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Background: The formation of oygenates by partial oxidation of alkanes are major processes in the chemical industry. For instance, over 90% of the cyclohexane used annually is oxidized to produce intermediates for the production of polymers, mostly nylon 6 and 6,6. These nylon intermediates include cyclohexene, cyclohexanone, cyclohexanol, and adipic acid. The production of these chemicals is characterized by exceedingly long residence times (~1 hr) and inefficiencies of size, operating costs, and energy usage (and therefore emissions). In recent years, millisecond reactors employing Pt–10%Rh single-gauze catalysts have shown promise for high-throughput and autothermal production of oxygenates and olefins.
Sketch of the main reaction paths of partial oxidation of cyclo-hexane in the gas-phase (O'Connor et al.) Project: One of the processes, we study, is cyclohexane oxidation over a single-gauze catalyst that can produce >80% selectivity to oxygenates and olefins at 25% cyclohexane conversion and 100% oxygen conversion, with a residence time six orders of magnitude smaller than that for comparable liquid-phase industrial processes. The millisecond single-gauze reactor successfully couples catalytic and gas-phase chemistry to produce highly unstable, non-equilibrium species. A unique feature of the single-gauze chemical reactor is rapid preheat following by fast thermal quenching to prevent decomposition of reactive intermediates. A portion of the cyclohexane feed reacts completely on the surface, generating heat and free radicals which initiate a gas-phase reaction sequence. The homogeneous chain reactions producing desired oxygenated hydrocarbons and olefins are then thermally quenched by cold gases passing between the wires. Collaboration: L.D. Schmidt (University of Minnesota) Further information R. P. O´Connor, L.D. Schmidt, O. Deutschmann. Simulating Cyclohexane Millisecond Oxidation: Coupled Chemistry and Fluid Dynamics. AIChE J. 48 (2002) 1241-1256 |
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