Additive Methyl Tert-butyl Ether Research Articles

Plasma-chemical pyrolysis of a mixture of fuel oil and methyl tert-butyl ether

NTP-pyrolysis of heavy petroleum products is a difficult task due to high viscosity, low hydrogen-to-carbon ratio and tendency to polycondensation with formation of high-molecular products. The use of oxygen-containing compounds for NTP-pyrolysis can reduce the yield of polycondensation products due to internal oxygen. In the present work, NTP pyrolysis of fuel oil in the presence of oxygen-containing additive (methyl tert-butyl ether) was carried out at a current source voltage of 700V. The influence of the content of the doping component in the range of 5-15 wt% on conversion, energy consumption and product composition was investigated. At increase in the content of methyl-tert-butyl ether up to 15 wt% in fuel oil the energy consumption decreases and the yield of gaseous products increases from 21.7 to 47.9 wt%. Carrying out NTP-pyrolysis process in the presence of oxygen-containing additive leads to an increase in the depth of processing of heavy fractions.

Study of cyclic cataluminescence virtual sensor array for gasoline quality monitoring

The addition of methyl tert-butyl ether (MTBE) can increase the octane number of gasoline to improve the combustion efficiency of gasoline. Because of the health effects on the population exposed to MTBE, limiting the addition of MTBE in gasoline will be thefuture development tendency. Here, a cyclic cataluminescence (CCTL) sensor array was utilized to monitor the addition of MTBE in gasoline. CCTL sensor obtained multistage signals (In) on a single catalyst, which realized the function of the sensor array. MTBE trigger-CCTL reaction on 4 kinds of catalysts was investigated. Three brands (No. 92, 95, and 98) of gasoline triggered the CCTL reaction to obtain In which conforms to the exponential decay equation (EDE). CCTL sensor was used to detect the volume ratio of MTBE to gasoline according to A and τ-values. The In was applied to normalize and distinguish gasoline through linear discriminate analysis (LDA) and hierarchical cluster analysis (HCA). The τ-values of gasoline on 4 catalysts generated a digital code to differentiate each gasoline. CCTL virtual sensor arrays own the sensor array function and provide a promising technology for gasoline quality analysis.

Understanding of the octane response of gasoline/MTBE blends

Despite the wide utilization of MTBE as an octane booster for market gasoline fuels, the blending characteristics of methyl tert-butyl ether (MTBE) with gasoline fuels are not fully understood. This arises from the lack of octane number measurement of MTBE/gasoline blends, along with lack of detailed analyses of MTBE blending characteristics. In an attempt to address the knowledge gap in MTBE blending, this study provides new research octane number (RON) and motor octane number (MON) measurements of MTBE blended with various pure components and gasoline fuels. The first set of blends were binary mixtures of pure components blended with MTBE. The pure components we chosen to represent PIONA (paraffins, iso-paraffins, olefins, naphthenes and aromatics) molecular classes. The second set of blends were Fuels for Advanced Combustion Engines (FACE) and market gasoline fuels with MTBE. It was observed that the addition of MTBE to n-paraffins, iso-paraffins and olefins results in synergistic octane number effect while linear-by-volume and antagonistic blending was observed for MTBE blends with naphthenes and aromatics, respectively. The octane numbers and response of gasoline/MTBE blends are also dependent on the composition of the base gasoline fuel. These new measurements along with literature dataset were utilized to develop octane predictive models for MTBE blended with gasoline fuels. Various blending rules such as linear-by-volume (LBV), octane sensitivity (OS) and PIONA based models were developed in this work. The most accurate model was the linear-by-volume with the iso-paraffins and aromatics terms where more than 80% of the predictions are within the experimental reproducibility limits. The model can be used to predict and quantify the characteristics of octane boost caused by MTBE addition to gasoline fuels. It can also be used to optimize the octane boost due to the addition of MTBE by changing the composition of the base gasoline fuel.

