Bimetallic carbides as catalysts for dry reforming and steam reforming

In this work, a series of novel bimetallic carbide catalysts has been successfully prepared in house, by changing the metallic elements therein and the ratio of CO2/CO in carburization process. Co-W-C and Ni-W-C are the elements in the bimetallic carbides to be discussed in this dissertation. Following the preparation, different techniques were applied to characterize the catalyst from the bulk phase to the surface.;For Co-W-C, the catalytic evaluation were carried out for three reactions, methane dry reforming (DRM), methane steam reforming (SRM) and methanol steam reforming (SRMeOH). This bimetallic carbide is stable and active for DRM after proper pretreatment, while less so for SRM and SRMeOH. Afterwards, the effect of temperature history on the catalytic properties was investigated for DRM of Co-W-C. The effect is significant, and the reactivity can be improved a lot after being exposed to methane at 850°C.;For Ni-W-C, the catalytic properties were evaluated only for DRM. This Ni-W-C also has high reactivity and good stability for DRM, with very low coke formation. Similar to the work for Co-W-C, the effect of temperature history was also studied. No obvious difference has been found in the catalytic performance before and after exposure to methane at 850°C.;For both Co-W-C and Ni-W-C, the fresh and spent catalysts (both before and after exposure to high temperature) have been collected for characterization, including XRD, TPR, SEM, EDAX and NEXAFS. Consistent characterization measurement results were obtained. To exhibit reasonable reactivity, those catalysts transform into the stable and active phases, a mixture material of Co (or Ni), WC and C. For Co-W-C, before it is exposed to 850°C, the presence of some form of oxide (CoWO4) makes the catalyst ineffective for DRM. However, once the stable and active phases are formed by exposure to methane at 850°C, they can be maintained even though the catalyst is brought back to a low temperature. In the application of Co-W-C in steam reforming, the presence of water could prevent necessary carbon laydown to transform the catalyst into final active phases, by decreasing the reactivity of the catalyst.;Keywords. catalyst, carbide, reforming, methane