Key Takeaways & Executive Findings
- •• • Alkali modification with 10% NaOH for 2 h increased the specific surface area and alkaline site density of 15%Ni/Al2O3 monolithic catalysts, leading to enhanced catalytic activity and CH4 selectivity. • • Under H2/CO = 3:1, space velocity 10000 mL/(g·h), and 400 °C, the 15%Ni/Al2O3-2h catalyst achieved 97% CO conversion and 100% CH4 selectivity, outperforming unmodified catalysts. • • Stability tests over 2 h showed that the 15%Ni/Al2O3-2h catalyst maintained a CO conversion of approximately 98%, demonstrating excellent long-term stability for industrial methanation processes. • • The use of cordierite as a monolithic support provides a structured catalyst with improved heat and mass transfer, addressing a key bottleneck in conventional packed-bed reactors for exothermic methanation reactions.
Abstract
The methanation of biomass gasification syngas (H2/CO = 3:1) was investigated over Ni/Al2O3 monolithic catalysts supported on cordierite, with a nominal Ni loading of 15 wt%. Catalysts were modified by treatment with 10% NaOH solution for 1 h and 2 h. Physicochemical properties were characterized by BET, TEM, H2-TPR, XRD, CO2-TPD, and TG. Results showed that the 2 h modification (15%Ni/Al2O3-2h) increased specific surface area, enhanced catalytic activity, and increased alkaline site density compared to the unmodified catalyst. Under optimized conditions (H2/CO volume ratio 3:1, space velocity 10000 mL/(g·h), temperature 400 °C), the 15%Ni/Al2O3-2h catalyst achieved a CO conversion of 97% and CH4 selectivity of 100%. Stability tests over 2 h showed that the CO conversion remained stable at approximately 98%, indicating excellent catalytic stability. The study demonstrates that alkali modification with 10% NaOH for 2 h significantly improves both the methanation performance and stability of Ni/Al2O3 monolithic catalysts, offering a promising route for synthetic natural gas production from biomass.
1. Introduction
Biomass gasification coupled with catalytic methanation offers a viable route to substitute fossil natural gas, yet commercial catalysts often suffer from insufficient activity and stability under industrial conditions. Conventional Ni/Al2O3 catalysts, while active, exhibit limited CH4 selectivity and deactivate due to carbon deposition and sintering. Alkali promotion has been proposed to modify catalyst surface basicity and pore structure, but systematic studies on monolithic supports are scarce.
This work addresses these limitations by employing a cordierite monolithic support coated with Ni/Al2O3, modified via NaOH treatment. The 2 h alkali modification enhances the catalyst's structural properties and alkaline site density, leading to superior methanation performance. The study provides quantitative evidence that alkali-modified monolithic catalysts achieve near-complete CO conversion and perfect CH4 selectivity, offering a scalable solution for biomass-to-methane technologies.
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XING Wanli, YANG Bingjie, ZHANG Wanli, KAI Xingping, ZHOU Quan, YANG Tianhua (2026). Methanation Performance of Biomass Gasification Syngas over Alkali-Modified Ni/Al2O3 Monolithic Catalysts. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(25)60607-4
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Frequently Asked Questions
What is the optimal NaOH modification time for maximizing CO conversion and CH4 selectivity?
The 2 h modification (15%Ni/Al2O3-2h) yielded the best performance, achieving 97% CO conversion and 100% CH4 selectivity at 400 °C, H2/CO = 3:1, and space velocity 10000 mL/(g·h). In contrast, 1 h modification showed inferior performance, indicating that 2 h is required to sufficiently enhance catalyst properties.
How does alkali modification affect the catalyst's structural properties and stability?
Alkali modification with 10% NaOH for 2 h increased the specific surface area and alkaline site density of the Ni/Al2O3 catalyst, as confirmed by BET and CO2-TPD. This enhanced basicity promotes CO adsorption and methanation, while the improved structural integrity contributes to stable CO conversion (~98%) over 2 h, indicating reduced deactivation.
What are the key operating conditions for achieving high methanation performance?
Optimal conditions are H2/CO volume ratio of 3:1, space velocity of 10000 mL/(g·h), and reaction temperature of 400 °C. Under these conditions, the 15%Ni/Al2O3-2h catalyst achieved 97% CO conversion and 100% CH4 selectivity, demonstrating the importance of stoichiometric H2/CO ratio and moderate temperature to balance thermodynamics and kinetics.
How does the monolithic catalyst compare to conventional pellet catalysts in terms of industrial scalability?
The cordierite monolithic support offers lower pressure drop and improved heat transfer compared to packed-bed pellets, which is critical for exothermic methanation reactions. The study demonstrates that the monolithic catalyst maintains high activity and stability, making it a promising candidate for scalable fixed-bed or structured reactors in biomass-to-SNG plants.
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