Abstract  This paper presents the results of an experimental investigation on ethyl tert-butyl ether (ETBE) liquid-phase synthesis from isobutene (IB) and ethanol (EtOH), catalyzed by an acidic macroreticular ion exchange resin, Amberlyst 15 (A15). The experiments were carried out batchwise in a Parr reactor in the range 323-363 K at 2 MPa for different initial EtOH/IB mole ratios and amounts of catalyst. Data collected at equilibrium gave thermodynamic information which was compared with theoretical calculations using the UNIFAC method. The kinetic results were used to develop a reaction mechanism and a kinetic model. The resin's affinity for polar substances and the strong nonideality of the liquid phase lead to a complex expression, which is valid both in the presence of high and low alcohol concentrations. Simulations performed with this kinetic model agree satisfactorily with the experimental results.

Abstract  Thermodynamic equilibrium constants for the liquid-phase synthesis of ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 40-80-degrees-C (313-353 K) at 1.6 MPa for an initial molar ratio of ethanol to isobutene ranging from 1 to 1.5. To reach etherification equilibrium a macroporous sulphonic acid resin (K-2631, Bayer) was used as a catalyst. The thermodynamic equilibrium constant and the enthalpy, free energy, and entropy changes are given as a temperature function. At 298 K, DELTAH-degrees = -34.8 kJ mol-1. DELTAG-degrees = -11.7 kJ mol-1, and DELTAS-degrees = -77.3 J mol-1 K-1. A comparison with the values obtained for MTBE is also included.

Abstract  This work aims at a better understanding, from the reaction mechanism point of view, of the antiknock effect of two unsymmetrical ethers : tert-amyl methyl ether (TAME) and ethyl tert-butyl ether (ETBE). An experimental investigation of the reactions of equimolecular mixtures of these ethers in the presence of oxygen shows that these ethers oxidize less easily than the alkanes of similar structures. Taking into account the distribution of the primary reaction products at ca. 300 degrees C and by using the techniques of Thermochemical Kinetics due to BENSON et al. for the estimation of kinetic parameters, it has been shown that these ethers do not oxidize according to a ''low'' temperature scheme, like the neighbouring alkanes. Their reaction with O-2 seems to have the characteristics of a thermal degradation and not those of a genuine oxidation. In line with the experimental results, it aears that in the co-oxidation of one of the above-mentioned ethers and a hydrocarbon, the effect of the ether is that of a ''negative catalyst'' transforming reactive radicals, chain carriers of the hydrocarbon oxidation, through a rather complex reaction scheme into unreactive ones, unable to propagate the reaction at a sufficient rate to trigger the auto-ignition reactions, responsible for the occurrence of knock phenomena.

Abstract  EtOH/ETBE azeotropic mixture was separated by pervaporation through films of polyurethaneimides (PUI), i. e., alternating block copolymers varying in their structure only by their oligomeric soft blocks. Pervaporation performances strongly depend on the flexible segments: fluxes on the molecular weight and selectivity towards ethanol on the chemical structure in the decreasing order: PEG, PCL, PCD, PTMG, PPG. In order to correlate selectivity with segment polarity, a new solvatochromic polarity probe that was well soluble in PUI was synthesized. Using 13 solvents covering a wide polarity range, Vis λmax of the photochromic indicator open form was linearly correlated with the ET(30) polarity scale. By illumination of the dissolved dye, PUI polarity was investigated in relation to soft segment nature and size. The very high PUI polarity values and their splitting for highest size segments were assigned to preferential probe solvation by interblock urethane junctions combined with phase segregation. Polarity values consistent with the chemical structure of the flexible segments were provided by similar measurements on suitably end-capped precursors of these segments and were then linearly correlated with the related PUI pervaporation selectivity.

Abstract  Synthesis of ethyl tert-butyl ether (ETBE) from the reaction between ethanol (EtOH) and tert-butyl alcohol (TEA) in the presence of different acid catalysts (KHSO4, NaHSO4, H2SO4, and Amberlyst 15) was investigated at low alcohol grade (mixture of 80 mol % water). Potassium hydrogen sulfate (KHSO4) showed the highest selectivity among the tested catalysts. Other catalysts caused the dehydration of TEA into water (H2O) and isobutene (IB). In the top of the reactive distillation column with total reflux, the condensate was split into two layers. The uer layer contained ETBE with a more than 60 mole fraction.

