Diesel pre-reforming over highly dispersed nano-sized Ni catalysts supported on MgO–Al2O3 mixed oxides

•A highly dispersed 50 wt.%Ni/MgO–Al2O3 catalyst for diesel pre-reforming.•Deposition–precipitation method is applied for catalyst preparation.•Catalytic activity and coke resistance is affected by pH of precursor solution.•The optimum pH is 11.5 for high metal dispersion and small NiO crystallite size.

A highly dispersed 50 wt% Ni/MgO–Al2O3 catalyst was prepared by deposition–precipitation (DP) method for the diesel pre-reforming reaction. The pH of the precursor solution was controlled from pH 9.5 to 12.0 to examine the effects on NiO crystallite size and metal dispersion. The increase of pH of the precursor solution causes an increase of specific surface area and metal dispersion, and reduces NiO crystallite size. The pre-reforming reaction was carried out using n-tetradecane as surrogate compound of diesel. The coke formation of used catalysts was examined by TGA, TEM, SEM, and Raman analysis. The 50 wt% Ni/MgO–Al2O3 catalyst prepared at pH 11.5 showed a high catalytic activity and excellent coke resistance due to high metal dispersion (8.71%), small NiO crystallite size (3.5 nm), and strong interaction between Ni and support. Furthermore, this catalyst showed a good stability in the pre-reforming reaction at S/C ratio of 3.5 and 450 °C for 88 h.