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

The aviation industry, responsible for a significant portion of global carbon emissions, has long sought pathways to decarbonize its fuel supply. Jet fuel derived from fossil resources remains the dominant option, prompting extensive research into sustainable alternatives including biofuels and synthetic hydrocarbons. A particularly intriguing prospect involves converting abundant plastic waste—a growing environmental threat—into high-value jet fuel components. Historically, this conversion has required harsh reaction conditions, notably elevated pressures around 3 MPa and protracted reaction durations extending up to six days, which have limited scalability and economic viability.

Challenging these constraints, the research team designed a remarkable catalyst system based on atomically dispersed ruthenium species anchored on Co-Al oxide substrates. This single-atom catalyst exhibits unprecedented activity for benzene hydrogenation at atmospheric pressure, achieving turnover frequencies of 144 s^−1, which surpass conventional commercial Ru/C catalysts by more than two orders of magnitude. Such catalytic potency at ambient pressure marks a transformative leap toward more sustainable and accessible plastic upcycling technologies.

The tandem catalytic process exploits hydropyrolysis to fragment polymer chains in plastic feedstocks at elevated temperature (460 °C), producing intermediate hydrocarbon vapors enriched in unsaturated species. These vapors then transit downstream to a second stage maintained at a much lower temperature (160 °C), where the Ru_SA@CoAlO_x catalyst performs vapour-phase hydrogenation, saturating the molecules to yield cycloalkanes. This tandem reactor configuration integrates decomposition and hydrogenation seamlessly, optimizing conversion efficiency while maintaining mild operational pressure—ranging from atmospheric to a modest 0.15 MPa.

When tested on pure polystyrene feeds, this tandem catalytic system produced cycloalkane yields reaching an extraordinary 94.8 wt% at 0.15 MPa, and still an impressive 59 wt% even when operated at atmospheric pressure alone. The method’s versatility extends beyond single polymer types; mixtures of common plastic wastes undergo efficient conversion, yielding hydrocarbons within the jet-fuel boiling range at yields exceeding 82 wt%. This remarkable breadth points to broad practical applicability for diverse, heterogeneous plastic streams.

Equally notable is the catalyst’s stability under continuous operation. Over 110 hours of vapour-phase hydrogenation with the Ru_SA@CoAlO_x catalyst revealed sustained activity without significant degradation. This durability is critical for industrial viability, indicating that the catalyst can support sustained processing of plastic waste feedstocks without frequent replacement, reducing downtime and operational costs.

From an environmental perspective, the life-cycle assessment of the entire process underscores its transformative potential. Compared to conventional petroleum-derived jet fuel, the new method delivers an estimated 73% reduction in CO2 emissions over the well-to-pump lifecycle. This dramatic emissions cut arises from both the valorization of existing plastic waste and the energy efficiencies enabled by operating at low pressure and moderate temperatures, marking a meaningful stride toward climate targets in aviation fuel production.

Economic analysis further highlights the promise of this technology. The minimum selling price for jet fuel produced through this route is projected between US$1.0 and US$1.8 per kilogram, placing it in competitive range with fossil-based fuels. This is particularly relevant given fluctuating crude oil prices and growing regulatory pressures incentivizing greener alternatives, creating a favorable scenario for commercialization of this platform.

At the core of this innovation lies the concept of single-atom catalysis, a field gaining increasing traction for its ability to maximize atom efficiency and achieve superior reaction selectivity. By anchoring ruthenium atoms on carefully engineered cobalt-aluminum oxide supports, the research team capitalized on intimate metal-support interactions that stabilize active sites while enhancing hydrogen dissociation—key for high-performance hydrogenation under mild conditions.

The hydropyrolysis step in this tandem process cleverly exploits thermal cracking in a reducing hydrogen environment to generate reactive intermediates that are readily hydrogenated downstream. Operating hydropyrolysis at 460 °C balances conversion efficiency with thermal stability of the catalyst, while the downstream hydrogenation at 160 °C ensures effective saturation of unsaturated domains without undesired side reactions. This finely tuned temperature gradient within a single fixed-bed reactor system exemplifies elegant process engineering.

In contrast with prior high-pressure technologies, this ambient or near-ambient pressure operation not only reduces equipment and safety costs but also minimizes hydrogen consumption. Hydrogen is supplied in conjunction with plastic feedstock, enabling simultaneous polymer breakdown and hydrogenation in a continuous-flow system. This design presents a practical pathway for the integration of hydrogen sourced from renewables, further amplifying sustainability benefits.

Beyond polystyrene, the catalyst efficiently processed mixed plastic waste commonly found in municipal streams, such as polyethylene, polypropylene, and polyvinyl chloride blends. This adaptability is paramount for potential real-world deployment since plastic waste is notoriously heterogeneous. The ability to convert such varied feedstocks into consistent, jet-range hydrocarbons simplifies downstream fuel synthesis and distribution logistics.

The process’s integration compatibility with existing refinery infrastructure represents another advantage. The cycloalkane products can directly blend into conventional jet fuels without extensive upgrading, a factor facilitating regulatory compliance and adoption. Moreover, the high selectivity toward saturated hydrocarbons reduces the need for post-processing steps, contributing to overall process simplicity and cost reduction.

Looking forward, this innovation sets a new paradigm for plastic waste valorization, combining catalyst design, reaction engineering, and environmental consciousness into a single platform capable of addressing pressing challenges of waste accumulation and aviation emissions. The study’s authors articulate the potential for scale-up and industrial adoption, envisioning distributed conversion units near waste collection centers coupled with hydrogen production from renewable sources, creating circular and low-carbon fuel supply chains.

While challenges remain, including catalyst synthesis scalability and integrating hydrogen sourcing sustainably, this research provides a compelling blueprint for advancing beyond fossil-based jet fuel dependency. With plastic pollution and climate change exerting mounting global pressure, such technological breakthroughs exemplify how scientific ingenuity can transform environmental liabilities into valuable resources fueling a more sustainable future.

This work, published in Nature Energy in 2026, stands as a testament to interdisciplinary collaboration spanning materials science, catalysis, chemical engineering, and environmental assessment. Its implications resonate across sectors, promising impactful contributions to climate mitigation, resource conservation, and the emerging circular economy.

The unveiling of a single-atom Ru catalyst capable of ambient-pressure conversion of plastic waste into jet fuel cycloalkanes represents a pivotal step forward. By merging state-of-the-art catalyst innovation with process optimization, the research lays the groundwork for scalable, economically viable, and environmentally responsible aviation fuel solutions derived from problematic plastic waste streams. The path ahead integrates scientific discovery with global sustainability aspirations, illuminating a hopeful direction for tackling two of humanity’s most urgent crises simultaneously.

Subject of Research: Conversion of plastic waste to jet fuel cycloalkanes through tandem hydropyrolysis and vapour-phase hydrogenation enabled by a single-atom ruthenium catalyst.

Article Title: Ambient-pressure conversion of plastic waste to jet fuel cycloalkanes by tandem hydropyrolysis and vapour-phase hydrogenation.

Article References:
Wang, J., Zhang, Z., Wang, S. et al. Ambient-pressure conversion of plastic waste to jet fuel cycloalkanes by tandem hydropyrolysis and vapour-phase hydrogenation. Nat Energy (2026). https://doi.org/10.1038/s41560-026-02078-7

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41560-026-02078-7