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This paper focuses on the correlation between the oxidative reactivity and electrical properties of soot particles. Soot particles were produced from an n -heptane inverse diffusion flame and were sampled at different heights above the burner (HAB) using a thermophoretic and probe sampling techniques. The electrical properties were characterized by the electrical conductivity and work function, which were evaluated by an atomic force microscopy. The soot reactivity was assessed in terms of activation energy (E a) and characteristic oxidation temperatures, including peak temperature (T P) and burnout temperature (T b), using thermogravimetric analysis. As the soot particles gradually age, they have various electrical conductivity distributions. The average electrical conductivity presents an increase by three orders of magnitude when increasing the HAB from 10 to 60 mm. The work function of bulk soot particles shows an increase with the soot maturation. The soot reactivity gradually reduces during the soot maturation process because the values of E a , T P , and T b show increases with the increase in HAB. For the soot particles, the E a and T p have strongly positive correlations with the work function and with the logarithm of the electrical conductivity. Thus, electrical properties can serve as an indicator of soot reactivity. [Display omitted] • The electrical properties and reactivity of soot particles were assessed. • The electrical conductivity and work function increase as soot particles mature. • Soot reactivity decreases with the increase in logarithm of electrical conductivity. • Soot reactivity decreases with the increase in work function. • Soot electrical properties can serve as an indicator of soot reactivity. [ABSTRACT FROM AUTHOR]

The effect of Pd doping on the NOx removal efficiency and NH 3 selectivity was studied over lean NOx trap LaCo 1- x Pd x O 3 -Ba/Al 2 O 3 -type catalysts. Two catalysts were prepared by the sequential impregnation of 15 wt% of LaCo 1- x Pd x O 3 -type perovskites and 20 wt% of barium over alumina. The results of X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, temperature programmed techniques, UV–vis diffuse reflection absorption spectroscopy, and X-ray photoelectron spectroscopy demonstrated that perovskite and barium grains uniformly distribution over the alumina surface. Cobalt partial substitution by palladium changed the chemical coordination environment, thus leading to the redox properties of perovskites getting different. Moreover, the LaCoO 3 –Ba/Al 2 O 3 catalyst exhibited a high reduction on NOx by H 2 between 450 and 550 °C. Whereas Pd-doped LaCo 0·9 Pd 0·1 O 3 –Ba/Al 2 O 3 catalyst decreased the best activity interval around 100 °C, as well as improved the NH 3 selectivity. The NOx reduction conversion of the LaCo 0·9 Pd 0·1 O 3 –Ba/Al 2 O 3 catalyst increased significantly from 72.9% to around 100% at H 2 /NO ratio = 1, and the production of NH 3 was increased from 20.1% to 58.6% at H 2 /NO ratio = 3. • Novel perovskite-based catalysts were synthesized for excellent textural properties. • Pd changes the chemical environment of the cobalt metal ions and enhances the redox properties of LaCoO 3. • Pd enhances H 2 dissociation thus offering more H ions to promote the NH 3 generation. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) was used to characterize the attractive force, adhesive force and adhesion energy between an AFM probe tip and nanometric soot particle generated by a premixed methane/oxygen flame. Different attractive force distributions were found when increasing the height above burner (HAB), with forces ranging from 1.1–3.5 nN. As the HAB was increased, the average attractive force initially increased, briefly decreased, and then underwent a gradual increase, with a maximum of 2.54 nN observed at HAB = 25 mm. The mean adhesive force was 6.5–7.5 times greater than the mean attractive force at the same HAB, and values were in the range of 13.5–24.5 nN. The adhesion energy was in the range of 2.0–5.6 × 10 −17 J. The variations observed in the average adhesion energy with increasing HAB were different from those of the average adhesion force, implying that the stretched length of soot particles is an important factor affecting the average adhesion energy. The Hamaker constants of the soot particles generated at different HABs were determined from AFM force-separation curves. The average Hamaker constant exhibited a clear correlation with the graphitization degree of soot particles as obtained from Raman spectroscopy. [ABSTRACT FROM AUTHOR]

This paper reports the effect of post-injection on pollutant emissions from a four-cylinder, direct-injection diesel engine fueled with biodiesel. Characteristics of exhaust pollutants were measured and evaluated for different main-post intervals (MPIs) and post-injection rates (PIRs). Measurements included emissions of carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NO x ) and particulate matter (PM), the particle number concentration distribution, and the reactivity and graphitization degree of the soot particles. Increasing the MPI or PIR increased the emissions of CO and THC but decreased those of NO x . At both low and high MPI values, higher PM emissions and particle number concentrations were observed for the 12 and 20% PIRs. At a PIR of 4%, PM emissions and particle number concentration increased with the increase in MPI. The size distributions of exhaust particulates exhibited a trimodal character under the applied operating conditions. The particle geometric mean diameter decreased with the increase in MPI, probably as a result of an increased yield of soluble organic compounds. Post-injection significantly impacted the reactivity of emitted soot particles, as evidenced by changes in the graphitization degree of soot. [ABSTRACT FROM AUTHOR]

