Diesel soot oxidation by nitrogen dioxide,oxygen and water under engine exhaust conditions: Kinetics data related to the reaction mechanism

Experimental studies on diesel soot oxidation under a wide range of conditions relevant for modern diesel engine exhaust and continuously regenerating particle trap were performed. Hence, reactivity tests were carried out in a fixed bed reactor for various temperatures and different concentrations of oxygen, NO₂ and water (300–600 °C, 0–10% O₂, 0–600 ppm NO₂, 0–10% H₂O). The soot oxidation rate was determined by measuring the concentration of CO and CO₂ product gases. The parametric study shows that the overall oxidation process can be described by three parallel reactions: a direct C–NO₂ reaction, a direct C–O₂ reaction and a cooperative C–NO₂–O₂ reaction. C–NO₂ and C–NO₂–O₂ are the main reactions for soot oxidation between 300 and 450 °C. Water vapour acts as a catalyst on the direct C–NO₂ reaction. This catalytic effect decreases with the increase of temperature until 450 °C. Above 450 °C, the direct C–O₂ reaction contributes to the global soot oxidation rate. Water vapour has also a catalytic effect on the direct C–O₂ reaction between 450 °C and 600 °C. Above 600 °C, the direct C–O₂ reaction is the only main reaction for soot oxidation. Taking into account the established reaction mechanism, a one-dimensional model of soot oxidation was proposed. The roles of NO₂, O₂ and H₂O were considered and the kinetic constants were obtained. The suggested kinetic model may be useful for simulating the behaviour of a diesel particulate filter system during the regeneration process.     

The Characteristics of Green Calcium Oxide Derived from Aquatic Materials

Thermogravimetric Analysis of three aquatic materials, i.e. cuttlebone, mussel shell and oyster shell, and other physicochemical characteristics were investigated. The highest decomposition rates of aquatic materials under two surrounding gases, i.e. oxygen and nitrogen, exhibited no significant difference for cuttlebone (3.6×10^-5-4.8×10^-5 mg s^-1 mg_initial^-1 at heating rate 5 °C/min and 11.8 ×10^-5 -12.5×10^-5 mg s^-1 mg_initial^-1 at heating rate 15 °C/min) and mussel shell (3.4×10^-5- 5.2×10^-5 mg s^-1 mg_initial^-1 at heating rate 5 °C/min and 11.9×10^-5 – 12.4×10^-5 mg s^-1 mg_initial^-1 at heating rate 15 °C/min), while oyster shell provided the higher decomposition rate under nitrogen surrounding gas (7.6×10^-4 mg s^-1 mg_initial^-1 at heat rate 5 °C/min and 21.53×10^-4 mg s^-1 mg_initial^-1 at heating rate 15 °C/min). This is probably because of the difference in their starting crystalline structures, i.e. aragonite (cuttlebone and mussel shell) and calcite (oyster shell). The cubic calcium oxides were prepared by calcination of three aquatic materials under oxygen and nitrogen surrounding gases at 5 °C/min ramping to 850 °C for 2 hours. All resulting calcium oxides obtained from oxygen atmosphere provided only cubic crystalline phases and the adsorption-desorption isotherms (IUPAC Type III), whereas the calcinations under nitrogen surrounding gas gave a presence of calcium hydroxide crystalline or hydroxyl- contaminate existing with cubic calcium oxide that influences on the strength and the number of carbon dioxide adsorption sites. The specific surface area of all resulting calcium oxides ranged from 0.1 – 1.5 m²/g and the average pore diameter was found in the range of 40-60 nm. The the number of basic sites belonging to CaO derived from Oyster shell or Cuttlebone were improved while firing under oxygen atmosphere. The suitable firing condition is at the low heating rate to develop porous materials.     

