Carbon dioxide reforming of methane over Ni/Al2O3 treated with glow discharge plasma

Ni/Al₂O₃ catalyst was first treated by argon glow discharge plasma followed by calcination in air. The catalyst prepared this way exhibits an improved low-temperature activity for carbon dioxide reforming of methane, compared to the catalyst prepared without plasma treatment. The catalyst characterization using XRD, chemisorption and TEM analyses show that the plasma treatment followed by calcination thermally induces a generation of specific nickel species on the support. This kind of “plasma” metal species is highly dispersed on the support and can remain stable during reforming reactions. The average size of the “plasma” metal particles is ca. 5 nm. The plasma treatment can also enhance the anti-carbon deposition performance of the catalyst. The formation of carbon species that is responsible for catalyst deactivation can be inhibited. The catalyst stability is therefore improved.     

Oxygen storage in O2/Pt/YSZ cell

The phenomenon of electrochemical promotion of catalysis (EPOC) was initially characterized as fully reversible, i.e. the catalyst restores its initial activity after current interruption. However, it has been recently demonstrated that after prolonged anodic polarization an unusual promoted activity is observed for a certain time after current interruption. This phenomenon has been reported as permanent electrochemical promotion of catalysis (P-EPOC).In this work the oxygen storage reported as responsible of P-EPOC has been investigated by transient electrochemical techniques using an O₂(g)Pt/YSZ cell. A model has been proposed involving place interchange of Pt and O species in Pt/YSZ system. This seems to be induced by the strong lateral interaction of Pt–O surface dipoles and by increasing electric field at the Pt/YSZ interface. Such a rearranged oxide, so-called “phase oxide” can have a lower free energy than the initial monolayer oxide. This cooperative interaction of Pt and O species can lead to further thickening of this “phase oxide” especially at high temperature and potentials (currents). Furthermore, as the charge involved in this oxide thickening shows a t^1/2 dependency, the process seems to be diffusion controlled.     

Nitridation of MoO<Subscript>3</Subscript>/HZSM-5 and Fe-MoO<Subscript>3</Subscript>/HZSM-5

Thermal treatment and subsequent ammonolysis of MoO₃/H-ZSM-5 is shown to be an effective means for the preparation of zeolite dispersed nitrided molybdenum species. However, it is unlikely that these species reflect the bulk structures formed by analogous treatment of bulk MoO₃ precursor. The inclusion of low levels of Fe as a dopant does not produce any apparent effects on the Mo XPS spectra, although the amount of N incorporation is increased, and iron is shown to be reduced to Fe⁰. FTIR studies evidence the migration of molybdenum oxo species into the zeolite at the temperatures employed.     

13C nuclear magnetic resonance spectroscopy of saturated,unsaturated, and oxygenated fatty acid methyl esters

Chemical shifts have been assigned to all the separate signals in the¹³C nuclear magnetic resonance spectra of methyl stearate, oleate, and petroselinate by means of the second and third atom isotope effects in spectra of specifically deuterated esters. Spectra of almost all the isomeric hydroxy, acetoxy, and oxo stearates were also measured. From the assignments, the effects of the introduction of a double bond or an oxo, hydroxy, or acetoxy group at different positions on the fatty acid chain on the¹³C nuclear magnetic resonance spectra were determined. All the isomeric oxo stearates and most of the hydroxy and acetoxy stearates can be distinguished and identified by their¹³C spectra. Presented in the Symposium on NMR analysis of lipids at the AOCS Fall Meeting, Philadelphia, October 1974. National Research Council of Canada No. 150 87     

Catalytically Active Iron(IV)oxo Species Based on a Bis(pyridinyl)phenanthrolinylmethane

Starting from the mononuclear iron(II) complex [Fe(MeCPy₂Phen)(MeCN)₂]²⁺, a non-heme Fe(IV)oxo complex [Fe^IV(MeCPy₂Phen)O]²⁺ was synthesized via oxidation with meta-chloroperoxybenzoic acid (mCPBA). The Fe(IV)oxo complex was characterized using UV/Vis spectroscopy, Mößbauer spectroscopy and CSI mass spectrometry. The ability of this species to oxidize C−H bonds was tested with cyclohexane and adamantane as model substrates. For cyclohexane, an alcohol-to-ketone ratio (A/K) of 6.1 and efficiencies up to 55 were obtained. In case of adamantane, the ratio of tertiary over secondary products (3°/2°) is 38. In combination, this indicates the iron(IV)oxo complex being the catalytically active species.     

