Abstract: The effect of aging pH on the preparation of pseudo-boehmite by stepwise continuous neutralization with NaAlO₂-Al₂(SO₄)₃ method was investigated, the corresponding Ni-Mo-P/Al₂O₃ catalysts were prepared, and the hydrodesulfurization performance was evaluated by using 4,6-dimethyldibenzothiophene (4,6-DMDBT) as the reactant. The results showed that the aging pH had a significant effect on the properties of pseudo-boehmite. The content of sulfate in the product was too high at pH 8.6, and the mass fraction of alumina trihydrate and Na₂O in the product was too high at pH 10.0. The proposed pseudo-boehmite with lower content of impurities could be obtained at the aging pH of 9.0-9.5. The aging pH also affected the growth of different crystalline surfaces, and high aging pH was conducive to increasing the growth rate of (020) crystalline surfaces. The pore volume and specific surface area of Al2O3 support were larger at the aging pH of 9.0 and 9.5, and the most probable pore diameter was about 9.1 nm. The aging pH significantly affected the distribution ratio of different types of hydroxyl groups in the supports, thus, the reduction temperature at the low temperature reduction peaks of the active metals and the proportion of hexa-coordinated 2D polymers were affected. The order of hydrodesulfurization activity of the catalysts was consistent with the order of the low temperature reduction peak temperature of the active metal supported on the carries and the proportion of hexa-coordinated 2D polymers of molybdenum. The preparation of pseudo-boehmite for high activity hydrodesulfurization catalyst support was most favorable when the aging pH was 9.0.

Key words: pseudo-boehmite, aging pH, alumina, pore structure, hydrodesulfurization catalyst