Complete Oxidation Of Formaldehyde At Room Temperature Over Zeolite Supported Pt Catalysts

Formaldehyde (HCHO) is one of the major components in indoor air pollutants, which are great threats to the human health and also the environment. Up to now, many techniques for the removing of HCHO have been well developed. Among them, completely catalytic oxidation HCHO at room temperature has been identified as one of the most efficient routes. Zeolite supported Pt has been proved to be one of the superior catalysts for catalytic removal of HCHO, due to the combination of the advantages of both noble metal and zeolite. Recently, it has been reported that zeolite-supported Pt catalysts are active for HCHO oxidation at low temperatures, but they are still unable to completely oxidized HCHO at room temperature. In this dissertation, a series of zeolite supported Pt catalysts have been successfully synthesized and tested in the catalytic oxidation HCHO at room temperature. What's more, the influences of zeolite's cation, Si/Al ratio and acidic density on the performance of catalysts have been carefully studied.This thesis mainly include introduction (chapter 1), experimental section (chapter 2), and results and discussion (chapters 3 and 4). In chapter 3, H-form of Al-rich Beta supported Pt catalyst (Pt/H-Beta-SDS) is very active for catalytic oxidation of HCHO, giving full conversion at room temperature (25 ?), which is much more active than a conventional H-Beta-supported Pt catalyst (Pt/H-Beta-TEA), giving the temperature for complete oxidation of HCHO at 45 ?. The higher activity of the Pt/H-Beta-SDS catalyst than that of the Pt/H-Beta-TEA catalyst is related to the advantages of higher Pt dispersion and higher adsorption of HCHO. Meanwhile, Pt/H-Beta-SDS also exhibits much higher catalytic activity than the Pt/Na-Beta-SDS and Pt/K-Beta-SDS catalysts. These results could be positively related to that Na-type and K-type catalysts would inhibit the conversion of formaldehyde into formate.In chapter 4, a series of ZSM-5 zeolite with different Si/Al ratios (60,100,300, and oo) and various cations (H*, Na+, and K*) supported Pt catalysts have been prepared by three different way:hydrothermal synthesis, ion-exchange, and impregnation. And we found out that both the zeolite's cation and Si/Al ratio strongly influence the activity of Pt/ZSM-5. Catalytic tests in HCHO catalytic oxidation show that Pt/ZSM-5-Si exhibits the highest activity, which proves that higher Si/Al ratios in the zeolites are helpful for improvement of zeolite hydrophobicity, which could enhance the adsorption ability of HCHO and accelerate the reaction product of water away from the catalytic system.In addition, these catalysts are very active and stable, which would be potentially useful for the removal of HCHO in the future.