This work studied the physicochemical characteristics of exhaust particles from a 1.48 L SIDI engine operating at different air–fuel ratios (AFRs). The morphology, fractal dimension, size and nanostructure were characterized using high-resolution transmission electron microscopy (HRTEM) in conjunction with electron energy-loss spectroscopy. The results indicate that SIDI aggregate particles produced at varying AFRs exhibit different morphologies. TEM images show that the aggregates obtained at an AFR of 14.7 are more compactly clustered than those generated under fuel-rich and fuel-lean conditions. The fractal dimension of SIDI aggregates at an AFR of 14.7 is found to be 2.21, a value that is larger than those from other AFRs. The primary particle sizes are distributed over a wide range of 5–55 nm at all AFRs, although the largest average primary particle diameter is found at an AFR of 14.7. Similar to diesel soot particles, SIDI soot particles also show characteristic shell-core and turbostratic structures at the nanoscale level. At an AFR of 14.7, the soot particles have a relatively short fringe length, a small fringe separation distance and high fringe tortuosity. As the AFR is increased, the sp 2 /sp 3 hybridization ratios first gradually decrease and then increase, with a minimum value of 0.156 at AFR = 14.7. SIDI soot particles are likely more reactive than diesel soot particles because they possess the relatively short fringe length, large separation distance and high tortuosity. [ABSTRACT FROM AUTHOR]

We investigate effects of post injection strategies on regular exhaust emissions and soot particulate matters on in-cylinder emission control. A trade-off relation indicates that CO and THC emissions increase as post injection timing delays, but NOx emission significantly decreases when crank angle intervals increase because of cylinder volume expansion and heat transfer. In PM emission, total particle concentration and particle size distributions indicate that, at early post injection timing, SOF emission is relatively low but soot emission is relatively large caused by high temperature and local lean oxygen conditions. As crank angle intervals increasing, soot emission decreases quickly and becomes insensitive to the post injection timing. When SOF emission has an obvious increasing trend, there is a lowest level for the PM emission at intermediate post injection timing. Moreover, variations for total particle concentration are similar with soot emission at different post injection strategies. Particle size distribution result illustrates that PS is insensitive to post injection timing at different post injection strategies. [ABSTRACT FROM AUTHOR]

This work compared the surface functional group (SFG) types and concentrations and sp 3 /sp 2 hybridization ratios of in-cylinder soot samples generated by a heavy-duty diesel engine when employing n -heptane and a toluene/ n -heptane mixture (20% toluene by volume) as the fuels. In-cylinder soot samples were obtained from a total cylinder sampling system, and the SFGs and sp 3 /sp 2 hybridization ratios were analyzed using Fourier transform infrared and X-ray photoelectron spectroscopy. Despite the differences in fuel formulation, both n -heptane and n -heptane/toluene soot exhibited similar trends in terms of changes in the SFGs concentrations and sp 3 /sp 2 hybridization ratios during the combustion process. However, the addition of toluene to the n -heptane was found to increase the concentrations of all SFGs as well as the sp 3 /sp 2 hybridization ratio. The C OH and C O group concentrations exhibited a bimodal distribution for both the n -heptane and n -heptane/toluene soot throughout the combustion process, with the concentrations peaking in the premixed and diffusion combustion phases, respectively. In contrast, the relative amounts of aliphatic C H groups decreased in the premixed combustion phase, increased in the early diffusion combustion phase, and then decreased in the subsequent combustion phase. The sp 3 /sp 2 hybridization ratios obtained from both fuel soot were observed to initially decrease, then to increase before a decrease during the combustion process. There was a definite correlation between the sp 3 /sp 2 hybridization ratio and the relative concentration of aliphatic C H groups. [ABSTRACT FROM AUTHOR]

