拟薄水铝石老化pH对氧化铝载体及加氢催化剂脱硫性能的影响

EFFECT OF pH IN PSEUDO-BOEHMITE AGING ON THE ALUMINA SUPPORT AND HYDRODESULFURIZATION PERFORMANCE OF HYDROGENATION CATALYST

研究了NaAlO_(2)-Al_(2)(SO_(4))_(3)法分步连续中和制备拟薄水铝石工艺中老化pH的影响,并制备了相应的NiMoP Al 2O 3催化剂,使用4,6-二甲基二苯并噻吩作为反应物对催化剂进行加氢脱硫性能评价。结果表明:老化pH对拟薄水铝石性质影响显著,老化pH为8.6时产品中硫酸根含量过高,老化pH为10.0时产品中三水氧化铝杂晶和Na 2O杂质含量过高,老化pH为9.0~9.5时可以得到杂质含量较低的拟薄水铝石;老化pH还影响不同晶面的生长速率,老化pH高有利于提高(020)晶面的生长速率;老化pH为9.0和9.5时载体的孔体积和比表面积较大,最可几孔径为9.1 nm;老化pH显著影响载体表面不同类型羟基的比例,从而影响不同载体负载的活性金属的低温还原峰温度和六配位二维钼多聚物所占比例。催化剂的加氢脱硫活性与载体上负载的活性金属的低温还原峰温度和六配位二维钼多聚物所占比例顺序一致。当拟薄水铝石老化pH为9.0时,最有利于制备高活性加氢脱硫催化剂载体。

The effect of aging pH on the preparation of pseudo-boehmite by stepwise continuous neutralization with NaAlO_(2)-Al_(2)(SO_(4))_(3) method was investigated,the corresponding Ni-Mo-P Al_(2)O_(3) 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 Na_(2)O 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 Al_(2)O_(3) 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.