Investigation of the evolved gases from Sulcis coal during pyrolysis under N2 and H2 atmospheres

The evolution of gases and volatiles during Sulcis coal pyrolysis under different atmospheres (N₂ and H₂) was investigated to obtaining a clean feedstock of combustion/gasification for electric power generation. Raw coal samples were slowly heated in temperature programmed mode up to 800 °C at ambient pressure using a laboratory-scale quartz furnace coupled to a Fourier transform infrared spectrometer (FTIR) for evolved gas analysis. Under both pyrolysis and hydropyrolysis conditions the evolution of gases started at temperature as low as 100 °C and was mainly composed by CO and CO₂ as gaseous products. With increasing temperature SO₂, COS, and light aliphatic gases (CH₄ and C₂H₄) were also released. The release of SO₂ took place up to 300 °C regardless of the pyrolysis atmosphere, whilst the COS emissions were affected by the surrounding environment. Carbon oxide, CO₂, and CH₄ continuously evolved up to 800 °C, showing similar release pathways in both N₂ and H₂ atmospheres. Trace of HCNO was detected at low pyrolysis temperature solely in pure H₂ stream. Finally, the solid residues of pyrolysis (chars) were subjected to reaction with H₂ to produce CH₄ at 800 °C under 5.0 MPa pressure. The chars reactivity was found to be dependent on pyrolysis atmosphere, being the carbon conversions of 36% and 16% for charN₂ and charH₂, respectively.     

Quantitative and kinetic TG-FTIR study of biomass residue pyrolysis: Dry distiller's grains with solubles (DDGS) and chicken manure

New energy policies all over the world are trying to tackle high oil prices and climate change by promoting the use of biomass to produce heat, electricity and liquid transportation fuels. In this paper we studied two different secondary fuels: dry distiller's grains with solubles (DDGS) and chicken manure. These materials have high content of nitrogen and ashes which limit their usage in thermal applications due to potential excessive NO_x emissions and problems of slagging, fouling, corrosion and loss of fluidization.The fuels tested here were received from industrial partners. In order to reduce the ash content the fuels were pre-treated using water leaching pre-treatment.Pyrolysis of these fuels has been monitored through a TG-FTIR set-up. Quantification of the following volatile species was possible: CO, CO₂, CH₄, HCN, NH₃, HNCO, H₂O.The water leaching appeared to decrease the amount of ashes in both samples and remove some of the troublesome compounds like Cl, S and K.The DDGS thermogravimetric curve showed three main peaks at 280 °C, 330 °C and 402 °C with a total weight loss of around 79%wt_a.r. (on an “as received” basis). NH₃ is the main N-compound released at low temperatures with a peak at 319 °C. HNCO and HCN were detected at higher temperatures of around 400 °C. Chicken manure reacted in four stages with peaks at 280 °C, 324 °C, 430 °C and 472 °C with a total average weight loss of 66%wt_a.r. The main N-compound was HNCO, released at 430 °C. Ammonia was detected during the whole measurement, while HCN presented peaks of reactivity at 430 °C and 472 °C.Kinetic analysis was applied using a distributed activation energy method (DAEM) using discrete and Gaussian distributions and data for further modeling purposes were retrieved and presented.     

Synthesis and characterization of porous WO3–SnO2 nanomaterials: An infrared study of adsorbed pyridine and dimethyl methylphosphonate

High surface area porous W/Sn oxide nanomaterials were prepared via water/oil based (W/O) emulsion. Tungstic acid solution was generated by cation exchange of sodium tungstate in acidic Dowex resin. The acid was then mixed with a clear homogeneous aqueous N-cetyl trimethyl ammonium bromide (CTAB) solution followed by a slow addition of 0.2 M SnCl₄ solution. The mixture was stirred for 24 h and then subjected to slow calcination at 500 °C. The prepared materials were characterized using SEM-EDX, BET surface area, and sorption of nitrogen and water. Fourier transform infrared spectroscopy (FTIR) was used to characterize the surface acidic properties using pyridine vapor as a probe. The materials were then tested toward the Dimethyl methylphosphonate (DMMP) adsorption at various temperatures using infrared spectroscopy. At elevated temperatures, the desorption of DMMP from WO₃ and SnO₂ surfaces results in forming methyl phosphonate that strongly bounds on the metal oxide surfaces. In contrast, the FTIR spectra showed that the adsorbed dimethyl methylphosphonate (DMMP) on the mixed W/Sn oxide powders can be molecularly desorbed without any decomposition.     