Abstract  The oxidation of n-heptane and mixtures n-heptane-MTBE (50:50) and n-heptane-ETBE (50:50) has been studied experimentally in a high-pressure jet-stirred reactor in a wide range of conditions covering the low and high temperature oxidation regimes (570-1150 K, 10 atm, phi=1, 0.1% of fuel). The mole fractions of reactants, intermediates and final products have been measured. The influence of the additives on the formation of several pollutants has been addressed. The present results clearly show an influencing effect of MTBE and ETBE on the kinetics of n-heptane oxidation by a reduction of the mixture reactivity in the low temperature regime (570-800K). The results are interpreted in terms of knocking and non-knocking tendencies related to fuel structure and low temperature oxidation mechanism.

Abstract  A new kind of membrane was prepared by blending poly( acrylic acid) with cellulose acetate propionate for the separation of ethyl tert-butyl ether and ethanol mixtures. The properties of the membranes were evaluated by the pervaporation separation of mixtures of ethyl tert-butyl ether/ethanol and the sorption experiments. The experimental results showed that the selectivity and the fluxes of this membrane depend on the blend composition and on that of processed feed mixtures. With respect to temperature, the ethanol fluxes obey the Arrhenius equation. The fluxes increase with the increase of the poly(acrylic acid) content in the blended membrane, the ethanol concentration in the feed, and the experimental temperature. But the selectivity decreases as the poly(acrylic acid) content and the experimental temperature are raised up. When the feed composition is varied, this membrane shows the special characteristics at the azeotropic composition. In the vicinity of th azeotropic point, the minimum values of ethanol concentration in the permeate and in sorption solution are obtained. The swelling ratios increase with an increase in the temperature and the ethanol concentration. The ethanol concentration in the sorption solution is also influenced by the temperature and composition of the mixtures. When the temperature increases, the sorption selectivity of the membrane decreases. (C) 1997 John Wiley & Sons, Inc.

Abstract  This work reports the pervaporative separation of ethanol from ethanol-ethyl ter butyl ether mixtures using a commercial membrane, PERVAP 2256, that previously showed an interesting behavior in the separation of methanol-MTBE mixtures. Pervaporation flux has been obtained and analyzed as a function of feed composition in the range of ethanol concentration of 30-50 wt % and temperature in the range of 50-70degreesC whereas permeate pressure was kept constant in all the experiments and equal to 3 mmHg. Pervaporation fluxes showed an exponential dependence with both variables, that in the case of temperature fitted to an Arrhenius type expression. Achievement of steady state conditions referred to the pervaporation flux needed of long times that depended on the previous history of the membrane; thus new membranes needed a long conditioning period before reaching steady state that was considerably shortened in subsequent changes of the operation conditions.

Abstract  Ethyl tert-butyl ether (ETBE) synthesis from ethanol (EtOH) and tert-butyl alcohol (TBA) was studied with different macroporous and gelular ion exchange resin catalysts. Purolite (CT-124, CT-145H, CT- 151, CT-175 and CT-275) and Amberlyst (15 and 35) ion exchange resins were used for the present work. Effect of various parameters such as catalyst type, temperature, reactants feed molar ratio and catalyst loading were studied for the optimisation of reaction condition. Among the catalysts studied, Purolite CT-124 gave the best results for TBA conversion and selectivity towards ETBE. Kinetic modelling was performed with this catalyst and activation energy and water inhibition coefficient were determined. Heterogeneous kinetic models [e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW)] were unable to predict the behaviour of this etherification reaction, whilst the quasi-homogeneous (QH) model represented the system very well over wide range of reaction conditions.

Abstract  Alternatives to the conventional isobutylene-derived ethers, namely methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), are being explored, e.g., those produced from a combination of the branched C-5 and C-6 olefins with methanol or biomass-based ethanol. The conversion and selectivity of these ethers are thermodynamically limited. This paper, thus, describes the determination and analysis of the equilibrium limitations in the liquid-phase synthesis of two of the three possible isomers of tert-hexyl ethyl ether (THEE) from reactive C-6 olefins and ethanol in the temperature range 298-353 K. The coupled reaction network for either of these two ethers involves two simultaneous etherification and one isomerization reactions, all being reversible. The equilibrium constants for these reactions, experimentally determined from equilibrium composition and the corresponding activity coefficients estimated by the UNIFAC method, decrease in the following order of tertiary olefins: 2M1P > isobutylene > 2,3DM1B aroximate to 2M1B > 2M2P > 2M2B > 2,3DM2B for etherification reactions with ethanol, and (2,3DM1B reversible arrow 2,3DM2B) > (2M1B reversible arrow 2M2B) > (2M1P reversible arrow 2M2P) for the isomerization reactions. This is explained on the basis of the relative stability of these olefins. The developed correlations are used to study the influence of process variables on the equilibrium conversion and selectivity of THEE formation.

