Higher Degree Of Reduction Research Articles

New materials technologies for hydrogen generation

A thermochemical cycle is described that demonstrates the use of biomass or lignite-derived synthesis gas to reduce New Zealand ironsand, which is subsequently steam-oxidised to generate pure hydrogen. The redox reactions for this cycle have been thermodynamically modelled, giving an indication of the temperature ranges required to achieve water splitting and the potential sensitivity of the process to partial pressures of CO2. A fixed bed reactor showed reproducible oxide reduction behaviour over 10 redox cycles but only achieved limited conversion to 64% residual Fe3O4 (18%Fe). Fluidised bed reactor studies carried over a comparable timeframe using CO/N2 mixtures demonstrated a high degree of reduction to 76%Fe.

Spatially resolved UV–vis microspectroscopy on the preparation of alumina-supported Co Fischer–Tropsch catalysts: Linking activity to Co distribution and speciation

The preparation steps of Co/ γ-Al 2O 3 Fischer–Tropsch (FT) catalysts have been studied using spatially resolved UV–vis microspectroscopy. The speciation of the different Co phases inside the support bodies changed by varying the composition of the impregnation solutions and the applied treatment, that is, subsequent impregnation, aging, drying, and calcination. The activity in the FT synthesis reaction of the reduced catalysts has been correlated with the applied preparation procedure. The highest activity was observed when γ-Al 2O 3 was impregnated with an aqueous CoCO 3 solution containing 1 equivalent citric acid. The formation of a Co citrate complex inside the support after impregnation was favored due to the higher pH of this solution compared with a similar solution involving Co(NO 3) 2. After calcination, Co 3O 4 was observed with an eggshell distribution, and no unfavorable CoAl 2O 4 was observed. The Co citrate complex formation is thought to restrict the extent of interaction of Co with alumina to form CoAl 2O 4, thereby allowing a higher degree of reduction and a concomitant higher catalytic activity. This study demonstrates the power of monitoring catalyst preparation with spatially resolved UV–vis microspectroscopy. The understanding of the physicochemical processes occurring at the different stages of the preparation process allows fine-tuning of the catalyst properties, which is ultimately expected to enable the development of improved supported catalysts.

Reduction of the RACM scheme using Computational Singular Perturbation Analysis

The modeling of dispersion of reacting pollutants in the atmosphere requires proper description of both the chemistry involved and the transport of pollutants. We present here highly reduced chemical schemes for rural and urban dispersion problems based on the Computational Singular Perturbation (CSP) technique. CSP identifies the steady‐state species for removal, by resolving the “fast” and the “slow” chemistry components. Here, the CSP method is employed for the reduction of the Regional Atmospheric Chemistry Mechanism (RACM), which includes 77 species and 237 reactions. Three cases were tested: (1) a polluted scenario including ground emissions, (2) a relatively cleaner environment with 10% of the emission levels of case 1, and finally (3) rural conditions without any emissions, for which the effects of emissions on the reduction procedure were directly studied. It was found that reduced mechanisms with high degree of reduction, down to a 16 step mechanism, i.e., 56 species in steady state, produced excellent results for most species for all cases. These reduced mechanisms did not change much between urban or rural conditions and the inclusion of emissions did not affect significantly the selection of major species. This indicates the persistence of a well‐defined fast subset of the mechanism, suggesting that the produced reduced mechanisms are valid for a wide range of conditions in the atmosphere.

Development of a dosing strategy for a heavy-duty diesel exhaust cleaning system based on NOX storage and reduction technology by Design of Experiments

