Dry Reforming of Model Biogas on a Ni/SiO2 Catalyst: Overall Performance and Mechanisms of Sulfur Poisoning and Regeneration

Carbon-neutral application of renewable biogas to valuable chemical raw materials has received much attention in sustainable areas, while sulfur poisoning remains a big problem in biogas dry reforming process. In this work, sulfur deactivation and regeneration performance of a Ni/SiO2 catalyst in model biogas dry reforming and related mechanisms were studied. The effects of H2S content (50 and 100 ppm) and reaction temperature (700800 degrees C) on biogas dry reforming were investigated. Three regeneration methods (H2S feeding cessation, temperature-programmed calcination (TPC), and O-2 activation) were applied. The results showed that the presence of H2S caused server deactivation in catalytic activity, and higher H2S content led to faster deactivation. The deactivation was not reversed simply by stopping H2S feeding and TPC, but O-2 activation could totally recover deactivated catalysts. The formation of Ni7S6, detected for the first time in biogas conditioning catalytic processes, confirmed by X-ray diffraction and X-ray photoelectron spectroscopy, led to sulfur poisoning, as well as catalyst sintering and carbon deposition. This work revealed that sulfur poisoning and regeneration mechanism is the formation and elimination of Ni7S6, and concluded that oxygen activation was the most effective method for reviving the catalytic activity, preventing sintering, and reducing carbon deposition. These findings will contribute to the industrial application of syngas production from biogas dry reforming.