【作者】 骆益鸣；

【导师】 刘迎新；

【作者基本信息】 浙江工业大学 ， 工业催化， 2010， 硕士

【摘要】 纳米Au催化剂在许多化合物的还原反应中表现出良好的催化活性和选择性,是一类很有发展前景的选择性加氢催化剂。探明调控Au催化剂的加氢活性位点和对特定基团的选择性吸附位点的主要方法,是此类催化剂开发过程中迫切需要解决的问题。本论文采用液相还原法制备出聚乙烯吡咯烷酮（PVP）稳定的Au纳米粒子催化剂,采用沉积-沉淀法制备出一系列Au/M_xO_y-TiO₂催化剂和Au-M/TiO₂双金属催化剂,以肉桂醛选择性加氢为模型反应,考察了各催化剂的催化性能,利用XRD、TEM、XPS等方法对催化剂进行了表征。研究发现,Au纳米粒子催化剂对肉桂醛分子中的C=C键加氢具有很高的选择性,小粒径、高分散的Au纳米粒子对催化剂加氢活性有利。实验优化出Au纳米粒子催化剂的最佳制备条件为:PVP作稳定剂,PVP/Au摩尔比为20:1,还原剂KBH4/Au摩尔比为3:1。此条件下制备的Au纳米粒子尺寸在10 nm左右,且分散均匀,加氢活性高,肉桂醛转化率可达98.82%,苯丙醛选择性为63.78%。将Au纳米粒子催化剂负载后研究发现,Au催化剂的加氢选择性吸附位点与载体的物化性质有很大关系。惰性载体SiO₂负载的Au纳米粒子经H₂还原处理前后其选择性与未负载的Au纳米粒子相似,优先选择吸附C=C键。用活性载体TiO₂负载的Au纳米粒子经H₂还原处理前后,其选择性发生很大变化,未用H₂处理的催化剂选择吸附C=C键,而经H₂处理后的催化剂,优先选择吸附C=O键,这与H₂处理过程中活性载体TiO₂部分电子转移到Au粒子上,产生了许多富电子Au颗粒有关。研究发现,用沉积-沉淀法制备的Au/MxOy-TiO₂催化剂的活性和选择性受到助剂种类、助剂含量、添加方式等因素的影响。选用ZrO₂助剂,先对TiO₂修饰再负载Au制备的2%Au/5%ZrO₂-TiO₂催化剂对肉桂醛加氢具有较高的活性。研究发现,Co的添加方式会影响Au-Co/TiO₂双金属催化剂的加氢性能。先负载Co再负载Au制备的Au-Co/TiO₂双金属催化剂对肉桂醛加氢具有较高的催化性能。而Au、Co共沉淀制备的Au-Co/TiO₂双金属催化剂的催化性能较差,这是由于Co加入导致催化剂表面Au粒子发生聚集,生成50 nm左右的大尺寸Au粒子,使催化剂的活性位降低。更多还原

【Abstract】 Gold catalysts are a kind of promising catalysts for selective hydrogenation based on their good activity and selectivity for the reduction of many compounds. Finding good methods to tune the active sites and the selective adsorption sites is crucial for the further research and development of the gold catalysts.In this paper, a series of colloidal gold catalysts stabilized by poly（ N-vinyl-2-pyrrolidone） （PVP） have been synthesized by the liquid reduction of HAuCl4. A series of Au/MxOy-TiO₂ catalysts and Au-M/TiO₂ bimetallic catalysts were prepared by deposition-precipitation （DP） method. All the catalysts were tested in cinnamaldehyde hydrogenation, and characterized by XRD, TEM and XPS techniques.The results showed that the gold nanoparticle catalysts are active for the reduction of carbon-carbon double bond in cinnamaldehyde. Au nanoparticles with quite narrow size distribution and small diameters （ca. 10nm ） prepared at the conditions of the mol ratio of surfactant to Au at 20:1, and the molor ratio of KBH4 to Au at 3:1, exhibits excellent catalytic activity and selectivity for the hydrogenation of cinnamaldehyde. The conversion of cinnamaldehyde and the selectivity to hydrocinnamaldehyde are 98.82% and 63.78%, respectively.The property of intrinsic support plays a key role for the supported colloidal gold catalysts. Colloidal gold supported on SiO₂ shows high selectivity for the reduction of carbon-carbon double bond, the same as unsupported Au nanoparticle catalyst. Colloidal gold supported on TiO₂ followed reduction treatment using H2 behavior an opposite selectivity to the unreduced PVP-Au/TiO₂ catalyst,selective for the reduction of carbon-oxygen double bond. The reduction process facilitates electron transfer from support to gold, and the multielectron gold particles are responsible for the selectivity adsorption of the carbon oxygen double bond.The supported catalysts prepared by deposition-precipitation （DP） method are selective for cinnamaldethyde hydrogenation to cinnamyl alcohol. The type, dosage and adding method of metal oxide modifier significantly affect on the performance of Au/MxOy-TiO₂ catalysts via the different interaction between gold species and the support. Pre-deposition and pre-impregnating could make the zirconium modifier finely dispersed on the supports. The Au/5%ZrO₂-TiO₂ catalyst, prepared by decomposition of ZrO₂ on TiO₂ followed by loading gold, shows comparable performance in cinnamaldethyde hydrogenation.The addition of cobalt can influence the performance of Au/TiO₂ catalyst. Au-Co/TiO₂ catalyst synthesized by the pre-decomposition of cobalt followed by loading gold showed comparable performance in cinnamaldethyde hydrogenation. While the cobalt added by co-deposition with Au could lead to congregating of the gold nanoparticle, which is inert for cinnamaldethyde hydrogenation.更多还原