Presence Of SO2 Research Articles

The effect of multivalent anions on removal of Titanium dioxide nanoparticles from drinking water sources by coagulation-sedimentation processes: Efficacy and mechanisms

Titanium dioxide nanoparticles (TiO2 NPs) are emerging potential hazard contaminants. There is a pressing need to understand TiO2 NPs removal from anions-spiked complex waters by coagulation-sedimentation (C/S) processes. In this study, we investigate impacts of Cl−, NO3−, SO42−, and PO43− on TiO2 NPs removal at circumneutral pHs by C/S processes. Little removal of TiO2 NPs was observed in the absence and presence of Cl− or NO3−. However, 93% and 82% of 10 mg/L TiO2 NPs were removed within 45 min as dosing 0.6 mM PO43− and 0.8 mM SO42−, respectively, at 10 mg/L polyaluminum chloride (PAC) and pHini. 6.2 in C/S processes, with pseudo-first-order rate constants of 0.098 ± 0.002 and 0.072 ± 0.001 min−1, respectively. Reaction rates in this work were several orders of magnitude faster than those in previous studies. Removal efficiencies of TiO2 NPs reached higher than 89% with a spike of multivalent anions in tap water, thereby exhibiting high practical implication potential. Additionally, the temporal evolution of total particle number and fractal dimension demonstrated that the presence of SO42− and PO43− improved the formation of denser spherical flocs and consequently precipitation rates mainly due to charge neutralization. Moreover, appropriate coagulants, optimized levels of PAC, SO42− and PO43−, and acidic pHs favored nanoparticle removal. Together, this work suggests that the presence of background water composition could facilitate nanoparticle removal in a C/S process.

The effects of SO2 exposure on three-way catalysts for passive SCR operation

Efficient lean-burn gasoline engines cannot employ traditional three-way catalysts (TWCs) to control NOX emissions due to excess oxygen. Passive selective catalytic reduction (pSCR) is a process designed to control NOx by generating NH3 over the TWC during fuel-rich operation, storing it on a downstream SCR, and then converting NOx during fuel-lean operation. This work is focused on studying sulfur effects on this promising strategy. Two hydrothermally-aged commercial catalysts were studied for their effectiveness in the presence of SO2: a Pd-based TWC and a TWC with NOX storage. The sulfated samples were evaluated in a flow reactor under pSCR conditions and with targeted reactions. SO2 inhibited the water gas shift and steam reforming reactions, decreasing (but not eliminating) NH3 production; however, initial activity is recoverable after a simple thermal treatment at 650 °C. This work will prove valuable in understanding, mitigating, and even reversing the effects of SO2 inhibition on real pSCR systems.

Sulfur tolerance and self-regeneration mechanism of Na-Ru/Al2O3 dual function material during the cyclic CO2 capture and catalytic methanation

The combined CO2 capture and methanation with Dual Function Materials (DFM) is emerging as a vibrant field of research for its potential to increase the efficiency and reduce the cost of current multistage CCU processes. In this work, we set out to investigate for the first time the impact of sulfur poisoning over a Na-Ru/Al2O3 DFM operated in a fixed bed reactor with alternate feeds under realistic conditions including the presence of SO2, H2O and O2 in the process gas stream. The results of the extensive characterization of the fresh and sulfated (reaction-aged) DFM evidenced a remarkable intrinsic tolerance of the combined CO2 capture and methanation process to high concentrations of SO2 in the feed due to a self-regeneration mechanism of the Ru catalytic sites.

Promoting H2O/SO2 resistance of Ce-Mn/TiO2 nanostructures by Sb5+/Sb3+ addition for Selective catalytic reduction of NO with NH3

A series of xSb-4Ce-10Mn/TiO2 (x = 0, 2, 3, 4, 5, 6) catalysts were prepared by a reverse co-precipitation method. The catalysts were characterized by XRD, TEM, Raman, XPS, etc. The effect of the Sb5+/Sb3+ loading on the NO conversion and H2O/SO2 resistance was studied. The xSb-4Ce-10Mn/TiO2 displayed the highest low-temperature catalytic activity, best N2 selectivity and best H2O/SO2 resistance at × = 4. The Sb5+/Sb3+ addition slightly decreased the catalytic activity, but helped to improve the H2O/SO2 resistance. Meanwhile, the Sb5+/Sb3+ addition decreased the Mn4+ and Ti4+ content, but increased the Ce3+ and surface adsorbed oxygen content of the catalyst. In the presence of SO2, the Brønsted acid sites of the 4Sb-4Ce-10Mn/TiO2 increased. Results showed the Sb5+/Sb3+ addition enlarged the surface area, made (NH4)2SO4 easy to decompose and inhibited the MnSO4 formation, which contributed to the improvement of the H2O/SO2 resistance. Transient in situ DRIFT spectra showed the reaction of the NH3-SCR over the catalysts belongs to the Langmuir-Hinshelwood (L-H) mechanism.

