Direct Catalytic Decomposition Of Nitrous Oxide Over Supported Copper-iron Oxide Composite Catalyst

In this paper,cupric and ferric oxide were selected to prepare copper-iron oxide composite catalyst for nitrous oxide direct catalytic decomposition.The oxide composite was supported on γ-Al2O3 by equal volume impregnation method.Experiments for Cu/Fe molar ratio and Cu-Fe loading indicated the optimal sample was Cu2Fe1O/γ-Al2O3 with total Cu-Fe loading of 25%.Nitrous oxide complete decomposition temperature was 530℃ over this catalyst sample.The operation conditions were investigated for nitrous oxide decomposition reaction on this catalyst sample.The results show that the increase of volumetric space velocity and nitrous oxide concentration would cause the decrease of decomposition rate of nitrous oxide.There was little effect on the decomposition rate of nitrous oxide for low oxygen concentration in the feed gas.However,with the increase of oxygen concentration,decomposition rate of nitrous oxide obviously decreased.A thermal stability experiment expressed that the decomposition rate of nitrous oxide was maintained about 90%for 100 h at 515℃ with not obvious inactivation.The intrinsic kinetics study of the catalyst showed that the nitrous oxide decomposition reaction was a first-order reaction with 124.2 kJ/mol activation energy.The effects of different kinds of metal oxide on the performance of copper-iron oxide composite catalysts were examined.Activity evaluation results show that the addition of Co and Mn oxide could cause increase of catalytic activity in low temperature range.There was no obvious effect on the complete decomposition temperature.The addition of Ce oxide could slightly increase the reactivity of the catalyst.Characterization results show that the addition of transition metal Co,Mn and rare earth metal Ce oxide could increase the dispersion of CuO on the surface of the carrier and reduce the reduction temperature of CuO species from Cu2+state to Cu0 state on the surface of the catalyst.For industrial application,the optimal copper-iron oxide composite catalyst was selected to research the industrial scale catalyst forming conditions.Considering the single factor variable method and the orthogonal experiment method,nitric acid concentration,water-powder ratio and sesbania powder content were selected as factors effect on the activity and mechanical strength of the shaped catalyst.Finally,the optimal molding conditions were achieved to prepare industrial copper-iron oxide composite catalyst.Evaluation results of the industrial size catalyst prepared under this condition showed that the catalytic activity of the shaped catalyst decreased slightly.