Key Takeaways & Executive Findings
- •• • Pt/3CeO2-ZrO2 (Ce/Zr = 3:1) achieved CH4 conversion of 86% and CO2 conversion of 93% at 800 °C, with H2/CO ratio near unity, demonstrating superior activity for dry reforming of methane. • • The catalyst exhibited no detectable carbon deposition after a 10 h stability test at 800 °C, as confirmed by TG and Raman analyses, indicating exceptional coking resistance. • • The optimal Ce/Zr ratio of 3:1 yielded the highest concentration of Ce3+ and Zr3+ species and abundant oxygen vacancies, correlating with strong metal-support interaction and enhanced defect density. • • Platinum on Pt/3CeO2-ZrO2 exists predominantly as single atoms and PtOx clusters, which are thermally stable and highly dispersed, contributing to sintering resistance and sustained catalytic performance.
Abstract
Dry reforming of methane (DRM) converts CH4 and CO2 into syngas with a unity H2/CO ratio, but suffers from catalyst deactivation via sintering and carbon deposition at high temperatures. This study addresses these challenges by employing UiO-66 as a precursor to modify Pt-based catalysts. A series of Pt/CeO2-ZrO2 catalysts were synthesized via incipient wetness impregnation using supports with varying Ce/Zr ratios prepared hydrothermally. Comprehensive characterization—including CO2-TPD, CH4-TPD, XPS, XAFS, in situ DRIFTS, TG, and Raman spectroscopy—revealed a volcano-type correlation between DRM performance and Ce/Zr ratio. Optimal activity and stability were achieved with Pt/3CeO2-ZrO2 (Ce/Zr = 3:1). This catalyst features highly dispersed platinum, primarily as single atoms and thermally stable PtOx clusters. It exhibits the highest concentration of Ce3+ and Zr3+ species, abundant oxygen vacancies, and high defect density, indicating strong metal-support interaction. Mechanistically, stable DRM is facilitated by oxygen-assisted CH4 dissociation and hydrogen-assisted CO2 dissociation. At 800 °C, CH4 and CO2 conversions reached 86% and 93%, respectively, with H2/CO ratio near unity. A 10 h stability test showed no detectable carbon deposition. These results confirm that the catalyst enhances reaction kinetics while demonstrating superior activity, stability, and resistance to coking and sintering.
1. Introduction
Dry reforming of methane (DRM) is a promising route for converting two major greenhouse gases, CH4 and CO2, into valuable syngas with a H2/CO ratio of unity. However, the reaction is highly endothermic and requires operating temperatures above 700 °C, under which conventional catalysts, particularly nickel-based systems, suffer from rapid deactivation due to carbon deposition (coking) and sintering of metal particles. These issues have hindered industrial implementation, as they lead to reduced activity and shortened catalyst lifetime.
This study addresses these bottlenecks by engineering the support material using UiO-66 metal-organic framework as a precursor to obtain CeO2-ZrO2 mixed oxides with tunable Ce/Zr ratios. The hypothesis is that optimizing the Ce/Zr ratio can modulate defect chemistry and metal-support interactions, thereby enhancing the dispersion and stability of platinum active sites. The experimental results demonstrate that a Ce/Zr ratio of 3:1 yields a catalyst with exceptional activity, stability, and resistance to coking and sintering, providing a viable strategy for designing robust DRM catalysts.
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YANG Chen, JIANG Panying, SHEN Dongyang, ZHANG Yuhua, LI Jinlin, LI Lin (2026). Effect of UiO-66 Precursors with Different Ce/Zr Ratios on the Performance of Pt-Based Catalysts in Dry Methane Reforming Reactions. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60669-X
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Frequently Asked Questions
What is the optimal Ce/Zr ratio in the UiO-66 precursor for maximizing DRM performance, and what are the corresponding conversion rates?
The optimal Ce/Zr ratio is 3:1, yielding the Pt/3CeO2-ZrO2 catalyst. At 800 °C, it achieves CH4 conversion of 86% and CO2 conversion of 93%, with a H2/CO ratio near unity.
How does the Pt/3CeO2-ZrO2 catalyst resist carbon deposition and sintering under harsh DRM conditions?
The catalyst exhibits high resistance to coking and sintering due to strong metal-support interactions, abundant oxygen vacancies, and high defect density. Platinum is present as highly dispersed single atoms and PtOx clusters, which are thermally stable. A 10 h stability test at 800 °C showed no detectable carbon deposition, as confirmed by TG and Raman analyses.
What is the mechanistic pathway for the DRM reaction on the Pt/3CeO2-ZrO2 catalyst?
The reaction proceeds via a synergistic cycle involving oxygen-assisted CH4 dissociation and hydrogen-assisted CO2 dissociation. CH4 reacts with oxygen species to form CHxO intermediates, while CO2 is reduced with hydrogen or hydroxyl groups to form formate/carbonate species, ultimately producing CO and H2.
How does the Ce/Zr ratio affect the electronic properties and defect chemistry of the support, and why is this important?
The Ce/Zr ratio modulates the concentration of Ce3+ and Zr3+ species and oxygen vacancies. A ratio of 3:1 yields the highest defect density, which enhances oxygen mobility and metal-support interactions, leading to improved catalytic activity and stability.
What are the implications of this study for industrial scale-up of DRM processes?
The Pt/3CeO2-ZrO2 catalyst demonstrates high activity and stability at 800 °C, with no carbon deposition after 10 h, suggesting potential for long-term operation. However, the use of platinum, a noble metal, may pose cost challenges. Future work should explore strategies to reduce platinum loading or substitute with more abundant metals while maintaining similar performance.
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