Tert-butylbenzene Research Articles

Interconversion equilibria between tert-butylbenzenes and tert-butyltoluenes

The equilibrium of six positional isomerization reactions in the systems of sterically unhindered tert-butylbenzenes (TBB) and tert-butyltoluenes (TBT) was experimentally studied in the liquid phase over a wide temperature range. The thermodynamic characteristics of the reactions were obtained, their interpretation was given, and the enthalpy of interaction of the (1-TB)-(3-TB) type between the substituents in alkylbenzene molecules was determined on the basis of the experimental and literature data.

Characterization of mixed micelles of structural isomers of sodium butyl benzene sulfonate and sodium dodecyl sulfate by SANS, FTIR spectroscopy and NMR spectroscopy

The mixed systems of sodium dodecyl sulfate (SDS) and sodium salts of n-butyl benzene sulfonate (NBBS), iso-butyl benzene sulfonate (IBBS) and tert-butyl benzene sulfonate (TBBS), as hydrotropes, are studied by Small Angle Neutron Scattering (SANS), Fourier Transform Infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy for the effect of hydrotrope concentration, hydrotrope structure, and temperature on the SDS micelles. The mixed micelle formation of SDS with NBBS is confirmed with the contrast matching technique. NBBS when mixed with SDS replaces some of the SDS molecules from the micelle affecting its size. The hydrotrope structure shows a prominent effect on the dimensions of the mixed micelle. The behavior of NBBS, in the SDS–NBBS mixtures, is different from that of NaCl and is not the same as the salt effect. Higher temperatures result in the formation of smaller SDS–NBBS mixed micelles in the solutions. The FTIR spectroscopy results indicate enhanced gauche/trans conformer ratio of SDS in the mixed micelles unlike the reduction of the ratio in the mixed micelles of a cationic surfactant with NBBS. The up-field chemical shifts of the aromatic protons of the hydrotrope and the methylene protons of surfactant adjacent to ionic headgroup indicate that the hydrotrope resides near the surface of the SDS micelle.

Diluent effect on Sr(II) extraction using di- tert-butyl cyclohexano 18 crown 6 as the extractant and its correlation with transport data obtained from supported liquid membrane studies

The effect of organic diluents on the extraction of Sr(II) from an aqueous nitrate medium (containing a mixture of 2.0 M Al(NO 3) 3 + 0.5 M HNO 3) using di- tert-butylcyclohexano 18 crown 6 (DTBCH18C6) as the extractant was investigated. The diluent effect on the Sr(II) transport rates across supported liquid membranes (SLM) containing DTBCH18C6/diluent as the carrier was also investigated. Though diluents containing DTBCH18C6 alone have shown moderate transport rates, their 1:1 mixture with 1-octanol has shown significant enhancement in transport rates: a 1:1 chloroform–octanol mixture resulted in the highest distribution ratio values though the transport rates were at maximum with a tert-butyl benzene–octanol mixture. The extractability of the metal ion was correlated with Schmidt’s diluent parameter.

Determination of stability constants of lanthanide nitrate complex formation using a solvent extraction technique

Summary For lanthanides and actinides, nitrate complex formation is an important factor with respect to the reprocessing of nuclear fuels and in studies that treat partitioning and transmutation/conditioning. Different techniques, including microcalorimetry, various kinds of spectroscopy, ion-exchange and solvent extraction, can be used to determine stability constants of nitrate complex formation. However, it is uncommon that all lanthanides are studied at the same time, using the same experimental conditions and technique. The strengths of the complexes are different for lanthanides and actinides, a feature that may assist in the separation of the two groups. This paper deals with nitrate complex formation of lanthanides using a solvent extraction technique. Trace amounts of radioactive isotopes of lanthanides were produced at the TRIGA Mainz research reactor and at the Institutt for Energiteknikk in Kjeller, Norway (JEEP II reactor). The extraction of lanthanide ions into an organic phase consisting of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine, 2-bromodecanoic acid and tert-butyl benzene as a function of nitrate ion concentration in the aqueous phase was studied in order to estimate the stability constants of nitrate complex formation. When the nitrate ion concentration is increased in the aqueous phase, the nitrate complex formation starts to compete with the extraction of metal ions. Thus the stability constants of nitrate complex formation can be estimated by measuring the decrease in extraction and successive fitting of an appropriate model. Extraction curves for La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Ho and Er were obtained and stability constants for their nitrate complex formation were estimated. Tb, Tm, Yb and Lu were also investigated, but no stability constants could be determined. The distribution ratios for the metal ions at low nitrate ion concentration were obtained at the same time, showing the effect of lanthanide contraction resulting in decreasing extraction along the series. A clear tetrad effect in the lanthanide group was also found.

