Abstract  OBJECTIVES: In order to measure occupational exposure concentrations of ethyl tertiary-butyl ether (ETBE), we developed a diffusive sampling method for monitoring ETBE and performed an ETBE exposure assessment.

METHODS: The applicability of diffusive samplers was examined by exposing the samplers to ETBE vapor in test chambers. The personal exposure levels of workers and airborne concentrations were measured at 4 gas stations.

RESULTS: The ETBE sampling rate for the diffusive samplers (VOC-SD, Sigma-Aldrich Japan) was 25.04 ml/min (25°C). Compared with the active sampling method, the diffusive samplers could be used for short-term measurements and in environments containing a mixture of organic solvents. The geometric mean (GM) of TWA-8h ETBE was 0.08 ppm (0.02-0.28 ppm) in 28 gas station workers and 0.04 ppm (0.01-0.21 ppm) in 2 gasoline tanker truck drivers. With regard to ETBE airborne concentrations, the GM was 4.12 ppm (0.93-8.71 ppm) at the handles of hanging pumps but dropped to less than 0.01 ppm (less than 0.01-0.01 ppm) at the side of a public road.

CONCLUSION: The diffusive sampling method can be used for the measurement of occupational ETBE exposure. The threshold limit of TLV-TWA 5 ppm recommended by the ACGIH was not exceeded in any of the workers in this study.

Abstract  This study aimed to investigate the comparative effects of oxygenates such as ethanol (EA), methyl tertiary-butyl ether (MTBE), and ethyl tertiary butyl ether (ETBE) by fixing the oxygen contents as 0.82 wt% 1.65 wt%, and 2.74 wt% of the fuels on the regulated (CO, NMHC and NOx) and unregulated (formaldehyde, acetaldehyde and BTEX) exhaust emissions in gasoline-powered vehicles. The most widely used type of vehicles (light-duty, medium-duty, heavy-duty) in Korea were tested on a chassis dynamometer under the CVS-75 Cycle. When EA, MTBE and ETBE percentage increased, the CO and NMHC concentration decreased. The NOx emission decreased at 1.65 wt% and 2.74 wt% oxygen content of MTBE and ETBE. The emissions of CO decreased by 0.363 g/km, 0.266 g/km and 0.356 g/km for light-duty vehicle when EA, MTBE and ETBE oxygenates blending ratio increased. Increased EA, MTBE and ETBE oxygenates blending ratio demonstrated no specific reducing effect on CO emissions from low-mileage vehicle, but NMHC emissions decreased by 0.011 g/km (medium-duty), 0.015 g/km (light-duty) and 0.018 g/km (heavy-duty). More CO was emitted from MTBE among three oxygenates at same oxygen content. The emitted concentrations of NMHC from three oxygenates at same oxygen content were almost similar, but reduced NOx emissions from EA (10%) to MTBE (20.4%) and ETBE (23.6%) were observed at 2.74 wt% oxygen content. Reducing effect on CO emissions was order of EA > ETBE > MTBE. Formaldehyde emissions increased up to 54.3% as MTBE ratio increased. When oxygen content of ETBE, EA, and MTBE increased from 0.82 wt% to 2.74 wt%, the acetaldehyde emissions increased up to 177.4%, 39.5% and 31.0%, respectively. There was significant formaldehyde concentration difference between high emission vehicle type (light-duty and medium-duty) and low emission vehicle type (heavy-duty and low-mileage) for three oxygenates. Reduction effect of MTBE and ETBE on BTEX was the order of toluene > benzene > ethylbenzene > xylene, and MTBE showed more reduction effect than ETBE at same oxygen content.

Abstract  OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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 780ng 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).

CONCLUSIONS: 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 1457ng 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.

Abstract  Catalytic activity of different zeolites: H, NH4-form of mordenite-containing rock (H-CMK) and H-Beta with a Si/Al ratio of 15-407 (H-BEA) in ethyl tert-butyl ether (ETBE) synthesis in a packed-bed flow reactor at 80-180 degrees C and 1 MPa has been studied. Acid characteristics of zeolites were determined by stepwise (Quasi-Equilibrium) ammonia thermodesorption. Three types of acid sites of different strength has been found, which is marked as weak (E-NH3-60-75 kJ/mol), medium (E-NH3-86-123 kJ/mol), and strong (E-NH3 = 112-145 kJ/mol). The correlation between ETBE productivity and the concentration of weak acid sites has been found. Thereby, it was established that weak acid sites of zeolites are the active sites in ETBE synthesis.

