Diesel Soot Combustion Research Articles

Co,Ce nanoparticles supported on stacked wire mesh cartridges. Activity and stability in diesel soot combustion

In this work, Co3O4 nanoparticles were successfully synthesized by precipitating a precursor salt solution in the form of microdroplets generated by a nebulizer, as an efficient, fast and low-cost approach. After drying and calcination, synthesized particles were deposited on stacked wire mesh monoliths by immersing the structures in a suspension containing synthesized Co3O4 particles and commercial ceria nanoparticles as a binder. These structured catalysts were evaluated for the combustion of diesel soot which constitutes a crucial step in the regeneration of catalytic particulate filters (CDPFs). Thermal and mechanical stability of Co,Ce washcoated monoliths were investigated. For this, successive catalytic evaluations of the structured system, with intermediate treatments at 900 °C (accelerated aging), were carried out indicating a very good activity and stability of the catalysts developed. Adherence tests showed good adhesion of the catalytic layer to the metallic substrate. Fresh and aged catalysts were fully characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Laser Raman Spectroscopy (LRS) and Temperature-Programmed Reduction (TPR). It was found that the catalytic coating resulted composed of nanometric CeO2 and Co3O4 along with chromium, iron and manganese oxides coming from the migration of the metallic substrate, in the catalytic cartridge calcined at 600 °C. Despite after calcination at 900 °C spinels of Co, Fe, Cr and Mn were observed, these oxides did not significantly affected the catalytic activity. Although this aging treatment at 900 °C was severe and is not expected under real conditions, it highlights the potential application of the catalytic metallic cartridges here developed.

Catalytic diesel soot combustion over FeCo2O4 monolithic catalysts with different morphologies

Herein, four different morphologies of FeCo2O4 monolithic catalysts were prepared on three-dimensional macroporous (3-DM) Ni foam substrate by a facile hydrothermal route, including nanowire (FeCo-NW), nanobrush (FeCo-NB), nanosheet (FeCo-NS) and porous nanosheet (FeCo-PNS). The contact efficiency between these catalysts and soot particulates was calculated, respectively. The relationships between catalyst morphology and reactivity for soot combustion were analyzed from the perspective of contact efficiency. Among these catalysts, the FeCo-NW displays the highest catalytic activity, with the T10 = 351 °C, SCO2 = 100 %, which is ascribed to its outstanding contact efficiency with soot (60), optimal intrinsic activity (TOF = 1.77 × 10−5 s−1), ample surficial active species and exceptional reducibility. In the O2 atmosphere, the catalytic performance of FeCo2O4 catalysts in different temperature ranges is affected by different factors. At low temperatures (T < 380 °C), the catalytic activity is mainly influenced by contact efficiency. At high temperatures (T = 380–500 °C), the catalytic activity is comprehensively determined by contact efficiency, redox properties, surface active species and inherent activity.

Electricity-pulse-sparked rapid combustion of diesel soot on conductive LaCoO3 catalysts

In coping with the rapid emission of massive soot particles during the cold starts of diesel vehicles, achieving rapid catalytic soot combustion at low temperatures is a formidable challenge. Herein, we developed an electricity-pulse-sparked catalysis (EPSC) strategy on a conductive LaCoO3 perovskite catalyst, creating instantaneous soot combustion. As soon as 800 J of electricity pulse is applied, approximately 80 % of soot is combusted within 1 min at <300 °C, exhibiting the higher reaction rates (180−1300 µmol gcat−1 s−1) and energy efficiencies (18−100 gsoot kWh−1) than previously reported results for catalytic soot combustion. Moreover, the EPSC eliminates the gap of contact between soot and catalyst that is a longstanding bottleneck for the specific solid (soot)-solid (catalyst)-gas (O2) reaction, which can be synchronized with the frequently engine start/stop operations, demonstrating potential to address the challenges of soot emissions for hybrid powers.

Nanostructured Pr-Rich CexPr1-xO2-δ Mixed Oxides for Diesel Soot Combustion: Importance of Oxygen Lability.