Comparison of the Solvents n‐Hexane, tert‐Butyl Benzene and Toluene in the Polymerization of 1,3‐Butadiene with the Ziegler Catalyst System Neodymium Versatate/Diisobutylaluminum Hydride/Ethylaluminum Sesquichloride

The influence of the solvents n‐hexane, tert‐butyl benzene (TBB) and toluene on the Nd‐catalyzed polymerization of butadiene was studied. Special emphasis was placed on polymerization kinetics and on the evolution of molar masses and molar mass distributions with monomer conversion. Distinct differences were found between the three solvents. From the polymerization kinetics there is evidence which supports Porri's view on the competitive coordination between aromatic solvents and butadiene to active Nd‐sites. In addition, there are indications for the irreversible transfer of benzyl‐H‐atoms from toluene to active allyl‐anionic polymer chains. The evolution of molar mass distributions with monomer conversion provides evidence for the existence of two active catalyst species which are present in all three solvents. One of these two species is highly reactive (“hot”) and short‐lived. This species generates BR with high molar mass. The second species has a low reactivity and lives throughout the entire course of the polymerization. In n‐hexane the “hot”, short‐lived species is present only at the start of the polymerization, whereas in TBB and toluene, the short‐lived species becomes evident at monomer conversion>10% and is constantly (re)generated. Cis‐1,4‐contents determined at final monomer conversion are not in line with other available studies in this field.

The vapour phase reaction of tert-butylbenzene and tert-butyl acetate over Al-MCM-41 molecular sieves

Hydrothermal synthesized Al-MCM-41 with different Si/Al ratios (30, 54, 78 and 107) were characterized by XRD, ICP-AES, BET, acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR techniques. The catalytic activity of these materials was tested in the vapour phase alkylation of tert-butylbenzene (TBB) with tert-butyl acetate (TBA) in the temperature range 200–400 °C. The products were found to be 1,4-di- tert-butylbenzene (1,4-DTBB), 1,3-di- tert-butylbenzene (1,3-DTBB), 4-acetyl- tert-butylbenzene (4A-TBB), 3-acetyl- tert-butylbenzene (3A-TBB), 2-acetyl- tert-butylbenzene (2A-TBB) and 2-acetyl-1,4-di- tert-butylbenzene (2A-1,4-DTBB). The selectivity towards 1,3-DTBB increased with increase in temperature, conversely the selectivity of 1,4-DTBB decreased. The selectivity to 4A-TBB, which is higher than that of other compounds, also increased with increase in temperature. The effect of temperature, flow rate and feed ratio was also studied over all the catalysts to arrive optimum conditions for higher conversion with product selectivity. The effect of time-on-stream was studied over all the catalysts and the results are discussed.

Osmotic and Activity Coefficients of Short-Chain Alkyl Benzene Sulfonates by Vapor Pressure Osmometry

Osmotic coefficients φ for aqueous solutions of sodium salts of n-butyl benzene sulfonate (NaNBBS), isobutyl benzene sulfonate (NaIBBS), tert-butyl benzene sulfonate (NaTBBS), n-propyl benzene sulfonate (NaPBS), ethyl benzene sulfonate (NaEBS), and p-toluene sulfonate (NaPTS) have been determined as a function of their molality m at 40 °C, 45 °C, and 50 °C by vapor pressure osmometry. Plots of φ versus 1/m show breaks yielding minimum hydrotropic molality (MHM) of the six hydrotropes. Burchfield and Woolley's model of micelle formation of ionic surfactants gives an apt representation of the experimental data.

