Tandem catalyst innovation pathways: A green route to high-value light aromatics from CO2

In the ongoing global transition toward carbon neutrality, converting carbon dioxide (CO₂) into high-value platform chemicals represents a vital strategy for reducing greenhouse gas emissions and decreasing industrial reliance on petroleum. Among these target products, light aromatics—specifically benzene, toluene, and xylenes (collectively known as BTX)—are crucial bulk feedstocks for polymers, resins, and synthetic fibers. However, direct CO₂ hydrogenation via the traditional CO₂-to-methanol pathway has long suffered from poor selectivity toward target BTX molecules, as intermediate species frequently undergo excessive surface methylation to form heavier, less desirable C₉₊ aromatics.

To address this challenge, a research team from the Shanghai Advanced Research Institute, Chinese Academy of Sciences, together with researchers from the University of Chinese Academy of Sciences and Shanxi University, has designed a novel oxide/dual-zeolite tandem catalyst. By integrating a methanol-to-olefins (MTO)-active SAPO-34 zeolite into a ZnZrO_x/ZSM-5 catalytic system via physical powder mixing, the team successfully modulated the concentration and evolution pathway of reaction intermediates. This hybrid system (designated as ZZO/2SP34/Z5) achieves remarkable BTX selectivity at a relatively low reaction temperature of 320 °C, offering a facile, non-petroleum route for sustainable chemical synthesis. The findings were published in ENGINEERING Energy.

Key Highlights and Findings

• Enhanced Reactant Adsorption: The introduction of SAPO-34 (SP34) substantially boosts the adsorption capacity for H₂ and CO₂ across the ZZO/Z5 catalytic system.
• Intermediates Tailoring: Probe experiments and in situ DRIFTS studies confirm that SP34 selectively converts a portion of the generated methanol intermediate into light olefins (C₂⁼–C₄⁼). This lowers the local methanol concentration transferred to ZSM-5 (Z5), effectively suppressing the unwanted surface methylation of BTX into heavy C₉₊ aromatics.
• Superior BTX Selectivity: Under optimized conditions (320 °C, 3 MPa, and 1200 mL/(g_cat·h)), the optimized ZZO/2SP34/Z5 catalyst achieved an overall aromatic selectivity of 75.3% (CO-free) and a CO₂ conversion of 12.4%. Crucially, BTX selectivity reached 42.3% among the aromatic fractions—a 3.3-fold increase compared to the standalone ZZO/2Z5 catalyst (12.9%).
• More Effective Than Acid Passivation: The dual-zeolite relay strategy proved far more effective and accessible than traditional external acid site passivation (e.g., core-shell silicalite-1 coating), which only raised BTX selectivity to 19.9% while increasing diffusion resistance.

A Breakthrough in Low-Temperature Conversion

Direct hydrogenation of CO₂ to aromatics usually involves a trade-off: high overall aromatic yields often come at the expense of BTX selectivity due to secondary alkylation. While earlier efforts attempted to solve this by passivating ZSM-5 acid sites or introducing Fischer-Tropsch synthesis (FTS) components, these methods often degraded total aromatic selectivity or required complex synthesis steps.

The tandem dual-zeolite strategy cleanly bypasses these issues. In this dynamic system, the ZnZrO_x oxide converts CO₂ into oxygenated intermediates and methanol. SAPO-34 selectively redirects part of the methanol into C₂⁼–C₄⁼ olefins, and ZSM-5 processes both the remaining oxygenates and light olefins into BTX via oligomerization, cyclization, and dehydrogenation. Achieving over 40% BTX selectivity among total aromatics at a mild temperature of 320 °C represents a performance benchmark rarely reported in existing literature.

This work provides crucial mechanistic insights into intermediate regulation during CO₂ hydrogenation and serves as a practical foundation for designing next-generation multifunctional tandem catalysts.

About the Research

Journal: ENGINEERING Energy

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Cite this article: Liu, J., Sun, S., Pan, M., Fang, D., Zhou, T., Bu, X., Yang, C., & Gao, P. (2026). Modulating reaction pathways for the highly selective production of light aromatics from CO₂ hydrogenation. ENGINEERING Energy, 20(5), 10750. https://doi.org/10.1007/s11708-026-1075-2