Key Takeaways & Executive Findings
- •• • At 250 °C and WHSV of 30000 mL/(g·h), the Ni/CaO-ZrO2-Al2O3 catalyst achieves 96% CO2 conversion and 100% CH4 selectivity, with a methane space-time yield of 257.5 mmol/(g·h), demonstrating superior low-temperature activity for power-to-gas applications. • • After 200 h aging at 600 °C, the dual-promoted catalyst shows minimal Ni particle growth and activity loss, whereas the Ca-only promoted catalyst suffers pronounced deactivation, highlighting the critical role of Zr in maintaining high-temperature sintering resistance. • • Ca and Zr promoters synergistically enhance Ni dispersion and surface basicity, which are key factors for the high low-temperature activity, as confirmed by physicochemical characterization. • • Zr addition stabilizes Ca species by forming Ca-Zr solid solutions, preventing the transformation of CaO to CaCO3 that would otherwise promote Ni sintering, thus ensuring long-term catalyst stability under industrial conditions.
Abstract
Ni/Al2O3 is regarded as one of the most promising catalysts for industrial CO2 methanation, yet it suffers from inadequate low-temperature activity and thermal sintering. To address these challenges, an Ni/CaO-ZrO2-Al2O3 catalyst with high low-temperature activity and robust high-temperature sintering resistance was developed by introducing Ca and Zr promoters. Under reaction conditions of 250 °C and a space velocity of 30000 mL/(g·h), the catalyst achieved a CO2 conversion of 96% and a methane space-time yield of 257.5 mmol/(g·h). In a 200 h aging test at 600 °C, the Ca-Zr dual-promoted catalyst exhibited a smaller increase in Ni particle size and less activity loss compared to the Ca-promoted counterpart. Characterization revealed that Ca and Zr promoters not only improve Ni dispersion but also enhance surface basicity, contributing to excellent low-temperature activity. Furthermore, Zr suppresses the transformation of Ca species into CaCO3 via solid-phase reaction under operating conditions, thereby inhibiting Ni sintering and ensuring high-temperature stability. This work provides a novel promoter design strategy for developing high-performance Ni-based catalysts for CO2 methanation.
1. Introduction
CO2 methanation is a cornerstone of power-to-gas technology, converting captured CO2 and green hydrogen into methane for storage and transport via existing natural gas infrastructure. However, the reaction is kinetically limited below 300 °C due to the high activation energy for CO2 dissociation, leading to suboptimal conversions on most catalysts. At elevated temperatures, the exothermic nature of the reaction reduces equilibrium conversion, while high pressure can mitigate thermodynamic constraints. Industrially, Ni/Al2O3 catalysts are favored for their cost and activity, yet they suffer from inadequate low-temperature activity and severe sintering of Ni particles under high-temperature operation, causing significant activity loss.
This study addresses these bottlenecks by co-doping Ni/Al2O3 with Ca and Zr promoters. The dual promotion enhances Ni dispersion and surface basicity, boosting low-temperature activity, while Zr stabilizes Ca species against carbonation, preventing Ni sintering. The resulting Ni/CaO-ZrO2-Al2O3 catalyst achieves 96% CO2 conversion at 250 °C and maintains stability after 200 h at 600 °C, offering a practical solution for robust, high-performance CO2 methanation.
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LI Jia, SUI Qingqing, JIANG Yanan, BAI Yang, LIU Yuan (2026). Ni/CaO-ZrO2-Al2O3 Catalyst for CO2 Methanation: Enhanced Low-Temperature Activity and High-Temperature Sintering Resistance. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60639-1
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Frequently Asked Questions
What is the specific role of Zr in preventing Ni sintering during high-temperature CO2 methanation?
Zr forms partial Ca-Zr solid solutions, which stabilize Ca species and prevent their transformation into CaCO3. This suppresses the sintering of Ni particles, as evidenced by the smaller increase in Ni particle size and less activity loss after 200 h aging at 600 °C compared to the Ca-only promoted catalyst.
How does the Ni/CaO-ZrO2-Al2O3 catalyst achieve high low-temperature activity at 250 °C?
The combined introduction of Ca and Zr enhances Ni dispersion and increases surface basicity, which are critical for CO2 adsorption and activation. This results in a CO2 conversion of 96% and a methane space-time yield of 257.5 mmol/(g·h) at 250 °C and a space velocity of 30000 mL/(g·h).
What are the industrial implications of the catalyst's stability under high-temperature aging?
The catalyst retains high performance after 200 h at 600 °C, indicating robust sintering resistance. This is crucial for industrial operations where exothermic reactions can cause localized overheating, leading to catalyst deactivation. The dual-promoted catalyst offers extended lifetime and reduced downtime.
How does the performance of Ni/CaO-ZrO2-Al2O3 compare to conventional Ni/Al2O3 catalysts?
Conventional Ni/Al2O3 suffers from inadequate low-temperature activity and thermal sintering. The dual-promoted catalyst achieves 96% CO2 conversion at 250 °C, which is significantly higher than typical Ni/Al2O3 under similar conditions, and maintains stability after high-temperature aging, addressing both limitations.
What is the significance of the 100% CH4 selectivity reported?
100% CH4 selectivity indicates that the catalyst exclusively produces methane without undesirable byproducts like CO, which is essential for producing pipeline-grade synthetic natural gas. This high selectivity, combined with high conversion, ensures efficient CO2 utilization and product purity.
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