Unveiling structural evolution and performance of hybrid-functional catalyst in plastic pyrolysis–catalytic gasification process

Conventional metal-loaded zeolite catalysts often suffer from deactivation due to coking and sintering. To address this, hybrid-functional Ni-CaO-Ca 2 SiO 4 catalyst was prepared and evaluated for H 2 -rich syngas production by pyrolysis–catalytic gasification process, achieving maximum H 2 yield of 113.21 mmol g −1 of plastic . The catalyst deactivation behavior, along with the structural evolution and surface chemistry of the hybrid-functional catalyst, was investigated by means of both ex situ and in situ characterization techniques . After cycles, Ni oxidation at the surface of particle, slight Ni sintering, a decrease in Ni/NiO ratio, and surface enrichment of O–C=O species were observed. Although metallic Ni was detected by PXRD (Powder X-ray diffraction) in the bulk, surface X-ray photoelectron spectroscopy (XPS) revealed the absence of metallic Ni and the predominance of NiO on the catalyst surface, suggesting surface-initiated deactivation and pore blockage. In situ PXRD results confirmed the reduction of NiO by pyrolysis products. These findings elucidate the fundamental behavior of the catalyst under realistic conditions and provide practical insights for designing durable and efficient catalysts for waste valorization. These dynamic observations distinguish this work from studies based mainly on post-reaction characterization and provide mechanistic insight into catalyst activation, deactivation, and structural evolution. The integrated ex situ / in situ approach offers a useful framework for designing durable catalysts for plastic-waste valorisation.