Reservoir operation under accidental MTBE pollution: A graph-based conflict resolution framework considering spatial-temporal-quantitative uncertainties

Given the hazardous effects of sudden dam reservoir contamination — as might occur upon the intrusion of the fuel additive methyl tert-butyl ether (MTBE) — the contaminant’s effect on the quality of allocated waters requires careful study. Employed to determine optimal reservoir operational rules in the case of sudden MTBE pollution, a risk-based simulation–optimization model was developed to simultaneously minimize unsatisfied water demand, the risk of violations of water quality standards, and the reservoir recovery time. Risks were assessed by considering various often-neglected pollution scenarios as a combination of location, quantity, and the season of pollution intrusion. The appropriateness of operational rules proved to depend upon thermal conditions and MTBE intrusion properties, confirming the necessity of considering location-quantity-season uncertainties. Social and regional conditions also occupied a dominant role in determining the level of satisfaction achieved under different water allocation strategies. Accordingly, by considering environmental conditions and local rules, a graph model for conflict resolution was established and used to reach a set of compromise operational rules. The developed framework could serve as a guide for water utilities to determine efficient reservoir operational rules after a sudden contaminant intrusion.

Biphasic Bioelectrocatalytic Synthesis of Chiral β-Hydroxy Nitriles

Two obstacles limit the application of oxidoreductase-based asymmetric synthesis. One is the consumption of high stoichiometric amounts of reduced equivalent. The other is the low solubility of organic substrates, intermediates, and products in the aqueous phase. In order to address the two obstacles of oxidoreductase-based asymmetric synthesis, a biphasic bioelectrocatalytic system was constructed and applied.. In this study, the preparation of chiral β-hydroxy nitriles catalyzed by alcohol dehydrogenase (AdhS) and halohydrin dehalogenase (HHDH) was investigated as a high-value organic product. Diaphorase (DH) was immobilized by cobaltocene-modified poly(allylamine) redox polymer on the electrode surface (DH/Cc-PAA bioelectrode) to realize the effective bioelectrocatalytic NADH regeneration. AdhS is a NAD-dependent dehydrogenase, so the diaphorase modified biocathode was used to regenerate NADH to support the conversion from ethyl 4-chloroacetoacetate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by AdhS. The addition of methyl tert-butyl ether (MTBE) as organic phase not only increased the uploading of COBE, but also prevented the spontaneous hydrolysis of COBE and extended the lifetime of DH/Cc-PAA bioelectrode, and finally increased the Faradaic efficiency and the concentration of generated (R)-ethyl-4-cyano-3-hydroxybutyrate ((R)-CHCN). After 10 hours of reaction, the highest concentration of (R)-CHCN in biphasic bioelectrocatalytic system achieve 25.5 mM with 81.2% enantiomeric excess (ee p). The conversion ratio of COBE achieved 85%, which was 8.8 times higher than that of single phase system. Besides COBE, the other two substrates with aromatic ring structures were also used in this biphasic bioelectrocatalytic system to prepare corresponding chiral β-hydroxy nitriles. The results indicate that the biphasic bioelectrocatalytic system has the potential to produce a variety of β-hydroxy nitriles with different structures.

Biphasic Bioelectrocatalytic Synthesis of Chiral β-Hydroxy Nitriles.

