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The application of iron oxide to NH3-SCR is attractive but largely hindered by its poor acid properties, and surface sulfation is proven to be a prominent way of enhancing the acidity. As such, the method of enriching the sulfate species on iron oxide is crucial for improving the NH3-SCR performance. In the present study, by employing ammonium bisulfate (ABS) as the source of gaseous SO2 for the purpose of trapping, we reported an effective strategy for enhancing the SO42− immobilization on α-Fe2O3 catalyst via spatial confinement in a mesoporous SBA-15 framework. Interestingly, although the presence of the mesopore channel had an adverse effect on the ABS decomposition, which was expected to produce less available SO2, the measured SO42− immobilized on α-Fe2O3 in the mesoporous SBA-15 system was significantly greater than that of the regular SiO2, demonstrating the promoting effect of the spatial confinement on the SO42− enrichment. Further characterizations of the NH3-TPD, NO oxidation, and NH3-SCR performance tests proved that, as a result of the enhanced acidity, the enrichment of SO42− on α-Fe2O3 displayed a clear correlation with the SCR activity. The results of the present study provide an effective strategy for boosting the catalytic performance of iron oxide in NH3-SCR via SO42− enrichment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CeCoMnO x spinel-type catalyst prepared using oxalic acid precipitant has a more favorable physicochemical structure for NO conversion than that prepared using alkaline precipitant. • 400 °C is the optimum calcination temperature for oxalic acid precipitated CeCoMnO x spinel for NH 3 -SCR reaction. • The oxalic acid precipitated CeCoMnO x calcined at 400 °C has nearly 100 % NO conversion at 100–200 °C at GHSV = 15,000 mL·g−1·h−1. • An interface-enhanced redox macrocycle mechanism incorporating acid cycling is proposed for oxalic acid precipitated CeCoMnO x catalysts. CeCoMnO x spinel-type catalysts for the selective catalytic reduction of NO using NH 3 (NH 3 -SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnO x spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH 3 -SCR activities of the CeCoMnO x spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnO x spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnO x -C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnO x -N-400), and thus CeCoMnO x -C have better low-temperature NH 3 -SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnO x -C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100–125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnO x -N-400 at 100–125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnO x -C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantitative analysis based on the number of active sites disclosed the reaction rates for different copper species actually followed the order of highly dispersed CuO > bulk CuO > clustered CuO. • Highly dispersed CuO was advantageous to enhance NH 3 adsorption and NO x activation via weakly bonded NO x species, which accelerated the reaction via both L-H and E-R pathways. • The presence of clustered CuO induced the formation of stable NO x species and aggravation of NH 3 oxidation. Cu-based catalysts are attractive for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, the inherent contribution from different copper species is still elusive. Herein, by adopting a novel solvent-free preparation, CuO/SiO 2 catalysts with controlled copper species (highly dispersed CuO, clustered CuO and bulk CuO) were constructed for investigation. Evidence for the presence of distinct copper species was provided by diverse characterizations like XRD, N 2 sorption, TEM and XPS. Quantitative analysis based on the number of active sites disclosed the reaction rates for different copper species actually followed the order of highly dispersed CuO (0.19–0.3 min−1) > bulk CuO (0.14 min−1) > clustered CuO (0.03 min−1). Regarding the crucial information of activity contribution and reaction mechanism, results from NO/NH 3 -TPD, kinetics measurement and in situ DRIFTS conveyed that despite with the unique feature of more NO 2 generation, the presence of clustered CuO induced the formation of stable NO x species and aggravation of NH 3 oxidation, delivering a detrimental effect on NO conversion. As a contrast, the formation of highly dispersed CuO was advantageous to enhance NH 3 adsorption and NO x activation via weakly bonded NO x species, which accelerated the reaction via both L-H and E-R pathways. [ABSTRACT FROM AUTHOR]

