Deactivation of barium oxide-based NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> storage and reduction catalyst by hydrothermal treatment

The deactivation of a barium oxide-based NO _x storage and reduction (NSR) catalyst with hydrothermal treatment was studied by treating it with 10 vol% water vapor diluted in nitrogen at 850°C. XRD, XPS, SEM, IR of CO adsorption, and the N₂ adsorption was used to investigate the physical and chemical changes of the NSR catalyst caused by the hydrothermal treatment. The 12 h hydrothermal treatment decreased its NO₂ storage capacity by 20%. However, the hydrothermal treatment significantly decreased its ability to reduce the stored NO₂. The formation of an inactive phase consisting of platinum and aluminum is believed to be the cause of the severe deactivation of the NSR catalyst.     

Industrial test on coal re-burning at a 600 MW utility boiler and NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> reduction

This research conducts a series of industrial tests on coal reburning of a 600 MW pulverized coal boiler firing lignite, which is one part of a coal reburning demonstration project. When running steadily under 600 MW load, the boiler has an average NO _x emission of 274 mg/m³ (O₂ content in flue gas is converted to 6%), the NO _x emission is reduced by 65.36%. In the meanwhile, loss of ignition (LOI) under coal reburning rarely increases. Three operation conditions — traditional air feeding, air staging and coal reburning — are realized, respectively, during the industrial tests, and the results indicate that coal reburning has the lowest NO _x emission, while the traditional air feeding has the highest NO _x emission. Under the test conditions, the higher the proportion of the reburning coal, the higher the NO _x control can reach. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Electrochemical oxidation of an acid dye by active chlorine generated using Ti/Sn<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Ir<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> electrodes

The generation of active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes, with different compositions of Ir (x = 0.01, 0.05, 0.10 and 0.30 ), was investigated by controlled current density electrolysis. Using a low concentration of chloride ions (0.05 mol L⁻¹) and a low current density (5 mA cm⁻²) it was possible to produce up to 60 mg L⁻¹ of active chlorine on a Ti/Sn_0.99Ir_0.01O₂ anode. The feasibility of the discoloration of a textile acid azo dye, acid red 29 dye (C.I. 16570), was also investigated with in situ electrogenerated active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes. The best conditions for 100% discoloration and maximum degradation (70% TOC reduction) were found to be: NaCl pH 4, 25 mA cm⁻² and 6 h of electrolysis. It is suggested that active chlorine generation and/or powerful oxidants such as chlorine radicals and hydroxyl radicals are responsible for promoting faster dye degradation. Rate constants calculated from color decay versus time reveal a zero order reaction at dye concentrations up to 1.0 × 10⁻⁴ mol L⁻¹. Effects of other electrolytes, dye concentration and applied density currents also have been investigated and are discussed.     

NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> emission from incineration of organic liquid waste in a circulating fluidized bed

An incineration test of a toxic chemical organic waste liquid was conducted on a circulating fluidized bed (CFB) incinerator. The flue gas was measured online with the advanced SAE-19 flue gas analyzer. The effects of several factors, in terms of flow rate of waste liquid, ratio of waste liquid injected into dense bed of the CFB, excess air coefficient, the secondary air fraction and bed temperature on NO _x emissions, were verified. The experimental results show that NO emissions in flue gas increase with increase in the flow rate of the waste liquid injected into the bed or the excess air coefficient or the bed temperature and those decrease with increase in the ratio of waste liquid injected into the dense bed of the CFB or the secondary air fraction. During the test runs, NO _x concentration in flue gas met the national regulation on NO _x emissions due to suppressive effect of low temperature and staged combustion in CFB on NO _x formation. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Bulk and Surface Properties of Dispersed CuO Phases in Relation with Activity of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Reduction

Synthesized silicas modified with alumina, titania, and zirconia (about 13% wt) were used as supports for dispersing nanosized CuO phase. All the prepared catalysts, containing about 1 mmol_cu g_cat ^-1 possessed high surface areas (230–430 m²g_cat ^-1) and homogeneous coverage of the relevant support, as revealed by SEM-EDS analysis. The nature of the support and its acidity directed the CuO deposition modifying the dimensions of the CuO aggregates and the ratio between highly and scarcely interacting copper species with support, as revealed by complementary analyses. The redox character of the CuO phase was studied realizing cycles of programmed temperature reduction/oxidation (TPR-TPO) which gave the extent of CuO reduction and CuO re-oxidation. Deconvolution of the reduction profiles permitted identifying different copper species which presence depended on the support nature. Attempts were made to individuate relations between the properties of the CuO species and catalytic activity in NO _x reduction with ethene (HC-SCR process) in highly oxidant atmosphere. The CuO phase deposited on the most acidic supports showed the best activity and selectivity in the NO _x reduction.     

