硫化CoMo催化剂上H_2同时还原NO和SO_2的研究 Ⅰ.H_2还原NO反应

Catalytic Reduction of NO and SO_2 by H_2 over Supported Sulfided Catalysts Ⅰ. Catalytic Reduction of NO by H_2

研究了Al2 O3 担载的硫化CoMo催化剂上NO被H2 还原的规律 ,并考察了不同Mo含量的CoMo/Al2 O3 催化剂、单一的Mo/Al2 O3 和Co/Al2 O3 催化剂 ,以及原料气中H2 /NO比对反应活性和选择性的影响 .结果表明 ,硫化的 5 1%Co 15 2 %Mo/Al2 O3 催化剂具有最高的催化活性和选择性 ,在 2 0 0℃以下时反应产物为N2 O ,在 35 0℃以上时则完全转化为N2 .进一步增加Mo含量引起在 35 0～ 4 5 0℃间N2 选择性轻微下降 .提高原料气中的H2 含量可明显提高反应活性和N2 选择性 ,但当n(H2 ) /n(NO) >3后反应性能不再变化 .催化剂具有较高的稳定性 ,反应产物中始终未观察到有H2 S或SO2 产生 ,即反应未引起催化剂中的晶格S流失 .这说明H2

Catalytic reduction of NO by H 2 was carried out over sulfided CoMo/Al 2O 3 (with various molybdenum loadings), Co/Al 2O 3 and Mo/Al 2O 3 catalysts. The sulfided 5 1%Co 15 2%Mo/Al 2O 3 exhibited the highest activity and N 2 selectivity, at n (H 2) / n (NO) =1, NO was completely converted to N 2 above 350 ℃ while the product was only N 2O below 250 ℃. A slight decrease in N 2 selectivity was found above 350 ℃ for the catalysts with higher molybdenum loading (5 0%Co 20 6%Mo and 5 0%Co 25 1%Mo). Increasing n (H 2) / n (NO) to 3 led to complete conversion of NO to N 2 at 250 ℃. The stability test of sulfided CoMo/Al 2O 3 catalyst demonstrated that its activity remained high and stable over a period time as long as 5 h. Neither H 2S nor SO 2 was detected in the products, implying that no sulfur loss in the catalysts occurred during the reaction. These results suggested that the addition of H 2 to NO stream suppressed the deactivation of the sulfided catalysts induced by the oxidation of lattice sulfur in the catalysts. Obviously the reaction between O ad , formed from the dissociation of NO, and H ad to give H 2O occurred more easily than the following two reactions: lattice sulfur in the catalysts reacting with O ad to produce SO 2, or it reacting with H ad to produce H2S.