钨、锰对镍-硼/碳纳米管非晶态合金催化剂性能的影响

EFFECTS OF W OR Mn ADDITION ON PROPERTIES OF CARBON NANOTUBES-SUPPORTED Ni-B AMORPHOUS ALLOY CATALYST

采用超声辅助的浸渍-还原法制备了Ni-B/碳纳米管(CNTs)及经W、Mn改性的Ni-B/CNTs非晶态合金催化剂,运用ICP、XPS、TPR、H2-TPD及CO化学吸附法对其进行了表征,研究了催化剂对乙炔选择加氢性能的影响。与Ni-B/CNTs相比,添加质量分数为5%的W和5%的Mn将活性Ni比表面积从改性前的30.6m2/g提高到35.9 m2/g和37.3 m2/g。W的添加基本不影响非晶态合金中Ni的电子状态,Mn则提高了合金中Ni的富电子性。添加W对提高催化剂加氢活性效果不如Mn明显,主要是提高乙烯选择性,但添加Mn更好地促进了催化剂的还原和氢脱附性能,并具有更好的加氢活性。

A series of amorphous Ni-B/CNTs catalysts with different W or Mn concentration were prepared by an impregnation-chemical reduction method with the aid of ultrasonic. Catalysts were characterized by inductively coupled plasma （ICP）, X ray photoelectron spectroscopy （XPS）, temperature programmed reduction （TPR） and temperature programmed desorption of hydrogen （H2-TPD） as well as CO-chemisorption, and studied in the selective hydrogenation of acetylene. Compared to Ni-B/ CNTs, Ni-W-B/CNTs and Ni-Mn-B/CNTs catalysts showed the increase of active nickel surface area, from 30.6 m^2/g to 35.9 m^2/g and 37.3 m^2/g, respectively, due to the dispersing effect of W, Mn on the nickel clusters. XPS results indicated that introduction of 5% W did not appreciably affect the e lectronic state of Ni, but the presence of 5% Mn made Ni more electron-rich in the Ni-B/CNTs amorphous alloy; the addition of W resulted in slight improvement of hydrogenation activity, but higher ethylene selectivity. The addition of Mn promoted the reduction and desorption of H2, and therefore enhanced the hydrogenation activity of Ni-B/CNTs.