Experimental Study of Model Biogas Catalytic Steam Reforming: 2. Impact of Sulfur on the Deactivation and Regeneration of Ni-Based Catalysts

To investigate the effect of sulfur in biogas on steam reforming, the effectiveness and deactivation behavior of Ni-based catalysts in the presence of H2S are experimentally studied. A model biogas, using a constant molar ratio of CH4/CO2 = 1.5, is contacted to supported nickel catalysts in a laboratory-scale fixed-bed reformer. Various partial pressures of H2S, in the range of 15-145 ppm, are introduced to the feed gas, and the catalyst activity is characterized in terms of methane conversion. Tests are carried out at atmospheric pressure in the temperature range of 700-900 degrees C. The results show that the catalyst activity strongly depends upon operating temperature. The effectiveness of the H2S concentration on catalyst deactivation behavior also differs for various operating temperatures, which shows a stronger effect at 800 degrees C compared to 700 or 900 degrees C. To investigate the impact of the type of catalyst, a comparison of two different catalysts is carried out. To study the regenerability of the catalyst, the effects of sudden sulfur removal from the feed gas, temperature increase, and oxidative treatment are studied. On the basis of the results, the activity of the catalyst will be regained rather quickly when H2S is removed from the feed gas at 900 degrees C. For practical operation with Ni-based catalysts and biogas at small scale, temperatures of 900 degrees C seem necessary for the catalytic reforming process.