疏水型H-ZSM-5分子筛上NO氧化反应的研究

NO oxidation over hydrophobic H-ZSM-5 molecular sieves

针对NO低温氧化催化剂的抗水汽性差的问题,以疏水型高硅H-ZSM-5分子筛为NO氧化催化剂,在温度为10-90℃、NO进口浓度为0.05%-0.08%,及相对湿度为0-100%条件下,考察了NO的氧化反应.结果表明,H-ZSM-5分子筛的硅铝比由50提高至300时,湿气条件（水汽含量1.18%）下,NO氧化率由20%升高至56%;干气下,低温有利于NO氧化;湿气下（水汽含量1.18%）,NO氧化率随着温度的升高先增加后减少,最佳反应温度为20℃,与NOx工业废气的排放温度相近.200h的稳定性试验结果显示,在30℃、NO进口浓度0.08%、空时0.5s、保持相对湿度为50%或100%时,NO氧化率可维持在60%和50%,催化剂具有良好的稳定性.

Based on the principle that molecular sieve ZSM-5 can be highly hydrophobic by using a high Si/Al2 ratio, a silica rich H-ZSM-5 was used as the NO oxidation catalyst and its catalytic activity under various reaction conditions was investigated： relative humidity from 0 to 100%, reaction temperature from 10 to 90℃, and inlet NO concentration from 0.05% to 0.08%. H-ZSM-5 catalyzed NO oxidation efficiently in the presence of vapor. When the Si/Al2 ratio of H-ZSM-5 increased from 50 to 300, the steady-state NO oxidation conversion in wet NOx gas （H2O concentration was 1.18%） raised from 20% to 56%. The oxidation conversion in dry gas decreased monotonously as reaction temperature increased, and low temperature was favorable for NO oxidation. In wet gas （H2O concentration was 1.18%） the optimal reaction temperature for NO oxidation was 20℃, which was close to the temperature of NOx in exhaust gas. The NO conversion decreased when temperature was below or above. A 200h stability test was conducted at 30℃, with an inlet NO concentration of 0.08% and a space time of 0.5s. The NO oxidation conversion reached to 60% and 50%, when the relative humidity was 50% and 100%, respectively. ZSM-5 catalyst displayed high stability in saturated wet gas and it converted the waste gas into an optimum composition for alkali absorption of NOx.