Figure - available from: Scientific Reports
This content is subject to copyright. Terms and conditions apply.
Microstructure of the soot and ash in the CDPF with different aging mileage, (a) soot and ash in the CDPF after 30,000 km’ aging, (b) ash after combustion in the CDPF after 30,000 km’ aging, (c) soot and ash in the CDPF after 60,000 km’ aging, (d) ash after combustion in the CDPF after 60,000 km’ aging.
Source publication
Catalyzed diesel particulate filters (CDPFs) have been widespread used as a technically and economically feasible mean for meeting increasingly stringent emissions limits. An important issue affecting the performance of a CDPF is its aging with using time. In this paper, the effects of noble metal loadings, regions and using mileage on the aging pe...
Citations
... Diesel particulate matters (PM) pose a serious threat to the atmospheric environment and human health [1][2][3]. A catalytic diesel particulate filter (CDPF) has been considered as an efficient way to reduce diesel PM emissions [4,5]. PM from diesel exhaust gases can be removed through two processes. ...
A series of Ag-modified manganese-mullite (SmMn2O5) catalysts with different Ag contents (1, 3, and 6 wt.%) were prepared via a citric acid sol–gel method for catalytic soot oxidation. The catalysts were characterized by powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy analysis (HRTEM), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). The soot oxidation activity of the mullite was significantly promoted by the addition of silver and affected by the loading amount of the metal. Herein, the influences of silver loading on the metal size distribution and its interactions with the mullite were studied. Based on these characterizations, a possible soot oxidation reaction mechanism was proposed for silver-modified SmMn2O5.
... Which is sprayed upstream toward the flue gas inside the SCR system [51]. This process of NOx reduction to N 2 ensues in three steps reactions [52]. ...
Oxides of nitrogen (NO x) emissions have always been considered as the primary concern for the development of diesel engines. Several post-treatment technologies have also been developed to fulfil the stringent standards for NOx emissions that cannot be controlled by fuel composition and combustion reaction. At present, the after-treatment technologies employed include Selective Catalytic Reduction (SCR), Lean NOx Traps and SCR filtering. The current review article summarizes the investigations conducted earlier about the reduction of NOx emissions from lean-burn engines and discusses the benefits and limitations of different types of SCRs. Among the available technologies, the urea SCR process is ultimately the most efficient process using Ad blue technology. Urea SCR process uses NH 3 reduction agents to achieve 98% conversion efficiency. The article discussed some of the operating parameters such as the nature of catalytic material, the range temperature of the catalyst and the mixing of NH 3 and NOx. Hybrid SCR such as the metals-impregnated SCR (M-SCR, HC-SCR, SCR + LNT) moderately increases the catalytic activity and converts the exhaust gas into less harmful gases even at low temperature. The novelty of the work, debates about the outrivaling importance of oxidation catalyst of the modern diesel exhaust purification systems, techniques for enhancement and the optimization of oxidation catalysts that are aimed at NOx and hydrocarbon conversion and the methods for reducing the Platinum Group Metal (PGM) content in these catalytic systems via combination devices for thermal energy and further optimization and material cost at-tenuation. There exists a requisite for continuous investigation of PM control technology that comprises of regenerating systems to reduce the complexity of these systems and concomitant fuel economic penalties. Future research works should be conducted extensively with different additives, substrate materials, regenerating systems , and controls to develop optimal devices that are capable of reducing the diesel particulate emissions levels.
... At the same time, the low temperature can reduce the thermal shock to the material and prolong the service life of CDPF (Fang et al. 2019). The catalytic method is affected by several disadvantages: the reaction conditions are complex when driving, which is very different from the stable conditions in the laboratory; Poor contact of soot / catalyst, and the reaction speed cannot keep up with the deposition speed; The exhaust temperature range is wide, which requires high catalytic activity and heat resistance of the catalyst at low temperature (Zhang et al. 2020g). In order to achieve better filtration and regeneration performance, the composition and ratio of catalyst as well as PM to catalyst contact modes are key (Guo et al. 2013) (Sabet Sarvestani et al. 2020). ...
