Abstract
Barium doping effect on the activity and stability of nickel-based catalysts, supported on yttria-stabilized zirconia (Ni-YZr), was investigated in dry reforming of methane. Catalysts were characterized by several techniques (nitrogen sorption, X-ray diffraction [XRD], scanning electron microscopy with energy dispersive X-ray, transmission electron microscopy [TEM], thermogravimetric analysis [TGA], temperature programmed oxidation, CO2-TPD, H-2-TPR) and were tested in a fixed-bed reactor at 800 degrees C and 42,000 mL/h g(cat). Barium played a crucial role in enhancing catalyst reducibility and CO2 adsorption at high temperatures, as indicated by the activity and stability of the Ni-YZr catalyst. The addition of 4.0 wt% of barium appeared to be the optimal loading, allowing for CH4 conversion of 82%, which remained constant for 7 h of reaction, compared with 72% of barium-unpromoted Ni-YZr at 800 degrees C. TEM images of the spent catalysts revealed the formation of multiwalled carbon nanotubes on all samples. The TGA analysis showed, however, that an increase in baria loading significantly reduced the coke formation amount, indicating the inhibition of coke formation and the enhancement of the catalytic activity. Such improvement in activity and stability was attributed to the incorporation of barium into YZr support, as revealed by XRD analysis, which inhibited the sintering of the catalysts support.