Photocatalytic oxidation of gas-phase methyl tert-butyl ether and tert-butyl alcohol

Abstract

Adsorbed methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) were oxidized at room temperature by transient photocatalytic oxidation (PCO) on TiO2 and Pt-TiO2 catalysts; carbon dioxide, water, and acetone were the main gas-phase products. TBA oxidized faster than MTBE. Reaction products such as formic acid, which remained on the surface, were characterized by temperature-programmed desorption (TPD) and oxidation (TPO). The TiO2 catalyst was not a good oxidation catalyst in the dark, but both TBA and MTBE decomposed to form 2-methyl-1-propene (2-MP) during TPD, and MTBE decomposed much faster. The Pt/TiO2 catalysts had higher complete oxidation rates during PCO. Continuous-flow PCO of gas-phase MTBE and TBA was also carried out at 333-453 K on TiO2, and carbon dioxide, water, and acetone formed. Product distributions differed during transient and continuous-flow PCO because reaction products were displaced from the surface by reactants or other products. Continuous PCO of TBA proceeded faster in humid air than dry air, but MTBE oxidation was less sensitive to humidity. The TiO2 catalyst was stable during continuous PCO of MTBE, TBA, and acetone above 373 K, but gradually lost activity below 373 K; the catalyst could be regenerated by UV irradiation in the absence of gas-phase VOCs. © 2005 Elsevier B.V. All rights reserved.