseous products were analyzed by online gas chromatography for ethylbenzene and xylene, while their liquid products were quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS). It is found that the gaseous products of ethyl- benzene decomposition are similar to those of xylene, while the liquid products of ethylbenzene and xylene decomposition are quite different, of which the major products are aromatic hydrocarbons. The experiment reveals that the higher the pyro- lysis temperature is, the higher the conversion ratio will be for ethylbenzene and xylene. On the other hand, the conversion ratio of ethylbenzene is higher than that of xylene at the same temperature in experiment. From the experimental observation, we conclude that the pure aromatic hydrocarbon does not cause serious coking during the cracking process, owing to the low pyrolysis. Theoretical calculations are performed to obtain the bond energies for the different C—C or C—H bond types in side alkyl groups of ethylbenzene and xylene, by using density functional theory (DFT) method at the BHandHLYP/6-31+ G(d, p) level. The bond energies calculated in this study agree well with those available from literature. It is found that the weakest bond is the C—C bond in the ethyl group of ethylbenzene, with a bond energy of 313.1 kJ/mol. This value is much smaller than the smallest bond energy of 393.2 kJ/mol of the C—H bond in the substituted methyl group in xylene. The weakness of the C—C bond in ethylbenzene thus leads to the fact that the pyrolysis of ethylbenzene is much easier than that of xylene. The theoretical results predict a higher conversion ratio of ethylbenzene than that of xylene. So the calculation gives a good explanation for the experimental phenomenon. Finally, the study in this work shows a new and important insight to the coking mechanism for the hydrocarbon fuels. Keywords ethylbenzene; xylene; pyrolysis; supercritical; coke; bond energy

Theoretical investigation into the low-temperature oxidation of ethylbenzene

The classical topic on the oxidation of alkylbenzene has been revisited via performing accurate theoretical calculations to address the salient features for the initial oxidation of ethylbenzene. Potential energy surfaces are mapped out for all possible reactions in the systems of (1-phenylethyl+O2 and 2-phenylethyl+O2). Reaction rate constants at the high-pressure limit are calculated for all possible reactions in these two systems. Direct H abstraction from 1-phenylethyl radical by oxygen molecule appears to be an important route for the formation of styrene from the oxidation of ethylbenzene. Concerted elimination of HO2 is predicted to contribute significantly the production of styrene from system of 2-phenylethyl+O2; especially at the atmospheric pressure and intermediate temperatures. Formation of the other major experimental product, benzaldehyde, is attributed to the unimolecular decomposition of C6H5CH2(O)CH3 rather than to unimolecular isomerisation of the two initial peroxy adducts. Kinetic and mechanistic data presented herein are instrumental for better understanding of the oxidative decomposition of ethylbenzene, i.e., major constituents of commonly formulated fuel surrogates.

Experimental and modeling investigation on premixed ethylbenzene flames at low pressure

Three premixed ethylbenzene/O2/Ar flames with equivalence ratio (φ) of 0.75, 1.00, 1.79 were studied at low pressure (4.0kPa) to represent the lean, stoichiometric, and rich ethylbenzene flames. Flame species were identified using synchrotron vacuum ultraviolet photoionization mass spectrometry, and their mole fractions were evaluated. The maximum mole fractions of hydrocarbon intermediates were observed to increase with φ increasing. A kinetic model including 176 species and 804 reactions was developed with detailed submechanisms of ethylbenzene and toluene. The validation of the model was made by simulating the measured mole fractions of flame species, showing good agreement in reproducing the mole fractions of most observed species. Furthermore, rate of production analysis reveals the main formation and consumption channels of some key hydrocarbon intermediates involved in ethylbenzene decomposition and PAHs formation. The main reaction channels of these species in the rich flame have salient differences with those in the lean flame, indicating the different chemistry between the pyrolysis dominated and oxidation dominated circumstance, while the chemistry in the stoichiometric flame is more similar to that in the lean flame. Furthermore, reactions involving phenyl and benzyl are concluded to be critical for PAHs formation in the rich ethylbenzene flame.

