The Investigation Of N₂O Decomposition Over Commercial Size Fe-beta Catalyst

Iron-zeolite catalysts are very active for decomposition N2O. In order to further industrial application, the effect of extrusion condition on zeolite’s global performances, such as activity, strength and high temperature stability ect were experimentally investigated under the condition of close to industry.In the present paper, N2O decomposition behaviors over Fe-beta powder were investigated. The physical and chemical properties of the zeolites prepared here under different molding conditions were analysed by means of some testing technology and characterization methods, such as particle strength measurement, plasticity measurement and evaluation of activity. The results showed:with the increase of nitric acid and the ratio of water to zeolite powder, the plasticity and strength of zeolite first increased and then decreased; the ratio of water to zeolite powder have little effect on the activity of zeolite, with the increase of nitric acid, the activity of zeolite first increased and then decreased, while the activity of zeolite decreased with the increase of SB powder. Studied with orthogonal experiments, the feasible extrusion condition were:SB powder20%, nitric acid6%, the ratio of water to zeolite powder65%. The macro-kinetics experiments of N2O catalytic decomposition over Fe-beta zeolites were carried out in an internal recycle gradientless reactor under the following conditions:0.12Mpa,430-500℃, various mole compositions of syngas, respectively. By means of Simplex optimal method, the power-law type macro-kinetic model of N2O decomposition were developed, and a good agreement with experimental data and those calculated by the kinetic models estimated was obtained. The reaction orders of N2O are0.677. And the activation energies of it is79.315kJ-mol-1. The model can guide to establish pilot plant and to realize its commercialization.The high temperature stability of Fe-beta catalyst was investigated. The catalysts are characterized by XRD, N2adsorption-desorption, FT-IR, H2-TPR, XPS, and catalytic activity is evaluated for N2O decomposition in fixed-bed reactor. Fe-beta catalysts treated in high temperature show low N2O decomposition activity. Fe-beta catalysts structure did not. collapse via high temperature. The treated Fe-beta catalysts activity decreased mainly due to the active center in the molecular sieve ferric species into poor active FeOx. In addition, some iron oxides migrate to the zeolite surface and accumulate, which lead to decrease the dispersion and the surface area of active center. The regenerating research indicated that the activity of deactivated Fe-beta catalyst almost restored after reduction in H2atmosphere.