A dosing strategy for the transient control of an exhaust after-treatment system using the NOX storage and reduction approach was developed on a heavy-duty diesel engine rig equipped with an 11l diesel engine. The catalysts were oxidation catalysts of 8.4l and NOX storage and reduction catalysts of 16.8l total volume. The dosing strategy has been tested in a European Transient Cycle (ETC) resulting in a NOX reduction of 60% (by 4.5g/kWh) with a fuel penalty of 6.6% when the catalysts were preconditioned to 450°C. The reducing agent was diesel fuel. To keep the fuel penalty low, a bypass system was used which bypassed approximately 90% of the exhaust flow under the regeneration periods. The parameters for the dosing strategy were obtained from steady-state optimization experiments (constant speed and torque) using Design of Experiments (DoE) to obtain much information from few experiments. The system was optimized for a high degree of NOX reduction with a low fuel penalty. The period when the flow through the catalyst is reduced (bypass time), the cycle time, the injection time and rate are important parameters to achieve an improved NOX reduction. The optimal values of these parameters varied with the load points used. The steady-state NOX conversion was approximately 60% (3.3–4.1g/kWh) at catalyst temperatures between 330 and 530°C. The most promising parameters for a large NOX reduction and a low fuel penalty have been applied in the dosing strategy and tested in an ETC.

The surface modification effects of silica support by organic solvents for Fischer–Tropsch synthesis catalysts

The surface of silica support was pretreated by various organic solvents before the impregnation of cobalt precursor. The catalysts prepared from pretreated supports exhibited highly catalytic activity, due to high dispersion and high reduction degree of the supported cobalt. Co/SiO 2 catalyst pretreated by acetic acid showed the highest CO conversion and the lowest CH 4 selectivity. The pretreatment by organic solvent modified the surface properties of silica support, realizing the high dispersion and the increased reduction degree of supported cobalt simultaneously. The properties of various catalysts were characterized by XRD, TPR and H 2 chemisorption.

Wound dressings containing bFGF-impregnated microspheres

The primary objective was to synthesize a novel wound dressing containing basic fibroblast growth factor (bFGF)-loaded microspheres for promoting healing and tissue regeneration. Gelatin sponge was chosen as the underlying layer and elastomeric polyurethane membranes were used as the external layer. To achieve prolonged release, bFGF addition was loaded in microspheres. The microspheres were characterized for particle size, in vitro protein release and bioactivity. The bilayer dressings were tested in in vivo experiments on full-thickness skin defects created on pigs. Average size of the microspheres was 14.36 ± 3.56 µm and the network sponges were characterized with an average pore size of 80–160 µm. Both the in vitro release efficiency and the protein bioactivity revealed that bFGF was released in a controlled manner and it was biologically active as assessed by its ability to induce the proliferation of fibroblasts. It was observed that sustained release of bFGF provided a higher degree of reduction in the wound areas. Histological investigations showed that the dressings were biocompatible and did not cause any mononuclear cell infiltration or foreign body reaction. The structure of the newly formed dermis was almost the same as that of the normal skin. The application of these novel bilayer wound dressings provided an optimum healing milieu for the proliferating cells and regenerating tissues in pig's skin defect models.

Hydroformylation of 1-hexene for oxygenate fuels via promoted cobalt/active carbon catalysts at low-pressure

The hydroformylation of 1-hexene was catalyzed with active carbon-supported cobalt catalysts under the low syngas pressure. Small amount of Pt, Pd and Ru, added as promoters in Co/AC, led to a great improvement of catalytic activity for hydroformylation of 1-hexene. The promotional effect of Ru for Co/AC catalyst was the best in this study as the highest activity and selectivity for oxygenate formation. Meanwhile, the activity of 1-hexene hydroformylation increased with increasing Ru loading. Ru added was bulk-rich in the active carbon supported cobalt particles, showing very low surface Ru density. This kind of unbalanced alloy formation determined the highest performance of Ru added Co/AC catalyst, via small particles but high reduction degree, keeping more CO in non-dissociative state and lowering surface hydrogen pressure.