Photocatalytic Activity Dependence on the Structural Orientation of MOCVD TiO2 Anatase Films

This paper is concerned with the study of metallorganic chemical vapor deposition (MOCVD) anatase film growth, with the aim of assessing the relationship between the surface morphology and the photocatalytic properties of the films, particularly their relation to the decomposition of ethylbenzene at in humidified air. We have found an interesting relationship between the structural properties of films deposited by MOCVD at for different deposition times. We observed the maximum efficiency of films in the thickness range of 600–900 nm, while in a higher thickness, this activity relentlessly decreased. From atomic force microscopy analysis, it was ascertained that this reduction was not due to a decrease in the superficial area, which showed a constant roughness of films thicker than 600 nm. From X-ray diffraction analysis, the films always grew in the anatase structure, but the thicker the films, the more pronounced the (100) preferred orientation. Thanks also to theoretical considerations, it was concluded that the activity decrease in the 900–1800 nm thickness range was due to the particularly strong increase in the (100) plane-oriented crystallites recorded in the same range, causing a decrease in surface energy and, contemporaneously, a hindering effect on photocatalytic activity.

Investigation of the Kinetics of Ethylbenzene Pyrolysis Using a Temperature-Scanning Reactor

A new technique of gathering kinetic data has been examined. This involved gathering raw data at the end of a plug-flow reactor undergoing temperature ramping. The data acquired in this way was made to yield many isothermal sets of rate data suitable for fitting to candidate rate expressions. This technique was applied to the thermal decomposition of ethylbenzene. The resulting fit to a rate expression proposed previously in the literature was good. The parameters obtained compare well with literature values, and our fitted rate expressions yield calculated conversions in agreement with those reported in the literature. We believe that temperature-scanning methods used in experimental reactors yield correct rate data and are considerably faster for rate data acquisition than conventional isothermal reactors.

Adsorption and thermal decomposition of ethylbenzene and styrene on Pt(111) studied by UPS and XPS

The interaction of ethylbenzene (EB) and styrene with Pt(111) was studied by UPS and XPS for adsorption temperatures between 135 and 870 K. Below 350 K, styrene chemisorbs strongly and the work function decreases by more than 2 eV indicating strong polarization or charge transfer. This is accompanied by different bonding shifts of the π and σ orbitals towards lower binding energy. After saturation of the chemisorbed layer, physisorption and finally condensation in the form of clusters is observed. The isosteric heats of adsorption for physisorbed and condensed styrene are 61 and 58.5 kJ mol −1, respectively. The first EB layer dissociates into chemisorbed styrene and hydrogen atoms. The subsequent physisorbed and condensed layers consist of undissociated EB. Upon annealing in an EB or styrene atmosphere, chemisorbed γ-styrene polymerizes at about 400 K with a saturation coverage slightly above one monolayer. Upon further annealing the layer starts to decompose and beyond 700 K it forms a graphitic coke layer. Annealing of a γ-styrene layer without further gas admission yields the same species but with lower coverages.

Hydrocarbon and lipid oxidation in micro heterogeneous systems formed by surfactants or nanodispersed Al 2O 3, SiO 2 and TiO 2

The effect of surfactants and micro dispersed solid oxides on the kinetics and mechanism of hydrocarbon (ethylbenzene, limonene, β-carotene) and lipid (sunflower oil triacylglycerols) liquid phase oxidation by molecular oxygen have been studied. Ionic surfactants sodium dodecylsulphate (SDS) and cetyltrimetyl ammonium bromide (CTAB) were found to affect the rate and mechanism of hydroperoxide decay and consequently the rate of the ethylbenzene and limonene oxidation. In the case of β-carotene, which does not form hydroperoxides in the course of oxidation; the surfactants do not affect the β-carotene consumption rate. Anionic surfactant SDS is found to be a catalyst for the heterolytic decay of hydroperoxides. In the case of α-phenyl ethyl hydroperoxide, the decay reaction catalyzed by SDS yields phenol that is an acceptor of free radicals. So the ethylbenzene oxidation is completely inhibited in the presence of SDS. The same effect on the ethylbenzene oxidation and its hydroperoxide decay was found to be caused by nanodispersed Al 2O 3. Cationic surfactant CTAB as a catalyst causes the decomposition of ethylbenzene and limonene hydroperoxides via free radical formation that results in acceleration of hydrocarbon oxidation. Solid oxides SiO 2, TiO 2 non-ionic ethoxylated hydrocarbons, and sodium bis (2-ethylhexyl)sulfosuccinate (AOT) show a slight effect on the hydroperoxide decay and hydrocarbon oxidation rates. The effect of surfactants and cosurfactants on the inhibited oxidation of lipid and hydrocarbons is strongly dependent on the nature of antioxidant and surfactant used.

