Microsecond Catalytic Partial Oxidation of Alkanes

Abstract

A single layer of woven platinum-10 percent rhodium gauze was used as a catalyst for the partial oxidation of ethane, propane, n-butane, and isobutane. This configuration produced oxygen conversions of equal to or greater than 90 percent and had high selectivity to olefins and oxygenated hydrocarbons at contact times as short as 10 microseconds at atmospheric pressure. This reactor operates by rapid chemical heating (∼5 microseconds) followed by rapid quenching to avoid homogeneous reactions, which decompose products. Mixing of the cold unreacted gas passing between the gauze wires with the hot product gas results in rapid quenching (∼200 microseconds) of the products from ∼800° to ∼400°C. The rapid quenching avoids successive homogeneous decomposition reactions of unstable products such as olefins and aldehydes but still allows homogeneous chain reactions that produce these species. The strong variations in products with the feed alkane showed that the reaction pathways operating at ∼10⁻⁵ seconds are quite different than those operating at longer residence times. These results could have a significant effect on the direct conversion of alkanes to oxygenates such as formaldehyde.