In a landmark advancement in sustainable chemistry, researchers from Sichuan University and Peking University have developed an innovative catalytic system that transforms waste polyethylene (PE) and carbon dioxide (CO₂) into valuable liquid aromatics and carbon monoxide (CO), under ambient pressure conditions. This breakthrough presents a technically feasible and environmentally friendly approach to valorizing two problematic carbon-rich waste streams simultaneously, addressing critical issues of plastic pollution and greenhouse gas mitigation. Published in the journal Engineering, the study unveils a tandem catalytic process that departs from conventional methods requiring high pressures and complex reaction setups.
Polyethylene, a dominant constituent of plastic waste globally, has long posed challenges in chemical recycling due to its inertness and tendency to produce complex, hard-to-separate mixtures upon degradation. Meanwhile, CO₂ utilization often depends on external hydrogen supplies to drive hydrogenation reactions, complicating both economics and scalability. The novel catalyst system designed by the researchers circumvents these limitations by integrating a bifunctional oxide-zeolite catalyst pairing: CuFeO₂ and Ga-[Ga]/ZSM-5. This sophisticated catalyst architecture enables a one-step conversion at 400 °C while maintaining atmospheric pressure, a significant leap forward in operational practicality.
At the heart of this process is a finely tuned catalytic synergy. The Ga-[Ga]/ZSM-5 component features cationic gallium species that interact with the zeolite’s Brønsted acid sites, thereby facilitating the dehydrogenation of polyethylene chains while suppressing undesired hydrogen transfer reactions. This results in significant in situ hydrogen generation, which is then consumed by CuFeO₂ catalyzing the reverse water-gas shift (RWGS) reaction. In this manner, hydrogen acts as a shuttle to balance and propel the reaction, pushing the system towards the formation of aromatic hydrocarbons, particularly benzene, toluene, and xylene (BTX), which are highly valuable chemical intermediates.
The reaction’s selectivity and yields surpass those of earlier methods. Under optimized conditions, the catalyst system yields 99% selectivity toward liquid-phase aromatic compounds and 91.9% selectivity toward C₁–C₂ aliphatic hydrocarbons in the gaseous products. The total aromatic yield reaches an unprecedented 75.3 wt%, of which BTX comprises 81.1%. Furthermore, the CO₂ conversion efficiency is quantified at 10.9 mmol per gram of polyethylene, highlighting a significant degree of co-utilization of the greenhouse gas within the process. Notably, isotope labeling experiments confirm that CO₂ exclusively participates in the RWGS reaction, indicating no direct incorporation into aromatic molecular frameworks and reinforcing mechanistic understanding.
This catalytic innovation also showcases commendable stability and recyclability. Repeated regeneration cycles through calcination preserve the catalyst’s activity, underscoring its robustness for long-term industrial applications. The system’s versatility extends to real-world plastic feedstocks as well, with positive results demonstrated for high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), and even heterogeneous mixed plastic waste containing typical impurities. Such adaptability positions this technology as a potential solution for tackling diverse plastic waste streams without extensive pretreatment.
Advancing design ingenuity, the process was implemented in a cascade reactor configuration. This design refinement further optimizes product distribution by almost completely eliminating heavier C₃–C₄ alkane impurities and enhancing the purity of the aromatic product slate. The practical implication is a streamlined downstream separation and purification process, reducing operational complexity and costs. The integration of polyethylene upcycling with CO₂ valorization through tandem catalysis propels the concept of circular carbon economy into a tangible realm, with petrochemical intermediates and syngas precursors produced simultaneously from waste.
Beyond the fundamental chemistry, this breakthrough bears immense significance for global sustainability goals. Addressing plastic waste accumulation and greenhouse gas emissions concurrently aligns with the urgent need for environmentally sound chemical manufacturing pathways. By harnessing atmospheric pressure reaction conditions and accessible catalyst materials, the technology promises scalability and environmental compatibility. If adopted at scale, this method could disrupt current paradigms in plastic recycling and CO₂ utilization, ushering in a new era where waste is transformed into wealth with reduced carbon footprints.
In summary, the collaboration between Sichuan University and Peking University researchers has yielded a pioneering catalytic process that converts polyethylene waste and CO₂ into highly pure aromatics and carbon monoxide under mild conditions. The process leverages carefully engineered bifunctional catalysts, operational synergy between dehydrogenation and RWGS reactions, and reactor design innovations to deliver superior selectivity, yield, and stability. This research not only pushes the frontiers of chemical recycling but also paves the way for industrial practices that integrate multiple waste valorization pathways efficiently.
The study, titled “Upcycling Polyethylene into Separable Aromatics Through Tandem Catalysis with CO₂ at Atmospheric Pressure,” represents a milestone in green chemical engineering. Its open-access publication in Engineering serves as a resource for further advancement by the broader scientific community and industrial stakeholders. As plastic waste and carbon emissions continue to challenge planetary health, such cutting-edge research underscores the pivotal role of interdisciplinary innovation in shaping sustainable futures.
Future work will likely focus on scaling the process, optimizing catalyst longevity under industrial conditions, and integrating this methodology into existing petrochemical infrastructure. Additionally, exploration of catalytic analogs and reactors could further improve efficiency and broaden the array of convertible feedstocks, enhancing the system’s applicability. Given the demonstrated conversion of mixed plastic wastes, the technology could synergize with municipal recycling programs and carbon management strategies globally.
This innovative route not only adds value to waste materials but also creates high-purity products compatible with existing chemical supply chains, reducing the need for virgin fossil feedstocks. By strategically coupling plastic upcycling with CO₂ utilization, this research exemplifies the circular economy’s principles of resource efficiency, environmental stewardship, and economic viability. Its implications ripple across environmental science, catalysis, chemical engineering, and materials science, making it a profoundly viral breakthrough in sustainable technology development.
Subject of Research: Chemical upcycling of polyethylene and utilization of carbon dioxide via tandem catalysis for producing aromatic hydrocarbons.
Article Title: Upcycling Polyethylene into Separable Aromatics Through Tandem Catalysis with CO₂ at Atmospheric Pressure
News Publication Date: April 4, 2026
Web References:
Article DOI: https://doi.org/10.1016/j.eng.2025.12.006
Journal Website: https://www.sciencedirect.com/journal/engineering
Image Credits: Wenjun Chen, Mingyu Chu et al.
Keywords
Plastic upcycling, polyethylene recycling, carbon dioxide utilization, tandem catalysis, bifunctional catalysts, reverse water-gas shift reaction, aromatic hydrocarbons, sustainable chemistry, waste valorization, chemical engineering, green catalysis, circular carbon economy
Tags: ambient pressure catalytic processbifunctional oxide-zeolite catalystCO2 conversion to aromaticsCO2 utilization without hydrogenCuFeO2 catalyst for CO2Ga-ZSM-5 catalyst in catalysisgreenhouse gas mitigation technologiesliquid aromatic production from wastepolyethylene chemical recyclingscalable plastic and CO2 conversionsustainable plastic waste valorizationtandem catalysis for plastic recycling
