多级孔ZSM-5分子筛对低阶煤流化床快速热解产物分布的影响

Effect of hierarchical ZSM-5 zeolites on product distribution of low rank coal fast pyrolysis in a fluidized bed

  • 摘要: 采用晶种诱导法和碱处理法制备了不同介-微孔复合结构的多级孔ZSM-5分子筛,利用XRD、TEM、NH3-TPD、氮气物理吸附等手段对其结构性质进行了表征,并考察了其对低阶煤流化床快速热解产物分布的影响。结果表明,碱处理后不同程度上增加了分子筛催化剂的比表面积、介孔孔容和平均孔径。多级孔ZSM-5分子筛促进了热解挥发分中脂肪烃的裂解环化和酚池的解离,提高了焦油中轻质芳烃的收率。在碱浓度为0.3 mol/L时轻质芳烃收率达到最大,其中,单环芳烃和萘/甲基萘较微孔分子筛分别增加了2.7倍和0.9倍。在碱浓度达到0.4 mol/L时,由于过度脱硅造成表面塌陷,分子筛催化剂性能下降。

     

    Abstract: A series of hierarchical ZSM-5 zeolites was prepared by seed induction method and alkali-treated method, and their crystal structural, textural and acidic properties were characterized by XRD, TEM, NH3-TPD, and N2-sorption. The effect of hierarchical ZSM-5 zeolites on product distribution of low rank coal fast pyrolysis in fluidized bed was investigated. The results showed that the specific surface area, mesoporous pore volume and average pore size of the zeolites were increased to different degree after alkali treatment. Hierarchical ZSM-5 zeolites promoted the cyclization of aliphatics and the dissociation of phenol pool of volatile from coal pyrolysis, and increased the content of light aromatics. The yield of light aromatics reached the maximum at 0.3 mol NaOH. The content of mono-aromatics and naphthalene/methylnaphthalene increased by 2.7 times and 0.9 times respectively compared with microporous zeolites. The catalysts performance decreased at 0.4 mol NaOH due to excessive desilication.

     

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