纳米镍粉的固相合成及其催化性能研究

【作者】 刘红；

【导师】 菅盘铭；

【作者基本信息】 扬州大学 ， 物理化学， 2006， 硕士

【摘要】 一、催化剂的制备及表征固相法制备纳米Ni粉:以NiSO₄·6H₂O和NaOH为原料,首先采用室温固相法制备纳米Ni（OH）₂粉,经过95%乙醇和蒸馏水交替洗涤去除其中的Na+、SO42-等杂质离子,得到草绿色粉末;粉末再经过110℃烘干8h,350℃焙烧4h、得到黑色粉末纳米NiO;NiO在加热炉中通入氢气还原,400℃还原4h得到灰黑色纳米Ni粉。以NiO为载体采用浸渍法分别掺杂不同含量的Pd、Pt等贵金属对此催化剂进行改性,制得Pd/Ni、Pt/Ni催化剂。采用XRD、TEM、SEM、IR、XPS、BET等手段对催化剂进行了表征。结果表明制备的纳米Ni粉为结构稳定、纯度高、粒径分布均匀的纳米颗粒,平均粒径在20-25nm;掺杂贵金属Pd、Pt后,产物的结构没有发生明显的变化,只是粒径有所增大。所制得的催化剂在空气中均能稳定存放,不易失活,并且在催化剂使用过程中仍保持结构完整。以硝基苯、肉桂醛、马来酸酐等物质的加氢反应为探针实验考察了催化剂的活性。实验发现,纳米Ni粉在硝基苯催化加氢反应中表现出很好的活性,在相同的条件下与Raney-Ni相比,纳米Ni粉具有更好的加氢效果,在工业生产中具有广阔的应用前景。在肉桂醛催化加氢反应中,贵金属Pd对催化剂的改性效果远比贵金属Pt优越。马来酸酐的转化率和选择性都很高,丁二酸酐的收率高达98.7%二、硝基苯催化加氢性能研究以硝基苯加氢制备苯胺为探针反应,考察了纳米Ni粉及掺杂贵金属Pd、Pt催化剂的加氢性能,并在相同条件下与Raney-Ni做了比较;同时考察了反应温度、催化剂用量、氢气压力等因素对催化剂反应活性的影响。结果发现,120℃、催化剂用量在～4%,对硝基苯加氢反应有利;同时还发现氢气压力对硝基苯转化率有明显的影响,在催化剂用量为2.0%,120℃反应10h,氢气压力为0.8MPa条件下,硝基苯转化率高达76.42%,苯胺的选择性为100%;在相同的条件下,纳米Ni粉作为催化剂,硝基苯加氢的转化率选择性和选择性比Raney-Ni优越的多,硝基更多还原

【Abstract】 1. Preparation and characterization of catalystsNickel （NiO） powders with the sizes in the range of 20–25 nm were prepared via the reduction of nanosized NiO powders （The nanosized NiO powders were derived from low temperature （350℃） calcinations in air of nanosized Ni（OH） powders, which were firstly prepared through the room temperature solid state reaction between NiSO₄·6H₂O and NaOH） by H₂ at 400℃for 4 h and a series of palladium and platinum catalysts supported on NiO were prepared. The samples were characterized using XRD、TEM、SEM、IR、XPS and BET methods. The catalytic activity of the obtained nanosized Ni powders for hydrogenation of nitrobenzene, cinnamic aldehyde and maleic anhydride was investigated. The catalysts we made had high stability in the air and maintained the configuration of catalysts during the reaction process.The experimental results shown that the catalysts we made had high stability in the air and maintained the configuration of catalysts during the reaction process. Supporting palladium and platinum hadn’t changed the configuration of the sample. It suggested that the obtained nanosized Ni powders behaved better catalytic activity for hydrogenation of nitrobenzene to aniline than Raney-Ni. The experimental results shown that the catalyst improved by metal Pd had higher activity than the catalyst improved by metal Pt in hydrogenation of cinnamic aldehyde and the nanosized Ni powders shown high catalytic activity for hydrogenation of maleic anhydride.2. The studies of the catalytic activity for nitrobenzene hydrogenationThe catalytic activity of as-prepared Ni powders for hydrogenation of nitrobenzene to aniline was studied, and the factors such as temperature, catalyst amount and H2更多还原