Morphological consequences of range fragmentation and population decline on the endangered Iberian lynx (Lynx pardinus)

AbstractThe Iberian lynx Lynx pardinus is one of the world's most endangered felids and is vulnerable to human‐induced mortality and habitat loss, which reduce population size and accelerate the loss of genetic variation. Twenty‐five metric traits of Iberian lynx skulls have been measured on 95 skulls collected between 1872 and 2003. The skulls belong to three geographically distinct areas/populations, which have recently diverged from each other as a consequence of increased habitat fragmentation: Doñana area, Sierra Morena mountains and Montes de Toledo area. The morphometric study was undertaken using univariate, multivariate and admixture analysis approaches, and all three techniques provided evidence for morphometric differentiation, both in skull size and shape, among the three populations for both males and females. Environmental and genetic forces that may have shaped these patterns are discussed. The males of the population of the Doñana area showed a different degree of reduction in size in nine of the skull traits with time, which has been suggested to be partly because of worsened habitat conditions. However, the heterogeneity of the degree of mean size reduction and the relatively high degree of reduction of some of the skull traits investigated (>4%), which have altered the original proportions between the skull variables, could also partly be attributed to inbreeding depression in the Doñana population. The phenotypic variability of the skull traits showed significant increases (two traits) or decreases (nine traits) with time, and this different pattern of change with time has been suggested to be because of a different number of genes controlling the traits with different degrees of dominance and epistatic interactions. The increased phenotypic variability of two of the traits has also been attributed to a possible decreased level of developmental stability, which can be produced by environmental and/or genetic stress. The findings of this investigation contribute to the discussion about the utility and the limits of quantitative genetics techniques for conservation purposes.

Cold rolling behaviour and textural evolution in AISI 316L austenitic stainless steel

The present paper deals with the evolution of microstructure and texture of a 316L austenitic stainless steel during cold rolling. With increasing rolling reductions, different deformation mechanisms become active. TEM observations show the presence of deformation twinning. With increasing strain the volume fraction of twin increases. At higher degrees of reduction, there is evidence that flow localization takes place and there is formation of shear bands. The material initially shows Cu-type texture, i.e., Cu {1 1 2}〈1 1 1〉, Bs {1 1 0}〈1 1 2〉 with a spread towards Goss {0 1 1}〈1 0 0〉. With the progress of rolling, the Cu {1 1 2}〈1 1 1〉 component diminishes and the other two components increase their intensity during rolling. At higher strain levels, there are additional texture components, {1 1 1}〈 u v w〉. The evolution of texture is correlated with the associated deformation mechanisms.

Final stage of reduction of iron ores by hydrogen

A high degree of reduction or metallization of products, such as hot briquetted iron (HBI), used in steelmaking is desirable. For many ores it is difficult to achieve this goal because the rate of reduction slows significantly after 70–90% reduction. The present study shows that this happens for several types of ores and oxides because a shell of dense iron forms around wustite grains requiring atomic diffusion of oxygen through iron, for reduction to proceed. This rate is slow because of the low driving force and diffusion coefficient. Examination of the rate equations for gaseous reduction and oxygen diffusion indicate that if the wustite grains are about 1 μm, gaseous reduction will govern the rate up to 95% reduction or greater, but for 2‐μm‐sized grains the rate will slow significantly earlier when atomic diffusion controls the rate. The present work also indicates that if the equilibrium gas pressure at the Fe/FeO exceeds 1 atm, the iron shell may fracture allowing for faster gaseous reduction. Also, annealing or holding the ore at magnetite (Fe3O4) can also cause the rate of reduction to slow at lower degrees of reduction.

Improvement of Sinter Softening Property and Reducibility by Controlling Chemical Compositions