[Display omitted] This work investigated the influence of introduction methods of cerium and tin on the physicochemical properties as well as the activity and durability of titanium-based catalysts for the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). Precipitation and impregnation methods were adopted to synthesize a series of cerium-tin-titanium catalysts. These catalysts were characterized by XRD, Raman, N 2 adsorption–desorption, HRTEM, EDS mapping, XPS, H 2 -TPR, NH 3 -TPD and in situ DRIFT. Notably, Ce/Sn/Ti(imp) catalyst prepared by stepwise-impregnation method could provide an interface between Ce and Sn for more facile electron transfer than Sn/Ce-Ti(co), Ce/Sn-Ti(co) and Sn/Ce/Ti(imp) catalysts. It promoted the redox equilibrium of Ce4+ + Sn2+ ↔ Ce3+ + Sn4+ shifting to right to produce adequate Ce3+ and surface adsorbed oxygen, resulting in optimal reducibility and surface acidity of Ce/Sn/Ti(imp) catalyst. Besides, the activation of NH 3 and desorption of NO x readily occurred on the surface of Ce/Sn/Ti(imp), which were favorable for the proceeding of subsequent reactions and excellent performance of NH 3 -SCR. [ABSTRACT FROM AUTHOR]

The introduction of WO 3 species on to FeTiO x catalysts led to the formation of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen, surface W-OH species, which were beneficial to the NH 3 -SCR reaction. [Display omitted] • The catalytic activity of FeTiO x was improved after the loading of WO 3 species. • The amount and strength of Brønsted acid sites was enhanced. • Fe(3+n)+-O-W(6−n)+ raised the count of chemical adsorbed oxygen, surface W-OH species. A series of WO 3 modified iron-titanate mixed metal oxides catalysts (the molar ratio of Fe/Ti = 4:1) were synthesized by conventional impregnation method and tested for selective catalytic reduction of NO x by NH 3. The addition of WO 3 species could enhance the catalytic performance of FeTiO x and 6 W/FeTiO x showed optimal activity with above 80 % NO conversion under a wide operating temperature window of 200–400 °C. It also exhibited excellent stability in the presence of H 2 O and SO 2 at 250 °C, even as low as 225 °C, which provided a suitable deNO x candidate for stationary sources. The characterization methods including XRD, BET, XPS, H 2 -TPR, NH 3 -TPD, NO-TPD and in situ DRIFTs were used to investigate the structure and surface properties of catalysts and their influence on the catalytic activity. The results demonstrated that the impregnation of WO 3 species led to the strong electronic inductive effects between Fe3+and W6+, Ti4+ and W6+ in the forms of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen species, surface OH-, which were stimulative to low-temperature NH 3 -SCR reaction. The increased amount of surface Brønsted acid sites mainly came from W-OH species. Besides, the reaction pathway over 6 W/FeTiO x mainly followed Eley-Rideal mechanism at 225 °C through the reaction between gaseous NO and adsorbed NH 3 species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel effect of strong acid-redox interface hinders NH 3 -SCR activity is reported. • Three Ce 2 (SO 4) 3 -CeO 2 catalysts with distinct interfaces are constructed. • NO adsorption and oxygen vacancy formation are limited after Ce 2 (SO 4) 3 addition. • Weak interface promotes NO activation and the formation of active nitrites. The occurrence of NH 3 -SCR (selective catalytic reduction of NO with NH 3) reaction on catalyst surface typically requires acid and redox sites. However, the role of acid-redox interaction on NH 3 -SCR performance is still obscure due to complex acidities and entangled acid-redox sites. Herein, three types of model Ce 2 (SO 4) 3 -CeO 2 catalysts with distinct interfaces are constructed to reveal the effect of acid-redox interaction on NH 3 -SCR performance. That is, SO 4 2-/CeO 2 -VS (vapor sulfation of ceria) with strong acid-redox interfacial contact, SO 4 2-/CeO 2 -WI (wet impregnation), and SO 4 2-/CeO 2 -SG (solid grinding) with limited interfaces. It is found