SCR Performance Research Articles

The effect of dopants (Fe, Al) on the low-temperature activity and SO2 tolerance in solvothermally synthesized MnOx NH3-SCR catalysts

Fe-doped MnOx catalyst prepared by a preferred solvothermal method displayed noticeably better low-temperature (LT) NH3-SCR performance and water stability than an analogously prepared Al-doped MnOx catalyst. The SCR activity of both catalysts decreased markedly when exposed to SO2, but the resultant MnFeOx-S catalyst retained higher LT activity than MnAlOx-S and recovered significantly more of its original activity after thermal regeneration (400 °C). Comprehensive characterization confirmed that the deactivation of the catalysts was governed by formation of stable metal sulfates, which only decomposed to a minor extent upon thermal treatment although Al doping lowered the thermal stability of the adsorbed sulfur species. Additionally, Fe doping was found to facilitate electron transfer between Mn and Fe ions and weaken the interaction between active sites and deposited sulfates during the heating procedure, which promoted re-oxidation of Mn2+ to catalytically active Mn3+/Mn4+. Altogether, the altered redox properties resulted in improved LT SCR performance, enhanced water stability, higher SO2 tolerance and superior regeneration of the MnFeOx catalyst.

Enhanced low-temperature SCR performance of metal Oxide/Cu-SSZ-13 composite catalysts: The role of oxygen species in metal oxide

A composite catalyst composed of metal oxide and Cu-SSZ-13 components (OXZEO) presents a promising approach to solve the current challenge of improving the low-temperature efficiency of SCR catalysts. The diverse forms of oxygen present within the metal oxide components impact the formation of nitrate, which plays a critical role in the deNOx pathway, thereby influencing the overall SCR reaction in OXZEO. Despite this, the relationship between the various types of oxygen in metal oxide and their catalytic role in OXZEO catalysts remain not fully understood. To clarify this relationship, the activities of Cu-SSZ-13 combined with MnOx, CeOx, and ZrOx, respectively, were compared and analyzed. The low-temperature pathway (below 200 °C) for the three catalysts is primarily ascribed to the interplay between oxide-derived nitrate precursors and NH3 bound to Brønsted acids within the zeolite. However, MnOx/Cu-SSZ-13 demonstrated a stronger synergistic effect, achieving around 50 % higher NOx conversion than Cu-SSZ-13 alone at 200 °C, which was superior to the other two composite catalysts. Characterizations reveal that MnOx with surface oxygen vacancies can supply a significant quantity of chemisorbed oxygen, thus producing more reactive bridged nitrates and bolstering the reaction between nitrate and NH4+ in MnOx/Cu-SSZ-13. On the contrary, for CeOx/Cu-SSZ-13 and ZrOx/Cu-SSZ-13 catalysts, the lattice oxygen of the metal oxide encourages the formation of less active bidentate and monodentate nitrates, resulting in inferior low-temperature SCR performance.

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance

Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NOx with ammonia (NH3-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces the catalyst’s SCR performance. Herein, a hierarchically porous SSZ-13 zeolite was synthesized via a trans-crystallization method assisted by the use of carbon black as a hard template in a short synthetic period, and the corresponding Cu-SSZ-13 catalysts with mesopores exhibited improved low-temperature activity and hydrothermal stability when compared with their microporous counterpart. A series of characterizations revealed that the mesopores are conducive to an increase in Cu loading while helping to stabilize the CHA structure and maintain the Cu species in their ionic form. More importantly, intra-particle diffusion limitations are reduced via the introduction of the mesopores owing to the shortened diffusion path inside the SSZ-13 zeolite, thus not only enhancing the active sites’ accessibility but also promoting the diffusion of the reactants and products. This work contributes to the design and synthesis of a high-performance Cu-SSZ-13 zeolite SCR catalyst for the removal of NOx emitted from diesel vehicles.

