Investigation Of Preparation Of N₂O Direct Catalytic Decomposition Catalyst And Experimental Study On Its Technological Conditions

N₂O is not only an important greenhouse gas,but also can seriously damage the ozone layer structure.The aim of the paper was focused on direct catalytic decomposition of N₂O produced from adipic acid factory exhaust gas.A series of?-Al₂O₃ supported transition metal oxide catalysts were prepared for direct catalytic N₂O decomposition by impregnation method.Characterization of physical and chemical performances were carried out by methods of XRD?BET?H₂-TPR?SEM et al.Reaction activity of N₂O direct catalytic decomposition was examined in a miniature fixed bed reactor apparatus.Finally,the forming process of catalyst was studied with the aim of industrial pilot test.A desgned result was produce for the process flow,reactor structure and operation parameters of the pilot apparatus.The experimental investigate was carried out to examine the activity of single component Co/?-Al₂O₃ catalyst for catalytic decomposition N₂O.The optimum load amount of Co oxide was about 9 wt%?Co₃O₄/?-Al₂O₃weight ratio,similarly hereinafter?.The results of XRD characterization showed that there was interact between active component and carrier.CoAl₂O₄ composite metal oxides with spinel structure would be observed in the samples.Based on Co oxide load amount of 9 wt%,the experiment was conducted to investigate the reaction activity of doped Cu oxide component.For Co-Cu/?-Al₂O₃ catalyst,the optimum load amount of Cu oxide for catalytic decomposition N₂O was found to be about 15 wt%.At100%?Then catalysts were prepared with different molar ratio of Ce/Co and different mass ratio of Ce/supported.However,the promotion of catalyst activity was not observed.By the result of characterization the reason may be explainated that the interaction between CeO₂ and CoAl₂O₄ leads to obvious crystallinity enhancement of the catalyst activity center.This maybe reduced the specific surface area of the catalyst.Therefore the catalyst activity had no increase.To explore the effect of different additives on CoCu/?-Al₂O₃ catalyst activity,a series of metal oxide were selected,including the transition metal Fe?Mn?Ni?Zn,alkaline earth metals Mg?Sr?Ba,alkali metal KOH?KNO₃ and rare earth metals Ce.The experimental results revealed that the doping of Fe and Ce oxide expressed execellent performance.Both could change the redox property of Co-Cu/?-Al₂O₃ catalysts.When the N₂O decomposition rate reached 100%,the reaction temperature were about 545?.Based the optimal mixing ratio of the CoCuCe,the effect of carrier on the catalyst activity was investigated.Selected carriers included MgO?TiO₂?USY molecular sieve,and different proportion of mixed MgO and?-Al₂O₃.The activity of catalytic decomposition of N₂O was sorted by MgO>USY=?-Al₂O₃>TiO₂.For different ratio of Mg/Al catalyst,the experimental results showed that there was no significance synergistic effect between the two components,maybe just simple mechanical mixing.Based on the optimization of composite metal oxide catalyst,experimental work was carried out to study the industrial scale-up test catalyst forming conditions.Conditions of consideration mainly included nitric acid concentration,Sesbania powder content,water/powder ratio,drying condition,calcination temperature and temperature programming.The target parameters were selected as reaction activity and mechanical strength of the catalyst.Finally,different shape and size of catalyst molding molds were designed,including cylindrical,clover and five leaves of grass.The catalytic activity and lifetime test of the catalyst were carried out in the laboratory pilot reactor.Under the reaction temperature at 580?,the continuous test experiment was carried out for 120 h.The conversion rate of N₂O was higher than 95%.No obvious decrease of activity was observed.By reference to the Liaoyang Petrochemical plant,a process flow,operation and equipment parameters were designed for the pilot unit of end gas treatment build in future in Kailuan Group coal chemical plant.