临CO_2气氛下钼基催化剂耐硫甲烷化性能研究

在反应温度550℃、空速5 000 h~(-1)和1.2%H_2S浓度下,考察了反应气中添加CO_2对负载型Mo基催化剂甲烷化活性的影响。结果表明,添加CO_2会促进逆水煤气变换反应,从而降低Mo O_3/Al2O_3催化剂的耐硫甲烷化活性。与Mo O_3/Al2O_3催化剂相比,添加CO_2对铈铝复合载体负载的Co-Mo双组分催化剂的影响较小。通过表征发现,添加CO_2引起催化剂活性下降的主要原因是由于其增强了逆水煤气变换反应过程,使甲烷化过程可用氢气量减小。另外,逆水煤气变换反应生成的水会影响催化剂表面结构和组成。在连续加入10%CO_220 h后停止加入CO_2,催化剂的耐硫甲烷化活性可以得到恢复,因此,认为CO_2加入量低于10%时,对催化剂及甲烷化反应的影响是可逆的;但CO_2加入量大于10%后由于生成的水量增大会破坏催化剂的结构并减少活性位,从而造成催化剂的不可逆失活。

Effect of CO2 in syngas on methanation performance of Mo-based catalyst

The methanation of synthesis gas is the key process of coal to natural gas. Considering the existence of CO₂ in the synthesis gas, it is important to investigate the influence of CO₂ on the sulfur-resistant methanation. In this paper, the effect of CO₂ on methanation activity of Mo-based catalysts was investigated at the reaction temperature of 550℃ and the gas space velocity of 5000h^-1 with the syngas containing 1.2% H₂S(volume ratio). The results show that the promoter Co and the cerium-aluminum composite support can improve the stability of the catalyst and reduce the deactivation. The CO₂ is proved to promote the reverse water gas shift reaction, which would inhibit the activity of MoO₃/Al₂O₃ catalyst more heavily than MoO₃-CoO/CeO₂-Al₂O₃ catalyst. When the CO₂ adding to the inlet gas is less than 10% for 20h, the catalyst activity could be restored to its original activity after stopping the addition of CO₂. However, as the added CO₂ in inlet gas is over 10%, more H₂O will be generated through reverse water gas shift reaction to damage the catalyst structure and decrease the active component, resulting in an irreversible loss of catalyst activity.