Influence of Methanol–Biodiesel Blends on the Particulate Emissions of a Direct Injection Diesel Engine

In this study, Euro V diesel fuel, biodiesel, and methanol–biodiesel blends were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion characteristics and particulate emissions of the diesel engine under five engine loads at the maximum torque engine speed of 1800 rpm. Compared with Euro V diesel fuel, biodiesel gives lower and earlier heat release rate. For the blended fuels, the peak heat release rate becomes higher and retarded. With regard to particulate mass concentration, biodiesel generates less than Euro V diesel fuel, while the blended fuels result in significant reduction especially at high engine loads. Compare with Euro V diesel fuel, the total particle number concentration of using biodiesel is always higher while the geometric mean diameter (GMD) of the particles is lower. With the blended fuel, the total number concentration and GMD decrease in comparison with pure biodiesel. Further analysis shows that the difference between the total number concentration of biodiesel and Euro V diesel fuel is in particles smaller than 50 nm rather than in the larger particles. The use of methanol–biodiesel blends, compared with biodiesel, could reduce the number concentration of all sizes. A comparison between the particulate mass emission and total particulate number concentration with the mass of fuel burned in the diffusion mode show that they are strongly related to each other, even for the blended fuel.     

Impact of Biodiesel-Based Na on the Selective Catalytic Reduction of NOx by NH3 Over Cu–Zeolite Catalysts

A single-cylinder diesel engine was used to investigate the impact of Na on Cu–zeolite SCR catalysts using 20 % bio- and petrol-diesel fuel blend (B20) with elevated levels of Na. The Na exposure was performed on light-duty (DOC–SCR–DPF) and heavy-duty (DOC–DPF–SCR) configurations of the diesel emissions control devices. The accelerated Na aging is achieved by exposing the system to elevated levels of Na that represent full useful life exposure (700,000 km) and periodically increasing the exhaust temperature to replicate DPF regeneration. After aging, the NO_x performance and relevant chemistry of the SCR catalysts were evaluated in a bench flow reactor. The SCR in the DOC–SCR–DPF configuration was found to be severely affected by Na contamination, especially when NO was the only NO_x species in the simulated exhaust gases. In the DOC–DPF–SCR configuration, no impact is observed in the SCR NO_x reduction activity. Electron microprobe analysis (EPMA) reveals that Na contamination on the SCR samples in the DOC–SCR–DPF configuration is present throughout the length of the catalysts.     

Aspects of the Role of Hydrogen in H2-Assisted HC–SCR Over Ag–Al2O3

The role of hydrogen in H₂-assisted HC–SCR of NO _x over Ag–Al₂O₃ is investigated by XPS and in situ DRIFT spectroscopy. Hydrogen does not reduce the surface silver species to metallic silver, however direct reduction of surface nitrates by hydrogen is observed. It is proposed that one important role of hydrogen is the removal of nitrates from the Ag–Al₂O₃ surface.     

Analysis of CO2–NH3 reaction dynamics in an aqueous phase by PCA and 2D IR COS

Both carbamation and bicarbonation are of prime importance in the absorption reactions of CO₂ in an aqueous NH₃ solution, as they are related to the CO₂ working capacity, regeneration energy, and the critical problem of blocking the gas pathway for the CO₂ capture process. Herein, the influence of reaction temperature on the CO₂ and NH₃ reaction in an aqueous solution is demonstrated by a principal component analysis (PCA) and a two dimensional correlation analysis (2D IR COS) obtained from FT-IR, dependent on the reaction time. In contrast to the reaction at 298 K, conversion of the dominant reaction from carbamation to bicarbonation and respective conformational changes were observed at 278 K by PCA and 2D IR COS. The PCA results elucidate that two major reactions following the dependence of reaction time were divided into two regions, I and II. The turnover point was subsequently tracked in these two regions, where precipitation of ammonium bicarbonate occurred due to the limitation of solubility at this turning point. The interrelation and sequential variation of conformations in regions I and II were investigated by synchronous and asynchronous 2D correlation analyses. The combination of PCA and 2D IR COS provides a powerful and useful analytic method to capture and monitor the dynamics of complex chemical reactions.     