A cobalt-free electrode material La0.5Sr0.5Fe0.8Cu0.2O3 − δ for symmetrical solid oxide fuel cells

Cobalt-free perovskite oxide La_0.5Sr_0.5Fe_0.8Cu_0.2O_3 − δ (LSFC) was applied as both anode and cathode for symmetrical solid oxide fuel cells (SSOFCs). The LSFC shows a reversible transition between a cubic perovskite phase in air and a mixture of SrFeLaO₄, a K₂NiF₄-type layered perovskite oxide, metallic Cu and LaFeO₃ in reducing atmosphere at elevated temperature. The average thermal expansion coefficient of LSFC in air is 17.7 × 10^− 6 K^− 1 at 25 °C to 900 °C. By adopting LSFC as initial electrodes to fabricate electrolyte supported SSOFCs, the cells generate maximum power output of 1054, 795 and 577 mW cm^− 2 with humidified H₂ fuel (~ 3% H₂O) and 895, 721 and 482 mW cm^− 2 with humidified syngas fuel (H₂:CO = 1:1) at 900, 850 and 800 °C, respectively. Moreover, the cell with humidified H₂ fuel demonstrates a reasonable stability at 800 °C under 0.7 V for 100 h.     

Ni–Al hydrotalcite-like material as the catalyst precursors for the dry reforming of methane at low temperature

Nickel–aluminium and magnesium–aluminium hydrotalcites were prepared by co-precipitation and subsequently submitted to calcination. The mixed oxides obtained from the thermal decomposition of the synthesized materials were characterized by XRD, H₂-TPR, N₂ sorption and elemental analysis and subsequently tested in the reaction of methane dry reforming (DRM) in the presence of excess of methane (CH₄/CO₂/Ar = 2/1/7). DMR in the presence of the nickel-containing hydrotalcite-derived material showed CH₄ and CO₂ conversions of ca. 50% at 550 °C. The high values of the H₂/CO molar ratio indicate that at 550 °C methane decomposition was strongly influencing the DRM process. The sample reduced at 900 °C showed better catalytic performance than the sample activated at 550 °C. The catalytic performance in isothermal conditions from 550 °C to 750 °C was also determined.     

Quantum-classical wave packet calculations for the O(1D) + N2O → NO + NO/N2 + O2 reaction

Mixed quantum-classical calculations have been carried out for the O(¹D) + N₂O reaction with an emphasis on the effect of the relative translational energy as well as initial vibrational state of N₂O on the NO + NO/N₂ + O₂ product branching. The calculations were done within a planar constraint using a five-dimensional analytical potential energy surface previously developed by our group. Three vibrational coordinates in the N₂O molecule were treated with a quantum wave packet technique while other two degrees of freedom, translational and angular motions of O(¹D) with respect to N₂O, were described with classical mechanics. We have found that the initial orientation angle significantly affects the NO + NO/N₂ + O₂ product branching similar to our previous classical trajectory result using the same potential surface. It has been also found that the branching ratio decreases as the translational energy increases except for a low energy region. Excitation of the initial vibrational state of the N₂O reactant does not largely affect the reaction dynamics.     

Mechanochemical synthesis and ionic conductivity of lanthanum phosphosilicate oxyapatites

Lanthanum phosphosilicate apatites with the chemical formula Sr_10–xLa_x(PO₄)_6–x(SiO₄)_xO, where 0 ≤ x ≤ 6, usually prepared by a solid-state reaction at about 1400 °C, were synthesized via the mechanochemical method at room temperature. The samples were characterized using powder X-ray diffraction, infrared spectroscopy and thermal analysis. The results showed that the prepared products were carbonated apatites and no secondary phase was detected. The realization of the milling under a controlled atmosphere can lead to oxyapatites containing no carbonates. The ionic conductivity of the Sr₆La₄(PO₄)₂(SiO₄)₄O sample was investigated by using impedance spectroscopy. The highest ionic conductivity value of 1.522 × 10⁻⁶ S·cm⁻¹ was found at 800 °C. In the investigated temperature range, the activation energy is of 0.85 eV.     

