Cu/MgO催化剂上NO-TPO和CO-NO反应性能

采用TPD技术考察了Cu/MgO催化剂表面NO的脱附和分解。载体MgO表面有两类NO吸附中心,为MgO表面碱中心。负载Cu后,由于Cu覆盖了MgO表面碱中心,使Cu/MgO(>1%)催化剂表面只有吸附在Cu上的NO。热脱附过程伴有明显的分解,产物为N~2,N~2O和O~2。CO-NO反应低温有利于N~2O生成,而高温有利于N~2生成,反应活性与NO-TPD峰温有较好的对应关系。NO在催化剂表面解离(NO~a→N~a+O~a)是CO-NO反应的速控步。

CO-NO reaction and NO-TPD over Cu/MgO catalysts

Temperature programmed desorption(TPD) was used to study the desorption and decomposition of NO adsorbed on Cu/MgO catalysts. These are two kinds of NO adsorption sites on MgO surface, which are attributed to the basic sites. The basic sites of MgO surface are covered with Cu, therefore there are only one NO adsorption on Cu/MgO catalyst surface except Cu/MgO (1%), which is attributed to metal Cu. The adsorption NO undergoes extensive decomposition to form N~2, N~2O and O~2 during NO thermal desorption on all catalysts. CO-NO activity of catalysts is closely related to their NO decomposition activity. CO-O~2 reaction is easier than CO-NO on all catalysts. The dissociation of NO on catalyst to form N~a and O~a is the rate determing step of CO-NO reaction. N~2O formation dominates at lower temperature during NO reduction, whereas N~2 formation dominates at higher temperature.