Effects of Cu/Al Mass Ratio and Hydrothermal Aging Temperature on Catalytic Performance of Cu/SAPO-18 for the NH3-SCR of NO in Simulated Diesel Exhaust

Abstract

The Cu/SAPO-18 samples with different Cu/Al mass ratios were prepared, their catalytic activities for the NH3-SCR of NO in simulated diesel exhaust were evaluated, and effects of Cu/Al mass ratio and hydrothermal aging temperature on catalytic performance of Cu/SAPO-18 was examined. Physicochemical properties of the samples were characterized by means of various techniques. It is found that the activity of the sample changed with a rise in Cu/Al mass ratio, with the highest overall activity being achieved over the sample with a Cu/Al mass ratio of 0.045. The H2-TPR results indicate that the Cu/Al mass ratio could affect the distribution of Cu species, and the Cu/SAPO-18-0.045 sample possessed the highest amount of the isolated Cu2+ species. BET and XRD results reveal that the Cu/Al mass ratio exerted little effect on the structure of the sample. Low-temperature hydrothermal treatment had the least influence on the sample, and the effect of high-temperature hydrothermal treatment on the sample became increasingly obvious with a rise in hydrothermal treatment temperature. It is concluded that the hydrothermal aging treatment mainly affected the sample by destroying the structure, blocking the pores, migration and transformation of the Cu species, and changing the acidic sites of the sample.