制备条件对Ni/Al_2O_3催化剂催化乙醇水蒸气重整制氢性能的影响

分别采用均匀沉淀法、沉淀法和浸渍法制备了Ni/Al_2O_3催化剂,在常压固定床反应器中评价了Ni/Al_2O_3催化剂在乙醇水蒸气重整制氢反应中的性能;采用X射线衍射和低温N_2物理吸附法对Al_2O_3载体和Ni/Al_2O_3催化剂进行了表征;考察了载体焙烧温度及时间、催化剂制备方法、Ni负载量和催化剂还原时间等制备条件对Ni/Al_2O_3催化剂性能的影响。实验结果表明,以600℃下焙烧2 h的Al_2O_3为载体、采用浸渍法负载质量分数10.0%的Ni、在500℃焙烧1 h且在650℃下还原1 h的Ni/Al_2O_3催化剂的活性和选择性最好。在500℃、重时空速9 6 h~(-1)、水与乙醇的摩尔比为3:1的反应条件下,乙醇转化率达100%,产气速率为83.0 mL/min,H_2选择性为63.6%。

Influence of Preparation Conditions of Ni/Al_2O_3 Catalyst on Its Activity in ydrogen Production by Ethanol Steam Reforming

Ni/Al_2O_3 catalysts were prepared separately by homogeneous precipitation, precipitation and impregnation. Hydrogen production from steam reforming of ethanol over Ni/Al_2O_3 catalyst was studied in a fixed bed reactor. The structures and surface characteristics of Al_2O_3 support and Ni/Al_2O_3 catalyst were determined by means of XRD and N_2 physical adsorption. Influences of calcination temperature and time of support, Ni loading,preparation method and reduction conditions of Ni/Al_2O_3 on catalyst activity were investigated. The preferable preparation conditions were as follows:Al_2O_3 support was calcined at 600 ℃ for 2 h, Ni/Al_2O_3 catalyst with Ni loading of 10.0%(mass fraction, based on Al_2O_3 support) was prepared by impregnation and calcination at 500 ℃ for 1 h, and then reduced by H_2 at 650 ℃ for 1 h. Under the conditions: reaction temperature 500 ℃, mole ratio of water to ethanol 3:1 and WHSV 9.6 h~(-1), selectivity to H_2 was 63.6%, output of gas was 83.0 mL/min and ethanol conversed completely.