水热处理时间对氧化铝载体及加氢脱硫催化剂性能的影响

Effect of Hydrothermal Treatment Duration on the Performance of Alumina Support and Catalytic Activity in Hydrodesulfurization

采用低温N2吸附-脱附、XRD、IR、TG-DTA和Mo平衡吸附等方法,详细考察了90℃下,水热处理时间对高温焙烧氧化铝载体性质的影响;并以4,6-DMDBT为模型化合物,评价了水热处理时间对以氧化铝为载体的Ni-Mo-P催化剂加氢脱硫活性的影响。结果表明:水热处理时间较短时,氧化铝载体的物相不变、孔体积缓慢增大、比表面积迅速增加、孔径降低但降幅较小,基本保持了高温焙烧氧化铝的大孔特性,同时水合作用生成大量表面-OH,使载体吸附活性金属Mo的能力迅速提高,酸性-OH增加、碱性-OH减少,加氢脱硫催化剂活性显著提高;水热处理时间较长时,水合作用生成拟薄水铝石微小晶体,改变了载体物相、孔体积增大,对载体表面性质、催化剂活性改善不明显。水热处理使载体表面可以吸附活性金属的-OH数量增加是催化剂活性提高的主要原因。

The effects of hydrothermal treatment duration on the properties of calcined alumina support were studied by means of low temperature N2 adsorption-desorption,XRD,IR,TG-DTA and Mo equilibrium adsorption.The hydrodesulfurization activity of Ni-Mo-P catalyst with the same metal content was evaluated by using 4,6-DMDBT as model compound.Results show when the hydrothermal treatment duration is short,the phase of alumina carrier confirmed by XRD remains unchanged,and the pore volume,the specific surface area and pore diameter become slightly increased,rapidly increased,and decreased,respectively.These supports almost maintain the large porous characteristics of calcined alumina at high temperature.A large number of surface hydroxyl(-OH)groups are formed by hydration,which significantly increases the adsorption of active metal Mo and acidic-OH groups,but reduces basic-OH groups,hence the catalytic activity is remarkably improved.As the hydrothermal treatment time is subsequently lengthened,the pseudo-boehmite microcrystal is formed by hydration,with the increase of pore volume.But the surface properties of the carrier and the activity of the catalyst do not improve obviously.The increase of-OH groups,which can adsorb active metals on the surface of the support by hydrothermal treatment,is in favor of the increase of catalyst activity.