Selective catalytic reduction of nitric oxide over vanadia grafted on titania. Influence of vanadia loading on structural and catalytic properties of catalysts

The selective catalytic reduction (SCR) of NO by NH₃ has been studied over vanadia/ titania catalysts prepared by selective immobilization of vanadyl alkoxide species on two structurally different titania supports. The loading of vanadia was varied from 1.8 to 7.5 ,mol V⁵⁺ per m² surface area. Comparative kinetic measurements at 150 °C show that the NO turnover frequencies increase by more than an order of magnitude when the vanadia loading is increased from 1.8 to 3 mol V⁵⁺/m². In the region of lower SCR activity, i.e. at lower coverages ( 2 mol V⁵⁺/m²), small clusters and ribbons of vanadia are detected in the Raman spectra, whereas at loadings where maximum NO turnovers are achieved ( 3 mol V⁵⁺/m²) the prevalent vanadia species are well-developed two-dimensional vanadia layers bound to titania.     

Specific features of the phase transformations occurring during the sintering process of the beta-alumina based ceramics and their properties

Conclusions During the sintering process of beta-alumina obtained using the method of plasmochemical synthesis, the structural transformation occurs and it is accompanied by the separation of the excess Na₂O and the formation of an intergranular meltlike phase that is saturated with sodium and is characterized by high dielectric properties.The quantity of the meltlike phase and the magnitude of the /( + ) ratio determine the degree of stabilization (stability) and the final resistivity of the material and depend on the initial chemical composition and the heating rate maintained during the sintering process.It was shown that when the duration of residence of the material in the hot zone of the furnace is increased or when the specimens sintered maintaining high heating rates are subjected to additional heat treatment, one observes the occurrance of the reverse structural transformation that is characterized by an increase of the phase ratio /( + ) 1, a reduction in the quantity of the meltlike phase right up to its complete disappearance, and a decrease of the electrical resistivity of the material.In the materials having a large excess quantity of sodium oxide, the process of crystallization of the intergranular NaAlO₂ phase occurs simultaneously with the second phase transformation.The best ceramic and electrophysical parameters were obtained when sintering the material contained 7.9% Na₂O.Translated from Ogneupory, No. 3, pp. 13–18, March, 1990.     

Oriental fruit moth pheromone component emission rates measured after collection by glass-surface adsorption

We collected and quantified both synthetic and natural Oriental fruit moth [Grapholitha molesta (Busck)] sex pheromone components in 250-ml round-bottom flasks by hexane rinsing of compounds adsorbed on the glass walls. This simple procedure collected 100% of the pheromone evaporated inside the flask and was useful for quantifying both nanogram and microgram amounts of emitted pheromone. Emission rates of (Z)-8-dodecenyl acetate from 1000, 100, and 10 g-loaded rubber septa were 219, 12, and 1.2 ng/hr, respectively.G. molesta females emitted this component at 3.2 ng/hr, close to the emission rate from a 10 g-loaded septum, which evokes long-range and close-range behaviors in the male. The corresponding alcohol, (Z)-8-dodecenyl alcohol, was emitted from rubber septa ca. 3 times faster than the acetate.Lepidoptera: Tortricidae.Paper of the Michigan State Agricultural Experiment Station.     

Molybdenum nitride for the direct decomposition of NO

The physico-chemical properties of passivated -Mo₂N have been investigated. The material showed high activities for NO direct decomposition: nearly 100% NO conversion and 95% N₂ selectivity were achieved at 450C. The amount of O₂ taken up by -Mo₂N increased with temperature rise and reached 3133.9 molg^–1 at 450C; we conclude that there formation of Mo₂O_xN_y occurred. This oxygen-saturated -Mo₂N material was catalytically active: NO conversion and N₂ selectivity were 89 and 92% at 450C. We found that by means of H₂ reduction at 450C, Mo₂O_xN_y could be reduced back to -Mo₂N and the oxidation/reduction cycle is repeatable; such a behaviour and the high oxygen capacity (3133.9 molg^–1) of -Mo₂N suggest that -Mo₂N is a promising catalytic material for automobile exhaust purification.     

Caste-dependent pheromones in the head of the antTetramorium caespitum

The heads of maleT. caespitum contain 4-methyl-3-hexanol (1.7 g, only the erythro isomer(s) detected) and 4-methyl-3-hexanone (0.8 g). The heads of alate females contain 0.1 g of each compound, whereas only the alcohol (0.1 g) was found in the heads of workers. Both compounds act as attractants for the workers and their possible functions are discussed.'Chargé de Recherche du F.N.R.S.Chercheur qualifié du F.N.R.S.     

