INFLUENCE OF PRE-ADSORBED SULPHUR DIOXIDE AND WATER VAPOR ON THE PROTECTIVE PROPERTIES OF A COPPER-PALLADIUM CATALYST FOR CARBON MONOXIDE OXIDATION

It is known that the largest sources of sulfur dioxide (SO2) and carbon monoxide (CO) emissions into the atmosphere are the thermal power industry, ferrous and non-ferrous metallurgy, and the chemical industry. The presence of gaseous toxicants in the working area in concentrations that far exceed the MPC (20 mg/m3 for CO and 10 mg/m3 for SO2) acutely raises the issue of personnel respiratory protection. This necessitates the use of personal respiratory protective equipment (RPE) by workers equipped with filters that protect against both substances. We have developed a highly efficient low-temperature catalyst in which the carrier is hydrothermally modified dispersed silica tripoli (Н2О-Tr(К-І)). For such a catalyst, there are no studies on the influence of catalytic poisons, namely SO2 and H2O, on its activity in the reaction of low-temperature oxidation of CO with air oxygen. The work investigated the adsorption properties of hydrothermally modified dispersed silica trefoil and the carbon monoxide oxidation catalyst Pd(II)-Cu(II)/Н2О-Tr(К-І) with respect to water vapor and sulfur dioxide, as well as their effect on the protective properties of the catalyst. Analysis of water vapor adsorption-desorption isotherms by samples of natural and chemically modified tripoli allows us to attribute them to sorbents with a heterogeneous porous structure with a predominance of transitional pores. The effect of the additional water content on the activity of the Pd(II)-Cu(II)/Н2О-Tr(К-І) catalyst for carbon monoxide oxidation was investigated. It was established that with an increase in the water content, the degree of CO conversion decreases due to blocking of the active centers of the catalyst, or capillary condensation, which affects the internal diffusion processes. The adsorption properties of natural and chemically modified tripoli at low temperatures from a gas-air mixture in which the SO2 content was 150 mg/m3 were analyzed. It was found that the protective action time increases from 15 min for H2O-Tr(K-I) and up to 250 min for the Pd(II)-Cu(II)/H2O-Tr(K-I) catalyst, which indicates the participation of Pd(II) and Cu(II) in the reaction with sulfur dioxide. It was found that the copper-palladium catalyst, previously poisoned with sulfur dioxide, loses catalytic activity in the oxidation reaction of carbon monoxide as a result of the irreversible binding of part of palladium(II) with sulfur dioxide and its loss of the ability to coordinate and activate the CO molecule. Therefore, to prevent catalyst poisoning when using it in respiratory protection against carbon monoxide, it is necessary to provide for preliminary air purification from aerosol particles, sulfur dioxide, and water vapor.