Ethyl Tert-butyl Ether Research Articles

Organic/organic mixture separation by using novel ECTFE polymeric pervaporation membranes

Abstract ECTFE polymeric membranes were prepared via thermally induced phase separation (TIPS) technique using N-methyl-2-pyrrolidone as latent solvent and glycerol triacetate, triethyl citrate and adipic acid as plasticizers in order to improve polymer processability. The membranes were characterized by scanning electron microscopy, mechanical and contact angle tests for better evaluate their morphological and surface properties. The affinity and the resistance of the membranes with respect to different organic solvents (i.e. ethanol, methanol, methyl tert-butyl ether, ethyl tert-butyl ether and cyclohexane) were evaluated by means of swelling tests. All the membranes showed excellent solvent resistance (after 72 h) and high affinity to polar solvents, in particular to ethanol, whereas a low affinity to non polar solvents as cyclohexane was observed. Pervaporation (PV) tests by using a binary azeotropic mixture of ethanol and cyclohexane (30.5% w/w and 69.5% w/w) were carried out at different temperatures (30, 40 and 50 °C) and permeate pressures (2, 25 and 45 mbar). In all cases an improvement of the membrane performances, in terms of total flux, was observed by increasing the temperature and/or decreasing the permeate pressure. An improvement of the selectivity was, instead, obtained when both the temperature and the permeate pressure increased. The membranes with triethyl citrate and glycerol triacetate showed higher total flux, 1.7 kg m−2 h−1 and 1.5 kg m−2 h−1, with an ethanol/cyclohexane selectivity of 15 and 16, respectively. The membrane with adipic acid showed lower total flux, 0.45 kg m−2 h−1 of, but exhibited a much higher ethanol/cyclohexane selectivity, 31.

Liquid-liquid equilibrium data for water-ethanol-entrainer ternary system with entrainers: Cyclohexane, n-pentane, DEE (diethyl ether), DIPE (di-isopropyl ether), ETBE (ethyl tert-butyl ether)

The water-ethanol system was studied experimentally to find the liquid-liquid equilibrium (LLE) data at various temperature values by using five different entrainers: cyclohexane, n-pentane, DEE (diethyl ether), DIPE (di- isopropyl ether), and ETBE (ethyl tert-butyl ether). Ternary LLE data for water-ethanol-entrainer system was deter- mined based on an experimental procedure. Exact liquid activity coefficient parameters were found by experimental data and LLE data was predicted. For this purpose, two thermodynamic models, NRTL and UNIQUAC, were com- pared and contrasted with experimental data to probe into the better thermodynamic model for the azeotropic processes of ethanol system. The most promising entrainer was found through root mean square and average absolute deviations.

The Comparative and Combined Inhibitory Effects of MTBE and TBA on the Activities of Soil Exoenzymes

ABSTRACTMethyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) are major soil contaminants, and they have been actively investigated for their toxic effects on living organisms in soil ecosystems. Although previous studies have been used as tools to evaluate the health of soil, they have been limited in scope and ability to analyze the overall microbial activity. In the present study, the effects of MTBE and TBA on the activity of soil exoenzymes including urease, acid phosphatase, arylsulfatase, β-glucosidase, dehydrogenase, and fluorescein diacetate hydrolase, which are involved in nutrient cycles and overall microbial activities, were investigated. Soil samples were treated with 0–2% of MTBE and TBA solutions, and the comparative effects and combined effects on quantity of active soil exoenzymes were determined. The activity of six exoenzymes exposed solely to MTBE and TBA did not significantly change with dose concentration or exposure time, but did show significant changes when exposed to high concentrations of MTBE and TBA combined, with dehydrogenase being the most affected. Therefore, we proposed dehydrogenase as a potential biomarker to assess the risk of co-contamination of MTBE and TBA.

Grafting of cellulose acetate with ionic liquids for biofuel purification by a membrane process: Influence of the cation

A new strategy was developed for grafting ionic liquids (ILs) onto cellulose acetate in order to avoid IL extraction and improve its performance for ethyl tert-butyl ether (ETBE) biofuel purification by the pervaporation membrane process. This work extended the scope of IL-containing membranes to the challenging separation of organic liquid mixtures, in which these ILs were soluble. The ILs contained the same bromide anion and different cations with increasing polar feature. The membrane properties were strongly improved by IL grafting. Their analysis in terms of structure-property relationships revealed the influence of the IL content, chemical structure and chemical physical parameters α, β, π* in the Kamlet–Taft polarity scale. The ammonium IL led to the best normalized flux of 0.182kg/m2h for a reference thickness of 5μm, a permeate ethanol content of 100% and an outstanding infinite separation factor for the azeotropic mixture EtOH/ETBE at 50°C.