Novel and Ideal Zirconium-Based Dense Membrane Reactors for Partial Oxidation of Methane to Syngas

A novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo_0.4Fe_0.4Zr_0.2O_3– and the catalyst of LiLaNiO/-Al₂O₃. The POM reaction was performed successfully. Not only was a short induction period of 2 h obtained, but also a high catalytic performance of 96–98% CH₄ conversion, 98–99% CO selectivity and an oxygen permeation flux of 5.4–5.8 mlcm^–2min^–1 (1.9–2.0 molm^–2S^–1Pa^–1) at 850°C were achieved. Moreover, the reaction has been steadily carried out for more than 2200 h, and no interaction between the membrane material and the catalyst took place.     

Characterization of some organic poly(aminiumphosphate)s

Summary Metachromatic reactions of MB and AO are studied with poly(aminium phosphate)s. The main band() at 665 m and 492 m for MB and AO are shifted to 580 m and 455 m respectively (-bands). The metachromatic values at different concentrations of poly(aminium phosphate)s are also reported. The dye association for MB with these polymer derivatives is investigated conductometrically as well. It is observed that MB can be at the most bind with the phosphate residue of polymer upto 11 molar ratio. The polymeric nature was further established by paper chromatographic technique in Terry's, Ebel's & Pfrengle's solvents.     

Performance and impedance studies of thin,porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter

Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optinum performance as AMTEC electrodes at thicknesses less than 1.0 m when used with molybdenum or nickel current collector grids. Power densities of 0.40 W cm^–2 for 0.5 m molybdenum films at 1200 K and 0.35 W cm^–2 for 0.5 m tungsten films at 1180 K were obtained at electrode maturity after 40–90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3–0.4 m. The a.c. impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness <2.0 m, is not utilized efficiently unless a fairly fine (1×1mm) current collector grid is employed.     

Defensive secretions of three species ofAcilius (Coleoptera: Dytiscidae) and their seasonal variations as determined by high-pressure liquid chromatography

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of defensive secretions obtained from the pygidial and prothoracic glands of dytiscids. Methods were developed for both normal phase (Porasil) and reverse phase (Bondapak C₁₈) columns. The applicability of this technique was demonstrated when defensive compounds ofAcilius semiculcatus, A. sylvanus andA. mediatus were isolated, identified, and quantitated. No major differences were found in the composition of the defensive secretions between the three species. The seasonal defensive titer ofA. semisulcatus was determined from June through October 1977. The pygidial defensive agents (benzoic acid,p-hydroxybenzaldehyde, and methylp-hydroxybenzoate varied from 9.0 to 67.8 g and exhibited a maximum in July, and a steroid from the prothoracic gland varied from 7.1 to 33.2 g and was maximum in October.     

A Technology for Preparing Sintered Ceramics Based on Bauxite HCBS

A technology for preparing high-density (with zero open porosity) ceramics molded by casting from bauxite highly concentrated ceramic binding suspensions (HCBS) has been developed (90% Al₂O₃). The precursor HCBS feature a high dispersity (percentage of particles < 2 m across in excess of 40%; median particle diameter, < 5 m; d _max = 10 – 20 m), a high solid-phase concentration (C _V 0.65), and a high fluidity. A material with zero open porosity is obtained by sintering at 1400 – 1450°C and its potential use for making grinding bodies is considered.     

Linamarin and histamine in the defense of adultZygaena filipendulae

We determined the protective values of histamine and linamarin to an aposematic moth,Zygaena filipendulae. Using ion-exchange resin techniques, we found that the mean histamine concentrations in the wings were 0.061 ± 0.047 g/mg and 0.013 ± 0.0051 in the moths' bodies (totals: 0.586 g and 2.921 g, respectively, all wet weights). Average HCN evolution (mainly from the bitter cyanogen linamarin) from the wings was 0.049 ± 0.41 g/mg (0.426 g/ml of linamarin could produce this amount of HCN) and 0.029 ± 0.0026 g/mg HCN (0.281 g/mg linamarin) evolved from the bodies (total linamarin 4.09 g and 61.258 g, respectively, all wet weights). Therefore, higher concentrations of toxicants were found in the part of the body most liable to initial attack. We found, in offering various toxic solutions to 10 common quails, that 0.1% linamarin (mean linamarin consumed equal to about 70% of the average total wing content) but 1.0% histamine (mean histamine consumed equal to that found in about 8.9 average wing sets) solutions significantly lowered drinking rates. However, combination solutions were still effectively aversive at 0.001% histamine plus 0.028% linamarin. This synergism would allow a moth under local abiotic or dietary stress to elaborate substantially less of one or both compounds than that normally synthesized. The implications to kin selection are discussed.     

