SCR Performance Research Articles

Perovskite surface regulation to enhance the catalytic performances on SCR and Hg0 oxidation at low temperature

LaMnO3 is one of the most common Mn-based perovskites which has been studied as a low-temperature catalyst for NOx reduction. However, the Hg0 oxidation performance of LaMnO3 is not ideal. An acid treatment method was adopted to regulate the LaMnO3 surface to expose more active sites. The obtained MnO2/ LaMnO3 sample showed enhanced SCR and Hg0 oxidation performances. The NO conversion rate and Hg0 removal efficiency of MnO2/ LaMnO3 could be over 85% in the temperature range of 150−250 °C. The results suggested that the catalyst might be used to remove NO and Hg0 simultaneously at low temperature in coal-fired flue gas.

Si/Al Ratio Determines the SCR Performance of Cu-SSZ-13 Catalysts in the Presence of NO2.

A comparative study was performed to investigate the NH3-selective catalytic reduction (SCR) reaction activity of Cu-SSZ-13 zeolites having Si/Al ratios (SARs) of 5, 18, and 30. Remarkably, the Cu-SSZ-13 zeolite catalysts exhibited completely opposite behaviors as a function of SAR under standard SCR (SSCR) and fast SCR (FSCR) reaction atmospheres. Under SSCR conditions, the NOx conversion increased as expected with the decreasing SAR. Under FSCR conditions, however, the NOx conversion decreased as the SAR decreased, contrary to expectations. In this study, based on characterization of the catalysts by X-ray diffraction, transmission electron microscopy, electron paramagnetic resonance, H2-temperature-programmed reduction, temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy, together with theoretical calculations, the authors found that the amount of Brønsted acid sites goes up while the SAR goes down, leading to an increase in the accumulation of NH4NO3 under FSCR reaction conditions. Moreover, the accumulated NH4NO3 is of greater stability for those low SAR Cu-SSZ-13 catalysts. These two reasons cause the FSCR performance of Cu-SSZ-13 to decrease with a decrease in SAR. As a result, the NO2 effect on SCR activity changes from promotion to inhibition as the SAR decreases.

Effects of doping Mn, Cu and Fe oxides on polyhedron CeO2 catalyst during NH3-SCR reaction

BackgroundCeria (CeO2) was considered as one of the most promising catalysts due to its oxygen storage capacity and redox property. However, the low activity of CeO2 catalyst in SCR reaction limited its further application on industrial processes. MethodsTransition metal (Mn, Cu and Fe) oxides were impregnated on nanopolyhedron CeO2 (CeO2-NP) catalysts to investigate the SCR performance. Significant findingsThe Mn-CeO2-NP catalyst displayed the highest NOx conversion (ca. 70% conversion at 300 °C), followed by the Cu-CeO2-NP catalyst (ca. 65% conversion at 300 °C) and then the Fe-CeO2-NP catalyst (ca. 45% conversion at 300 °C). The results of H2-TPR showed that Mn-CeO2-NP and Cu-CeO2-NP catalysts were more efficient in reducing hydrogen at lower temperature than that of Fe-CeO2-NP catalysts. Based on XPS measurements, it was determined that the Oα/(Oα+Oβ) ratio was Mn-CeO2-NP (ca. 65%)> Fe-CeO2-NP (ca. 59%)> Cu-CeO2-NP (ca. 55%) catalyst. It was also shown by Raman spectroscopy that the Mn-CeO2-NP catalyst had a higher concentration of oxygen vacancies than that of the Cu-CeO2-NP and Fe-CeO2-NP catalysts. Meanwhile, more Brønsted acid sites, Lewis acid sites, nitrate and nitrites species were found in the Mn-CeO2-NP catalyst as seen by in situ DRIFT spectra.

Associations between different eGFR estimating equations and mortality for CVD patients: A retrospective cohort study based on the NHANES database.