Soot combustion experiments with 5%O2/He were conducted using model soot, and four distinct compositions of CexPr1-xO2-δ oxides of varying nominal cerium compositions (x = 0, 0.2, 0.3, and 1) were prepared. The catalyst samples were comprehensively characterized using techniques such as XRD, Raman spectroscopy, HR-TEM, N2 adsorption at -196 °C, XPS, O2-TPD, H2-TPR, and work function measurements. The Pr-rich compositions, ranging from Ce0.3Pr0.7O2-δ to PrO2-δ, resulted in a significant increase in the total evolved O2 amounts and enhanced catalyst reducibility. However, a decrease in the textural properties of the catalysts was noted, which was particularly important for the pure praseodymia under the synthesis route conducted. The catalytic activity was investigated under the two following contact modes of mixing between soot and catalyst: loose and tight. The results revealed that the catalytic performance is associated with the surface contact in tight contact mode and with the combination of surface/subsurface/bulk oxygen mobility and the BET surface area in loose contact mode. Notably, the temperatures estimated at 10% and 50% of the conversion (T10 and T50) parameters were achieved at much lower temperatures than the uncatalyzed soot combustion, even under loose contact conditions. Specifically, the 50% conversion was achieved at 511 °C and 538 °C for Ce0.3Pr0.7O2 and Ce0.2Pr0.8O2, respectively. While no direct correlation between catalytic activity and work function was observed, a significant relationship emerges between work function values and the formation of oxygen vacancies, whatever the conditions used for these measurements. On the other hand, the ability to generate a high population of oxygen vacancies at low temperatures, rather than the direct activation of gas-phase O2, influences the catalytic performance of Pr-doped ceria catalysts, highlighting the importance of surface/subsurface oxygen vacancy generation, which was the parameter that showed a better correlation with the catalytic activity, whatever the soot conversion value or the mode of contact considered.

Diesel soot combustion in air-NO environment: Evolution of functional groups on soot surfaces

It is inevitable for NO to be involved in the soot combustion in diesel particulate filters (DPFs), so giving full play to the NO oxidation activity is one of the most effective means to improve the DPF regeneration performance. In this work, based on the results of programmed temperature oxidation (TPO) experiments, Fourier transfer inference spectroscopy, and X-ray photoelectron spectroscopy, the evolution of surface functional groups was seriously analyzed to explore the soot oxidation mechanism. The results revealed that with the presence of NO in the air atmosphere, the concentration of -ONO2 groups showed an increasing trend in the early oxidation stage of 0–20 % oxidation degree (OD) and then slowly decreased during 20–80 % OD, while the variations in CH functional group concentration were directly related to the concentration NO in the air atmosphere. COO functional group is easy to decompose, and NO promotes COO's generation and decomposition. The sp3/sp2 hybrid ratio is strongly correlated with CO (carbon‑oxygen double bond), but the content of CO is also affected by the desorption of COO functional groups. It is worth noting that when the soot oxidation degree is at 50 %–80 % OD, CO groups are converted to CO functional groups.

Effect of ash participation on the catalytic activity of as-prepared catalysts to promote diesel soot combustion

This paper studies the effects of ash species and ash aging deposition on the physical and chemical properties of KC catalysts. By thermogravimetric analysis (TGA), the pure KC catalyst has good stability and catalytic activity at 600 °C. In the loosely contacting soot particles (PU)/ash/KC mixtures, the negative effect of ash on KC catalytic soot oxidation is relatively weak. The addition of ash makes the active site areas between PU and KC catalyst lose contact without changing the physicochemical properties of the catalyst. By contrast, the ash aging deposition on KC at 400 °C has an obviously negative effect on the soot combustion catalyzed by KC, because ash aging deposition leads to enormous changes in the chemical properties and catalytic activity of KC. This finding is consistent with characterization analyses such as XRD, SEM, XPS and Raman. Ash aging deposition destroys the KC structure and reduces the activity of KC to catalyze soot oxidation, and CaSO4 has the greatest effect on the oxidation activity. Consequently, ash aging deposition causes structural property damage of as-prepared catalysts, leading to the failure of CDPF catalytic layer. This study provides a new idea for the selection and optimization strategy of catalysts in CDPF.

Diesel soot combustion in air-NO environment: Evolution of soot physical properties and fragmentation characteristics

