Different exposed crystal surface CeO2 catalysts (nanopolyhedrons and nanocubes) are synthesized and treated by NH3 to investigate the effect of oxygen vacancies on improving NO oxidation for fast SCR reaction. The experiment results show that N-CeO2-NPs catalyst (treated by NH3) has the most oxygen vacancies of the four catalysts, thus leading to the best oxidation activity of NO, which further promotes the fast SCR reaction. From the XPS and Raman spectra results, it indicates that the more oxygen vacancies are due to the higher concentration of Ce3+ and surface adsorbed oxygen resulting from the NH3 treatment at high temperature. Meanwhile, the test of NO conversion to NO2 shows that the rich oxygen vacancies promote the conversion of NO to NO2, in which N-CeO2-NPs catalyst yields more remarkable promotion of NO oxidation to NO2, respectively. Also, the magnitude of the variety is in accordance with that of the oxygen vacancy content and concentration of Ce3+ ions. Thus, CeO2 with NH3 treatment is found to significantly enhance its NH3-SCR performance which leads to higher NOx removal efficiency of N-CeO2-NPs catalyst with {111} exposed crystal surface.

CeO2 nanorods (CeO2-NRs) catalyst was prepared and treated with ammonia (NH3) gas and the effect of NH3 treatment on CeO2 nanorods catalyst was also studied for improving NH3-SCR of NO. And the catalysts were tested for NH3-SCR of NO during 100-450 degrees C. The results showed that NH3 treatment could improve the De-NO efficiency of the catalyst, which increased evidently in the range of about 160-410 degrees C. XPS results revealed that NH3 treatment made CeO2-NRs catalyst produce more Ce3+ on its surface, and thereby produced more oxygen vacancies and further promoted SCR reaction. The XRD and H-2-TPR characterization test results indicated that CeO2 catalyst with NH3 treatment could destroy its crystallinity and enhance the reducibility. In addition, the in situ DRIFTS results also exhibited more activity functional groups on the surface of N-CeO2-NRs catalyst than that of CeO2-NRs catalyst.

Zinc salts and SO2 would cause Mn-Ce/AC catalyst poisoning, reducing the service life of the catalyst. In this study, the effects of Nb2O5 on the tolerance of ZnCl2 and SO2 over Mn-Ce/AC catalyst were studied by the characterization results of BET, SEM, XRD, H-2-TPR, NH3-TPD, TG and XPS. It indicated that doping Nb2O5 could effectively enhance the SCR performance and N-2 selectivity of Zn-Mn-Ce/AC catalyst. Meanwhile, Nb2O5 could significantly improve the SO2 poisoning resistance of Zn-Mn-Ce/AC catalyst when sulfur dioxide was added into the reaction system. Nb2O5 could react with SO2 in a preferential way to restrain the sulfuration of manganese and cerium oxides on the catalyst. More importantly, Nb2O5 reacted with SO2 to form Nb sulfate and then formed a new acidic site on the Zn-Mn-Ce/AC catalyst surface, which promoted the adsorption of NH3 and inhibited the adsorption of SO2, then restricted the reaction between NH3 and SO2 and hindered the formation of ammonium sulfate channels.

As a common heavy metal in the sintering flue gas, Pb can exist in the form of oxide (PbO) and lead to the decrease in the denitration catalysts activity. Ce–Mn/AC (activated carbon) and PbO–Ce–Mn/AC catalysts were prepared by impregnation method and their selective catalytic reduction of NH3 with NO was studied. Results showed that selective catalytic reduction activity of Ce–Mn/AC decreased remarkably after doping PbO. And the NO conversion of Ce–Mn/AC reached 94.52% at 200 °C, while the value was reduced to 65.8% after doping PbO at the same temperature. The doping of PbO decreased the total pore volume and oxygen functional groups of activated carbon, increased crystallinity of Mn oxides on the catalyst, decreased Mn4+ and chemisorbed oxygen content and then inhibited the “fast selective catalytic reduction” denitration reaction for Ce–Mn/AC catalysts. On this basis, the poisoning effects of lead oxide on Ce–Mn/AC catalysts for low-temperature selective catalytic reduction were revealed.