To assess the associations of eGFRCKD-EPI (estimated glomerular filtration rate (eGFR) by chronic kidney disease epidemiology collaboration equation), eGFRMDRD (eGFR by modification of diet in renal disease), and serum creatinine (scr) on the death for American people diagnosed with cardiovascular disease (CVD) respectively, and to compare the predicted performance of eGFRCKD-EPI, eGFRMDRD, and scr. A total of 63,078 participants who derived from the National Health and Nutrition Examination Survey (NHANES) database, were obtained in this retrospective cohort study, and collected the baseline characteristics all participants. The outcomes of our study were defined as death, and eGFR estimating equations was defined as eGFRCKD-EPI, eGFRMDRD, and scr. Univariate and multivariate COX analysis were performed to assess the relationship. A subgroup analysis was conducted based on whether patients had anemia. Simultaneously, we also considered the predictive value of eGFRCKD-EPI, eGFRMDRD, and scr in the risk of death. All patients were followed for at most 5-years. After excluded participants who did not meet the inclusion criteria and had missing information, the present study included 2419 participants ultimately, and were divided into alive group (n = 1800) and dead group (n = 619). The mortality rate for CVD patients in this study was approximately 25.59% at the end of follow-up. After adjustment for covariates, the result showed that participants with eGFRCKD-EPI/eGFRMDRD < 30 mL/min/1.73 m2 or 30 to 45 mL/min/1.73 m2 had a higher risk of mortality. Similarly, participants with scr (Q4 ≥ 1.2) were associated with the increased risk of death. Additionally, eGFRCKD-EPI has a higher predictive value in 1-year, 3-years, and 5-years risk of death among patients with CVD than eGFRMDRD and scr. The lower level of eGFR was associated with higher risk of death among American population diagnosed with CVD, especially for non-anemic patients. Importantly, our study also displayed that CKD-EPI-based calculation equation of eGFR (eGFRCKD-EPI) provided for a better predictive value than eGFRMDRD and scr in the risk of death.

Elucidating the facet-dependent reactivity of Cr[sbnd]Mn catalyst for selective catalytic reduction of NOx with NH3

The facet-dependent reactivity of CrMn catalysts was still unclear, hindering the further enhancement of their low-temperature SCR performance. Herein, the facet-dependent reactivity of CrMn1.5O4 catalyst for NH3-SCR of NOx was innovatively illustrated by numerous characterizations and density functional theory (DFT) calculations. Exposed (100) facet of CrMn1.5O4 catalyst exhibited best low-temperature SCR activity with ≥90 % NO conversion within 148–296 °C and 2.86 × 10−3 mol/(g·s) reaction rate within 160–240 °C. The characterizations revealed that (100) facet could induce the increase of BET specific area, electron transfer, concentration of Mn4+ and Oα, surface acidity, redox ability, NH3 and NOx adsorption/activation capacity. Subsequently, DFT calculations demonstrated that (100) facet exhibited the strongest affinity for NH3 and NO due to its unique 3O3c-Mn5c-2O4c bond and abundant charges transfer near the active adsorption sites, and Brønsted acid and oxygen vacancies were most easily formed on (100) facet. Furthermore, H2O formation as the rate determining step easily occurred on (100) facet. Eventually, we successfully improved the low-temperature SCR activity of CrMn1.5O4 catalyst by further tailoring highly active (100) facet from 0.754 to 0.865. This work provides the deeper understanding of facet-dependent reactivity and a good strategy to improve the catalytic activity of the catalysts.

Mechanistic effect of SO2 on mesoporous CuFeAlZrOx catalyst for simultaneous removal of Hg0 and NO at wide temperature range

Mesoporous CuFeAlZrOx catalyst is a promising substitute of V-based catalysts for potential candidate for simultaneous removal of Hg0 and NO due to its excellent performance at a broad temperature range. SO2 poisoning effects remain a challenge in development of efficient SCR catalysts for applications. In this paper, the effect of SO2 on mesoporous CuFeAlZrOx catalyst for simultaneous removal of Hg0 and NO at wide temperature range was studied. Relevant characterization techniques of H2-TPR, NH3-TPD, TG, SO2-TPD, XPS, Hg-TPD and in situ DRIFTS were used to reveal the correlativity between the physicochemical properties and SO2 resistance of CuFeAlZrOx catalysts. SO2 exhibited an inhibitory effect at low temperature (<300 °C) but a facilitative effect at high temperature(≥300 °C) for NH3-SCR reaction. At the same time, a promoting effect on Hg0 removal was observed during the whole temperature range. The deposition of NH4HSO4 and the decrease of redox capacity caused the loss of SCR activity at low temperatures, while the formed iron sulfate provided more Lewis acid sites facilitate the high-temperature SCR performance due to the strong electron withdrawing effect of the SO double bonds. In addition, the generation of iron sulfates and NH4HSO4 on mesoporous Cu1FeAlZrOx were alleviated because of the sacrifice of copper sites and promoted NH4HSO4 decomposition in mesopore channels. SO2 reacted with Hg0 to form HgSO4 and Hg2SO4, which contributed to Hg0 removal performance.

