Preparation Of Cobalt-based Composite Oxides Supported Gold Catalysts And Catalytic Decomposition Of N <sub> 2 </ Sub> O,

Nitrous oxide (N2O) is an important greenhouse gas with a long lifetime of about 120 years in the atmosphere. Although N2O is not the major contributor to global warming, it is much more potent than either of the other two most common anthropogenic greenhouse gases, CO2 and CH4. It is 310 and 21 times of the Global Warming Potential (GWP) of CO2 and CH4, respectively. Furthermore, N2O is an important source of stratospheric nitrogen oxides, which initiate a chain of cyclic reaction leading to stratospheric ozone destruction.The best option for N2O destruction is the direct decomposition of N2O to N2 and O2. The catalytic decomposition of N2O has been studied over various catalysts such as metal oxides, ion exchanged zeolites. However, most of the catalysts are not effective at low reaction temperature, the main problem is that the oxygen species formed during N2O decomposition adsorbs strongly on the catalyst surface leading to the inhibition of reaction rate and the decrease in catalytic activity.In the present thesis, the gold catalysts supported on Co-Al and Co-Ce mixed oxides were prepared and their activities for the catalytic decomposition of N2O were tested. BET, XRD, H2-TPR, TEM, and XPS techniques were used to characterize these catalysts. On the basis of the experimental data, some conclusions have been drawn as follows.(1) Au/Co-Al catalysts were prepared by using ion-exchanged and co-precipitation methods and their activities for the catalytic decomposition of N2O were tested, the result shows that the activity of Au/Co-Al catalyst prepared by using ion-exchanged method is higher than that using co-precipitation method. For Au/Co-Al catalysts prepared by using ion-exchanged method, the effect of preparation parameters, such as pretreatment of Au loading, HAuCl4 solution, and calcination temperature, upon N2O conversion was investigated, and the optimal preparation parameters of Au/Co-Al catalysts are that 1.1% of Au loading, pH value of HAuCl4 solution adjusted to 9.0 and 300°C of calcination temperature. It is indicated that the addition of Na species in Co-Al mixed oxide promoted the reduction of Co3+ to Co2+ and thus enhanced the catalytic activity for N2O decomposition.(2) Au/Co-Ce catalyst prepared by using co-precipitation method showed high catalytic activity in N2O decomposition because the addition of Au species into Co-Ce mixed oxide promoted the reduction of Co3+ to Co2+. In addition, the impregnation of Na species in Au/Co-Ce increased the dispersion degree of Au species and also promoted the Co3+ reduction, and hence improved the catalytic performance for N2O decomposition.