To clarify the Fe doped effects over activated carbon (AC) supported Mn-Ce oxide catalysts and study the influence of Fe addition on the AC, several Mn/Ce/Fe mixed oxide catalysts prepared via an impregnation method supported on AC were investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3. The Mn-Ce-Fe/AC catalyst with 5% (mass ratio) loading exhibited the highest catalytic activity and yielded above 90% NO conversion at 125 degrees C with a space velocity of 12,000 h(-1). The Fe addition could obviously reduce the destruction of AC surface area. Also, the metal ions could insert into graphite crystallite structures of AC, splitting it into smaller graphene-like sheets. After doping with Fe species, the relative ratios of Mn-4/Mnn+, Ce3+ /Cen+ and the surface adsorbed oxygen greatly enhanced in Mn-Ce-Fe/AC catalyst. Additionally, both weak acid and medium acid amount increased significantly after the Fe species introduced in Mn-Ce/AC, which could be attributed to the more exposed active sites of acid due to Fe species or its influence on Mn/Ce species. Relying on the obtained results, a L-H mechanism was proposed, owing to the Fe doping, the average valence state of Mn ions and surface adsorbed oxygen both increased on the Mn-Ce-Fe/AC catalyst, specially accompanying with the surface acid sites promotion, therefore remarkably promoting the denitration efficiency due to all the cumulative effect.

Anosovite crystalline is an ideal mineral for flotation from the Ti-bearing blast furnace (TBBF) slag. Ti3O5 crystal and Al2TiO5 crystal are two kinds of anosovites, and the Al element significantly affects the electronic structure and flotation performance of anosovite. The floatability of Ti3O5 and Al2TiO5 crystals were studied by Mulliken populations, energy bands, and density of states (DOS). In addition, the flotation experiment of the two kinds of anosovite crystals (Ti3O5 and Al2TiO5) was conducted and proved that the density functional theory (DFT) calculation results were accurate. Compared with Ti3O5 crystal, the Fermi energy level of Al2TiO5 crystal shifts around 2 eV in a negative direction by DOS analysis, which is beneficial to flotation. And Al2TiO5 crystal possesses a larger value of bond population, which is 0.41, for Ti-O bonds than Ti3O5 crystal and the bond length of Ti-O in Al2TiO5 crystal is shorter, therefore Al2TiO5 crystal shows a stronger covalency. The changes of the Fermi energy level and the covalency bonds in Al2TiO5 crystal both demonstrated that doping the Al component into the Ti3O5 crystal was beneficial to improve the flotation effect. Moreover, the Al2TiO5 crystal had a higher flotation efficiency compared to the Ti3O5 crystal when the dosages of salicylhydroxamic acid (SHA) and sodium oleate were the same. Therefore, both DFT calculation and experiment show that the flotation effect of the Al2TiO5 crystal is better than that of the Ti3O5 crystal.

In this study, the effect of different zinc salts (ZnCl(2)and ZnSO4) on the deactivation of activated carbon(AC)-based Mn-Ce catalysts and the poisoning mechanism of zinc salts on Mn-Ce/AC are comparatively studied. SEM, BET, XRD, XPS, H-2-TPR, NH3-TPD and In-situ DRIFT are used to characterize the physical and chemical changes of Mn-Ce/AC catalyst. The Selective Catalytic Reduction (SCR) activities of Mn-Ce/AC has a noticeable decline after loading zinc salts, and the highest NO conversion of Zn poisoning catalysts do not exceed 70 %. And the acid site is occupied by Zn(2+)on the catalyst, which affects the chemical adsorption of NH(3)and hinders the formation of the intermediate -NH2. Moreover, the decrease of Mn4+, reducibility of manganese oxide and acid sites are more serious on ZnC-Mn-Ce/AC. Besides, loading ZnSO(4)can improve the content of Ce(3+)and O(beta)on catalyst surface, which can mitigate the poisoning effects of ZnSO(4)on Mn-Ce/AC catalyst. Hence, ZnCl(2)displays a more serious poisoning effect on Mn-Ce/AC catalyst compared with ZnSO4. Then the probable mechanism model of ZnCl(2)and ZnSO(4)on Mn-Ce /AC catalyst is proposed and compared.

