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Promotional Effect And Alkali-resistant Performance On Ce-Si Modified V2O5/TiO2Catalyst

Posted on:2016-07-18Degree:MasterType:Thesis
Country:ChinaCandidate:Q BaoFull Text:PDF
GTID:2181330467469847Subject:Thermal Engineering
Abstract/Summary:PDF Full Text Request
The selective catalytic reduction of NOx with NH3is the most efficient technology for abating NOx in flue gas at present. Catalysts are the core of SCR technology. Poisoning is inevitable for SCR catalysts in the actual application process. The key research point of the present work is study a novel catalyst with promotional effect as well as good alkali poisoning resistance. This work is important and meaningful.First, the optimal composition and the ability of alkali poisoning resistance on the new modified catalyst were studied. The optimal CeO2loading is10%and the optimal SiO2loading is0.3. The temperature window was extended to200-400℃, and within this temperature range, the average efficiency is18.6%higher than VTi catalyst before poisoning, the average efficiency is65.5%higher thanVTi catalyst after poisoning. Then the adaptability of gas hourly space velocity, the resistance to SO2and H2O, N2selectivity, stability and economy on modified catalyst were studied. Compared with conventional catalysts, the modified catalysts have a better adaptability and N2selectivity, meanwhile, a comparable stability, economy and resistance to SO2and H2O were observed,In addition, the main mechanism of alkali metal on catalyst was summarized. Alkali metal will preferentially adsorbed on V5+-OH which will reduce the adsorption of NH3on Bransted acid sites, the amount of Lewis acid sites also have a big decline as well as a drop of V reductibility, therefore, the overall activity is greatly declined. Moreover, the load of alkali metal reduces the chemisorbed oxygen concentration and the interaction between the carrier and the active ingredient which also cause a drop in reaction activity.Third, the main mechanism of the Ce-Si modified catalyst was summarized. The introduction of Ce and Si can increase the total pore volume and form smaller particle size and rich surface area which are conducive to the reaction. After the introduction of Ce and Si catalyst, a rich Bronsted acid sites (V5+-OH) and Lewis acid sites (V5+=O) were formed on the catalyst and greatly improved the catalyst activity. At the same time, the introduction of Ce and Si improve the chemisorbed oxygen concentration and the interaction between the carrier and the active ingredient, therefore, the activity on adsorption sites and reduction sites were enhaced. These factors above are the reason that the modified catalyst can largely improve the activity as well as the alkali poisoning resistance ability.
Keywords/Search Tags:selective catalytic reduction, V2O5/TiO2, SiO2, CeO2, alkali metalpoisoning
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