Preparation And Characterization Of Fe/CaO Catalysts And Its CO₂ Absorption Mechanism Under Biomass Directional Gasification

Energy is the foundation of our society for survival and development, and it is also the important factor which influences the development of the national economy. Energy mainly comes from fossil fuels currently. However, since they are non-renewable, energy shortage problem and environmental problem such as atmospheric pollution, ozone depletion and climate warming become increasingly sharp. Therefore, new energy represented by biomass, solar have become the focus of scholars at home and abroad. We can convert low grade biomass into high grade liquid fuels through directional biomass gasification technology. During the progress, we should solve some problems sunch as CO₂ removal, tar macromolecular deep conversion and H2/CO proportion adjustment. And CO₂ removal is the key of the progress. Reference to the literature, this paper proposed to doping Fe into CaO catalyst to prepare CaO-based catalysts which will be used in the directional biomass gasification technology. This paper mainly researched the performance of CaO-based catalysts for CO₂ absorption under biomass directional gasification.We systematically studied the performance of CaO for CO₂ absorption by investigating the effects of heating rate, CO₂ concentration and reaction temperature. The results showed: CaO conversion decreased with the increase of heating rate and increased with the increase of CO₂ concentration, we obtained the fitting formula of the equilibrium partial pressure of CO₂: RCO₂,eq（atm）=1.16×108exp（-21399/T（K））. During the experiments under the constant temperature, the final CaO conversion firstly increased, then decreased with the increase of constant absorbing temperature and CaO gradually deactivation with the increase of cycling times.We researched the influence of the doping of Fe. We prepared Fe/CaO sorbents under different factors like preparation method, precursor of Fe and the content of Fe. We abtained the influence of these factors for Fe/CaO absorbability through BET、XRD、TPD and TPR characterization methods and thermogravimetric experiment. The results showed that mix-FeN-5 have the best CO₂ absorbability.We also researched the dynamic characteristic of mix-FeN-5 and CaO absorbed CO₂. According to CO₂ absorption curves of mix-FeN-5 and CaO under different conditions, we chosed the point when rate of conversion droped to half the maximum rate of conversion as the demarcation point of rapid and slow reaction step and obtained dynamical modal of mix-FeN-5 and CaO. In the rapid reaction step, the activation energy of Fe/CaO is apparently higher than CaO. In the slow reaction step, the activation energy of Fe/CaO is a little higher than CaO.