Since the oxidation activity of nitrogen oxides on soot is obviously higher than that of O2, it is one of the most effective means to improve soot combustion in diesel particulate filter (DPF) by fully utilizing the oxidation activity of nitrogen oxides in diesel exhaust. This paper investigated the physical properties (i.e. morphology, primary particle diameter, fractal dimension and nanostructure) and oxidation-induced fragmentation characteristics of diesel exhaust soot particles during oxidation degrees (0 %, 20 %, 50 % and 80 %) in different atmospheres (air, air-1000 ppm NO and air-2000 ppm NO). The results showed that during the oxidation process the variation trends of soot morphology in air and air-NO environments were similar, while the number and size of primary particles in an aggregate decreased and the fractal dimension of the aggregate increased with the presence of NO in air atmosphere. With the progress of oxidation, the nanostructure of soot particles became more ordered, while this variation trend was slowed down when NO was added to the air atmosphere. This is because soot particles oxidized in air-NO atmospheres showed less probability of internal oxidation but more external oxidation than those in air atmosphere. Over the oxidation process, the soot aggregate fragmentation rate presented a decreasing variation trend under each oxidizing atmosphere, with a higher aggregate fragmentation rate and more apparent variations in air-NO atmospheres. Moreover, in the air atmosphere, the probability of primary soot particle fragmentation showed a consistent upward trend, while the addition of NO slowed down this trend and showed an upward trend in stages 1(0 % ∼ 20 %) and 2(20 % ∼ 50 %), but a downward trend in stage 3(50 % ∼ 80 %). This suggests that the addition of NO reduces the probability of oxidants (especially O2) entering the particles, which would lead to a decrease in the probability of primary soot fragmentation caused by internal oxidation.

Kinetic Analysis of Devolatilized Diesel-Soot Oxidation Catalyzed by Ag/Al2O3 and Ag/CeO2 Using Isoconversional and Master-Plots Techniques.

This work presented the kinetic analysis of devolatilized diesel-soot combustion accelerated by Ag/Al2O3 and Ag/CeO2 catalysts. Isoconversional and master-plots techniques were employed to estimate activation energy and identify the reaction model. The apparent activation energy of uncatalyzed soot oxidation was 101.85 kJ/mol, and it was reduced to 61.85 and 82.78 kJ/mol for the combustion catalyzed by Ag/Al2O3 and Ag/CeO2, respectively. The reaction-order model, f(α) = (1- α)n, with n of 1.4, 1, and 1 showed the best fit for the uncatalyzed soot oxidation and soot oxidation catalyzed by Ag/Al2O3 and Ag/CeO2, respectively. The proposed single-step reaction models were quite capable of reproducing experiments for the uncatalyzed soot oxidation and soot oxidation catalyzed by Ag/CeO2. In the presence of Ag/Al2O3, the oxidation rate at the first 20% of conversion was faster than the 1st-order reaction reflecting that the soot was rapidly oxidized by highly active species generated by Ag/Al2O3. The oxidation of the remaining soot closely followed the 1st-order reaction mechanism.

Core-shell MnCeO catalysts for NO oxidation and mild temperature diesel soot combustion

Environmental contamination such as soot particles and NO x have aroused extensive attraction recently. However, the main challenge lies in the oxidation of soot at mild temperature with the assistance of NO x . Here, a series of core–shell MnCeO x catalysts were successfully synthesized by hydrothermal method and employed for low-temperature catalytic oxidation of soot in the presence of NO x . X-ray diffraction (XRD), inductively coupled plasma - optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), N 2 adsorption/desorption, H 2 -temperature programmed reduction (H 2 -TPR), O 2 -temperature programmed desorption (O 2 -TPD), X-ray photoelectron spectroscopy (XPS) and Raman were conducted for identifying the structure of prepared catalysts and investigating redox properties of the core–shell mixed oxide, which shows excellent performance for NO oxidation and the T 50 about 350 °C for soot oxidation. Besides, soot particle is oxided at 304 °C in presence of NO, while T 50 augments up to 340 °C in the absence of NO. In the NO x -assisted elimination cases of soot, NO 2 generated from NO in emission gas is generally reckoned as a facilitator which significantly reduces ignition temperature of soot particles. Possible catalytic mechanism over core–shell MnCeO x catalysts is also proposed in this paper. Core-shell MnCeO x catalysts with different Mn contents were successfully synthesized through hydrothermal method and they exhibit superior catalytic ability for soot oxidation. This work achieves NO x -assisted soot combustion at mild temperature and can be used as alternative option in catalytic processes of soot particles. • A series of MnCeO x catalysts were successfully synthesized by hydrothermal method and the core-shell structure is confirmed. • MnCeO x catalysts showed superior catalytic capability for low-temperature catalytic oxidation of soot in the presence of NO x and the lowest catalytic temperature was achieved at 304 °C. • Possible catalytic mechanism over core-shell MnCeO x catalysts was also proposed.

