Investigation On The Catalytic Ozonation Behavior And Process For Chlorinated Volatile Organic Compounds

Chlorinated Organic Compounds（Cl–VOCs）as the main air pollutants are seriously harm to the environment and human health,which possess strong biotoxicity and are hard to be degradaded naturally.With the rapid development of the national industry,more and more Cl-VOCs was emitted.Therefore,exploit the efficient control method for Cl-VOCs is of great significance.This thesis based on the proven low temperature ozonation technique which has been widely applied in practical multiple flue gas pollutants removal,then put forward the efficient,stable,and complete degradation route of Cl-VOCs under low temperature by catalytic ozonation.The superiority of catalytic ozonation in Cl-VOCs degradation at low temperature was systematically evaluated.The interaction between Cl-VOCs catalytic ozonation performances and catalyst properties was further investigated.Besides,the interaction effects of complicated flus gas components on Cl-VOCs catalytic ozonation and byproducts formation were also considered.Initially,this thesis conducted catalytic ozonation and oxidation of chlorobenzene（CB）and dichloroethane（DCE）over three synthesized MnO₂ catalysts with different properties.Catalytic ozonation exhibited high efficiency with less catalyst dosage at low temperature,ca.30～120 ^oC,excellent stability,and less byproducts formation for both CB and DCE conversion（>90%）.Catalytic ozonation exhibited excellent stability with much fewer organic byproducts in effluent gas in the stability tests,and even H₂O had no effect on it,while catalytic oxidation of CB exhibited deactivation（from～98%to 35～55%）.In–situ DRIFTs measurements validated facilitated transformation of intermediates during catalytic ozonation.These findings comprehensively verify the superiority of catalytic ozonation to attain highly stable and complete degradation of Cl–VOCs at mild conditions,indicating its great potential in practical application.Secondly,this thesis synthesized bimetallic MnCoO_x catalysts for efficient synergistic ozonation of CB and NO with presence of complicated components in flue gas.Catalytic co-ozonation of CB/NO demonstrated that NO presence possessed negligible effects for CB conversion.But promoted mineralization rate increase,especially,the corresponding MAR for 50 ppm CB and 50/100 ppm NO co-ozonation near to 100%as O₃/CB exceeded 13.0.Which originate from the high valence intermediates of NO ozonation.Besides,the complicated components were introduced in to single CB catalytic ozonation and CB/NO catalytic co-ozonation.The results exhibited SO₂ and DCE introduction promoted CB ozonation and CB/NO co-ozonation,while H₂O,and benzene（Ph H）presence demonstrated opposite but not obvious tendency.These observations provided a significant brand-new insight for VOC catalytic ozonation under practical conditions.Finally,the investigation on catalytic ozonation of various Cl-VOCs（CB,DCE,dichloromethane（DCM）and trichloroethylene（TCE））over series of supported MnO_xcatalysts were conducted.Due to the great difference of Cl-VOCs molecule structures,catalytic ozonation performances exhibited obviously difference.The co-ozonation of mixed Cl-VOCs was conducted,results showed that the inhibited and synergistic effects were co-exsisted on each mixed Cl-VOCs.Thereafter,the temperature programmed desorption results of mixed Cl-VOCs proved the existence of competitive adsorption between molecules to some extent,but it did not play a decisive role.The difficulty of degradation of Cl-VOCs molecules was an important factor in the process of co-oxidation,which also verified the performances in the co-oxidation experiment.However,the inhibition could be weakened as the increase of O₃ input,and Cl-VOCs conversion could be recoverd to a high value.