CuO/γ-Al_2O_3催化剂选择性催化还原NO

Selective Catalytic Reduction of NO over CuO/γ-Al_2O_3 Catalysts

利用溶胶凝胶法制备CuO/γ-Al2O3催化剂颗粒,在固定床上测试催化脱硝活性.CuO/γ-Al2O3在250～400℃范围内脱硝效率达到90%以上.硫化作用后催化剂的最佳温度窗口向高温方向移动.利用程序升温方法研究了CuO/γ-Al2O3对NH3的氧化性能,经硫化后催化剂对NH3的氧化性能下降,降低了催化剂在低温区脱硝活性.NH3和NO的脱附实验显示NH3和NO在催化剂表面存在明显的吸附现象.经硫化经后催化剂增加了对NH3的吸附量,降低了对NO的吸附量.暂态实验证明NH3以吸附态参与反应,而NO以气态或者弱吸附态参与反应.NO的吸附在实际SCR反应过程中影响有限.动力学计算显示溶胶凝胶法制备CuO/γ-Al2O3拥有较低的选择性催化还原反应活化能.

CuO/γ-Al2O3 granular catalysts were synthesized by the sol-gel method. Performance of CuO/γ-Al2O3 catalysts for selective catalytic reduction （SCR） was explored in a fixed bed adsorption system. The optimum temperature range for SCR of NO over fresh CuO/γ-Al2O3 is 250--400 ℃. The maximum efficiency reaches near 99% at 350℃. The operating temperature range increases on sulfated catalysts. Preliminary tests were carried out to study the behavior of NH3 over fresh and sulfated catalysts in the presence of oxygen. The sulfated catalysts in this experiment show relatively weak oxidation of NH3, which reduces denitrification efficiency at low temperature. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO/γ-Al2O3. Sulfation on catalysts improve adsorption capacity of NH3 and reduces adsorption capacity of NO. The transient behaviors of NH3 and NO were also studied, h is found that SCR reaction is zero order with respect to NH3 and first order with respect to NO. The adsorption of NO is not important in the SCR process. The activation energies of fresh and sulfated catalysts in the present study are lower than those by the wet-impregnation method.