Development of Ni-Pd bimetallic catalysts for the utilization of carbon dioxide and methane by dry reforming

摘要

The present research deals with catalyst development for the utilization of CO2 in dry reforming of methane with the aim of reaching highest yield of the main product synthesis gas (CO, H2) at lowest possible temperatures. Therefore, Ni-Pd bimetallic supported catalysts were prepared by simple impregnation method using various carriers. The catalytic performance of the catalysts was investigated at 500, 600 and 700 °C under atmospheric pressure and a CH4 to CO2 feed ratio of 1. Fresh, spent and regenerated catalysts were characterized by N2 adsorption for BET surface area determination, XRD, ICP, XPS and TEM. The catalytic activity of the studied Ni-Pd catalysts depends strongly on the support used and decreases in the following ranking: ZrO2-La2O3, La2O3 > ZrO2 > SiO2 > A12O3 > TiO2. The bimetallic catalysts were more active than catalysts containing Ni or Pd alone. A Ni to Pd ratio = 4 at a metal loading of 7.5 wt% revealed the best results. Higher loading lead to increased formation of coke; partly in shape of carbon nanotubes (CNT) as identified by TEM. Furthermore, the effect of different calcination temperatures was studied; 600 °C was found to be most favorable. No effect on the catalytic activity was observed if a fresh catalyst was pre-reduced in H2 prior to use or spent samples were regenerated by air treatment. Ni and Pd metal species are the active components under reaction conditions. Best conversions of CO2 of 78% and CH4 of 73% were obtained using a 7.5 wt% NiPd (80:20) ZrO2-La2O3 supported catalyst at a reaction temperature of 700 °C. CO and H2 yields of 57% and 59%, respectively, were obtained.