Mixed Nitrate Research Articles

High primary productivity and f-ratio in summer in the Ulleung basin of the East/Japan Sea

To better understand the cause of high summer primary productivity in the Ulleung Basin located in the southwest part of the East/Japan Sea, the spatial dynamics of primary, new, and regenerated productivities (PP, NP, and RP) were examined along the path of the Tsushima Warm Current system in summer 2008. We compared hydrographic and chemical parameters in the Ulleung Basin with those of the Kuroshio Current in the Western Pacific Ocean and the East China Sea. In summer, integrated primary productivity (IPP, 0.37–0.96gCm−2d−1) and integrated new productivity (INP, 26–221mgNm−2d−1) within the euphotic zone in the Ulleung Basin were higher than those in the East China Sea and the Western Pacific Ocean (0.17–0.28gCm−2d−1, 2−5mgNm−2d−1, respectively). In contrast, there was no pronounced spatial variation in integrated regenerated productivity (IRP, 43–824mgNm−2d−1). Strong positive correlations between IPP and INP (also the f-ratio), and between nitrate uptake rate in the mixed layer and nitrate upward flux through the top of pycnocline in summer in the Ulleung Basin imply that the high IPP was mainly supported by supply of nitrate from the underlying water in the euphotic zone. Shallowing of the pycnocline depth as the current enters the East/Japan Sea facilitates nitrate supply from the nutrient-replete cold water immediately below the pycnocline through nitrate upward flux. A subsurface maximum in PP at or above the pycnocline and a high f-ratio further support the importance of this source of nitrate for maintaining the high summer PP in the Ulleung Basin. In comparison, the high PP layer was observed at the surface in the following fall and spring in the Ulleung Basin. Our results demonstrate the importance of hydrographic features in enhancing PP in this oligotrophic Tsushima Warm Current system.

Enhancement of nitrate removal from a solution of mixed nitrate, chloride and sulfate ions using a nitrate-selective carbon electrode

A nitrate-selective carbon electrode (NSCE) was fabricated to remove nitrate ions selectively from a solution of mixed anions. The NSCE was prepared by coating anion-exchange resin powder with a high selectivity toward nitrate ions on a carbon electrode surface. We performed desalination experiments on a solution of mixed chloride, nitrate and sulfate ions using a CDI cell (NSCE cell) constructed with the NSCE. The desalination results were compared with the results obtained in a CE cell containing an uncoated carbon electrode (CE). According to the adsorption equilibrium tests, the BHP55 resin had a preference for ions in the order nitrate≫sulfate>chloride. The desalination experiments were performed by applying a constant current until the cell potential reached 1.0V. The total amount of ions adsorbed in the NSCE cell was approximately 34% higher than that in the CE cell. The amount of nitrate ions adsorbed in the NSCE cell was approximately 2-fold higher value than that in the CE cell. However, the amount of adsorbed chloride and sulfate ions was similar in the two cells. These results show that the fabricated NSCE was effective at enhancing the removal of nitrate ions from a mixed solution.

Complexation of trace metals in size-segregated aerosol particles at nine sites in Germany

The complexation of trace metal ions (TMI) was studied in size-segregated ambient aerosol particles collected at nine sites in Germany (urban, rural and coastal). Samples were analysed in terms of TMI (Fe, Mn, Cu), potential inorganic and organic ligands and pH. Using a thermodynamic model (E-AIM III), the concentrations of these compounds in the particle liquid phase were estimated. The resulting liquid phase concentrations were then used as input parameters for a speciation model (Visual MINTEQ) and the equilibrium complexation was calculated under realistic conditions. The complexation was found to be controlled by the availability of strong organic ligands, especially oxalate, whose occurrence in turn was governed by the formation of insoluble Ca-oxalate. Likewise, the pH influenced oxalate availability because it alters the concentrations of the chelating mono- and dianions. As a qualitative result, Fe3+ was found to be mainly complexed by oxalate, while Fe2+ and Mn2+ were rather associated with nitrate. Cu2+ showed mixed organic and nitrate complexation. Complexation by HULIS was only significant for Fe3+ and Cu2+ and was generally less important than other ligands like oxalate and nitrate. Oxalate was found to exist mainly in the solid phase while higher dicarboxylic acids mostly did not form complexes due to protonation. Complexation was shown to be influenced by season, air mass origin, particle size and sampling site.

