Research On Formaldehyde Degradation In Bipolar High Voltage Pulse Dielectric Barrier Discharge Combined With Catalyst

In recent years,with the improvement of people's environmental awareness,air quality is getting more and more attention,especially in indoor air quality.The indoor air pollution is more and more serious with the use of a variety of building decoration materials.Formaldehyde is listed as the primary indoor air pollutants because of great toxicity,long duration,wide range of pollution.Formaldehyde has posed a great threat on people's physical and mental health and living environment.Therefore,to study how to degrade formaldehyde efficiently has a very important meaning and value.Discharge plasma technology combined with catalytic technology developed in recent years have short processing time,high efficiency advantages in the application of formaldehyde degradation.But how to improve the formaldehyde degradation rate in the same time control the generation amount of byproducts,require further study.In this paper,formaldehyde as treatment object in the experiment.Coaxial dielectric barrier reactor was powered by dual positive and negative high voltage pulse power.First the experiment systematic studied pulse voltage,pulse repetition frequency,discharge gap,gas flow and the initial concentration influence on formaldehyde degradation rate and ozone generation.Then screening of the carrier and active component of catalyst.Used 5A molecular sieve as carrier,rare earth elements La,Ce as additives modified ingredients,prepared two catalysts La-Mn/5A molecular sieve catalyst and Ce-Mn/5A molecular sieve catalyst which were characterized and analyzed by SEM methods.Finally,the experiment in-depth study the effect of the dielectric barrier discharge plasma cooperated with different types of catalysts on formaldehyde degradation rate and ozone generation.The experiment results showed that elevated pulse voltage was beneficial to the formaldehyde degradation,when voltage reached 19 kV,continued to increase voltage,growth of formaldehyde degradation rate had shrunk,while ozone generation grew with the increase of voltage.Degradation rate increased with the decreased of discharge gap,but discharge gap too small would lead to excessive ozone generation.As the flow increased,formaldehyde degradation rate decreased.The pulse repetition frequency increased,formaldehyde degradation rate increased,when the pulse repetition frequency was 60 Hz,continue to increase the pulse repetition frequency,the increase of degradation rate was not obvious.Under certain experimental conditions,the greater initial concentration,the lower degradation rate,while the amount of formaldehyde degradation increased and close to the maximum capacity of the reactor.5A molecular sieve as carrier loading 8%Mn catalyst had better effect on formaldehyde degradation combined with plasma,when the pulse voltage was 22 kV,the pulse frequency was 60 Hz,the gas flow rate was 0.5L/min,formaldehyde degradation rate was 92.1%,ozone generation was 40.3mg/m3.La-Mn/5A molecular sieve catalyst and Ce-Mn/5A molecular sieve catalyst had significantly higher catalytic effect than Mn/5A molecular sieve catalyst.3%Ce-Mn/5A molecular sieve catalyst had the optimum catalytic effect with dielectric barrier discharge plasma,formaldehyde degradation rate was as high as 99.2%,ozone generation was only 38.9 mg/m3.The study also analyzed the mechanism of formaldehyde degradation in separate discharge plasma and discharge plasma combined with catalyst,it can provide a certain theory reference for polluting gases degradation by discharge plasma combined with catalyst.