Efficient Metal Catalyst Preparation And Metal Enzyme Catalytic Performance

Catalysis is the decrease in the activation energy due to the participation of a substance called a catalyst and thereby changes the rate of chemical reaction without change in the quality and quantity of catalyst during the reaction. To study and use catalysis can greatly reduce the cost of production, improve product quality, protect the environment and make rational use of resources. This thesis devotes to the preparation of highly effective catalyst with large surface area, high catalytic activity and selectity by the nanometer material synthesis technology. The amorphous alloy catalyst prepared by chemical reduction method is a kind of nanocatalyst. Amorphous alloy catalyst is a kind of special material with short-range ordering while long-range disordering structure. The composition of alloy and unique structure can be easily molulated by this chemical reduction method, resulting in excellent catalytic activity and selectivity. Moreover, there is low environmental pollution during the preparation process. All these advantages of this highly efficient catalyst is consisten with the development trend in today's chemical industrial with the scientific concept of saving energy and environmental protection, attracting the increasing attention of people.In this paper, we prepared amorphous catalysts with different composition and/or shape by chemical reduction method, and investigated the effect of composition and morphology on the catalytic performances. In the last chapter, metal catalysts were combined with enzyme, and used in catalytic transformation of biological biomass (dextrin). Around the main aspects, this paper is developed in the following areas: (1) At low temperature, In-B amorphous alloy was prepared by chemical reduction of InCl3 solution with high concentration was reduced by KBH4 solution. The as-prepared sample had good thermal stability, large specific surface area, and high catalytic activity. By XRD, TEM, BET, XPS, DSC and other testing methods, this catalyst has been identified to be amorphous alloy. This structure transformation from crystal to amorphous can also be observed with the change of stirring speed. High-speed resulted in nanoparticles with small size and amorphous alloy structure. During Barbier-type reaction of benzaldehyde or acetophenone with allyl reagent in water-medium, the as-prepared In-B amorphous alloy catalyst exhibited much higher activity than the regular(2) Hollow Ni-B nanospheres were synthesized through chemical reduction of nickle ions with borohydride in an emulsion system comprised of toluene, sodium dodecyl benzene sulfonate and water. With the characterization of XRD, TEM, BET, XPS, DSC and other testing methods, the resulting hollow Ni-B nanospheres were identified to be amorphous alloys with a hollow chamber. Sodium dodecyl benzene sulfonate played a significant role in fabricating hollow Ni-B nanospheres, because sodium dodecyl benzene sulfonates have hydrophilic groups and lipophilic group. Two groups have a significant influence on the formation of hollow Ni-B nanospheres, because hydrophilic groups can adsorb Ni²⁺. During liquid-phase m-dinitrobenzene hydrogenation to m-phenylenediamine, the as-synthesized Ni-B catalyst exibited much-higher activity and even better selectivity than the regular Ni-B prepared by direct reduction of nickle ions with borohydride and Reney Ni.(3) Metal catalyst was combined with enzyme, and used in the one-pot hydrolysis-hydrogenation of dextrin to sorbitol. Firstly, we investigated the effet of saccharifying enzyme on the hydrolysis of dextrin, and selected the optimal temperature and pH value for enzyme, as well as the amount of metal particles. In the presence of metal catalyst, the optimal conditions for hydrolysis by enzyme were also selected. Through the screening of catalyst, metal catalyst with higher catalytic activity was established and a higher sorbitol yield was achieved.