煤热解与Ni/La2O3-ZrO2上低碳烃干重整耦合过程焦油生成特性

Tar formation characteristic of integrated process of coal pyrolysis with dry reforming of low carbon alkane over Ni/La2O3-ZrO2

  • 摘要: 低碳烷烃干重整(DRA)耦合煤热解(CP)过程可以有效提高热解焦油产率。使用Ni/La2O3-ZrO2作为DRA催化剂,当La/Zr比为4∶1时,催化剂能够有效抑制DRA反应过程中积炭的生成,同时能够进一步提高重整耦合煤热解(CP -DRA)过程的焦油产率。本工作分析了CP-DRA的焦油组成和官能团分布,并与氮气中煤热解(CP-N2)的焦油进行了对比,以了解DRA对煤热解的影响,并利用同位素示踪方法,讨论了低碳烃在CP-DRA中的作用。结果表明,CP-N2得到的焦油中含有较多Hal、Cal和CH+CH2的脂肪族化合物,而CP-DRA焦油含有较多Car、Har、Hα及CH3,并且比CP-N2焦油的平均分子量更低,焦油组分更轻。在CP-DRA中加入少量乙烷会提高CP-DRA焦油中的Hβ和CH+CH2的含量。电子顺磁共振分析表明,CP-DRA的焦油具有较高的自由基浓度,而相应的半焦具有较低的自由基浓度。同位素示踪实验表明,DRA提供·H、·CH3等自由基稳定煤热解自由基,在CP-DRA过程中生成更多的烷基芳香族化合物。

     

    Abstract: Coal pyrolysis integrated with dry reforming of low-carbon alkane (CP-DRA) is an effective way to improve tar yield. Ni/La2O3-ZrO2 with a La/Zr ratio of 4 was a good catalyst for DRA to inhibit carbon deposition and obtain high tar yield in CP-DRA. In this study, the fraction distribution and component of tars from CP-DRA and coal pyrolysis in N2 atmosphere (CP-N2) were characterized by using several methods to understand the effect of DRA on coal pyrolysis. The isotope trace method was also used to discuss the role of low-carbon alkane in CP-DRA. The results showed that the tar from CP-N2 is mainly composed of aliphatic compounds with more Cal, Hal and CH+CH2, and the tar from CP-DRA contains more Car, Har, and CH3, and has lower weight-average molecular weight and more light tar content than CP-N2. A small amount of C2H6 addition in CP-DRA will raise the ratio of Hβ and CH+CH2. Electron paramagnetic resonance (EPR) analysis shows that the tar from CP-DRA has a higher radical concentration while the corresponding char has a lower radical concentration. The isotope trace experiment showed that alkanes provide ·H, ·CH3, etc. to stabilize the radicals from coal pyrolysis and result in more alkyl aromatic compounds during CP-DRA.

     

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