| Nitrous oxide(N2O)is one of the serious green-house gases.It can also destroy the ozone-layer in the atmosphere.Among many technologies for reducing N2O emission,the method of catalytic decomposition N2O has more obvious advantages,such as simple process,low investment and no secondary pollution.The core technology of this method is the development of catalyst.The main content in this paper includes two parts of experimental work.The first part of the research work involved the preparation of CuY(composite copper and yttrium oxides,the same below)series catalysts in laboratory.The second part of the study concerned the operation conditions in a pilot plant with CoCu Ce industrial catalyst.In the first part,the catalysts of Cu/?-Al2O3?CuM/?-Al2O3?CuY/?-Al2O3?CuYM/?-Al2O3 and CuY catalyst loaded on different supporters were prepared by incipient-wetness impregnation method.The catalysts were evaluated for activity and analyzed by physicochemical property characterization.For Cu/?-Al2O3 catalyst,the catalyst exhibited the highest activity when the loading of Cu was 12%,on which the complete decomposition temperature of N2O was 547 ?.When added the second component Y to Cu/?-Al2O3 catalyst,the CuM/?-Al2O3 catalyst showed the highest activity,the complete decomposition temperature of N2O was 501 ?.The CuY/?-Al2O3 catalyst,with equal loading of Cu and Y(12%,respectively)achieved the highest catalytic activity and the complete decomposition temperature was 488 ?.With the addition of Y,the phase analysis indicated that the grain size of Cu O species became smaller and could promote the reducibility of the catalyst.The conversion rate of N2O on CuY12/?-Al2O3 catalyst could maintain 80% in a 100 h thermal stability test under 460 ?.Moreover,the hydrothermal stability for CuY12/?-Al2O3 catalyst was investigated.The result showed that the catalytic activity decreased obviously when the steam was added to the feed.However,the catalytic activity almost recovered completely once the steam was removed.The effects of different additives on the activity of CuY/?-Al2O3 catalyst were investigated.The result revealed that the addition of rare earth metal Re(Re = La ? Ce ? Pr ? Nd)enhanced the activity of CuY/?-Al2O3 catalyst evidently.When Ce/CuY=0.3,the complete decomposition temperature of N2O was 476 ?.The thermal stability and the effect of steam on CuYCe0.3/?-Al2O3 catalyst were also investigated.For CuY catalysts loaded on different supporters,HZSM-5 and ZrO2 exhibited higher acitivity.In the second part,CoCu Ce/?-Al2O3 industrial catalyst developed before in our laboratory was prepared by extrusion molding method.Firstly,the activity evaluation and thermal stability of CoCu Ce/?-Al2O3 industrial catalyst were tested in a small fixed-bed reactor in laboratory.And the operation conditions in a pilot plant filled with industrial catalyst were tested for the catalytic decomposition of a tail gas containing N2O in Kailuan(Group)company.The activity evaluation of the industrial catalyst showed that the complete decomposition temperature of N2O was 610 ?.The conversion rate of N2O still maintained 95% in a 1000 h thermal stability test under constant conditions.The operation conditions experiments consisted of two periods.In the first period,a total of 92.2 kg of CoCu Ce/?-Al2O3 industrial catalyst was filled in the reactor and N2O conversion rate was 77.7%,which did not reach the expected target.In the second period,a total of 134.9 kg of the industrial catalyst was supplied to the reactor.The optimum operation conditions were obtained that the inlet concentration of N2O was 12%,the space velocity was 1900 h-1,the inlet temperature was 500 ? and the outlet temperature was 695 ?.At this condition,a highest N2O conversion over 99% was achieved and the expected goal was derived. |
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