Oxo‐biodegradability of high‐density polyethylene films containing limited amount of isotactic polypropylene

Limited amount of isotactic polypropylene (iPP) is added to high‐density polyethylene (HDPE) containing 1% w/w an oxo‐biodegradable additive and extruded and converted to films. The films are put under UV irradiation for different periods of time. Irradiation of the films for 6 weeks imposes remarkable effects on viscosity average molecular weight (M_v) and carbonyl index (CI) of them. M_v decreases from 3.4 × 10⁵ to 4.7 × 10⁴ g mol^?1 for neat HDPE films; from 3.1 × 10⁵ to 3.3 × 10⁴ g mol^?1 for the films containing oxo compound, and from 1.5 × 10⁵ to 2.6 × 10⁴ g mol^?1 for the films containing oxo compound and 1% w/w iPP. Carbonyl index of the neat HDPE films increases from 4 to 8.7 while for the sample containing only the oxo compound it increases from 4.5 to 7.3 and for the sample containing both oxo compound and iPP it decreases from 12.0 to 8.8. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate more cracks and uniform degradation in the samples containing iPP and oxo compound. Thermogravimetric analysis (TGA/DTG) of the samples shows that the samples containing iPP and oxo compound have lower decomposition temperature after UV irradiation. Finally, it can be said that the presence of iPP in HDPE matrix containing oxo compound can improve HDPE oxo‐biodegradablity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45843.     

An FT-IR study of the conversion of 2-chloropropane, o-dichlorobenzene and dibenzofuran on V2O5-MoO3-TiO2 SCR-DeNOx catalysts

Spectra of the adsorbed species arising from contact of a V₂O₅-MoO₃-TiO₂ model SCR catalyst with ortho-dichlorobenzene (o-DCB) and dibenzofuran (DBF) and their evolution with the temperature are presented and discussed. Dichlorobenzene adsorbs weakly probably on Lewis acid sites through the chlorine atom. A very fast nucleophilic substitution on dichlorobenzene to a chlorophenate species occurs already at RT. On the contrary, adsorption of dibenzofuran is molecular, probably through the oxygen atom on Lewis sites. The aromatic rings of both molecules tend to be later oxidized to give carboxylate species. Parallel experiments with chloropropane show that dehydrochlorination occurs readily, hydrochloric acid is adsorbed quite weakly and that propene can be further oxidized. However, heavier oxidized species like cyclic anhydrides are also formed from chloropropane. The data suggest that the dechloration step of the phenyl ring could be not critical. On the contrary, the building-up of aromatic compounds from smaller molecules is possible and the oxidation of phenyl ring can be slow near reaction conditions. The possibility that the reaction between phenate species and chlorobenzenes give the “de novo” synthesis of dioxins is envisaged.     

CO oxidation over CuOx-CeO2-ZrO2 catalysts: Transient behaviour and role of copper clusters in contact with ceria

The effects of ZrO₂ content on the CO oxidation activity in a series of CuO_x/Ce_xZr_1−xO₂ (x = 0, 0.15, 0.5, 0.7 and 1) catalysts were investigated, both in the absence and in the presence of H₂, i.e. preferential CO oxidation—PROX. The investigation was performed under light-off conditions to focus the effects of transients and shut-down/start-up cycles on the performance; such phenomena are expected to affect the activity of PROX catalysts in small/delocalised fuel reformers. Evidence has been obtained for a transition from an “oxidized” towards a “reduced” state of the catalyst under the simulated PROX reaction conditions as a function of the reaction temperature, leading to different active species under the reaction conditions. Both CO oxidation activity and PROX selectivity appear to be affected by this process. IR characterisation of the surface copper species suggests an important role of reduced cerium sites in close contact with copper clusters on the CO oxidation activity at low temperatures.     