the redox property is significantly disturbed as a result of the electron-withdrawing effect from the sulfate. Theoretical result unravels that the introduction of Ce 2 (SO 4) 3 retards the oxygen vacancy formation over CeO 2. Due to restricted interfaces in SO 4 2-/CeO 2 -SG, the negative influence from acid sites is greatly alleviated. Further mechanism study discloses the weakened acid-redox interaction actually changes the nature of surface NO x species, resulting in the generation of reactive species (*O-N-O* and cis -N 2 O 2 2-) and the promotion of surface reaction via Langmuir-Hinshelwood (L-H) mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • The immobilization efficiency of sulfate species in ABS/FeSi catalyst exhibits a distinct atmosphere-dependent feature. • ABS/FeSi-NO displays the most remarkable activity enhancement due to the accelerated depletion of NH 4 +. • NH 3 treatment inhibits ABS decomposition and results in less SO 4 2- immobilization. • NH 3 treatment brings addition effect of α-Fe 2 O 3 disintegration, which was detrimental to activity enhancement. SO 4 2- immobilization is pivotal for boosting the catalytic performance of iron oxides in NH 3 -SCR. However, the critical issue related to sulfate species enrichment on α-Fe 2 O 3 is still elusive. Herein, by employing ammonium bisulfate (ABS) as the source of SO 4 2-, we conducted a detailed investigation on the effect of reaction atmospheres (NH 3 , NO + O 2 and NH 3 + NO + O 2) on the immobilization of sulfate species and their consequence for ABS poisoned Fe 2 O 3 /SiO 2 (ABS/FeSi) catalysts in NH 3 -SCR. Results showed sulfate group could be transferred from ABS to FeSi under thermal treatment and the efficiency actually exhibited an atmosphere-dependent feature. The promotion effect from NO/O 2 was most prominent due to accelerated consumption of NH 4 +, whereas NH 3 treatment retarded ABS pyrolysis, resulting in reduced sulfate immobilization on FeSi surface. Besides, an unexpected effect on Fe 2 O 3 disintegration was exhibited by NH 3 , which was detrimental to activity enhancement due to disruption of electronic property. By correlating catalytic performance with adsorption feature, we propose the occurrence of reaction via E-R pathway over sulfated FeSi catalysts. The result of present study can enrich our understanding on the controlled sulfate immobilization for robust SCR denitration. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sm doped CeO 2 -TiO 2 catalyst presents excellent NH 3 -SCR activity in range of 250–425 °C. • The acidity and redox property are adjusted with appropriate balance by Sm doping. • Redox cycle of Ce4++Sm2+⇌Ce3++Sm3+ is responsible for the good SO 2 tolerance. Abstract The Sm doped CeO 2 -TiO 2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H 2 O and SO 2 in the NH 3 -SCR reaction, was synthesized. The reasons for the high activity and SO 2 resistance of the catalyst were investigated by a series of characterization. The H 2 -TPR and O 2 -TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NO x species and activation ability of NH 3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO 2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO 2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO 2 tolerance ability. [ABSTRACT FROM AUTHOR]

Abstract We first present preparation of MnO x –CeO 2 –Al 2 O 3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis (SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR). Using the catalyst with 18 wt.% Mn (18MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr− 1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18MnCe1Al2 showed great resistance to SO 2 (100 ppm) and H 2 O (5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H 2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18MnCe1Al2 has an extensive pore structure, with a BET surface area of approximately 135.4 m2/g, a pore volume of approximately 0.16 cm3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnO x –CeO 2 –Al 2 O 3 catalysts were good, and because of the simplicity of the preparation process, the SHS method is applicable to their industrial-scale manufacture. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

