Study On Catalytic Processes Of Carbon Monoxide Coupling Reaction

Support effects on catalyst for CO coupling reaction to oxalate were studied using XRD, ChemBET,NH3-TPD, CO-TPD, TPR, TPO, XPS, Pulse Chemisorption and other methods. The diversity caused by calcinations temperature on crystal structures of the supports led to enormous difference on capability of catalysts. γ-Al2O3 support had stronger acidity which caused the decomposition of ethyl nitrite and the coupling reaction was retarded thereby. There were interactions among components of the catalysts that affect the capabilities of the catalyst. The α-Al2O3 with some transition crystal structure performed better as support. The active surface did more effect on the reactivity and selectivity of catalysts and the pore structure was an important factor. Deactivation test was carried out on FZHl00 catalyst, which had undergone for 1, 000 hours' scale-up circulating. The catalysts were deactivated at high temperature caused by temperature jump and then regenerated. The catalysts deactivated at the inlet and outlet parts of the reactor were difficult to regenerate and activities lost partially. The activities of most other catalyst can recover but the temperature sensitivity of catalyst will rise. BET surface area of catalyst changed in the deactivated-regenerated processes and the changes differ from the catalyst deactivated at different parts of the reactor. The crystal structure of support was not changed but the particle size of Pd was enlarged in the deactivated processes. In addition Fe2+ was oxidized into Fe3+ and the Fe3+ formed Fe2O3 crystal in the deactivated processes. XPS result showed the Pd0 on the catalyst surface was oxidized into Pd2+. The regenerated processes can recovered the changes partially. DFT method was employed to study some processes relative to CO coupling reaction. The results showed that CO can be adsorbed on top site, bridge site and hollow sites. The adsorbed states can change freely to others. The adsorption of methyl nitrite will lead to the decomposition to nitrous oxide and methoxyl on Pd surface. An important step for CO coupling reaction is CO move to methoxyl site and reacted to form methoxycarbonyl on palladium surface.