Particle deposition behaviors of monolithic De-NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> catalysts for selective catalytic reduction (SCR)

A major issue when using selective catalytic reduction (SCR) De-NO _x catalysts is the risk of physical deactivation due to particle deposition and plugging of the monolithic catalysts. In the present study, numerical computations were carried out to investigate the particle deposition behaviors in monolithic SCR catalysts. Based on the calculation results, the effects of particle diameter, particle density, gas velocity, turbulent intensity, chemical reaction and channel size on particle deposition were analyzed in detail. Increasing gas velocity and equivalent diameter of channel can mitigate particle deposition. The increases of turbulent intensity and channel length both lead to the rise of particle deposition ratio. For particles with high Stokes number, particle deposition mainly takes place in the inlet section of catalysts. For particles with low Stokes number, sediment can be observed in the middle and outlet sections of catalysts. De-NO _x chemical reaction can mitigate particle deposition, but the effect of chemical reaction on particle deposition is inactive.     

Preparation and characterization of RuO<Subscript>2</Subscript> · <Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O/carbon aerogel composites for supercapacitors

A series of RuO₂ · xH₂O/carbon aerogel (CA) composite electrode materials was prepared by a chemical precipitation method. Ultrasonication was used to accelerate the chemical reaction and improve the dispersion of RuO₂ · xH₂O particles on the surface and the pores of the aerogel. The structure and morphology of the as-prepared composite were characterized by N₂ adsorption isotherm, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM). The results showed that the CA had a pearly network structure and the composites had a relatively high specific surface area and mesopore volume. The electrochemical performance of the composite electrodes was studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance measurements. The results indicated a substantial increase in the specific capacitance of the composite. Moreover, the utilization efficiency of RuO₂ · xH₂O was greatly improved by loading it on the conductive and porous CA due to a significant improvement in the inter-particle electronic conductivity and the extensive mesoporous network of the composites.     

Soil bio-functioning under <Emphasis Type="Italic">Acacia nilotica</Emphasis> var. <Emphasis Type="Italic">tomentosa</Emphasis> protected forest along the Senegal River

Acacia nilotica var. tomentosa trees from the Diarra protected forest located in the Senegal River valley were identified for the assessment of both biological nitrogen fixation, using the natural abundance method, and soil bio-functioning parameters (nodulation, root biomass, total microbial biomass, and potential N mineralization). The presence and the genetic diversity of indigenous rhizobia nodulating A. nilotica var. tomentosa was also investigated, taking into account distance from the trunk (0, 1, 2, and 3 m) and depth (0–25, 25–50, and 50–75 cm). Surprisingly, no nodules on the trees root systems were found, whereas under laboratory conditions the presence of indigenous rhizobia nodulating A. nilotica var. tomentosa was demonstrated in the analyzed soils (90% of the nodules harvested on the trapped plants were occupied by the same Inter-Genic Spacer (IGS) group, IGS1). There was no significant influence of trees and/or depth on total microbial biomass and potentials of nitrogen mineralization. Some assumptions were formulated on the possible combined effect of flooding, which usually occurs annually during 4–7 months, and the clayey soils in the Diara forests. Although a deeply natural nodulation of A. nilotica var. tomentosa trees by indigenous rhizobia is not excluded, but it still remains to be demonstrated.     

Effect of calcination temperature on the characteristics of SO<Emphasis Type="Italic">sk</Emphasis>4/2-/TiO<Subscript>2</Subscript> catalysts for the reduction of NO by NH<Subscript>3</Subscript>

The catalytic activity of sulfated titania (ST) calcined at a variety of temperatures has been investigated for selective catalytic reduction (SCR) of NO by NH₃. The NO removal activity of ST catalyst mainly depends on its sulfur content, indicating critical role of sulfur species on the surface of TiO₂. The role of sulfur is mainly the formation of acid sites on the catalyst surface. The presence of both BrØnsted and Lewis acid sites on the surface of sulfated titania has been identified by IR study with the adsorption of NH₃ and pyridine on ST. The reduction of the intensity of IR bands representing BrØsted acid sites is more pronounced than that revealing Lewis acid sites as the calcination temperature increases. It has been further clarified by IR study of ST500 catalyst evacuated at a variety of temperatures. The NO removal activity also decreases with the increase of the catalyst calcination temperature. It simply reveals that BrØnsted acid sites induced by sulfate on the catalyst surface are primarily responsible for the enhancement of catalytic activity of ST catalyst containing sulfur for NO reduction by NH₃.     

