Abstract  A simple procedure for the determination of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), ethyl butyl ether (EBE), tert-amyl methyl ether (TAME), benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using headspace (HS) solid-phase microextraction (HS-SPME) was developed. The analysis was carried out by gas chromatography (GC) equipped with flame ionization detector (FID) and 100% dimethylpolysiloxane fused capillary column. A 2(7-4) Plackett-Burman design for screening and a central composite design (CCD) for optimizing the significant variables were applied. Fiber type, extraction temperature, sodium chloride concentration, and headspace volume were the significant variables. A 65 Ám poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) SPME fiber, 10 degrees C, 300 g/l, and 20 ml of headspace (in 40 ml vial) were respectively chosen for the best extraction response. An extraction time of 10 min was enough to extract the ethers and BTEX. The relative standard deviation (R.S.D.) for the procedure varied from 2.6 (benzene) to 8.5% (ethylbenzene). The method detection limits (MDLs) found were from 0.02 (toluene, ethylbenzene, and xylenes) to 1.1 Ág/l (MTBE). The optimized method was applied to the analysis of the rivers, marinas and fishing harbors surface waters from Gipuzkoa (North Spain). Three sampling were done in 1 year from June 2002 to June 2003. Toluene was the most detected analyte (in 90% of the samples analyzed), with an average concentration of 0.56 Ág/l. MTBE was the only dialkyl ether detected (in 15% of the samples) showing two high levels over 400 Ág/l that were related to accidental fuel spill.

Abstract  Ethyl tert-butyl ether (ETBE) has emerged as a competitor for methyl tert-butyl ether (MTBE) as an octane enhancer. Several companies are considering the merits of ETBE, made by substituting ethanol for methanol in a reaction with isobutylene. Preliminary tests indicate that this ether may be as good as, and possibly a little better than, MTBE, as an octane enhancer in gasoline. ETBE features a one to two point higher octane rating than MTBE, and it has a lower vapor pressure when it is blended with gasoline. Economics appear to be playing a key role in improving the attractiveness of ETBE. Methanol prices have risen dramatically, increasing the feedstock costs for MTBE producers.

Abstract  Ethyl tertiary butyl ether (ETBE) is being proposed as an additive for use in reformulated gasolines. In this study, experiments were performed to examine the kinetics and mechanism of the atmospheric removal of ETBE. The kinetics of the reaction of ETBE with OH radicals were examined by using a relative rate technique with the photolysis of methyl nitrite to generate OH radicals. With n-hexane as the reference compound, a value of (9.73 +/- 0.33) x 10(012) cm3 molecule-1 s-1 was obtained for the rate constant. The OH rate constant for t-butyl acetate, a product of the oxidation of ETBE, was (4.4 +/- 0.4) x 10(-13) cm3 molecule-1 s-1 at 298 K. The primary products and molar yields for the OH reaction with ETBE in the presence of NO(x) were t-butyl formate (0.64 +/- 0.03), t-butyl acetate (0.13 +/- 0.01), ethyl acetate (0.043 +/- 0.003), acetaldehyde (0.16 +/- 0.01), acetone (0.019 +/- 0.002), and formaldehyde (0.53 +/- 0.04). Under the described reaction conditions, the formation of t-butyl nitrite was also observed. From these molar yields, aroximately 98% of the reacted ETBE could be accounted for by paths leading to these products. Chemical mechanisms to explain the formation of these products are presented.

Abstract  Rate coefficients for the reaction of NO3 with ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE), and tert-amyl methyl ether (TAME) have been determined. Absolute rates were measured at temperatures between 257 and 367 K using the fast flow-discharge (FFD) technique. Relative rate experiments were also performed at 295 K in a reactor equied with White optics and using FTIR spectroscopy to follow the reactions. Rate data from FFD experiments can be presented as follows: k(ETBE) = (2.48 +/- 0.78) X 10(-12) exp [-(1613 +/- 542)/T], k(DIPE) = (2.02 +/- 0.35) X 10(-12) exp [-(1759 +/- 301)/T], and k(TAME) = (1.21 +/- 0.22) X 10(-12) exp [-(1874 +/- 304)/T] (in units of cm(3) molecule(-1) s(-1)). The rate coefficients at room temperature from the FFD experiments are in goad agreement with the corresponding rate coefficients from the relative rate experiments. Products from simulated atmospheric oxidation of the investigated ethers, initiated by the reaction with the nitrate radical, were identified using FTIR spectroscopy. The degradation of ETBE results in tert-butyl formate, tert-butyl acetate, formaldehyde, and methyl nitrate, that of DIPE in acetone, isopropyl nitrate, isopropyl acetate, and formaldehyde, and that of TAME in tert-amyl formate, formaldehyde, and tert-amyl nitrate.