Excellent NH3-SCR activity and significant sulfur resistance over novel core–shell Cu-SSZ-13@meso-CeO2 catalyst

A core–shell Cu-SSZ-13@meso-CeO2 catalyst with both microporous and mesoporous pores was successfully synthesized using a self-assembly technique in this research. The catalyst was tested via NH3–SCR of NOx removal from diesel exhausts. The Cu-SSZ-13@meso-CeO2 catalyst was found to have significantly improved activity at high temperatures, wider temperature range, improved hydrothermal stability, and anti-sulfur performance. After the introduction of meso-CeO2, a significant synergistic effect between the Cu2+/Ce4+ ions on the core–shell layer was observed, and the amounts of Cu2+–2Z species and acidic sites increased, which may be conducive to the superior catalytic performance of Cu-SSZ-13@meso-CeO2 contrasted to Cu-SSZ-13. Subsequent to hydrothermal treatment, Cu-SSZ-13@meso-CeO2 maintains a superior CHA-type structure, additional L-acidic sites, and isolated Cu2+ ions while being protected by a meso-CeO2 shell. In addition, in the presence of SO2, the meso-CeO2 shell in Cu-SSZ-13@meso-CeO2 reacts with SO2 to produce cerium sulfate, which serves as a protective component for the copper species on Cu-SSZ-13. Moreover, the reaction mechanism studies have indicated that NO reduction primarily adheres to the E–R mechanism on Cu-SSZ-13, whereas both L–H and E–R mechanisms contribute to Cu-SSZ-13@meso-CeO2. SO2 has a less significant inhibitive effect on the adsorption of NH3 over Cu-SSZ-13@meso-CeO2 compared with that over Cu-SSZ-13. The inhibitive influence of SO2 on Cu-SSZ-13@meso-CeO2 is primarily owing to the inhibitory adsorption of NO and the reduction of the L–H reaction path, with little effect on the E–R reaction mechanism, which is significantly affected in Cu-SSZ-13. The Cu-SSZ-13@meso-CeO2 catalyst demonstrated exceptional NH3–SCR performance, a broad temperature range, and super hydrothermal stability as well as anti-sulfur performance, indicating great application prospects for NOx removal from diesel vehicle exhausts.

Promotion Effect of Iron on Activity and N2 Selectivity of Mn/Ce Catalysts in the NH3-SCR Reaction

Manganese oxides are known to have good low-temperature SCR performance, whereas improving their medium- and high-temperature catalytic performance and N2 selectivity remain a challenge. Herein, manganese-based ternary catalysts Fe–Mn/Ce, using CeO2 as the carrier and Fe as the second active component, were constructed to effectively solve this problem. Fe–Mn/Ce catalysts show excellent catalytic performance, with NOx conversions of more than 90% over a wide operating temperature range (164.5–419.4 °C) with high and N2 selectivity. Further investigation showed that, for the Fe–Mn/Ce catalyst with rich redox sites and surface acidity, higher amounts of Fe2+ and Mn4+ are the important factors promoting excellent SCR reactivity. Besides, the Fe modification can generate effective electron transfer to reduce the N2O generation pathway and increase the catalytic reaction sites, thus enhancing the overall catalytic performance.

Modulation of paired acid centers for the α-, β-, γ- and δ-MnO2 for the NH3-SCR: A comparative density functional theory (DFT) study

The selective catalytic reduction with ammonia (NH3-SCR) has been the state-of-the-art technology for NOx pollutant control, in which the catalyst plays a key part. Along with the urgent academic pursuit of higher SCR activity at lower temperatures, manganese oxides are considered one of the most promising components to construct a strong oxidation center for the catalyst surface. However, the rough use of manganese oxides has only a limited promotion effect on lowering the temperature window of the catalyst. Their SCR performance will be largely determined by the physicochemical properties of manganese oxides of different crystal phases (α, β, γ, and δ-MnO2) and the modulation methods of acid centers, which are still controversial and lack systematic and reliable arguments. In this paper, we conducted comprehensive research on their physicochemical properties and proposed a reliable evaluation of their potential for SCR reaction via density functional theory (DFT) calculation. W and Mo were introduced as new acid centers to pair with redox centers. Among the α-, β-, γ-, and δ-MnO2, γ-MnO2 showed the strongest NH3 adsorption capacity with relatively high NO capture ability. However, when Mn atoms coordinated with W or Mo atoms to form Mn-O-W or Mn-O-Mo bonds on the α-MnO2 surface, the altered electronic distribution characteristics resulted in the maximum NH3 and NO adsorption energies with the minimum dehydrogenation barrier. Mo 4d had better bonding interaction with N 2p compared with W 5d, showing a higher NH3 capture ability. The electron transfer results indicated that the high catalytic activity of MnO2 originated from the strong interaction between H and the O2c site on the surface, while the O2c site easily forms an oxygen vacancy. Additionally, W or Mo doping may change the rate-determining steps.