Increasing permeability of packed materials in a blast furnace and decreasing reducing agent rate at a blast furnace process take an important role to improve productivity. In order to increase permeability and decrease reducing agent rate, sinter softening property during reduction and sinter reducibility are important.Effects of sinter compositions (CaO, SiO2, Al2O3, MgO, FeO) on the sinter softening property during reduction and sinter reducibility were examined by samples produced from pot scale sintering. These compositions were controlled by lime stone, serpentine, and coke breeze content and varying iron ore source in raw sinter materials. And sinter softening property was estimated by vertical pressure drop of sinter packed bed (70 mmφ×100 mm) during sinter reduction with raising temperature to 1 600°C under vertical loading force (9.8×104 N/m2). This pressure drop is caused by melt formation from slag compositions in sinter above 1 000°C. And sinter reducibility was estimated as reduction degree by CO(30%)-N2 gas under constant temperature conditions (900°C, 1 100°C).Results were obtained as follows.(1) Low SiO2 and low CaO sinter had superiority of sinter softening property. That is small pressure drop caused by decreasing SiO2-CaO-FeO melt.(2) And low SiO2 and low CaO sinter had high reducibility at both 900°C and 1 100°C. It is considered that decrease of these compositions affects restriction of calcium silicate containing ferrous oxides.(3) High MgO and high FeO sinter using dolomite instead of serpentine and blended with high coke breeze also had superiority of sinter softening property. Adding MgO to phase of CaO-FeO-SiO2 raises melting temperature. The raising melting temperature is considered to make high pressure drop region to be narrow.(4) And high MgO and high FeO sinter had low reduction degree at 900°C but kept high reduction degree at 1 100°C. X-ray diffraction pattern for the sinter indicated that it contained much magnetite structure (magnetite and magnesioferrite) instead of hematite. This mineral composition is consistent with low reduction degree at 900°C. On the other hand, keeping high reduction degree at 1 100°C is considered to correspond not to promote silicate (FeO-2SiO2, FeO-SiO2-CaO) formation. By X-ray micro analyzer, it was found that calcium ferrite contained more Si and more Mg ion with increasing MgO in sinter. Increasing Si ion in calcium ferrite is considered to be the cause of restricting silicate formation.(5) Al2O3 content has little effect to sinter softening property.Summarized these results, low SiO2, low CaO, high MgO and high FeO sinter has a good softening property and high reducibility. These characteristics indicate good performance as raw material in a blast furnace.

Adsorption of CO and C 2H 4 on Rh-loaded thin-film praseodymium oxide

A praseodymium oxide thin-film was deposited on Ru(0 0 0 1) by vapor depositing Pr in 2 × 10 −7 Torr O 2 while the Ru was at 700 K. The film was approximately 5 nm thick and did not produce a LEED pattern. The adsorption and reaction of CO and C 2H 4 adsorbed on Rh supported on the PrO X film were studied by TPD and SXPS. The CO initially reacted with oxygen in the substrate to produce CO 2. After this oxygen was removed, the CO adsorbed non-dissociatively in a manner similar to what is seen on Rh(1 1 1). C 2H 4 adsorbed on the Rh particles and underwent progressive dehydrogenation to produce H 2 during TPD. The C from the C 2H 4 reacted with the O in PrO X to produce CO. CO dissociation on the Rh particles could be promoted by reducing the PrO X with C 2H 4 before CO exposure. The CO dissociation occurred over a narrow range of Pr reduction and occurred only at high degrees of reduction. No CO dissociation was seen for films with a Pr 3+ content of up to 50%. Extensive treatment in C 2H 4 poisoned subsequent CO adsorption due to the build-up of C on the Rh particles.

Iterative schedule optimization for voltage scalable distributed embedded systems

We present an iterative schedule optimization for multirate system specifications, mapped onto heterogeneous distributed architectures containing dynamic voltage scalable processing elements (DVS-PEs). To achieve a high degree of energy reduction, we formulate a generalized DVS problem, taking into account the power variations among the executing tasks. An efficient heuristic is presented that identifies optimized supply voltages by not only "simply" exploiting slack time, but under the additional consideration of the power profiles. Thereby, this algorithm minimizes the energy dissipation of heterogeneous architectures, including power-managed processing elements, effectively. Further, we address the simultaneous schedule optimization toward timing behavior and DVS utilization by integrating the proposed DVS heuristic into a genetic list scheduling approach. We investigate and analyze the possible energy reduction at both steps of the co-synthesis (voltage scaling and scheduling), including the power variations effects. Extensive experiments indicate that the presented work produces solutions with high quality.

