Design of Ni/La2O3 catalysts for dry reforming of methane: Understanding the impact of synthesis methods

Abstract

Fine-tuning of materials properties, particularly the catalytic properties, through innovative synthesis procedures has gained an increased research interest in the last decades. It is well known that synthesis procedures have considerable impact on the physio-chemical properties of the synthesized materials even if the chemical composition is maintained. Herein, we investigated the impact of selected synthesis methods on the catalytic performance of Ni/La2O3 for the dry reforming of methane (DRM), a challenging reaction known for severe coking. Although this catalyst has been frequently studied for DRM, however, tuning the structure-activity relationship by varying the synthesis routes has not been reported. Herein, the chosen synthesis techniques; for example the solution combustion synthesis (Ni/La-SC), sol-gel (Ni/La-SG), homogeneous precipitation (Ni/La-HP), solvothermal (Ni/La-ST), and modified oleylamine-assisted synthesis (Ni/La-ME); considerably affected the morphology, metal support interaction (MSI), and surface area of Ni/La2O3 catalysts leading to variation in their performance for DRM. The investigated catalysts were thoroughly characterized by using SEM-EDX, TEM, N2-physisorption, XRD, XPS, and H2-TPR to understand the structural properties. Their catalytic performance towards the DRM was evaluated by varying the temperature between 550 and 800 °C. DRM experiments demonstrated that among the studied catalysts, Ni/La-SC showed the best performance for DRM with a high catalytic activity and coking resistance. For instance, Ni/La-SC revealed the highest CO2 and CH4 conversions i.e. 97.9 ± 1.5% and 96.6 ± 1.8%, respectively at 800 °C. The same sample revealed the highest hydrogen yield i.e. 71.9% and the highest H2/CO ratio i.e. 1.03 ± 0.013 at the same temperature. The results revealed that Ni/La-SC demonstrated the lowest increment (20.9%) in the Ni crystallite size after DRM reaction, highest durability, and the lowest rate of coke formation (42 ± 5.2 mg C/gcatalyst) over an operating period of 100 h at 800 °C. The outstanding performance of Ni/La-SC catalyst was credited to the small crystallite size of Ni, high Ni0/Ni2+ ratio, high BET area, and a good dispersion of nickel sites over the La2O3 support. The obtained results may open new frontiers for size and shape-controlled synthesis of nanostructured metals/metal oxides catalysts with controllable morphologies and dispersion that can lead to desirable catalytic properties.