NO catalytic oxidation over pure-silica zeolite-β

Key words: 
• pure-silica zeolite-β /
• NO oxidation /
• low temperature /
• hydrophobic

Abstract: It is very important to improve the performance of catalysts for NO oxidation in the industrial NOx waste gas treatment. The commonly used catalysts are not vapor-proofing and have high active temperature. In this study, puresilica zeolite-β was used as the NO oxidation catalyst due to its hydrophobicity. At constant inlet NO and O2 concentrations (0.05% and 20.7%, respectively, vol), the effects of various operating conditions on the NO catalytic oxidation conversion were investigated. The reaction conditions investigated included the reaction temperatures (20℃ to 60℃), the relative humidity (0% to 100%), and the space velocity (360 h-1～20 000 h-1) over puresilica zeolite-β. The results showed that the NO oxidation conversion decreased significantly with the increasing of the reaction temperature, for both dry and wet NOx gas. Thus, low temperature was favorable for NO catalytic oxidation. At 20℃ and space velocity of 20 000 h-1, NO oxidation conversion decreased from 49% to 34% when the relative humidity increased from 0% to 100%. The increase in the reaction temperature reduced the inhibition of the NO catalytic oxidation due to high relative humidity. The results of 240 h stability test at 30℃ demonstrated that, with an space velocity of 7 200 h-1, the NO oxidation conversion reached 67% and 56% when the relative humidity of the feed gas was 0% and 100%, respectively. The results indicated that the pure-silica zeolite-β catalyst had high catalytic stability in the saturated wet gas for NO oxidation.