MTBE mechanism

In a simulated spill, groundwater was spiked with BTEX, MTBE, and chloride as marker, and injected into a sandy aquifer (Schirmer and Barker 1998). Whereas the level of BTEX fell, loss of MTBE was much slower, and only ca. 3% remained after 8 years, although the mechanism of its loss was not resolved. 

Construct a mechanism that shows why methyl tert-butyl ether (MTBE), a common gasoline additive, oxidizes in air to give formaldehyde as well as acetone, fert-butyl formate (HC(0)OC(CH 3),), and methyl acetate (CH3C(0)0CH3). 

We sponsored a study by the environmental laboratory of tlie University of Maine in Orono. The study deteimined that HPUR had the capacity to extract about 3.5 mg of MtBE per gram of hydrophilic foam. The university and others attributed this to a solvent extraction mechanism based on the fact that the extraction units are noted in milligrams per gram of foam. If the reaction were purely a surface phenomenon, the units would have been stated in milligrams per unit of area. 

Kang J-W, Hoffmann MR. Kinetics and mechanism of the sonolytic destruction of MTBE by ultrasonic irradiation in the presence of ozone. Environ Sci Technol 1998 32 3194-3199. 

Show all of the steps in the mechanism for the formation of MTBE from methanol and isobutylene. 

Scheme 5.3 Solvolysis of tert-butylbromide in methanol produces MTBE via an SN1 mechanism.

As alluded to above, El reactions are integrally related to SN1 reactions by virtue of the carbocations common to both mechanisms. Thus, revisiting the solvolysis reaction leading to the conversion of tert-butyl bromide to MTBE illustrated in Scheme 6.2, we understand how formation of isobutylene occurs. Formation of isobutylene only occurs through the El process and comprises approximately 20 percent of the reaction mixture. 

Alcohols add to alkenes, forming ethers, using the same mechanism. Addition of CH3OH to 2-methylpropene, for example, forms tert-butyl methyl ether (MTBE), a high octane fuel additive described in Section 3.4C. 

Industrial experience has shown that this kind of plant, owing to the very high flexibility of the WCTR, can be switched easily from ETBE to MTBE production, and vice versa, without any reduction of feed rate and with few mechanical modifications. 

Methanol, ethanol, and methy t-butyl ether (MTBE) are blended Into some commercial gasolines. It was Important to determine the effects of such blends on automotive elastomers especially those used In the fuel system. A summary of the results of our studies [1] and detailed data on the effects of methanol/gasollne mixtures on sixteen elastomers [2] have already been published. This paper presents detailed results of our Investigation of the effects of ethanol and MTBE mixtures with gasoline on mechanical and swell properties of automotive elastomers. Comparisons will be made with the effects of methanol/gasollne mixtures on elastomers. Experimental... 

The gas composition (volume) was n-pentane 0.6-1.3 % oxygen 0-20 % helium 5 % balance nitrogen. Total flow 30 cm3, min l (Hourly Space Velocity 6000 h l). Brooks mass flow controllers were used to control air and helium stream. MTBE was introduced into the n-pentane/air mixture using a mechanical injector and a tube evaporator kept at about 150 °C. The delay for the step-wise change of the MTBE feed to reach the reactor zone was about 2 minutes. The outlet of the reactor prior to analysis was kept at between 140 and 150 °C, so the condensation of the products at the concentration levels produced at the catalytic test was satisfactorily prevented. 

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