Synthesis of Co,Ce Oxide Nanoparticles Using an Aerosol Method and Their Deposition on Different Structured Substrates for Catalytic Removal of Diesel Particulate Matter

The synthesis of Co and Ce oxide nanoparticles using precipitation of precursor salt solutions in the form of microdroplets generated with a nebulizer proved to be an efficient, fast and inexpensive method. Different morphologies of single oxides particles were obtained. Ceria nanoparticles were almost cube-shaped of 8 nm average size, forming 1.3–1.5 μm aggregates, whereas cobalt oxide appeared as rounded-edged particles of 37 nm average size, mainly forming nanorods 50–500 nm. Co3O4 and CeO2 nanoparticles were used to generate structured catalysts from both metallic (stainless steel wire mesh monoliths) and ceramic (cordierite honeycombs) substrates. Ceria Nyacol was used as a binder to favor the anchoring of catalytic particles thus enhancing the adhesion of the coating. The resulting structured catalysts were tested for the combustion of diesel soot with the aim of being used in the regeneration of particulate filters (DPFs). The performance of these structured catalysts was similar to or even better than that exhibited by the catalysts prepared using commercial nanoparticles. Among the catalysts tested, the structured systems using ceramic substrates were more efficient, showing lower values of the maximum combustion rate temperatures (TM = 410 °C).

Synergistic Effect of Pt and Dual Ni/Co Cations in Hydrotalcite-Derived Pt/Ni1.5Co0.5AlO Catalysts for Promoting Soot Combustion

In this article, the catalysts of hydrotalcite-derived Ni1.5Co0.5AlO nanosheet-supported highly dispersed Pt nanoparticles (Ptn/Ni1.5Co0.5AlO, where n% is the weigh percentage of the Pt element in the catalysts) were elaborately fabricated by the gas-bubble-assisted membrane--reduction method. The specific porous structure formed by the stack of hydrotalcite-derived Ni1.5Co0.5AlO nanosheets can increase the transfer mass efficiency of the reactants (O2, NO, and soot) and the strong Pt-Ni1.5Co0.5AlO interaction can weaken the Ni/Co-O bond for promoting the mobility of lattice oxygen and the formation of surface-oxygen vacancies. The Ptn/Ni1.5Co0.5AlO catalysts exhibited excellent catalytic activity and stability during diesel soot combustion under the loose contact mode between soot particles and catalysts. Among all the catalysts, the Pt2/Ni1.5Co0.5AlO catalyst showed the highest catalytic activities for soot combustion (T50 = 350 °C, TOF = 6.63 × 10-3 s-1). Based on the characterization results, the catalytic mechanism for soot combustion is proposed: the synergistic effect of Pt and dual Ni/Co cations in the Pt/Ni1.5Co0.5AlO catalysts can promote the vital step of catalyzing NO oxidation to NO2 in the NO-assisted soot oxidation mechanism. This insight into the synergistic effect of Pt and dual Ni/Co cations for soot combustion provides new strategies for reducing the amounts of noble metals in high-efficient catalysts.

Diesel soot combustion over ceria catalyst: Evolution of functional groups on soot surfaces

The use of ceria catalyst is a common way to promote the soot combustion during DPF regeneration, due to the superior capability to store and release oxygen. In this work, the oxidation behavior and evolutions of surface functional groups have been critically discussed to reveal the mechanism of soot catalytical oxidation, based on the results derived from temperature-programmed-oxidation (TPO) experiments, X-ray photoelectron spectroscopy, Fourier Transfer Inferred spectrometer, and Raman scattering spectrometer. Before the TPO test, the soot samples with and without ceria were annealed at up to 500℃ in pure N2 gas. During the thermal annealing, the reaction between soot and desorbed lattice oxygen in ceria leads to damage of the graphitic network and proliferation of the strongly oxidized OCO groups, defects, and disorder structure on soot surface. In consequence, the onset temperature for the mixture of diesel soot and ceria in loose-contact condition slightly elevates than the pure diesel soot. At initial soot catalytical oxidation, ceria enhances the consumption of amorphous carbon and generation of sp3 hybridized carbon. As the oxidation process evolves, ceria gives a boost to the complete saturation of C vacancy and the generation of larger O groups on soot surfaces. Meanwhile, the damage of the PAHs matrix occurs with the assistant of ceria catalyst, probably by facilitating the O desorption on the basal-plane C atoms. All these differences induced by ceria facilitate the oxidation reactions in the subsequent phases.

