Methyl Tert-butyl Ether Decomposition Research Articles

Photocatalytic degradation of tert-butyl alcohol and tert-butyl formate using palladium-doped zinc oxide nanoparticles with UV irradiation

Methyl tert-butyl ether (MTBE) is a well-known environmental pollutant. Its removal from water bodies is a challenge associated with ensuring the chemical is present only within the prescribed limits. Tert-butyl alcohol (TBA) and tert-butyl formate (TBF) are the two main intermediate (stable and toxic) compounds that are obtained during the decomposition of MTBE. The accumulation of these intermediates in water bodies raises serious issues about their chemical toxicity, as they are suspected carcinogens in humans. In this work, palladium-doped zinc oxide is utilised as a photocatalyst to decompose these contaminants in the presence of UV light. These photocatalysts have been found to efficiently degrade 100 ppm aqueous solutions of TBA and TBF using 100 mg of each of these photocatalysts and UV irradiation over a period of five hours.

Decomposition of Methyl Tert-Butyl Ether by Adding Hydrogen in a Cold Plasma Reactor

ABSTRACTMethyl tert-butyl ether (MTBE) is extensively used as an oxygenate and octane enhancer in gasoline. Its release to the environment has generated great public and governmental concern. In this study, we give a brief review of the decomposition of air toxics by the application of radio frequency (RF) plasma reactors and then present our study on decomposition of methyl tert-butyl ether by adding hydrogen in a cold plasma reactor. Based on our references, there are four types of the application in the RF plasma reactors are discussed, including: (i) Application I.: Converting methane, decomposing carbon dioxide, ethoxyethane, and ethylene oxide; (ii) Application II.: Decomposing methyl chloride, 1,1-C2H2Cl2, and CH2Cl2; (iii) Application III.: Decomposing dichlorodifluoromethane, CHF3, CH2F2, CCl2F2, and BF3; (iv) Application IV.: Decomposing dichlorodifluoromethane, CH3SH, CS2, SF6, and SF6 + H2S mixture. Moreover, this study demonstrates the feasibility of applying a radio frequency (RF) plasma reactor for decomposing and converting MTBE. Experimental results indicate that the decomposition efficiency (ηMTBE) and the fraction of total input carbon converted into CH4, C2H2 and C2H4 (FCH4+C2H2+ C2H4) increased with the input power and decreased as both the H2/MTBE ratio and the MTBE influent concentration in the MTBE/H2/Ar plasma environment increased. Interestingly, applying radio frequency plasma to the decomposition of MTBE while adding hydrogen constitutes alternative method of decomposing and converting MTBE into CH4, C2H4, C2H2, iso-butane and iso-butene.

Effect Factors on the Degradation of MTBE with Fenton Reagent

The fundamentals of the Fenton reagent-based degradation methyl tert-butyl ether (MTBE) in batch reactors under initially anaerobic conditions are discussed in this work, and the objective of the study was to elucidate the effect of the FR to MTBE molar ratio, pH, initial MTBE concentration, H 2 O 2 concentration and inorganic anions on MTBE decomposition. The results show that the added amount of FR proved to be an important controlling parameter of the overall MTBE degradation efficiency. Under the conditions investigated in the present study at pH 3.0 and equimolar ratio of Fe 2 + to H 2 O 2 , FR to MTBE molar ratio of 6:1 was the minimum required to achieve complete MTBE degradation. The MTBE decay curves at four different initial MTBE concentrations with a constant initial FR concentration, the decomposition ratio arrived by 90.8%, 82.3%, 71.6% and 41.8%, while the initial MTBE concentration at 10.0, 20.0, 40.0 and 60 mg/L, respectively. The amount of hydrogen peroxide has a positive influence on the degradation rate, at low peroxide levels, increasing the amount of hydrogen peroxide results in the generation of more hydroxyl radicals, and thereby enhances the decay rate of MTBE. Moreover, the Fenton reaction is extremely sensitive to the inorganic anions present in the solution. In the case of the PO 4 3 − ions, oxidation is clearly inhibited, but the addition of SO 4 2 − influences the reaction to a much smaller extent, the anions suppress the decomposition of MTBE in the following sequence: PO 4 3 − >HPO 4 2 − >H 2 PO 4 − >Cl − >SO 4 2 − .