Effect of the crystalline from of Al2O3 on the interaction and sintering of large-crystal quartzite and disperse alumina

It is established that the amount of mullite and the value of the open porosity of specimens increase in the sequence -Al₂O₃(+)-Al₂O₃-Al₂O₃Al₂O₃ · 3H₂O. The apparent density and the ultimate compressive strength increase in the reverse direction. Active modifications of alumina (hydrargillite, -Al₂O₃) stimulate mullite formation, which is accompanied by an increase in the open porosity to 40% and a decrease of the mechanical strength to 8–12.5 MPa, and high (up to 12%) linear shrinkage. High-quality, dense, strong refractories can be produced in a single firing from coarse-grained quartzite and finely disperse corundum and alumina in the form of -Al₂O₃.Translated from Ogneupory, No. 10, pp. 18 – 20, October, 1994.Eastern Institute of Refractories.     

Interrelation between the Glass Transition Temperature, Thermal Expansion Coefficient, and Poisson Ratio for Some Glasses in the AV–BVI–CVIISystems

In the framework of the free volume concept, the dependences of _g T _gand T _gon and are considered and the interrelation between the fraction of the fluctuation free volume f _g, Poisson ratio , and Grüneisen lattice parameter for chalcogenide, oxogenide, and oxohalide glasses is discussed. The fluctuation free volume model and the model of soft atomic configurations are compared in terms of anharmonicity of the glasses under investigation.     

Determination of electronic conductivity limits of mullite and ZrO2-9 mol% MgO solid electrolytes

A coulometric titration technique was used for the determination of the parameterP , defined as the oxygen partial pressure at which the ionic conductivity and n-type electronic conductivity of the electrolyte are equal, for mullite and 9 mol% MgO stabilized zirconia electrolytes in the temperature range 1674–1921 K. The results ofP for mullite and ZrO₂-9 mol% MgO were log(P /101 325 Pa)=54.32–137000/T and log (P /101 325 Pa)=27.16–75500/T, respectively. The results for low oxygen activities in liquid iron are discussed on the basis of the present results forP values.     

Leaf surface chemicals fromNicotiana affecting germination ofPeronospora tabacina (adam) sporangia

A bioassay was used to evaluate the effects of cuticular leaf components, isolated fromN. tabacum, N. glutinosa (accessions 24 and 24a), and 23other Nicotiana species, on germinationof P. tabacina (blue mold). The leaf surface compounds included- and-4,8,13,-duvatriene-l,3-diols (DVT-diols), (13-E)-labda-13-ene-8-,15-diol (labdenediol), (12-Z)-labda-12,14-diene-8-ol (cis-abienol), (13-R)-labda-8,14-diene-13-ol (manool), 2-hydroxymanool, a mixture of (13-R)-labda-14-ene-8,13-diol (sclareol), and (13-S)-labda-14-ene-8,13-diol (episclareol), and various glucose and/or sucrose ester isolates. The above in acetone were applied onto leaf disks of the blue moldsusceptibleN. tabacum cv. TI 1406, which was then inoculated with blue mold sporangia. Estimated IC₅₀ values (inhibitory concentration) were 3.0g/cm² for-DVT-diol, 2.9/cm² for-DVT-diol, 0.4g/cm² for labdenediol and 4.7g/cm² for the sclareol mixture. Manool, 2-hydroxymanool, andcis-abienol at application rates up to 30g/cm² had little or no effect on sporangium germination. Glucose and/or sucrose ester isolates from the cuticular leaf extracts of 23Nicotiana species and three different fractions fromN. bigelovii were also evaluated for antimicrobial activity at a concentration of 30g/cm². Germination was inhibited by >20% when exposed to sugar esters isolated fromN. acuminata, N. benthamiana, N. attenuata, N. clevelandii, andN. miersii, and accessions 10 and 12 ofN. bigelovii. These results imply that a number of compounds may influence resistance to blue mold in tobacco.     

Pore Structure and Permeability of an Alumina Fiber Filter Membrane for Hot Gas Filtration

The pore structure and permeability of an alumina-fiber-based hot gas filter membrane containing an acid phosphate binder were characterized using capillary flow porometry. The smallest pore diameter was 1.24 ± 0.06 m; the largest pore diameter (bubble point pore diameter) was 23 ± 1 m. The pore size distribution was narrow, with almost all pores ranging from 2 to 4 m, and the mean flow pore size 2.6 ± 0.1 m. The Darcy permeability constant for air through the membrane was (114 ± 6) × 10^–9 cm².     

