Influence of rare earth promoters on the performance of Ni/Mg(Al)O catalysts for hydrogenation and steam reforming of toluene

CeO2-, La2O3-, and ZrO2-promoted Ni/Mg(Al)O catalysts synthesized by hydrotalcite-type precursors have been investigated with respect to catalytic activity and carbon formation in the hydrogenation and steam reforming of toluene as a model tar compound. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) specific surface area and H-2-temperature programmed reduction (TPR) were used to observe the characteristics of the prepared catalysts. The carbon formation and its amount on the used catalysts were examined by transmission electron microscope (TEM), scanning electron microscope (SEM) and thermogravimetric (TG). The trend of catalytic activity as derived from the experimental results followed the order: Ni-Ce>Ni-La>Ni-Zr>Ni. The catalyst modified with CeO2 exhibited the highest catalytic performance and had good carbon resistance in the hydrogenation and steam reforming of toluene. A toluene conversion of 96.8%, a CH4 yield of 45.2% and a CO yield of 50.4% have been achieved. The addition of promoters led to better dispersion of nickel species and higher interaction nickel-support, which were favorable for increasing the catalytic activity and effectively preventing carbon formation.