Catalytic destruction of methyl tertiary butyl ether (MTBE) using oxidized carbon

Decomposition of methyl tert-butyl ether (MTBE) in the gas phase was studied using carbon catalysts with chemically modified surface. Carbon samples with different surface chemical properties were obtained from commercial activated carbon D43/1 (CarboTech, Essen, Germany) by oxidation in liquid phase with various oxidants as well as in air. The catalytic tests were performed in a flow reactor at a temperature range of 353–473 K. Isobutene and methanol are the only products of the MTBE decomposition. The generation of surface acidic oxides considerably enhances the catalytic activity of the carbons. However, the activity is controlled not only by the number and strength of acidic groups, but also by their accessibility. The most active carbon is that oxidized with air at 673 K, which contains pores wider than the pores of other oxidized carbons.

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.

Effect of Chlorides and Sulfates on the Performance of a Fe 3+/H 2O 2 Fenton‐Like System in the Degradation of Methyl Tert‐Butyl Ether and its Byproducts

The effect of chloride and sulfate ions on the oxidation of methyl tert-butyl ether (MTBE) and its degradation products in a Fenton-like system was studied. Although both chloride and sulfate ions inhibited the decomposition of H202, chlorides were found to be the more effective inhibitor of MTBE degradation. In the presence of sulfates, MTBE decomposition can be attributed to oxidation not only by hydroxyl radicals, but also likely by SO4*- species. In the presence of chloride ions, it is possible that the dichloride radical is formed, which is less reactive than OH*. In the system under investigation, t-butyl alcohol was found to be the major byproduct, followed by t-butyl formate and acetone. The degradation rates of all intermediates and their inhibition in the presence of inorganic ions are similar to those obtained for MTBE, although their distributions are related to the concentrations of inorganic salts added.

Novel Heteropolyacid Nanoporous Carbon Reactive Barriers for Supra-Equilibrium Conversion and In Situ Component Separation

A novel type of thin-film catalyst has been developed that combines high activity with selective transport across a micron-scale membrane film. Nanoporous carbon was used as a support for 12-tungstophosphoric acid with composite films synthesized by two distinct approaches: in-situ polymerization and adsorption from solution. Ion sputtering and XPS were used in combination to characterize the high dispersion of the catalyst within the film in the former case and a gradient in catalyst concentration in the latter. Both methods produce intact Keggin structures as demonstrated by FTIR spectroscopy. Gas permeation experiments indicate a preservation of separation capacity with O2/N2 permeability ratios as high as 6.5. The catalytic films were benchmarked using the decomposition of methyl tert-butyl ether at 55 °C and demonstrate remarkable increases in both conversion and simultaneous separation of decomposition products. Integrated conversions in a semi-batch reactor configuration far exceed the thermodynam...

Radiation induced decomposition of methyl tert-butyl ether in water in presence of chloroform: Kinetic modelling

The destruction of methyl tert-butylether (MTBE) in water in the presence of chloroform has been studied using 60Co gamma irradiation. Distilled water solutions at three different concentrations of the individual solutes MTBE and CHCl 3 were irradiated for various times to provide dose destruction information. Then, the irradiation of a mixture of MTBE (at two different concentrations) and CHCl 3 (at one concentration) was conducted. A kinetic model was used incorporating recently determined bimolecular rate constants to describe the destruction of the MTBE and CHCl 3 individually and in mixtures. These studies were conducted in distilled water simplifying the radiation chemistry significantly. With the improvements in the modelling capability, we are closer to being able to use the model to study “real-world” mixtures in natural waters.

Heteropolyacid (HPA)‐Polymer Composite Films as Heterogeneous Catalysts and Catalytic Membranes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Chemical oxidative degradation of methyl tert-butyl ether in aqueous solution by Fenton’s reagent

Degradation of methyl tert-butyl ether (MTBE) in aqueous solution by Fenton’s reagent (Fe 2+ and H 2O 2) was investigated. Effects of reaction conditions on the oxidation efficiency of MTBE by Fenton’s reagent were examined in batch experiments. Under optimum conditions, 15 mM H 2O 2, 2 mM Fe 2+, pH 2.8 and room temperature, the initial 1 mM MTBE solution was reduced by 99% within 120 min. Results showed that MTBE was decomposed in a two-stage reaction. MTBE was first decomposed swiftly based on a Fe 2+/H 2O 2 reaction and then decomposed somewhat less rapidly based on a Fe 3+/H 2O 2 reaction. The detection of Fe 2+ also supported the theory of the two-stage reaction for the oxidation of MTBE by Fenton’s reagent. The dissolved oxygen in the solution decreased rapidly in the first stage reaction, but it showed a slow increase in the second stage with a zero-order kinetics. A reaction mechanism involving two different pathways for the decomposition of MTBE by Fenton’s reagent was also proposed. Chemicals including tert-butyl formate, tert-butyl alcohol, methyl acetate and acetone were identified to be the primary intermediates and by-products of the degradation processes.