Forensic analysis of tertiary-butyl alcohol (TBA) detections in a hydrocarbon-rich groundwater basin.

Tertiary-butyl alcohol (TBA), a high-production volume (HPV) chemical, was sporadically detected in groundwater and coalbed methane (CBM) wells in southeastern Colorado's hydrocarbon-rich Raton Basin. TBA concentrations in shallow water wells averaged 75.1μg/L, while detections in deeper CBM wells averaged 14.4μg/L. The detection of TBA prompted a forensic investigation to try to identify potential sources. Historic and recent data were reviewed to determine if there was a discernable pattern of TBA occurrence. Supplemental samples from domestic water wells, monitor wells, CBM wells, surface waters, and hydraulic fracturing (HF) fluids were analyzed for TBA in conjunction with methyl tertiary-butyl ether (MTBE) and ethyl tertiary-butyl ether (ETBE), proxies for evidence of contamination from reformulated gasoline or associated oxygenates. Exploratory microbiological sampling was conducted to determine if methanotrophic organisms co-occurred with TBA in individual wells. Meaningful comparisons of historic TBA data were limited due to widely varying reporting limits. Mapping of TBA occurrence did not reveal any spatial patterns or physical associations with CBM operations or contamination plumes. Additionally, TBA was not detected in HF fluids or surface water samples. Given the widespread use of TBA in industrial and consumer products, including water well completion materials, it is likely that multiple diffuse sources exist. Exploratory data on stable isotopes, dissolved gases, and microbial profiling provide preliminary evidence that methanotrophic activity may be producing TBA from naturally occurring isobutane. Reported TBA concentrations were significantly below a conservative risk-based drinking water screening level of 8000μg/L derived from animal toxicity data.

Exposure to BTEX and Ethers in Petrol Station Attendants and Proposal of Biological Exposure Equivalents for Urinary Benzene and MTBE.

To assess exposure to benzene (BEN) and other aromatic compounds (toluene, ethylbenzene, m+p-xylene, o-xylene) (BTEX), methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE) in petrol station workers using air sampling and biological monitoring and to propose biological equivalents to occupational limit values. Eighty-nine petrol station workers and 90 control subjects were investigated. Personal exposure to airborne BTEX and ethers was assessed during a mid-week shift; urine samples were collected at the beginning of the work week, prior to and at the end of air sampling. Petrol station workers had median airborne exposures to benzene and MTBE of 59 and 408 µg m(-3), respectively, with urinary benzene (BEN-U) and MTBE (MTBE-U) of 339 and 780 ng l(-1), respectively. Concentrations in petrol station workers were higher than in control subjects. There were significant positive correlations between airborne exposure and the corresponding biological marker, with Pearson's correlation coefficient (r) values of 0.437 and 0.865 for benzene and MTBE, respectively. There was also a strong correlation between airborne benzene and urinary MTBE (r = 0.835). Multiple linear regression analysis showed that the urinary levels of benzene were influenced by personal airborne exposure, urinary creatinine, and tobacco smoking [determination coefficient (R(2)) 0.572], while MTBE-U was influenced only by personal exposure (R(2) = 0.741). BEN-U and MTBE-U are sensitive and specific biomarkers of low occupational exposures. We propose using BEN-U as biomarker of exposure to benzene in nonsmokers and suggest 1457 ng l(-1) in end shift urine samples as biological exposure equivalent to the EU occupational limit value of 1 p.p.m.; for both smokers and nonsmokers, MTBE-U may be proposed as a surrogate biomarker of benzene exposure, with a biological exposure equivalent of 22 µg l(-1) in end shift samples. For MTBE exposure, we suggest the use of MTBE-U with a biological exposure equivalent of 22 µg l(-1) corresponding to the occupational limit value of 50 p.p.m.

In English

We present a study on physical-chemical properties of hybrid inorganic-organic acid materials and their catalytic performance in ethyl tert-butyl ether synthesis under both atmospheric and elevated pressure. Such materials are compositions of acid styrene-divinylbenzene copolymer and silica with various (1.5–9.2 wt.%) polymer loadings (loaded resins LR). We have found that LR has better thermal stability compared to that of commercial sulfonic resins. Acidic properties of LR show that the acidity of polymer phase decreases with increasing of polymer loading. Catalytic tests show that under atmospheric pressure ethyl tert-butyl ether synthesis requires a higher acid capacity of LR than that under elevated pressure and proceeds with 100% of selectivity. Under pressure the side reaction of tert-butanol formation occurs and LR samples with higher polymer content (≥ 6.9 wt.%) possess lower conversion but higher selectivity compared to LR with polymer content below 6.9 wt.%.