Atomistic Simulation of Orientation Dependence in Shock-Induced Initiation of Pentaerythritol Tetranitrate

The dependence of the reaction initiation mechanism of pentaerythritol tetranitrate (PETN) on shock orientation and shock strength is investigated with molecular dynamics simulations using a reactive force field and the multiscale shock technique. In the simulations, a single crystal of PETN is shocked along the [110], [001], and [100] orientations with shock velocities in the range 3-10 km/s. Reactions occur with shock velocities of 6 km/s or stronger, and reactions initiate through the dissociation of nitro and nitrate groups from the PETN molecules. The most sensitive orientation is [110], while [100] is the most insensitive. For the [001] orientation, PETN decomposition via nitro group dissociation is the dominant reaction initiation mechanism, while for the [110] and [100] orientations the decomposition is via mixed nitro and nitrate group dissociation. For shock along the [001] orientation, we find that CO-NO(2) bonds initially acquire more kinetic energy, facilitating nitro dissociation. For the other two orientations, C-ONO(2) bonds acquire more kinetic energy, facilitating nitrate group dissociation.

Synthesis of Homogeneous MgAl2O4 Spinel Using Atmospheric Pressure Solvothermal Process

Spinel structure MgA12O4 is an important compound oxide for de-sulfur catalysts or electronic devices. There had been proposed so many-kinds of synthesis routes for MgAl2O4, however, it is still very difficult to get a pure and stoichiometric MgAl2O4 powder with high specific surface area. The authors approached by using atmospheric solvothermal synthesis with mixed nitrate solution adding monomer, dimer and trimer of glycol. The MgAl2O4 powder was successfully synthesized by the process and the glycols were recognized to play an important role of the reduction agent of nitric acid group to deposit uniform precursor.

Preparation of Ru/Ba-ZrO2Catalyst and Its Performance for Ammonia Synthesis

分别采用柠檬酸络合法、改性共沉淀法和湿浸渍法制备了掺Ba纳米ZrO2材料,负载Ru后用于催化氨合成反应.采用X射线衍射、CO2程序升温脱附（CO2-TPD）、N2物理低温吸附、H2程序升温还原技术（H2-TPR）、扫描电镜（SEM）、透射电镜（TEM）、X射线光电子能谱（XPS）和CO化学吸附对载体材料和催化剂进行了表征.结果表明,不同方法制备载体的物相结构和织构性能均有明显差别,负载Ru后催化剂的氨合成性能差别也较大.其中,以柠檬酸络合法制备的载体材料中Ba以BaZrO3的形式存在,钙钛矿型BaZrO3具有较强的供电子能力,电子可以通过Ru与载体间强相互作用传递到Ru表面,有效地促进N≡N的断裂,使催化剂的低温活性显著提高.在425℃,3 MPa,空速为10000 h-1条件下,出口氨浓度为5.72%.其氨合成活性分别是改性共沉淀法和湿浸渍法制备催化剂的3.8倍和14.3倍.

Controlled synthesis and magnetic properties of monodisperse Ni1−xZnxFe2O4/MWCNT nanocomposites via microwave-assisted polyol process

Ni1−xZnxFe2O4/MWCNT nanocomposites (x=0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) with controllable composition have been successfully synthesized via microwave-assisted polyol process using triethylene glycol solution (TREG) as solvent. Experimental results demonstrated that monodisperse face-centered cubical Ni1−xZnxFe2O4 nanoparticles with average size (6nm) had been attached on the MWCNTs. The composition of ferrite nanoparticles can be controlled through adjusting the atomic ratios of the nickel and zinc salts in the mixed nitrate solution. The magnetic properties of nanocomposites with different Zn contents were measured by vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of Ni1−xZnxFe2O4/MWCNT nanocomposites gradually increases when the x is less than 0.5 while decreases when the x is larger than 0.5. Ms reached maximum value when the x is 0.5. The coercivity (Hc) of nanocomposites is low at room temperature, which exhibits characteristic of superparamagnetic.