Selective catalytic reduction of NO by CO over MOF-based CuOx@ZIF-67 catalysts and reaction mechanism

The selective catalytic reduction of NOx using CO as a reduction gas (CO-SCR) is a promising method to eliminate NO and CO simultaneously and attracted much of the attention recently. Currently, the majority of CO-SCR catalysts tested showed high activity in the absence of oxygen, but their performance was poor when oxygen was present. As a result, it is important to explore an effective catalyst under aerobic conditions. This work proposed a new catalysts for CO-SCR based on metal organic framework (MOF) material, specially, ZIF-67. A series ofx%CuOx@ZIF-67 catalysts were successfully prepared and the CO-SCR reactivity was evaluated in a fixed-bed micro reactor with simulated flue gas in the presence of O2, containing 500 ppm NO, 1000 ppm CO, 0–10% O2 balanced by N2 at a temperature range of 200–375 °C. The catalysts were characterized by SEM, XRD, TGA, NH3-TPD, XPS, BET, H2-TPR, and in situ DRIFTS to investigate the influence of microstructure, texture, and chemical properties of the catalyst on the SCR performance. The result demonstrates that the CuOx@ZIF-67 catalysts were effective for CO-SCR performance and NO conversion was 100% at 300 °C for 8.0 %CuOx@ZIF-67 catalyst. Cu improved the surface oxygen vacancies and the reduction ability of the catalyst. The synergy effect of Cu on Co can increase the acid sites and the amount of Lewis acid on the catalyst surface. The primary intermediate species, according to in situ DRIFTS analysis, were Cu+–CO, bidentate nitrate, and bridging nitrate. The reaction path of CO-SCR on CuOx@ZIF-67 was proposed based on the in situ DRIFTS analysis.

Optimized local geometry and electronic structure of MoO3/CeO2 catalyst by adding copper cations for boosted nitrogen oxide reduction performance

The construction of highly active centers over the CeO2-based catalyst for the low-temperature NH3 selective catalytic reduction of nitrogen oxides (NH3–SCR) technology in non-power industry is one of the challenges in the application field. Herein, the SCR performance of MoO3/CeO2 catalyst has been remarkably enhanced by introducing Cu to induce the generation of active MoO structure. Advanced spectroscopy characterizations reveal that the adding of Cu into MoO3/CeO2 catalyst could create unsaturated sites on CeO2 for Mo anchor, and the enhanced electrons transfer from Mo to Cu would cause the formation of a new terminal MoO with highly distorted octahedral geometry, which is a new Lewis acid site for coordinated NH3 production. Meanwhile, the added Cu creates the adsorbed site for gaseous NO and the formed Mo-O-Cu pair center facilitates the transformation of ionic NO2– generated from NO adsorption to NO2, which is conducive to the fast SCR reaction process.

Enhanced low-temperature activity and huimid-SO2 resistance of MnFe-based multi-oxide catalysts for the marine NH3-SCR reaction

