Study On Sulfur And Water Resistance Of Metal Oxide Modified In/HBEA For Selective Catalytic Reduction Of NOx With Methane

CH₄ has abundant reserves and is cheap and easy to obtain.CH₄-SCR is a promising alternative to NH₃-SCR NOx removal technology.In/HBEA is one of the more active in the CH₄-SCR denitration catalyst,but In/HBEA has poor sulfur and water resistance and is severely deactivated under sulfur-containing water conditions.In practical applications,the flue gas often contains a certain concentration of water and sulfur dioxide.Therefore,improving the In/HBEA sulfur and water resistance is the key to applying the catalyst to the actual situation.This paper intends to systematically study the sulfur and water resistance of metal oxide modified In/HBEA to optimize its preparation and reaction conditions,and to explain its mechanism of improving sulfur and water resistance.The specific contents include:The addition of one,two and three metal oxides?16 metal oxides such as Ga₂O₃,Ta₂O₅,CeO₂,etc.?to In/HBEA was carried out,and the results showed that the double metal oxidation The modification of the material is better than that of the single metal oxide;sulfur and water resistance of triple metal oxide modified In/HBEA is slightly better than that of the double metal oxide modified In/HBEA.The catalyst with the best sulfur and water resistance is In-Co₃O₄-Ga₂O₃/HBEA,and the NOx removal rate at625 °C is up to 74.6 %.The preparation conditions and reaction conditions of In-Co₃O₄-Ga₂O₃/HBEA were optimized.The optimal preparation method was as follows:the concentration of In was0.033 M,and the mass ratio of metal oxide to molecular sieve For 10:40,the mass ratio of Co₃O₄ to Ga₂O₃ is 4:1,and the calcination temperature is 500 °C.In the optimization of reaction conditions,it was found that the removal rate of NOx by In-Co₃O₄-Ga₂O₃/HBEA under sulfur and water-containing conditions increased first,then decreased with the increasing of NOx and O₂ concentration.With.the concentration ratio of CH₄ and NOx increasing and increasing as the space velocity decreases.An increase in the concentration of SO₂ and H₂O causes a decrease in the activity of the catalyst,and the effect of SO₂ on it is greater than that of H₂O.The addition of Co₃O₄ and Ga₂O₃ can greatly improve sulfur and water resistance of In/HBEA.The mechanism of sulfur and water resistance of catalyst In-Co₃O₄-Ga₂O₃/HBEA was studied.In the sulfur-containing water condition,SO₂ andNO will have competitive adsorption at the Bronsted acid site,but Ga₂O₃ provides more adsorption and reactive sites for NO.Co₃O₄ greatly improves the redox of In/HBEA,which is CH₄.An activation site is provided,and the activated CH₄ can further form a carbon-containing intermediate such as R-CHO and R-COOH at?InO?⁺.The resulting carbon-containing intermediate product not only reacts with nitrates and nitrite intermediates to form N₂,CO₂,etc.but also reacts with NO and SO₂ on Co₃O₄ to form a final product.