Contributions of individual reactive biogenic volatile organic compounds to organic nitrates above a mixed forest

Abstract. Biogenic volatile organic compounds (BVOCs) can react in the atmosphere to form organic nitrates, which serve as NOx (NO + NO2) reservoirs, impacting ozone and secondary organic aerosol production, the oxidative capacity of the atmosphere, and nitrogen availability to ecosystems. To examine the contributions of biogenic emissions and the formation and fate of organic nitrates in a forest environment, we simulated the oxidation of 57 individual BVOCs emitted from a rural mixed forest in northern Michigan. Key BVOC-oxidant reactions were identified for future laboratory and field investigations into reaction rate constants, yields, and speciation of oxidation products. Of the total simulated organic nitrates, monoterpenes contributed ~70% in the early morning at ~12 m above the forest canopy when isoprene emissions were low. In the afternoon, when vertical mixing and isoprene nitrate production were highest, the simulated contribution of isoprene-derived organic nitrates was greater than 90% at all altitudes, with the concentration of secondary isoprene nitrates increasing with altitude. Notably, reaction of isoprene with NO3 leading to isoprene nitrate formation was found to be significant (~8% of primary organic nitrate production) during the daytime, and monoterpene reactions with NO3 were simulated to comprise up to ~83% of primary organic nitrate production at night. Lastly, forest succession, wherein aspen trees are being replaced by pine and maple trees, was predicted to lead to increased afternoon concentrations of monoterpene-derived organic nitrates. This further underscores the need to understand the formation and fate of these species, which have different chemical pathways and oxidation products compared to isoprene-derived organic nitrates and can lead to secondary organic aerosol formation.

Physical and chemical properties of the regional mixed layer of Mexico's Megapolis Part II: evaluation of measured and modeled trace gases and particle size distributions

Abstract. This study extends the work of Baumgardner et al. (2009) in which measurements of trace gases and particles, at a remote, high altitude mountain site, 60 km from Mexico City were analyzed with respect to the origin of the air masses. In the current evaluation, the temperature, water vapor mixing ratio (WMR), ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2) and acyl peroxy nitrate (APN) are simulated with the WRF-Chem chemical transport model and compared with the measurements at the mountain site. Comparisons between the model and measurements are also evaluated for particle size distributions (PSDs) of the mass concentrations of sulfate, nitrate, ammonium and organic mass (OM). The model predictions of the diurnal trends in temperature, WMR and trace gases were generally well correlated; 13 of the 18 correlations were significant at a confidence level of <0.01. Less satisfactory were the average hourly differences between model and measurements that showed predicted values within expected, natural variation for only 10 of the 18 comparisons. The model performed best when comparing with the measurements during periods when the air originated from the east. In that case all six of the parameters being compared had average differences between the model and measurements less than the expected standard deviation. For the cases when the air masses are from the southwest or west northwest, only two of the comparisons from each case showed differences less than the expected standard deviation. The differences appear to be a result of an overly rapid growth of the boundary layer predicted by the model and too much dilution. There also is more O3 being produced, most likely by photochemical production, downwind of the emission sources than is predicted by the model. The measured and modeled PSD compare very well with respect to their general shape and the diameter of the peak concentrations. The spectra are log normally distributed with most of the mass in the accumulation mode centered at 200 ± 20 nm and little observed or predicted changes with respect to the time when the RML is above the Altzomoni research station. Only the total mass changes with time and air mass origin. The invariability of average diameter of the accumulation mode suggests that there is very little growth of the particles by condensation or coagulation after six hours of aging downwind of the major sources of anthropogenic emissions in Mexico's Megapolis. This could greatly simplify parameterization in climate models although it is not known at this time if this invariance can be extended to other megacity regions.

Aerosol scattering and absorption during the EUCAARI-LONGREX flights of the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146: can measurements and models agree?

Abstract. Scattering and absorption by aerosol in anthropogenically perturbed air masses over Europe has been measured using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM) on 14 flights during the EUCAARI-LONGREX campaign in May 2008. The geographical and temporal variations of the derived shortwave optical properties of aerosol are presented. Values of single scattering albedo of dry aerosol at 550 nm varied considerably from 0.86 to near unity, with a campaign average of 0.93 ± 0.03. Dry aerosol optical depths ranged from 0.030 ± 0.009 to 0.24 ± 0.07. An optical properties closure study comparing calculations from composition data and Mie scattering code with the measured properties is presented. Agreement to within measurement uncertainties of 30% can be achieved for both scattering and absorption, but the latter is shown to be sensitive to the refractive indices chosen for organic aerosols, and to a lesser extent black carbon, as well as being highly dependent on the accuracy of the absorption measurements. Agreement with the measured absorption can be achieved either if organic carbon is assumed to be weakly absorbing, or if the organic aerosol is purely scattering and the absorption measurement is an overestimate due to the presence of large amounts of organic carbon. Refractive indices could not be inferred conclusively due to this uncertainty, despite the enhancement in methodology compared to previous studies that derived from the use of the black carbon measurements. Hygroscopic growth curves derived from the wet nephelometer indicate moderate water uptake by the aerosol with a campaign mean f(RH) value (ratio in scattering) of 1.5 (range from 1.23 to 1.63) at 80% relative humidity. This value is qualitatively consistent with the major chemical components of the aerosol measured by the aerosol mass spectrometer, which are primarily mixed organics and nitrate and some sulphate.