Several MnFe-based multi-metal oxides were synthesized as NH3-SCR catalysts by a simple coprecipitation method for abating NOx of marine diesel exhausts. The Co and Nb-doped MnFeCeAl catalysts exhibit NOx conversion over 90% and N2 selectivity above 95% at 180–270 °C, especially the MnFeCeAlCo catalysts can inhibit nearly all sulfate species growth within 150 ppm humid-SO2 gases at 225 °C. The structural characterization results revealed that Co, Nb, Sm, and Sb doping can enhance interactions among different components and promote active component dispersion. Temperature programmed analysis indicated that the Co doping is not only more favorable for improving redox properties, but can also enhance the surface acidity, which are advantageous to improve the activity, N2 selectivity, and humid-SO2 resistance. Moreover, the XPS results implied that the binding energy shift or the valence variation of the Sm, Sb, Nb, and Co species on catalyst surfaces are favored to raise the atomic ratios of high-valent Mn species and surface adsorbed oxygen, which can promote the redox property significantly and further facilitate SCR activity. Accordingly, the excellent activity and humid-SO2 tolerance of the MnFeCeAlCo catalyst should attribute to its lower redox temperature, strong interaction between oxides, 47.3% surface Mn4+/Mn3+ species, and 71.8% adsorbed oxygen, which provide a method for improving the SCR performances of MnFe-based catalysts with humid SO2 resistance.

Tailoring valence state of V in V-Mo atomically dispersed ensemble enables exceptional NH4HSO4 poisoning resistance for NH3-SCR reaction

Although V2O5/WO3/TiO2 catalyst has been commercially used for selective catalytic reduction of NOx with NH3 (NH3–SCR), it suffers from activity loss due to ammonium bisulfate (ABS) poisoning at low temperatures below ABS dew point (≤280 °C). Here, we demonstrate that V2O5/MoO3/TiO2 catalyst with H2 pretreatment (designated V2O5/MoO3/TiO2_H2) exhibits high activity and excellently stable NH3–SCR performance at 180–230 °C under SO2 and H2O poisoning conditions. Nevertheless, commercial V2O5/WO3/TiO2 catalyst is quickly deactivated under identical conditions after reaction for 25 h due to formation of liquid–like ABS. Electronic structure investigations show that H2 pretreatment decreases oxidation states of V species of the V2O5/MoO3/TiO2_H2 catalyst, and reduced V species suppress the SO2–to–SO3 oxidation rate. The suppression of SO2–to–SO3 oxidation rate contributes to lower formation rate of ABS on catalyst surface. MoO3/TiO2 with ABS decomposition ability different from those of conventional or bulk material was synthesized on the basis of our previous efforts, and used as a fundamental building block in V2O5/MoO3/TiO2_H2. Control experiments show that the MoO3/TiO2 building block in V2O5/MoO3/TiO2_H2 has excellent ability to decompose ABS. Difficulty of ABS formation and rapid decomposition rate of ABS offer a net result in terms of improved ABS resistance and high activity for V2O5/MoO3/TiO2_H2 catalyst.

Extraordinary Detoxification Effect of Arsenic on the Cadmium-Poisoned V2O5/TiO2 Catalyst for Selective Catalytic Reduction of NOx by NH3

Arsenic has been found as a serious toxicant for the catalysts in the selective catalytic reduction of NOx with NH3 (NH3-SCR). However, the detoxification effect of arsenic on the cadmium-poisoned V2O5/TiO2 catalyst was found in this work. With an arsenic loading of 1.8 wt %, the NOx conversion over cadmium-poisoned V2O5/TiO2 increased from 45.1 to 88.3% at 350 °C under a GHSV of 300,000 h–1. Meantime, the adverse effect on N2 selectivity caused by arsenic was reduced. The catalyst characterization manifests that the surface VOx-active sites were liberated from the restriction of cadmium due to the interaction between cadmium and arsenic. More importantly, it was found that the SCR performance of the catalysts was highly dependent on the surface VOx sites. In situ experiments proved that the released surface VOx species could not only provide the Lewis sites for the NH3 adsorption but also dominate the redox cycle (V5+ ↔ V4+) during the NH3-SCR process. We believe that this study can inspire directions for the design of NH3-SCR catalysts with superior resistance to different poisons.

Revisiting the Impact of Tungsten on the Catalytic Properties of Ammonia-SCR V2O5-WO3/TiO2 Catalysts: Geometric vs. Electronic Effects

The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study.

A review on identification, quantification, and transformation of active species in SCR by EPR spectroscopy.