Abstract  Vapor phase synthesis of ETBE from ethanol and isobutene has been investigated over US-Y, Beta, and ZSM-5 zeolites with different Si/Al ratios, using Amberlyst-15 as a reference catalyst. The zeolites were characterized by X-ray diffraction and nitrogen adsorption-desorption isotherms at 77 K. Total acidity of the Beta zeolites was determined by ammonia-TPD measurements whereas IR spectroscopy was used to investigate the OH stretching region and evaluate the Bronsted and Lewis acid contents by pyridine adsorption. Beta zeolites, with higher external surface area, were more active than the other zeolites. The highest yields of ETBE were obtained for Beta samples with high Bronsted acid content and low SiOH/AIOHSi ratio. (C) 2001 Academic Press.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Over the period covered by this review many changes have been made to fuel composition. A number of these changes have been made with the intention of improving the environment by altering exhaust emissions. On some occasions it appears that refiners may have removed one hazard only to create another. A typical example is the introduction of oxygenates at the expense of aromatics. Our review shows that this will reduce benzene and aromatic emissions but will increase aldehyde emissions. The use of catalytic converters minimizes many of these fuel effects but in many countries the catalytic vehicle population is small and these fuel changes may have significant effects if the fuels are used in cars not fitted with exhaust treatment devices. Concern grows regarding vehicular emissions as the number of vehicles continues to rise. It becomes even more important that we understand the environmental effects that changing fuel compositions will have. Particularly indicted appe

Abstract  Four gasoline or gasoline-oxygenate blend fuels were used in the evaluation of regulated and unregulated emissions for five test vehicles. The fuels listed below were all prepared from a common base gasoline and were blended to have equal octane ratings. They were Baseline, aromatic-enriched, 10% Ethanol blend, 16.4% Methyl tertiary-butyl ether (MTBE) blend, and 19.1% Ethyl tertiary-butyl ether (ETBE) blend. The five test vehicles represented different types of emissions control technology: pre-catalyst, oxidation catalyst, three-way catalyst with closed-loop carburetor operation and an air pump, three-way catalyst with throttle body fuel injection, and three-way catalyst with port fuel injection. Each vehicle was operated with each fuel over the Federal Test Procedure (including evaporative emissions) for a total of 15 tests per vehicle. Several unregulated exhaust emissions were measured including ethylene, 1,3-butadiene, isobutylene, benzene, toluene, o-, m-, and p-xylenes, formaldehyde, acetaldehyde, ethanol, MTBE, and nitrous oxide. In addition, evaporative emissions were analyzed for MTBE, benzene, and ethanol. The emission data from tests using the ethanol, MTBE, and ETBE blends were compared to emissions produced from tests using the aromatic-enriched baseline fuel to determine if there were any statistically significant differences associated with the use of the blends.

Abstract  A 1993 Ford Taurus and a 1995 Chevrolet Achieva were tested using three different fuels: (1) a winter grade (E-10) fuel containing 10% (vol.) 200 proof ethanol, (2) a winter grade (WG) fuel without any oxygen containing compounds, and (3) a summer grade (SG) fuel without oxygenates. Vehicle emissions were characterized at test temperatures of 75 (SG fuel only), 20, 0, and -20 deg F. The vehicles were tested under two simulated malfunction modes: (1) the oxygen (O2 mode) sensor was disconnected and (2) the exhaust gas recirculating valve (EGR mode) was disconnected and plugged. The malfunction modes were not tested simultaneously. The vehicles were tested on the Urban Dynamometer Driving Schedule (UDDS) of the Federal Test Procedure (FTP). Four IM240 test cycles were run after each of the UDDS tests and the exhaust particulate matter (PM2.5 and PM10), from the four IM240 driving cycles were collected on single filters. The gaseous emissions were collected and analyzed for total hydrocarbons, carbon monoxide, oxides of nitrogen speciated (individual) hydrocarbons, speciated (individual) aldehydes, ethanol, methanol, 2-propanol, methyltertiarybutyl (MTBE) ether, and ethyltertiarybutyl (ETBE) ether. Hydrocarbon emissions generally increased as test temperature decreased for both vehicles, fuels, and test modes. The E-10 fuel reduced some emissions and increased others, while disconnecting the O2 sensor increased emissions over the other two modes. The trend for carbon monoxide and oxides of nitrogen emissions showed a general increase in emission rates as the testing temperature decreased. When the O2 sensor was disabled, the trend showed the increasing carbon monoxide emissions and when the EGR valve was disabled it was observed that the oxides of nitrogen emissions generally increased.

