Customized Ni–MgO–Al2O3 catalyst for carbon dioxide reforming of coke oven gas: Optimization of preparation method and co-precipitation pH

•A Ni–MgO–Al2O3 catalyst was customized for CO2 reforming of coke oven gas.•Co-precipitation was selected as the optimum catalyst preparation method.•The co-precipitated pH was optimized as 12.0.•Complex NiO species–support interactions were key for catalytic activity.•The optimized catalyst lowered the H2/CO ratio of coke oven gas from 7.00–1.66.