In this paper, the morphology, attractive force ( F at ), adhesive force ( F ad ) and Young's modulus ( E Y ) of diesel in-cylinder soot particles sampled by a total cylinder sampling system were studied using atom force microscopy. In each combustion phase, the equivalent diameter ( ED ), F at , F ad , adhesion energy and E Y present broad distributions. The pattern of ED distribution in the late combustion phase is similar to that in the late diffusion combustion phase, especially in the range of ED < 10 nm, suggesting that the particle size distribution changes little after the late diffusion combustion phase. Most isolated soot particles in each combustion phase possess a very low sphericity ratio. Three types of force curves are discovered for in-cylinder particles, and are introduced to identify the particle types. For the test carbonized soot particles, the SR appears to increase with an increase in ED in each combustion phase, and the AED shows a similar trend to that for all test particles during the combustion process. Due to the presence of plastic deformation for the nascent soot particles and the penetration for the liquid materials during the force measurement, the carbonized primary soot particles are employed for force analysis. As the combustion proceeds, the population-averaged values of F at and F ad show opposite trends; the attractive force, which is mainly driven by the Van der Waals force, gradually decreases. During the combustion process, the population-averaged adhesion energy decreases to a minimum in the late premixed combustion phase after which it then increases. The initial increase in the population-averaged Young's modulus ( AE Y ) is followed by a decrease before gradually increasing again from the early diffusion combustion phase. The AE Y shows a negative correlation with the fringe separation distance in the soot structure. [ABSTRACT FROM AUTHOR]

This work studied the evolution of in-cylinder polycyclic aromatic hydrocarbons (PAHs) in a diesel engine fueled with n -heptane, and explored the effects of adding toluene to n -heptane on in-cylinder PAHs. In-cylinder PAHs were sampled in a direct injection diesel engine using a total cylinder sampling system. PAHs were analyzed by gas chromatography–mass spectrometry with programmed temperature vaporization in the solvent vent mode. For n -heptane, the mass of total in-cylinder PAHs ( Σ M PAHs ) increased in premixed and late diffusion combustion phases, and decreased in early diffusion and late combustion phases. Among the 16 PAHs detected, Naphthalene (Nap) was the most abundant. PAHs with two benzene rings and one five-membered ring, such as Acenaphthylene, Acenaphthene and Fluorene, were also plentiful, implying that PAHs with five-membered ring could play an important role in the growth of in-cylinder PAHs. When adding 20 vol.% toluene to n -heptane, the evolution of ΣM PAHs was varied. The Σ M PAHs for n -heptane/toluene increased in premixed and early diffusion combustion phases, and decreased in late diffusion and late combustion phases. Toluene addition reduced the ΣM PAHs in the premixed combustion phase by up to 48% but increased ΣM PAHs by 30% in the early diffusion combustion phase. In the subsequent combustion phase, the ΣM PAHs was reduced by approximately 67%. For in-cylinder individual PAHs, toluene addition generally reduced the percentages of Nap in ΣM PAHs during the engine combustion process but increased the percentages of larger PAHs, indicating that toluene addition was conducive to the growth of PAHs to form larger PAHs. [ABSTRACT FROM AUTHOR]

• The GDI soot was harvested from a China VI passenger vehicle operated over the WLTC. • The Physicochemical properties of GDI soot were investigated. • The physicochemical properties of the SB4 are similar to those of the GDI soot. • The SB4 and GDI soot have almost the same oxidation reactivity. • The SB4 can serve as a surrogate for GDI soot for oxidation investigations. The purpose of the present study is to understand the physicochemical properties of the GDI soot and determine a GDI soot surrogate for the oxidation investigations. The high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analyzer were used to characterize the soot properties, including the morphology, nanostructure, chemical composition, carbon chemical state and oxidation reactivity. The GDI soot sample was harvested from the gasoline particulate filter equipped on a modern China VI passenger vehicle operated over the Worldwide harmonized Light-duty Test Cycle. The obtained GDI soot comprises large numbers of near-spherical primary particles that cluster together to form aggregates with a mean gyration radius of 123.79 nm, and the mean diameter of primary particles is 27.63 nm. The primary particle exhibits a typical core–shell structure, and the mean values of fringe length, separation distance and tortuosity are 0.836 nm, 0.362 nm and 1.263, respectively. In addition to the carbon element, the oxygen element is another important component of soot particles, accounting for 6.28% of the total number of atoms. The carbon component is mainly composed of sp2 hybridized graphitic carbon and sp3 hybridized aliphatic carbon, and the ratio of sp2/sp3 is 2.02. Moreover, the apparent activation energy of soot sample is determined to be 141.7 kJ/mol. The Special Black 4 (SB4) was assessed as a potential surrogate for the GDI soot. The comparison of physicochemical properties shows that the SB4 and GDI soot have almost the same fractal dimension, gyration radius, primary particle size, fringe length, separation distance, tortuosity, sp2/sp3 ratio and apparent activation energy. The great similarities in physicochemical properties highlight that the SB4 can serve as a good GDI soot surrogate for the soot oxidation investigations. [ABSTRACT FROM AUTHOR]

