Studies On Adsorption-Desorption/Catalytic Oxidation Of Absorbing Materials Under Microwave Radiation For Purification Of Toluene Vapor

Volatile organic compounds(VOCs)as the main air pollutants are dangerous to human health and environment.It is necessary to develop a novel treatment method that VOCs can be decomposed with the mode of high efficiency and low consumption,because of severe national and local standard.In the article,toluene as the reaction gas was chosen from typical representatives of VOCs.Microwave radiation was introduced into processes of adsorption-desorption and catalytic oxidation,which macroscopic temperatures of samples were accurately measured and controlled by a special thermocouple that microwave could be shielded.Firstly,effects of different initial condition and mathematical models on adsorption-desorption process of toluene vapor onto absorbent surface were investigated in detail under microwave radiation.A reaction mechanism about adsorption-desorption process of toluene vapor onto absorbent surface under microwave radiation was proposed tentatively.Secondly,variation laws of catalytic oxidation process of toluene vapor onto catalyst surface were studies under microwave radiation using catalysts of CoOx from coprecipitation and complexaion.Effects of microwave radiation and physicochemical properties of catalysts on activities were studied using CoOx.Nano-compoites were prepared successfully by the intervention in ultrasonic radiation and the doping of the celerium for further enhancing of catalytic activities.A reaction mechanism about catalytic oxidation process of toluene vapor onto catalyst surface under microwave radiation was proposed for realizing of efficient degradation of toluene at low temperatures.The main results of the article and regular rule are as follows:(1)The increase in the reaction rate of adsorption-desorption process and the decrease of adsorption time,adsorption capacity and desorption temperature were ascribed to the existence of microcosmic"Hot Spots"on the surface of activated carbon possessing large specific surface area under microwave radiation,which the temperature of certain micro-region of adsorbent surface was much higher than the macroscopic temperature.(2)The effect of adsorption-desorption processs on catalytic oxidation process was negligible under microwave radiation,if the temperature of catalytic reaction was set to above 120? using catalysts from activated carbon possessing large specific surface area or was set to above 50? using catalysts from CoOx possessing small specific surface area.(3)Amorphous nano-Co3O4 was synthesized very well under the mampel power rule,comparing with the most probable mechanism functions and the microtopography of samples,which led to the result that the precursor derived from precursor materials was solidified by high-temperature processing for the synthesis of nano-CoOx.(4)"Hot Spots"might also exist on the surface of Nano-and Bulk-Co3O4 in the catalytic oxidation of toluene vapor under microwave radiation by comparisons of activities in different external fields and catalytic activities of two samples were promoted by the effect of"Hot Spots".(5)Catalytic degradation of toluene vapor was promoted by the combination technology of microwave radiation and nano-Co3O4,which values of removal rate and mineralization rate were increased to 3.54 and 220.9 times,respectively,and reached 100%and 96%at 120? owing to smaller size distribution,richer species of Co2+(4.16)and Oiatt(1.13)and higher values of tan??(27%)and tan??(134%).(6)The intervention in ultrasonic radiation and the doping of the second activated element were beneficial to improve catalytic activities under microwave radiation and had advantages of good stability,cyclicity and water-resistance.The sample of 5%Ce-Co presented the best catalytic performance,which values of removal rate and mineralization rate were increased to 0.7 and 2 times once again and the value of minimum Ea was also obtained(33 kJ/mol).(7)The absorbing property was tentatively introduced into the catalytic oxidation of toluene under microwave radiation to construct the relationship between absorbing properties and catalytic activities and the catalytic activity of Ce-Co materials depended on the comprehensive consideration of physicochemical properties.Possible reaction pathways and mechanisms about efficient synergism purification at low temperatures of toluene vapor using microwave radiation and nano-composites were provided.