Physical properties of gasoline, isobutanol and ETBE binary blends in comparison with gasoline ethanol blends

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.

Oxidation characteristics and products of five ethers at low temperature

The oxidation characteristics and products of five ethers – ethyl tert-butyl ether (ETBE), methyl tert-butyl ether (MTBE), dimethyl ether (DME), diethyl ether (DEE), and diisopropyl ether (DIPE) – were determined using an accelerating rate calorimeter (ARC) at low temperatures. Oxidation temperature and pressure were calculated using temperature–time (T–t) and pressure–time (P–t) plots, and reaction products were analyzed by gas chromatography–mass spectrometry (GC–MS). Results showed that the oxidation reaction pathway of ethers with oxygen occurred in three stages: (1) promotion of oxygen and peroxide absorption by ether; (2) generation of free radicals by thermal decomposition; and (3) complex oxidation caused by free radicals. Initial auto-oxidation temperatures of DME, DEE, DIPE, MTBE, and ETBE were approximately 393K, 389K, 359K, 413K, and 383K, respectively, and the activation energies (Ea) for thermal decomposition were 167.3kJ/mol, 126.7kJ/mol, 111.6kJ/mol, 236.7kJ/mol, and 159.1kJ/mol, respectively, for the first-order reaction. Peroxides of DEE, DIPE, MTBE, and ETBE were identified by iodimetry analysis when oxidation temperature was 333K. Oxidation reaction products were complex and included alcohols, aldehydes, ketones, acids, esters, and carbon dioxide.

Equilibrium conversion, selectivity and yield optimization of the simultaneous liquid-phase etherification of isobutene and isoamylenes with ethanol over Amberlyst™ 35

A prospective study on the product distribution at chemical equilibrium for the simultaneous liquid-phase etherification of isobutene and isoamylenes with ethanol over Amberlyst™ 35 is presented. Experiments were performed isothermally in a 200cm3 stirred tank batch reactor operating at 2.0MPa. Initial molar ratios of alcohol/olefins and isobutene/isoamylenes ranged both from 0.5 to 2, and temperature from 323 to 353K. Reactants equilibrium conversion, selectivities and yields toward products were clearly affected by the experimental conditions. Experimental etherification yields have been modeled using the response surface methodology (RSM), combined with the stepwise regression method to include only the statistically significant variables into the model. The multiobjective optimization (MOO) of etherification yields has been carried out numerically, by means of the desirability function approach, and graphically, by using the overlaid contour plots (OCP). Optimal conditions for the simultaneous production of ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE) have been found to be at low temperatures (323 to 337K) and initial molar ratio alcohol/olefins close to 0.9 and isobutene/isoamylenes close to 0.5.

Speed of sound measurement in ethyl tert-butyl ether and tert-amyl methyl ether by Brillouin light scattering

Ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) have been considered as the potential fuel additives as the replacement of methyl tert-butyl ether (MTBE). Now it is necessary to supplement and perfect the thermophysical properties of oxygenates, including acoustic property. In this paper, speed of sound in ETBE and TAME were measured by Brillouin light scattering from 293.15 K to 680 K and from saturated vapor pressure to 10 MPa, including saturated liquid/vapor, compressed liquid and supercritical region. It is estimated that u (T) = 0.01 K under saturated condition; u (T) = 0.02 K, u (p) = 0.015 MPa for p < 5.5 MPa, u (p) = 0.03 MPa for p > 5.5 MPa under compressed liquid and supercritical conditions; and the relative expended uncertainty in the speed of sound is estimated to be less than 0.5% with coverage factor of k to be 2. Moreover, the reference relations of the speed of sound for saturated liquid, vapor and compressed state are presented for interpolation with the average absolute deviation of 0.23%, 0.07% and 0.33% for ETBE and 0.34%, 0.24% and 0.29% for TAME, respectively.