Influence of Hydrothermal Ageing on NH3-SCR Over Fe-BEA—Inhibition of NH3-SCR by Ammonia

The decay in ammonia adsorption capacity and the amount of active iron sites are important to consider in order to understand the deactivation processes of Fe-BEA for NH₃-SCR catalyst applications. NH₃ and NO storage capacity experiments together with kinetic modeling have been used to evaluate ammonia inhibition during NH₃-SCR before and after hydrothermal treatment of H-BEA and Fe-BEA. The kinetic model shows that at least four types of acid sites for H-BEA and one additional site for Fe-BEA are required to predict the NH₃ desorption well. NH₃-TPD experiments together with simulations show that the strongest adsorption sites are the sites that are most affected by the hydrothermal treatment. For H-BEA a clear correlation between the ammonia storage capacity and the improved NO_X conversion after NH₃ cut-off during NH₃-SCR is observed. However, for Fe-BEA an inhibiting effect of ammonia after NH₃ cut-off is seen but no significant difference (i.e. increased NO_X conversion time) between fresh and aged samples can be observed, indicating that the inhibiting effect is unaffected by the hydrothermal treatment.     

Measurement and Correlation of Liquid–Liquid Equilibrium Data for Ethanol–Water–KF and Ethanol–Water–K2CO3 Systems

The liquid–liquid equilibrium data for two ternary systems, ethanol–water–KF and ethanol– water–K2CO3, were determined at 25℃. Experiments show that by adding KF or K2CO3 into the ethanol–water system two phases are formed: an ethanol-rich phase with negligible salt and a water-rich phase with negligible ethanol, thus water can be separated out easily. A mathematical calculation of the liquid–liquid equilibrium data was carried out with the Pitzer theory on water activity in the aqueous phase, and with the Wilson or NRTL or UNIQUAC equations for that in the ethanol phase, which is in good agreement with experimental data.     

Efficacy of different generations and concentrations of PAMAM–NH2 on the performance and structure of TFC membranes

In this work, several polyamide thin layer membranes were prepared and modified with polyamidoamine (PAMAM) dendrimers in different generations (G₀, G₁, and G₂) and different concentrations (0.5, 1.5 and 3 wt.%) to investigate the occurring changes in the performance and morphology of the prepared thin layers. SEM and AFM data (reinforced with SPM software) proved that the dense and compressed surfaces were fabricated by loading and increasing of the generations and concentrations of PAMAM. In addition, the MWCO of the membranes drastically decreased. The chemical properties of the surface were investigated with ATR-IR and the occurring changes were studied. The zeta potential measurements illustrated that the surface charge of the thin layers was changed with alteration in the generations and concentrations of PAMAM. Additionally, in some cases the rejection capability of NaCl increased over 90%. Furthermore, the contact angle results clearly demonstrated an enhancement in the hydrophilicity of the membranes. The flux recovery ratio of the thin layers increased from 63% (in the unmodified thin layer) to near 97% in the thin layer composed of 3 wt.% G₀.     

Influence of hydrogen on growth and microstructure of boron nitride coatings obtained from BCl3–NH3–H2 system by chemical vapor infiltration

Hexagonal boron nitride (h-BN) interfacial coatings were prepared by chemical vapor infiltration (CVI) process from BCl₃–NH₃–H₂ system with different hydrogen contents for improving the toughness of ceramic matrix composites. In this study, the yield of BN was found to be 94.90% without hydrogen present in the reactant system as calculated via FactSage, while it reached 99.95% at the [H₂]/[BCl₃] ratio of 10 and the [NH₃]/[BCl₃] ratio of 1, when chemical equilibrium was reached. BN interfacial coatings containing mixture of hexagonal and turbostratic phases were obtained. The deposition rate of coating increased from 18.2 ± 0.4 nm min⁻¹ (β = 0) to 23.0 ± 0.4 nm min⁻¹ (β = 5) with the increase of hydrogen content in reactants, then it significantly decreased when β was 10. Owing to different nucleation amounts on the surface of fibers, samples S2 (β = 2) and S3 (β = 5) exhibited particles with circular shapes and smooth surfaces, while the other coatings presented particles with polygonal shapes and rough surfaces. Moreover, the onset temperature of weight gain of sample S2 was 102 °C higher than that of sample S4, thus indicating the enhancement of the high-temperature oxidation resistance of BN coating.     