Promotional role of Nb modification on CuCeOx catalyst for low temperature selective catalytic reduction of NO with NH3: A mechanism investigation

CuCeOx and CuCeNbOx-k with different Nb doping ratios were obtained by the citric acid method and applied in NH3-SCR process. The activity test results elucidated that the addition of Nb effectively ameliorated the low-temperature SCR performance. Among them, CuCeNbOx-0.4 catalyst had the finest SCR activity (more than 90% in 185–370 °C), highest N2 selectivity, excellent SO2&H2O resistance and thermal stability. Numerous characterization analysis demonstrated that CuCeNbOx-0.4 had the largest specific surface area, the strongest surface acidity and the most excellent redox properties. The conclusions of in situ DRIFT manifested the Nb modification generated more activated species, enhanced the reactivity of ad-NH3 and ad-NOx species, and the SCR reaction on CuCeNbOx-0.4 mainly followed the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Furthermore, the Nb doping also formed the dual redox cycle (Cu2+ + Nb4+ ↔ Cu+ + Nb5+, Cu2+ + Ce3+ ↔ Cu+ + Ce4+), which facilitated the low-temperature SCR reaction.

Design of robust Co-doped Mn3O4 spinel catalysts for selective catalytic reduction of NO with NH3 at low temperatures

Developing an efficient catalyst with high intrinsic active sites for selective catalytic reduction of NOx with ammonia (NH3-SCR) at ultra-low temperature flue gas is challenging but desirable. Herein, a Co-doped Mn3O4 catalyst (Co0.04Mn2.96O4) was created by a confinement-pyrolysis-oxidation strategy using bimetallic Co–Mn–MOF–74 as the precursor, which exhibited excellent SCR performance with 96% NO conversion at 130 °C under a GHSV of 100,000 h−1. Benefited from the uniform microstructure of catalyst and combined with characterization and theoretical calculations, an efficient Cotet–O–Mnoct active site is revealed for NH3-SCR, and the formation of oxygen vacancies on Cotet–O–Mnoct site plays a crucial role in the adsorption and activation of reactants, which facilitating the low–temperature NH3-SCR activity. This work provides new insights into the design and synthesis of highly active NH3-SCR catalysts with high intrinsic active sites used at low temperatures.

Efficient MnOx-CeO2/Ti-bearing blast furnace slag catalyst for NH3-SCR of NO at low temperature: Study of support treating and Mn/Ce ratio

Exploring novel low-temperature SCR catalyst supports with excellent properties and low cost is a significant challenge. Ti-bearing blast furnace slag (Ti-BFS) presented great potential in this field due to high contents of Ti, Si and Al elements. In this work, Ti-BFS was pretreated and optimized by hydrochloric solution, and suitable treatment conditions were obtained. Ti and Si were well enriched and other components (especially Ca) were mostly leached, while the modified slag exhibited well-developed porosity and high surface area. An efficient MnOx-CeO2/Ti-bearing blast furnace slag catalyst (Mn-Ce/ATS) can be developed by loading appropriate MnOx-CeO2 ingredients on this support. 4Mn-Ce/ATS catalyst performed better SCR performance because of its excellent NH3 adsorption capacity and reactivity, as well as more alkali sites. Cerium was beneficial to bond NH3 species and manganese was advantageous to adsorb NO. Although SO2 resistance of this catalyst was relatively undesired, its H2O resistance was perfect. This work can provide a guidance on realizing waste Ti-bearing blast furnace slag utilization and reducing the denitrification cost.

The effect of fusel oil as a reductant over the multi-metallic catalyst for selective catalytic reduction of NOx in diesel exhaust at low-temperature conditions

In this paper, the NOx conversion efficiency of Mo-Cu-Ag/TiO2/Cordierite catalyst at low temperatures was investigated by using fusel oil as a reductant. The properties of Mo-Cu-Ag/TiO2/Cordierite catalyst prepared by the impregnation method were analyzed by Brunauer-Emmett-Teller, scanning electron microscopy with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy analyses, and X-ray diffraction. The SCR performance tests were performed under real diesel exhaust gas conditions in a temperature range from 200 °C to 290 °C with a rise of 10 °C, five different engine loads, and three different space velocities. The minimum and maximum NOx conversion rates were determined as 78,99% at 5 kW and 85.94% at 1 kW engine load, respectively.

