The SiO2 supported bimetallic Ni–Ru particles: A good sulfur-tolerant catalyst for methanation reaction

• Addition of H2S enhances the sintering and oxidation of Ni0 particle in the methanation reaction.
• Effect of Ru on the sulfur tolerance of the supported Ni catalyst depends on its geometric factor.
• Adsorption of S can only be reduced when S binds with Ni and Ru atoms simultaneously.
• S can bind with Ni and Ru atoms simultaneously on the small bimetallic Ni–Ru particles.
• NiRu/SiO2 catalyst with small bimetallic Ni–Ru particles has enhanced sulfur tolerance.

The long-term stabilities and the sulfur tolerances of SiO2 supported Ni and NiRu catalysts in the methanation reaction were examined. The presence of H2S molecules (10 ppm (v/v)) in the syngas led to fast deactivation of Ni/SiO2 catalyst, because the adsorption of S blocked the active sites as well as accelerated the sintering and the oxidation of Ni0 particles. The effect of Ru on the reduction of S adsorption over the supported Ni-based catalyst depended on its geometric instead of electronic factor. The S adsorption could only be weakened when S bound with both Ni and Ru atoms simultaneously. The formation of such state was more favorable on the polyethylene glycol (PEG)-additive method derived NiRu/SiO2 catalyst with small bimetallic Ni–Ru particles. As a result, this catalyst could stabilize for ∼127 h in H2S-containing methanation reaction, which was ∼1.6–5.8-fold longer than those of PEG-free method derived NiRu/SiO2 catalyst (∼79 h) with separated Ru and Ni/SiO2 catalyst (∼22 h).