Waveguide terahertz time-domain spectroscopy of ammonium nitrate polycrystalline films

We report temperature-dependent measurements of the terahertz (THz) vibrational spectrum of ammonium nitrate (AN) films and mixed potassium nitrate (KN)–ammonium nitrate films using waveguide THz time domain spectroscopy. The experiments were performed on polycrystalline films on the metal surface of a parallel plate waveguide. At cryogenic temperature and with frequency resolution as high as 7 GHz, our measurements produce a complex vibrational spectrum for AN, and show vibrational resonances not observed in previous far infrared and Raman measurements. We investigate potential interactions between AN and the metal surface by measuring THz spectra of films on aluminum, gold, and a gold surface coated with an organic self-assembled monolayer. Measurements are also performed on a deuterated AN film and indicate that the observed THz modes are due largely to the motion of the nitrate ions in the AN crystal. Finally, the effect of introducing small amounts of an impurity into the AN lattice is examined. We find that introduction of as little as 1%-2% by weight of potassium nitrate into the AN lattice causes line broadening of the THz modes, which is consistent with increased disorder introduced by the impurity.

Electron paramagnetic resonance and photoluminescence properties of α-Al2O3:Cr3+ phosphors

The red emitting Cr3+ activated α-Al2O3 powder phosphor has been prepared by easy combustion reactions from mixed metal nitrate reactants and urea with ignition temperatures of 500 °C. The as-synthesized powder was characterized by X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared techniques. The X-ray diffraction pattern reveals that the phosphor crystallized in the hexagonal α-Al2O3 phase directly from the combustion reaction. The EPR spectrum exhibits an intense resonance signal with effective g value at g=3.33 along with a few weak resonance signals with effective g values at g=13.7, 2.34, 1.95, 1.49, and 1.26. The spin concentration (N) and its paramagnetic susceptibility (χ) have been evaluated. The excitation spectrum consists of two broad intense bands at 415 nm and 555 nm and are assigned to 4A2g (F)→4T1g (F) and 4A2g (F)→4T2g (F) transitions, respectively. The intense fluorescence peak around 691 nm is attributed to 2E g →4A2g transition of Cr3+ ion. By correlating EPR and optical data, the crystal field splitting parameter (Dq), Racah inter-electronic repulsion parameter (B) have been evaluated and discussed. The EPR and optical studies reveal that Cr3+ ions are occupying in Al3+ sites in octahedral coordination.

Precipitation of silver/palladium alloy platelets from homogeneous solutions

Dispersed silver/palladium (Ag/Pd) nanoplatelets were prepared by delivering in parallel solutions of mixed metal nitrates and L-ascorbic acid into a nitric acid solution containing Arabic gum. The shape and size of bimetallic nanoparticles varied with the silver/palladium weight ratio and the concentration of nitric acid. The optimum conditions for platelets formation were a palladium content of ∼2.0wt.% and nitric acid concentrations above 1.0moldm−3. The data presented show that both parameters play a critical role in the nucleation and growth of AgPd particles. A mechanism explaining the formation of the bimetallic nanoplatelets is proposed.

Synthesis, morphology and spectroscopy of Nd:GSAG nano-powders

Nd3+-doped gadolinium scandium aluminum garnet (Nd:GSAG) precursors were obtained from a mixed nitrate solution with precipitant of ammonium hydrogen carbonate. The precursors were sintered at different temperatures and the phase developments in heat treatments were investigated through methods of XRD and IR, showing the precursors transformed to pure-GSAG phase with no intermediate phases appeared at 900°C. The TEM observation revealed that the powders sintered at 900–1000°C were well-dispersed with average crystalline sizes of 30–80nm. Photoluminescence analysis of the Nd:GSAG nano-powders showed that the PL intensities changing significantly with the Nd3+ doping concentration, and the concentration quenching was observed as the Nd3+ concentration reached to 1.5at.%.