Intrinsic bioremediation of MTBE-contaminated groundwater at a petroleum-hydrocarbon spill site

An oil-refining plant site located in southern Taiwan has been identified as a petroleum-hydrocarbon [mainly methyl tert-butyl ether (MTBE) and benzene, toluene, ethylbenzene, and xylenes (BTEX)] spill site. In this study, groundwater samples collected from the site were analyzed to assess the occurrence of intrinsic MTBE biodegradation. Microcosm experiments were conducted to evaluate the feasibility of biodegrading MTBE by indigenous microorganisms under aerobic, cometabolic, iron reducing, and methanogenic conditions. Results from the field investigation and microbial enumeration indicate that the intrinsic biodegradation of MTBE and BTEX is occurring and causing the decrease in MTBE and BTEX concentrations. Microcosm results show that the indigenous microorganisms were able to biodegrade MTBE under aerobic conditions using MTBE as the sole primary substrate. The detected biodegradation byproduct, tri-butyl alcohol (TBA), can also be biodegraded by the indigenous microorganisms. In addition, microcosms with site groundwater as the medium solution show higher MTBE biodegradation rate. This indicates that the site groundwater might contain some trace minerals or organics, which could enhance the MTBE biodegradation. Results show that the addition of BTEX at low levels could also enhance the MTBE removal. No MTBE removal was detected in iron reducing and methanogenic microcosms. This might be due to the effects of low dissolved oxygen (approximately 0.3 mg/L) within the plume. The low iron reducers and methanogens (<1.8×103 cell/g of soil) observed in the aquifer also indicate that the iron reduction and methanogenesis are not the dominant biodegradation patterns in the contaminant plume. Results from the microcosm study reveal that preliminary laboratory study is required to determine the appropriate substrates and oxidation-reduction conditions to enhance the biodegradation of MTBE. Results suggest that in situ or on-site aerobic bioremediation using indigenous microorganisms would be a feasible technology to clean up this MTBE-contaminated site.

Sorption of methyl tert-butyl ether and benzene in fine-grained materials from northern Illinois and the Chalco Basin, Mexico

Methyl tert-butyl ether (MTBE) is a gasoline oxygenate additive used to enhance gasoline combustion by lowering carbon monoxide and hydrocarbon emissions, thus reducing air pollution. However, it has been identified as the second most common volatile organic contaminant of urban aquifers in the United States. Methyl tert-butyl ether has also been blended into two types of gasoline sold in Mexico by the state oil company (Petrleos Mexicanos) but is currently not monitored in groundwater. Early research on MTBE determined that it is unable to sorb to soils and sediments. The objective of this study is to determine if fine-grained materials with high organic matter (0.25–15.3%) have the potential for sorption of MTBE. The experiment consisted of sorption isotherms of loess from DeKalb, Illinois, and lacustrine sediments from Chalco, Mexico. Experiments were performed with various concentrations of MTBE and benzene (10, 50, 100, 500, and 1000 g/L) at 25C and 10C. Methyl tert-butyl ether showed a retardation factor (R) as high as 1.856 0.0130 for lacustrine sediments and 1.095 0.0010 for loess at 25C. Benzene showed retardation factors as high as 1.996 0.0150 in lacustrine sediments and 1.775 0.0050 in loess at 25C. These results showed that sorption, and therefore, the retardation of MTBE in groundwater, is possible in fine-grained materials especially with high organic matter. This research increases the understanding of the fate and transport of MTBE and improves the knowledge to implement the optimal remediation method for sites contaminated by MTBE.

Berkelium nitrate complex formation using a solvent extraction technique

Summary The extraction of Bk(III) into an organic phase consisting of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine, 2-bromodecanoic acid and tert-butyl benzene as a function of nitrate ion concentration in the aqueous phase was studied in order to determine the stability constants of the formation of Bk nitrate complexes. Increasing the nitrate ion concentration in the aqueous phase will increase the nitrate complex formation and thus the extraction of metal ions will decrease. Measuring this decrease in distribution ratio and fitting the data points with an appropriate model gives the stability constants of the Bk nitrate complex formation.

