Development of Ultrafine Active Supported Metal Catalyst by Chemical Vapor Deposition

根据研究背景，将化学气相沉积法开发超细活性负载金属催化剂分为三个部分。第一步：将Ni(NO_3)_2分解成Ni(NO_3)_2，并喷射其甲醇溶液，制备Ni/SiO_2催化剂。催化剂的NiO颗粒被精细地还原到300-500A大小。通过以一氧化碳甲烷化反应为模型反应进行测试，发现该催化剂比普通预浸渍催化剂具有较高的活性。为了提高活性，氧化镍的粒径应进一步减小，但在此步骤中无法制备出300-500A以上的镍颗粒。第二步：采用蒸发的NiCl_2作为Ni源，但在该方法中，SiCl_4和NiCl_2氧化生成的Cl_2抑制了SiCl_2和NiCl_2的氧化，未反应的NiCl_2阻碍了氢的吸附，从而降低了催化活性。去除这个缺陷。第三步：在反应中加入水蒸气，生成的Cl_2被HCl的生成除去。通过这种改进，从数量上促进了向NiO的转化程度。NiO的过饱和蒸汽压比第一步提高，到100A时产生的颗粒变小。氧化镍与普通浸渍催化剂在粒径上无差异，但催化活性高于普通催化剂。究其原因，在制备过程中，氧化镍的最佳晶格应变为3-4x10^<-3>，且在快速淬火过程中晶格发生变形。结果表明，颗粒的生长速率受SiO2和NiO核的混凝过程控制。很明显，催化剂制备的基本项目取决于这项科学研究资助的基础。

Development of ultra fine active supported Metal Catalyst by Chemical vapor phase deposition is devided three parts by the research context.The first step: Ni/SiO_2 catalyst was prepared by decomposition of fume d Ni(NO_3)_2 from which was sprayed its methanol solution. The NiO particle of the catalyst is finely reduced to 300-500A in size. It was found that the catalyst is highly active than ordinary prepred impregnated catalyst by testing a methanation of carbon monoxide as a model reaction In order to promote the activty, the particle size of nickel oxide should be more reduced, but the nickel particle than 300-500A can not be prepared in this step.The Second step: So Vaporized NiCl_2 was used as a Ni source, but in th is method, Cl_2 which is produced by the oxidation of SiCl_4 and NiCl_2 inhibited the oxidation of SiCl_2 and Nicl_2 and unreacted NiCl_2 so retards adsorption of hydrogen that catalytic activity is depressed. To remove this defect.The third step: Adding the water vapor to this reaction, produced Cl_2 is removed by formation of HCl. By this improvemen, the extent of the conversion to NiO was quantitatively facilated. The Supersaturation vapor pressure of NiO is enhanced than the first step, and it becomes to produce smaller particle till 100A. In spite of no difference between the particle size of nickel oxide and ordinary impregnated catalysts, the catalystic activity is higher than theordinary catlysis. The reason could be deduced from the facts that the optimal lattice strain of nickel oxide are 3-4x10^<-3> and the lattices are deform during the rapid quenchingin the preparation. And it is revealed the growth rate of the particlesare controlled by coagulation process of SiO2 and NiO neucleus.It hasbe-come apparent that fundamental items of the catalyst preparation depends on the basis of this Grant-in-Aid for Scientific Research.