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Hydrogen production via biogas reforming and LPG steam reforming over supported Rh and Ru catalysts

Ovakoglou Evangelos

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Summary

Hydrogen (H2) is a highly promising molecule able to be used as an alternative fuel in energy production technologies. Fuel cells are an innovative technology that produce environmentally friendly electricity, through electrochemical reactions, with only by-product H2O, provided that hydrogen does not come from fossil fuels. In this thesis, two different H2 production technologies were studied, ‘’hydrogen production via biogas reforming and LPG steam reforming over supported Rh and Ru catalysts (0.5 wt.%)’’. The main object of the thesis is the preparation, characterization and evaluation of various catalysts in terms of their activity, selectivity and stability for H2 production. For the reaction of dry reforming of methane, the effect of the nature of the support (ZrO2, TiO2, Al2O3, CeO2, YSZ) on the activity of Ru and Rh (0.5 wt.%) catalyst was studied. Moreover, the effect of the addition of 10 wt.% La2O3 on ZrO2 support on the activity of Ru and Rh catalysts (0.5 wt.%) was examined. Α long-term stability test was conducted at 750°C for 30 hours of reaction for 0.5%Rh/ZrO2 and 0.5%Ru/ZrO2 catalysts, which exhibited optimum results. For the reaction of LPG steam reforming the effect of the calcination temperature (400, 600, 800 ° C) of the TiO2 and Al2O3 supports was investigated on the activity of Rh catalyst (0.5 wt.%). In addition, the effect of promotion of TiO2 support with alkali metals Li and K (0.2 wt.%) as well as the effect of the alkali content (0.1 wt.%, 0.2 wt.%, 0.4 wt.%) on the activity of Ru catalysts was examined. According to the results, catalysts supported on ZrO2 exhibits optimum performance and sufficient stability, the catalyst supported on CeO2 exhibits the lowest activity, while those supported on Al2O3 and YSZ exhibit intermediate behavior. The addition of La2O3 on ZrO2 support did not improve Ru and Rh catalytic activity. The results for the propane steam reforming reaction showed that calcination of TiO2 and Al2O3 supports only slightly improves the catalytic performance of Rh. The addition of alkali (Li, K) on Ru/TiO2 catalysts leads to an increase of catalytic activity for the reaction of steam reforming of propane with the highest reaction rate being observed over the Li-promoted (0.2 wt.%) sample.

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