Removal Of Printing VOCs By Catalytic O₃ Oxidation

Printing industry has become a key industry in China because of its large VOCs emissions.Toluene,ethyl acetate and butanone are the main VOCs representatives of printing industry and they not only endanger the natural environment,but also do harm to human health.At present,the technology of O3 catalytic oxidation is becoming more and more perfect,but the treatment of VOCs used in the printing industry is less.This paper will use the technology of O3 catalytic oxidation to degrade the toluene,ethyl acetate and butanone in the printed VOCs.In this paper,through the screening of the carrier and active components,it is determined that the supersaturated impregnation method is used to prepare the MnOx-CeOx-LaOx catalyst with ?-A12O3 as the carrier for the degradation of the printed VOCs.The results showed that the catalytic activity of the catalyst increased with the increase of the concentration of O3,and decreased with the increase of the concentration of VOCs.The removal rate and CO2 selectivity of toluene,ethyl acetate and butanone increased with the increase of O3 concentration,and decreased with the increase of VOCs concentration.The optimum conditions for determining the degradation of VOCs are air flow 4 L/min,temperature 20?,air velocity 5000 h-1,and O3 concentration 1500 mg/m3.The maximum removal rate of mixed waste gas of toluene,ethyl acetate and butanone with a concentration of 300 mg/m3 can reach 100%,and the highest selectivity of CO2 is 57.2%,61.8%and 54.7%respectively.The mixing process didn't have to significant effect to the removal rate of VOCs,but the selectivity of CO2 of each component decreased.Based on the above reaction products,the infrared spectrum was used to characterize the reaction mechanism.The results showed that the O*radicals and the·OH radicals produced in the reaction were the key to the degradation of VOCs.It was concluded that toluene was first oxidized to benzyl alcohol,benzaldehyde and benzoic acid,and then oxidized to alcohols,aldehydes and acids in low carbon chains;ethyl acetate first decomposed into acetaldehyde and acetic acid;butanone broke into formic acid,acetic acid and propionic acid.All the above intermediates can be oxidized to H2O and CO2.