La 1− x Ce x Mn 1− y Co y O 3 catalysts were prepared by the “glucose method”. The structures and physico-chemical properties for these catalysts were characterized using X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), H 2 -temperature-programmed reduction (H 2 -TPR) and O 2 -tempreature-programmed desorption (O 2 -TPD). Results showed that cerium substitution at the A-site in LaMnO 3 produced a CeO 2 phase. The cobalt can be introduced into the B-site in La 0.8 Ce 0.2 MnO 3 at any substitution ratio because of the similar ionic radii between cobalt and manganese. The catalytic activity for soot combustion in air was evaluated using a TG/DTA analyzer. Cerium substitution at A-site enhances the catalytic activity, while cobalt substitution at B-site inhibits the catalytic activity. The activation energy for soot combustion was calculated using the Horowitz method. The activation energy for non-catalytic soot combustion was 164.1 kJ mol − 1 . The addition of catalysts decreased the activation energy by about 26–63 kJ mol − 1 . Among the applied catalysts, Ce20Mn exhibited the lowest activation energy (101.1 kJ mol − 1 ). [ABSTRACT FROM AUTHOR]

Highlights: [•] Reductions in CBC emissions were assessed for CFT diesel. [•] Significant reductions in emissions of total and individual CBCs were obtained. [•] The percentage reduction in the total CBCs decreased with an increase in engine load. [•] The percentage reduction in the total CBCs increased with increase in engine speed. [•] The ozone formation potential of CBCs emitted was strongly reduced with use of CFT. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zirconia introduction favors copper dispersion and inhibits copper crystallization. [•] Zirconia addition is beneficial to enriching copper species on the ZSM-5 surface. [•] The interaction between copper and zirconium enhances the lattice oxygen and site reducibility. [•] The Cu-Zr/ZSM-5 presents a wide activity window within the range of diesel exhaust temperatures. [ABSTRACT FROM AUTHOR]

The oxidation rates of diesel soot from the combustion chamber of a running diesel engine were calculated based on the particle size distributions at different crank angles. The primary particle diameter and nanostructure of soot were obtained by means of high-resolution transmission electron microscopy (HRTEM). The soot characteristics were also investigated by oxidative thermogravimetry and Raman scattering spectrometry. The results showed the soot nanostructures were dependent on engine operation conditions and combustion phases. The oxidation rates were found to differ by nearly fourfold from that calculated by the Nagle/Strickland-Constable (NSC) model for the soots studied here. The varied oxidation rates were interpreted in terms of differences in nanostructure between the soots. The experimental results were used to modify the NSC model and the fringe length of in-cylinder diesel soot was chosen to describe the influence of graphitisation on the oxidation of soot. The modified NSC model lessened the deviation between measurements and predictions. [ABSTRACT FROM AUTHOR]

Abstract: The nanostructure, fractal dimension and size of in-cylinder soot during diesel combustion process have been investigated for a heavy-duty direct injection diesel engine, using a total cylinder sampling system followed by high-resolution transmission electron microscopy and Raman scattering spectrometry. Different structural organizations of in-cylinder soot are found depending upon the combustion phase. It is revealed that both the fringe tortuosity and separation distance decrease as combustion proceeds, while the mean fringe length increases distinctly from 1.00 to 2.13nm, indicating the soot evolution toward a more graphitic structure during the combustion process. The fractal dimensions of aggregates are in a range of 1.20–1.74 at various crank angles under the applied engine operating conditions. As temperature and pressure increase, the fractal dimension decreases significantly to a minimum at the early diffusion combustion stage. The soot particles become more compact again as the fractal dimension increases during the subsequent combustion period. Primary particle sizes start small, go through a maximum in the early diffusion combustion phase and decline again as combustion proceeds. [Copyright &y& Elsevier]