Two obstacles limit the application of oxidoreductase-based asymmetric synthesis. One is the consumption of high stoichiometric amounts of reduced cofactor. The other is the low solubility of organic substrates, intermediates, and products in the aqueous phase. In order to address these two obstacles to oxidoreductase-based asymmetric synthesis, a biphasic bioelectrocatalytic system was constructed and applied. In this study, the preparation of chiral β-hydroxy nitriles catalyzed by alcohol dehydrogenase (AdhS) and halohydrin dehalogenase (HHDH) was investigated as a model bioelectrosynthesis, since they are high-value intermediates in statin synthesis. Diaphorase (DH) was immobilized by a cobaltocene-modified poly(allylamine) redox polymer on the electrode surface (DH/Cc-PAA bioelectrode) to achieve effective bioelectrocatalytic NADH regeneration. Since AdhS is a NAD-dependent dehydrogenase, the diaphorase-modified biocathode was used to regenerate NADH to support the conversion from ethyl 4-chloroacetoacetate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by AdhS. The addition of methyl tert-butyl ether (MTBE) as an organic phase not only increased the uploading of COBE but also prevented the spontaneous hydrolysis of COBE, extended the lifetime of DH/Cc-PAA bioelectrode, and increased the Faradaic efficiency and the concentration of generated (R)-ethyl-4-cyano-3-hydroxybutyrate ((R)-CHCN). After 10 h of reaction, the highest concentration of (R)-CHCN in the biphasic bioelectrocatalytic system was 25.5 mM with 81.2% enantiomeric excess (eep). The conversion ratio of COBE achieved 85%, which was 8.8 times higher than that achieved with the single-phase system. Besides COBE, two other substrates with aromatic ring structures were also used in this biphasic bioelectrocatalytic system to prepare the corresponding chiral β-hydroxy nitriles. The results indicate that the biphasic bioelectrocatalytic system has the potential to produce a variety of β-hydroxy nitriles with different structures.

Chemical oxidation using stabilized hydrogen peroxide in high temperature, saline groundwater impacted with hydrocarbons and MTBE

In situ chemical oxidation (ISCO) of petroleum hydrocarbons (PHCs) within groundwater is considered a proven approach to addressing PHC-impacted groundwater in nonsaline environments. One of the most common oxidants used for oxidation of PHCs in groundwater is hydrogen peroxide (H2O2). Due to its highly reactive nature, H2O2 is often stabilized to aid in increasing its reactivity lifespan. Limited research and application of ISCO has been completed in warm, saline groundwater environments. Furthermore, even fewer studies have been completed in these environments for ISCO using stabilized H2O2. In this research, stabilized H2O2 was examined to determine its effectiveness in the treatment of PHCs and the additive methyl tert-butyl ether (MTBE). Three stabilizers (citrate, phytate, silica [SiO2]) were tested to determine if the stabilizers could enhance and extend the treatment life of H2O2 within saline groundwater. To determine the effect of salinity on the three stabilizers, groundwater and aquifer samples were collected from two saline locations that had different salinity (total dissolved solids of about 7,000 mg/L and 18,000 mg/L). Specific target chemicals for treatment were water soluble, mobile components of gasoline including benzene, toluene, ethylbenzene, xylenes, (BTEX) and MTBE. Previous studies using unactivated persulfate indicated that the PHCs within the groundwater could be oxidized, however, only limited oxidation of the MTBE could be affected. The results of the laboratory tests indicated that greater than 95 percent of the target hydrocarbons were removed within 7 days of treatment. Microcosms with citrate-stabilized H2O2 demonstrated a significantly faster and greater decline with most hydrocarbon concentrations reaching 400 mg/L to 90 percent) being measured in the citrate-stabilized microcosms. Unfortunately, H2O2 oxidation in the microcosms also resulted in production of up to 40 mg/L TBA or approximately 10 percent of the MTBE oxidized.

Enhanced simultaneous removal of MTBE and TCE mixture by Paracoccus sp. immobilized on waste silica gel

Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by the coexistence of chlorinated aliphatic contaminants such as trichloroethylene (TCE). This study reports for the first time an indigenous Paracoccus sp. using MTBE as a sole carbon source while cometabolizing TCE from the mixture. The culture was originally enriched and isolated from the sludge sample at a regional wastewater treatment plant in Macau Special Administrative Region (SAR), China. Waste silica gel was used as a matrix for the microbial immobilization. The effects of different concentrations of MTBE and TCE on the removal efficiencies were investigated, together with their interactions during the bioremoval process, as well as the effects of pH and temperature on MTBE and TCE removal rates. The adsorption kinetics of contaminants on silica gel was also evaluated and the adsorption capacities of MTBE (50 mg l−1) and TCE (50 mg l−1) were 0.42 mg g−1 and 0.65 mg g−1, respectively. In the immobilized system, TCE (20 mg l−1) was removed to non-detectable level while the highest removal efficiency for MTBE (40 mg l−1) was 70.2 ± 3.1%.