Diesel particulate filter (DPF) is considered as an effective method to control particulate matter (PM) emissions from diesel engines, which is included in the mandatory installation list by more and more national/regional laws and regulations, such as CHINA VI, Euro VI, and EPA Tier3. Due to the limited capacity of DPF to contain PM, the manufacturer introduced a method of treating deposited PM by oxidation, which is called regeneration. This paper comprehensively summarizes the most advanced regeneration technology, including filter structure, new catalyst formula, accurate soot prediction, safe and reliable regeneration strategy, uncontrolled regeneration and its control methods. In addition, due to the change of working conditions in the regeneration process, the additional emissions during regeneration are discussed in this paper. The DPF is not only the aftertreatment device but also can be combined with diesel oxidation catalyst (DOC), selective catalytic reduction (SCR) and exhaust recirculation (EGR). In addition, the impact of DPF modification on the original system of some old models has been reasonably discussed in order to achieve emission targets.
... Consequently, vehicle emission regulations are becoming more demanding, and the use of after-treatments systems is mandatory. Thus, a combination of diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) is employed as diesel after-treatment system to meet emission regulations [8,9]. However, DPF is made up of a ceramic honeycomb monolith coated with noble metals (Pt, Pt/Pd or Pd/Rh) [8,9], being these PGMs scarce and expensive [10,11]. ...
... Thus, a combination of diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) is employed as diesel after-treatment system to meet emission regulations [8,9]. However, DPF is made up of a ceramic honeycomb monolith coated with noble metals (Pt, Pt/Pd or Pd/Rh) [8,9], being these PGMs scarce and expensive [10,11]. ...
In this work, it is analyzed the effect of the partial substitution of Fe by Ni in a BaFeO 3 perovskite to be used as the catalyst for NO x -assisted diesel soot oxidation. A series of BaFe 1−x Ni x O 3 (x = 0, 0.2, 0.4 and 0.8) catalysts have been synthesized by using the sol–gel method. The catalysts have been characterized by ICP-OES, XRD, XPS, O 2 -TPD, H 2 -TPR- and TEM. The catalytic activity for NO to NO 2 oxidation and NO x -assisted diesel soot oxidation have been determined by Temperature Programmed Reaction experiments (NO x -TPR and Soot-NO x -TPR, respectively) and by isothermal reaction at 450 °C. Ni seems not to be inserted in the BaFeO 3 perovskite and, instead of that, BaNiO 3 perovskite and NiO are detected on the surface of the perovskite BaFeO 3 . XPS data reveal the coexistence of Fe(III) and Fe(IV) on the catalyst’s surface (being Fe(III) the main oxidation state) and the presence of oxygen vacancies. All catalysts are active for NO oxidation to NO 2 , showing BaFeO 3 and BaFe 0.6 Ni 0.4 O 3 the best catalytic performance. BaFe 0.6 Ni 0.4 O 3 shows the highest proportion of nickel on surface and it combines the highest activity and stability for NO x -assisted diesel soot oxidation. Also, this catalyst presents the highest initial soot oxidation rate which minimizes the accumulation of unreacted soot during reaction.
... A combination of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) has been used as a diesel engine after-treatment system to meet emission regulations [9]. Particularly, DPFs are manufactured by coating Pt or Pt and Pd on their walls [10]. ...
... Particularly, DPFs are manufactured by coating Pt or Pt and Pd on their walls [10]. The partial exchange of Pt by Pd or Rh has been reported as a strategy to improve the redispersion of Pd particles and reduce costs [9,11]. ...
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.
Increasing the contact efficiency and improving the intrinsic activity are two effective strategies to obtain efficient catalysts for soot combustion. Herein, the electrospinning method is used to synthesize fiber-like Ce-Mn oxide with a strong synergistic effect. The slow combustion of PVP in precursors and highly soluble manganese acetate in spinning solution facilitates the formation of fibrous Ce-Mn oxides. The fluid simulation clearly indicates that the slender and uniform fibers provide more interwoven macropores to capture soot particles than the cubes and spheres do. Accordingly, electrospun Ce-Mn oxide exhibits better catalytic activity than reference catalysts, including Ce-Mn oxides by co-precipitation and sol-gel methods. The characterizations suggest that Mn3+ substitution into fluorite-type CeO2 enhances the reducibility through the acceleration of Mn-Ce electron transfer, improves the lattice oxygen mobility by weakening the Ce-O bonds, and induces oxygen vacancies for the activation of O2. The theoretical calculation reveals that the release of lattice oxygen becomes easy because of a low formation energy of oxygen vacancy, while the high reduction potential is beneficial for the activation of O2 on Ce3+-Ov (oxygen vacancies). Due to above Ce-Mn synergy, the CeMnOx-ES shows more active oxygen species and higher oxygen storage capacity than CeO2-ES and MnOx-ES. The theoretical calculation and experimental results suggest that the adsorbed O2 is more active than lattice oxygen and the catalytic oxidation mainly follows the Langmuir-Hinshelwood mechanism. This study indicates that electrospinning is a novel method to obtain efficient Ce-Mn oxide.