Experimental study and modified modeling on effect of SO2 on CO2 absorption using amine solution

Understanding the competitive mechanism in absorption process between SO2 and CO2 is essential for simultaneous absorption of SO2 and CO2. In this study, the effect of SO2 on CO2 absorption using amine solution was studied experimentally and theoretically. The CO2 absorption rates in MEA/MMEA/MDEA solutions were determined using wetted wall column. Results showed that the reduction of flue gas temperature was beneficial for CO2 absorption at the typical coal-fired flue gas CO2 concentration. On this basis, the effect of SO2 on CO2 absorption performance was studied. Firstly, the overall CO2 mass transfer coefficient decreased under exposure to SO2. Secondly, in the presence of SO2, pH variation of amine solution increased. In addition, the saturated CO2 capacity largely decreased when SO2 was continuously bubbled into the solution. Furthermore, the quantum chemical calculation showed that CO2 had little effect on the absorption performance of SO2 whereas SO2 greatly weakened the interaction between CO2 and amines. The overall CO2 mass transfer coefficient was modified considering the effect of SO2. The competitive absorption factor, χ, was introduced to modify the CO2 liquid phase diffusion coefficients. The average deviation of overall CO2 mass transfer coefficient narrowed to 1.76 % (0.5 mol/L MEA), 1.13 % (1.0 mol/L MEA), 1.88 % (1.0 mol/L MMEA) and 1.43 % (1.0 mol/L MDEA) respectively, which agreed well with the experimental results.

Efficient removal and detoxification of Cr(VI) by PEI-modified Juncus effuses with a natural 3D network structure

In the present study, a novel PEI-modified Juncus effuses (PEI-JE) adsorbent was prepared based on the natural 3D network structure of JE via a simple and environmental-friendly method with the help of the ethanol/aqueous solution. SEM, EDS, ATR-FTIR and XPS were performed to reveal the physical and chemical structure of the PEI-JE. The Cr(VI) removal by the PEI-JE was investigated by bath adsorption experiments. Results showed that the developed PEI-JE exhibited the same 3D network structure as the JE, which not only was easy to separate from aqueous solution but also can expose more active sites and facilitate mass transfer. The optimal pH for Cr(VI) adsorption on the PEI-JE was 3, and adsorption equilibrium time was related to initial Cr(VI) concentrations. The adsorption kinetic obeyed pseudo-second-order kinetic model, and the adsorption isotherm showed the best fit with Freundlich model. The calculated maximum adsorption capacity was 268.93 mg/g at 25℃. Coexisting ions including Na+, K+, Al3+, H2PO4−, Cl−, NO3– had no remarkable effect on Cr(VI) adsorption, but the presence of SO42−, HCO3– and CO32– caused the efficiency losses of 10.9%, 41% and 66%, respectively. After 10 cycles of adsorption/desorption, Cr(VI) removal rate on the PEI-JE almost kept unchanged, demonstrating that the PEI-JE possessed good reusability. Mechanism study suggested that Cr(VI) removal was involved in a three-step reaction, namely electrostatic adsorption, redox and complexation. Film diffusion was the rate-limiting step and chemical adsorption was the main mechanism. The Cr(VI) adsorbed on the PEI-JE surface was completely reduced to Cr(III), demonstrating that PEI-JE is useful for Cr (VI) removal and detoxification.

Advanced Flue-Gas cleaning by wet oxidative scrubbing (WOS) using NaClO2 aqueous solutions

In this work, we investigate the use of a Wet-Oxidative Scrubber (WOS) to simultaneously control SO2 and NOx emissions from exhaust flue-gases.The experiments are performed in a pilot-scale scrubber with a simulated flue-gas containing 500 ppmv of SO2 and 1030 ppmv of NOx, using water doped with 0.25–1% w/w of NaClO2. The results prove that the adopted WOS is able to simultaneously remove SO2 and NOx, and a synergistic effect is observed for the presence of SO2 in the flue-gas, which improves the NOx removal by establishing more effective and faster oxidative mechanisms under acidic conditions.A predictive model of the WOS unit performance based on the experimental dosage of NaClO2, which takes into account for all the operating parameters of the process, is developed to predict the de-SOx and de-NOx efficiencies and also the wash water pH.

