Hydrogen spillover boosts PET upcycling to aviation fuel additives over Co–ReOₓ catalysts

Abstract

Polyethylene terephthalate (PET) upcycling holds potential for producing aviation fuel additives such as benzene, toluene, and xylene (BTX), yet selectively activating C-O bonds over C-C bonds remains a formidable challenge. In this study, we have developed an innovative Co-ReOx catalyst (Co/ReOx-LDO (layered double oxides)) through a hydrothermal impregnation approach. This catalyst facilitates the direct and selective conversion of PET to p-xylene (PX) under mild conditions, achieving yields and productivities as high as 71.7% and 1.1 mmol/g/h, , representing an 3.0 fold improvement compared to the CoAl-LDO catalyst. The Co/ReOx-LDO catalyst demonstrates remarkable recyclability and broad applicability across various esters. Characterization studies reveal that the robust Co-ReOx interaction results in smaller Co particle sizes and higher charge densities, which effectively suppress ring hydrogenation and C-C bond cleavage. Meanwhile, the adjacent ReOx sites promote hydrogen spillover, significantly enhancing the reactivity of Co-ReOx. Spectroscopic analyses indicate that the rate-determining step involves C-O bond cleavage of the ester linkage to form acyl intermediates, and the Co-ReOx accelerates this process with a reduced energy barrier. This research offers valuable insights into catalyst design for efficient fuel additive production from waste polyesters.