纳米镍粉的制备及其对对硝基苯酚催化加氢的影响

采用改进的化学还原法制备了一系列纳米镍粉催化剂,在对硝基苯酚催化加氢反应中考察了制备条件对纳米镍粉催化活性的影响,并与纳米镍粉的XRD表征结果相关联,期望得到纳米镍粉的最佳制备条件。结果表明,随水合肼用量的增加,纳米镍的催化活性先增加后基本保持不变,适宜的水合肼用量为n(N_2H_4·H_2O):n(Ni~(2+))=1.5;随氢氧化钠用量的增加,纳米镍的催化活性先增加后下降,适宜的氢氧化钠用量为n (NaOH):n(Ni~(2+))=1.5:1;随反应温度的增加,纳米镍的催化活性先增加后下降,适宜的反应温度为76℃;随停留时间的延长,纳米镍的催化活性逐渐下降,适宜的停留时间为2 min。HRTEM表征表明最优条件下制备得到的纳米镍粉粒径较小,约25 nm左右,其对硝基苯酚加氢速率达19.4 mmol/(min·g)。

PREPARATION OF NANO-SIZED NICKEL AND EFFECT OF PREPARING CONDITIONS ON CATALYTIC HYDROGENATION OF p-NITROPHENOL

A series of nano-sized nickel catalysts were prepared by an improved chemical reduction method.The effects of the preparation conditions on the catalytic activity of the nano-sized nickel were examined in the hydrogenation of p-nitrophenol to p-aminophenol.The results showed that the catalytic activity of the nano-sized nickel first increased and then changed slightly with the increase of the amount of N_2H_4·H_2O,with the optimum at n(N_2H4_4·H_2O):n(Ni~(2+))=1.5:1;the catalytic activity first increased and then decreased with the increase of the amount of NaOH,with the opti- mum at n(NaOH):n(Ni~(2+))=1.5:1;the catalytic activity first increased and then decreased with the increase of the reaction temperature,with the optimum at 76℃;the optimum reaction time was 2 min and the catalytic activity decreased gradually with the increase of the reaction time.The particle sizes of the nano-sized nickel prepared under the optimum conditions were about 25 nm and the corre- sponding hydrogenation rate was about 19.4 mmol/(min·g).