催化学报 ›› 2024, Vol. 64: 133-142.DOI: 10.1016/S1872-2067(24)60097-5

• 论文 • 上一篇    下一篇

Y/Beta催化剂上丙酮制异丁烯反应的失活机理

王畅a, 颜婷婷b,*(), 戴卫理a,*()   

  1. a南开大学材料科学与工程学院, 天津 300350
    b中国民航大学理学院, 天津 300300
  • 收稿日期:2024-05-30 接受日期:2024-07-09 出版日期:2024-09-18 发布日期:2024-09-19
  • 通讯作者: * 电子邮箱: weilidai@nankai.edu.cn (戴卫理),ttyan@cauc.edu.cn (颜婷婷).
  • 基金资助:
    国家自然科学基金(22272083);国家自然科学基金(22302228)

Deactivation mechanism of acetone to isobutene conversion over Y/Beta catalyst

Chang Wanga, Tingting Yanb,*(), Weili Daia,*()   

  1. aSchool of Materials Science and Engineering, Nankai University, Tianjin 300350, China
    bCollege of Science, Civil Aviation University of China, Tianjin 300300, China
  • Received:2024-05-30 Accepted:2024-07-09 Online:2024-09-18 Published:2024-09-19
  • Contact: * E-mail: weilidai@nankai.edu.cn (W. Dai),ttyan@cauc.edu.cn (T. Yan).
  • Supported by:
    National Natural Science Foundation of China(22272083);National Natural Science Foundation of China(22302228)

摘要:

异丁烯作为一种常用的有机化工原料, 具有重要的工业价值. 与传统的化石路线制异丁烯相比, 生物基丙酮制异丁烯引起了研究者的广泛关注. Brønsted酸催化剂常用作丙酮制异丁烯反应的催化剂, 但反应过程产生的积碳会导致催化剂快速失活. 与常用的Brønsted酸催化剂相比, Lewis酸催化剂具有更好的催化性能和更高的异丁烯选择性, 近年来得到了研究者的广泛关注. 然而, 催化剂的失活仍不可避免, 并且失活机理仍有待阐明.

本文以具有Lewis酸的Y/Beta分子筛为丙酮转化制异丁烯反应的催化剂, 发现该催化剂表现出较好的催化性能, 然而随着反应时间的延长, 其失活仍不可避免, 并且反应温度对催化剂失活影响较大. 采用程序升温表面反应(TPSR)、色质联用(GC-MS)、原位紫外-可见光(UV-vis)光谱和13C交叉极化魔角旋转核磁共振(CP MAS NMR)波谱等多种表征技术详细研究了Y/Beta催化剂上丙酮制异丁烯的催化反应过程. 首先, 通过TPSR监测了反应过程反应物、产物以及中间体的动态变化, 并通过原位UV-vis光谱辅以验证. 其次, 利用13C CP MAS NMR以及GC-MS得到了反应过程重要有机中间物种的具体结构信息. 基于以上谱学手段, 实现了反应过程有机中间物种的动态监测, 得到了失活物种生成和演变过程的谱学证据, 并绘制了Lewis酸Y/Beta催化剂上丙酮转化制异丁烯的反应机制和失活路线. 在低温反应条件下, 丙酮在具有Lewis酸性的Y活性位点上的连续缩合和环化是主要的副反应, 并且在反应过程会产生较多的佛尔酮等失活物种. 高温则可导致环状不饱和醛/酮以及芳烃物种的快速形成和累积, 比如2, 4-二甲基苯甲醛等, 该物种可较强地吸附在Y活性位点上, 并最终导致催化剂失活. 然而, 该积碳物种经过简单的煅烧便可去除, 催化剂的活性也可以很好地恢复. 因此, 通过优化反应温度以及催化剂活性位点的分布, 有望提高丙酮制异丁烯反应的催化活性, 同时延长催化剂的寿命.

综上, 本文通过系列谱学手段相结合的方式, 实现了Lewis酸分子筛上丙酮制异丁烯反应过程有机中间物种动态变化的监测, 阐明了丙酮制异丁烯的反应和失活机理, 为Lewis酸催化的丙酮制异丁烯反应高效催化剂的优化和设计提供了新思路.

关键词: 失活机理, 丙酮制异丁烯, 路易斯酸位点, Y/Beta, 光谱

Abstract:

The conversion of acetone derived from biomass to isobutene has attracted extensive attentions. In comparison with Brønsted acidic catalyst, Lewis acidic catalyst could exhibit a better catalytic performance with a higher isobutene selectivity. However, the catalyst stability remains a key problem for the long-running acetone conversion and the reasons for catalyst deactivation are poorly understood up to now. Herein, the deactivation mechanism of Lewis acidic Y/Beta catalyst during the acetone to isobutene conversion was investigated by various characterization techniques, including acetone-temperature-programmed surface reaction, gas chromatography-mass spectrometry, in situ ultraviolet-visible, and 13C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy. A successive aldol condensation and cyclization were observed as the main side-reactions during the acetone conversion at Lewis acidic Y sites. In comparison with the low reaction temperature, a rapid formation and accumulation of the larger cyclic unsaturated aldehydes/ketones and aromatics could be observed, and which could strongly adsorb on the Lewis acidic sites, and thus cause the catalyst deactivation eventually. After a simple calcination, the coke deposits could be easily removed and the catalytic activity could be well restored.

Key words: Deactivation mechanism, Acetone to isobutene, Lewis acid sites, Y/Beta, Spectroscopy