(Liquid + liquid) equilibria of methanol + ethylbenzene + isooctane + methy tert-butyl ether quaternary system at T = 303.15 K

Tie line data of {methanol + methyl tert-butyl ether + isooctane} ternary systems were obtained at T = 303.15 K, while data for {methanol + ethylbenzene + isooctane} were taken from literature. The ternary system {methanol + methyl tert-butyl ether + ethylbenzene} and {methyl tert-butyl ether + ethylbenzene + isooctane} were completely miscible. A quaternary system {methanol + ethylbenzene + isooctane + methyl tert-butyl ether} was also studied at the same temperature. In order to obtain equilibium data of the quaternary system, four quaternary sectional planes with several methyl tert-butyl ether/methanol ratios were studied. The effect of the addition of methyl tert-butyl ether on the liquid-liquid equilibrium data of {methanol + ethylbenzene + isooctane} ternary system has been investigate at the same temperature. The distribution curves for ternary and quaternary system was analysed. For the quaternary system {methanol + ethylbenzene + isooctane + methyl tert-butyl ether}, experimental data demonstrated that the distribution coefficient of ethylbenzene between the hydrocarbon and methanol phase on a methyl tert-butyl ether–free basis slightly increases with the increase of methyl tert-butyl ether/methanol ratio. Ternary experimental results were correlated with the UNIQUAC and NRTL equation. The NRTL equation is more accurate than the UNIQUAC equation for the ternary systems studied here. The equilibrium data of three ternary systems were used for determining interactions parameters for the UNIQUAC equation. The UNIQUAC equation fitted to the experimental data appeared to be more accurate than the UNIFAC method for the same quaternary system.

ChemInform Abstract: Laccase/2,2,6,6‐Tetramethylpiperidinoxyl Radical (TEMPO): An Efficient Catalytic System for Selective Oxidations of Primary Hydroxy and Amino Groups in Aqueous and Biphasic Media.

AbstractThe reaction can be scaled up.

Microbial toxicity of methyl tert-butyl ether (MTBE) determined with fluorescent and luminescent bioassays

The inhibitory effects of the fuel additive methyl tert-butyl ether (MTBE) and potential degradation products tert-butanol (TBA) and formaldehyde was examined using mixed microbial biomass, and six strains of bioluminescent bacteria and yeast. The purpose was to assess microbial toxicity with quantitative bioluminescent and fluorescent endpoints, and to identify sensitive proxies suitable for monitoring MTBE contamination. Bioluminescent Aliivibrio fischeri DSM 7151 (formerly Vibrio fischeri) appeared highly sensitive to MTBE exposure, and was a superior test organisms compared to lux-tagged Escherichia coli DH5α, Pseudomonas fluorescens DF57-40E7 and Saccharomyces cerevisiae BLYR. EC10 and EC50 for acute MTBE toxicity in A. fischeri were 1.1 and 10.9mgL−1, respectively. Long term (24h) MTBE exposure resulted in EC10 values of 0.01mgL−1. TBA was significantly less toxic with EC10 and EC50 for acute and chronic toxicity >1000mgL−1. Inhibition of bioluminescence was generally a more sensitive endpoint for MTBE toxicity than measuring intracellular ATP levels and heterotrophic CO2 assimilation. A weak estrogenic response was detected for MTBE at concentrations ⩾3.7g L−1 using an estrogen inducible bioluminescent yeast strain (S. cerevisiae BLYES). Microbial hydrolytic enzyme activity in groundwater was affected by MTBE with EC10 values of 0.5–787mgL−1, and EC50 values of 59-3073 for alkaline phosphatase, arylsulfatase, beta-1,4-glucanase, N-acetyl-beta-d-glucosaminidase, and leucine-aminopeptidase. Microbial alkaline phosphatase and beta-1,4-glucanase activity were most sensitive to MTBE exposure with EC50⩽64.8mgL−1. The study suggests that bioassays with luminescent A. fischeri, and fluorescent assays targeting hydrolytic enzyme activity are good candidates for monitoring microbial MTBE toxicity in contaminated water.

