Tailored Ruthenium Catalyst Converts Waste PET Directly into Benzene

    Controlled acidity and oxygen vacancies steer consecutive decarboxylation reactions, enabling high-yield benzene production from real-world PET waste.

    A research team from Zhejiang University and the Chinese Academy of Sciences has reported a catalytic route that converts waste polyethylene terephthalate directly into benzene. Published in the Journal of the American Chemical Society on October 21, the work demonstrates a form of molecular “skeletal editing” in which the eight-carbon aromatic unit derived from PET is contracted into a six-carbon benzene ring.

    PET is commonly broken down into terephthalic acid or related compounds before further processing. Converting that aromatic intermediate into benzene is difficult because two carboxyl groups must be removed consecutively while the aromatic ring remains intact. Competing hydrogenolysis reactions can divert the reaction pathway and reduce benzene selectivity.

    The researchers addressed this problem with a ruthenium catalyst supported on tungsten-modified zirconia, denoted Ru/W₀.₄ZrOₓ. The optimized material achieved an 83.3% benzene yield from waste PET.

    Moderate incorporation of tungsten oxide reconstructed the acid sites of the zirconia support, increasing its Brønsted acidity. At the same time, oxygen vacancies and tungsten species promoted the adsorption and activation of carboxyl groups.

    Working together with ruthenium nanoparticles, these features stabilized reaction intermediates that favor carbon–carbon bond cleavage through decarboxylation. The researchers also controlled the hydrogen supply and employed a dodecane–water solvent system to suppress unwanted hydrogenolysis and direct both carboxyl-removal steps toward benzene formation.

    The catalyst was evaluated using several real-world PET wastes rather than only a purified model compound. Preliminary techno-economic and life-cycle analyses produced favorable results under the assumptions adopted in the study, although the authors’ process-level assessments will still require validation at pilot scale.

    Benzene is a major platform chemical used to produce polymers, resins and numerous chemical intermediates. Recovering it from PET waste could conserve aromatic carbon and provide an alternative to exclusively fossil-derived feedstocks.

    Practical implementation will depend on several factors, including safe closed-system handling of benzene, hydrogen and solvent requirements, catalyst regeneration, tolerance to additives and contaminants, and performance in larger reactors. These considerations are particularly important because benzene is toxic and must be contained throughout production, purification and transport.

    Beyond PET recycling, the study establishes a broader catalyst-design principle: coordinated control of acidity, oxygen vacancies and metal sites can direct consecutive decarboxylation reactions while preserving an aromatic framework.

    Research source: Yue Zhu, Zhouying Mao, Buxing Han and Qingqing Mei, “Selective Consecutive Decarboxylation Enables Skeletal Contraction of Waste PET,” Journal of the American Chemical Society 148 (2026), 44380–44396. DOI: 10.1021/jacs.6c11537; PubMed record.