Cu, Co, or Ni species in exchanged Y zeolite catalysts and their denitration performance for selective catalytic reduction by ammonia

Identifying the role of Cu, Co, or Ni species in exchanged zeolite catalysts by different preparation methods has been widely concerned for selective catalytic reduction by ammonia (NH3-SCR). Here, we found that ammonia wet ion exchange method (AWIE) was useful for increasing ionic species and improving ion polymerization degree in traditional NaY (Si/Al = 2.5) zeolites. Cu, Co, and Ni substituted Y zeolite prepared by AWIE method achieved better SCR performance than those by conventional wet ion exchange method (CWIE). Meanwhile, the coordination states and chemical environments of Cu, Co, and Ni exchanged species influenced the redox and adsorption properties of catalysts. Cu-NH3-IE catalyst had a wider SCR temperature window than Co-NH3-IE and Ni-NH3-IE catalysts owing to its more stable NH3 adsorption, lower temperature, and smaller area of reduction peak. We proposed that the balance of NH3 adsorption and oxidation in thermodynamics and kinetics was the key for high N2 selectivity. This work provided a new idea for modifying the active sites of zeolite catalysts to achieve high activity and N2 selectivity in a broad temperature window.

Efficient Catalysis for Low-Temperature CO Selective Catalytic Reduction over an Fe-Cu Bimetal Oxide Catalyst Supported on Amorphous SiO2

Efforts have been devoted to exploring the effective composite catalysts for low-temperature selective catalytic reduction of NOx by CO (CO-SCR) using Fe-Cu bimetal oxide (Fe2Cu1) as the active component and rice husk ash (RHA), amorphous SiO2, and activated carbon (AC) as supports. The results showed that the beneficial role of RHA as a catalyst support for CO-SCR was primarily reliant on amorphous SiO2 in RHA and not on AC. Both Fe2Cu1/RHA and Fe2Cu1/amorphous SiO2 catalysts exhibited the best catalytic performance of CO-SCR, which had good stability, wide active temperature range, high conversion ratio, 100% N2 selectivity, and superior resistance to O2, SO2, and H2O (g). The CO and NOx conversion ratios of Fe2Cu1/amorphous SiO2 could reach up to approximately 100% from 100 to 500 °C. The excellent SCR performance was associated with the large specific surface area and good structural stability of amorphous SiO2, the uniform distribution of active sites, dual redox cycle of Fe2O3 and CuO species, and many surface-adsorbed oxygen species, which made amorphous SiO2-based catalysts highly competitive for application in the SCR process. This research provides the underlying insights for the improvement of industrial application to realize ″non-ammonia SCR″ technology with near-zero NOx/CO emissions synergistically at low temperatures.

Inspecting Promotive Functions of Antimony Oxides for NH3-Assisted Selective Catalytic NOX Reduction

It is widely accepted that Sb oxide promotes redox cycling feature and SO&lt;sub&gt;2&lt;/sub&gt; resistance of a catalyst utilized for selective catalytic NO&lt;sub&gt;X&lt;/sub&gt; reduction (SCR) at low temperatures (≤300 ℃). However, promotive roles of Sb oxide have never been explored with the alteration of its crystal phases, which can be crucial to direct the overall acidic/redox characteristics and SCR performance of a catalyst along with its SO&lt;sub&gt;2&lt;/sub&gt; tolerance. In this regard, while implementing TiO2-supported Mn oxide (Mn) as a model catalyst, we successfully isolated Sb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; and Sb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; on Mn using wet impregnation and precipitation protocols, leading to produce Mn-Sb-I and Mn- Sb-P, respectively. The resulting catalysts were verified to have comparable acidic properties, yet, exhibit distinct redox traits, as evidenced by the greatest quantity of labile oxygens for Mn-Sb-I (Sb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;) compared to Mn and Mn-Sb-P (Sb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;). This leads to significant enhancement of SCR performance and SO&lt;sub&gt;2&lt;/sub&gt; resistance for Mn-Sb-I over the others.