Abstract  Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/polydimethylsiloxane, polydimethylsiloxane/divinylbenzene, and polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30-4600 ng L(-1), within- and between-run precision, as coefficient of variation, <22 and <16%, accuracy within 20% the theoretical level, and limit of detection of 6 ng L(-1) for all the analytes. The influence of the matrix on the quantification of these ethers was evaluated analysing the specimens of seven traffic policemen exposed to autovehicular emissions: using the calibration curve and the method of standard additions comparable levels of MTBE (68-528 ng L(-1)), ETBE (<6 ng L(-1)), and TAME (<6 ng L(-1)) were obtained.

Abstract  This study proposes an azeotropic ETBE/ethanol mixture as a possible oxygenated additive for the formulation of eurosuper-type gasolines. Two eurosuper gasolines with different chemical compositions and well defined characteristics of density, volatility and octane numbers are used. Gasoline formulations containing azeotropic mixtures display an intermediary behavior between that of ETBE (ethyl tert-butyl ether) and ethanol in gasoline blends. Formulations containing this additive offer advantages over ethanol (low volatility and low solubility in water) and ETBE (higher octane number and lower production cost). Gasolines with azeotropic additives show lower Reid vapor pressures (RVPs) than gasolines formulated with ethanol, and therefore low levels of volatile organic compounds, similarly to highly pure ETBE. The use of the azeotropic mixture containing ethanol (renewable, deriving from biomass) and ETBE (produced from ethanol and isobutene) in its formulation is environmentally attractive in industrialized countries due to the need to reduce carbon dioxide emissions.

Abstract  The recent EU directive on renewable energy sources (Directive 2009/28/EC) promotes the use of biofuel and bioliquids that could be produced through chemical processes. These biofuels consist of a biogenic (renewable) part and a non-renewable (fossil or non-biogenic) part. A method to evaluate the renewable and non-renewable energy fractions released during combustion is presented. The method is based on thermochemical criteria of bond dissociation energies and on the knowledge of the molecular structure of reagents and products. Its application to MTBE and ETBE analysis provided results that are close to those published in the directive. In particular, application of the method on these products points out a renewable fractions of 23.7% and 35.9% compared with the 22% and 37% listed by the RED. Moreover, the application of the method to products of the process production of FAME with use of fossil methanol, shows a fraction of non-renewable energy very low. For glycerol this value is 1.6% and for the methyl ester fraction of non-renewable energy depends on the type of molecule but always less than 2.4%. These findings could be used to devise correction criteria for the fiscal mechanisms being applied to these biofuels.

Abstract  Oxygenated fuels are gasolines blended with alcohol or ether additives, The U.S. National Institute of Standards and Technology (NIST) provides eight oxygenated gasoline standard reference materials (SRMs) each containing one of four oxygenates at both the 2.0% and 2.7% oxygen mass fraction levels in 20-mL sealed glass ampules, In this study, ET near-IR and FT Raman spectroscopic methods were investigated to nondestructively identify and quantitate the oxygenate concentration in ampules of SRM gasoline, The samples contained any one of the four SRM oxygenates, MTBE, ETBE, TAME, or ETOH, In addition, dual-oxygenate mixtures were examined. The multivariate, statistical calibration technique, partial least-squares, was employed for both near-IR and Raman data to obtain calibration methods to predict the mass fraction of the oxygenate in these gasoline samples, Both spectroscopic techniques were able to unambiguously identify the oxygen additives and quantitate oxygen concentration to an accuracy within 0.1% oxygen mass fraction.

Abstract  Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and isopropyl tert-butyl ether (IPTBE) have been synthesized for the first time over a non-acid ionic liquid as catalyst and dehydrator with high conversion (> 90%) and selectivity (> 90%) under mild conditions.

Abstract  Solid-phase microextraction (SPME) and gas chromatography/mass spectrometry have been combined for trace-level determination of very polar compounds in water, including the widely used gasoline oxygenates ethanol and methyl tert-butyl ether (MTBE). A relatively simple extraction method using a divinylbenzene/Carboxen/poly(dimethylsiloxane) SPME fiber was optimized for the routine analysis of ethanol and MTBE in groundwater and reagent water. A sodium chloride concentration of 25% (w/w) combined with an extraction time of 25 min provided the greatest sensitivity while maintaining analytical efficiency. Replicate analyses in fortified reagent and groundwater spiked with microgram per liter concentrations of ethanol and MTBE indicate quantitative and reproducible recovery of these and related oxygenate compounds. Method detection limits were 15 microg L(-1) for ethanol, 1.8 microg L(-1) for tert-butyl alcohol, 0.038 microg L(-1) for tert-amyl methyl ether, 0.025 microg L(-1) for ethyl-tert-butyl ether, and 0.008 microg L(-1) for MTBE.