Quantum Chemical Investigation of the Koch Carbonylation of Methyl tert-Butyl Ether (MTBE)

Methyl tert-butyl ether (MTBE) is a widely used additive in oxygenated gasoline that has recently come under environmental pressure. Consequently, the demand for MTBE is likely to decrease in the future, and new uses for MTBE need to be explored. Production of methyl 2,2-dimethylpropanoate (methyl pivalate) via Koch carbonylation chemistry is an attractive option because methyl pivalate has been shown to be a fluid with a much lower ozone-forming potential than many other oxygenated solvents. Semiempirical, Hartree-Fock, MP2, and density functional theory calculations, believed to be the first on this system, indicated that the most energetically difficult step in this chemistry is the decomposition of MTBE to tert-butyl cation and methanol. Specific solvation effects were included in these calculations by inclusion of a small number of explicit solvent molecules, and nonspecific solvation effects were taken into account using a dielectric continuum model.

Heteropolyacid (HPA)-polymer composite films as heterogeneous catalysts and catalytic membranes

Preparation, characterization, and catalytic application of membrane-like heteropolyacid (HPA)-polymer composite films as heterogeneous catalysts and catalytic membranes were reported in this work. HPA-polymer composite film catalysts were prepared by a membrane preparation technique by blending HPA with polymer using a common or a mixed solvent. HPA-polymer composite film catalysts were cut into small pieces, and they were applied as heterogeneous catalysts to the liquid-phase tert-butyl alcohol (TBA) synthesis, to the vapor-phase ethyl tert-butyl ether (ETBE) synthesis, and to the vapor-phase ethanol conversion. It was observed that HPA catalysts were finely dispersed throughout the polymer supports, and the blending patterns of the composite film catalysts were different depending on the identity of solvent and polymer material used. The HPA-polymer composite films showed enhanced catalytic activities in these reactions compared to the mother HPAs. Pore characteristics of the composite film catalysts could be controlled by a conventional membrane preparation technique, and they were related to the catalytic performance of the film catalysts. Shell- and tube-type membrane reactors comprising inert polymer membranes and HPAs were designed and applied to the vapor-phase methyl tert-butyl ether (MTBE) decomposition. Simulation and experimental results revealed that polyphenylene oxide (PPO)-based membrane reactor showed the best performance, among some polymer membranes examined. Selective removal of methanol through the polymer membrane inhibited the unfavorable reverse reaction (MTBE synthesis), and at the same time accelerated the MTBE decomposition. Shell- and tube-type catalytic membrane reactors (CMRs) utilizing HPA-polymer composite catalytic membranes were also designed for the vapor-phase MTBE decomposition. Experimental results showed that HPA-polymer composite catalytic membranes not only showed catalytic reactivity for the reaction, but also were perm-selective for methanol with respect to isobutene and MTBE. It has been demonstrated that HPA-polymer composite catalytic membranes have potential application in a membrane reactor for the MTBE decomposition.

PHOTOCATALYTIC DESTRUCTION OF METHYL TERT-BUTYL ETHER IN THE GAS PHASE USING TITANIUM DIOXIDE

ABSTRACT The efficiency of the photocatalytic destruction of methyl tert-butyl ether (MTBE) in the gas-phase using UV light and titanium dioxide was studied. TiO2 was coated on the inner side of the photoreactor. Specifically, the effect of residence time (0.17–2.22 min), MTBE concentration (500–5000 ppm), oxygen concentration (0–20,000 ppm) and water vapor on MTBE conversion was examined. Acetone and tert-butyl formate were detected in the photoreactor effluent. The formation of by-products from MTBE decomposition was determined with gas chromatography–mass spectrometry. The residence time affected dramatically the MTBE photo-oxidation as well as by-products existence and configuration. The increase in MTBE concentration at the reactor inlet and the addition of water vapor to the reactants resulted in decreased MTBE conversions. Increasing oxygen concentration up to 10,000 ppm enhanced the photocatalytic process but a further increase to 20,000 ppm had an adverse impact on MTBE decomposition. In all cases, the by-product formation profiles were extremely dependent on photocatalysis parameters studied.