Multi-Level Computational Screening of in Silico Designed MOFs for Efficient SO2 Capture.

SO2 presence in the atmosphere can cause significant harm to the human and environment through acid rain and/or smog formation. Combining the operational advantages of adsorption-based separation and diverse nature of metal–organic frameworks (MOFs), cost-effective separation processes for SO2 emissions can be developed. Herein, a large database of hypothetical MOFs composed of >300,000 materials is screened for SO2/CH4, SO2/CO2, and SO2/N2 separations using a multi-level computational approach. Based on a combination of separation performance metrics (adsorption selectivity, working capacity, and regenerability), the best materials and the most common functional groups in those most promising materials are identified for each separation. The top bare MOFs and their functionalized variants are determined to attain SO2/CH4 selectivities of 62.4–16899.7, SO2 working capacities of 0.3–20.1 mol/kg, and SO2 regenerabilities of 5.8–98.5%. Regarding SO2/CO2 separation, they possess SO2/CO2 selectivities of 13.3–367.2, SO2 working capacities of 0.1–17.7 mol/kg, and SO2 regenerabilities of 1.9–98.2%. For the SO2/N2 separation, their SO2/N2 selectivities, SO2 working capacities, and SO2 regenerabilities span the ranges of 137.9–67,338.9, 0.4–20.6 mol/kg, and 7.0–98.6%, respectively. Besides, using breakdowns of gas separation performances of MOFs into functional groups, separation performance limits of MOFs based on functional groups are identified where bare MOFs (MOFs with multiple functional groups) tend to show the smallest (largest) spreads.

Fractal-like random pore model applied to CO2 capture by CaO sorbent

• The application of fractal dynamics concepts to the random pore model is proposed. • The case-study is CO 2 capture by CaO carbonation in fluidised bed calcium looping. • Results were discussed as a function of the carbonator operating conditions. • The building-up of a solid product layer calls for a time-decreasing diffusivity. • A correlation between carbonation degree and product layer diffusivity is proposed. CO 2 capture from industrial flue gas by CaO in fluidised bed calcium looping processes is one of the means to reduce anthropogenic greenhouse gas emissions. The heterogeneous carbonation reaction has been widely investigated in literature, but in almost all cases the product layer (CaCO 3 -rich) CO 2 diffusivity has been considered as a constant parameter. In this work, the application of fractal-like dynamics concepts to the present case has led to the formulation of an expression for the product layer diffusivity that is function of the carbonation time. This expression has been used in the canonical random pore model, to propose an original fractal model, whose superior accuracy has been demonstrated by validation with experimental data obtained under realistic operating conditions (dual interconnected fluidised beds system, use of a CaCO 3 -rich limestone sorbent, carbonation carried out at 650 °C treating a flue gas with 15% CO 2 and in absence/presence of steam - 10% when present - and SO 2 - 1500 ppmv when present-). Main model parameters were the following: fractal heterogeneity parameter, average value for product layer diffusivity, characteristic time for CO 2 diffusion into the sorbent pores, intrinsic kinetic constant, average value for a modified Biot number. Their values were discussed in the light of the reaction mechanism, and of the effect of the absence/presence of steam and SO 2 in the flue gas to be treated. It has been observed that the presence of steam in the carbonator favours both the intrinsic carbonation kinetics and the CO 2 product layer diffusion, while the presence of SO 2 limits the product layer diffusion.

Ion-mediated desorption of asphaltene molecules from carbonate and sandstone structures

As more and more oil recovery scenarios use seawater, the need to identify the possible mechanisms of wettability state changes in oil reservoirs has never been greater. By using molecular dynamics simulations, this study sheds light on the effect of ions common to seawater (Ca2+, K+, Mg2+, Na+, Cl−, HCO3−, SO4 2−) on the affinity between silica and carbonate as the traditional rock types and asphaltene molecules as an important contributing factor of reservoir oil wetness. In the case of carbonate and silica being the reservoir rock types, the measured parameters indicate good agreement with each other, meaning that (HCO3 − & SO4 2−) and (Na+ & Cl−) ions reached maximum bonding energies of (25485, 25511, 4096, and −4093 eV, respectively). As with the surface charge density measurements, the results of the non-bonding energies between the individual atomic structures agree with those from the simulation cell. In the presence of a silica surface, the radial distribution function (RDF) results determine that the peak of the maximum value for the distribution of the ions is 4.2. However, these values range from 3 to 6.6, suggesting that different ions perform better under the influence of carbonate rock. As these ions are distributed in the simulation box along with the adsorption domain, the conditions for sequestering asphaltene from the rock surface are made ideal for dissolution and removal. At equal ion strength, measuring the distance between the center of mass of rocks and asphaltene structures reveals a maximum repulsion force of 22.1 Å and a maximum detachment force of 10.4 Å in the presence of SO4 2− and Na+ ions on carbonate and silica surfaces.