Electron paramagnetic resonance (EPR) is the only technique that provides direct detection of free radicals and samples that contain unpaired electrons. Thus, EPR had an important potential application in the field of selective catalytic reduction of nitrogen oxide (SCR). For the first time, this work reviewed recent developments of EPR in charactering SCR. First, qualitative analysis focused on recognizing Cu, Fe, V, Ti, Mn, and free-radical (oxygen vacancy and superoxide radical) species. Second, quantification of the active species was obtained by a double-integral and calibration method. Third, the active species evolved because of different thermal treatments and redox-thermal processes under reductants (NH3 and NO). The coordination information of the active species in catalysts and their effects on SCR performances were concluded from mechanism viewpoints. Finally, potential perspectives were put forward for EPR developments in characterizing the SCR processes in the future. After all, EPR characterization will help to have a deep understanding of structure-activity relationship in one catalyst.

Insights into Synergy of Copper and Acid Sites for Selective Catalytic Reduction of NO with Ammonia over Zeolite Catalysts

Herein, we report the function of copper sites in Cu-SSZ-13, Cu-ZSM-5 and Cu-Beta catalysts with the same Si/Al ratio (14) and Cu/Al ratio (0.4) on selective catalytic reduction of NO with NH3 (NH3-SCR) and reveal the relationship between active sites (Cu sites, acid sites) and catalytic activity. The results show that the amount of isolated Cu2+ ions in the catalysts directly determines the formation of strong Lewis acid sites and reaction intermediate NO3− ions, thus affecting the low-temperature SCR performance, while the amount of highly stable Cu+ ions and Brønsted acid sites is related to the high-temperature SCR performance of the catalysts. Consequently, it contains enough isolated Cu2+ ions, highly stable Cu+ ions and Brønsted acid sites, which endows Cu-SSZ-13 with excellent NH3-SCR activity.

A novel MnTi mixed oxide catalyst engineered by metal–organic framework precursor for enhancing NOx removal performance

In this research, MnTi metal–organic frameworks (MnTi‐MOFs) were successfully prepared, and derived catalysts were innovatively applied to the removal of NOx by selective catalytic reduction with NH3 (NH3‐SCR). The test results show that the one‐step controllable synthesis of MnTi‐MOFs material is achieved through adjusting the Mn/Ti molar ratios and the proportion of metal to organic ligands, in which the ratio of organic ligands is vitally significant for the synthesis of MnTi‐MOFs (MnTi‐MOFs can only be synthesized with the ligand to metal molar ratio in the range of 3–4). Owing to the special heterogeneity of MOFs, the catalyst sample derived from the MnTi‐MOFs precursor prepared with suitable raw material ratio exhibits the best SCR performance. Series of characterization analyses show that the catalysts derived from MOFs precursors with ordered lattice structure exhibit an appropriate surface chemical adsorption oxygen, an increased Mn4+/Mnn+ content, and enhanced acidity of the surface of the sample. This research affords an innovative method to the controllable preparation of dual metal MOFs and expands the development of catalysts in the field of low‐temperature de‐NOx.

Simultaneous removal of NOx and dust with integrated catalytic filter: Interactions between NH3-SCR and filtration processes

The integrated selective catalytic reduction of nitrogen oxides by NH3 (NH3-SCR) and dust filtration technology can effectively reduce the energy consumption and space of the flue gas purification system. Herein, a novel catalytic filter is fabricated by in situ depositing FeWOx heterogeneous catalyst onto stainless-steel-fiber filter (named as FeWOx/SSFF), which displays excellent deNOx performance (>85 % NOx conversion and 96 % N2 selectivity) with superior H2O and SO2 tolerance, as well as great dedust efficiency (>99.99 % and low residual pressure drop). The suitable oxygen mobility and enhanced charge transfer ability at the crystalline-amorphous interface contribute well to the excellent SCR performance, and the low pressure drop is promoted by the well dispersion of FeWOx species on the SSFF. Notably, a volcanic relationship between dedust process and SCR performance was obtained, due to the boosting of dedust process for the denitrification, which was confirmed by computational fluid dynamics (CFD). Besides, excessive dust-cake could inhibit SCR performance owing to catalytic site being covered by dust particles. Accordingly, SCR process hardly affected dedust efficiency and residual pressure drop. This work reveals the interactions between SCR and dedust processes, and paves a way to design novel catalytic filters for simultaneously removing dust and gas pollutants at practical conditions.

