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

Abstract

The present research deals with catalyst development for the utilization of CO 2 in dry reforming of methane with the aim of reaching highest yield of the main product synthesis gas (CO, H 2) 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 CH 4 to CO 2 feed ratio of 1. Fresh, spent and regenerated catalysts were characterized by N 2 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: ZrO 2-La 2O 3, La 2O 3 > ZrO 2 > SiO 2 > Al 2O 3 > TiO 2. 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 H 2 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 CO 2 of 78% and CH 4 of 73% were obtained using a 7.5 wt% NiPd (80:20) ZrO 2-La 2O 3 supported catalyst at a reaction temperature of 700 °C. CO and H 2 yields of 57% and 59%, respectively, were obtained.