• Three MnOx-CeO 2 catalysts with controlled surface and interfacial properties are prepared for investigation. • Strong interface between dispersed MnOx and CeO 2 does not show the best NH 3 -SCR performance. • The unique role of crystalline Mn 3 O 4 in promoting NH 3 activation is revealed. • The catalytic performance can be considerably improved by the synergistic interaction between crystalline Mn 3 O 4 and CeO 2. MnOx-CeO 2 catalysts have been widely investigated in the reaction of selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, the existence of diverse Mn species together with multiple interfaces between MnOx and CeO 2 precludes clear understanding of the synergy. Herein, by constructing MnOx-CeO 2 catalysts with controlled dispersion and interface properties, the significant promotion effect of interfacial contact between CeO 2 and crystalline Mn 3 O 4 in NH 3 -SCR was revealed. Although dispersed MnOx exhibited the combined merits of strong interaction with CeO 2 , improved textural property and abundant adsorption sites for NO/NH 3 , the catalytic performance was still not superior. With advent of Mn 3 O 4 crystallites, the NO conversion was much enhanced, demonstrating essential role of crystalline MnOx. Notably, loss of activity was also observed when apparent phase segregation between ceria and crystalline Mn 3 O 4 occurred, emphasizing the importance of Mn 3 O 4 /CeO 2 boundary. Further mechanism analyses from in situ NH 3 -DRIFTS, quantitative titration of surface NOx with NH 3 and kinetics measurement disclosed the crucial role of crystalline Mn 3 O 4 in activating NH 3 for reaction with NOx anchored on ceria, greatly boosting the catalytic performance. The result of present study enriches our understanding on the synergism between MnOx and ceria in NH 3 -SCR. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hybrid strategy is employed to design catalysts with superior K resistance. • The main reason for CeMn deactivation is cut-off of L-H mechanism resulting from the formation of stable nitrates. • The addition of ZSM-5 can re-activate the inert nitrates. • Alkali metals poisoned catalysts can be regenerated by ZSM-5 hybridization. The application of cerium-manganese oxides (CeMn) in controlling exhaust gas from biomass combustion is greatly inhibited due to poor resistance to alkali metals. Herein, we report a smart strategy to circumvent the K poisoning problem of CeMn by physically coupling with ZSM-5, which exhibited almost no activity loss even under a high loading of 2 wt % K 2 O. Results showed that in contrast to the conventionally believed disturbance of redox property and reduction of acid sites, the dominant effect from K loading on the deactivation of CeMn catalysts lies on the formation of chemically inert nitrates, which significantly restrains the reaction cycle via Langmuir-Hinshelwood route. With ZSM-5 hybridization, the stable nitrates over CeMn can be facilely activated and consumed by NH 4 + species introduced by ZSM-5, thus transforming poisoning sites into active sites and ensuring superior catalytic performance. The study presenting here not only provides an efficient strategy for fabricating NH 3 -SCR catalysts with superior K resistance but also sheds new light on the deactivation mechanism of K over CeMn catalysts. [ABSTRACT FROM AUTHOR]

• Thin-layered titania confined in SBA-15 was successfully synthesized by grafting strategy. • The amorphous thin-layered titania exhibited much enhanced surface acidity and regulated electronic state. • Activity of Fe supported titania catalyst were greatly improved, and H 2 O surprisingly promoted the catalyst activity. • The catalyst revealed promising SO 2 resistance, SO 2 was confirmed to have negligible influence on reactants adsorption. TiO 2 is a famous support for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). Engineering the morphology and structure of TiO 2 is effective to modulate the interaction with surface dispersed component, providing further opportunity to improve catalytic performance. In this study, we rationally construct thin-layered titania confined in mesoporous silica via a surface grafting strategy. It exhibits high specific surface area with amorphous structure along mesopore channel, and much more Brønsted acid sites are generated than bulk TiO 2 due to defect induced oxygen-related species. After iron oxide loading, both the denitration