Nanostructures in clear and homogeneous mixtures of rapeseed oil and ethanol in the presence of green additives

Ethanol and rapeseed oil are mixed in the presence of tributyl citrate, 2,5-dimethylfuran, 2-methylfuran, 2-methyl tetrahydrofuran, methyl tert butyl ether, ethyl tert butyl ether, FAME-rapeseed biodiesel, 1-heptanol, and 2-ethylhexyl nitrate, at 25 °C (298.15 K). All these additives come or can be obtained completely or partially from plants. The obtained ternary phase diagrams show a large domain of clear and homogeneous solutions and a liquid two-phase system due to the partial solubility of rapeseed oil and ethanol. All the tested additives have thus an evident cosolvent behavior for ethanol and rapeseed oil. In all the studied systems, the possible presence of nanostructures is checked with dynamic light scattering (DLS) and confirmed using static light scattering (SLS). In the system rapeseed oil/ethanol/1-heptanol, the presence of nanostructures is definitely established performing small-angle neutron scattering (SANS). The true geometry of these nanostructures could not be detected, but systematic conductivity measurements starting with the binary melt 1-heptanol/rapeseed oil in the presence of LiClO4 adding ethanol show clearly a continuous transition from ethanol-in-rapeseed oil to rapeseed oil-in-ethanol mixtures passing through a bicontinuous medium.

Development and application of a rat PBPK model to elucidate kidney and liver effects induced by ETBE and tert-butanol

Subchronic and chronic studies in rats of the gasoline oxygenates ethyl tert-butyl ether (ETBE) and tert-butanol (TBA) report similar noncancer kidney and liver effects but differing results with respect to kidney and liver tumors. Because TBA is a major metabolite of ETBE, it is possible that TBA is the active toxic moiety in all these studies, with reported differences due simply to differences in the internal dose. To test this hypothesis, a physiologically-based pharmacokinetic (PBPK) model was developed for ETBE and TBA to calculate internal dosimetrics of TBA following either TBA or ETBE exposure. This model, based on earlier PBPK models of methyl tert-butyl ether (MTBE), was used to evaluate whether kidney and liver effects are consistent across routes of exposure, as well as between ETBE and TBA studies, on the basis of estimated internal dose. The results demonstrate that noncancer kidney effects, including kidney weight changes, urothelial hyperplasia, and chronic progressive nephropathy (CPN), yielded consistent dose–response relationships across routes of exposure and across ETBE and TBA studies using TBA blood concentration as the dose metric. Relative liver weights were also consistent across studies on the basis of TBA metabolism, which is proportional to TBA liver concentrations. However, kidney and liver tumors were not consistent using any dose metric. These results support the hypothesis that TBA mediates the noncancer kidney and liver effects following ETBE administration; however, additional factors besides internal dose are necessary to explain the induction of liver and kidney tumors.

Impact of the content of ETBE, EtOH and polybutylene-succinate additives on the propensity of E10 petrol to form deposits in combustion chambers

This paper presents the results of research on the propensity of E10 petrol (defined by EN 228 standard as a petrol with a maximum oxygen content of 3.7wt.%) to form deposits in combustion chambers by using the method of determining the unwashed gum content EN ISO 6246 and by thermography TGA FLTM BZ-154-01. The aim of this is study was to examine samples of unleaded petrol 95 containing ethanol (EtOH) and/or ethyl tert-butyl ether (ETBE) improved with three different packages containing detergent additives derived from poly-succinic acid. The additive D3 containing imido-amid of polybutylene-succinate exhibited the best efficiency in reducing the propensity for fuel deposit formation in combustion chambers. Clear differences were found in how the presence of various oxygenating compounds can affect the efficiency of the thermogravimetric decomposition of gums. In the case of petrol containing ETBE as the only oxygenate, for the same levels of additives used, there was a reduced tendency to form deposits (CCD) than for the same type of petrol fuel with ethanol content.

Physicochemical Properties and Catalytic Performance of Sulphonic Resins of Various Morphological Types in Ethyl t-Butyl Ether Synthesis

Physicochemical and catalytic properties of sulphonic resins of various morphological types in ethyl t-butyl ether synthesis were studied. We have found that the turnover frequency (TOF) of sulphonated cation-exchange resins reflects the effect of morphology expressed in terms of fractal geometry. The correlation between the catalytic activity of various types of sulphonated resins and their fractal dimension was established. Difference in observed TOF of sulphonic resins of various morphological types is caused by various accessibilities of acid sites. Catalysts of more ordered structure (characterized by smaller fractal dimension) provide the best conditions for the adsorption–desorption of reactants and products resulting in large values of TOF.

Promotion of liver and kidney carcinogenesis by ethyl tertiary-butyl ether (ETBE) in male Wistar rats.

