Mg助剂对Co/Mg/HZSM-5催化剂结构及其催化甲烷部分氧化制合成气性能的影响

采用XRD、TEM、H2-TPR、Raman、XPS和活性评价等方法, 研究了Mg助剂对Co/Mg/HZSM-5催化剂物理化学性质和甲烷部分氧化(POM)制合成气反应性能的影响. 研究发现, 在Co/HZSM-5催化剂中添加Mg助剂, 可有效地提高催化剂的催化活性和稳定性. 在750 ℃和空速1.0×10⁵ mL·h^-1·g^-1反应条件下, Co/Mg/HZSM-5在连续反应30 h的实验时间内催化活性稳定不变, 而Co/HZSM-5因其活性中心Co0转化生成CoAl2O4非活性相, 反应10 h后即迅速失活. 催化剂表征结果表明, 在Co/Mg/HZSM-5催化剂中钴物种除以Co3O4存在外, 一部分钴物种还与Mg助剂发生强相互作用生成较难还原的MgCo2O4, 由此导致还原后钴金属的分散度较高. 关联催化剂表征和活性评价结果, 讨论了催化剂结构与性能之间的关系.

Effect of a Mg Promoter on the Structure and Catalytic Performance of a Co/Mg/HZSM-5 Catalyst for the Partial Oxidation of Methane to Syngas

The effect of a Mg promoter on the physical and chemical properties, as well as catalytic performance of the Co/Mg/HZSM-5 catalyst for the partial oxidation of methane(POM) to syngas was studied by XRD, H2-TPR, TEM, Raman, XPS and activity measurements. The activity and stability of the Co/HZSM-5 catalyst was effectively improved by Mg modification. At T=750 ℃ and SV (space velocity)=1.0×10⁵ mL·h^-1·g^-1 the Mg-modified catalyst exhibited high activity and good stability during a long run. The unmodified catalyst rapidly deactivated after 10 h on stream. Catalyst deactivation was mainly due to the transformation of Co0 into CoAl2O4 as indicated by TPR and XPS. For the Co/Mg/HZSM-5 catalyst the Co species, in addition to ones existing as Co3O4, reacted with the Mg promoter to produce MgCo2O4. This structure, after reduction, led to a higher dispersion of Co metal, compared with the Mg-free catalyst. From the results of the characterization and activity measurements, the relationship between catalyst structure and performance was discussed.