Intermetallic synergy between CeOx-Co accelerates the selective production of p-xylene from PET plastic waste over core-shell type cobalt phyllosilicates catalysts

Abstract

The catalytic upcycling of PET waste into value-added aromatics, particularly p-xylene (PX), has attracted considerable research interest. Nevertheless, the rational design of non-precious metal catalysts capable of achieving high PX selectivity while simultaneously ensuring long-term structural and catalytic stability remains a significant challenge. Herein, CeOₓ-modified Co-phyllosilicate (Co-PS) core-shell structured catalysts were synthesized using a single-step approach, yielding a crystalline 2:1 phase of sandwich-like layered phyllosilicate. Controlled Ce incorporation induced structural and electronic modulation, forming a strong CeOₓ–Co interfacial site within a flower-like Co-PS architecture. Among the series, the Ce3.0Co@Co–PS catalyst achieved complete PET conversion with a PX yield of 93.2%. Notably, the catalyst also demonstrated excellent performance for real and mixed PET waste, even with the presence of additives, showcasing a broad substrate scope and practical utility. Comprehensive investigation revealed that the introduction of Ce induces Co0 exsolution from the Co-PS framework, accompanied by lattice distortions and partial delamination of the phyllosilicate structure. Characterization, kinetics, and FT-IR studies revealed that the strong CeOₓ–Co interfacial sites, characterized by enhanced oxygen vacancies and strong acid sites, promoted ester C=O bond activation; meanwhile, hydrogen spillover across the interface facilitated efficient ester bond hydrogenolysis. The comparative assessment revealed that the Ce3.0Co@Co–PS achieved a high PX formation rate (11.3 mmol PX gmetals-1 h-1) with a low environmental impact. This work presents a selective, sustainable catalytic strategy for the efficient upcycling of PET into liquid aromatics.