| With the rapid development of printing and packaging industrialization,the emission of volatile organic compounds(VOCs)is increasing year by year,which seriously affects the air quality and people’s health.Microwave catalytic combustion is considered to be an effective method to control VOCs emission,and microwave heating can replace traditional electric heating in the catalytic combustion of VOCs.Microwave heating is rapid,only selective to absorbing catalysts and low energy consumption.However,VOCs is oxidized incompletely with low temperatures,which will cause secondary pollution.Therefore,researching for mineralization and degradation mechanism of catalytic combustion at low temperature is essential to control industrial VOCs Pollution.The precious metal and transition metal composite catalyst has good low-temperature catalytic activity.In this paper,a dual-active-site Pt-Cu Mn Ce O_x/monolithic honeycomb nano-ceramic catalyst was prepared by incipient-wetness impregnation method.The catalytic performance and mineralization effect of the catalyst for VOCs toluene and acetone under microwave heating were investigated;Furthermore,the effect of increasing the inlet temperature on the mineralization was analyzed,and the reaction route and mechanism of toluene and acetone were explored.The catalysts were characterized by SEM,XRD,BET and XPS,and the following research results were obtained on the basis of research work:(1)When the microwave power was increased from 600 W to 1000 W,the degradation rate of toluene increased from 88%to 99%during 150 minutes reaction,and the degradation rate of acetone improved from 80%to 88%.The increase of microwave power can improve the efficiency of microwave catalytic oxidation degradation of VOCs.When the microwave power was 600W and the bed temperature reached 300°C,the mineralization rate of the mixed components arrived 82%.(2)According to XRD and XPS characterization,the active component particles were highly dispersed and uniformly distributed on the surface of the catalyst and most of these particles were amorphous.Highly dispersed Pt particles and copper-manganese-cerium spinel active components improved the low-temperature catalytic efficiency for p-toluene and acetone under"microwave hot spots"effect.Seven repetitive experiments with total 1400 minutes confirmed that the catalytic activity of Pt-Cu Mn Ce O_x/nano-ceramic catalyst for toluene and acetone was kept at stable.(3)On the basis of the original experimental device,silicon carbide rods were added to increase the intake air temperature,and the catalytic oxidation effect and mineralization rate of VOCs in the three cases were investigated.The sequence was:Adding four solid silicon carbide rods>no Adding silicon carbide rods>Adding four hollow silicon carbide rods.The catalyst could quickly heat up due to its own favorable microwave-absorbing performance after four solid silicon-carbon rods were added to the experimental device.At the same time,the intake temperature of toluene and acetone exhaust gas was preheated,which shortens the degradation time of waste gas.(4)GC-MS/MS test results showed that the main degradation pathway of toluene could be speculated to be:toluene→benzaldehyde→benzoic acid→small molecule acid→carbon dioxide and water.The main degradation pathway of acetone could be:acetone→aldehydes,acids→carbon dioxide and water.The microwave catalytic combustion reaction both followed the L-H and Mv K oxidative mechanisms,and lattice oxygen and surface adsorbed oxygen participated in the activation oxidation process simultaneously to enhance the adsorption and oxidation of VOCs molecules.The results show that the prepared Pt-Cu Mn Ce O_x/honeycomb nano-ceramic catalyst has an excellent degradation effect and mineralization performance for toluene and acetone.This paper studies the mineralization degradation pathway of toluene and acetone,which provides technical and theoretical support for the complete mineralization degradation of VOCs in the printing and packaging industry. |
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