Abstract: The diesel soot was extracted from the chamber of a running diesel engine using a total cylinder sampling system. A structural description and size distribution of the soot spherules were performed by means of high-resolution transmission electron microscopy (HRTEM). HRTEM image analysis was carried out to achieve semi-quantitative information about the soot organization. Different nanostructures were found in dependence upon the engine test conditions. A better organization of the graphitic layers occurred for the in-cylinder soot as the expansion stroke developed. The oxygen concentrations at sampling angles and the cylinder pressure were measured. The oxidation rates of the in-cylinder soot during the late combustion phase were calculated according to the differences of spherules size distributions between two consecutive sampling angles. The soot reactivity in dependence on the nanostructure was shown after deducting the effect of oxygen concentration and temperature. The increase of resistance toward oxidation was associated to the increase of the structural order for the in-cylinder soot. The results are a useful database for testing the structure–property relationship between the nanostructure and the reactivity of the in-cylinder diesel soot. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an investigation of the carbonyl emissions from a direct injection heavy-duty diesel engine fueled with pure diesel fuel (DF) and blended fuel containing 15% by volume of ethanol (E/DF). The tests have been conducted under steady-state operating conditions at 1200, 1800, 2600rpm and idle speed. The experimental results show that acetaldehyde is the most predominant carbonyl, followed by formaldehyde, acrolein, acetone, propionaldehyde and crotonaldehyde, produced from both fuels. The emission factors of total carbonyls vary in the range 13.8–295.9mg(kWh)−1 for DF and 17.8–380.2mg(kWh)−1 for E/DF, respectively. The introduction of ethanol into diesel fuel results in a decrease in acrolein emissions, while the other carbonyls show general increases: at low engine speed (1200rpm), 0–55% for formaldehyde, 4–44% for acetaldehyde, 38–224% for acetone, and 5–52% for crotonaldehyde; at medium engine speed (1800rpm), 106–413% for formaldehyde, 4–143% for acetaldehyde, 74–113% for acetone, 114–1216% for propionaldehyde, and 15–163% for crotonaldehyde; at high engine speed (2600rpm), 36–431% for formaldehyde, 18–61% for acetaldehyde, 22–241% for acetone, and 6–61% for propionaldehyde. A gradual reduction in the brake specific emissions of each carbonyl compound from both fuels is observed with increase in engine load. Among three levels of engine speed employed, both DF and E/DF emit most CBC emissions at high engine speed. On the whole, the presence of ethanol in diesel fuel leads to an increase in aldehyde emissions. [Copyright &y& Elsevier]

• The physical properties of CFT and ULSD soots are studied at various engine modes. • CFT produces the soot with smaller fractal dimensions and primary particle sizes. • CFT soot has more ordered nanostructure and lower reactivity than the ULSD soot. • The fringe length and tortuosity show definite correlations with soot reactivity. This study investigated the physical properties of the exhaust soot particles from a light-duty diesel engine fueled with an ultra-low sulfur diesel fuel (ULSD) and Fischer–Tropsch diesel fuel synthesized from coal (CFT). The morphology and nanostructure of the obtained soot were characterized using a high-resolution transmission electron microscopy, while the oxidation reactivity of soot was evaluated by the thermogravimetric analysis (TGA). Despite the different fuel properties, both the ULSD and CFT soot exhibits similar changes in fractal dimension, primary particle size and nanostructure parameters (including fringe length, separation distance and tortuosity) when varying the engine speed or load. However, the CFT soot has smaller fractal dimensions and primary particle sizes and a more ordered nanostructure as compared to the ULSD soot. The TGA results demonstrate that the CFT soot has the higher apparent activation energy, indicating that it is less reactive than the ULSD soot. The length and tortuosity of the fringes within the soot structure are found to have definite correlations with soot reactivity. [ABSTRACT FROM AUTHOR]

The mechanism for the C2H3+ CH3CH2OH reaction has been investigated by the CCSD(T)/cc-pVTZ method based on the geometries of stationary points optimised at the B3LYP/6-311++G(d, p) level of theory. Five reaction channels have been identified for the production of C2H4+ CH2CH2OH, C2H4+ CH3CH2O, C2H4+ CH3CHOH, C2H3OH + CH3CH2,and C2H3OCH2CH3+ H (denoted as channels (1)–(5), respectively). The potential barrier heights of the corresponding transition states TSR/P1, TSR/P2, TSR/P3, TSR/P4 and TSR/P5 were predicted to be 12.40, 8.50, 8.11, 38.38 and 42.21 kcal/mol at the CCSD(T)//B3LYP level of theory, respectively. The rate constants and branching ratios for the three lower energy H-abstraction channels were calculated using conventional transition state theory with Eckart tunnelling correction at the temperature range 300–2500 K. The predicted rate constants have been compared with the available literature data. Both the forward and reverse rate constants have positive temperature dependence, and the tunnelling effect is only important at low temperatures. The branching ratio calculation shows that channel (2) is predominant and channel (3) is less competitive, while channel (1) is almost neglectable at low temperatures. However, all three channels are important in high-temperature region. [ABSTRACT FROM PUBLISHER]