In this study, the poisoning effect of CaO on activated carbon (AC)-based Mn-Ce catalysts was discussed. Loading CaO inhibited the catalytic activity of the catalyst and the NO conversion of the catalyst decreased from 69.5% to 38.2% at 75 °C. The amount of MnO2 in AC surface decreased in the process of loading CaO, which was detrimental to the Selective Catalytic Reduction (SCR) performance of the catalyst. The change of manganese oxide form inhibited generation rate for the chemisorption oxygen and NO2, which was the most critical reason for the decrease of catalytic activity. Besides, loaded CaO entered into the pores of the catalyst, which led to the blockage of the pores and further resulted in the decrease of the Brunauer-Emmett-Teller (BET) surface area and total pore volume. It also destroyed the oxygen-containing functional groups and acid site on the surface of AC. All of these caused the deactivation of Mn-Ce/AC catalyst after loading CaO.

Different valence states manganese oxides catalysts (MnO2, Mn2O3 and Mn3O4) were synthesized to investigate their N2O formation pathways during NH3–SCR of NO process. In contrast, the NO conversions of Mn2O3 and Mn3O4 were nearly identical, while MnO2 exhibited better NO conversion activity over the whole temperature range and corresponding to NO conversion of 100% at 150 °C with a space velocity of 36,000 h−1. At low temperature, the majority of N2O was generated from the SCR reactions on the three catalysts. With the increasing temperature, the N2O amounts and the N2O generation ratios from NH3 oxidation of the three catalysts both increased. Besides, NH3 species on MnO2 were easier to be oxidized by gaseous O2, while NH3,ads at Lewis acid sites would partly transfer to NH4+ and NH2 species on Mn2O3 in the presence of O2 and more NH2 species would be formed on the oxygen adsorbed surface of Mn3O4. Both E−R and L−H mechanisms were found conducting on the three catalysts. NH2/NH species on the MnO2 surface would react with gaseous NO to form NH2NO/NHNO and then decomposed to N2/N2O, respectively, while the adsorbed monodentate nitrites combined with NH3,ads and/or NH4+ species to form NH4NO2 that decomposed to N2. Besides the formation and decomposition of NH2NO/NHNO, NH4NO3 was also formed on Mn2O3 and Mn3O4, and then decomposing to N2O.

Series of catalysts with Mn-Ce mixed oxides loaded onto biomass char (BC) modified by nitric acid were prepared via impregnation method. And these catalysts were used for the selective catalytic reduction (SCR) of NO with NH3. Mn-Ce (7:3)/BC catalysts with loading 6% (mass ratio) Mn-Ce oxides showed the best NO conversion ratio of 99.2% at 175 degrees C. The changes of the microstructure, phase composition, metal valence state and functional groups were investigated through SEM, BET, XRD, XPS and FT-IR. It showed that nitric acid modification could increase surface acidic functional groups of biomass char. And surface functional groups on BC could increase NH3 and NO adsorption capacity. In the denitration process, oxygen was transferred from CeO2 to Mn2O3, which could promote the cyclic catalytic reaction rate, then significantly enhanced the NO conversion in the Mn-Ce/BC catalysts. Based on the experimental results and theoretical analysis, the synergetic mechanism model of surface functional groups on the surface of BC, Mn and Ce on the catalysts was set up. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.

The poisoning effects of KCl and As2O3 on selective catalytic reduction (SCR) of NH3 with NO over Mn-Ce/AC catalysts were investigated with the reaction temperature range of 100-250 degrees C. KCl and As2O3 poisoned catalysts were synthesized by impregnation method and catalytic activity test was performed under the condition of simulated flue gas. The changes of crystal structure, microstructure, surface atomic state, surface acidity and functional groups were characterized by XRD, SEM, BET, XPS, NH3-TPD and FT-IR. Deactivation for single KCl or As2O3 doping catalyst was observed and severe synergistic inactivation occurred with the common effect of KCl and As2O3 on the catalyst. KCl destroyed the porosity of active carbon (AC) and could react with -OH and C=O on the surface of AC to ultimately form -O-K and Cl-C-O-K, resulting in the decrease of NH3 and NO adsorption. Besides, KCl caused the reduction of oxygen vacancies and chemisorbed oxygen on the Mn-Ce/AC catalyst. Lattice oxygen of MnOx may be transformed to surface chemisorbed oxygen to oxidize As2O3. As2O3 was oxidized to As2O5 and some layer was formed on the surface of catalyst preventing NH3 and NO adsorption. In addition, As2O3 could increase the number of oxygen vacancies and decrease the surface acidity of Mn-Ce/AC catalyst. According to the experimental results and theoretical analysis, the synergy poisoning model of KCl and As2O3 on Mn-Ce/AC catalysts was schematically established.