The flow reactor oxidation of C1−C4 alcohols and MTBE

Experimental results are presented for the flow reactor oxidation of methanol, ethanol, normal- and iso-propanol, tert-butyl alcohol (TBA), and methyl tert-butyl ether (MTBE) at initial temperatures of 1020–1120 K and at atmospheric pressure. In comparison to alkanes, alcohols have a more complex oxidation mechanism, which involves the production of both oxygenated and nonoxygenated intermediates directly from the fuel. The ratio of dehydration to dehydrogenation observed depends on the molecular structure of the fuel. Primary alcohols are more susceptible to dehydrogenation than to dehydration, because of the weakness of the α C−H bonds. The direct production of aldehydes from primary alcohols causes these fuels to have much shorter reaction times than do the corresponding alkanes. By contrast, tertiary alcohols are highly susceptible to unimolecular dehydration. Since the dominant intermediates are alkenes, the chemistry closely resembles that of non-oxygenated hydrocarbons. Secondary alcohols react both by dehydration to alkenes and by dehydrogenation to ketones. MTBE decomposes directly to methanol + isobutene. These findings are summarized in a general mechanism for alcohol fuel oxidation. Methanol is observed to have the unique property that nearly half of its heat release occurs before the CO peak.