activity and H 2 O/SO 2 tolerance are greatly promoted as compared to conventional Fe/TiO 2. Further characterizations reveal the obtained catalyst displays uniform iron oxide dispersion and intense Fe-Ti interaction, resulting in superior redox behavior and increased acidity. Notably, it is found the introduction of H 2 O exhibits a promotional effect on NO conversion efficiency, which can be ascribed to enhancement of NH 3 adsorption capability. Besides, SO 2 has negligible disturbance on NO/NH 3 adsorption, leading to superior sulfur tolerance. The result of present study demonstrates vital role of surface structure engineering of TiO 2 for sustainable denitration, which opens up a new avenue for designing well-performed and stable NH 3 -SCR catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cryptomelane-type NMOs were synthesized by solvent-free in-situ Ni-doping method. • NMOs-4 catalyst showed over 85 % NO conversion at 100–300 ℃ for NH 3 -SCR. • Tuning Ni loading could control the surface acidity and redox ability. • NH 3 activation was the key to broaden the active temperature region. Cryptomelane-type Ni-doped MnOx catalysts (NMOs) prepared by solvent-free doping method showed very attractive performances in wide temperature zones and stability for selective catalytic reduction (SCR) at 100–300 ℃. The effect of Ni loading on NH 3 -SCR activity at medium temperature (200–300 ℃) was investigated. The NMOs-4 catalyst not only maintained excellent low temperature (100–200 ℃) NH 3 -SCR activity, the NO conversion was approached to 100 %, but also significantly improved the medium temperature activity while the NO conversion increased from 54.4% to 87.2% at 300 ℃ (T 95 = 100–265 ℃) compared with undoped MOs catalyst (T 95 = 100–225 ℃). Appropriate Ni loading could effectively tune the surface lattice oxygen activity and acidity of catalyst to ensure the NH 3 activation ability at low temperature and inhibit the occurrence of NH 3 direct oxidation at higher temperature. On other words, moderate NH 3 activation capacity was the key to achieve a wide temperature region of MnOx-based catalysts. [ABSTRACT FROM AUTHOR]

• A confinement strategy was adopted to design and synthesize a novel Mn-Ce based deNO x catalyst • The confined MnCeO x @Z5 catalyst was assembled by a mesoporous zeolite (ZSM-5) as shell and Mn-Ce oxides as core • MnCeO x @Z5 displayed enhanced water and SO 2 resistance for NH 3 -SCR of NO x • The enhanced performances should be attributed to the shielding and synergy effects over MnCeO x @Z5 Nitrogen oxides (NO x) are a primary source of air pollutants from combustion of fossil fuels. Though Mn-Ce based catalysts exhibit superior low temperature activities, their water and SO 2 tolerance is inferior to other metal oxide catalysts, due to their strong water adsorption and sulfate species formation tendency at low reaction temperatures. Herein, a confinement strategy was adopted to design and synthesize a novel Mn-Ce based catalyst for selective catalytic reduction of NO x with NH 3. The confined MnCeO x catalyst was assembled with a simple one pot method, using a mesoporous zeolite (ZSM-5) as the shell and Mn-Ce oxides as the active core (MnCeO x @Z5). Owing to the zeolite shell's shielding effect and the synergy between the alumina-silica zeolite shell's acidic properties and the mixed oxide cores' redox properties, the novel MnCeO x @Z5 catalyst displayed enhanced water and SO 2 resistance as compared to the MnCeO x supported on ZSM-5 (MnCeO x /Z5) and its precursor (MnCeO x @Al-SiO 2). Evidently, the zeolite sheath hinders sulfate species formation, and this phenomenon was further investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (In situ DRIFTS). The novel shielding and acid-redox synergy effect/strategy adopted in this work can be applied to design other high performance deNO x catalysts for air pollution control. [ABSTRACT FROM AUTHOR]

