摘要
采用溶胶-凝胶法制备了助剂Cr改性的Ni/MgO催化剂,用化学气相沉积(CVD)法在600℃下裂解甲烷生长碳纳米管,研究了助剂Cr的引入对催化剂微结构和制备碳纳米管性能的影响.催化剂样品用XRD,TPR和CO-TPD进行了分析,制备的碳纳米管用TEM和XRD进行了表征.实验结果表明,NiO和MgO之间存在着强相互作用而形成固溶体,Ni/MgO催化剂经氢气处理后其中的镍氧化物只有极少部分被还原成为镍.助剂铬的引入明显促进了镍的还原,使得催化剂表面的Ni活性中心数增多,从而使催化剂的活性和性能得到了明显的改进.在加入助剂后碳纳米管的产率明显增加,当Cr质量分数为8%时,碳纳米管的产量为未加助剂时产量的5倍,碳纳米管和催化剂的质量比达到19.28.当Cr含量进一步增加时,Ni在催剂表面聚集形成大颗粒,制备出的产品中含有大量的碳纳米纤维和无定形碳.以8%Cr-Ni/MgO催化剂合成的碳纳米管具有比较高的产率且质量较好.
Cr-modified Ni/MgO catalysts for carbon nanotubes （CNTs） synthesis were prepared by sol-gel method and characterized by X-Ray diffraction（XRD）, temperature programmed reduction（TPR） and temperature programmed desorption（CO-TPD）. Carbon nanotubes（CNTs） were synthesized by chemical vapor deposition（CVD） of CH4 at 600 ℃, and characterized using TEM and XRD techniques. The catalytic performances of modified Ni/MgO catalysts for methane decomposition to CNTs were investigated. The results of XRD and TPR show that the addition of Cr to Ni/MgO improve the number of active sites, meanwhile the introduction of Cr reduced the interaction between NiO and MgO, and the reducibility of Ni species is increased remarkably. These factors were responsible for better catalytic performances. It was found that 8% Cr-Ni/MgO catalyst exhibited a CNTs yield of 19.28, which was 5 times higher than that obtained with Ni/MgO catalyst （3.98）. When the Cr loading increased to 15% , the yield of CNTs decreased significantly. The Cr-Ni/MgO catalysts with 6%--8% chromium loading gave the better results.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第2期231-235,共5页
Chemical Journal of Chinese Universities
基金
国家自然科学基金重大专题项目(批准号:20590363)
国家教育部新世纪优秀人才计划(批准号:NCET-05-0783)资助.
关键词
碳纳米管
铬助剂
镍基催化剂
甲烷裂解
Carbon nanotube
Chromium promoter
Cr-Ni/MgO catalyst
Decomposition of methane