Inside Cover Picture: Laccase/2,2,6,6-Tetramethylpiperidinoxyl Radical (TEMPO): An Efficient Catalytic System for Selective Oxidations of Primary Hydroxy and Amino Groups in Aqueous and Biphasic Media (Adv. Synth. Catal. 10/2014)

The inside cover picture, provided by Dbaz-Rodrbguez et al., illustrates the oxidization of alcohols, diols or amino alcohols in buffer solution under aerobic conditions using the laccase from Trametes versicolor together with 2,2,6,6-tetramethylpiperidinoxyl radical (TEMPO). This practical and efficient methodology promotes the chemoselective oxidation of hydroxy or amino groups, leading to aldehydes, lactones, hemiaminals or lactams in good yields. Addition of methyl tert-butyl ether allows the TEMPO loading to be reduced, also enhancing the solubility of hydrophobic compounds. Details of this work can be found in the Update on pages 2321–2329 (A. Dbaz-Rodrbguez, L. Martbnez-Montero, I. Lavandera, V. Gotor, V. Gotor- Fernndez, Adv. Synth. Catal. 2014, 356, 2321–2329; DOI: 10.1002/adsc.201400260).

Influence of Selected Surfactants and High-Octane Oxygen Components on Water Content, Electrolytic Conductivity in Gasoline, and Interfacial Tension in the Water/Gasoline System

The influence of selected surfactants and oxygen containing components on solubility of water, electrolytic conductivity in gasoline, and interfacial tension in the water/gasoline system was studied. Anionic sodium bis-(2-ethylhexyl)sulfosuccinate (AOT), the branched alkylamine Primene JM-T, and some hydrophilic additives (alcohols and methyl tert-butyl ether) were examined. Slight amounts of amphiphilic substances can improve the solubility of water, and they may cause the association phenomena with the formation of reverse micelles. Hydrophilic groups of the compounds are located inside the micelles, in which the water pools can be contained. Surfactant aggregates and droplet clusters are contained in the microemulsion solution due to the dipolar interaction between the dispersed droplets. The formation of these structures induces an increase in the solubility of water in gasoline. The improvement of electrolytic conductivity depends on the type and concentration of surfactants and hydrophilic additives. Conductivity is very sensitive to microemulsion structure and it significantly increases because of the presence of reverse micelles, which are able to transport charges. Correlation between conductivity, water content, and interfacial tension has been analyzed. On the basis of the calculated coefficients, the closest correlation between these parameters was osberved in the case of the addition of AOT and hydrophilic components.

Structural and kinetic characterization of two 4-oxalocrotonate tautomerases in Methylibium petroleiphilum strain PM1

Methylibium petroleiphilum strain PM1 uses various petroleum products including the fuel additive methyl tert-butyl ether and straight chain and aromatic hydrocarbons as sole carbon and energy sources. It has two operons, dmpI and dmpII, that code for the enzymes in a pair of parallel meta-fission pathways. In order to understand the roles of the pathways, the 4-oxalocrotonate tautomerase (4-OT) isozyme from each pathway was characterized. Tautomerase I and tautomerase II have the lowest pairwise sequence identity (35%) among the isozyme pairs in the parallel pathways, and could offer insight into substrate preferences and pathway functions. The kinetic parameters of tautomerase I and tautomerase II were determined using 2-hydroxymuconate and 5-(methyl)-2-hydroxymuconate. Both tautomerase I and tautomerase II process the substrates, but with different efficiencies. Crystal structures were determined for both tautomerase I and tautomerase II, at 1.57 and 1.64Å resolution, respectively. The backbones of tautomerase I and tautomerase II are highly similar, but have distinct active site environments. The results, in combination with those for other structurally and kinetically characterized 4-OT isozymes, suggest that tautomerase I catalyzes the tautomerization of both 2-hydroxymuconate and alkyl derivatives, whereas tautomerase II might specialize in other aromatic hydrocarbon metabolites.