The Effect of Biofuel Originated Potassium and Sodium on the NH3-SCR Activity of Fe–ZSM-5 and W–ZSM-5 Catalysts

The effect of potassium, sodium and water on Fe–ZSM-5, W–ZSM-5 and ZSM-5 catalysts was investigated. Catalysts were characterized by several techniques and tested in the NH₃-SCR reaction. The impact of water-, K- and Na-treatments on the activity of catalysts was negligible. Thus, the catalysts can be concluded to be resistant to K- and Na-treatments.     

Analysis of the Composition of CuI–As2Se3 and CuI–PbI2–As2Se3 Chalcogenide Films by X-ray Fluorescence Spectroscopy

The chalcogenide films As₂Se₃, CuI–As₂Se₃, and CuI–PbI₂–As₂Se₃ are prepared through chemical deposition from an organic solvent and investigated by X-ray fluorescence spectroscopy. The contents of the main components of the chalcogenide films are compared by analyzing the intensity ratios for the AsK , SeK , and CuK lines. It is found that the content of the main components (As, Se, and Cu) is virtually the same in binary chalcogenide, pseudobinary, and multicomponent chalcogenide systems, no matter what the technique used for preparing the materials (films deposited from solutions of chalcogenide glasses in n-butylamine and bulk glasses). This result is consistent with a model of dissolution of vitreous semiconductors in organic bases (amine) according to which the fundamental properties of bulk glasses remain unchanged upon formation of the films. The experimental data indicate an analogy between the properties of the multicomponent chalcogenide glasses CuI–As₂Se₃ and CuI–PbI₂–As₂Se₃ and the chalcogenide glass–based films.     

On the Efficiency of NH3–SCR Catalysts for Heavy Duty Vehicles Running on Compressed Natural Gas in Synthetic Gas Bench Scale

This work aims to study the effectiveness of NH₃–SCR after-treatment systems, initially developed for a Diesel application, on Heavy duty natural gas engines working in lean conditions for exhaust gas pollutants abatement. Commercial oxidation and NH₃–SCR catalysts were investigated for respectively CH₄, CO oxidation and NO_X reduction. In this study, we showed that the NH₃–SCR coupled with an oxidation catalyst lead to significant conversion of CH₄, CO and NO_X, and can be used as after-treatment system for pollutants providing from CNG lean burn engines.     

Analysis of the Influence of the Loading Scheme on the Stress State of the Surface Layer of Al2O3–TiC-Ceramics with AlN and TiN Coatings

Refractories and Industrial Ceramics - The results of force, thermal, and combined stress analysis of the surface layer of Al2O3–TiC-ceramics with AlN and TiN coatings are analyzed and...     

Selective catalytic reduction (SCR) of NO by NH3 over TiO2-supported V2O5–WO3 and V2O5–MoO3 catalysts

A comparison between commercial and model WO₃–V₂O₅/TiO₂ and MoO₃–V₂O₅/TiO₂ SCR catalysts is considered in this study. The data indicate that WO₃ and MoO₃ behave as “structural” and “chemical” promoters for the catalysts. MoO₃-based catalysts are more active but less selective than WO₃–V₂O₅/TiO₂ catalysts in the SCR reaction, although in the presence of water the catalytic performances of the investigated samples are comparable. This revised version was published online in August 2006 with corrections to the Cover Date.     