Abstract  The densities and ultrasonic velocity of {ethyl tert-butyl ether (ETBE) + (benzene, toluene, ethylbenzene, isooctane, tert-butyl alcohol, and ethanol)} over the temperature range (288.15 to 323.15) K and atmospheric pressure, have been measured over the whole concentration range. The experimental excess volumes and deviation of isentropic compressibilities data have been analysed in terms of different theoretical models. The gathered data improve open literature related to gasoline additives, and help to understand the ETBE volumetric and acoustic trend into different chemical environment. (C) 2007 Elsevier Ltd. All rights reserved.

Abstract  (Solid/liquid + liquid) phase diagrams at ambient pressure have been determined for the hyperbranched polymer, Boltorn W3000 with alcohols (methanol, ethanol, 1-propanol, 1-hexanol, 1-decanol), or with ethers (tert-butyl methyl ether, tert-butyl ethyl ether), or with hydrocarbons (n-hexane, n-heptane, benzene, toluene) by a dynamic method from T = 240 K to the boiling temperature of the solvent. (Solid + liquid) phase equilibria with immiscibility in the liquid phase were detected for B-W3000 with the alcohols and aliphatic hydrocarbons. The upper critical solution temperatures, UCSTs, were measured for (B-W3000 + 1-hexanol and 1-decanol) systems. The experimental results of (solid + liquid) phase equilibria have been correlated using NRTL equation. © 2010 Elsevier Ltd. All rights reserved.

Abstract  An automated flow calorimeter has been developed for the measurement of high accurate isobaric heat capacities for pure compounds and mixtures over the range 250-400 K and 0-20 MPa. The technique has been checked for different compounds and at different conditions of temperature and pressure and the results have been compared with the literature values available. The conclusion of this comparison is that the new calorimeter can measure heat capacities with an estimated total uncertainty better than 0.5%. This paper report describes the new equipment, its set-up and gives new heat capacity data for toluene and ethyl tert-butyl ether at different temperatures and pressures. (C) 2008 Elsevier B.V. All rights reserved.

Abstract  Possible crystal structures of ethyl-tert-butyl ether (ETBE) were predicted by global lattice-energy minimizations using the force-field approach. 33 structures were found within an energy range of 2 kJmol(-1) above the global minimum. Low-temperature crystallization experiments were carried out at 80-160 K. The crystal structure was determined from X-ray powder data. ETBE crystallizes in C2/m, Z = 4, with molecules on mirror planes. The ETBE molecule adopts a trans conformation with a (CH(3))(3)C-O-C-C torsion angle of 180°. The experimental structure corresponds with high accuracy to the predicted structure with energy rank 2, which has an energy of 0.54 kJmol(-1) above the global minimum and is the most dense low-energy structure. In some crystallization experiments a second polymorph was observed, but the quality of the powder data did not allow the determination of the crystal structure. Possibilities and limitations are discussed for solving crystal structures from powder diffraction data by real-space methods and lattice-energy minimizations.

Abstract  Adapted bacterial consortia from activated sludge mineralized 2.8 mg ethyl tert-butyl ether (ETBE) l-1 h whereas methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) were not attacked. From these consortia, two bacterial strains, identified as Gordona terrae and Rhodococcus equi, were isolated. Both strains used ETBE, but not MTBE or TAME, as sole carbon and energy source. Gordona terrae and Rhodococcus equi completely converted ETBE into tert-butanol (TBA) with degradation rates up to 380 mg ETBE g-1 protein h-1. TBA was mineralized by the ETBE-adapted consortia.

Abstract  Methyl tert-butyl ether (MTBE) is a gasoline oxygenate that has become a significant threat to groundwater supplies across the United States. Due to its physiochemical properties it has proven difficult and costly to remove from contaminated sites. This study was conducted to determine whether the alternative oxygenates (AO)-diisopropyl ether (DIPE), ethyltert-butyl ether (ETBE), tert-amyl methyl ether (TAME), tert-butyl alcohol (TBA), and ethanol (EtOH)--present a more efficient and less costly option from a remediation standpoint. Air stripping, carbon adsorption, and ultraviolet/H sub(2)O sub(2) and O sub(3)/H sub(2)O sub(2) advanced oxidation processes were examined at pilot scale to develop design parameters from which technical and economic comparisons were made for each alternative oxygenate versus MTBE. The experimental results showed that the ether AOs--DIPE, TAME, and ETBE--were each more efficiently and more economically treated than MTBE. The alternative alcohol oxygenates--TBA and EtOH--were less efficiently and less economically treated by the processes studied. The paper details the effects of primary process parameters and properties of individual oxygenates on process efficiency.