Insight into catalytic activity of K-Ce catalysts and K-Ce based mixed catalysts on diesel soot combustion

A series of K-Ce catalysts with different K/(K+Ce) molar ratios are successfully prepared by hydrothermal method, to optimize catalyst diesel particlate filter (CDPF) regeneration efficiency of soot elimination. The K-Ce catalyst is an excellent promoter for soot combustion by thermogravimetric analysis (TGA), and the KC-0.2 catalyst has the best catalytic activity because proper K ions lead to more oxygen vacancies and improve contact efficiency with soot. This result corresponds well to characterization analysis, such as XRD, SEM and XPS. In a 10%O2/90%N2 atmosphere, the KC-0.2 has the highest average mass loss rate (Wmean), maximum mass loss rate (Wmax) and combustion stability index (Rw). The weight ratios of the soot/KC-0.2 mixture are less than 1:10, making catalytic oxidation easier for the soot. Thermal aging in static air at 600 °C is used to investigate the catalytic stability of KC-0.2, and the TGA results show that KC-0.2 has good stability at temperatures lower than 600 °C. Compare to KC-0.2, the KC-0.2 based mixed catalyst with ZrO2 participation is further prepared by mechanical method and has better catalytic activity because the presence of Zr enhances redox surface sites of catalyst. This facilitates the exploration of novel catalysts through combinatorial catalysis.

Ceramic Papers as Structured Catalysts: Preparation and Application for Particulate Removal

Fibers represent a type of structure of great interest in catalysis since they combine high area to volume ratio and can be fabricated from many types of materials, such as ceramic oxides, polymers, and alloys. They can be used in isolated form or structured, as in the case of the ceramic papers synthesized in this work, following a modified papermaking technique. The addition of cationic and anionic polyelectrolytes improved the retention of ceramic fibers during the ceramic paper formation stage by adsorption processes, through the formation of floccules. In the complex aqueous system containing charged macromolecules, the amounts of polyelectrolytes to be added were determined by titrations. To enhance mechanical properties of ceramic papers, different classes of nanoparticle suspensions can be used as binders. As a novel alternative, we have used different borate-type compounds. Among them, we selected natural ulexite, which was purified and used as a binder of ceramic fibers. In order to improve mechanical resistance and flexibility, measured from tensile indexes and elastic module, the amounts of NaCaB5O6(OH)6.5H2O and the calcination temperature were varied. In this contribution, to take advantage of the unique characteristics of the ulexite-containing ceramic papers, they were impregnated with Co,Ce and Co,Ba,K and tested for diesel soot combustion.

Insight into high-performance of La–Ce–MnOx oxides with different calcination temperatures for diesel soot combustion

ABSTRACT A series of La–Ce–MnOx catalysts derived from the precipitation of acetate salt and ammonium carbonate were calcined at different temperatures and applied for the catalytic oxidation of soot from diesel exhausts. The structure states of the as-prepared catalysts and catalytic behaviour for soot oxidation were studied by many characterization techniques such as XRD, XANES, N2 adsorption–desorption, TPR, O2-TPD, XPS and TGA. XANES results display most Mn species are Mn4+ when the samples are calcined at 500 and 600°C. However, for MCLa-700 and MCLa-800 catalysts, the predominance valence is 3+ ions. The MCLa-500 and MCLa-600 catalysts possess higher concentrations of surface active oxygen evidenced by H2-TPR and soot-TPR. Therefore, the combustion rate of soot over MCLa-600 catalyst is remarkably increased with the T10, T50 and T90 at 318°C, 360°C and 388°C under NOx atmosphere respectively.

Catalytic activity and influence factors of Mn-Ce mixed oxides by hydrothermal method on diesel soot combustion

To solve the soot elimination and optimize catalyst diesel particulate filter (CDPF) regeneration strategies, a series of Mn-Ce catalysts with different Mn/(Mn+Ce) molar ratios are successfully synthetized by hydrothermal method and the complete catalytic oxidation of diesel engine soot are investigated. Compare to CeO2 and MnO2, the catalytic promotion on soot combustion of Mn-Ce catalysts is more excellent by thermogravimetric experiments due to their better ability to activate oxygen species, which is consistent with results in characterization analysis. Among as-prepared catalysts, MC-0.40 has the best catalytic activity with the lowest starting temperature (Ts), peak temperature (Tp) and largest comprehensive combustion index (S) both in O2/N2 and NO/O2/N2 atmosphere. Influence factors on catalytic performance are studied. Weight ratios of soot/MC-0.40 catalyst are suitable at the range of 1:9–1:13, which makes soot combustion more easily. Ashes in the reaction process show adverse effects due to their ability to increase ignition point by inhibit heat and oxygen transfer. Mn-Ce catalysts are more sensitive and show better catalytic activity in NO atmosphere because of generations of abundant adsorbed species and NO adsorption/desorption. The three consecutive cycles of MC-0.40 catalyst are performed to study the catalytic stability, and thermogravimetric curves show that the potential reusability of MC-0.40 catalyst can be relatively accepted in soot combustion.

