Effect of rare-earth promoters (Ce, La, Y and Zr) on the catalytic performance of NiO-MgO-SiO2 catalyst in propane dry reforming

In this contribution, NiO-MgO-SiO2 catalysts containing 3 wt. % of CeO2, La2O3, Y2O3, and Zr2O3 were examined for propane dry reforming at 550-750 degrees C. The samples were synthesized by a co-precipitation route, followed by a hydrothermal treatment, and characterized by BET, XRD and TPX analyses. The results indicated that the addition of promoters enhanced the metal-support interaction and basic characteristics, while the acidic nature of the promoted catalyst was changed in a different way. The highest propane conversion of 39.6% was observed over Ce-promoter sample, while the un-promoted catalyst possessed a value of 36.8% at 700 degrees C. Nevertheless, La and Y-promoted catalysts possessed a relatively poor performance, whereby lower CO2 conversion and H-2 yield along with the largest amount of by-products. The yield of H-2 production decreased in the following order of promoters: Zr>Ce>un-promoted>La>Y. The best catalytic performance observed over ceria-promoted catalysts, supported through the sufficient number of active sites, high oxygen mobility, and redox properties (Ce4+/Ce3+) combined with appropriate acidic/ basic characteristics for reactants activation. The largest amount of coke deposition was detected over the Zr-promoted sample while the Ce-promoted catalyst possessed the lowest carbon formation. The influence of ceria loading on the textural and catalytic properties revealed that the higher loadings of ceria (>3 wt. %) resulted in the formation of ceria island which negatively influenced the catalytic activity. Eventually, 3 wt. % ceria loading was suggested as the optimum loading achieving desirable activity, excellent coke formation resistance, and limited byproducts production over NiO-MgO-SiO2 catalyst.