Low temperature dry reforming of methane over Pt-Ni-Mg/ceria-zirconia catalysts

Low temperature dry reforming of methane was studied over platinum (0.2-2 wt.%) and/or nickel (8 wt.%) and magnesium (8 wt.%) immobilized onto a ceria-zirconia support. Ceria-zirconia (0.6:0.4) solid solutions were synthesized by precipitation and the metals were loaded by the incipient wetness method. XRD patterns demonstrated that the support was a cubic fluorite structure and Ni and Mg were deposited onto it. Temperature-programmed reduction showed that Pt addition substantially decreased the reduction temperature and the impact became less prominent with increasing Pt loading. The Ni-Mg/(Ce0.6Zr0.4)O-2 had the highest number of basic sites and the amounts decreased with the addition of platinum. The lowest CH4 and CO2 conversion (X-10) temperatures were achieved at 454 degrees C and 437 degrees C, respectively, using a 0.5% Pt-Ni-Mg/(Ce0.6Zr0.4)O-2 catalyst. This catalyst was optimum because it balanced between the enhanced reducibility and decreasing number of basic sites, which both occurred with increasing Pt loading. Dry reforming experiments also indicated that Pt decreased the reaction onset temperature for methane and CO2 and correlated to a slight decrease in the H-2:CO ratio (though still higher than for the 0.5% Pt-Ce0.6Zr0.4O2 control catalyst). Steady-state reaction experiments were conducted between 430 and 470 degrees C for the best catalyst and the results showed TOFs increasing from 2.69 to 4.74s(-1) with increasing temperature and minimal deactivation when left on stream for 100.5 h. A comparison to literature indicates that the Pt/Ni/Mg/Ce0.6Zr0.4O2 catalyst has among the highest activities, especially if Ir and Rh catalysts are not included. (C) 2015 Elsevier B.V. All rights reserved.