CAJ | 학술논문

利用恒温还原和程序升温还原技术研究了水分压对铁基费托合成催化剂还原路径、还原机理和表观活化能的影响.程序升温还原结果表明,水分压对催化剂的还原路径没有明显的影响,催化剂均首先由α-Fe_2O_3还原为Fe_3O_4,然后超顺磁态Fe_3O_4先还原为FeO,再还原为α-Fe,而顺磁态Fe_3O_4则直接还原为α-Fe.恒温还原结果表明,催化剂在2.5%H_2O-97.5%H_2气氛中还原时,还原过程达到平衡时的还原程度随还原温度的升高而增加.利用Hancock-Sharp方法分析了恒温还原过程的动力学模型.结果表明,还原温度较低时,催化剂在2.5%H_2O-97.5%H_2气氛中还原时受内扩散模型控制;还原温度较高时则受晶相形成与生长模型控制.利用Kissinger方法计算了还原过程的活化能,发现随着水分压的增加,表观活化能呈增大的趋势.水分压对Fe_3O_4还原为α-Fe过程的影响大于其对α-Fe_2O_3还原为Fe_3O_4过程的影响.
이용항온환원화정서승온환원기술연구료수분압대철기비탁합성최화제환원로경、환원궤리화표관활화능적영향.정서승온환원결과표명,수분압대최화제적환원로경몰유명현적영향,최화제균수선유α-Fe_2O_3환원위Fe_3O_4,연후초순자태Fe_3O_4선환원위FeO,재환원위α-Fe,이순자태Fe_3O_4칙직접환원위α-Fe.항온환원결과표명,최화제재2.5%H_2O-97.5%H_2기분중환원시,환원과정체도평형시적환원정도수환원온도적승고이증가.이용Hancock-Sharp방법분석료항온환원과정적동역학모형.결과표명,환원온도교저시,최화제재2.5%H_2O-97.5%H_2기분중환원시수내확산모형공제;환원온도교고시칙수정상형성여생장모형공제.이용Kissinger방법계산료환원과정적활화능,발현수착수분압적증가,표관활화능정증대적추세.수분압대Fe_3O_4환원위α-Fe과정적영향대우기대α-Fe_2O_3환원위Fe_3O_4과정적영향.
The effect of H_2O partial pressure on the reduction pathway, mechanism, and apparent activation energy of an iron-based Fischer-Tropsch catalyst was investigated by isothermal and temperature-programmed reduction (TPR). The TPR results indicated that the H_2O partial pressure had no obvious influence on the reduction pathway of the catalyst in H_2. α-Fe_2O_3 in the catalyst was first reduced to Fe_3O_4. The formed superparamagnetie Fe_3O_4 was reduced to a-Fe via FeO as an intermediate, while the formed paramagnetic Fe_3O_4 was reduced to α-Fe directly. The isothermal reduction of the catalyst showed that the reduction degree of the catalyst increased with the increase of reduction temperature when the reaction approached to equilibrium. The reduction mechanism analyzed based on the Hancock-Sharp method indicated that the reduction of the catalyst in 2.5%H_2O-97.5%H_2 at lower temperature was controlled by the inner diffusion model. However, at higher temperature the reduction process was controlled by the formation and growth of nuclei model. The apparent activation energy calculated based on the Kissinger method was increased with increasing H_2O partial pressure in H_2. The H_2O partial pressure had stronger influence on the reduction of Fe_3O_4 to α-Fe than that on the reduction of α-Fe_2O_3 to Fe_3O_4.