Study On The Catalytic Characters Of Colloidal Copper Catalysts And Theoretical Calculations

This paper studies the optimal reaction conditions for the preparation of colloidal copper catalysts without protection of N₂. In the presence of stabilizer Poly(N-Vinyl-2-Pyrrolidone)(PVP), copper chloride solution is reduced by hydrazine hydrate, at 80℃ with pH=7.0±0.5, which can prepare stable colloidal copper. Colloidal copper catalysts in different particle sizes with high activity are obtained under different reacted conditions. After that, the substance shape and size are respectively affirmed by UV, XRD TEM and Laser Particle Size Analysis. The colloidal copper is a high active catalysts for hydration of acrylonitrile to acrylamide, and its activity has relation to the particle size. It presents that the particle size of higher active colloidal copper is 40⁵0nm. The special characters of copper colloidal catalyst is the high selectivity in the reaction of hydration of acrylonitrile to acrylamide. According to the properties of defect on the surface of colloidal copper particles, the reasons of the high selectivity are analyzed, (a) The type of the active centre is singled. From the theories of defect and experimental results, it presents that the active centre of metal copper is not point defect, but the end point of dislocation, (b) The structure of the active centre is stable. Experimental results show that the mechanic properties of colloidal copper particle are high hardness and high strength, which keeps the structure of active centre stabling. The point is also presented that a proper size space is needed to permit active centre existing stably on the surface of catalyst. This explains the reason that colloidal catalyst particles under a certain size will lose its catalytic activity, not the smaller the better. The protection of PVP for colloidal copper is also discussed. On the basic of polymer irregular clew statistical formula, some expressions are reasoned out. Some experimental phenomenon are explained combining with the theory of cage effect. Lastly, the adsorption of acrylonitrile(AN) on the different sites of Cu(100) surface has been studied theoretically bymeans of model copper cluster Cuu(9,4,l) under using Density Functional Theory(DFT). AN standing up adsorbed perpendicular to the surface and bonded the metal sites via a nitrogen-metal interaction, which was a weak chemisorption. Chemisorption leaded to electron transfer from the AN molecule toward to the cluster. In the metal complexes Cuu AN, the a-binding via the lone-pair electrons on the N atom was observed.Chemisorption ontop site is preferred with the adsorption energy of 40.739KJ mol'], while both bridge and hole sites are less stable than top one, their adsorption energies are 36.2513 and 30.2158A.7-wo/"1. The calculation frequency results of the metal complexes Cui4 AN aresimilar to the experiment spectra results. Chemisorption causes the decrease of the complexes' entropy,which is contributed to paralleling entropy and turning entropy.