C-6 oxygenates from n-hexane in a single-gauze reactor

Partial oxidation of n-hexane in an autothermal single-gauze reactor can pr oduce 70% selectivity to oxygenated hydrocarbons, including > 50% selectivi ty to C-6 oxygenates with similar to 35% selectivity to 2,5-dimethyltetrahy drofuran at similar to 20% n-hexane conversion and 100% oxygen conversion E xperiments are performed with 40-mesh Pt-10%Rh single gauzes (similar to 10 0 mum wire diameter and similar to 630 mum spacing) at n-hexane-oxygen mola r ratios (C6H14/O-2) of 0.5-5.0, preheat temperatures of 100-300 degreesC, N-2 dilution of 10-75%, and flow rates of 1.0-3.5 standard liters per minut e. Oxygenates are optimized at C6H14/O-2 approximate to 2.5 and are favored by low preheat temperature, some dilution, and intermediate flow rate (cat alyst contact time). Catalytically assisted gas-phase reaction pathways are proposed for partial oxidation of n-hexane and compared to similar experim ents for cyclohexane and methylcyclohexane. The differences in product dist ributions can be qualitatively explained by the number of unique primary, s econdary, and tertiary carbon sites in cyclohexane, n-hexane, and methylcyc lohexane because the abundance of possible products grows quickly as the nu mber of distinct sites increases. Results suggest that initial H-atom abstr action rates for these alkanes increase in the order 1 < 2 < 3 degrees, whi le the overall reactivities increase in the order methylcyclohexane < cyclo hexane < n-hexane. The low reactivity of methylcyclohexane, despite its hig h initial rate of abstraction, is likely a result of the stability of the t ertiary radical. (C) 2000 Elsevier Science Ltd. All rights reserved.