Revealing the effect of crystal size on the high-temperature hydrothermal stability of Cu/SSZ-13 NH3-SCR catalysts

The large-sized Cu/SSZ-13 having a lower amount of Al–OH keeps a relative complete CHA structure after aging. The complete structure is beneficial to the re-dispersion process of copper species and SCR performance during aging.

Poisoning Effects of HCl on MOx‐WO3/TiO2(M=Mn, Ce and V) Catalysts for Selective Catalytic Reduction of NOxby NH3

AbstractSelective catalytic reduction of NOxby ammonia (NH3‐SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MOx‐WO3/TiO2(MW/Ti, M=Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NOxconversion over MnW/Ti and CeW/Ti catalysts, respectively. While the SCR activity over VW/Ti catalyst was hardly affected by HCl. Over MnW/Ti catalyst, the rupture of the Mn−O bond by the strong Mn−Cl binding induced the formation of amorphous MnCl2species. This Cl‐containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in low‐temperature SCR activity. However, instead of directly affecting the CeOxand VOxsites, gaseous HCl reacted with NH3to form NH4Cl species on the surface of CeW/Ti and VW/Ti catalysts. As a result, the SCR activity of VW/Ti catalyst was scarcely influenced by HCl, taking the unchanged redox ability and NH3adsorption. With a further accumulation of NH4Cl on CeW/Ti catalyst, the NOxconversion at low temperature was evidently enhanced due to the promotion in NO‐to‐NO2conversion (Fast‐SCR).

Mechanochemical synthesis of alumina-based catalysts enriched with vanadia and lanthana for selective catalytic reduction of nitrogen oxides.

Novel alumina-based materials enriched with vanadia and lanthana were successfully synthesized via in situ modification using a mechanochemical method, and were applied in ammonia-induced selective catalytic reduction of nitrogen oxides (SCR process). The synthesis was optimized in terms of the ball milling time (3 or 5h), vanadium content (0.5, 1 or 2 wt% in the final product), and lanthanum content (0.5 or 1 wt% in the final product). Vanadium (V) oxide was immobilized on an alumina support to provide catalytic activity, while lanthana was introduced to increase the affinity of nitrogen oxides and create more active adsorption sites. Mechanochemical synthesis successfully produced mesoporous materials with a large specific surface area of 279-337m2/g and a wide electrokinetic potential range from 60 to (-40)mV. Catalytic tests showed that the incorporation of vanadia resulted in a very large improvement in catalytic performance compared with pristine alumina, increasing its efficiency from 14 to 63% at 400°C. The best SCR performance, a 75% nitrogen oxide conversion rate at a temperature of 450°C, was obtained for alumina enriched with 2 and 0.5wt% of vanadium and lanthanum, respectively, which may be consideredas a promising result.

Effect of a novel catalyst zonal coating strategy on the performance of SCR coated particulate filters

The selective catalytic reduction catalysts (SCR) coated into a diesel particulate filter (DPF), so called SDPF, can reduce both NOx and particulate in the exhaust gas of diesel engines, which is a promising technology to meet stringent emission regulations. Advanced coating techniques are crucial for optimizing SDPF technology, and this study focused on the effect of a novel catalyst zonal coating strategy on the performance of SDPFs. Three SDPF samples with 50 %, 75 %, and 100 % catalyst coating (named samples I, II, and III, respectively) were tested at ten steady-state engine operating conditions. The results showed that catalyst zonal coated SDPFs (samples I and II) had good NOx conversion rates under most conditions, but the NOx conversion rates of both samples dropped below 80 % at 2200 r/min with full engine load condition. The three SDPF samples had similar pressure drops at low exhaust flow, while catalyst zonal coated SDPFs showed lower pressure drops and flow resistance at high engine speed and heavy engine load conditions, especially for sample I. Catalyst zonal coated SDPFs had slightly lower particulate filtration efficiencies than that of sample III, because some small particulates with a diameter of<50 nm could escape from the catalyst uncoated area due to its high porosity.