Grinding kinetics of calcined alumina

Conclusions If it is necessary to obtain a mineral powder with a high dispersion (_mean 1 ), it is technically-undesirable and economically unsuitable to increase the quantity of grinding bodies by more than four times with respect to the weight of -Al₂O₃.Silicone oil is a suitable surface active agent for carrying out effective dry grinding of -Al₂O₃.With the dry grinding of -Al₂O₃ using metal grinding bodies, the iron pickup is approximately ten times greater than with wet grinding. During the dry grinding of -Al₂O₃ with an addition of silicone oil, and corundum grinding bodies, the rate of grinding is the same as with wet grinding using metal grinding bodies.Translated from Ogneupory, No. 8, pp. 71–72, August, 1971.     

Synergism of Polygodial and trans-Cinnamic Acid on Inhibition of Root Elongation in Lettuce Seedling Growth Bioassays

A bicyclic sesquiterpene dialdehyde, polygodial did not inhibit root elongation up to a concentration of 12.5 g/ml in a lettuce seedling assay: trans-Cinnamic acid inhibited the elongation by 50% at 1.2 g/ml (8.1 M). The inhibitory activity of trans-cinnamic acid was enhanced 17-fold when used in combination with 6.25 g/ml (26.5 M) of polygodial. A decrease in the pH of the medium was observed during normal seedling growth, indicating transport of protons from the cells by a plasma membrane H⁺-ATPase. The inhibitory effect of trans-cinnamic acid on the elongation was reduced to some extent in 2 mM phosphate buffer (pH 7.0) during seedling growth. Although polygodial did not inhibit the activity of H⁺-ATPase in the plasma membrane fraction of roots in normally growing seedlings, a decrease in activity was found in the fraction obtained from seedlings incubated with 20 g/ml of polygodial. These results suggest that polygodial functions synergistically with trans-cinnamic acid in the inhibition of root elongation via restriction of proton transport from the cytoplasm of germinated cells.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.     

Studies concerning charged nickel hydroxide electrodes. II. Thermodynamic considerations of the reversible potentials

In this paper the thermodynamics of mixing are applied to account for the independence of the discharge potential of the nickel hydroxide electrode as a function of nickel oxidation state. The constant potential region is considered to arise from the formation of a pair of co-existing solid solutions having a composition predetermined by the magnitude of the interactions between the oxidized and reduced species. From considerations of the excess-energy terms, it can be shown for a symmetrical potential/ composition profile, that the constant potential region is identical with the standard potentialE ₀. The influence of asymmetry on the changes inE ₀ are discussed. Consideration has also been made of the influence of dissociation of oxidized and/or reduced species on the potential determining equations. The removal of n-type defects from the nickel(II)-rich phase on discharge is considered to be responsible for the observed secondary discharge plateau at potentials 300 mV more cathodic than normal. This non-equilibrium behaviour can be explained in terms of a mixed pn-semiconducting material.List of symbols E electrode potential at constant pH(V) - E ₀ standard electrode potential (V) - R the gas constant (J K^–1 mole^–1) - F the Faraday constant (C g-equiv^–1) - T the absolute temperature (K) - ^aH⁺ proton activity in the electrolyte - a _z activity of oxidized species z - a _y activity of reduced species y - _H+ chemical potential of the proton - _e chemical potential of the electron - _z ^o standard chemical potential of species z - _z chemical potential of species z - _y ^o standard chemical potential of species y - _y chemical potential of species y - _H,e chemical potential of the proton/electron pair - x _y orx mole fraction of reduced species y - x _z mole fraction of oxidized species z - G _M total free energy of mixing (J mole^–1) - G _R free energy of reaction (J mole^–1) - G _I free energy of mixing under ideality (J mole^–1) - G _E excess free energy (J mole^–1) - A,A _i andB _i interaction energy parameters (J mole^–1) - x _u mole fraction of y in co-existing phase u - x _v mole fraction of y in co-existing phase v - _y activity coefficient of undissociated reduced species y - _z activity coefficient of undissociated oxidized species z - _y ^± mean ionic activity coefficient of y - _z ^± mean ionic activity coefficient of z - _y activity coefficient of y in phase u - _z ^u activity coefficient of z in phase u - _y ^v activity coefficient of y in phase v - _z ^v activity coefficient of z in phase v - I current (A) - S cross-sectional area (cm²) - L conductor length (cm)