Effect of input power and feeding concentration on MTBE decomposition using an RF plasma reactor

The toxicology of the widely used oxygenated fuel additive methyl tert-butyl ether (MTBE) has recently attracted considerable interest in the public sector. In this study, a radio-frequency (RF) plasma reactor was used to decompose MTBE gas. The effects of two important plasma operational parameters – including power consumption per unit volume of the plasma (WD, W cm−3) and MTBE feeding concentration (CMTBE, %) – for MTBE decomposition were investigated in detail. The results show that the MTBE decomposition efficiency (ηMTBE) increases with increasing WD and with decreasing CMTBE. In this study, the results reveal that, in the MTBE/Ar plasma, the ηMTBE was over 99.9%, which occurred at the conditions of for WD = 0.96W cm−3, CMTBE = 3%, 20 Torr of operational pressure and a 100 cm3 · min−1 total gas flow rate. In particular, the effects of WD and CMTBE for the species detected in the effluent gas stream are carefully discussed. In addition, the deposition problem which occurred in the reactor was examined by means of Scanning Electron Microscopy (SEM). © 2002 Society of Chemical Industry

Design of H 3PW 12O 40–PPO (polyphenylene oxide) composite catalytic membrane reactor and its performance in the vapor-phase MTBE (methyl tert-butyl ether) decomposition

Experimental studies on the design of shell- and tube-type heteropolyacid (HPA)-polymer composite catalytic membrane reactors (CMR) and their applications to the vapor-phase decomposition of methyl tert-butyl ether (MTBE) were reported. H 3PW 12O 40 (PW) was used as a catalyst for the reaction, and polyphenylene oxide (PPO) was used as a membrane material. It was found that the single-phase (PW-PPO/Al 2O 3, type-1) and the composite (PW-PPO/PPO/Al 2O 3, type-2) catalytic membranes not only showed catalytic reactivity for the reaction, but also were perm-selective for methanol with respect to isobutene and MTBE. The selective removal of methanol through the catalytic membrane inhibited the unfavorable reverse reaction (MTBE synthesis), and at the same time accelerated the MTBE decomposition reaction. The PW-PPO/PPO/Al 2O 3 CMR showed a superior performance compared to the PW-PPO/Al 2O 3 CMR. The enhanced performance of PW-PPO/PPO/Al 2O 3 CMR was attributed to the intrinsic perm-selective capabilities of the PW-PPO catalytic membrane and the sub-layered PPO membrane. The PW-PPO/PPO/Al 2O 3 catalytic membrane with high PW loading was less perm-selective than that with low level of PW loading. Although the PW-PPO catalytic layer itself had a lower intrinsic activity than the bulk PW catalyst in a normal reactor, PW-PPO/PPO/Al 2O 3 catalytic membrane could be utilized in a membrane reactor to achieve higher MTBE conversions than equilibrium values by means of chemical equilibrium shift at high cut-off.

Low temperature catalytic decomposition and oxidation of MTBE

Catalytic combustion of methyl-tert-butyl-ether (MTBE) was studied in the gas-phase from an aqueous solution spiked with MTBE (1.1mM), to simulate actual remediation conditions. The solution of MTBE was sparged with an oxygen/helium gas, at a ratio of 1–4. The sparged gas stream of MTBE and water vapor was passed over catalysts utilizing Pt/Rh or Pd in conjunction with a mixed metal oxide based upon La1−xSrxMnO3. The results were compared to a commercial catalyst which contained a higher loading of Pt. The experiments with the catalysts were conducted over a temperature range of 80–500°C. Combustion to CO2 and water was observed in all cases, but by-product formation of isobutene and methanol was seen at lower temperatures for all of the catalysts tested, with the exception of the commercial catalyst. The catalyst with the lowest loading of Pt/Rh achieved the lowest temperature for complete oxidation of MTBE and its by-products.