Copper,cobalt and manganese: Modified hydrotalcite materials as catalysts for the selective catalytic reduction of NO with ammonia. The influence of manganese concentration

Hydrotalcites containing Cu, Co and Mn with varying manganese contents were prepared by co-precipitation. Manganese was also introduced into the catalysts via adsorption of an Mn–EDTA complex from an aqueous solution. The obtained samples were characterized by room- and high-temperature XRD, low-temperature nitrogen sorption, and FT–IR. Calcination of the catalysts at 500 °C resulted in the formation of mixed oxides with specific surface areas of 166–187 m²/g. The calcined samples were tested as catalysts for selective catalytic reduction of NO_x with ammonia. It was found that the Mn content strongly influences the product selectivity in SCR–NH₃. Mn–EDTA modified samples exhibited higher selectivity towards N₂ than Mn hydrotalcites obtained by the co-precipitation method. A hydrotalcite sample containing 5.4 wt% of manganese showed the highest catalytic activity and the lowest selectivity to N₂ at the same time.     

The effect of copper content on the reactivity of Cu/Co6Al2 solids in the catalytic steam reforming of methane reaction

The steam reforming of methane over Cu/Co₆Al₂ mixed oxides with different copper contents was studied. The Co₆Al₂ support was prepared via the hydrotalcite route. It was thermally stabilized at 500 °C, impregnated with 5 wt.%, 15 wt.% or 25 wt.% copper using copper (II) nitrate Cu(NO₃)₂·3H₂O precursor and then calcined again at 500 °C under an air flow. The impregnation of copper enhanced significantly the reactivity of the solids in the considered reaction. The 5Cu/Co₆Al₂ solid was the most reactive one, with a methane conversion of 96% at 650 °C. The selectivities of H₂ and CO₂ were also better for the catalyst containing 5 wt.% copper compared to higher copper loadings. The decrease in the catalytic reactivity with increasing the copper content was attributed to the formation of agglomerated and less reactive CuO species, which were detected by XRD and TPR analyses.     

Effects of calcination and activation temperature on dry reforming catalysts

The effect of calcination temperatures on dry reforming catalysts supported on high surface area alumina Ni/γ-Al₂O₃ (SA-6175) was studied experimentally. In this study, the prepared catalyst was tested in a micro tubular reactor using temperature ranges of 500, 600, 700 and 800 °C at atmospheric pressure, using a total flow rate of 33 ml/min consisting of 3 ml/min of N₂, 15 ml/min of CO₂ and 15 ml/min of CH₄. The calcination was carried out in the range of 500–900 °C. The catalyst is activated inside the reactor at 500–800 °C using hydrogen gas. It was observed that calcination enhances catalyst activity which increases as calcination and reaction temperatures were increased. The highest conversion was obtained at 800 °C reaction temperature by using catalyst calcined at 900 °C and activation at 700 °C. The catalyst characterization conducted supported the observed experimental results.     

Sensing characteristics of mixed-potential-type zirconia-based sensor using laminated-oxide sensing electrode

A planar sensor was fabricated using a yttria-stabilized zirconia (YSZ) plate and laminated-oxide sensing electrode (SE) aiming for selective detection of NO₂ at high temperature. The NO₂ sensing characteristics as well as the cross-sensitivity to various gases were examined in the temperature range of 700–900 °C under the wet condition (5 vol.% H₂O). It was found that the sensor attached with the laminated hetero-oxide layer (Cr₂O₃/NiO (+WO₃)) could detect NO₂ selectively at 895 °C. It was speculated that the additional oxide layer (Cr₂O₃) placed on the NiO (+WO₃) layer acted as a catalyst for the oxidation of CO, hydrocarbons and NO, and then led to better NO₂ selectivity.     

Cobalt-free cathode material SrFe0.9Nb0.1O3−δ for intermediate-temperature solid oxide fuel cells

A cobalt-free cubic perovskite oxide, SrFe_0.9Nb_0.1O_3?δ (SFN) was investigated as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD results showed that SFN cathode was chemically compatible with the electrolyte Sm_0.2Ce_0.8O_1.9 (SDC) for temperatures up to 1050 °C. The electrical conductivity of SFN sample reached 34–70 S cm^?1 in the commonly operated temperatures of IT-SOFCs (600–800 °C). The area specific resistance was 0.138 Ω cm² for SFN cathode on SDC electrolyte at 750 °C. A maximum power density of 407 mW cm^?2 was obtained at 800 °C for single-cell with 300 μm thick SDC electrolyte and SFN cathode.     

