The cerium and/or zirconium-doped Cu/ZSM-5 catalysts (CuCe_xZr_1−xO_y/ZSM-5) were prepared by ion exchange and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H₂-TPR). Activities of the catalysts obtained on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia were measured using temperature programmed reactions. Among all the catalysts tested, the CuCe_0.75Zr_0.25O_y/ZSM-5 catalyst presented the highest catalytic activity for the removal of NO, corresponding to the broadest active window of 175–468 °C. The cerium and zirconium addition enhanced the activity of catalysts, and the cerium-rich catalysts exhibited more excellent SCR activities as compared to the zirconium-rich catalysts. XRD and TEM results indicated that zirconium additions improved the copper dispersion and prevented copper crystallization. According to XPS and H₂-TPR analysis, copper species were enriched on the ZSM-5 grain surfaces, and part of the copper ions were incorporated into the zirconium and/or cerium lattice. The strong interaction between copper species and cerium/zirconium improved the redox abilities of catalysts. Furthermore, the introduction of zirconium abates N₂O formation in the tested temperature range.

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.

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.

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.

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.