Rhodium-Enhanced Reducibility and Coke Resistance in Low-Loading Ni and Co/Al2O3 Catalysts for CO2 Methanation
Year: 2026
Type: article
Abstract: Low-loading Ni (2.9 wt%) and Co (2.8 wt%) catalysts supported on γ-Al 2 O 3 were promoted with small amounts of Rh (0.8–1.9 wt%) and evaluated for CO 2 methanation under high space velocity (60,000 mL g cat −1 h − 1 ). A monometallic Rh/Al 2 O 3 catalyst was used as a reference. Rhodium significantly enhances the reducibility of Ni 2+ and Co 3+ /Co 2+ species, lowering reduction temperatures to ~ 240°C (Ni) and below 570°C (Co), achieving near-complete reduction (~ 100%) for both bimetallic systems. Despite lower dispersion in the bimetallic catalysts (~ 14–15%) compared to RhAlO (~ 55%), competitive catalytic performance is achieved at elevated temperatures. CO 2 -TPD reveals only weak basic sites for all catalysts, and the significantly lower CO 2 uptake observed for NiRhAlO does not compromise activity, suggesting that the metallic phase primarily governs CO 2 activation. Catalytic tests show that while RhAlO is more active at low temperatures (28% conversion at 250°C), NiRhAlO and CoRhAlO reach comparable conversions (> 80%) at 450°C, with CH 4 selectivity above 90% up to 350°C. All catalysts exhibit high stability over 30 h at 450°C, with no clear evidence of sintering or carbon deposition, as confirmed by XRD, TGA, and Raman analyses. These results suggest that Rh promotion enables low-loading Ni and Co catalysts to achieve high activity, enhanced reducibility, and high stability under demanding methanation conditions, offering a cost-effective alternative to high-loading or noble-metal-based systems.
Source: Catalysis Letters
Institution: Universidade Federal do Rio de Janeiro
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,990
OpenAlex ID: W7165943722