Abstract  The catalysis of the etherification of alcohol and iso-olefin mixtures is discussed. Emphasis is placed on the synthesis of MTBE (methyl tert-butyl ether), but mention is also made of other ethers such as ETBE (ethyl tert-butyl ether), SAME (sec-amyl methyl ether) and MIPE (methyl isopropyl ether) and, to a very limited extent, of hydrocarbon feedstocks other than iso-olefins. Established sulphonated resin catalysts are described together with various aspects of their catalytic characteristics, including kinetics, thermodynamics and the occurrence of side-reactions. The use of alternative inorganic acids, especially zeolites, is covered and comparisons drawn between these systems and the ion-exchange resins. Finally, attention is given to the design of commercial processes for the production of MTBE.

Abstract  The oxidation characteristic of ETBE (ethyl tert-butyl ether) was determined using ARC (accelerating rate calorimetry). Oxidation temperature and oxidation kinetics were calculated using temperature-time (T-t) and pressure-time (P-t) plots, and reaction products were analyzed by GC-MS (gas chromatography-mass spectrum). Results showed that the oxidation reaction process of ETBE with oxygen occurred through absorption of oxygen by ETBE, followed by thermal decomposition and oxidation reaction. The initial auto-oxidation temperature was approximately 383 K. The initial oxygen absorption kinetics was second-order, 1/P = 1.39 x 10(-7)t + 7.31 x 10(-4). The thermal decomposition kinetics of ETBE peroxides was first-order reaction, and parameters were k = A(r) x exp (E-a/RT), in (A(r)) = 85.43 (1/min), E-a = 264.9 kJ/mol. E-a was reduced when the reaction included added peroxide. Oxidation reaction products were complex, indicating a link between the products and the ETBE/O-2 ratio. Many oxidation products were formed when an excess of oxygen, such as carbon dioxide, formaldehyde, formic acid, or acetic acid was present. And the acetic acid tert-butyl ester and formic acid 1,1-dimethylethyl ester were detected in reaction product. ETBE was stable even 393 K, and exothermic reaction has not been detected even 523 K under a nitrogen atmosphere. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  A two-step conversion of light-light cracked naphtha (LLCN) olefins to strong anti-knocking alcohol mixtures is proposed as a potential solution to the serious negative aspects from the use of gasoline ether oxygenates (MTBE, ETBE, TAME) from the refineries. Aqueous biphasic Rh/TPPTS-catalysed hydroformylation reaction of olefins present in a Greek refinery naphtha cut comprises the first part of the two-step proposed process. The second part of the proposed LLCN upgrade process is the in situ hydrogenation of the produced aldehydes to the corresponding alcohols catalysed by Ru/TPPTS complex in aqueous media. Both catalytic systems of Rh/TPPTS and Ru/TPPTS have been generated in situ by direct addition of the corresponding catalyst precursors to TPPTS in aqueous media; and they were revealed as effective catalytic systems for biphasic hydroformylation and biphasic hydrogenation of complicated mixtures, respectively. The ultimate fuel will contain more oxygen; it will have better combustion properties and higher octane numbers. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  The environmental pollution crisis and the new environmental legislations have facilitated the need for cleaner-burning gasoline. Oxygenate additives, which can increase the octane rating and induce complete fuel combustion, play increasingly important roles in the development of a greener and more sustainable environment. In this short review, one of the better-known oxygenate additives, ethyl tert-butyl ether (ETBE), is discussed; this compound gained interest after the limitations and negative impacts caused by the addition of methyl tert-butyl ether (MTBE) to gasoline were discovered. The discussion focuses on the trends in ETBE production and on the evolution of conventional separation techniques toward the development of hybrid processes. Moreover, a new concept that involves the use of nanomaterials (carbon nanotubes (CNTs) and graphenes) in the production and separation of ETBE is proposed and discussed.