Continuous lean NOx reduction with hydrocarbons over dual pore system catalysts

In order to reduce CO2 emissions there is a trend towards an increased use of more fuel-efficient lean burn combustion engines and thus an increased need for deNOx catalysts for such engines. In this study a mechanical mixture of CoFER and HZSM-5 zeolites was studied as a dual pore system catalyst for the continuous lean reduction of NOx with isobutane as reducing agent. The degree of NOx conversion was found to be strongly dependent on the oxygen concentration in the gas mixture, and the highest degree of reduction was achieved with 10% O2. This optimum is explained by the need for NO2 as an intermediate for the catalyst to work efficiently, and that above a certain oxygen concentration O2 oxidises the hydrocarbon resulting in a lower reduction potential for NOx. At an operating temperature of 350°C the conversion of NOx to N2 was 52% under steady-state conditions, but the efficiency can be improved further by optimisation of the oxidising zeolite and of the mixing ratio of the two zeolites.

Phosphorus removal with membrane filtration for surface water treatment

Surface water such as aquifers, recreational waters and rivers are often loaded by inflows with low quality, so that drinking water production, swimming or ground water charging must be restricted. To ensure the long-term use it is necessary to treat the influents or the water used for ground water charging. The current treatment process for phosphorus and turbidity removal is a combination of precipitation/coagulation, flocculation, sedimentation and sand filtration. By using this conventional method it is possible to reduce the dissolved ortho-phosphate and the turbidity (particulate phosphorus) as well as the amounts of algae and pathogenic organisms to very low concentrations. The high degree of reduction in this process is only achieved by a relatively high dosage of coagulants and flocculants. Such a process has been used for nearly 20 years by the Berliner Wasserbetriebe. In this study a comparison will be made between this process, which represents the state-of-the-art, and the combination of precipitation/coagulation with dead-end membrane filtration (micro-/ultrafiltration) concerning water quality and costs. The results show that it is possible to reach similar levels of phosphorus removal as with floc filtration. However, floc filtration requires significantly higher amounts of chemicals (coagulants and flocculants). No flocculants are used for membrane filtration. But the estimated costs for the membrane based process are at 0.17 €/m3 probably a little more expensive. However, the excellent permeate quality is much better at the values of suspended solids and micro-biological organisms.

Chromatographic and electromigration analysis of rhenium compounds used in radiopharmacy

A large group of radiopharmaceuticals includes complex radionuclide-ligand compounds which are very sensitive to the preparation conditions, as for example pH of reaction mixture, incubation time, temperature, molar ratio of reagents, etc. It is necessary to find the optimum condition for the formation of the radionuclide-ligand complex and to select the convenient analytical methods to determine the purity of the product. The preparation of radiopharmaceuticals labeled by rhenium-186 or rhenium-188 requires the addition of a reducing agent (commonly stannous chloride) to the reaction mixture in order to reduce perrhenate to a lower oxidation state which is capable of complex formation. For rhenium concentration up to approximately 10-5 mol/l, the molar excess of reduction agent over perrhenate is usually higher than 800 to reach the optimum yield of reduction and complexation (between 80-95%). Because of the potentially toxic effect of SnCl2 the reduction of perrhenate by stannous chloride was studied in detail to find the way for decreasing the concentration of reducing agent in the reaction mixture without significant lowering of the yield of perrhenate reduction. The reduction of perrhenate was determined by electromigration methods, i.e., capillary electrophoresis (CZE) and isotachophoresis (ITP), and thin-layer chromatography (TLC) with radiometric detection. The highest degree of reduction of perrhenate was obtained at pH 2 at perrhenate concentration ranging from 10-4 to 10-3 mol/l. The stability of reduced rhenium against a pH change from 2 to 5.5 (which corresponds to the pH close to physiological values) was tested as well. The influence of the presence of ascorbic acid as an antioxidant in the reaction mixture on the stability of the preparation against the pH change was determined. The stability of reduced rhenium against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy was also found out. The data acquired by capillary electrophoresis, isotachophoresis and thin-layer chromatography are comparable. Results obtained in these experiments were applied for the study of rhenium complexes with hydroxyethylidenediphosphonic acid (HEDP).