Low-temperature CO oxidation of Pt/Al<Subscript>0.1</Subscript>Ce<Subscript>0.9</Subscript>O<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> catalysts: Effects of supports prepared with different precipitants

We prepared 0.1Al-0.9Ce supports using various precipitants such as NH₄OH, KOH, NaOH, K₂CO₃, and Na₂CO₃ to prepare Pt-based CO oxidation catalysts. Of the studied catalysts, the Pt/0.1Al-0.9Ce_NH₄OH catalyst showed the optimum activity for CO oxidation. Catalysts prepared with carbonate-form precipitants revealed relatively lower activity than carbonate-free precipitants. A temperature at 50% CO conversion of all samples was observed in the low-temperature region in the presence of water vapor because of the promotional effect of the water-gas shift reaction. Several characterization results revealed that catalytic activity was related to oxygen capacity and Pt dispersion was attributable to precipitant nature.     

Ph<Subscript>2</Subscript>Zn-metallocene-MAO initiator systems in the homo- and copolymerization of styrene/<Emphasis Type="Italic">p</Emphasis>-alkylstyrene

Summary The homo- and copolymerization of styrene (S) with p-methylstyrene (p-MeS) and p-tert-butylstyrene (p-Bu^tS) has been tested using initiator systems of the Ph₂Zn-metallocene-MAO type. The metallocenes used were CpTiCl₃, IndTiCI₃, (n-BuCp)₂TiCl₂, Ind₂ZrCl₂ and Et(Ind)₂ZrCl₂. The Ph₂Zn-metallocene-MAO systems homopolymerize styrene, p-methylstyrene and p-tert-butylstyrene, producing syndiotactic polymers in the case of the titanocenes and amorphous polymers in the case of the zirconocenes. The S/p-MeS and S/p-Bu^tS copolymers obtained with the Ph₂Zn-titanocene-MAO systems are enriched in the comonomer with respect to the initial feed.     

Adsorption of Bovine Serum Albumine Onto Poly (<Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">t</Emphasis>-Butylacrylamide-co-Acrylamide/Maleic Acid) Hydrogels

In the present study, a series of ionic poly(N-t-butylacrylamide-co-acrylamide) [P(NTBA-co-AAm)] hydrogels were synthesized by free-radical crosslinking copolymerization of N-t-butylacrylamide (NTBA) and acrylamide (AAm) monomers in fixed amount, but changing amount of maleic acid (MA) comonomer in methanol using N,N-methylene-bis-acrylamide (BAAm) as the crosslinker, ammonium persulfate (APS) as the initiator, and N,N,N′,N′-tetramethylethylenediamine (TEMED) as the activator. The swelling behavior of these hydrogels was analyzed in buffer solutions at various pHs. The prepared hydrogels also were investigated swelling-deswelling transition in water depending on the temperature. For the bovine serum albumin (BSA) adsorption, the effect of pH, temperature, initial protein concentration and adsorption rate were investigated. Maximum BSA adsorption was observed at pH 5.0 which is close to the isoelectric pH of BSA (pH 4.8). The highest adsorption rate was achieved in about 12 h. and also, maximum BSA adsorption was found at +5°C.     

Selective Hydrogenation of <Emphasis Type="Italic">trans</Emphasis>-Cinnamaldehyde over SiO<Subscript>2</Subscript>-Supported Co–Ir Bimetallic Catalysts