Hydrothermal Aging Treatment Activates V2O5/TiO2 Catalysts for NOx Abatement

Thermal stability is crucial for the practical application of deNOx catalysts. Vanadia-based catalysts are widely applied for the selective catalytic reduction of NOx with NH3 (NH3-SCR). Generally, hydrothermal aging at high temperatures induces the deactivation of deNOx catalysts. However, in this work, a remarkable increase in low- and medium-temperature NH3-SCR activity was observed for a V2O5/TiO2 catalyst after hydrothermal aging treatment, especially at 750 °C for 16 h. After the vanadia-based catalyst was hydrothermally treated at 750 °C, the specific surface area decreased and the surface VOx density and surface V ratio increased significantly. Therefore, the aged catalyst presented more abundant polymeric vanadyl species than the fresh one. Furthermore, the redox capability was improved markedly after hydrothermal treatment due to the strong interaction of vanadia and titania, contributing to the NH3-SCR reaction. 750 °C is the optimal temperature to activate the V2O5/TiO2 catalyst, improving the SCR performance significantly. This study provides an in-depth understanding of vanadia-based catalysts for practical applications.

Fabrication of wide temperature lanthanum and cerium doped Cu/TNU-9 catalyst with excellent NH3-SCR performance and outstanding SO2+H2O tolerance

The effects of La on the catalytic performance, SO2 and H2O resistance of Cu–Ce/TNU-9 catalyst were studied in the selective catalytic reduction of NOx via ammonia (NH3-SCR). The results show that the La doped Ce–Cu/TNU-9 (CCL/T9) catalyst exhibits better SCR performance than Ce–Cu/TNU-9 (CC/T9) and Cu/TNU-9 (C/T9) in the wide temperature window (200–450 oC) due to La benefiting from enhancing Cu++Ce4+↔Cu2++Ce3+ to facilitate the electron transfer, which further accelerates the oxidation of NO into NO2 that leads to the “Fast SCR”. The La can also enhance the surface acidic, redox property and is beneficial to the formation of oxygen vacancy. Meanwhile, the larger content of Ce3+ can produce oxygen vacancy, resulting in rising SCR activity. The CCL/T9 has outstanding water and SO2 resistance, which may be due to the adsorbed S on the surface of these catalysts mainly existing in the form of a small amount of sulfate and sulfite, the decomposition of ammonium bisulphite under high temperature and the hydrophobicity of TNU-9 zeolite.

A novel flower-like MnCe/TiO2catalyst with controlled morphology for low-temperature selective catalytic reduction of NO with NH3

In this work, a flower-like TiO2 support was firstly synthesized via the hydrothermal method, and then Mn and Ce were loaded onto the synthesized flower-like TiO2 carrier by impregnation for the selective catalytic reduction of NO with NH3 (NH3-SCR). The activity test results manifested that the flower-like MnCe/TiO2 (MnCe/TiO2-FL) catalyst exhibited marvelous SCR performance (almost 100% NO conversion in the range of 150–250 °C) and satisfactory resistance to SO2 and H2O. Based on a series of characterization experiments, it could be found that the MnCe/TiO2-FL catalyst possessed a larger surface area, higher Ce3+ and Mn4+ content, superior surface acidity and redox performance, which greatly ameliorated to the SCR performance of the MnCe/TiO2-FL catalyst. Furthermore, the accelerated surface adsorbed oxygen mobility and the increased quantity of active species also promoted to the SCR activity of MnCe/TiO2-FL at low temperatures.

Dual-layer AdSCR monolith catalysts: A new solution for NOx emissions control in cold start applications

A new dual layer monolithic AdSCR system (adsorption + selective catalytic reduction) constituted by Cu/CHA (top) and BaO/Al2O3 (bottom) was prepared and studied as a potential solution to improve the low-T performances of NH3-SCR catalysts. Two washcoat formulations were considered. The samples were characterized through optical microscopy and SEM-EDX; the ammonia storage capacity and the catalytic activity in the standard NH3-SCR reaction were also studied. When using water as solvent during the deposition, migration of Ba into the Cu-zeolite layer was observed, resulting in a decay of both ammonia storage capacity and NH3-SCR activity. On the other hand, when water was replaced by n-butanol, the two layers were well segregated, and no loss of SCR performances was noted. The butanol-based formulation exhibited promising performances in the NOx abatement during cold-start transients, with a NO removal efficiency of 31%, prior to ammonia injection, and of 52% after ammonia injection.

