【作者】 居艳；

【导师】 李凤仪；

【作者基本信息】 南昌大学 ， 工业催化， 2005， 博士

【摘要】 在共沉淀法制备的3种镍基催化剂上裂解甲烷制备了碳纳米管，研究结果表明：催化剂的性质对碳纳米管的产率，结构，形貌和物性有重要影响。应用XRD，TEM，BET和TG等表征手段对碳纳米管进行了表征。在Ni-Cu-Al催化体系中加入少量碳酸钠会降低碳纳米管的产率，使竹节状碳纳米管转变成大内径碳纳米管。体系中的碳酸钠对控制碳纳米管的形貌起了重要作用。利用化学气相沉积技术在多孔氧化铝模板上制备了取向碳纳米管阵列。通过控制阳极氧化电压可以调节膜板的孔径，进而可以控制碳管的直径。 以次磷酸为还原剂，有机胺为pH值调节剂，用诱导——化学还原法制备了非晶态NiP／CNTs催化剂。以苯加氢为探针反应，研究了碳纳米管的不同处理方法以及催化剂的制备条件对非晶态NiP／CNTs催化活性的影响。用XRD，TEM，ICP，TPR，XPS，H₂-TPD和DTA等方法对催化剂进行了表征。讨论了载体——碳纳米管和稀土对非晶态NiP／CNTs催化剂活性和热稳定性的影响。实验结果表明：硝酸氧化和KOH活化均能促进碳纳米管负载非晶态NiP的催化活性。催化剂的制备条件对非晶态NiP／CNTs催化剂活性有一定影响。NiP在载体上具有非晶态结构。合金负载后粒径明显变小，分散度和比表面积有很大提高。非晶态NiP／CNTs催化剂中磷以及碳纳米管都能向镍给出电子，使镍表面富电子状态。富电子状态的镍更易被还原，氢在其上的吸附强度降低。非晶态NiP／CNTs催化剂的苯加氢活性较非晶态NiP合金低，但其比活性更高。这与载体的分散作用、载体与合金问相互作用、非晶态NiP／CNTs催化剂中Ni-H吸附键较弱以及碳纳米管的贮氢性能有关。非晶态NiP合金在碳纳米管上负载后热稳定性增强。这与载体所起的分散作用、传热贮热作用以及载体与合金间的相互作用密不可分。在非晶态NiP／CNTs合金中加入适量的稀土后，催化剂中镍含量、合金体相中的镍含量、催化剂的表面积以及活性镍表面积均有所增加。稀土能以结构效应以及电子效应促进非晶态NiP／CNTs催化剂苯加氢活性的提高。加入大量稀土会掩盖表面镍的活性位，从而导致催化剂活性下降。加入少量稀土改善了催化剂的热稳定性，主要是大尺寸稀土原子部分取代晶格中镍原子，降低了自由体积和原子扩散系数，同时稀土的分散作用有效阻止了镍原子聚集，使得非晶态合金更稳定。更多还原

【Abstract】 Carbon nanotubes （CNTs） were synthesized from decomposition of methane over three nickel-based catalysts prepared by co-precipitation method. Experimental results showed that the nature of catalysts could affect the yield, microstructures, morphology and properties of CNTs that were characterized by XRD, TEM, BET and TG. The addition of sodium carbonate into Ni-Cu-Al catalyst brought about slight decreases in the yield of CNTs and led to the morphology change from bamboo-shaped CNTs to large-inner-diameter CNTs. The sodium carbonate added in system played an important role in controlling the morphology of CNTs. Chemical vapor deposition technique based on porous anodic aluminum oxide （AAO） template was applied for synthesizing highly aligned carbon nanotube arrays. The channel diameter of AAO, thereby the diameter of CNTs inside the channels, could be easily regulated by altering anodization voltage.Amorphous NiP/CNTs catalyst was prepared by induced reduction, in which H₃PO₂ was used as the reducing agent, and amine was used to adjust the pH value of the solution. Benzene hydrogenation was used as a probe reaction for the study of effect of different treatment to CNTs and preparation conditions on catalytic activity of amorphous NiP/CNTs catalyst. Catalysts were characterized by XRD, TEM, ICP, TPR, XPS, H₂-TPD and DTA. The effect of support-CNTs and rare earth elements on catalytic activity and the thermal stability were discussed. Experimental results showed that CNTs oxidized by HNO₃ or activated by KOH resulted in improvements in catalytic activity of amorphous NiP/CNTs catalyst, and preparation conditions could affect its catalytic activity to some extent. NiP supported on CNTs belonged to amorphous structure. The particle size of NiP alloy supported on CNTs became smaller. Its dispersions and the specific surface area increased remarkably. In amorphous NiP/CNTs catalyst, both phosphorus and CNTs could donate electrons to nickel, making Ni electron-rich. The reduction of the electron-rich Ni became easy and the strength of hydrogen adsorptions on it was weakened. The catalytic activity of benzene hydrogenation for NiP/CNTs catalyst was lower than that for amorphous NiP alloy, but its specific activity was higher, which attributed to the dispersing effect of support, the electronic interaction between support and alloy, the relatively weak Ni-H bond and hydrogen-storage ability of CNTs. The amorphous NiP alloy supported on CNTs could improve its thermal stability, owing to the dispersing effect of support, heat sink of the support and interaction between support and alloy. The addition of a small amount of rare earth elements could increase the content of nickel in NiP/CNTs catalyst, the bulk content of nickel, specific area of catalyst as well as activate metal surface area. The small amounts of rare earth elements added in amorphous NiP/CNTs catalyst promoted the catalytic activity of benzene hydrogen because of structure effect and electronic effect. However, higher content of rare earth elements led to the coverage of surface Ni atoms by rare earths, therefore decrease of catalytic activity. The addition of rare earths enhanced the thermal stability of catalyst due to the possibility that a larger atom of rare earths compared with Ni and P partly displaced Ni in the lattice, resulting in less free volume and a lower rate of diffusing, moreover, such addition might prevent the gathering of Ni atom due to the dispersing effect of rare earth.更多还原