催化学报 ›› 2018, Vol. 39 ›› Issue (12): 1960-1970.DOI: 10.1016/S1872-2067(18)63147-X

• 论文 • 上一篇    下一篇

乙酸甲酯和正己烷在HZSM-5上耦合反应的研究

杨阔a,b, 李金哲a,c, 张潇b, 刘中民a   

  1. a 中国科学院大连化学物理研究所, 洁净能源国家实验室(筹), 甲醇制烯烃国家工程实验室, 辽宁大连 116023;
    b 中国石油大学理学院, 重质油国家重点实验室, 北京 102249;
    c 中国科学院大学, 北京 100049
  • 收稿日期:2018-07-24 修回日期:2018-07-26 出版日期:2018-12-18 发布日期:2018-09-26
  • 通讯作者: 张潇, 刘中民
  • 基金资助:

    国家自然科学基金(21303264,21576256,21273005);中国石油大学(北京)引进人才科研启动基金(YJRC-2013-49);中国石油大学(北京)基础学科研究基金(2462015YQ0601).

Investigation of the coupled reaction of methyl acetate and n-hexane over HZSM-5

Kuo Yanga,b, Jinzhe Lia,c, Xiao Zhangb, Zhongmin Liua   

  1. a National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b College of Science, State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China;
    c University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-07-24 Revised:2018-07-26 Online:2018-12-18 Published:2018-09-26
  • Contact: 10.1016/S1872-2067(18)63147-X
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21303264, 21576256, 21273005), the Science Foundation Research Funds Provided to New Recruitments of China University of Petroleum, Beijing (YJRC-2013-49), the Basic Academic Research Funds of China University of Petroleum, Beijing (2462015YQ0601).

摘要:

蒸汽裂解是石油化工行业生产低碳烯烃和芳烃的一种非常重要的手段.石脑油和一些低碳烷烃在蒸汽裂解中被广泛用作原料.经过长时间的发展和改进,蒸汽裂解技术已经有了长足的进步,但它作为一个强吸热的反应过程,需要非常高的温度才能进行,巨大的能耗是蒸汽裂解技术所要面临的最大问题.虽然催化裂解能够显著降低裂解温度到650℃左右,但若将强吸热的反应和强放热的反应进行耦合,这将是一种全新的解决能源利用率问题的途径.我们将强放热的乙酸甲酯在HZSM-5上的反应和强吸热的正己烷的裂解反应结合,使得热量得到耦合.其次,乙酸甲酯拥有碳氧双键,是一种"缺氢化合物",而正己烷作为一种"富氢"化合物,其元素组成上具有大量的氢元素.两种反应物的共同反应,除了热量耦合效应外,必将具有某种形式的元素耦合效应.
在固定床反应器上考察了不同条件下乙酸甲酯和石脑油模型化合物正己烷在HZSM-5上的反应,发现耦合体系中产物分布的系统性变化是显而易见的.在多数反应条件下,耦合体系中烯烃和C5以上芳烃的选择性升高,而烷烃,H2,CO和CO2的选择性则明显降低,表明元素耦合效应存在于耦合体系中,且契合了"缺氢"的乙酸甲酯能够夺取"富氢"的正己烷中氢元素的特性.
在Si/Al=19的HZSM-5分子筛上,反应温度为300℃时,耦合体系的正己烷初始转化率达到100%,而此时正己烷单独进料体系的初始转化率只有58.9%.我们通过TPSR对两种体系的正己烷变化趋势进行考察,发现乙酸甲酯的加入会显著降低正己烷的初始裂解温度,进而促进正己烷的转化,同时加剧了正己烷的芳构化.
乙酸甲酯非常高的活性导致催化剂的迅速失活,但随着正己烷的加入而得到缓解.通过GC-MS对积碳物种的分析发现,正己烷的加入改变了乙酸甲酯在分子筛上形成的积炭物种前驱体,这也为我们研究耦合体系的反应机理提供了证据.结合低温乙酸甲酯的产物分布和原位红外对三种反应体系的研究,我们提出了一种正己烷和乙酸甲酯耦合体系的反应机理.

关键词: 乙酸甲酯, 正己烷, 耦合反应, HZSM-5

Abstract:

The coupled reaction of methyl acetate and n-hexane was carried out over a HZSM-5 catalyst. In addition to a thermal coupling effect, systematic variations in the product distribution were also observed in the coupled system. The bezene-toluene-xylene (BTX) selectivity was remarkably improved while the H2, CO, and CO2 selectivity decreased. Rapid deactivation of the catalyst was observed, caused by the extremely high reactivity of methyl acetate, which was alleviated after adding n-hexane. These results indicated that a coupling effect exists in this system. A detailed pathway for the coupled system is suggested based on the analysis of the surface species, carbonaceous species deposited on the catalyst, as well as the product selectivity changes. The good match between the "hydrogen deficiency" of methyl acetate and the "hydrogen richness" of n-hexane is consistent with the observed coupling effect.

Key words: Methyl acetate, n-Hexane, Coupled reaction, HZSM-5