Novel promotional effect of yttrium on Cu–SAPO-34 monolith catalyst for selective catalytic reduction of NOx by NH3 (NH3-SCR)

Cu–SAPO-34 and CuY–SAPO-34 catalysts for NH₃-SCR were prepared by the wet-impregnation method. XRD, UV–vis DRS, ESR and NH₃-TPD results showed that the introduction of Y effectively improved the dispersion of copper species, increased the amount of isolated copper ions and enhanced the acid density. In addition, the activity test, NH₃-TPD and TGA results reflected that the CuY–SAPO-34 catalyst showed better C₃H₆ oxidation activity, lower dropping degree of acid sites after C₃H₆/O₂ treatment and less adsorption of C₃H₆/O₂ than Cu–SAPO-34 catalyst. Therefore, the addition of Y promoted the NH₃-SCR performance and the hydrocarbon (HC) resistance of Cu–SAPO-34 catalyst.     

Structure Sensitivity of NO Reduction over Iridium Catalysts in HC–SCR

Ir black with different crystallite sizes and Ir–H–ZSM-5 prepared using two different precursors were investigated for their behavior in selective catalytic reduction using hydrocarbons as reducing agents (HC–SCR). Emphasis was given to the study of the influence of time onstream on N₂ yield, the change in Ir crystallite size, and the change in the ratio of Ir : IrO₂. Under reaction conditions at 450°C Ir–H–ZSM-5 did not reach steady-state catalytic behavior within 32 h. In contrast, unsupported Ir black showed higher initial yields of nitrogen and approached steady-state considerably faster. Ir black with the largest crystallite size (45 nm) required the shortest time for reaching steady-state behavior. The influence of crystallite size on the reaction of Ir with O₂ and NO was addressed and related to the increase in N₂ yields with increasing Ir crystallite size in the reduction of NO using propene as a reducing agent. Comparative pulse thermoanalysis studies of NO and O₂ adsorption on Ir black with different crystallite sizes (5–45 nm) revealed that the relative uptake of NO (m_NO/m_O2) increases strongly with increasing crystallite size. This behavior is due to a strong structure sensitivity of NO adsorption, whereas O₂ adsorption is relatively insensitive to crystallite size. The improved yield of N₂ with increasing crystallite size under HC–SCR conditions is traced to the higher surface concentration of NO relative to O₂ with increasing crystallite size.     

Effect of the Presence of Ceria in the NSR Catalyst on the Hydrothermal Resistance and Global DeNOx Performance of Coupled LNT–SCR Systems

The global performance of coupled LNT–SCR systems, addressed to high NOx-to-N₂ conversion, minimal ammonia slip and null N₂O production, as well as the hydrothermal resistance of single NSR and SCR monolith catalysts and their coupling is discussed. Pt–Ba/Al₂O₃ and Pt–Ce–Ba/Al₂O₃ were washcoated on cordierite monoliths as NSR catalysts, and Cu/CHA was washcoated on similar monoliths as SCR catalysts. Both monoliths were coupled in two subsequent reactors to conform the LNT–SCR system. Previously to washcoating, the fresh powder catalysts and after severe hydrothermal aging were fully characterized by N₂ adsorption–desorption isotherms at 77 K, X-ray diffraction, NH₃ temperature-programmed desorption, and H₂ chemisorption to relate textural and chemical characteristics with the DeNO_x performance. The Cu/CHA catalyst shows an excellent hydrothermal resistance for the NH₃–SCR reaction. Incorporation of ceria to the model Pt–BaO/Al₂O₃is beneficial for the NO-to-NOx oxidation and NO₂ storage, improving NO conversion at low temperature and reducing the NH₃ slip. However, addition of ceria is detrimental for the hydrothermal resistance of the NSR catalyst. However, this detrimental effect is minimized when the NSR catalyst is coupled with the Cu/CHA monolith downstream of the NSR catalyst, achieving the coupled LNT–SCR device high NO conversion and minimal NH₃ slip with superior N₂ selectivity for an extended temperature windows, including as low as 220 °C, and maintaining performance even after severe hydrothermal aging.