A novel rotary-type atomic layer deposition (ALD) process for coating platinum thin film on three-dimensional (3D) substrates is demonstrated. High uniformity and conformability of the platinum thin-film deposition on 3D substrates were confirmed, ensuring the controllability of the new ALD technique. The results for this technique surpassed those of the conventional wet method and ordinary atomic layer deposition, which both have a limited specific surface area. To demonstrate the application of this new technology, Pt nano-film coated γ-Al2O3 was produced using the rotary-type ALD and applied to diesel oxidation catalysts (DOCs). The produced DOCs showed high Pt content when the number of ALD cycles was increased, and thereby exhibited more complete combustion of gaseous pollutants, such as CO, C3H8, and NO, even at lower temperatures. Pt nano-film deposition by the rotary-type ALD process was first optimised on Si wafer substrates. The process was controlled by four parameters: processing temperature, number of ALD cycles, precursor pulse time, and reactant pulse time. Deposition of the Pt nano-film was mainly determined by the processing temperature and the number of ALD cycles. The average growth per cycle and density of the Pt nano-film were found to be 0.8 Å/cycle and 21.0 g/cm3, respectively. The same procedure and conditions were applied to 3D γ-Al2O3 powder substrates for DOCs, which demonstrated greater conversion performance compared with conventional Pt-used DOCs.
The lifetime and efficiency of diesel particulate filters (DPFs) strongly depend on the proper and periodic cleaning and servicing. Unfortunately, in some cases, inappropriate methods are applied to clean the DPFs, e.g., using air compressors without proper disposal procedures that can have negative impacts on human health, the environment, and DPF’s efficiency. However, there is no information available about the properties of this kind of PM. This research is therefore presented to explore the physicochemical and toxicity properties of aged PM trapped in a DPF (using compressed air for PM sampling) employing STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer for investigating the physicochemical properties, and assays of cell viability, cellular reactive oxygen species (ROS), interleukin-6, and tumor necrosis factor-alpha (TNF-α) for investigating the toxicity properties. Also, analyses from fresh PM samples from the diesel vehicle at two engine speeds are presented. It is found that at a certain/fixed PM number/mass for all three samples tested, the PM from DPF compared with the fresh PM can have both positive (particularly having the lowest water-soluble total carbon ratio) and negative impacts on human health (particularly having the highest cell death rate of 13.4%, ROS, and TNF-α) and the environment.
The literature shows that information about the physical, chemical, and cell toxicity properties of particulate matter (PM) from diesel vehicles is not rich as the existence of a remarkable number of studies about the combustion, performance, and emissions of diesel vehicles using renewable liquid fuels, particularly biodiesels and alcohols. Also, the PM analyses from combustion of spent coffee ground biodiesel have not been comprehensively explored. Therefore, this research is presented. Pure diesel, 90% diesel + 10% biodiesel, and 90% diesel + 9% ethanol + 1% biodiesel, volume bases, were tested under a fast idle condition. STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer were employed for investigating the PM physical and chemical properties, and assays of cell viability, cellular reactive oxygen species, interleukin-6, and tumor necrosis factor-alpha were examined for investigating the PM cell toxicity properties. It is found that the application of both biodiesel and ethanol has the potential to change the PM properties, while the impact of ethanol is more than biodiesel on the changes. Regarding the important aspects, biodiesel can be effective for better human health (due to a decrease in cell death (−60.8%)) as well as good diesel particulate filter efficiency (due to lower activation energy (−7.6%) and frequency factor (−83.2%)). However, despite a higher impact of ethanol on the reductions in activation energy (−24.8%) and frequency factor (−99.0%), this fuel causes an increase in cell death (84.1%). Therefore, biodiesel can be an appropriate fuel to have a positive impact on human health, the environment, and emissions catalysts performance, simultaneously.
