催化学报 ›› 2025, Vol. 73: 222-233.DOI: 10.1016/S1872-2067(25)64682-1

• 论文 • 上一篇    下一篇

合成气制烯烃双功能催化剂中分子筛拉动效应的微观动力学模拟

胡文德, 柯俊, 王仰东(), 王传明()   

  1. 中石化(上海)石油化工研究院有限公司, 绿色化工与工业催化全国重点实验室, 上海 201208
  • 收稿日期:2025-01-02 接受日期:2025-03-18 出版日期:2025-06-18 发布日期:2025-06-12
  • 通讯作者: *电子信箱: wangyd.sshy@sinopec.com (王仰东), wangcm.sshy@sinopec.com (王传明).
  • 基金资助:
    国家自然科学基金(22402236);国家自然科学基金(22293025);国家自然科学基金(92045303);国家自然科学基金(U22B6011);国家重点研发计划(2024YFA1509901);国家重点研发计划(2022YFA1503503)

First-principles microkinetic simulations revealing the driving effect of zeolite in bifunctional catalysts for the conversion of syngas to olefins

Wende Hu, Jun Ke, Yangdong Wang(), Chuanming Wang()   

  1. State Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Sinopec Shanghai Research Institute of Petrochemical Technology Co., Ltd., Shanghai 201208, China
  • Received:2025-01-02 Accepted:2025-03-18 Online:2025-06-18 Published:2025-06-12
  • Contact: *E-mail: wangyd.sshy@sinopec.com (Y. Wang), wangcm.sshy@sinopec.com (C. Wang).
  • Supported by:
    National Natural Science Foundation of China(22402236);National Natural Science Foundation of China(22293025);National Natural Science Foundation of China(92045303);National Natural Science Foundation of China(U22B6011);National Key Research and Development Program of China(2024YFA1509901);National Key Research and Development Program of China(2022YFA1503503)

摘要:

由氧化物和分子筛组成的双功能催化体系已成为合成气(CO/H2)直接制烯烃(STO)和芳烃(STA)等基本有机原料的关键技术平台. 在STO反应中双功能催化剂通过集成CO活化与C-C偶联反应, 可实现高选择性生成烯烃, 然而其构效关系和动力学影响机制仍不明确, 且氧化物与分子筛之间的协作和匹配对催化性能的影响还缺乏系统认知. 此外, 关键副反应(如水煤气变换(WGS)、烯烃加氢)导致产物分布复杂, 进一步制约了催化性能的提升. 结合第一性原理计算与微观动力学模拟, 本文旨在探究双功能催化体系中分子筛对合成气转化的拉动效应, 强调反应条件与单组分性能协同的重要性.

本文针对双功能(ZnAl2O4/分子筛)催化STO反应, 构建了涵盖甲醇合成与转化、WGS、烯烃加氢等关键过程的全反应网络, 模拟研究了STO催化性能与“反应温度、压力、空速”等反应条件以及分子筛活性之间的关系. 模拟计算结果表明, ZnAl2O4表面极易发生WGS反应, 但对烯烃加氢生成烷烃的活性较低, 这源于氧化物表面H2的异裂活化特性及烯烃分子极性较弱的本质特征. 微动力学模拟表明分子筛组分对CO转化展现出显著的拉动效应: 在673 K等典型STO反应条件下, 当分子筛活性较低(ΔG > 2.1 eV)时, CO转化率仅为~18%, 主要产物为甲醇和二甲醚, 表明分子筛拉动作用弱; 随着分子筛活性提高(ΔG < 1.6 eV), CO转化率可显著增至~40%, 产物以烯烃和CO2为主; 当分子筛总自由活化能在1.6-2.1 eV范围时, 分子筛活性显著影响STO催化性能. 然而, 受甲醇合成热力学平衡的影响, 分子筛的拉动效应对STO的反应温度高度敏感. 微观动力学模拟进一步发现烯/烷比(O/P比)随空速降低或压力升高而下降, 但在典型STO反应条件下仍高于10, 因此可以推测STO反应中烷烃的生成主要源于分子筛内的氢转移而非ZnAl2O4表面的烯烃加氢. 在此基础上, 提出了STO双功能耦合反应“不可能三角”概念, 即在固定压力与氧化物/分子筛活性位点比例下, 不可能同时实现高CO转化率、高烯烃选择性与高反应空速. 若要实现高的烯烃选择性和CO转化率, 可通过采用弱酸性分子筛的同时降低反应空速和/或提高反应压力, 从理论上解释了已有实验结果.

综上, 本文为深入理解双功能催化剂催化STO反应提供了较为完整的动力学图像, 为双功能催化材料各组分的设计优化与工艺条件的调控提供了理论基础.

关键词: 合成气制烯烃, 双功能催化, 微观动力学模拟, 分子筛拉动效应, 不可能三角, ZnAl2O4尖晶石

Abstract:

Direct conversion of syngas to light olefins (STO) on bifunctional catalysts has garnered significant attention, yet a comprehensive understanding of the reaction pathway and reaction kinetics remains elusive. Herein, we theoretically addressed the kinetics of the direct STO reaction on typical ZnAl2O4/zeolite catalysts by establishing a complete reaction network, consisting of methanol synthesis and conversion, water gas shift (WGS) reaction, olefin hydrogenation, and other relevant steps. The WGS reaction occurs very readily on ZnAl2O4 surface whereas which is less active towards alkane formation via olefin hydrogenation, and the latter can be attributed to the characteristics of the H2 heterolytic activation and the weak polarity of olefins. The driving effect of zeolite component towards CO conversion was demonstrated by microkinetic simulations, which is sensitive to reaction conditions like space velocity and reaction temperature. Under a fixed ratio of active sites between oxide and zeolite components, the concept of the “impossible trinity” of high CO conversion, high olefin selectivity, and high space velocity can thus be manifested. This work thus provides a comprehensive kinetic picture on the direct STO conversion, offering valuable insights for the design of each component of bifunctional catalysts and the optimization of reaction conditions.

Key words: Syngas to olefins, Bifunctional catalysis, Microkinetic simulations, Driving effect, Impossible trinity, ZnAl2O4 oxide