ABSTRACT The mechanism for the C2H3 + CH3OH reaction has been investigated by the Gaussian-4 (G4) method based on the geometric parameters of the stationary points optimized at the B3LYP/6-31G(2df, p) level of theory. Four transition states have been identified for the production of C2H4 + CH3O (TSR/P1), C2H4 + CH2OH (TSR/P2), C2H3OH + CH3 (TSR/P3), and C2H3OCH3 + H (TSR/P4) with the corresponding barriers 8.48, 9.25, 37.62, and 34.95 kcal/mol at the G4 level of theory, respectively. The rate constants and branching ratios for the two lower energy H-abstraction reactions were calculated using canonical variational transition state theory with the Eckart tunneling correction at the temperature range 300-2500 K. The predicted rate constants have been compared with existing literature data, and the uncertainty has been discussed. The branching ratio calculation suggests that the channel producing CH3O is dominant up to about 1070 K, above which the channel producing CH2OH becomes very competitive. [ABSTRACT FROM AUTHOR]

• A series of excellent properties NH 3 -SCR catalysts. • The introduction of Ce and Zr can increase SCR activity and anti-thermal aging in NOx abatement. • 6%Ce-2%Zr/Cu-ZSM-5 catalyst has an excellent SCR activity than Cu-ZSM-5 catalyst in the presence of water vapor. The effects of cerium and cerium + zirconium supported over Cu-ZSM-5 on SCR activity and anti-thermal aging performance in NOx abatement have been studied. X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance, temperature-programmed technologies, Fourier transform infrared spectroscopy, and in-situ diffuse reflectance infrared Fourier transform spectroscopy were used to characterize the surface properties and transition-state species of the catalysts. The 6 %Ce-2 %Zr/Cu-ZSM-5 catalyst exhibits excellent NOx purification activity under dry and water vapor conditions and the best thermal aging resistance. Copper and zirconium species formed are in the nanometer size range and are well dispersed on the ZSM-5 surface, and cerium was formed with the low crystallinity of CeO 2 as an increase of cerium content. Cerium and zirconium addition improve copper dispersion and the cooperative effect between copper and cerium/zirconium. Zirconium can promote the presence of copper in the form of ionic state rather than oxides, improve copper species dispersion, assist to stabilize the framework of ZSM-5, and prevent copper cations precipitation sintering. There were no obvious correlations between acid site strength and the SCR catalytic activity. The NH 3 -SCR reaction over 6 %Ce-2 %Zr/Cu-ZSM-5 catalyst co-follows the Eley-Rideal and Langmuir-Hinshelwood mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Manganese–zirconium catalysts loaded on ZSM-5 (Si/Al=25) were prepared using an ion-exchange method and investigated for the selective catalytic reduction of NO, with the aim of studying the effects of zirconium doping on the performance of Mn-based ZSM-5 catalysts. A series of characterization techniques, namely N2-sorption, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen, and X-ray photoelectron spectroscopy (XPS), were used to characterize these samples. TEM and XRD results showed that the addition of zirconium increased the manganese dispersion and prevented manganese crystallization. XPS results demonstrated that the introduction of zirconium enhanced the manganese species enrichment on the ZSM-5 grain surfaces. After zirconium addition, some of the manganese ions were incorporated into the zirconia lattice. The strong interaction between Mn and Zr contributed to the formation of Zr3+ ions or oxygen vacancies around the Zr4+ ions, which enhanced the redox abilities of the Mn–Zr/ZSM-5 catalysts. The temperature range for efficient NO conversion was lowered after zirconium doping. The MnZr3/ZSM-5 (Mn 3.2wt.% and Zr 8.6wt.%) sample exhibited NO x conversions (>90%) over a wide temperature range (230–415°C) and markedly superior to that of Mn/ZSM-5 (296–425°C). Moreover, the formation of N2O was suppressed at low temperatures due to the presence of zirconium in the catalysts. [Copyright &y& Elsevier]

