Construction Of High Efficiency Amorphous Alloy Catalytic Materials And Its Application In Energy Conversion

In order to improve efficiency of chemical processes, to reduce emission of pollutants, as well as to insist sustainable development strategy in green chemistry, one of the most important tasks is to develop new materials, especially new catalytic materials. Amorphous alloys, one of the important novel catalytic materials, are a kind of non-equilibrium metastable materials in thermodynamics with long-range disordered but short-range ordered structure. Due to their superior catalytic properties in comparison with the crystalline counterparts, amorphous alloys have attracted growing attention from both academia and industry. Up to now, amorphous alloys prepared by chemical reduction method have been widely studied as heterogeneous catalysts. Because the reaction between metallic ions and borohydride is highly exothermic, particle aggregation inevitably occurs owing to the high local temperature. Consequently, the amorphous alloys prepared by the traditional chemical reduction method usually have low surface areas, which is harmful to activity. Additionally, the amorphous alloys are also prone to deactivation resulted from crystallization during the using process. As a result, development of novel and efficient amorphous alloys is the key to tackle the above problems.Based on the development of novel and efficient amorphous alloy catalysts, the following aspects are discussed in this thesis. In addition, the catalytic performances of the as-prepared amorphous alloys in energy conversion are investigated.(1) Control over composition and morphology of catalysts are essential and necessary to develop superior catalysts. We prepared the hollow Ni-Co-B amorphous alloy catalyst through the vesicle-assisted chemical reduction method. The catalysts were used for liquid-phase hydrogenation of 2-ethyl-2-hexenaldehyde, showing excellent activity and stability. In the contrast experiment that with different active component, it is concluded that the metal Ni in the reduction process is mainly used to catalyze the hydrogenation of C=C. Co was used to catalyze the hydrogenation of both C=C and C=O. In the cycling test, we used the traditionally-prepared Ni-Co-B amorphous alloy for comparison. It showed that the hollow Ni-Co-B amorphous alloy was much better than the traditional one in both the activity and stability.(2) Supporting the amorphous alloys on porous carriers can not only enhance the dispersion degree of active sites, but also improve their thermal stability. We prepared highly-dispersed Ru-B amorphous alloys by using mesoporous carbon as support, which was encapsulated by a radially oriented mesoporous silica shell. Adopting a regional selective etching method, yolk-shell nanoarchitectures with a Ru-containing core and a silica shell were fabricated. Because the mesoporous carbon was easy to enrich the etching agent, it selectively etched out the cavity to left shell. By using silica(MCM-41) as core for comparison, the region-selective etching mechanism for the formation of the yolk-shell structure is proved. In order to confirm the generality of this strategy, we also used other etching agents under the same optimized conditions. Similar yolk-shell structure could be achieved. Finally, we use the above catalyst for the one-pot conversion of dextrin to sorbitol. The results showed higher activity and stability.(3) Based on the above results, we developed a stepwise crosslinking approach to preparing a new bifunctional catalystsystem that integrates enzyme and chemical material into a biochemical composite. The first step was to crosslink the enzyme and catalyst with glutaraldehyde. Then the long chain glucosan was used for further grafting between enzyme molecules. We used various characterization methods to prove the mechanism for the formation of biochemical composite. In order to evaluate the activity and stability of the catalyst, we use it for the hydrolysis-hydrogenation conversion of dextrin to sorbitol, showing excellent catalytic efficiency.