Effect of Si/Zr ratio on the catalytic behavior of Pt-Cu/Zr-SBA-15 in continuous methane dry reforming

Abstract

Mesostructured SBA-15 supports with varying zirconium contents were synthesized through a single-step hydrothermal route by systematically adjusting the Si/Zr molar ratio. These Zr-incorporated mesoporous materials were subsequently employed as hosts for a bimetallic catalytic system, in which 5 wt% copper served as the primary active phase while platinum (0.5 wt%) acted as a promoter. The active metals were introduced using the incipient wetness impregnation technique, employing copper nitrate and chloroplatinic acid as precursors. The structural and surface characteristics of the synthesized supports and catalysts were systematically explored using powder XRD, BET analysis, NH₃-TPD, TPR, HR-SEM, HR-TEM, and TGA. Catalytic activity was assessed in the dry reforming of methane under atmospheric pressure. Reactions were conducted with equimolar CH₄ and CO₂ feeds (1 : 1 ratio) operated under a GHSV of 36 000 mL g⁻¹ h⁻¹, between 400 and 800 °C. Structural analyses verified the efficient embedding of Zr atoms within the silica structure. Particularly, samples with Si to Zr ratios of 5 and 10 exhibited enhanced surface acidity while avoiding the crystallization of ZrO₂ (anatase phase). Among the tested formulations, the Pt-Cu/Zr-SBA-15 catalyst possessing a Si to Zr ratio of 5 displayed the most promising performance. It achieved CH₄ and CO₂ conversion levels of 90% and 95%, respectively, with a favorable H₂/CO ratio of 3.8 after six hours of continuous operation. The catalyst also demonstrated excellent resistance to sintering and minimized coke accumulation, highlighting its long-term stability. Post-reaction analyses confirmed negligible carbon deposition on the Zr-modified catalysts. The superior DRM performance was attributed to several synergistic factors: strong electronic and structural interactions between copper and platinum, fine dispersion of the active metal species, reinforced metal-support bonding, and an optimal balance between weak and strong surface acid sites was observed for the catalyst.