稀土氧化物上SO_2和NO的催化还原 Ⅱ.用CO作还原剂的脱硫及反应机理

Catalytic Reduction of SO_2 and NO over Rare Earth Oxides Ⅱ. Reduction of SO_2 by CO and Its Mechanism

采用连续流动固定床石英反应器 ,在反应气体为 1%SO2 和 2 %CO ,流量为 180ml/min ,以及催化剂用量为0 5g的条件下 ,考察了经活化处理的稀土系列氧化物对CO还原SO2 的催化活性 ,探讨了空速、温度和水蒸气等因素对反应的影响 .所研究的样品依据对SO2 的转化能力可分为三组 :高活性的镧、镨、钕、钐、铕和钆氧化物 ;低活性的铈、钬和铒氧化物 ;无活性的铽和镝氧化物 .在活性最高的钕和钐氧化物样品上 ,45 0℃时SO2 的转化率 >98% .反应过程中 ,活性相为稀土氧硫化物 。

In a fixed bed flow reactor,eleven rare earth oxides were tested for the reduction of SO 2 by CO to elemental sulfur under the following conditions: composition of the gas mixture 1%SO 2, 2%CO and balanced N 2, flow rate 180 ml/min, catalyst weight 0 5 g. The oxides of La, Pr, Nd, Sm, Eu and Gd are very active after proper activation. SO 2 conversion reaches 98% at temperature 450 ℃ over Nd 2O 3 sample. The oxides of Ce, Ho and Er show lower activity, and the oxides of Td and Dy possess no activity for the reaction. The activity can be related to the ease of sulfidization from oxides to oxysulfides, and a COS intermediate mechanism is confirmed in the reduction reaction over the high active catalysts, while both COS intermediate mechanism and redox mechanism may be involved over the less active catalysts. The influence of temperature, gas space velocity and water vapor on the reduction reaction were also discussed.