Abstract  The thermal diffusivities of 2-ethoxy-2-methylpropane (ETBE) and 2-methoxy-2-methylbutane (TAME) (mass purity > 0.990, GC) were measured by.the dynamic light scattering method. The investigated p T regions are T = (293 to 523) K and p = (4 to 10) MPa, including saturated liquid, saturated vapor, and liquid. The expanded relative uncertainty in thermal diffusivity was estimated to be less than 2.4% over the whole investigated range. The influences of temperature and pressure on thermal diffusivity were presented. The empirical correlation of thermal diffusivities for both saturated liquid/vapor and liquid were also proposed with absolute average relative deviations (AARDs) of 0.22 and 0.26% for saturated-liquid ETBE and TAME, 0.13 and 0.20% for saturated-vapor ETBE and TAME, and 0.23 and 0.69% for liquid ETBE and TAME, respectively.

Abstract  A kinetic study on the simultaneous liquid-phase etherification of ethanol with isobutene (IB), 2-methyl-1-butene (2M1B) and 2-methyl-2-butene (2M2B) catalyzed by Amberlysf (TM) 35 to form ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE) is presented. Isothermal experimental runs were carried out in a stirred tank batch reactor in the temperature range 323-353 K at 2.0 MPa, starting from different initial concentrations. Obtained reaction rates were free of catalyst load, internal, and external mass transfer effects. Mathematical fitting of a series of systematically originated models, model selection, and model averaging procedures were applied to find the best model and to draw conclusions about the reaction mechanism. The selected model involves a saturated catalytic surface with the participation of two active sites in etherification reactions and one active site in isoamylenes isomerization. Apparent activation energies for ETBE formation from IB and EtOH, TAEE formation from 2M1B and EtOH, TAEE formation from 2M2B and EtOH, and double bond isomerization between 2M1B and 2M2B were 72.8 +/- 1.4, 74.9 +/- 2.8, 81.2 +/- 2.2 and, 76.5 +/- 7.2 kJ/mol, respectively. The alkenes with the double bond in terminal position were more reactive towards EtOH than 2M2B, with the double bond in internal position. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  In this study concentrations of aromatic hydrocarbons (BTEX-components), with special interest for benzene, plus methyl-tert-butylether (MTBE) and ethyl-tert-butylether (ETBE) were measured in air of salesrooms of gas stations and in air among gas stations. Using seven days passive sampling technique in the salesrooms, each in winter and summer, measured median concentrations of 3.8 mu g/m(3) benzene, 72.3 mu g/m(3) toluene, 6.1 mu g/m(3) ethylbenzene and 34.7 mu g/m(3) sum of xylene were given. MTBE could not be measured above LOQ (0.051.1 mu g/m(3)), ETBE showed a median of 3.3 1.1 mu g/m(3). Concentrations measured in summer lay slightly above those measured in winter, although the difference was not statistically significant. There is a weak relation between the concentration of aromatic hydrocarbons measured in salesrooms and the distance from the entrance to the nearest fuel dispenser. About 30% of the measurements in salesrooms lay above 5 mu g/m(3), the concentration that might indicate a current reference value.

Abstract  The Clean Air Act Amendments (CAAA) of 199G mandated the addition of 2.7% oxygen from oxygenated organic species (oxygenates) to automotive fuels during the winter season in areas not attaing the National Ambient Air Quality Standards for carbon monoxide (CO). Oxygenates arc added to gasoline to increase the octane rating and minimize incomplete combustion. reducing air pollutants including carbon monoxide and unburned hydrocarbons. Anecdotal reports of health complaints (e.g., headaches. iniration, Dausea) allegedly associated with oxyfuel use led to a variety of research efforts in 1993 (EPA. 1995). These included measurements of customer fuel oxygenate additive exposure during commuting (Lioy et al, 1994) and refueling (IT, I995a). A survey of oil company occupational exposure records (IT, 1995b) provided adequate numbers of exposure measurements for employees in most seaors of me petroleum refining and marketing industry. However,relatively few measurements were available to document the exposure of attendants refueling cars (Hartle. 1993)or auto mechanics repairing vehicles in service stations. This study measured service station refueling attendant and mechanic exposures to oxygenated species (metbyl tertiary butyl ether(MTBE), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), ethanol (ETOH), selected aromatics (benzene-B, toluene-T, xylenes-X, ethylbenune-EB) and total hydrocarbons (THC) during normal activities at service stations dispensing oxyfuels during the winter season and non-oxyfuels during the summer of 1994. Characterizations of dispensed liquid fuel compositions and local meteorology during sampling were also undertaken