Anti-sulfur selective catalytic reduction of NOx on Sb-doped OMS-2

Sb doped cryptomelane-type manganese oxides (Sb-OMS-2) with Sb/Mn molar ratios of 0–0.4 were synthesized and investigated for low-temperature selective catalytic reduction of NO by CO (CO-SCR). The resulting catalyst was characterized by X-ray diffractometer (XRD), specific surface area analyzer (BET), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). As a result, the doping of Sb increased the specific surface area and oxygen vacancy concentration of the catalyst. At the same time, most Sb entered the lattice of MnO6 to form Sb–O bonds, and a small number of Sb ions replaced K+ in the tunnel. Sb and Mn synergistically catalyzed the reduction of NO. Compared with undoped OMS-2, the NO conversion rate of Sb0.2-OMS-2 increased from 60% at 150 ℃ to 83%, and from 80% at 300 ℃ to 95%. In the presence of SO2, the NO conversion rate of Sb0.2-OMS-2 at 300 ℃ was 88%, while that of OMS-2 was only 60%.

Enhanced removal of nitric oxide and carbon dioxide from flue gas in a biofilter: Effect of flue gas recirculation and Fe(II)EDTA addition

Flue gas emission from combustion of fossil fuel is a growing environmental concern. In this study the effect of flue gas recirculation and Fe(II)EDTA addition on CO2 and NO removal from flue gas was explored in a biofilter. The effect of SO2 on CO2 and NOx removal efficiencies were also studied herein. The optimal removal efficiencies of CO2 (88.1%) and NO (85.8%) were achieved with the flue gas recirculation of 2:1. The presence of SO2 showed little impact on CO2 or NO removal while induced the decline of NO removal. The addition of Fe(II)EDTA clearly enhanced NO removal (~85%). The Illumina sequencing results showed that abundant sulfur-associated bacteria (Desulfobulbus, Desulfococcus, Sulfurovum, Chlorobium), nitrogen-associated bacteria (Thauera), fermentative bacteria (Longilinea and Anaerovorax), and various iron-reducing bacteria (Geobacter) were detected in the biofilter with Fe(II)EDTA addition. The synergistic effect of denitrifying/iron-reducing bacteria dedicated to the sustainable NO removal.

Influence of corrosion behavior of X80 steel in silty soil containing composite sodium salt based on orthogonal test

AbstractThe corrosion law of X80 steel in silty soils with different contents of sodium chloride and sodium sulfate is studied at different temperatures by using an orthogonal test group of three factors and three levels L9 (34) in conjunction with the results of electrochemical impedance spectroscopy, polarization curve, and microscopic images. The steel corrosion rate increases with the silty soil temperature. The presence of SO42− in silty soil inhibits corrosion in X80 steel. The corrosion mechanism involves competition between Cl− and SO42− for adsorption sites: SO42− ions occupy some corrosion pits, and FeS and other corrosion products are generated and adhere to the surface of the corrosion pits, inhibiting further reaction. A range analysis of the fitted electrochemical impedance spectra and polarization curves of X80 steel shows that the temperature has the strongest effect on the corrosion of X80 steel, followed by the Cl− content, whereas the SO42− content has the least effect. The lowest corrosion rate is found for a silty soil Cl− content of 0.3%, a SO42− content of 2.0%, and a temperature of −20°C.