Tumor-promoting effects of ethyl tertiary-butyl ether (ETBE) were investigated in a 2-stage carcinogenesis bioassay with regard to hepatic and renal carcinogenesis in rats. Male 6-week-old Wistar rats were given drinking water containing N-ethyl-N-(2-hydroxyethyl)nitrosamine (EHEN), as an initiator, at a dose of 500 ppm for 2 weeks. Starting one week thereafter, the animals were administered ETBE at dose levels of 0 (control), 100, 300, 500 or 1,000 mg/kg/day by gavage for 19 weeks from week 4 to 22. Necropsy of all rats was performed at week 23, and livers and kidneys were examined histopathologically. Incidences of hepatocellular adenomas, and those of combined hepatocellular adenomas and carcinomas were significantly elevated in rats given 1,000 mg/kg/day ETBE, but not 100‒500 mg/kg/day ETBE, and there was a significant increase in the average numbers of lesions. No significant differences in incidences and average numbers of renal tubule neoplasms were found in rats administered 100‒1,000 mg/kg/day ETBE. However, the average numbers of atypical tubule hyperplasias, considered to be preneoplastic lesions, were significantly increased in rats given ETBE at 1,000 mg/kg/day, but not in rats given 500 mg/kg/day or lower doses. Thus, these results imply that ETBE has hepatic and renal tumor-promoting activities that affect EHEN-induced carcinogenesis in male rats, and the no-observed-effect level is 500 mg/kg/day under the present experimental conditions.

Atmospheric oxidation of methyl and ethyl tert-butyl ethers initiated by hydroxyl radicals. A quantum chemistry study

Abstract In this work, a systematic investigation on the reactions of methyl t-butyl ether (MTBE) and ethyl t-butyl ether (ETBE) with OH radicals in the gas phase has been performed, within the Density Functional (DFT) framework. The potential energy surfaces were obtained at the M06-2X/6-311++G(d,p) level. Specific emphasis was given to obtain kinetic data for MTBE and ETBE oxidative degradation and to identify and quantify the intermediate products formed. The values of the calculated rate constants reproduce remarkably well the available experimental data. The calculated total rate constants for the MTBE + OH and ETBE + OH reactions, in the gas phase at 298.15 K, are 2.79 × 10−12 and 7.38 × 10−12 cm3 molecules−1 s−1. Thus, ETBE reacts more than 2 times faster with OH radicals than MTBE. In both molecules, the hydrogen atoms that are most easily abstracted are the ones occupying an α position with respect to the ether oxygen atom. The contribution of the reaction channels involving H-abstraction from the tert-butyl group amounts to about 24–27% of the total rate coefficient. The results obtained in this work may improve the reliability and precision of the OH radical kinetic data required to predict the lifetime of aliphatic ethers and their contribution to urban and regional pollution.

The cleaning method selected for new PEX pipe installation can affect short-term drinking water quality.

The influence of four different cleaning methods used for newly installed polyethylene (PEX) pipes on chemical and odor quality was determined. Bench-scale testing of two PEX (type b) pipe brands showed that the California Plumbing Code PEX installation method does not maximize total organic carbon (TOC) removal. TOC concentration and threshold odor number values significantly varied between two pipe brands. Different cleaning methods impacted carbon release, odor, as well the level of drinking water odorant ethyl tert-butyl ether. Both pipes caused odor values up to eight times greater than the US federal drinking water odor limit. Unique to this project was that organic chemicals released by PEX pipe were affected by pipe brand, fill/empty cycle frequency, and the pipe cleaning method selected by the installer.

A unifying framework for optimization-based design of integrated reaction–separation processes

The determination of the best flowsheet and the development of a conceptual design of a chemical reaction–separation process is a complex task. Although model-based methods for process design have been proposed in the last decades, only a few contributions address the simultaneous design and optimization of integrated reaction–separation processes. This paper presents a systematic and optimization-based approach for the design of such processes. Shortcut methods are utilized to screen alternative flowsheet structures. For the most promising alternatives a rigorous optimization of the entire flowsheet is executed to determine the best alternative. The incremental refinement of this framework allows for the systematic generation and numerically robust evaluation of every reaction–separation process. Consequently, it helps to shorten the time for developing new and innovative processes and improves the chances to find the best process design. The suggested methodology is illustrated by means of a case study considering ethyl tert-butyl ether (ETBE) production.

Oxidation characteristic and products of ETBE (ethyl tert-butyl ether)

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 × 10−7t + 7.31 × 10−4. The thermal decomposition kinetics of ETBE peroxides was first-order reaction, and parameters were k = Ar × exp (Ea/RT), ln (Ar) = 85.43 (1/min), Ea = 264.9 kJ/mol. Ea was reduced when the reaction included added peroxide. Oxidation reaction products were complex, indicating a link between the products and the ETBE/O2 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.