An excellent textual properties and performance La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was synthesized. The reaction mechanism of H 2 /NOx over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was investigated by temperature programmed reduction/ desorption/ surface reaction (TPR/D/SR) technologies and in-situ diffuse reflectance Fourier transform (DRIFT) technology. The results show that cerium or palladium species are inserted into the cells of LaCoO 3 , as well as they synergetic promote the redox properties of the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst. Surface activated nitrates exist over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst, with thermal stable increasing in the order: absorbed N 2 O 4 < monodentate nitrates < chelating bidentate nitrates < nitrates unidentate < free ionic nitrates < bulk free ionic nitrates. H 2 preferentially reacted with absorbed N 2 O 4 and monodentate nitrates at low temperatures, due to their high activity. The concentration of generated NH 3 from the redox reaction of H 2 /NOx achieves the maximum value between 350 and 450 °C over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst. Compared with the NOx adsorption process at 50 °C, monodentate nitrates and absorbed N 2 O 4 disappeared due to their low thermal stability, chelating bidentate nitrates become stronger, as well as free ionic nitrates converted to bulk free ionic nitrates with higher thermal stability at 350 °C. When H 2 is exposed to NOx species adsorbed on La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 , chelating bidentate nitrates and bulk free ionic nitrates are consumed gradually, indicating that although the bulk free ionic nitrates own high stability, it also could be consumed by involving in the H 2 /NOx reaction at 350 °C. The quantitative H 2 /NO reaction experiments confirmed the results of H 2 -TPSR and NSR. It is beneficial to the formation of NH 3 when the H 2 /NO ratio is more than 2.5. Comparing traditional Pt-BaO/Al 2 O 3 catalyst, the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst exhibit an excellent performance, including considerable NH 3 production property, lower N 2 O selectivity, and the precious metal saving. [Display omitted] • An excellent textual properties and performance La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was synthesized. • The reduction behavior of the stored NOx over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was researched. • The H 2 /NO reaction process over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was investigated. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of adding 20 vol.% biodiesel to petroleum diesel (to produce a mixture termed B20) on the physical properties and reactivity of the resulting exhaust soot particles. Tests were performed at different engine loads of a constant speed, and the soot particles from the combustion of B20 and petroleum diesel fuel (DF) were collected from the engine exhaust stream. Transmission electron microscopy and Raman spectroscopy were employed for the analysis of soot morphology and nanostructure. The thermogravimetric analysis was used to determine the oxidative reactivity of the soot. For both the DF and B20 soot, increased engine loads result in soot aggregates with more compact morphology and primary soot particles with larger size and more organized structure. Compared to the DF soot, the B20 aggregates have a slightly more compact morphology and smaller primary particle size. No appreciable differences are observed in nanostructure between the DF and B20 soot. The thermogravimetric analysis demonstrates that the B20 soot is associated with lower peak temperature, burnout temperature and apparent activation energy, suggesting that it is more reactive than the DF soot. [ABSTRACT FROM AUTHOR]

In this study, programmed temperature vaporization in the solvent vent mode (PTV-SV) of gas chromatography-mass spectrometry was optimized and validated for the analysis of particle-phase and gas-phase polycyclic aromatic hydrocarbons from diesel engine combustion. Because of the large number of experimental and response variables to be studied, central composite inscribed design was used to optimize the PTV-SV injection factors, including initial inlet temperature, vaporization flow and time. The optimized PTV-SV method was validated by linearity, accuracy and sensitivity. For the 16 Polycyclic aromatic hydrocarbons (PAHs) studied, the correlation coefficients for the calibration plots of peak areas versus concentrations (0.5–300 ng mL−1) ranged from 0.9812–0.9998. Limits of detection ranged from 0.016–20,130.375 ng mL−1, and limits of quantification ranged from 0.055–1.25 ng mL−1. The optimized method was used for the analysis of real samples collected from a diesel engine, which included particle-phase and gas-phase PAHs. The results showed that the improved PTV-SV method was satisfying for simultaneously identifying and quantifying PAHs produced during diesel combustion. [ABSTRACT FROM AUTHOR]

This work aimed to optimize the washcoat slurry for hydrotalcite-based lean NOx trap (LNT) catalyst. The effects of the slurry properties including pH, solid content, binder and additive on the hydrotalcite-based slurry viscosity were investigated. The particle size distribution of the optimal hydrotalcite-based slurry was measured. A cordierite material was used to coat the optimal slurry, and the washcoat was characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption. The optimal slurry containing Pt and Ba was coated on the cordierite for the preparation of hydrotalcite-based LNT catalyst, and the performances of this catalyst were evaluated by NOx storage test, temperature programmed desorption and NOx reduction. For comparison, the performance of the commercial LNT catalyst with Pt/BaO/Al2O3 was analyzed. After coating, the hydrotalcite-based washcoat was closely contacted with the support, being the main phase MgO and presenting a specific surface area of 86.3 m2/g. The hydrotalcite-based LNT catalyst had better NOx storage and desorption ability, selectivity to N2 and LNT efficiency than the Pt/BaO/Al2O3 catalyst. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to better understand the reaction kinetics of diesel exhaust soot during oxidation process. A thermogravimetric analyzer was used to oxidize real diesel exhaust soot generated from a Euro VI diesel engine under non-isothermal conditions. The Friedman-Reich-Levi method and the Sestak-Berggren model were used to determine the oxidation kinetics. Raman spectroscopy and high-resolution transmission electron microscopy were employed to follow the changes of the soot structure during oxidation. The activation energy gradually increased with increasing conversion level during soot oxidation. The oxidation process of diesel exhaust soot could be described as three-step kinetics, and the calculated conversions fitted the experimental results very well. The kinetic predictions of diesel soot oxidation that were obtained using the proposed kinetic models were more accurate and precise than those with the common first-order model. The structural order increased as oxidation progressed, which was responsible for the increased activation energy. The structural ordering was principally caused by the preferential oxidation of the disordered fraction in the diesel soot, especially for the amorphous carbon, which was oxidized in the initial stage of the oxidation reaction. [Display omitted] • The oxidation reaction kinetics of diesel exhaust soot were studied. • The activation energy of soot gradually increases with conversion during oxidation. • The oxidation process of diesel soot can be described as three-step kinetics. • The developed kinetic models can reflect the soot oxidation process accurately. • The structural ordering of diesel soot causes the increase in activation energy. [ABSTRACT FROM AUTHOR]

