Effect of calcination conditions on time on-stream performance of Ni/La2O3–ZrO2 in low-temperature dry reforming of methane

A series of catalysts based on Ni supported on mesoporous La2O3–ZrO2 was prepared and tested in low-temperature (400 °C) dry reforming of methane for 100 h on stream. The catalysts were obtained from the same precursor by calcining in either flowing air or Ar at different temperatures. Both the temperature and the atmosphere had an effect on the catalytic activity and on-stream stability. With increasing calcination temperature, the dispersion of Ni decreased. Surprisingly, this resulted not in the lower, but in the higher intrinsic activity of Ni species. This increase can be rationalized by assuming that the rate-determining step is not CH4 decomposition, but the removal of carbon deposits from Ni particle by reaction with CO2. The catalysts calcined at 800 °C in Ar and air showed the strongest and the second strongest deactivation, respectively, caused by the formation of crystalline carbon coatings due to a lower number of CO2 adsorption sites. The size of Ni particles favoring the formation of layered carbon species was found to be the main origin of the catalysts deactivation in the low-temperature dry reforming of methane.