Selective hydrogenation of trans-cinnamaldehyde was studied on SiO₂-supported Co–Ir bimetallic catalysts. Addition of Ir to Co/SiO₂ increased the hydrogenation selectivity and activity of cinnamaldehyde to the corresponding cinnamyl alcohol (UOL). A selectivity as higher as 93% to UOL at ambient temperature under H₂ pressure of 2.0 MPa was obtained over catalyst with loadings of 10 wt% Co and 0.5 wt% Ir (Co_10.0Ir_0.5/SiO₂). The XRD, Raman and TPR results showed that the higher dispersed Co₃O₄ particles were formed on SiO₂ due to the addition of Ir, which increased the reducibility of Co₃O₄ to Co⁰. The reduction of oxidized Co–Ir/SiO₂ samples occurred at the temperatures with about 200 K lower than that of the one without Ir species as evidenced by the observations of TPR and in-situ Raman characterizations. The XPS results indicated that the large parts of Co₃O₄ in the sample of Co–Ir/SiO₂ were reduced to Co⁰, but only small parts of that were reduced to Co⁰ in the sample of Co/SiO₂ under flowing 5%H₂/Ar at 673 K. The CO chemisorptions revealed that the irreversible uptakes of CO on the reduced Co–Ir/SiO₂ sample was much higher than those on the reduced Co/SiO₂ and Ir/SiO₂, and also higher than the combination of that on the reduced Co/SiO₂ and Ir/SiO₂, respectively. The experimental data suggested that the presence of Ir played a key role in the reduction of Co₃O₄ to Co⁰ through a strong interaction between them and that the amount of Co⁰ at the catalyst surfaces was correlated to the activity and more importantly to the UOL selectivity.     

Highly selective and sensitive Th<Superscript>4+</Superscript>-PVC-based membrane sensor based on 2-(diphenylphosphorothioyl)-<Emphasis Type="Italic">N</Emphasis>′,<Emphasis Type="Italic">N</Emphasis>′-diphenylacetamide

A Th⁴⁺ ion-selective membrane sensor was fabricated from poly (vinyl chloride) (PVC) matrix membrane containing 2-(diphenylphosphorothioyl)-N′,N′-diphenyl acetamide (DPTD) as a neutral carrier, potassium tetrakis (p-chlorophenyl) borate (KTpClPB) as anionic excluder and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH and additive anionic influence on the response properties were investigated. The sensor, comprising 30% PVC, 63% solvent mediator, 4% ionophore and 3% anionic additive demonstrates the best potentiometric response characteristics. It displays Nernstian behavior (15.2 ± 0.5 mV per decade) over the concentration range 1.0 × 10⁻²–1.0 × 10⁻⁶ M. The detection limit of the electrode is 6.3 × 10⁻⁷ M (∼140 ng/ml). The response time of the electrode is 30 s .The sensor can be used in the pH range 3.0–9.0 for about 6 weeks. The membrane sensor was used as an indicator electrode in the potentiometric titration of Th⁴⁺ ions with EDTA. It was successfully applied to the determination of thorium ions in binary mixture.     

Oxygen permeability and structural stability of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>Co<Subscript>0.2</Subscript>Fe<Subscript>0.8</Subscript>O<Subscript>3−<Emphasis Type="Italic">δ</Emphasis></Subscript> membrane

La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature, but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen flux of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane exposed to flowing air (P _h =0.21 atm) and helium (P₁=0.037 atm) is ca. 0.33 ml/cm²·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La₂O₃ and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both surfaces of membrane irrespective of spreading of glass sealing material. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

A Novel Coordination Polymer with Helical Chain: Synthesis and Crystal Structure of [Cu<Subscript>4</Subscript>(PMEP-Sal)<Subscript>4</Subscript>·H<Subscript>2</Subscript>O]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

Summary A novel coordination polymer, [Cu₄(PMEP-sal)₄·H₂O] _n (PMEP-sal = 4-(2′-hydroxyl benxoylhydrazinyl) ethylidene-5-methyl-2-phenyl-pyrazole-3-one), is synthesized. Single crystal X-ray analysis reveals the polymer contains tetranuclear building blocks in helical arrangement.     

Physicochemical and Rheological Properties of Crystallized Blends Containing <Emphasis Type="Italic">trans</Emphasis>-free and Partially Hydrogenated Soybean Oil

Three vegetable oil blends, intended for formulation of high melting temperature confectionary coatings, were prepared by mixing different proportions of coconut oil, palm stearin, and either partially hydrogenated soybean oil (PH-SBO) or native soybean oil (i.e., trans-free SBO). The blends were crystallized under the same isothermal conditions and the crystallized systems evaluated by DSC, SFC, polarized light microscopy, and rheology under low [i.e., G′ and yield stress (σ*)] and high (i.e., creep and recovery profiles) stress forces. Overall, all trans-free blends showed lower SFC and heat of crystallization than the ones obtained with PH-SBO blends. These results showed that trans-fatty acids decrease the level of structural order of the crystals, and probably also the organization of the crystal network. As a result, most of the crystallized blends with PH-SBO showed lower σ* values and higher creep profiles (i.e., softer texture) than trans-free blends, particularly in systems crystallized at high supercooling and blends with saturated medium chain TAG. Nevertheless, at particular crystallization temperatures some trans-free formulations provided crystallized systems with rheological properties that would result in softer textures than the ones obtained with PH-SBO blends. Knowledge of the rheological properties under low and high stress forces is vital when comparing the functionality of crystallized TAG systems with and without TAG with trans-fatty acids.     