The effect of lanthanum and zinc ions on the activity of alumina supported nickel–molybdenum catalysts

Activity studies of a series of nickel–molybdenum catalysts incorporated on alumina modified with lanthanum and zinc ions have been performed. Decomposition of isopropyl and diacetone alcohol as well as ethylbenzene decomposition were used as model reactions. The studies of hydrofining activity of catalysts were conducted on a coal liquid in the conditions of a real process at a hydrogen pressure of 9.0 MPa and at the temperature of 400°C. Support modification with lanthanum and zinc ions affects the catalysts activity in the applied reactions. Zinc ions either do not change or insignificantly increase the acidity of the catalyst surface, whereas incorporation of lanthanum ions decreases it considerably. Modified catalysts revealed a higher yield of acetone, both in the reaction of isopropyl and diacetone alcohol decomposition. A very high yield of acetone was obtained for lanthanum modifications. Dehydrogenation activity was higher for the modified catalysts when compared with the unmodified sample. Modification with the two ions caused a decrease in the hydrofining activity of coal liquid with increasing concentration of the modifier. A markedly bigger drop in the hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activity was obtained for samples modified with lanthanum.

Selective decomposition of ethylbenzene in C 8 aromatic compounds

Selective decomposition of ethylbenzene in C 8 aromatic compounds

Synthesis and catalytic performance of Fe-Cr-bimetallosilicate having a pentasil pore structure

Abstract We synthesized Fe-Cr-silicate with a pentasil pore structure. The results from chemical analyses suggest that both iron and chromium are strongly held in the crystal. Chromium in H-Fe-Cr-silicate did not contribute to the formation of the strong acid sites, and it weakened the acidity of strong acid sites formed by iron in H-Fe-Cr-silicate. The thermogravimetry-differential thermal analysis profiles for the following three catalysts, H-Fe-Cr-silicate, Na-Fe-Cr-silicate, and Fe-Cr oxide supported on a silica gel, indicate that it is more difficult for Fe and Cr in the silicate crystal to be oxidized and reduced than those on silica. In propene conversion, on H-Fe-Cr-silicate catalyst, the selectivity to alkenes was high, as compared with the case of H-Fe-silicate catalyst. In ethylbenzene dehydrogenation, Na-Fe-Cr-silicate catalyst showed the highest selectivity to styrene among the three catalysts. On the other hand, the selectivity to the products in ethylbenzene decomposition was high in the region of the relatively low temperature on H-Fe-Cr-silicate catalyst.

Thermal decomposition of ethylbenzene, styrene, and bromophenylethane: UV absorption study in shock waves

Shock wave studies of the pyrolysis of ethylbenzene, isopropylbenzene, tert-butylbenzene, styrene, and 1-bromo-1-phenylethane were performed using UV molecular absorption spectroscopy. By extensive spectral studies over the range 190-330 nm the overlapping absorption continua could be separated. Key observations in ethylbenzene pyrolysis were the dominance of a primary C-C bond split, the comparable fast fragmentation of benzyl radicals in agreement with observations from other benzyl sources, and the evidence for nonnegligible styrene formation. The following rate constants were derived: ethylbenzene ..-->.. CH/sub 3/ + benzyl, k/sub 1/ = 10/sup 15.55/ exp(-306.7 kJ mol/sup /minus/1//RT) s/sup +/minus/1/; styrene ..-->.. benzene + acetylene, k/sub 15/ = 10/sup 11.2/ exp(-244.5 kJ mol/sup /minus/1//RT) s/sup /minus/1/; 1 bromo-1-phenylethane ..-->.. HBr + styrene, k/sub 22/ = 10/sup 12.5/ exp(-160 kJ mol/sup /minus/1//RT) s/sup /minus/1/; benzyl fragmentation rates were identical with results from toluene, benzyl iodide, benzyl chloride, and other benzyl precursors. There is evidence for a dominant C-C bond split in isopropylbenzene and tert-butylbenzene pyrolysis as well.

