Preparation Of High Performance CuO-CeO₂ Catalysts And Investigation Of The Interaction Of CuO And CeO₂

Fuel cells are called the forth dynamoelectric equipment following waterpower, fire power and nuclear energy as an efficient and clean energy resource,which can substitute the gas engine.The international energy orgnaziation forecast that fuel cells is one of the most attracted methods of generating electricity in the 21 century,proton exchange membrane fuel cells(PEMFC)becomes the uptodate fuel cells,for its merits(the high density of work energy,the long work time,the rapid responsion,the low operating temperature,and so on),and especially attracts people's attention,for its application in the moving energy aspect in the future.H₂ rich-gas made from reforming hydrocarbon is primary fuel source of PEMFC. Generaly,there is about 1%CO in H₂ rich-gas,but the content of CO in H₂ rich-gas must under 10ppm,or else it will lead electrode to poision.Preferential oxidation is the most simple and effective method for decreasing the CO content to ppm level in H₂ rich-gas.As the catalysts of preferential oxidation,the non-noble metal catalysts CuO-CeO₂ show favorable catalytic activity for preferential oxidation CO,and become the hot field in recent years.In the present dissertation,the influence of preparation methods on the catalytic performance of CuO-CeO₂ catalysts in the preferential oxidation of carbon monoxide in excess hydrogen has been investigated and CuO-CeO₂ catalysts and their application in the preferential oxidation of carbon monoxide in excess hydrogen have been studied in detail.Furthermore,the influence of preparation conditions of mechanical mixing method and hydrothermal method on the catalytic performance of catalysts has been investigated extensively.Finally,the mechanism of the reaction over CuO-CeO₂ catalysts and the influence of reaction conditions have also been studied.Some valuable results,as shown in the following,have been achieved.Firstly,the catalytic performance of CuO-CeO₂ catalysts prepared by different methods such as mechanical mixing,impregnation and hydrothermal methods in the preferential oxidation of carbon monoxide in excess hydrogen is compared,and CuO-CeO₂ catalysts prepared by hydrothermal method are found to possess a higher catalytic performance in the preferential oxidation of carbon monoxide in excess hydrogen.Secondly,the influence of preparation conditions on the catalytic performance of CuO-CeO₂ catalysts in the preferential oxidation of carbon monoxide in excess hydrogen has been studied.The result shows that both catalysts have the best catalytic performance with the 5wt%Cu loading and calcined at 500℃.And CuO-CeO₂ catalysts with high catalytic performance have been prepared,which has a catalytic performance as well as,if not better than,that of precious metal-based catalysts and those reported in literatures.At a space velocity of 60.000 ml g^-1h^-1and a reaction temperature of 130℃,carbon monoxide conversion and selectivity are 99.6%and 57.4%,and a temperature window with a high carbon monoxide conversion is formed.In addition,the influence of different reaction conditions on CuO-CeO₂ catalysts prepared by hydrothermal method is studied.The study indicates that hydrogen has inhibitory effect on the catalytic performance of CuO-CeO₂ catalysts in the preferential oxidation of CO in excess H₂,and the catalytic activity is inhibited obviously while the feed gas has some water and carbon dioxide,but the selectivity is not effected.CuO-CeO₂ catalysts have stable catalytic activity undergoing stability experiment for 50 h.In this work,CuO-CeO₂ catalysts were characterized by XRD,H₂-TPR,BET, TEM,UV-Raman,CO-TPSR,TG-DTA,O₂-TPD and XPS techniques.The copper oxide species,according to the dispersion and valence of copper,are classified as following:(a)Copper oxide associated tightly with surface oxygen vacancies.(b)One-,two- and three-dimension copper oxide entities.(c)The Cu+ stabilized by oxygen vacancies.(d)Bulk copper oxides etc.Furthermore,according to the contact between copper oxide and oxygen vacancies, there exist strong,weak and null interactions,which play an important role in the sygnism and the catalytic performance in the preferential oxidation of carbon monoxide in excess hydrogen.