Separation of hydrogen from steam using a SiC-based membrane formed by chemical vapor deposition of triisopropylsilane

A silicon carbide-based membrane was formed in the macropores of an α-alumina support tube by chemical vapor deposition of triisopropylsilane at 700–800°C with a forced cross-flow through the porous wall. The membrane permeated gases except H₂O mainly by the Knudsen diffusion mechanism at permeation temperatures of 50–400°C. The H₂/H₂O selectivity was near or below unity because of the hydrophilic nature of the membrane. After a heat-treatment in Ar at 1000°C for 1 h, however, the membrane formed at a final evacuation pressure of 1 kPa exhibited a H₂/H₂O selectivity of 3–5, for a mixed feed of H₂–H₂O–HBr system, associated in a thermochemical water-splitting process. The H₂ permeance was (5–6)×10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 50–400°C. The membrane maintained the H₂/H₂O selectivity for more than 100 h in the H₂–H₂O–HBr mixture at 400°C.     

Cyanamide-derived non-precious metal catalyst for oxygen reduction

Cyanamide was used in the preparation series of metal–nitrogen–carbon (M–N–C) oxygen reduction catalysts. The best catalyst, treated at 1050 °C, shows good performance versus previously reported non-precious metal catalysts with an OCV ~ 1.0 V and a current density of 105 mA/cm² (iR-corrected) at 0.80 V in H₂/O₂ fuel cell testing (catalyst loading: 4 mg cm^? 2). Although nitrogen content has been previously correlated positively with ORR activity, no such trend is observed here for any nitrogen type. The combined effects of nitrogen and sulfur incorporation into the carbon may account for the high activity of the 1050 °C catalyst.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO₂ nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl₂ · 2H₂O in ethylene glycol at 195 °C for 4 h under vigorous stirring in air. The as-prepared SnO₂ nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g⁻¹ beyond 100 cycles.     

Thermal degradation and evolved gas analysis: A polymeric blend of urea formaldehyde (UF) and epoxy (DGEBA) resin

A polymeric blend has been prepared using urea formaldehyde (UF) and epoxy (DGEBA) resin in 1:1 mass ratio. The thermal degradation of UF/epoxy resin blend (UFE) was investigated by using thermogravimetric analyses (TGA), coupled with FTIR and MS. The results of TGA revealed that the pyrolysis process can be divided into three stages: drying process, fast thermal decomposition and cracking of the sample. There were no solid products except ash content for UFE during combustion at high temperature. The total mass loss during pyrolysis at 775 °C is found to be 97.32%, while 54.14% of the original mass was lost in the second stage between 225 °C and 400 °C. It is observed that the activation energy of the second stage degradation during combustion (6.23 × 10⁻⁴ J mol⁻¹) is more than that of pyrolysis (5.89 × 10⁻⁴ J mol⁻¹). The emissions of CO₂, CO, H₂O, HCN, HNCO, and NH₃ are identified during thermal degradation of UFE.     

Impact of reforming catalyst on the anodic polarisation resistance in single-chamber SOFC fed by methane

This paper emphasises the electrochemical and catalytic properties of a Ni–10% GDC (10% gadolinium-doped ceria) cermet anode of a single-chamber solid oxide fuel cell (SC-SOFC). Innovative coupling of electrochemical impedance spectroscopy with gas chromatography measurements was carried out to characterise the anode material using an operando approach. The experiments were conducted in a symmetric anode/electrolyte/anode cell prepared by slurry coating resulting in 100 μm-thick anode layers. The electrochemical performance was assessed using a two-electrode arrangement between 400 °C and 650 °C, in a methane-rich atmosphere containing CH₄, O₂ and H₂O in a 14:2:6 volumetric ratio. The insertion of a Pt–CeO₂ based catalyst with high specific surface area inside the cermet layer was found to promote hydrogen production from the Water Gas Shift reaction and consequently to improve the electrochemical performances. Indeed, a promising polarisation resistance value of 12 Ω cm² was achieved at 600 °C with a catalytic loading of only 15 wt.%.