Quantitative in-situ infrared spectroscopy for the kinetic study of the resin-catalyzed dehydration of t-butyl alcohol
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abstract
Methyl tert-butyl ether (MTBE) represents an important anti-knocking blending agent in reformulated gasolines. MTBE can be formed by acid-catalyzed addition of methyl alcohol to isobutylene using a commercially available sulfonated styrene-divinyl benzene resin catalyst. The related acid-catalyzed dehydration of t-butyl alcohol (TBA) to synthesize isobutylene and water is the subject of this in situ study of kinetics. Kinetics of the resin-catalyzed dehydration of t-butyl alchol to isobutylene and water are difficult to study spectroscopically due to light scattering by solid particle interference, causing a variation of the IR beam pathlength and intensity. In this work, the nature of the internal reflectance experiment prevents interference by the solid resin and allows the work to be quantitative. Kinetic information was extracted from infrared reaction spectra using a partial linear squares (PLS) method based on multivarient statistics to correlate the absorbance to the weight% of TBA. Data were fitted to a rate law that accounted for the effect of water and methylcyclohexane (MCH) diluent. A standard Langmuir-Hinshelwood-Hougen-Watson model has been extended to describe the significant inhibiting effect of water.