Spray Pyrolysis Synthesis of Mesoporous Lithium-Nickel-Manganese-Oxides for High Energy Li-Ion Batteries

Uniform, spherical powders consisting of nanostructured Li-excess Li(1+x)Ni0.25Mn0.75O(2.25+x/2) (0.375 ≤ x ≤ 0.5) were synthesized via a spray pyrolysis approach using mixed nitrate precursors. Among the materials produced, the layered Li1.5Ni0.25Mn0.75O2.5 (R3̅m) attained a capacity of over 250 mAhg−1, which is comparable to that of the Li-excess cathode materials produced via coprecipitation. Li content was varied and found to affect the crystal structure, morphology and electrochemical properties of the materials, and the sintering temperature increased with Li content. Li2MnO3-type structures were observed on XRD diffraction patterns at high annealing temperatures for x < 0.5 due to a phase transformation. The Li2MnO3-type structures degraded the electrochemical performance of these materials due to the high kinetic barrier for Li transportation. In particular, Li1.5Ni0.25Mn0.75O2.5 annealed at 800°C and Li1.375Ni0.25Mn0.75O2.4375 annealed at 700°C predominately adopted a layered composite structure. Nano-domains (5∼10 nm) of spinel structure were observed by HR-TEM to be structurally integrated with the layered structure for Li1.375Ni0.25Mn0.75O2.4375 annealed at 700°C. Nonetheless, the layered Li1.5Ni0.25Mn0.75O2.5 materials showed the best performance in terms of capacity, cycleability and rate-capability among these materials. The superior rate capability of these materials is aided by the nano-structured morphology, which consists of nano-sized primary particles and highly porous secondary particles.

Solvent-free synthesis of oxides for CuInSe2 thin films fabrication

A low-cost non-vacuum process for fabrication of CuInSe2 (CIS) films by solvent-free mechanochemical method and spin-coating process is described. First, highly monodisperse Cu, In oxides nanoparticles are synthesized via a facile, solvent-free route, which is the first applied in the CIS solar cells. Second, the oxide particulate precursors are deposited in a thin layer by spin-coating technique. Finally, the dry layers are sintered into CIS thin films with composition control by sequential reduction and selenization. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), it is found that near stoichiometric CIS films with a micron-sized dense grains are obtained in our work. Three types of mixed nitrates are used to fabricate oxides, the influence of the degree of mixing on the CIS films have been investigated.

Copper(I)/(II) or silver(I) ions towards 2-mercaptopyrimidine: An exploration of a chemical variability with possible biological implication

Direct reaction of copper(I) chloride with 2-mercaptopyrimidine (pmtH) in the presence of the triphenylphosphine (tpp) in 1:1:2M ratio forms the mixed ligand Cu(I) complex with formula [CuCl(tpp)2(pmtH)] (1). The dimeric {[Cu(tpp)(pmt)]2 0.5(MeOH)} (2) complex was derived from the reaction of 1 with twofold molar amount of sodium hydroxide. However, the reaction of copper(II) sulfate or nitrate with pmtH and tpp in 1:2:2M ratio, unexpectedly results in the formation of the [CuSH(tpp)2(pmtH)] (3) complex. Further studies have shown that the [Cu(tpp)2(pmt)] (4) complex is formed by reacting copper(II) acetate with pmtH in the presence of tpp in 1:2:2M ratio, while in the absent of tpp, the Cu(CH3COO)2 or CuSO4 is found to oxidizes pmtH to its corresponding disulfide (pmt)2. For comparison the mixed ligand silver(I) chloride or nitrate complexes with formula [AgCl(tpp)2(pmtH)] (5) or [Ag(NO3)(tpp)2(pmtH)] (6) are also synthesized by reacting of the AgCl or AgNO3 with pmtH and tpp in 1:2:2M ratio. The complexes have been characterized by elemental analyses, m.p., vibrational spectroscopy (mid-, far-FT-IR and Raman), 1H NMR, UV–Vis, ESI-MS, TG–DTA spectroscopic techniques and single crystal X-ray crystallography at ambient conditions. Photolysis of 1–6, was also studied and the results showed formation of triphenylphosphine oxide. The complexes 1–6, were used to study their influence upon the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX) experimentally and theoretically. The binding of 1–4 with LOX was also investigated by saturation transfer difference 1H NMR experiments (STD).

