Unlocking the Structure–Property Relationships in Ceria-Modified Ni-Al Catalysts in Partial Oxidation of Methane

Partial oxidation of methane (POM) is a thermodynamically favorable process for hydrogen and syngas production. Cerium oxide (CeO2) was investigated as a textural promoter for nickel (Ni)-based catalysts in POM. In this study, CeO2 was incorporated into Ni/Al2O3 catalysts with varying cerium loadings (1–3 wt.%) to examine its role as a structural and functional promoter. Comprehensive physicochemical characterization using BET, XRD, H2-TPR, and TEM analyses indicated that incorporation of ceria influenced the textural and structural properties, leading to reduced Ni crystallite size from 10 nm to 2.9–3.3 nm, and modified metal-support interactions. The 2 wt.% CeO2-modified Ni/Al2O3 (Ni/2Ce-Al) catalyst demonstrated superior catalytic performance, achieving 70% methane (CH4) conversion and 64% hydrogen (H2) yield at 650 °C with stable performance over 275 min time-on-stream with minimal deactivation. Temperature-programmed reduction studies revealed a non-monotonic trend in reduction behavior with an optimal 2 wt.% cerium loading exhibiting the lowest reduction temperature (865 °C). The H2/CO ratio of 2.92 indicates favorable syngas composition under the conditions studied. Raman spectroscopy showed a decrease in the D/G intensity ratio from 1.55 to 1.33 with increasing cerium loading, indicating enhanced structural ordering and improved coke resistance. The improved catalytic performance may be associated with redox properties of ceria (Ce3+/Ce4+ cycling), its enhanced oxygen storage capacity, and modified Ni-support interactions which can contribute to improved resistance to carbon deposition and Ni sintering. Response surface methodology (RSM) was also successfully used to model the interaction of temperature, space velocity and feed ratio and to confirm the significant positive effect of temperature on conversion. The long-term performance of the optimized catalyst, over a 20 h period, demonstrated the excellent durability of the catalyst, resulting in a stable H2 yield of ca. 87% and CH4 conversion of ca. 90%. This work demonstrates that optimized cerium promotion on alumina-supported Ni catalysts can improve catalytic activity and stability, providing a potentially cost-effective, thermally stable catalyst system for industrial hydrogen and syngas production from (CH4).