低温耐硫甲烷化催化剂硫化过程

Sulfidation effect on low temperature sulfur-resistant methanation catalyst

采用燃烧法制备MoO_3/ZrO_2催化剂,该催化剂由于具有比表面积大、粒径小的优点,表现出很高的低温耐硫甲烷化活性。通过考察硫化工艺条件的影响发现,硫化过程中硫化时间、硫化压力、硫化氢浓度的影响不大,而硫化温度的影响较明显,300℃下恒温硫化效果最佳,表征结果表明,300℃下恒温硫化可以使催化剂完全硫化,得到较多的Mo S2晶格条纹,有利于提高催化剂的甲烷化活性。恒温硫化时,硫化温度低于300℃时,催化剂硫化不完全,形成的Mo S2晶格条纹较少;硫化温度过高会导致催化剂过度硫化并发生团聚,从而导致催化剂的耐硫甲烷化活性降低。分步硫化时目标温度为400℃时效果最佳,且与300℃恒温硫化的效果接近,对于MoO_3/ZrO_2催化剂,可选择300℃恒温硫化,适宜的硫化条件为:硫化压力0.1 MPa,硫化温度300℃,硫化氢浓度3%H_2S/H_2,硫化时间4 h。

MoO3/ZrO2 catalyst, which prepared by solution combustion method, achieved the highest CO methanation activity due to its high surface area and effective MoO3 dispersion on ZrO2 support. By study of sulfidation process on methanantion activity, it was found that sulfidation pressure, time and H2S concentration had little effect but sulfidation temperature had signifcant effect. For one-step constant temperature sulfidation process, the optimum sulfidation temperature was 300℃. Catalyst characterization showed that isothermal sulfidation at 300℃ produced catalyst with complete sulfidation and many MoS2 crystalline, which is helpful to improve methanation activity. Isothermal sulfidation below 300℃ yielded catalyst with incomplete sulfidation and fewer amounts of MoS2 crystalline while isothermal sulfidation above 300℃ resulted aggregation of MoS2 crystalline, which will deteriorate MoOa/ZrO2 catalyst. For stepwise sulfidation process, the optimum sulfdation temperature was 400℃, which resulted catalyst with nearly same methanation activity as that of one-step isothermal sulfidation at 300℃. Therefore, the suitable sulfidation condition for MoO3/ZrO2 catalyst is determined as 0.1 MPa, isothermal 300℃, 3% HES/H2, and time 4 h.