Intermetallic synergy between CeOx–Co accelerates the selective production of p-xylene from PET plastic waste over core–shell type cobalt phyllosilicate 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, CeO_x-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 CeO_x–Co interfacial site within a flower-like Co-PS architecture. Among the series, the Ce_3.0Co@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 in the presence of additives, showcasing 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 CeO_x–Co interfacial sites, characterized by enhanced oxygen vacancies and strong acid sites, promoted ester CO bond activation; meanwhile, hydrogen spillover across the interface facilitated efficient ester bond hydrogenolysis. The comparative assessment revealed that Ce_3.0Co@Co-PS achieved a high PX formation rate (11.3 mmol_PX g_metals⁻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.