One step citric acid-assisted synthesis of Mn-Ce mixed oxides and their application to diesel soot combustion

Mn-Ce catalysts were prepared by a one-step synthesis method using citric acid, and were characterized by X-ray diffraction, CO temperature-programmed reduction, laser Raman spectroscopy and X-ray photoelectron spectroscopy. These catalysts were applied to the catalytic combustion of diesel soot in the presence of nitric oxide. A remarkable influence of the ratio of precursors and the method of synthesis on the physicochemical properties and subsequent catalytic activity was evidenced. The mixed oxides had higher activities than the individual ones, showing a synergistic effect whereby the catalyst with Mn/(Mn + Ce) = 0.1 had the lowest temperature of the maximum combustion rate.Mechanical mixtures of oxides were also prepared in order to better understand the synergistic effect observed. The main TPO peak was located at a similar temperature for both methods of synthesis. However, the TPO profiles of the catalysts synthesized by mechanical mixing had a shoulder at around 420 °C, which was more evident for catalysts prepared with lower Mn contents. This fact could be related to the coexistence of different MnOx species, as demonstrated by XRD, which exhibited different catalytic performances on oxidation reactions. The formation of a solid solution between Mn and Ce oxides for a ratio of Mn/(Mn + Ce) < 0.25 was observed, which enhanced the Ce4+ ↔ Ce3+ redox process. It was observed that both the coexistence of Mn2O3 and Mn3O4 at high concentrations and the formation of a solid solution strongly favored the oxidation of diesel soot, obtaining lower values of maximum combustion rate temperature.

In situ growth of ceria nanofibers on cordierite monoliths for diesel soot combustion

The direct in situ growth of CeO2 nanofibers was performed by hydrothermal synthesis on cordierite monoliths for the diesel soot combustion reaction. They were characterized by SEM (Scanning Electron Microscopy), XRD (X-Ray Diffraction), LRS (Laser Raman Spectroscopy), textural analysis and adherence test. The mechanical stirring during the synthesis was essential to obtain the desired nanofibers, as well as a homogeneous coverage throughout the monolith with a very good anchoring to the substrate. The CeO2 nanoarray monolithic catalyst exhibited a catalytic oxidation activity similar to that obtained for bare CeO2 fibers (temperature of maximum soot combustion rate, TM = 428 °C). Raman in situ experiments along with kinetic analysis indicated that the amorphous fraction of carbon burned more easily than the graphitic fraction. Successive reaction runs indicated that the nanoarray of CeO2 fibers partially deactivated, especially after 800 °C. However, TM was 477 °C, being this last value about 100 °C lower than the non-catalytic soot combustion temperature.

Ozone-assisted diesel soot combustion over Mn2O3 catalysts: A tandem work of different reactive phases

Catalytic diesel particulate filtration (CDPF) assisted by ozone is a promising strategy for soot elimination at exhaust temperatures. It is important yet challenging to utilize the strongly oxidizing ozone while prevent its escape. In this study, rod-like Mn2O3 catalysts with high ozone decomposition ability were proved as an ideal tool for such a task. With thorough characterizations and temperature-programmed oxidation tests in selected atmospheres, triple low-temperature incubation effects were ascribed to the (catalytic) decomposition of ozone, including oxidizing NO to NO2, breeding surface oxygen complexes on soot and surface manganese species on the catalyst. Superior soot elimination efficiency (T10 = 267 °C, T50 = 392 °C, TOFMn = 1.0 × 10−2 s−1) was achieved by the tandem work of NO2 (at ∼200–500 °C), NO2-induced nitrates/nitrites (at ∼200–300 °C), surface manganese oxides (at ∼300–400 °C) and O2 (at ∼400–500 °C), indicating the coupling of ozone and transition metal oxides may lead to reliable and cost-effective CDPF systems.

Catalytic Activity and Influence Factors of Mn-Ce Mixed Oxides by Impregnation Method on Diesel Soot Combustion

Catalytic Activity and Influence Factors of Mn-Ce Mixed Oxides by Impregnation Method on Diesel Soot Combustion