Effect of Ce/Y Addition on Low-Temperature SCR Activity and SO2 and H2O Resistance of MnOx/ZrO2/MWCNTs Catalysts

Abstract:In this study, we proposed an innovative oxidation-absorption method for low-temperature denitrification (160-240 • C), in which NO is initially catalytically oxidized by hydrogen peroxide (H 2 O 2 ) vapor over titania-based catalysts, and the oxidation products are then absorbed by NaOH solution. The effects of flue gas temperature, molar H 2 O 2 /NO ratio, gas hourly space velocity (GHSV), and Fe substitution amounts of Fe/TiO 2 catalysts on the denitrification efficiency were investigated by a well-designed experiment. The results indicated that the Fe/TiO 2 catalyst exhibited a combination of remarkable activity and deep oxidation ability (NO converted into harmless NO 3 − ). In order to comprehend the functional mechanism of the Fe dopant's local environment in TiO 2 support, the promotional effect of the calcination temperature of Fe/TiO 2 on the denitration performance was also studied. A tentative synergetic mechanism could be interpreted from two aspects: (1) Fe 3+ as a substitute of Ti 4+ , leading to the formation of enriched oxygen vacancies at the surface, could significantly improve the adsorption efficiency of •OH; (2) the isolated surface Fe ion holds a strong adsorption affinity for NO, such that the adsorbed NO could be easily oxidized by the pre-formed •OH. This process offers a promising alternative for current denitrification technology.

Section: Effects Of Catalyst Typementioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Removal of NOX Using Hydrogen Peroxide Vapor over Fe/TiO2 Catalysts and an Absorption Technique

Chen

Zhao

et al. 2017

“…In this unit, the temperature of the flue gas entering the NH 3 -SCR reactor is below 160 • C. Although dust and SO 2 are previously removed, the H 2 O content in the flue gas still remains as high as 10 vol.%. Almost all current catalysts show low activity and poor water-resistance at this temperature [157,158]. Therefore, this technique is not practical for SIIs.…”

Section: Nh 3 -Scrmentioning

confidence: 99%

A Critical Review of Recent Progress and Perspective in Practical Denitration Application

Liu

et al. 2019

Nitrogen oxides (NO x ) represent one of the main sources of haze and pollution of the atmosphere as well as the causes of photochemical smog and acid rain. Furthermore, it poses a serious threat to human health. With the increasing emission of NO x , it is urgent to control NO x . According to the different mechanisms of NO x removal methods, this paper elaborated on the adsorption method represented by activated carbon adsorption, analyzed the oxidation method represented by Fenton oxidation, discussed the reduction method represented by selective catalytic reduction, and summarized the plasma method represented by plasma-modified catalyst to remove NO x . At the same time, the current research status and existing problems of different NO x removal technologies were revealed and the future development prospects were forecasted.Catalysts 2019, 9, 771 2 of 39 adsorption, oxidation, reduction, and plasma methods. In view of these attentive findings, adsorption method uses recyclable solid adsorbent material to adsorb NO x from flue gas through microporous structure, remarkably, environmentally friendly, no secondary pollution, and energy-saving and -efficient features make it stand out [18][19][20]. The oxidation process is a method that oxidizes NO into NO 2 or N 2 O 3 with high solubility under the action of an oxidant that is then absorbed by water or alkali solution. The process is simple and cost-saving, and is widely used in the wet flue gas denitrification process with relatively low cost and high removal efficiency of NO x ; except that the oxidized NO and SO 2 can be removed simultaneously to produce high value-added products [21][22][23]. The reduction method has the characteristics of high efficiency, cleanliness, and mildness; NO x removal can be realized at low temperature at present [24][25][26]. The plasma method is used to modify the surface of the catalyst, the dispersion of active species can be improved by plasma treatment, and the stability and low temperature activity of catalyst can be improved [27,28].Seldom, if ever, does a comprehensive article to introduce the current situation and treatment methods of removing NO x . In this paper, we tried to renovate, classify, and summarize the significant perspectives and most relevant findings reported in recent research articles and earlier reviews generalizing the mechanism analysis and research progress of NO x removal by adsorption, oxidation, reduction, and plasma methods, which can provide means for promoting the technological progress of pollution prevention, maintaining healthy development of factories continuously, studying the methods of removing NO x deeply, and mastering different technologies of removing NO x , as well as providing guidance for controlling the emission of NO x from motor vehicles such as diesel, gasoline, and so on. In order to improve the environmental quality and save the ecological environment, this paper further provides a convenient, low-cost, efficient, and economic guidance line.

“…Moreover, in iron containing SCR catalysts, the introduction of Mn could obviously enhance the low-temperature activity, probably due to the fact that synergistic effect between iron and manganese species [18]. It was reported that the MnFe/TiO 2 could improve the activity, stability and SO 2 durability of the SCR catalysts using NH 3 as the reducing agent [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Byproduct Analysis of SO2 Poisoning on NH3-SCR over MnFe/TiO2 Catalysts at Medium to Low Temperatures

Lee

Bai

2019

The byproducts of ammonia-selective catalytic reduction (NH3-SCR) process over MnFe/TiO2 catalysts under the conditions of both with and without SO2 poisoning were analyzed. In addition to the NH3-SCR reaction, the NH3 oxidation and the NO oxidation reactions were also evaluated at temperatures of 100–300 °C to clarify the reactions occurred during the SCR process. The results indicated that major byproducts for the NH3 oxidation and NO oxidation tests were N2O and NO2, respectively, and their concentrations increased as the reaction temperature increased. For the NH3-SCR test without the presence of SO2, it revealed that N2O was majorly from the NH3-SCR reaction instead of from NH3 oxidation reaction. The byproducts of N2O and NO2 for the NH3-SCR reaction also increased after increasing the reaction temperature, which caused the decreasing of N2-selectivity and NO consumption. For the NH3-SCR test with SO2 at 150 °C, there were two decay stages during SO2 poisoning. The first decay was due to a certain amount of NH3 preferably reacted with SO2 instead of with NO or O2. Then the catalysts were accumulated with metal sulfates and ammonium salts, which caused the second decay of NO conversion. The effluent N2O increased as poisoning time increased, which was majorly from oxidation of unreacted NH3. On the other hand, for the NH3-SCR test with SO2 at 300 °C, the NO conversion was not decreased after increasing the poisoning time, but the N2O byproduct concentration was high. However, the SO2 led to the formation of metal sulfates, which might inhibit NO oxidation reactions and cause the concentration of N2O gradually decreased as well as the N2-selectivity increased.