Deciphering the stability mechanism of Pt-Ni/Al2O3 catalysts in syngas production via DRM

Abstract

Deactivation induced by coke deposition remains the foremost challenge in using Ni-based catalysts for the production of syngas via dry reforming of methane (DRM) reaction. Herein, highly dispersed Pt-Ni/Al2O3 bimetallic catalysts prepared by atomic layer deposition (ALD) displayed remarkable stability at 650 ℃ in the DRM reaction. The Pt-Ni catalysts underwent an activation process within the initial 10 h and maintained its activity without deactivation throughout the subsequent aging testing up to 48 h. In contrast, the Ni/Al2O3 rapidly deactivated over time. Despite its high CH4 conversion rates, the Pt-Ni bimetallic catalyst produced a substantial quantity of carbon nanotubes (CNTs) analogous to the Ni/Al2O3 catalyst. The discrepancy in stability performance between two catalysts derived from disparities in the carbon sites and structural defects evolving over reaction time. Regarding the catalysts with Pt decoration on the Ni surface, CNTs exhibited increasing structural defects and gradually deposited on the Al2O3 support without fully encapsulating the metal active sites, as evidenced by CH4-TPD experiments. In the case of Ni nanoparticles on Al2O3, crystalline CNTs with fewer defects accumulated, leading to rapid deactivation. These findings enhance our understanding of coke resistance in DRM catalysts and help the development of more robust bimetallic catalyst systems.