Partial oxidation of CH4 to synthesis gas using Ni-catalyst/Au|YSZ|Ag electrochemical membrane reactor

Spc-Ni/MgAl (spc-: solid phase crystallization method) catalyst has been prepared from Mg-Al hydrotalcite-like compounds containing Ni at the Mg site as the precursors and successfully used as a catalyst on an electrochemical membrane reactor for partial oxidation of CH4 at 1173 K. The precursors based on [Mg2+A1−xl3+(OH)2x]x+(CO3−)x·mH2O, in which a ratio of Mg/Al varied and a part of Mg2+ ions were replaced by Ni2+ ions, were prepared by co-precipitation method, thermally decomposed, calcined and reduced to spc-Ni/MgAl catalyst. The electrochemical reactor, using yttria-stabilized zirconia (YSZ) as a solid electrolyte, has been employed as an oxygen permeable membrane reactor. The Ni catalyst coupled with Au paste was used as the catalyst-anode, while Ag paste was used as the cathode of the electrochemical cell. The reaction was carried out over the catalyst-anode film under oxygen pumping through the YSZ, and the results were compared with those obtained by various supported Ni catalysts prepared by impregnation (imp-) method. Spc-Ni/MgAl catalysts showed higher activity than imp-Ni catalysts and the best composition of metals in the catalyst was spc-Ni0.5/Mg2.5Al. This catalyst showed the CH4 conversion following the thermodynamic equilibrium between 1023 and 1173 K, while the other catalysts of different compositions or imp-Ni catalysts showed a clear decrease in the CH4 conversion with decreasing temperature. Moreover, spc-Ni0.5/Mg2.5Al catalyst showed stable activity during the reaction for 40 h. It is concluded that the high and stable activity for the partial oxidation of CH4 is due to highly dispersed and stable Ni metal particles formed on spc-Ni0.5/Mg2.5Al catalyst film.