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    热催化CO2加氢制芳烃研究进展

    Advances in thermal catalytic hydrogenation of CO2 to aromatics

    • 摘要: 利用可再生能源产生的“绿氢”将二氧化碳(CO2)转化为高附加值芳烃为实现碳减排与资源循环利用提供了一条绿色可持续的技术路径。芳烃作为重要的基础化学品,广泛应用于聚合物、燃料添加剂、医药中间体等领域。然而,CO2分子具有高度热力学稳定性和化学惰性,其高效活化及定向转化面临着巨大的挑战。当前,热催化CO2加氢制芳烃主要包含甲醇中间体和改性费托合成两条反应路线。二者均采用双功能催化剂,其通常由金属氧化物(或碳化铁)以及分子筛耦合而成。甲醇中间体路线中,CO2首先加氢转化为甲醇或其衍生物,再在分子筛酸中心上进一步芳构化;该路线表现出优异的芳烃选择性,但CO2转化率较低。改性费托合成路线则通过逆水煤气变换(RWGS)反应将CO2转化为CO,再经费托合成步骤生成烯烃中间体,最终在分子筛上芳构化生成芳烃。该路线可实现较高的CO2转化率,但产物分布宽、芳烃选择性较低,且易发生过度加氢生成烷烃。如何协同提升CO2转化率、芳烃选择性和催化剂的稳定性是该领域的难点与挑战。本文主要聚焦于热催化CO2加氢制芳烃,系统综述了近年来该领域的研究进展。基于上述两种主流反应体系,首先探讨了催化剂设计与调控策略,涵盖复合氧化物构建、碳化铁基催化剂助剂引入、载体优化与制备方法创新以及分子筛酸性、孔道结构与形貌的调控,旨在增强活性位点协同、促进中间体传递与转化。其次,阐述了串联催化、烃池机理及氢转移机制,探讨了通过中间体定向强化与协同催化优化反应路径的策略,从而提升目标产物选择性。同时,分析了金属氧化物烧结与迁移、碳化铁相变、分子筛积碳等失活行为,为进一步开发长效运行催化剂提供理论依据。最后,总结与展望了CO2加氢制芳烃面临的机遇与挑战,提出聚焦催化剂精准设计、多尺度研究反应机理、过程集成与系统优化以及创新反应路径是研究的重点,从而为未来该领域的发展提供前瞻的研究方向与战略性参考。

       

      Abstract: Renewable energy sources are receiving increasing attention in order to meet the energy needs of social development and mitigate the effects of greenhouse gases. Advances in hydrogen production technology from renewable energy sources have enabled the sustainable conversion of CO2 into high-value aromatic hydrocarbons via hydrogenation, offering a promising a pathway for CO2 emission and carbon recycling. Aromatics, as essential basic chemicals, are widely used in polymers, fuel additives, pharmaceutical intermediates, and other industries. However, due to its high thermodynamic stability and chemical inertness, the efficient activation and directional conversion of CO2 molecules remain a significant challenge. CO2 hydrogenation to aromatics primarily proceeds via two pathways: methanol intermediate route and modified Fischer-Tropsch synthesis route. Both routes rely on bifunctional catalysts, typically composed of metal oxides (or iron carbides) coupled with zeolites. The methanol-intermediate route first converts CO2 into methanol or its derivatives through hydrogenation, followed by further aromatization on the acidic sites of the zeolite. This route exhibits high aromatics selectivity but suffers from limited CO2 conversion The modified Fischer-Tropsch synthesis route, on the other hand, converts CO2 into CO via the reverse water-gas shift (RWGS) reaction, followed by the Fischer-Tropsch step to produce olefin intermediates, which are finally aromatized on the zeolite to generate aromatic hydrocarbons. This route achieves higher CO2 conversion activity but exhibits a broad product distribution, lower aromatics selectivity, and a tendency for excessive hydrogenation to produce alkanes. How to synergistically improve high CO2 conversion, high aromatic selectivity and long-term catalyst stability remains a pivotal issue in this field. This article focuses on thermal catalytic CO2 hydrogenation to aromatic hydrocarbons, systematically reviewing recent research progress in this area. Based on the two mainstream reaction systems mentioned above, the catalyst design and regulation strategies are first examined. These include the construction of composite oxides, the introduction of promoters in iron carbide-based catalysts, carrier optimization and innovative preparation methods, as well as modulation acidity, pore structure, and morphology of zeolites. These approaches aim to enhance the synergy among active sites and promote the transfer and transformation of reaction intermediates. Subsequently, the tandem catalysis, the hydrocarbon pool mechanism, hydrogen transfer mechanisms are elaborated upon. Strategies for optimizing reaction pathways through the directed enhancement of intermediates and synergistic catalysis to improve target product selectivity are also discussed, with the goal of improving selectivity toward target products. In parallel, catalyst deactivation behaviors are analyzed, including sintering and migration of metal oxides, phase transformation of iron carbides, and coke deposition on zeolites, providing a theoretical foundation for the development of long-term stable catalyst. Finally, opportunities and challenges are outlined, emphasizing that precise catalyst design, multi-scale investigation of reaction mechanisms, process integration and system optimization, and innovative reaction pathways are key research priorities. This review aims to offer forward-looking research directions and strategic references for the future development of this field.

       

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