Abstract  Vapor intrusion of synthetic fuel additives represents a critical yet still neglected problem at sites contaminated by petroleum fuel releases. This study used an advanced numerical model to investigate the vapor intrusion potential of fuel ether oxygenates methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and ethyl tert-butyl ether (ETBE). Simulated indoor air concentration of these compounds can exceed USEPA indoor air screening level for MTBE (110μg/m(3)). Our results also reveal that MTBE has much higher chance to cause vapor intrusion problems than TAME and ETBE. This study supports the statements made by USEPA in the Petroleum Vapor Intrusion (PVI) Guidance that the vertical screening criteria for petroleum hydrocarbons may not provide sufficient protectiveness for fuel additives, and ether oxygenates in particular. In addition to adverse impacts on human health, ether oxygenate vapor intrusion may also cause aesthetic problems (i.e., odour and flavour). Overall, this study points out that ether oxygenates can cause vapor intrusion problems. We recommend that USEPA consider including the field measurement data of synthetic fuel additives in the existing PVI database and possibly revising the PVI Guidance as necessary.

Abstract  Green buildings are increasingly being plumbed with crosslinked polyethylene (PEX) potable water pipe. Tap water quality was investigated at a six month old plumbing system and chemical and odor quality impacts of six PEX pipe brands were examined. Eleven PEX related contaminants were found in the plumbing system; one regulated (toluene) and several unregulated: Antioxidant degradation products, resin solvents, initiator degradation products, or manufacturing aides. Water chemical and odor quality was monitored for new PEX-a, -b and -c pipes with (2 mg/L free chlorine) and without disinfectant over 30 days. Odor and total organic carbon (TOC) levels decreased for all pipes, but odor remained greater than the USA's Environmental Protection Agency's (USEPA) secondary maximum contaminant level. Odors were not attributed to known odorants ethyl-tert-butyl ether (ETBE) or methyl-tert-butyl ether (MTBE). Free chlorine caused odor levels for PEX-a1 pipe to increase from 26 to 75 threshold odor number (TON) on day 3 and affected the rate at which TOC changed for each brand over 30 days. As TOC decreased, the ultraviolet absorbance at 254 nm increased. Pipes consumed as much as 0.5 mg/L as Cl2 during each 3 day stagnation period. Sixteen organic chemicals were identified, including toluene, pyridine, methylene trichloroacetate and 2,4-di-tert-butylphenol. Some were also detected during the plumbing system field investigation. Six brands of PEX pipes sold in the USA and a PEX-a green building plumbing system impacted chemical and drinking water odor quality.

Abstract  The rates of Brønsted-acid-catalyzed reactions of ethyl tert-butyl ether, tert-butanol, levoglucosan, 1,2-propanediol, fructose, cellobiose, and xylitol were measured in solvent mixtures of water with three polar aprotic cosolvents: γ-valerolactone; 1,4-dioxane; and tetrahydrofuran. As the water content of the solvent environment decreases, reactants with more hydroxyl groups have higher catalytic turnover rates for both hydrolysis and dehydration reactions. We present classical molecular dynamics simulations to explain these solvent effects in terms of three simulation-derived observables: (1) the extent of water enrichment in the local solvent domain of the reactant; (2) the average hydrogen bonding lifetime between water molecules and the reactant; and (3) the fraction of the reactant accessible surface area occupied by hydroxyl groups, all as a function of solvent composition. We develop a model, constituted by linear combinations of these three observables, that predicts experimentally determined rate constants as a function of solvent composition for the entire set of acid-catalyzed reactions.

Abstract  No abstract available.

Abstract  The oxidation of ethyl tert-butyl ether (ETBE), a widely used fuel oxygenated additive, is investigated using Cl atoms as initiators in the presence of oxygen. The reaction is carried out at 293, 550, and 700 K. Reaction products are probed by a multiplexed chemical kinetics photoionization mass spectrometer coupled with the synchrotron radiation produced at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory. Products are identified on the basis of mass-to-charge ratio, ionization energies, and shape of photoionization spectra. Reaction pathways are proposed together with detected primary products.