Numerical calculations of field enhancement and field amplification factors for a vertical carbon nanotube in parallel-plate geometry

Three types of models, with various emitter shapes in planar electrodes, have been employed to investigate field electron emission characteristics by finite element method. With the model of “hemisphere on a post”, two definitions of field enhancement and field amplification factors and their relation have been discussed systemically at different anode locations. The field distribution in the gap, between emitter apex and anode, is quantified by a field saturation factor. Simulation indicates that field distribution is an important aspect for explaining the nonlinear variation of field amplification factor at different anode locations. Furthermore, the field saturation factor can reflect the saturation degree of field amplification factor. The findings can be used not only in the model of “hemisphere on a post” but also approximately in the models of “two-stage hemisphere on a post” and “hemi-ellipsoid on plane”. Therefore, the fact can be approximately applied to every protruding shape of emitter that is supposed. Comparisons with previously reported experimental and theoretical results are also given.     

Selective catalytic reduction of nitric oxide with ammonia on Fe-ZSM-5 catalysts prepared by different methods

Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by TPR and XRD and tested in the NO-SCR by NH_3. The sublimation method leads to the most active catalysts. Nevertheless the preparation starting from Fe(acac)₃, which is a preparation easy to implement from an industrial point of view, seems to be a very attractive alternative way.On the most active catalyst, Fe(0.83)_subZSM-5, prepared starting from FeCl₃, a study of the mechanism was undertaken. In the initial step of the SCR reaction, the oxidation of NO in NO₂, the re-oxidation of Fe^II species in the active iron oxo species is the slow phase.     

Preparation and kinetic analysis of PS‐b‐PBA block copolymer by 4‐oxo‐TEMPO capped polystyrene macroinitiators

Polystyrene‐block‐poly(n‐butyl acrylate) block copolymers were prepared from 4‐oxo‐2,2,6,6‐tetramethylpiperidinooxy (4‐oxo‐TEMPO) capped polystyrene macroinitiators at a high temperature, 165°C. It was found that the number‐average molecular weight of PBA chains in block copolymers could reach above 10,000 rapidly at early stage of polymerization with a narrow polydispersity index of 1.2–1.4, but after that, the polymerization seemed to be retarded. Furthermore, according to the kinetic analysis, the concentration of 4‐oxo‐TEMPO was increased mainly by the hydrogen transfer reaction of hydroxylamine (4‐oxo‐TEMPOH) to growing radicals during polymerization. This increase in 4‐oxo‐TEMPO concentration could retard the growth of polymer chains. The rate constant of the hydrogen transfer reaction of 4‐oxo‐TEMPOH to growing radicals, k_H, estimated by the kinetic model is about 9.33 × 10⁴M^‐1s^?1 at 165°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Analysis of Fe species in zeolites by UV–VIS–NIR, IR spectra and voltammetry. Effect of preparation, Fe loading and zeolite type

Three procedures were employed for the preparation of Fe-zeolites with ZSM-5 (MFI), ferrierite (FER) and beta (BEA) structures: ion exchange from FeCl₃ solution in acetyl acetonate and solid-state ion exchange from FeCl₂ using an oxygen or nitrogen stream. A combination of UV–VIS–NIR spectra, IR spectra of skeletal vibrations and of adsorbed NO, as well as voltammetry provided information on the type of Fe species introduced. Single Fe(III) ion complexes (Fe(H₂O)_6−xOH_x) in hydrated zeolites were reflected in the charge-transfer bands at 33 100, 37 300 and 45 600 cm⁻¹. The single Fe(II) ions at cationic sites in evacuated zeolites yielded (through perturbation of framework T–O bonds) characteristic bands (910–950 cm⁻¹) in the region of the skeletal window. These Fe(II) ions with adsorbed NO were also reflected in vibrations at 1880 cm⁻¹. Dinuclear Fe–oxo complexes yielded the Vis band at 28 200 cm⁻¹. Voltammetry indicated the presence of Fe oxides (hematite) through the reduction peak at −0.7 V. Such oxide-like species were also reflected in the absorption edge at 19 800 cm⁻¹, and a doublet at 11 000 and 11 800 cm⁻¹ in the Vis spectra. Fe(II)–NO vibrations at 1840, 1810 and 1760 cm⁻¹ belonged to the undefined exposed Fe cations, probably originating from supported oxides. Using an ion exchange procedure, employing FeCl₃ in acetyl acetonate, exclusively Fe ions at cationic sites could be introduced at low concentrations (Fe/Al < 0.1). At higher Fe loadings, dinuclear Fe–oxo complexes were formed preferably in Fe-ZSM-5, but were absent in Fe-beta. Exclusively single Fe species could not be prepared at Fe concentrations above Fe/Al > 0.2; all three types of Fe species, single Fe ions, dinuclear Fe–oxo complexes and Fe oxides were formed.     