Insight into the effect of SO42− on the precipitation and solubility of ferric arsenate in acidic solutions: Implication for arsenic mobility and fate

The effect of sulfate (SO42−) on the precipitation of As(V) and Fe(III) and the stability of the generated solid phase as well as its underlying mechanisms, which strongly influences the transportation and fate of As in acidic waters (such as acid mine drainage), is still not well known. This work systematically investigated the precipitation, decomposition, and settling properties of the ferric arsenate phase in the presence of different amount of SO42− at pH 1.2 and 1.8. The results showed that on the one side, the presence of SO42− delayed the removal of As and Fe from the aqueous phase and enhanced the solubility of solid ferric arsenate. The geochemical modelling results showed that the coexisting SO42− induced the formation of aqueous SO42−-Fe(III) complexes, inducing the decomposition of produced ferric arsenate solid phase. On the other side, the addition of SO42− promoted the growth rate of generated ferric arsenate and accelerated the settling of solids. The particle size distribution and transmission electron micorscopy analyses elucidated that the presence of SO42− significantly enlarged the ferric arsenate aggregate size. The infrared spectroscopy and S K-edge X-ray absorption near edge structure results proved that SO42− is incorporated into the structure of ferric arsenate by forming ferric arsenate sulfate solid solution, with each SO42− tetrahedron coordinating with approximately two FeO6 octahedra. The S K-edge extended X-ray absorption fine structrure result gave an averaged S-Fe interatomic distance of 3.21 Å. These results demonstrated that the presence of SO42− enlarged the aggregate size of ferric arsenate dominantly via the S-O-Fe bridging, and then accelerated the settling of SO4-ferric arsenate. The contrasting role of SO42− in influencing As obtained in this study is significant for understanding the mobilization and fate of As and the formation mechanisms of ferric arsenate minerals in acidic systems.

Highly efficient removal of toluene over Cu-V oxides modified γ-Al2O3 in the presence of SO2

Developing efficient catalysts with good resistance to complex flue gas is essential for VOCs removal in coal-fired flue gas. In this study, by exploring the effect of transition metal oxide additive, metal loading and bimetallic synergy on toluene oxidation in coal-fired flue gas, 10Cu-3V/γ-Al2O3 is identified as the optimal catalyst. It achieves 90% of CO2 generation at 350 ℃, which is decreased by ca. 46 ℃ compared with 13Cu/γ-Al2O3. And it also exhibits good resistance to H2O and good stability. ICP-OES, N2 adsorption-desorption isotherms, XRD, TEM, XPS, EPR and H2-TPR analyses were applied to characterize the catalyst composition and physicochemical properties. Doping V into 13Cu/γ-Al2O3 not only leads to better dispersity of CuO and homogeneous elements distribution that benefits to produce more active centers, but also constitutes the redox cycle of V5+ + Cu+ ↔ V4+ + Cu2+ which induces more surface chemical oxygen (Osur). Moreover, since SO2 is the main inhibiting factor in toluene oxidation, the SO2 poisoning mechanism was illustrated by XPS, TG and in situ DRIFT analyses in depth.

SO2-Tolerant Catalytic Reduction of NOx via Tailoring Electron Transfer between Surface Iron Sulfate and Subsurface Ceria.

Currently, SO2-induced catalyst deactivation from the sulfation of active sites turns to be an intractable issue for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Herein, SO2-tolerant NOx reduction has been originally demonstrated via tailoring the electron transfer between surface iron sulfate and subsurface ceria. Engineered from the atomic layer deposition followed by the pre-sulfation method, the structure of surface iron sulfate and subsurface ceria was successfully constructed on CeO2/TiO2 catalysts, which delivered improved SO2 resistance for NOx reduction at 250 °C. It was demonstrated that the surface iron sulfate inhibited the sulfation of subsurface Ce species, while the electron transfer from the surface Fe species to the subsurface Ce species was well retained. Such an innovative structure of surface iron sulfate and subsurface ceria notably improved the reactivity of NHx species, thus endowing the catalysts with a high NOx reaction efficiency in the presence of SO2. This work unraveled the specific structure effect of surface iron sulfate and subsurface ceria on SO2-toleant NOx reduction and supplied a new point to design SO2-tolerant catalysts by modulating the unique electron transfer between surface sulfate species and subsurface oxides.

SO2 capture in a chemical stable Al(III) MOF: DUT-4 as an effective adsorbent to clean CH4

Biomethane (CH4) combustion, as a renewable fuel, is an excellent alternative to decrease the CO2 emissions released into the atmosphere. However, this combustion requires catalysts which are normally poising by the presence of SO2 gas. Then, an auxiliary material capable of selective capturing the contaminant SO2 is necessary. In this work, the SO2 gas adsorption performance of a high stable Al(III) MOF known as DUT-4 was studied. In addition to the high SO2 uptake, in dry and wet conditions, and a high SO2 adsorption cyclability, we have explored for the first time a promising purification of CH4 in presence of SO2, taking into account the high affinity for SO2, even at a low concentration of SO2 (a molar gas composition of 1:99 SO2:CH4).