Abstract  Vapor-liquid equilibrium (VLE), excess molar enthalpies (H-E), and excess molar volumes (V-E) provide complementary data for thermodynamic models. In this work, new data of binary mixtures of acetonitrile (ACN) or propanenitrile (PPN) with 2-ethoxy-2-methylpropane (ETBE) or 2-ethoxy-2-methylbutane (TAEE) are reported. Isothermal VLE data were measured by using a circulation still at 333 K for ETBE + ACN, at 343 K for TAEE + ACN, and at 363 K for TAEE + PPN. H-E were measured by using a SETARAM C80 calorimeter equipped with a flow mixing cell at 298 K for all four binary systems. V-E were measured by using an Anton Paar DMA 512P densimeter at 298 K for all four binary systems. H-E data and measured VLE data, or literature VLE data for the binary system of ETBE and PPN, were used for the optimization of Wilson model parameters by using VLEFIT software. Redlich-Kister equation parameters were separately regressed for the V-E data.

Abstract  The addition of renewable fuels to gasoline, such as bio-alcohols or bio-ethers is required in order to be in compliance with current environmental directives. Nevertheless, they change fuel properties which could affect standards compliance, engine performance and air emissions. This paper studies the impact of ethanol (EtOH), isobutanol (iBtOH) or ethyl tert-butyl ether (ETBE) on the Reid Vapour Pressure (RVP), distillation curves, density and other related gasoline properties, which belong to the group of relevant specifications that affect engine operation. The main conclusion is that the addition of ETBE or iBtOH has important advantages over EtOH in terms of energy density, air/fuel ratio, vapour pressure, renewable content and other effects; it was also found that the addition of ETBE affects equally and linearly the properties of two kinds of base gasolines as compared with other studies. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  Earlier recommendations [J.H. Dymond et al., Fluid Phase Equilibria 27 (1986) 1-13; C. Tsonopoulos et al., Pure Al. Chem. 61 (1989) 1387-1394.] are updated for C-4-C-8 alkanes and C-1-C-4 alkanols, and more recent values are presented for 1-hexanol. New recommendations are made for butane, on the basis of recent isochoric Burnett measurements. Preliminary recommendations are given for dimethyl, diethyl, and diisopropyl ethers, but nothing definitive can be said about other alkyl ethers due to the limited quantity and quality of the available data. Calculations with a correlation [C. Tsonopoulos, AIChE J. 20 (1974) 263-272] reexamine the dependence of the parameter b of alkanols and parameter a of alkyl ethers on their reduced dipole moment. Also included is the recent [C. Tsonopoulos and J.L. Heidman, Fluid Phase Equilibria 57 (1990) 261-276] analysis of the data for water and water/alkane binaries, along with new analyses of data for the binaries of water with methanol and ethanol. Only other relevant binary data that could be located were for n-hexane/ethanol and methanol/diethyl ether. Recommendations are given for the characteristic binary constant k(ij) for all binaries of interest. In addition, recent results are provided for the critical properties of the industrially important alkyl ethers MTBE, ETBE, TAME, and TAEE, together with recommendations for calculating their B with the 1974 correlation. (C) 1997 Elsevier Science B.V.

Abstract  Modern environmentally beneficial methods of formulating motor gasoline often use alcohols and/or ethers as octane improvers, Thus, the thermophysical properties of these substances have become important in process engineering design, the simulation of gasoline blending operations, and engine operability. In all of these applications, phase equilibrium properties are represented by thermodynamic models, which are derived from a combination of theory and experimental data. This work seeks to quantify these models from careful measurement of key thermodynamic properties. Vapour-liquid equilibrium measurements on 2-ethoxy-2-methylpropane (ETBE), 2-methoxy-2-methylbutane (TAME) and 2-methoxy-2-methylpropane (MTBE) with various alkanes, aromatics and oxygenates have been made over a temperature range of 293 to 323 K using a static experimental method. These data are utilised in the development of a flexible model for the thermodynamic properties of motor gasolines. The data are well correlated by the UNIQUAC excess Gibbs model for the liquid phase and with the Hayden-O'Connell correlation for the virial equation for the gas phase. Prediction of the vapour phase composition above a gasoline containing MTBE and methanol show maximum differences of 0.0353 in mass fraction. (C) 1997 Elsevier Science B.V.

Abstract  Reactive distillation has been demonstrated to reduce the capital cost and increase reactant conversion in MTBE production. These advantages are potentially transferable to the production of ETBE, TAME, and other tertiary ethers. However, the design of reactive distillation columns is complicated by interaction between phase and reaction equilibrium. Whereas in conventional distillation, an increase in fractionation is always associated with an improvement in process performance (separation of key components), the same does not necessarily aly to reactive distillation. Using the production of ETBE as an example, several reactive distillation columns were designed for various feed compositions and design philosophies. It was found that the best designs incorporated high reflux ratios with a restricted number of theoretical stages, and that increasing the number of theoretical stages could actually be detrimental to process performance.