Özet:
The overall purpose of this research study is to design and develop effective non-noble catalysts having high and stable activity with suitable H2/CO product selectivity for the production of synthesis gas via CO2 reforming of methane (CDRM). In this context, bimetallic Co-La/ZrO2, and trimetallic Co-Ni-La/ZrO2 and Co-Ni-Ce/ZrO2 catalysts were prepared, characterized and tested for their CDRM performance. The freshly reduced and spent samples were characterized by SEM-EDX. The reaction temperature, feed composition, space velocity, reaction time and nickel loading were the parameters used in activity and selectivity tests. In the catalysts, Co and promoter, i.e. La and Ce, loadings were kept fixed as 5 wt.% and 2 wt.%, respectively, while two Ni loading levels, 3 wt.% and 5 wt.%, was used in trimetallic samples. The results have shown that Co-La catalyst exhibited high stability, but only has moderate activity in CDRM. The introduction of nickel led to an increase in the activity which may be related with high dehydrogenation activity of Ni and strong and extensive Co-Ni surface interaction. The results show that Co:Ni loading ratio in the trimetallic catalyst has a significant effect on CDRM performance for the La promoted samples. There was no significant change in terms of activity and stability occur Co-Ni-Ce/ZrO2 system in response change in Ni:Co ratio. Characterization of the catalysts indicated uniform distribution of metal on both Ce and La promoted trimetallic catalysts. The type of carbon deposited on trimetallic catalysts was all filamentous. It was also clearly observed that Ce-promoted catalyst have less carbon deposition than La-promoted one, remarking the effect of ceria on the stable activity of the catalysts through CeOx redox cycle regulating surface oxygen transfer. On the basis of the performance test results, it was concluded that increasing temperature increased CH4 and CO2 conversions and H2/CO product ratio. The results have shown that when the CH4:CO2 feed ratio is greater than 1.0, the lowest methane conversion, the highest carbon dioxide conversion and H2/CO product ratio were observed for all catalysts. It was found out that increasing space velocity decreased the conversion values and H2/CO product ratio.
