Carbon Nanodot Modified Catalyst On Microwave Assisted Catalytic Oxidation Of Gaseous Toluene

At present, the industry has developed rapidly in our country and the air pollutionis serious. So we are paying much attention to volatile organic compounds which is theprecursor of PM2.5,including many poisonous and harmful material such as benzenecontent. The catalytic oxidation technology which dealing with toluene waste gas fastand efficiently is a way to adsorb toluene on catalyst surface and some REDOX reactionoccurred to remove pollutants. Catalyst with good adsorption performance caneffectively increase the retention time of toluene for the removing of toluene. Combinedwith microwave heating which is fast, efficient and selective, the catalysis process oftoluene waste gas can improve the efficiency of catalytic oxidation by reducing thecatalytic reactivity. Thus the good MW-absorbing ability became much more importantfor catalysts. The study found that carbon nanodots as a new type of nano carbonmaterials,which has the good physical, chemical and optical properties, can prepared bya range of raw material with a simple method, indicating its wide application prospectssuch as catalysis. But, there are few researches on carbon nanodots modified metal loadtype catalyst. Therefore, researches on how to modified catalyst for improving theadsorption and MW-absorbing performance is significant for the microwave assistedcatalytic oxidation process. In this study, carbon nanodots (CNDs) with the sizes of2-7nm and blue fluorescence were firstly synthesized by hydrothermal treatment of naturalbiomass (dead leaves of plane tree). The transmission electron microscopy (TEM),three-dimensional fluorescence excitation-emission matrix analysis (EEM), Fourierinfrared transform spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS) weretaken to analyze the chemical and physical properties of carbon nanodots. In ourexperiment, After that, three different ways was taken to modified Cu-Mn-Ce-5A supported catalysts. And microwave heating test, toluene gas adsorption and catalyticoxidation experiment of the three kinds of catalysts were carried out. Around the abovecontents,, there are some extended jobs.1. The best quantity was determined by testingtoluene adsorption and MW-absorbing ability of the CNDs modified5A molecular sievewith different CNDs concentration. And we determined the calcination temperature inthe same research method too. Then, using the CNDs modified5A molecular sieve asthe carrier for Cu-Mn-Ce catalysts (CMC-CNDsZ). Through the catalyst performancetest and the low temperature catalytic oxidation experiment of toluene gas, we foundthat the adsorption performance of the modified catalysts has improved. But theMW-absorbing performance is poor. The catalytic oxidation of toluene under lowtemperature increased slightly compared with traditional Cu-Mn-Ce-5A catalyst, andthe stability has the certain enhancement.2.The catalysts were modified by mixing theCNDs and Cu-Mn-Ce impregnation liquid, using the same CNDs concentration andcalcination temperature (CMCCNDs-Z). Relevant test results show that the adsorptionperformance of the modified catalysts has improved significantly, But theMW-absorbing performance is poor too. The catalytic oxidation of toluene under lowtemperature was same as the traditional Cu-Mn-Ce-5A catalyst.3.CNDs were used tomodify Cu-Mn-Ce-5A catalysts without high-temperature roasting, which namedCNDs-CMCZ. Relevant tests show that the CNDs-CMCZ catalyst has good tolueneadsorption and MW-absorbing performance. Owing to these advantages,75%ofgaseous toluene was degraded within80min at150°C using CNDs-CMCZ catalyst,which was almost1.9times of that using unmodified catalyst. And the catalytic processhas certain stability.4. Based on the above experiments, Test using the best modifyingmethods modified the Cu-Mn-Ce-Al2O3catalyst, which showed that the modifiedmethod can improve adsorption performance and MW-absorbing performance in thedifferent carrier. As a result, this way of modification proved to be feasible. Furthermore,EDS, BET characterization and oxidation production analysis on the GC-MS ofCNDs-CMCZ and CMC-Z catalysts shows that, The CNDs not only increased thecarbon content on the surface of the catalyst to improve the MW-absorbing capacity, butalso made the catalyst have larger specific surface area and smaller pore diameter,which promoted effectively the adsorption of toluene and maintained better adsorption time, also generate enough active sites, which ensuring the catalytic oxidation reactioncan be carried out highly efficient and stable. The economic analysis proves that themodified catalyst can be used in microwave assisted catalytic oxidation process forimproving the utilization ratio of microwave to lower energy consumption and enhancethe catalytic oxidation reaction effect, Which has a certain application prospect.