Influence of pore structure and pretreatments of activated carbons and water effects on breakthrough dynamics of tert-butylbenzene

Several activated carbons differently pretreated (de-ashed, oxidized, reduced, wetted, frozen, and dried) were investigated using static (equilibrium adsorption of nitrogen and benzene) and dynamic ( tert-butylbenzene (TBB)) adsorption methods. Treatments of carbons at relatively mild conditions leading to not great changes in their textural characteristics affect the TBB breakthrough concentration because of changes in the chemistry of the surfaces (oxidized or reduced) and the presence of water in airstream or pre-adsorbed on carbon beds. Oxygen-containing functionalities at a carbon surface change condition of competitive adsorption of nonpolar TBB and polar water molecules. Calculations of distribution functions of adsorption potential ( A), energy ( E), Gibbs free energy (Δ G) of adsorption of benzene and TBB and effective adsorption (first-order) rate pseudoconstant β e over different ranges of relative exit TBB concentration c ( t ) / c 0 (from ≈ 10 −5 to 0.01–0.4) reveal nonlinear effects caused by the size of carbon granules, the pore size distributions, the presence of water, oxidation or reduction of the surfaces and other treatments resulting in distribution functions f ( y ) with nonzero intensity in relatively broad ranges of the A, E, Δ G, and β e values. There are many factors affecting the breakthrough parameters; therefore, simple linear relationships between these parameters and the structural characteristics ( S BET , S DS , V p , and V DS ) are not observed.

Study of nitrate complex formation with trivalent Pm, Eu, Am and Cm using a solvent extraction technique

Summary The separation of actinides and lanthanides is an important question in the treatment of spent nuclear fuel in the transmutation concept. To find an efficient and well functioning separation process it is necessary to study the chemistry of the elements in the two groups in different aqueous media. The stability constants of the nitrate complex formation with Pm, Eu, Am and Cm were determined using solvent extraction. The extraction was studied using the synergistic system of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine and 2-bromodecanoic acid in tert-butyl benzene. As the nitrate ion concentration in the aqueous phase was increased, a decrease in separation between actinides and lanthanides was seen owing to complex formation between the different elements and the nitrate ions.

Vapor phase reaction of tert-butylbenzene with isopropyl acetate over mesoporous Al-MCM-41 molecular sieves

The vapor phase reaction of tert-butylbenzene (TBB) with isopropyl acetate (IPA) has been studied over mesoporous Al-MCM-41 (Si/Al=30, 51, 72, and 97) from 200 to 350 °C. Catalysts were synthesized hydrothermally and characterized by XRD, FT-IR, BET (surface area), and 29Si, 27Al MAS-NMR techniques. Conversion of TBB decreases with the increase in temperature. The activity of these catalysts followed the order Al-MCM-41 (30) > Al-MCM-41 (51) > Al-MCM-41 (72) > Al-MCM-41 (97). The catalysts with less Si/Al ratios (Si/Al=30 and 51) showed higher activity than the other catalysts. The reaction was observed to yield alkylated and acylated products namely 3-acetyl-4-isopropyl-tert-butylbenzene (3A-4ITBB), 4-acetyl-tert-butylbenzene (4-ATBB), 4-isopropyl-tert-butylbenzene (4-ITBB), Isopropylbenzene (IPB), and 2-acetyl-isopropyl benzene (2A-IPB). Both the alkylation and acylation reaction can be accounted by the nature of acid sites in the catalyst. The selectivity to 3A-4ITBB, 4-ATBB, and IPB increased with increase in temperature, whereas, the selectivity to other products decreased. Increase in the feed ratio increased the conversion, indicating the preferential adsorption of IPA on the catalyst surface. The time-on-stream studies with Al-MCM-41 (30) showed gradual decrease in conversion with the increase in stream was observed after 5 h.

Thermally induced homolytic scissions of interunitary bonds in a softwood lignin solution: A spin-trapping study