N<Subscript>2</Subscript>O fluxes and CO<Subscript>2</Subscript> exchange at different N doses under elevated CO<Subscript>2</Subscript> concentration in boreal agricultural mineral soil under <Emphasis Type="Italic">Phleum pratense</Emphasis>

The effects of elevated atmospheric CO₂ concentration on N₂O fluxes, instant CO₂ exchange and the biomass production of timothy (Phleum pratense) were studied in the laboratory. Three sets of 12 farmed sandy soil mesocosms sown with Phleum pratense were fertilised with a commercial fertiliser in order to add 5, 10 and 15 g N m⁻², and equally distributed in four thermo-controlled greenhouses. In two of the greenhouses, the CO₂ concentration was kept at atmospheric concentration (360 μmol mol⁻¹), and in the other two at double the ambient concentration (720 μmol mol⁻¹). Forage was harvested and the plants fertilised twice during the N₂O measurements. This was followed by an extra fertilisation and harvesting. After the third harvest, the growth of P. pratense was maintained at a height of 18 cm for measurements of instant CO₂ exchange, performed in two growth chambers. N₂O exchange was monitored using a closed chamber technique and a gas chromatograph. Instant CO₂ exchange was monitored using an infrared gas analyser. N₂O was emitted from the soil in the low, moderate and high N treatments at both CO₂ concentrations when the moisture content was low, the N₂O probably being mainly derived from nitrification. The highest flux (3303 μg N₂O m⁻² h⁻¹) occurred in the highest N treatment before thinning the stand of P. pratense under elevated CO₂ concentration. P. pratense was acclimated to the elevated CO₂ concentration: the NEE and P _G of the elevated growth of P. pratense decreased, in contrast to the fluxes of the normal ambient growth, when measured at the changed CO₂ concentration (ambient). The rate of respiration (R _TOT) in the agroecosystem did not increase due to the elevated CO₂ concentration, but instead the results indicated decreased R _TOT (on average 2049 and 1808 mg CO₂ m⁻² h⁻¹ at ambient and elevated CO₂ concentration, respectively) when there was an abundant N supply. This infers the possibility of enhanced C accumulation in agriculture mineral soil via P. pratense under an increased atmospheric CO₂ supply.     

Effect of <Emphasis Type="Italic">in situ</Emphasis> co-crosslinking on mechanical properties and rheology of nylon 11/EVOH/DCP composites

Nylon 11/ethylene-vinyl alcohol (EVOH) composites with various concentration of dicumyl peroxide (DCP) were prepared using a single-screw extruder. The influence of DCP concentration on the mechanical properties and rheological behavior of nylon 11/EVOH composites as well as gel content was investigated. The experimental results showed that the impact and tensile strength were significantly improved when the DCP loading was in the range of 1.0~1.5 wt% while the elongation at break reduced. All nylon 11/EVOH melts with and without DCP were pseudoplastic and exhibited shear-thinning behavior. The apparent viscosity of composites was increased dramatically with the addition of DCP and was up to the maximum value at 1.5 wt% DCP level, which indicated that the interfacial adhesion owe to co-crosslinking between nylon 11 and EVOH was increased markedly.     

Swelling behaviors and mechanical properties of polymer gel/poly(<Emphasis Type="Italic">N</Emphasis>-vinyl-2-pyrrolidone) complexes

The contraction of poly(acrylic acid-co-butyl methacrylate) (P(AA-co-BMA)) gel induced by complexation with linear Poly(N-vinyl-2-pyrrolidone) (PVP) is quite different from that of poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA) gel. The dynamic mechanic properties vary greatly between complexed and uncomplexed networks. It was found that the concentration of PVP has a strong effect on the complexation with P(AA-co-BMA) gel and the dynamic mechanic properties of the P(AA-co-BMA)/PVP complexes.