Anion Exchange Reaction Potentials as Approximate Estimates of the Relative Thermodynamic Stabilities of Mg/Al Layered Double Hydroxides Containing Different Anions

Coatings of hydrotalcite-like nitrate-intercalated Mg/Al layered double hydroxides are electrochemically deposited on a Pt electrode by electrogeneration of base by reduction of a mixed metal nitrate aqueous solution. As-prepared coatings are stable to workup and function as rugged electrodes. The voltammetric response generated by anion exchange of intercalated nitrate for dissolved anions from solution under equilibrium conditions is employed to estimate the thermodynamic stabilities of the Mg/Al layered double hydroxides comprising different anions relative to the nitrate-containing phase. Among monovalent anions, the most stable is the fluoride-containing LDH (ΔG° = -48.7 kJ mol(-1)) relative to the nitrate-containing LDH. The stability in aqueous phase decreases as F(-) > Cl(-) > Br(-) > NO(2)(-) > NO(3)(-), whereas, among divalent anions, SO(4)(2-) (ΔG° = -8.7 kJ mol(-1)) > CO(3)(2-) (ΔG° = 14.3 kJ mol(-1)). The results of monovalent ions match well with the Miyata series, whereas the divalent anion series is at variance with the commonly held belief that carbonate-LDHs are more stable than sulfate-LDHs.

(Gd&lt;sub&gt;0.95&lt;/sub&gt;Eu&lt;sub&gt;0.05&lt;/sub&gt;)(OH)&lt;sub&gt;3&lt;/sub&gt; Nanomaterials via Hydrothermal Processing and their Transformation into Single Crystalline (Gd&lt;sub&gt;0.95&lt;/sub&gt;Eu&lt;sub&gt;0.05&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; with Enhanced Photoluminescence

In this work, hexagonal solid solutions of (Gd0.95Eu0.05)(OH)3with two distinctive morphologies of nanorods and nanotubes were successfully synthesized via hydrothermal treatment of mixed nitrate solutions in the presence of ammonium hydroxide. The hydroxide samples exhibited characteristic Eu3+photoluminescence through the energy transfer from Gd3+to Eu3+and the self-excitation of Eu3+. The hydroxide precursors transformed into cubic (Gd0.95Eu0.05)2O3at ~500 °C via an intermediate monoclinic (Gd0.95Eu0.05)OOH phase, and the Eu3+coordination accordingly experienced symmetry changes fromD3htoC2v, and then toC2/S6. The cubic (Gd0.95Eu0.05)2O3well retained the original morphologies of their polycrystalline precursors and exhibited a single-crystalline character at 1000 °C. Greatly enhanced photoluminescence (~5000 times that of the hydroxides) was observed for the phase conversion.

Application of Mixed Oxide Catalysts to the Removal of Lean NO&lt;SUB&gt;&lt;I&gt;x&lt;/I&gt;&lt;/SUB&gt; and N&lt;SUB&gt;2&lt;/SUB&gt;O Using Transient-Mode Cyclic Operations

The storage and reduction of NO and N2O in the presence of excess O2 have been investigated over two mixed oxide catalysts. The catalysts, which were prepared via coprecipitation of solutions of mixed metal nitrates, followed by calcination, were found to have plenty storage capacities for nitrogen oxides. The storage and reduction performances varied with the catalyst composition and the duration of cycle time: the AlCoPd (1/1/0.05) mixed oxide catalyst exhibited higher efficiency for NO, and an AlCoFe (1/1/2) mixed oxide catalyst exhibited higher efficiency for N2O. The adsorptions of NO and N2O onto the mixed oxide catalysts progressed without an oxidation step, and the adsorptivity of NO surpassed that of O2. The mixed oxides showed spinel structures with sizes of 10-100 nm, and with well-developed mesopores that were formed by the evaporation of H2O and CO2 from layered double hydroxide (LDH) precursors. The storage and reduction of lean NOx and N2O over the mixed oxide catalysts were carried out via cyclic operations in a transient mode at 300 degrees C and at space velocities of around 30,000 h(-1). The removal efficiency of the cyclic operations generally increased with reduced adsorption cycle time, and reached 90% for NOx and N2O with the respective catalysts.