Unstable chemical species, that is, radicals generated by the thermal treatment of a dimethyl sulfoxide (DMSO) solution of the lignin of a softwood, Yezo spruce (Picea jezoensis Carr.), were studied in detail with an electron spin resonance (ESR) method combined with a spin-trapping technique. An unstable secondary carbon radical (∼CH ·) in the solution was trapped as a stable nitroxide spin adduct [R(NO ·)CH∼ (R = tert-butyl benzene)] when the DMSO solution was heat-treated in the presence of a spin-trapping reagent [2,4,6-tri-tert-butylnitrosobenzene (BNB)] at about 40°C. This meant that alkyl phenyl ether bonds (∼CHO-phenyl), known as interunitary lignin bonds, were homolytically scissioned by the thermal treatment in the lignin solution. A detailed analysis of the ESR spectrum revealed that three kinds of radicals—primary (∼CH2 ·), secondary (∼CH ·), and tertiary (∼C ·) carbon radicals—were trapped as stable spin adducts at about 60°C, although the phenoxy radical (PhO ·) was not trapped by the BNB spin trap as the counter radical of the secondary carbon radical. This suggested that a fairly large steric hindrance existed between the so-called guaiacoxy radical with a methoxy group in the ortho position and the BNB molecule bearing two butyl groups as bulky moieties in the ortho positions. However, the phenoxy radicals in the lignin solution were stable up to about 60°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2136–2141, 2004

Extraction Behavior of the Synergistic System 2,6‐ bis ‐(Benzoxazolyl)‐4‐ Dodecyloxylpyridine and 2‐Bromodecanoic Acid Using Am and Eu as Radioactive Tracers

In this study, the extraction properties of a synergistic system consisting of 2,6‐bis‐(benzoxazolyl)‐4‐dodecyloxylpyridine (BODO) and 2‐bromodecanoic acid (HA) in tert‐butyl benzene (TBB) have been investigated as a function of ionic strength by varying the nitrate ion and perchlorate ion concentrations. The influence of the hydrogen ion concentration has also been investigated. Distribution ratios between 0.03–12 and 0.003–0.8 have been found for Am(III) and Eu(III), respectively, but there were no attempts to maximize these values. It has been shown that the distribution ratios decrease with increasing amounts of ClO4 −, NO3 −, and H+. The mechanisms, however, by which the decrease occurs, are different. In the case of increasing perchlorate ion concentration, the decrease in extraction is linear in a log–log plot of the distribution ratio vs. the ionic strength, while in the nitrate case the complexation between nitrate and Am or Eu increases at high nitrate ion concentrations and thereby decreases the distribution ratio in a non‐linear way. The decrease in extraction could be caused by changes in activity coefficients that can be explained with specific ion interaction theory (SIT); shielding of the metal ions, and by nitrate complexation with Am and Eu as competing mechanism at high ionic strengths. The separation factor between Am and Eu reaches a maximum at ∼1 M nitrate ion concentration. Thereafter the values decrease with increasing nitrate ion concentrations.

Small-Angle Neutron Scattering Studies of Mixed Cetyl Trimethylammonium Bromide−Butyl Benzene Sulfonate Solutions

The effect of hydrotropes, sodium salts of butyl benzene sulfonate (Na-BBS), viz., n-butyl benzene sulfonate (Na-nBBS), iso-butyl benzene sulfonate (Na-iBBS), and tert-butyl benzene sulfonate (Na-tBBS), on microstructures of cetyl trimethylammonium bromide (CTAB) in aqueous solutions has been studied using small-angle neutron scattering (SANS) and viscosity changes. The viscosity of CTAB solutions increased with the addition of the hydrotropes, but differently with different isomers. This behavior is attributed to the structural differences in the hydrotropes. The SANS studies indicated the growth of the CTAB micelles on the addition of the hydrotropes while the micellar shape changed from sphere to ellipsoid depending upon the structure of the hydrotrope. Na-nBBS showed the highest aggregation number and a lower fractional charge on the micelles as compared to the sterically hindered Na-tBBS, at the same concentration.

Porous Structure of Activated Carbons and Tert-butylbenzene Breakthrough Dynamics

The structural and adsorptive characteristics of six activated carbons were studied by means of nitrogen and benzene adsorption and water desorption. Tert-butylbenzene (TBB) breakthrough dynamics was analyzed by using several integral equations solved with a regularization/singular-value decomposition procedure. TBB interaction with texturally different activated carbons with the presence of preadsorbed or adsorbed water under dynamic conditions was illustrated by the breakthrough plots handled with several models. The influence of the type of activated carbons, their pore size distributions, water vapor, and TBB flow rate on the breakthrough times (tb) and the dynamic capacity of the carbon beds has been explored with better results for a carbon sample possessing a maximal contribution of mesopores at half-width x>1.5 nm among the carbons studied (which also appears on benzene adsorption) and a major contribution of microporocity as VDS/Vp≈0.88 and SK/SBET≈0.15. Another adsorbent, which is characterized by a similar total porosity but a larger micropore volume, a smaller contribution of mesopores (SK/SBET≈0.08), greater total and miroporous specific surface areas, and greater intensity of the pore size distribution at x<1.5 nm, shows the second result in dynamic TBB retention.

