Research On Low Temperature Denitration Performance Of ZSM-5/USY Composite Molecular Sieve Catalyst

The NH₃-SCR denitrification process is one of the most widespread and effective methods for removing NO_X.Vanadium based denitrification catalysts are mainly used in the high-temperature and high dust stage,where the process conditions are relatively harsh,the flue gas flow rate is high,and the smoke and dust content is high.Vanadium based catalysts are susceptible to the influence of dust particles and SO₂ in the flue gas,and the metal element vanadium carried in the catalyst has certain biological toxicity and is easy to volatilize,making it difficult to regenerate deactivated catalysts.Therefore,catalysts that can efficiently denitrification,have better SO₂ resistance,and are easy to regenerate under low temperature conditions have received widespread attention.This article uses ZSM-5/USY composite molecular sieve as the catalyst carrier,and loads different ratios of Cu O,Ce O₂,and Zr O₂ as the active components.The denitrification performance,sulfur resistance performance,regeneration performance,and economic evaluation of the catalyst were compared and analyzed.At the same time,the catalyst performance was investigated by characterizing and analyzing the specific surface area,pore volume,pore size,and component crystal properties of the catalyst.The research conclusion is as follows:The optimal mass ratio of ZSM-5 molecular sieve and USY molecular sieve is 1:3,the optimal calcination temperature is 550℃,the optimal calcination time is 5 hours,and the ZSM-5/USY composite molecular sieve is loaded with 3 wt.%In the case of Cu,the denitrification efficiency at 200℃is 69.04%.Under experimental conditions of 6%O₂,0.1%NO,0.1%NH₃,high-purity N₂ as equilibrium gas,space velocity of 12000 h^-1,and reaction temperature of 200℃,the denitrification efficiency of the 5Cu/ZSM-5-USY catalyst is 70.13%;The denitrification efficiency of the 5Cu-3Ce/ZSM-5-USY catalyst is75.95%;The denitrification efficiency of the 5Cu-3Ce-3Zr/ZSM-5-USY catalyst is87.93%.After introducing SO₂,the denitrification efficiency of the 5Cu/ZSM-5-USY catalyst decreased from about 68%to 28.23%;The denitrification efficiency of the 5Cu-3Ce/ZSM-5-USY catalyst decreased from about 72%to 51.84%;The denitrification efficiency of the 5Cu-3Ce-3Zr/ZSM-5-USY catalyst decreased from about 85%to52.97%.The sulfur resistance performance of single Cu based catalysts is relatively not good enough.In a gas atmosphere with SO₂ present,the sulfur resistance performance of Cu Ce double active centers is better than that of single Cu based catalysts.Mainly attributed to the easier adsorption of SO₂on Ce to form sulfates,thereby protecting Cu O_X,and the fact that Ce can reduce NH₄⁺and SO₄^2-The binding energy between leads to the decomposition of ammonium sulfate.The loading of Zr can slightly improve the sulfur resistance of the composite molecular sieve with Zr O_X.The 5Cu-3Ce-3Zr/ZSM-5-USY catalyst after SO₂ poisoning was regenerated using a mixed solution ultrasonic cleaning and pyrolysis method.It was found that the denitrification efficiency of the catalyst increased from 59.73%to 73.13%,but it was still less than 87.93%of the fresh catalyst.Based on economic evaluation and analysis,the5Cu-3Ce-3Zr/ZSM-5-USY catalyst has a low comprehensive cost and price,excellent low-temperature denitrification and sulfur resistance performance,and good application prospects.