The feasibility of n-butane partial oxidation to maleic anhydride (MA) over vanadium phosphorus oxide catalysts in an electrochemical membrane reactor in which an oxygen-ion-conducting electrolyte was used as the membrane was studied. Butane oxidation and oxygen separation were carried out simultaneously on the opposite surfaces of the membrane, and the oxygen flux transferred across the membrane was controlled by the external current between the two electrodes. At 751 K and with a current of 40 mA, the conversion of butane was 15−16%, and the selectivity to MA was about 39%. The selectivity and yield of MA increased with increasing applied current. The optimal reaction temperature was 750 ± 5 K, as a compromise among the ionic conductivity of the membrane, the polarization resistances of the electrodes, and the selectivity and the yield of MA.

The feasibility of the oxidative dehydrogenation of ethane to ethylene with alumina-supported vanadium oxide catalyst (VO x /γ-Al2O3) in an electrochemical packed-bed membrane reactor was investigated at temperatures between 500 and 620 °C with molar ratios of oxygen to ethane of 0.06−3.10. An oxygen-ion-conducting yttria-stabilized zirconia (YSZ) membrane was employed in a reactor of Au|YSZ|Pt, and the oxygen flux transferred across the membrane was controlled over the faradic coupling of oxygen-ion conduction and the external current between the electrodes. The oxidative dehydrogenation of ethane with electrochemically supplied oxygen in the membrane reactor was compared to that obtained with gaseous dioxygen in a conventional packed-bed reactor. The selectivity to ethylene was found to decrease as a function of supplied oxygen in both investigated operating modes. For all investigated oxygen/ethane molar ratios, the selectivity ratio, S CO 2 /S CO, was found to be clearly higher in the electrochemical than in the packed-bed reactor mode. The electrochemical oxygen supply significantly promoted CO2 formation, whereas the ethane conversion and ethylene selectivity were almost equal in the two investigated reactors. The experimental results indicate that, in the electrochemical operation, additional oxygen species exist in the system and are especially reactive in the total oxidation reactions.

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The partial oxidation of n-butane to maleic anhydride ͑MA͒ in a solid electrolyte membrane reactor was studied in three different operation modes: electrochemical membrane reactor ͑EMR͒, cofeed membrane reactor ͑CR͒, and mixed-feed membrane reactor ͑MMR͒. The EMR operation exhibited lower selectivity to MA but higher conversion of oxygen than the CR operation. The electrochemical oxygen pumping in the MMR operation led to decrease in the MA selectivity compared to the CR operation. By means of comparing the three operation modes, the electrochemically pumped oxygen was found to be more reactive but less selective to MA than gas-phase oxygen, which is directly related to the different reaction mechanisms between the CR and EMR operations. The butane oxidation occurred in the EMR involved not only the same catalytic reaction mechanism as in the CR but also an electrocatalytic reaction. A simplified catalytic and electrocatalytic reaction-mechanism scheme was proposed for the butane oxidation carried out in the EMR.Maleic anhydride ͑MA͒, produced by partial oxidation of n-butane over vanadium phosphorous oxide ͑VPO͒ catalyst, is a versatile monomer and an important chemical intermediate with many uses such as unsaturated polyester resins, lubricating oil additives, agricultural products, and pharmaceuticals. The oxidation of n-butane to MA is recognized as one of the most complex reactions involving light alkanes, 1-4 which includes eight hydrogen atoms abstraction and three oxygen atoms insertion with 14 electrons transferring. VPO catalyst is the unique catalyst used in this reaction. It is commonly accepted that the vanadium oxidation state of VPO catalyst plays an important role in the catalyst selectivity and activity and that the best VPO catalyst for MA production should possess an optimal V 4+ /V 5+ ratio. [5][6][7][8] Despite the fact that the oxidation of butane to MA has been intensively studied by numerous scientists, the respective roles of oxygen species in the selective and nonselective oxidations are still far from clear. 1 Gas-phase oxygen, lattice oxygen, and activated chemisorbed oxygen have been proposed as the possible active species in the formation of the desired product MA and undesired products CO x . [9][10][11][12][13] Though MA production processes have been commercialized in fixed-bed and fluidized-bed reactors, all these reactors still suffer from disadvantages such as the demand of high attrition resistance of the catalyst in fluidzed-bed reactors and the possible hot spots and explosive mixtures in fixed-bed reactors. Recently, in order to increase the MA selectivity and also to overcome the limitations of these conventional reactors, Mallada et al. 14,15 have intensively studied the application of inert porous membrane reactors to butane partial oxidation. In our previous work, 16,17 we have demonstrated the feasibility of MA synthesis in an electrochemical membrane reactor ͑EMR͒ using a dense solid oxide electrolyte membrane, where the oxygen required for the butane oxidation was su...

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