Morphology and crystal–plane dependence of CeO2–TiO2 catalysts: Activity and mechanism for the selective catalytic reduction of NOx with NH3

CeO2–TiO2 catalysts with four different morphologies were successfully synthesized by a hydrothermal method and tested for selective catalytic reduction of NOx with NH3 (NH3–SCR). For the four catalysts, CeO2–TiO2 nanocubes (CT–NC) and nanorods (CT–NR) preferentially exposed {100} and {110} facets, respectively; furthermore, nanosheets (CT–NS) and nanospheres (CT–NH) mainly exposed {111} facet. Interestingly, CT–NH catalyst showed the best NH3–SCR performance and the NOx conversion exceeded 97% at 325 °C. Through a series of characteristic methods manifested that the short–range ordered structure of Ce–O–Ti in CT–NH catalyst provided stronger surface acidic sites to promote the high–temperature activity. Moreover, the abundant Ce3+ species and appropriate reduction ability on {111} facet of CT–NH catalyst also caused outstanding deNOx activity. Reaction mechanism study showed that the Langmuir–Hinshelwood (L–H) mechanism and Eley–Rideal (E–R) mechanism existed simultaneously on all catalysts in NH3–SCR reaction. Meaningfully, two types of E–R mechanism were present on CT–NH catalyst, while L–H mechanism was dominant.

Construction of fluffy MnFe nanoparticles and their synergistic catalysis for selective catalytic reduction reaction at low temperature

Mn-based catalysts had favorable low temperature SCR performance but it was restricted its practical application due to easy deactivation. Different proportions of Fe species were doped into Mn-MOFs as a precursor by a simple one-pot solvothermal method. A series of MnOx, Mn4FeOx, MnFeOx and MnFe4Ox catalysts with different structures were obtained by calcining under air. MnFeOx showed better catalytic activity and water resistance at low temperature. The NO conversion was 96% at 200 °C and kept above 85% in the range of 120–280 °C. Through a series of characterizations, it was found that manganese and iron species were highly dispersed in the MnFeOx catalyst, which was a vital factor for SCR reaction. Moreover, the MnFeOx catalyst not only possessed a large specific surface area and pore volume but also had a better reduction ability and abundant oxygen vacancies to adsorb and activate the reaction gases. Therefore, the catalyst possessed a satisfactory catalytic performance. More importantly, charging transfer between active manganese species and iron species in MnFeOx catalyst could effectively inhibit H2O poisoning and improve the stability of the catalyst. The results of in situ DRIFTs experiments showed that the low temperature NH3-SCR reaction of MnFeOx catalyst followed L-H mechanism. The effects of Fe doping content on the crystal structure of active species and SCR performance of manganese-based catalysts were revealed.

Three-dimensionally ordered macroporous Ce-W-Nb oxide catalysts for selective catalytic reduction of NO with NH3

• Ce-W catalyst is optimized by combining Nb-modification and structural manipulation. • 3DOM structure provides abundant diffusion channels for catalytic reactions. • 3DOM structure ensures the high dispersion of active components. • Synergistic effect among the species of Ce, Nb and W promotes the increase of O α . • Active NH 3 and NO x species are increased over 3DOM Ce-W-Nb catalysts. A string of 3DOM Ce-W-Nb ternary catalysts for NH 3 -SCR were prepared by a colloidal template method. The 3DOM Ce-W-Nb 0.15 catalyst had the best SCR activity and yielded more than 90% NO conversion at 275 ∼ 450 °C in the high GHSV of 120,000 h −1 . In addition, it exhibited good tolerance to H 2 O and SO 2 . The addition of Nb increased the number of active sites and made them dispersed more evenly, optimized the pore structure to a certain extent, and increased the specific surface area. The interaction among Ce, W, and Nb species promoted the increase of chemisorbed oxygen and enhanced the redox properties, thus contributing to the satisfactory SCR activity at low temperatures. In addition, the synergistic effect between Nb and W provided sufficient Lewis acid sites for the 3DOM Ce-W-Nb x catalyst, which was conducive to the good SCR performance at high temperatures. The NH 3 -SCR reaction on 3DOM Ce-W-Nb x catalysts followed both Eley-Rideal and Langmuir-Hinshelwood mechanisms. The doping of Nb was beneficial to boost the adsorption of NH 3 and improved the reactivities of NH 3 adsorbed species while facilitating the generation of active NO x species. These accelerated the reaction rate and optimized the reaction path.