Insights into samarium doping effects on catalytic activity and SO2 tolerance of MnFeOx catalyst for low-temperature NH3-SCR reaction

The development of catalysts with high NH3-SCR activity in the presence of SO2 was urgent for non-electric industries to control NOx emission at low temperature. Herein, a series of Sm-doping MnFeOx catalysts were synthesized through a typical PEG-assisted co-precipitation method and applied for low-temperature NH3-SCR process. SmMnFe-0.1 catalyst significantly broadened the activation temperature window and yielded almost 100% NO conversion from 75 to 200 °C, simultaneously, the NO removal efficiency still maintained at about 90% in the presence of SO2 and H2O. The characterization results confirmed that Sm could optimize the dispersity of active components and enlarge the surface area of catalyst. Furthermore, strong interaction among active ions facilitated more oxygen vacancies and accelerated NO oxidizing to NO2, further cooperating with abundant adsorbed NH3, leading to cause “Fast SCR” reaction. Both catalysts were dominated by the E-R mechanism despite MnFeOx catalyst also obeyed the L-H pathway. Particularly, the intense redox circles between Sm and Mn inhibited the electron transferring from SO2 to Mn ions, and induced Fe species serving as sacrificial sites along with Sm to preferentially react with SO2, resulting in an excellent SO2 tolerance, and the possible mechanism model was proposed.

Template synthesis of sulfur-doped mesoporous carbon for efficiently removing gas-phase elemental mercury from flue gas

Sulfur doped mesoporous carbon (SMC) was synthesized by using template method for efficiently removing gas-phase elemental mercury from flue gas. MCM-41 was used as sorbent template, and the mixture of thymol blue (C27H30O5S) and 2-thiophene ethanol (C6H8OS) was screened as co-precursor of carbon and sulfur. The mercury removal performance of the SMC was evaluated by fixed-bed mercury adsorption experiment. Effect of precursor ratio, carbonization temperature, adsorption temperature, and SO2 on mercury removal was studied. Combining with sorbent characterization, the mercury removal mechanism of the SMC was clarified. The results show that when the ratio of precursor (thymol blue: 2-thiophene ethanol) is 1:6 and the carbonization temperature is set at 900 ℃, the synthetic SMC-900 sorbent is a promising mercury sorbent, which displays excellent mercury removal performance as well as high SO2 tolerance. Decrease of carbonization temperature from 900 ℃ to 700 ℃ significantly reduces the mercury removal performance of SMC due to the incomplete carbonization of precursor. At 50–150 ℃, the mercury removal rate of SMC-900 is more than 97%, but a higher temperature inhibits its mercury removal capacity. The characterization result shows that the SMC-900 is spherical shape nanoparticle and the BET specific surface area reaches 933.0 m2/g. The mass proportions of carbon (C) and sulfur (S) of SMC-900 are 81.29% and 10.29%, respectively. The sulfur in SMC-900 is in the form of thiophene bond (C-S-C) and oxidized sulfur (C-SOx-C). In the presence of SO2, the main mercury removal product is HgS because the oxygen-containing functional group is occupied by SO2.

SO2- and H2O-Tolerant Catalytic Reduction of NOx at a Low Temperature via Engineering Polymeric VOx Species by CeO2.

Selective catalytic reduction (SCR) of NOx over V2O5-based oxide catalysts has been widely used, but it is still a challenge to efficiently reduce NOx at low temperatures under SO2 and H2O co-existence. Herein, SO2- and H2O-tolerant catalytic reduction of NOx at a low temperature has been originally demonstrated via engineering polymeric VOx species by CeO2. The polymeric VOx species were tactfully engineered on Ce-V2O5 composite active sites via the surface occupation effect of Ce, and the obtained catalysts exhibited remarkable low-temperature activity and strong SO2 and H2O tolerance at 250 °C. The strong interaction between Ce and V species induced the electron transfer from V to Ce and tuned the SCR reaction via the E-R pathway between the NH4+/NH3 species and gaseous NO. In the presence of SO2 and H2O, the polymeric VOx species had not been hardly influenced, while the formation of sulfate species on Ce sites not only promoted the adsorption of NH4+ species and the reaction between gaseous NO and NH4+ but also facilitated the decomposition of ammonium bisulfate through weakening the strong bond between HSO4- and NH4+. This work provided a new strategy for SO2- and H2O-tolerant catalytic reduction of NOx at a low temperature.