Molecular interaction, co-solubilization of organic pollutants and ecotoxicity of a potential carcinogenic fuel additive MTBE in water

We study the molecular properties and ecological consequences of a most common gasoline oxygenate, and widespread carcinogenic environmental threat, methyl tert-butyl ether (MTBE) upon inclusion in water. Our study shows the change of bulk properties like densities, viscosities and refractive indices of binary mixtures of water and MTBE at temperatures from 10°C to 50°C and over the entire composition range, under atmospheric pressure using densimetry, viscometry and refractive index measurement. The studies are clear indicative of the association of MTBE in the hydrogen bonding network and possible MTBE clustering in the aqueous solution. While, dynamic light scattering studies confirm the formation of micro-droplets (micelle-like) of MTBE in water, which still persist at 70°C (much above the boiling point of pure MTBE, 55.2°C), FTIR and Raman spectroscopies have distinctly unrevealed the molecular interaction of MTBE with water molecules. Co-solubilization of other potential hazardous organic matters (anthracene, naphthalene, benzo[α]pyrene and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM)) in the MTBE–water mixture has also been studied. Raman spectroscopic studies confirm the micelle-like cluster of MTBE to be a potential host of the organic pollutants in the aqueous environments. The picosecond-resolved spectroscopic studies also confirm localization of DCM in the ground state, in the MTBE cluster. Our studies also show the ecotoxic effect of MTBE in model eukaryotic microorganism yeast in aqueous environments.

Biodegradation of MTBE by Achromobacter xylosoxidans MCM1/1 induces synthesis of proteins that may be related to cell survival

The gasoline additive methyl tert-butyl ether (MTBE) can contaminate groundwater and soil. In order to eliminate it, several methods are being developed, among which bioremediation – that is, the addition of microbial cultures that can degrade the compound – holds promise. Our laboratory has identified Achromobacter xylosoxidans MCM1/1 as an MTBE-degrading bacterial strain. It degrades 78% of this chemical in 5 days. In this study we also analyze the effects of MTBE on the biology of A. xylosoxidans MCM1/1 and compare its proteomic profile after incubation with MTBE with that of unchallenged bacteria. The 2D proteomic analysis shows that the following four proteins are induced by MTBE: 50S ribosomal protein L10, amino acid-binding periplasmic protein, ATP synthase and endoribonuclease L. Characterizing the bacterial response to MTBE at the biochemical level identifies proteins that can be used by biocatalysts for soil and water bioremediation.

Ether oxygenate additives in gasoline reduce toxicity of exhausts

Fuel additives can improve combustion and knock resistance of gasoline engines. Common additives in commercial fuels are “short-chain, oxygen containing hydrocarbons” such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE). Since these additives change the combustion characteristics, this may as well influence toxic effects of the resulting emissions. Therefore we compared toxicity and BTEX emissions of gasoline engine exhaust regarding addition of MTBE or ETBE. Non-reformulated gasoline served as basic fuel. This fuel was supplemented with 10%, 20%, 25% and 30% ETBE or 15% MTBE. The fuels were combusted in a gasoline engine at idling, part load and rated power. Condensates and particulate matter (PM) were collected and PM samples extracted with dichloromethane. Cytotoxic effects were investigated in murine fibroblasts (L929) using the neutral red uptake assay and mutagenicity using the bacterial reverse mutation assay. BTEX emissions were analyzed by gas chromatography. Results PM-extracts showed mutagenicity with and without metabolic activation. Mutagenicity was reduced by the addition of MTBE and ETBE, 10% ETBE being most effective. The condensates produced no significant mutagenic response. The cytotoxicity of the condensates from ETBE- and MTBE-reformulated fuels was reduced as well. The BTEX content in the exhaust was lowered by the addition of MTBE and ETBE. This effect was significantly related to the ETBE content at rated power and part load. Conclusions Addition of MTBE and ETBE to fuels can improve combustion and leads to decreased toxicity and BTEX content of the exhaust. Reduction of mutagenicity in the PM-extracts is most probably caused by a lower content of polycyclic aromatic hydrocarbons.

