Study On Non-Thermal Plasma-Assisted Catalysis For Carbon Monoxide Oxidation

Carbon monoxide is a kind of poisonous and harmful gas, the indoor pollution control problem has been paid much more attention. Many technologies have been developed for removal of carbon monoxide from the indoor air, in which carbon monoxide catalytic oxidation technologies are included. However, most of thesecatalysts have problems of deactivation in some special environmental conditions. Non-thermal plasma (NTP, also called cold plasmas) combined with catalytic technology is a promising technology for VOCs treatment, but the plasma treatment of VOCs leads to the formation of non-desired by-products such as carbon monoxide, which becomes the technical bottleneck to further development of the plasma hybrid with the catalysts.This report aimed to eliminate carbon monoxide formed in the VOCs decomposition using plasma and improved the catalytic stability. The carbon monoxide oxidation over non-thermal plasma-driven catalysts was studied. The synergetic effect between NTP and catalysts was observed under lower carbon monoxide concentration. The effects of carbon monoxide initial concentration、gas flow rate、water concentration on carbon monoxide conversion were also studied.The results are as follows:1) The combined application of plasma and catalysts showed different synergetic effects for carbon monoxide oxidation, Hopcalite and Au/y-Al2O3combined systems have an enhancement effect, but the PdCl2-CuCl2/γ-Al2O3combined system has weaken effect. It was shown that the carbon monoxide conversion increased when the Special Energy Density(SED) increased.2) In Hopcalite combined system, the carbon monoxide conversion increases up to98%when the SED is261J/L.The carbon monoxide initial concentration、gas flow rate、water concentration are proved to be obviously affected on the performance of carbon monoxide elimination over the synergetic system with low SED, but hardly affected on carbon monoxide elimination performance with high SED.3) The NOx formation in the process of NTP discharge is investigated. In NTP alone system, the nitrogen oxide concentration in the outlet is low; adding catalysts increases the nitrogen oxide concentration obviously, the nitrogen oxide concentration increases with the increasing SED. When SED is261J/L, adding water increases the concentration of nitrogen oxide.4) The ozone formation in the process of NTP discharge is investigated, furthermore In NTP alone system and γ-Al2O3combined system, the ozone concentration increases when SED is lower than150J/L, and drops when SED is higher than150J/L; in catalysts combined system, the ozone concentration is low, which is reduced to non-detectable levels in Hopcalite combined system.The poison resistance to chlorine in Hopcalite combined system is investigated. It was showed that Hopcalite combined system do not have good chlorine resistance. Adding Na2CO3/Al2O3catalyst to the combined system can prolong the breakthrough time,but not avoid the deactivation of the Hopcalite.Hopcalite supported on the honeycomb ceramic is prepared by composite processing, and effects of boiling time、Hopcalite rations、calcination time、 addition of urea are investigated. The experimental results indicate that the optimal impregnation time is4h; the optimal Hopcalite rations is80%; the optimal calcination time is12h and addition of urea. In this condition the catalyst have best catalytic performance of oxidation of carbon monoxide.