Customized Ni-MgO-Al₂O₃catalyst for carbon dioxide reforming of coke oven gas: Optimization of preparation method and co-precipitation pH

Coke oven gas can be upgraded through catalytic reforming using carbon dioxide as a soft oxidant. Herein, a customized Ni-MgO-Al2O3 catalyst for the carbon dioxide reforming of coke oven gas was developed by selecting an appropriate catalyst preparation method and further optimizing the key variable of the selected method. Catalysts were prepared by various methods including co-precipitation, incipient wetness impregnation, hydrothermal, co-impregnation, and sequential impregnation. Among them, the co-precipitated catalyst showed the best performance. As the key variable, the co-precipitated pH of the precursor solution was optimized as 12. The catalysts were characterized using X-ray diffraction, Brunauer-Emmet-Teller method, H2-temperature-programmed reduction, H2-chemisorption, and thermogravimetric analysis. The interaction between a complex NiO species and the support material showed a strong relationship with the number of Ni° active sites, which also has a direct connection with the activity of the catalyst. The developed catalyst successfully lowered the high H2/CO ratio of coke oven gas from 7.00-1.66 through the carbon dioxide reforming reaction. Moreover, the catalytic activity was maintained over 50 h and thermodynamic equilibrium was achieved, even at a high gas hourly space velocity of 600,000 h-1.