The storage and reduction of NOx on a series of Fe-modified hydrotalcite-based lean NOx trap catalysts were assessed, together with the product selectivity. The crystal structures and micromorphologies of these materials were characterized using X-ray diffraction and scanning electron microscopy, while in situ diffuse reflectance Fourier transform infrared spectroscopy was used to evaluate the evolution of transition state species. The introduction of Fe was found to improve the synergistic interaction between the Mg and Fe in the hydrotalcite structure, allowing these catalysts to work efficiently at low temperatures. In addition, both Pt/BaO/MgAlO and Pt/BaO/MgFeO catalysts exhibited better NOx adsorption and reduction performance compared with Pt/BaO/Al 2 O 3. The superior performance of the former two materials was attributed to the enhanced adsorption of NOx in the form of nitrates and nitrites by Fe and Mg and to the ready decomposition of these nitrates at low temperatures. A Pt/BaO/MgFeO catalyst showed excellent low temperature activity and high selectivity for N 2 together with superior sulfur resistance compared with Pt/BaO/Al 2 O 3. [Display omitted] • This study prepared a series of hydrotalcite-derived lean NOx trap catalysts. • The introduction of Fe was found to increase the NOx removal efficiency at low temperature because of improving the synergistic interaction between the Fe and Mg in the hydrotalcite structure. • Pt/BaO/MgFeO has better sulfur resistance than traditional Pt/BaO/Al 2 O 3 catalysts. [ABSTRACT FROM AUTHOR]

Copper–cerium–zirconium catalysts loaded on TiO 2 prepared by a wet impregnation method were investigated for NH 3 -selective catalytic reduction of NO x , aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu–Ce–Zr/TiO 2 catalysts. The Cu–Ce 0.25 –Zr 0.75 /TiO 2 sample exhibited nearly 100% NO x conversion over a wide temperature range (165–450 °C), which is strikingly superior to that of Cu/TiO 2 (210–389 °C) within the range of exhaust temperatures of diesel engines. The factors that govern the activity enhancement were extensively investigated by using a series of characterization techniques, namely X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H 2 -TPR). The results showed that the addition of zirconium and/or cerium refined the copper dispersion, prevented copper crystallization and partially incorporated the copper ions into the zirconia (ceira) lattice, which led to enhance the redox abilities of Cu–Ce–Zr/TiO 2 catalysts. [ABSTRACT FROM AUTHOR]

Experiments were performed on a CH 4 lean premixed flame to better understand the effect of the oxidation-induced fragmentation of primary particles on soot oxidation reactivity. An aerosol generator was used to homogeneously disperse diesel soot into the flame. Because minimal soot was formed in this flame itself, the information about diesel soot fragmentation was readily obtained. The thermophoretic and probe sampling techniques were used to obtain soot particles at various heights above the burner. The particle size distribution, oxidation reactivity, nanostructure and carbon chemical state of each sample were characterized. The soot reactivity was evaluated in terms of activation energy. The results indicate a higher extent of aggregate fragmentation occurs at moderate soot burnout percentages and that the internal structure in soot is not destroyed during aggregate fragmentation. At higher soot burnout percentages, the internal burning produces more primary particle fragmentation, so that the soot particles exhibit an increase in fringe tortuosity and decreases in fringe length and sp2/sp3 hybridization ratio. These variations in physicochemical properties increase the oxidation reactivity of the soot particles. [ABSTRACT FROM AUTHOR]