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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]

• 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]

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]

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]

• 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]

• 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]