The Effects of MTBE/Ethanol Additives on Toxic Species Concentration in Gasoline Flame

Methyl tert-butyl ether (MTBE) and ethanol as gasoline fuel additives can enhance gasoline fuel octane value. This study evaluates the effects of these oxygenated additives (MTBE and ethanol) at 10% by volume on the main combustion intermediates in a low-pressure laminar premixed gasoline flame using synchrotron radiation. The photoionization mass spectra of three flames were presented, and the temperatures of flames were measured by a thermocouple. The relative concentrations of five typical combustion toxic species in the gasoline, gasohol, and MTBE/gasoline flame were compared. It is observed that ethanol and MTBE both delay the oxidation of aromatics in gasoline, and MTBE plays a more obvious role than ethanol. It is also shown that the addition of ethanol leads to an increased concentration of acetaldehyde, whereas the addition of MTBE has no significant effect on the concentration of acetaldehyde. The results obtained provide data for the analysis of intermediates and radicals in flames, which is of...

Numerical study of the effect of oxygenated blending compounds on soot formation in shock tubes

This numerical study deals with the influence of blends on the amount of soot formed in shock tubes, which were simulated by assuming a homogeneous plug flow reactor model. For this purpose, first, the reaction model used here was validated against experimental results previously obtained in the literature. Then, the soot volume fractions of various mixtures of methyl tert-butyl ether (MTBE)–benzene, isobutene–benzene, methanol–benzene, and ethanol–benzene diluted in argon were simulated and compared to the results of benzene–argon pyrolysis at 1721 K and 5.4 MPa. For MTBE, isobutene, methanol, and ethanol, small amounts of additives to benzene–argon mixtures promoted soot formation, for the shock tube model assumed, while higher concentrations of these additives led to smaller soot volume fractions in comparison to pure benzene–argon pyrolysis. The most significant soot promotion effect was found for the additives MTBE and isobutene. The channel for MTBE decomposition producing isobutene and methanol is very effective at temperatures beyond 1200 K. Thus, both MTBE–benzene and isobutene–benzene mixtures diluted in argon showed rather similar behavior in regard to soot formation. Special emphasis was directed toward the causes for the concentration-dependent influence of the blends on the amount of soot formed. Aromatic hydrocarbons and acetylene were identified as key gas-phase species that determine the trends in the formation of soot of various mixtures. From reaction flux analysis for phenanthrene, it was deduced that the combinative routes including phenyl species play a major role in forming PAHs, especially at early reaction times. It is found that the additives play an important role in providing material to grow side chains, such as by reaction channels including phenylacetylene or benzyl, which are confirmed to form aromatic hydrocarbons and thus to influence the amount of soot formed, particularly when the concentrations of the blends are increased.

Adsorption and Abiotic Transformation of Methyl tert -Butyl Ether through Acidic Catalysts

The fuel additive methyl tert-butyl ether (MTBE) is sometimes considered to be a recalcitrant compound in groundwater. Due to MTBE’s relatively poor adsorption and low volatility, interest is growing in new remediation methods which provide an alternative to using activated carbon or stripping techniques. This study addresses the abiotic degradation (hydrolysis) of MTBE to the intermediate tert-butanol (TBA). Two selected materials with acidic properties were shown to hydrolyze MTBE in batch tests at moderate pH values. The sorption of MTBE and TBA was estimated with Freundlich isotherms. Isotherms and TBA formation were used to calculate MTBE degradation. In another experiment, TBA was degraded aerobically by microorganisms. Since TBA seems to be more easily available as a carbon source to microorganisms than MTBE, the catalytic transformation of MTBE to TBA and methanol could enhance the natural attenuation of MTBE.