MINOR ACTINIDE PARTITIONING BY LIQUID–LIQUID EXTRACTION: USING A SYNERGISTIC MIXTURE OF BIS(CHLOROPHENYL)-DITHIOPHOSPHINIC ACID AND TOPO IN A HOLLOW FIBER MODULE FOR AMERICIUM(II)–LANTHANIDES(III) SEPARATION

Regarding the difficult selective extraction of trivalent actinides over fission lanthanides from acidic media, we performed several separation tests in hollow fiber modules. Using a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid and tri-n-octyl phosphine oxide in tert-butyl benzene, tests on extraction, lanthanide scrubbing, and stripping were performed. Up to 99.99% americium could be extracted from 0.5 kmol/m3 nitric acid, with approximately one third of the lanthanides being co-extracted. Mass transfer calculations using a consistent set of input data showed good agreement with the experiments. The influence of operating mode on extraction efficiency was very pronounced. This is discussed based on the calculations.

Characterization of Interaction between Butylbenzene Sulfonates and Cetyl Pyridinium Chloride in a Mixed Aggregate System

Surface active short chain alkyl benzene sulfonates, which are known as hydrotropes, interact electrostatically as well as hydrophobically with cationic surfactants. The mixtures of butyl benzene sulfonate (BBS-) with cetyl pyridinium chloride (CPyCl), as shown by surface tensiometry, rheological techniques, and IR and NMR spectroscopy form rodlike micelles or vesicles. These microstructures give rise to highly viscous solutions even at very low concentrations in the millimolar region. The CPy+/BBS- complexes also show similar behavior in the absence of electrolytes. The steric hindrance due to the butyl group to the interaction with CPyCl is at a maximum with tert-butyl benzene sulfonate (TBBS-) as compared to n-butyl benzene sulfonate (NBBS-) and iso-butyl benzene sulfonate (IBBS-). The molecular interactions between surfactant/hydrotrope pairs are simulated using the MM2 force field in the presence and absence of water. The presence of water reduces the electrostatic interaction by solvation and reinfo...

Modelling of the pyrolysis of tert-butylbenzene in supercritical water

The thermal decomposition of tert-butylbenzene (TBB) in supercritical water (SCW) was investigated. From experimental data of the overall rate and formation of 30 products (more than 50 experiments; T=500–540°C, p=5–25 MPa, five different environments including SCW) and assuming a free radical mechanism, a high pressure reaction model was developed on the basis of a chemical mechanism. The model, which ultimately consists of 171 elementary reactions (ER), and the chemical mechanism, which identifies the reaction paths for the formation of the main products, were evaluated in an interactive process. For the calculation of the entire set of 342 coefficients of the model, an optimisation method was applied to solve the ‘inverse problem’, using: (1) as initial values all available kinetic data at normal pressure; (2) best estimates for the remaining coefficients, considering limits for the different types of ER; (3) ‘punishment functions’, which force the parameters to vary only within certain limits. Model simulations show reasonable agreement with experimental data. The main difference of the reaction in SCW and at low pressure in an inert environment is the strong inhibition of the overall reaction by a factor of 1000. Simulations indicate that mainly radical decomposition reactions are responsible for this effect. It is assumed that a cage effect of water molecules reduces the reactivity of these species. Also, the pressure dependence of the different types of ER is discussed. The product spectra of the reaction in SCW has a greater variety than at 0.1 MPa and below. Simulations show that this is caused by a promotion of substitution reactions and the suppression of decomposition reactions at SCW conditions. Thus, the difference of the decomposition of TBB in SCW regarding the product spectra to the reaction at normal conditions is mainly a pressure effect. These results seem to be of general significance for free radical reactions. They are in agreement with previous studies of the pyrolysis of ethyl-benzene in SCW as well as in inert conditions at atmospheric pressure.