• The influence of CuO content on CuO/PRM catalysts was investigated. • High dispersed CuO promotes catalyst reducibility and NH 3 -SCR activity. • High dispersed CuO activates NH 3 and promotes NO x desorption. • NH 3 -SCR activity depends on synergistic effect between CuO and PRM. A series of copper-modified red mud catalysts (CuO/PRM) with different copper oxide contents were synthesized by wet impregnation method and investigated for selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The catalytic results demonstrated that the red mud catalyst with 7 wt% CuO content exhibited the excellent catalytic performance as well as resistance to water and sulfur poisoning. The red mud support and copper-containing catalysts were characterized by XRF, XRD, N 2 adsorption–desorption, HRTEM, EDS mapping, XPS, H 2 -TPR, NH 3 -TPD and in situ DRIFT. The obtained results revealed that well dispersed copper oxide originating from 1 to 7 wt% CuO contents was more facile for the redox equilibrium of Cu2+ + Fe2+ ↔ Cu+ + Fe3+ shifting to right to form Cu+ and surface oxygen species than crystalline CuO generating from high CuO loading (9 wt% CuO), which was beneficial to the enhancement of reducibility and the formation of Lewis acid sites on the catalyst surface. All these factors made significant contributions to the improvement of NH 3 -SCR activities for CuO/PRM catalysts. Moreover, in situ DRIFT analysis combined with DFT calculated results confirmed that the finely dispersed copper species not only enhanced the NH 3 activation but also promoted the NO x desorption, which synergistically facilitated the NH 3 -SCR process via the Eley–Rideal mechanism. [ABSTRACT FROM AUTHOR]

• The dual effects of ABS on NH 3 -SCR performance of Fe 2 O 3 -WO 3 /MCM-41 is observed and illustrated for the first time. • The formation of surface metal sulfates sustainably promotes the catalytic performance. • Nearly 90% of sulfates in ABS are immobilized after NH 4 + consumption. • Both the acidity and redox properties of catalyst are greatly improved after metal sulfates formation. Ammonium bisulfate (ABS) has long been considered as a main poisoning material in the selective catalytic reduction by NH 3 (NH 3 -SCR) due to the inevitable coverage of sticky ABS on catalytic active sites in sulfur-containing atmospheres, which severely hinders the achievement of stable and highly active NH 3 -SCR catalysts. In the present study, we report a novel observation of the dual effects of ABS on the NH 3 -SCR reaction. That is, ABS inhibits the NH 3 -SCR performance of Fe 2 O 3 -WO 3 /MCM-41 catalyst at low temperatures (50–200 °C) but shows apparent and sustainable reaction promotion when the temperature surpasses 250 °C. X-ray photoelectron spectroscopy (XPS) and NO probing adsorption confirmed that when ABS is deposited on the catalyst surface, a partial interaction between ABS and the Fe 2 O 3 -WO 3 component occurs, resulting in blocking of the active sites and an obvious loss of catalytic activity. With increasing reaction temperature, the ammonium in ABS can be facilely consumed by NO/O 2 , thus inducing the disintegration of poisoning species. The sulfate group transforms into metal sulfate and survives at high temperatures. Importantly, owing to the strong inductive effect of sulfate species, both the acidity and redox properties of the catalyst are greatly improved, which contributes to the enhanced activity. The results of the present study expand our knowledge of the role of ABS in the NH 3 -SCR reaction and will be useful for designing high-performing NH 3 -SCR catalysts. [ABSTRACT FROM AUTHOR]

CeO 2 -TiO 2 hollow spheres with distinct cavity sizes of ca. 500 nm and 5 μm were prepared from carbon spheres and hybrid Ce–C sphere templates, respectively. After 40 h of successive operation in SO 2 -containing gas stream for the NH 3 -SCR reaction, the catalyst with large cavity showed only 4.7% activity loss, while that with small cavity exhibited sharp decrease (ca. 72.6%) in its deNO x activity. Results of physicochemical characterizations manifested that accelerated decomposition of NH 4 HSO 4 on the CeO 2 -TiO 2 catalyst with larger cavity size is likely largely responsible for the improved SO 2 resistance of catalyst activity loss. Hollow structured CeO 2 -TiO 2 yolk-shell catalyst with larger cavity exhibited superior SO 2 resistance due to accelerated NH 4 HSO 4 decomposition. Unlabelled Image • CeO 2 -TiO 2 hollow structured catalysts with different cavity sizes were prepared. • CeO 2 -TiO 2 catalyst with larger cavity showed remarkably enhanced SO 2 resistance. • Accelerated decomposition of NH 4 HSO 4 is account for improved SO 2 resistance. [ABSTRACT FROM AUTHOR]