Synthesis Of Non-reducible Supports And Their Application In CO Oxidation

The low-temperature CO oxidation is of great interest due to its relevance in practical applications?such as in CO removal from hydrogen feed of polymerelectrolyte-membrane fuel cells,exhaust gas,and environmental air cleaning and sensing?and as a model reaction for the understanding of catalytic mechanisms.Among them,supported nano-gold catalyst has received extensive attention due to its excellent performance.Inert supports have been utilized as supports of gold catalysts due to their high specific surface area,good thermal stability and chemical stability.However,for this type of support,there are still two problems to be solved:Firstly,supports with controlled crystal structure,texture parameters,morphology and surface properties should be prepared by appropriate method;secondly,the catalytic activity of gold catalysts loaded on inert supports should be further improved.In response to these questions,alumina and boron nitride is selected in this paper,and the type of raw material,synthesis method,calcination temperature and other technological conditions are adjusted in order to achieve controllable preparation of supports.And catalytic performance of corresponding gold catalysts are also improved by changing the type and amount of assistant.The specific research content and results are as follows:?1?Alumina was prepared by hydrothermal method and calcined at different temperature.Taking aluminum nitrate and ammonium carbonate as raw materials,sheet-like alumina can be obtained after being calcined at 500°C,then 3 wt%Au was loaded and complete conversion of CO was realized at 20°C when pretreated with reducing atmosphere,whose catalytic activity is the best.The support has a rough surface and moderate acidity,and can effectively anchor the gold nano particles.The catalyst can be completely converted at 60°C even being calcined at 500°C.?2?The transition metal nitrate is introduced in situ during the preparation process of alumina,which introduces transition metal element into the body phase of alumina.It was found that 1wt%Au loaded on Ni-Al₂O₃ with n(Al³⁺):n(Ni²⁺)=20:1 shows the best catalytic performance,achieving complete CO conversion at 60°C.The catalysts are characterized by TEM,H₂-TPR,O₂-TPD and the results exhibit that the introduction of Ni can assist in anchoring gold particles and providing reactive oxygen species for CO oxidation,which are reasons why the catalytic activity improved.?3?Boron nitride samples are prepared using"top-down"and"bottom-up"methods,then transition metal promoters are introduced to the support by impregnation method,after that,gold nano particles are loaded by deposition-precipitation method.The results show that catalysts with ball-milled boron nitride as support,Cu as promoter can improve the catalytic performance effectively.The catalysts show the best activity and achieve the complete conversion of CO at 180°C.It was found by characterization that the boron nitride after ball milling has large specific surface area and abundant surface groups,which makes it anchor the Au-Cu active component effectively,so the reaction of CO oxidation can be facilitated.