Performance of shell and tube-type membrane reactors equipped with heteropolyacid-polymer composite catalytic membranes

Experimental studies on the performance of shell and tube-type membrane reactors equipped with heteropolyacid-polymer composite catalytic membranes were carried out for the vapor-phase decomposition of MTBE (methyl tert-butyl ether). Three types of catalytic membranes comprised of 12-tungstophosphoricacid (H 3PW 12O 40, PW) and polyphenylene oxide (PPO) were designed in this work. The PW-PPO/Al 2O 3 (type-1), PW-PPO/PPO/Al 2O 3 (type-2) and PW/PPO/Al 2O 3 (type-3) catalytic membranes not only showed catalytic reactivity for the reaction, but also were perm-selective for the reaction species. The selective removal of methanol through the catalytic membrane led to an equilibrium shift in a direction favorable to MTBE decomposition. Among three types of catalytic membrane reactor, the PW-PPO/PPO/Al 2O 3 (type-2) catalytic membrane reactor showed the best performance. The enhanced performance of the PW-PPO/PPO/Al 2O 3 (type-2) catalytic membrane reactor can be attributed to the intrinsic perm-selective capabilities of the PW-PPO catalytic membrane and the sub-layered PPO membrane.

Synthesis and Characterization of Heteropolyacid Nanoporous Carbon Membranes

Heteropolyacid nanoporous carbon membranes were synthesized by re-precipitation of 12-tungstophosphoric acid on a prefabricated nanoporous carbon film. The Keggin structure is maintained on and within the 8 μm film as inferred from FTIR spectroscopy and XRD. Gas permeation reveals that separation performance of the carbon membrane is maintained after deposition although total membrane flux decreases by nearly 40% for N2 permeation. Semi-batch membrane reactor performance in the decomposition of methyl tert-butyl ether at 55°C shows significant enhancement of the conversion with 96.5% compared with 64.1% for a non-selective membrane analog under the same conditions.

Performance of double-pipe membrane reactor comprising heteropolyacid catalyst and polymer membrane for the MTBE (methyl tert-butyl ether) decomposition

Simulation and experimental studies on the double pipe (shell and tube) polymer membrane reactors were examined for the vapor-phase methyl tert-butyl ether (MTBE) decomposition. H 3PW 12O 40 catalyst supported on silica was used as an active catalyst for the reaction. Polyphenylene oxide (PPO), polysulfone (PSF) or cellulose acetate (CA) membrane coated on the double-layered alumina tube was used as a constituent membrane. It was observed that permeabilities of methanol through each polymer membrane were higher than those of isobutene and MTBE regardless of the kind of polymer material used. The selective removal of methanol through polymer membrane shifted the chemical equilibrium toward a favorable direction in the model reaction. The MTBE conversions in the membrane reactors were much enhanced compared to the equilibrium conversions. The PPO membrane reactor showed the best performance under the experimental conditions. The simulation results on the performance of the membrane reactors were in good agreement with the experimental results within the error of ±5%. It was revealed from the simulation that the CA membrane reactor showed the best performance at high contact time whereas the PPO membrane reactor showed the best performance at low contact time in terms of MTBE conversion, isobutene yield and isobutene selectivity. It was also observed that the performance of membrane reactor was much improved with the decrease of coating amount of polymer membrane and reaction temperature, but with the increase of partial pressure of MTBE. It was concluded that the simulation program developed in this work described the performance of the membrane reactor very well for the vapor-phase MTBE decomposition.

Simulation and experimental study on the polymer membrane reactors for the vapor-phase MTBE (methyl tert-butyl ether) decomposition

Simulation and experimental studies on the polymer membrane reactor were examined for the vapor-phase MTBE (methyl tert-butyl ether) decomposition. A double pipe (shell and tube type) membrane reactor comprising 12-tungstophosphoricacid catalyst and polymer membrane was designed. The polymer membrane was coated on the porous alumina tube. Polyphenylene oxide (PPO), polysulfone (PSF) or cellulose acetate (CA) was used as a constituent membrane material. It was observed that permeabilities of methanol through each polymer membrane were higher than those of isobutene and MTBE regardless of the kind of polymer membrane used. The selective permeation of methanol through each polymer membrane shifted the chemical equilibrium toward the favorable direction in the MTBE decomposition reaction. MTBE conversions in the membrane reactors were much enhanced compared to the equilibrium conversions. The MTBE conversions were increased with the increase of reaction temperature and with the decrease of reaction pressure. Simulated results were in good agreement with the experimental results. The PPO membrane reactor showed the best performance in the experimental condition.