Shock wave study of benzyl UV absorption spectra: Revised toluene and benzyl decomposition rates

High temperature UV absorption spectra of benzyl radicals were recorded over the range 190–330 nm after shock wave induced thermal decomposition of three different precursor molecules, benzyliodide, benzylchloride, and methyl-benzyl-ketone. These spectra are consistent with “hot” and “cold” spectra of benzyl from laser flash photolysis studies. Benzyl radicals have an unexpectedly low stability; their “fragmentation” rates are characterized by the sum of two components k a +k b , with k a =10 15.3±0.3 exp (−349.6±12 kJmol −1 /RT) s −1 and k b =10 10±0.7 exp(−178±15 kJmol −1 /RT) s −1 measured between 1400 and 1900 K at carrier gas concentrations [Ar]=3±0.3·10 −5 mol cm −3 . Toluene and benzyl absorption profiles have been remeasured over the range 190–305 nm in the shock wave induced decomposition of toluene, and reinterpreted with the new benzyl spectra and “fragmentation” rates. The reaction mechanism is dominated by primary dissociation of toluene forming benzyl + H (rate coefficient k=10 15.3±0.1 exp(−369±6 kJmol −1 /RT) s −1 , 1500–1900 K, [Ar]=3±0.3·10 −5 mol cm −3 ) and by “fragmentation” of benzyl radicals which is about ten times faster. The recombination benzyl + H → toluene and toluene attack by H atoms play only a minor role for the concentrations employed (15≤[toluene]/[Ar]≤1000 ppm). An accurate representation of the observed toluene and benzyl concentration profiles over very wide ranges of conditions was possible using toluene and benzyl decomposition, H + benzyl and H + toluene reaction rates. The reason for the lower “stability” of benzyl radicals compared to toluene, as well as the anomalous properties of their apparent “fragmentation” rates remain to be elucidated. However, a revision of earlier mechanisms for toluene and ethylbenzene decomposition appears necessary.

ChemInform Abstract: The High Temperature Pyrolysis of Ethylbenzene

The thermal decomposition of ethylbenzene has been investigated behind reflected shock waves over the temperature and pressure ranges of 1350–2080 K and 0.25–0.5 atm using a 1.6% C8H10 Ne mixture. Major products of the pyrolysis are C7H8, C7H7, C6H6, C4H2, C2H4, C2H2, and CH4; C8H8 appears throughout the temperature range as a minor product. Comparison of the product profiles obtained by time-of-flight mass spectrometry and the results of model calculations strongly supports the initiation step of β CC bond homolysis for C8H10 dissociation. A 51 kinetic step reaction mechanism with 24 species was formulated to model the temperature and time dependence of the major products observed in our experiments.

The high temperature pyrolysis of ethylbenzene

AbstractThe thermal decomposition of ethylbenzene has been investigated behind reflected shock waves over the temperature and pressure ranges of 1350–2080 K and 0.25–0.5 atm using a 1.6% C8H10  Ne mixture. Major products of the pyrolysis are C7H8, C7H7, C6H6, C4H2, C2H4, C2H2, and CH4; C8H8 appears throughout the temperature range as a minor product. Comparison of the product profiles obtained by time‐of‐flight mass spectrometry and the results of model calculations strongly supports the initiation step of β CC bond homolysis for C8H10 dissociation. A 51 kinetic step reaction mechanism with 24 species was formulated to model the temperature and time dependence of the major products observed in our experiments.

Ethylbenzene Pyrolysis: Benzyl CC or CH Bond Homolysis

AbstractThe thermal unimolecular decomposition of ethylbenzene has been studied by both the very‐low‐pressure pyrolysis and heated single‐pulse shock tube methods in an attempt to resolve a recent controversy as to whether the initial dissociation channel is benzyl C ‐ C, or benzyl C‐H homolysis, Observed decomposition products and mass balance studies lead to the conclusion that up tc 1288K the predominant decomposition channel is benzyl C‐C homolysis. Additional support of this conclusion is provided by a study of isopropylbenzene decomposition by these same methods. Arguments are given which strongly suggest that benzyl C‐H homolysis cannot be the major reaction channel even at temperatures as high as 1600K.