The Study Of Adsorption And Low Temperature Catalytic Oxidation Of Toluene On MnO_X-CeO₂/Honeycomb Zeolite

Urban air qualities, especially the local environmental air quality, have attracted moreand more attention with the sustainable development of economic and the acceleration ofurbanization in our country. Volatile Organic Compounds （VOCs） is one kind of this complexorganic composition of air pollutants which exists universally both indoor and outdoor, andhave a direct impact on people’ health and life safety. At present, the purification method ofVOCs is mainly based on adsorption and catalytic oxidation, but there are severaldeficiencies in single adsorption or catalytic oxidation technology. Adsorption-catalyticoxidation integration technology is will to have high adsorption capacity of porous adsorptionmaterials and high catalytic effect of heat catalytic materials combined, on the one hand,through the adsorption action of the porous material can provide high concentration pollutionenvironment for the catalyst activity of thermal catalytic reaction; on the other hand, it canrealize in situ desorption regeneration of adsorbent by thermal catalysis, making theseparation of catalyst more easier, and in the further to realize the catalyst working steadily inthe adsorption-catalytic oxidation cycles. Thus, it provides the basis research for thedecontamination of VOCs which are adsorbed in the normal temperature and catalyzed at alow temperature.In this work, the porous molecular sieve with a large adsorption capacity was selected asthe supporter. We prepared the manganese cerium complex by sol-gel method, and loadedmanganese cerium metal oxide to the supported by the dipping method. The catalyticoxidation activity was tested by GC and characterized by BET, SEM, TPR, TPD, XPS, etc.The main conclusions are as follows:（1） The series of MnOX（Z）-CeO₂catalyst prepared by sol-gel method has a significantcatalytic oxidation activity for toluene at low temperature, and in which a Z （atomic ratio）in0.4⁰.6intermediate range showed a higher efficiency relatively, the light-off temperaturecan be reduced to125℃and the complete transformation temperature can be decreased to189℃（at the conditions: volume air speed at10000h-1, toluene concentration at100ppm）.All kinds of the characterization show that the efficient low temperature catalytic activity ofMnOX-CeO₂are due to its large surface area, manganese oxides with high oxidation statesform and rich reactive oxygen species.（2） MnOX-CeO₂/honeycomb zeolite showed a high capability of adsorption at normaltemperature and excellent catalytic oxidation activity at low temperature of toluene in lowconcentration and large volume. In the10000-30000h-1of space velocity, the catalyst still can maintain a conversion of90%for toluene in325℃; What’s more, the catalyst’s thermalstability was tested for30hours at the temperature of275℃, resulting in the conversion oftoluene had been sustainable above90%and the selectivity CO2was more than85%. Finally,we made an on-the-spot investigation on the life of catalyst in the adsorption-catalyticoxidation cycles, and the results showed that after five times adsorption-catalytic oxidationcycles, the capability of adsorption of the catalyst was kept at99.5mg/g, but the conversion oftoluene and the selectivity of CO2were maintained above85%and80%, which provedMnO_X-CeO2/honeycomb zeolite can realize low temperature regeneration effectively andcontinuous operation.