Abstract  The Clean Air Act Amendments of 1990 introduced reformulated gasoline legislation, which regulated the composition of gasoline to improve tailpipe emissions and air quality. Oxygenates are adeded in the form of MTBE (methyl tert-butyl ether), ETBE (ethyl tert-butyl ether), ethanol, or methanol to reduce carbon monoxide and unburned hydrocarbon emissions. Aromatic and benzene content is capped to reduce volatile organic compounds (VOCs). The need for faster analysis of fuels in the field has driven the search for new methods to supplement gas chromatography (GC). Petroleum companies and regulatory agencies are using mid-infrared (mid-IR) analyzers over GC because they are fast, accurate, and portable for field use. Unlike GC, the mid-IR method described requires no initial separation of chemical compounds or advanced analytical training for operation.

Abstract  Continued operation of periodic injection of air/ozone microbubbles into groundwater under retail dispensers of gasoline provides a level of protection against low volume releases from vapor or liquid during operation. Four years of operation at spill sites has shown that the ozone targets higher health risk compounds, including aromatic additives (BTEX, naphthalenes, methylbenzenes) and oxygenates (MTBE, ETBE, TBA, TAME). A summary of experiences at numerous sites is presented. Whereas initial remediation of a prior spill may involve short-term use of higher concentrations of oxidant, long-term pulsing requires a balance between maintaining optimal conditions for petroleum compound removal and avoiding impact to nontarget site materials. To evaluate the level of risk of damage, a ranking of structural materials and sensitivity to ozone was compiled from existing sources. The expected concentration of ozone with distance in both gaseous and aqueous forms under microbubble production was compared to materials sensitivity (when available) to prepare a set of standard safety operating procedures. Conditions such as groundwater level beneath grade were found to be an important factor.

Abstract  Mechanism and kinetics of gasphase synthesis of ethyl-tert-butyl ether (ETBE) over Wells-Dawson heteropolyacid H6P2W18O62 in an anhydrous system have been discussed. The rates of ETBE synthesis were measured in a differential reactor for ethanol-isobutene system, far from the limitation by chemical equilibrium. In the pressure range studied, kinetic measurements show that isobutene has an enhancing effect on the reaction while ethanol has an inhibitory one. Catalytic and sorption experiments allowed to formulate the mechanism of ETBE synthesis which assumed isobutene adsorption and oligomerization at the surface of heteropolyacid crystallites and the formation of carbocation using protons sulied from the bulk of catalyst. Kinetic equations were deduced indicating that it is the concentration of protons forming inter-anionic bonds between heteropolyacid anions which determines the catalytic activity of heteropolyacid. (c) 2006 Elsevier B.V. All rights reserved.

Abstract  Multiplicity of steady states can exist in three forms: input multiplicity, output multiplicity, and pseudo-multiplicity, which are described here. Input multiplicity is Likely to be common in reactive distillation and places substantial restrictions on the selection of controlled variables. Output multiplicity is also possible in reactive distillation and also has less significant implications for operation and control as it may influence the choices of control structure and the operating region. Pseudo-multiplicity parallels output multiplicity but is only present in terms of molar inputs. It has only minor implications for operation and control but is an important discovery as it reconciles recent reports of material balance output multiplicity with earlier conjecture which claimed that this was unlikely.

Abstract  Vapor-liquid equilibrium data for the binary systems 2-methylpentane + methyl 1,1-dimethylethyl ether (MTBE), + ethyl 1,1-dimethylethyl ether (ETBE), and + methyl 1,1-dimethylpropyl ether (TAME) are reported at 101.3 kPa, including pure component vapor pressures. The measured systems, which deviate slightly from ideal behavior, can be described as symmetric regular solutions, and only the system 2-methylpentane + MTBE presents an azeotrope. Boiling points are correlated with the Wisniak-Tamir equation.

Abstract  The fuel ether ethyl tert-butyl ether (ETBE) is produced from ethanol and isobutene in liquid phase. Acid ion-exchange resins are used as catalyst. The chemical reaction on the active sites of the solid catalyst (microkinetics) involves adsorption and desorption processes, thus leading to a Langmuir-Hinshelwood-Hougen-Watson or Eley-Rideal type approach. Based on this assumption, both Fite et al. and Sundmacher et al. derived different approaches and evaluated parameter values for them. Fite et al. received their parameters from their own measurements, so the parameters fit the experimental results well. Sundmacher et al. fitted parameters based on experiments of Francoisse and Thyrion. These constants cause a much worse fit to the measurements of Fite et al., however, the approach of Sundmacher er nl. predicts the results as well if its parameters are newly fitted to the data of Fite et al. and our own. If both approaches are applied to the investigations of Francoisse and Thyrion, the predictions are almost equal but differ from the experiment by a factor of two.