Flame-made nanocrystalline ceria/zirconia: structural properties and dynamic oxygen exchange capacity

Ceria/zirconia nanocrystals were prepared by flame-spray synthesis. Application of carboxylic acid-derived solvents allowed the continuous production of homogeneous mixed oxides with narrow particle-size distribution. The high preparation temperature favored the formation of a highly crystalline solid solution of the constituents. Structural and textural properties of the ceria-zirconia nanoparticles were characterized by high-resolution electron microscopy, nitrogen adsorption, and X-ray diffraction. The redox properties of the nanoparticles were investigated by temperature-programmed reduction and by dynamic oxygen exchange capacity (OEC) measurements using H 2, CO, and propene as reductants. For CO and H 2 a similar reduction was found, whereas propene afforded a considerably higher degree of reduction. While the flame-made powders had very stable specific surface area (up to 80 m 2/g) even after severe calcination (2 h at 900 °C in air) their OEC was lower than in corresponding ceria-zirconia prepared by coprecipitation. This difference is traced to the high crystallinity and low defect concentration of the flame-made material.

Context-based adaptive binary arithmetic coding in the H.264/AVC video compression standard

Context-based adaptive binary arithmetic coding (CABAC) as a normative part of the new ITU-T/ISO/IEC standard H.264/AVC for video compression is presented. By combining an adaptive binary arithmetic coding technique with context modeling, a high degree of adaptation and redundancy reduction is achieved. The CABAC framework also includes a novel low-complexity method for binary arithmetic coding and probability estimation that is well suited for efficient hardware and software implementations. CABAC significantly outperforms the baseline entropy coding method of H.264/AVC for the typical area of envisaged target applications. For a set of test sequences representing typical material used in broadcast applications and for a range of acceptable video quality of about 30 to 38 dB, average bit-rate savings of 9%-14% are achieved.

New CMS-associated phenotypes in cybrids Nicotiana tabacum L. (+Hyoscyamus niger L.).

Morphological characteristics were studied in cytoplasmic male sterile (CMS) cybrids possessing the tobacco nuclear genome, Hyoscyamus niger plastome and recombinant mitochondria. After backcrosses with tobacco, new flower modifications were found, including: conversions of stamens into branched filamentous structures; alterations in the shape of petals and the corolla limb; and high degrees of reduction in most flower organs. Vegetative alterations (leaf elongation and stem branching) occurred in some cybrids. Results confirmed that a protoplast fusion-based alloplasmic cytoplasm transfer, followed by conventional backcrosses, is a useful tool for generating alternative CMS sources with novel nucleo-cytoplasmic compositions. These alterations in the genetic status were accompanied by modified floral and vegetative phenotypes.

Synthesis and Characterization of Mesoporous Alumina as a Catalyst Support for Hydrodechlorination of 1,2-Dichloropropane: Effect of Catalyst Preparation Method

A mesoporous alumina was synthesized by a posthydrolysis method. The prepared mesoporous alumina was found to have randomly ordered pores, and retained relatively high surface area with narrow pore size distribution centered at ca. 4 nm. Nickel precursors were then supported on the mesoporous alumina by an impregnation (Ni-IMP) and vapor deposition (Ni-VD) method. Several characterizations were carried out in order to investigate physical and chemical properties of mesoporous alumina and supported Ni catalysts. TPR, XPS, and UV-DRS measurements revealed that the Ni-IMP catalyst retained much more amounts of surface nickel aluminate-like species than the Ni-VD sample. TPD experiments also showed that nickel aluminate species affected the adsorption amounts of reactant (1,2-dichloropropane). In the hydrodechlorination of 1,2-dichloropropane (DCPA), DCPA conversion over the Ni-VD catalyst was about two times higher than that over the Ni-IMP catalyst at 300 °C. It is probably due to the fact that the Ni-VD catalyst, which had low contents of nickel aluminate species compared to the Ni-IMP catalyst, exhibited higher degree of reduction than the Ni-IMP catalyst at pretreatment conditions. The difference in DCPA conversion between two catalysts was closely related to the degree of reduction of nickel species and the amounts of adsorption of DCPA onto the catalyst as well.