Identification of Neutral and Charged NxOy Surface Species by IR Spectroscopy

The infrared spectral performance of the N_xO_y species observed on oxide surfaces [N₂O, NO^-, NO, (NO)₂, N₂O₃, NO⁺, NO₂^- (different nitro and nitrito anions), NO₂, N₂O₄, N₂O₅, NO₂, and NO₃^- (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N₂, H-, and C-containing nitrogen oxo species, C─N species, NH_x species) are also briefly discussed. Some guidelines for spectral identification of N_xO_y adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.     

Biological Activity of Acyl Glucose Esters from <Emphasis Type="Italic">Datura wrightii</Emphasis> Glandular Trichomes against Three Native Insect Herbivores

Datura wrightii is dimorphic for leaf trichome type in southern California. “Sticky” plants produce glandular trichomes that secrete acylsugars, whereas velvety plants produce nonglandular trichomes. Glandular trichomes confer resistance to some potential insect herbivores and are associated with reduced feeding in the field by two native coleopteran herbivores: the tobacco flea beetle, Epitrix hirtipennis, and a weevil, Trichobaris compacta. In contrast, another native beetle, Lema daturaphila, damages sticky and velvety plants similarly in the field. A series of choice and no-choice “ester removal” and “ester addition” feeding experiments were performed in the laboratory to evaluate the role of acylsugars in feeding by all three insect species. Consumption of sticky leaves after their esters were removed by washing was compared to consumption of unwashed sticky leaves and velvety leaves in ester removal experiments. Consumption of velvety leaves was measured after acylsugars were applied to those leaves in controlled amounts in the ester addition experiments. Consumption by E. hirtipennis was reduced by acylsugars in all experiments. Consumption by T. compacta was reduced by acylsugars in the ester removal experiments, but not in the ester addition experiments. The location of the acylsugars at the tip of a long trichome, rather than simply on the leaf surface, may be an important component of the biological activity of acylsugars against T. compacta in nature. Consumption by L. daturaphila was not significantly reduced by acylsugars in any experiment. The acylsugars caused no significant mortality of any of the three insect species.     

Reactor and in situ FTIR studies of Pt/BaO/Al2O3 and Pd/BaO/Al2O3 NOx storage and reduction (NSR) catalysts

The reduction of NO under cyclic “lean”/“rich” conditions was examined over two model 1 wt.% Pt/20 wt.% BaO/Al₂O₃ and 1 wt.% Pd/20 wt.% BaO/Al₂O₃ NO_x storage reduction (NSR) catalysts. At temperatures between 250 and 350 °C, the Pd/BaO/Al₂O₃ catalyst exhibits higher overall NO_x reduction activity. Limited amounts of N₂O were formed over both catalysts. Identical cyclic studies conducted with non-BaO-containing 1 wt.% Pt/Al₂O₃ and Pd/Al₂O₃ catalysts demonstrate that under these conditions Pd exhibits a higher activity for the oxidation of both propylene and NO. Furthermore, in situ FTIR studies conducted under identical conditions suggest the formation of higher amounts of surface nitrite species on Pd/BaO/Al₂O₃. The IR results indicate that this species is substantially more active towards reaction with propylene. Moreover, its formation and reduction appear to represent the main pathway for the storage and reduction of NO under the conditions examined. Consequently, the higher activity of Pd can be attributed to its higher oxidation activity, leading both to a higher storage capacity (i.e., higher concentration of surface nitrites under “lean” conditions) and a higher reduction activity (i.e., higher concentration of partially oxidized active propylene species under “rich” conditions). The performance of Pt and Pd is nearly identical at temperatures above 375 °C.     

HEAT TRANSFER IN A CONDUCTIVE-HEATING AGITATED DRYER

The heat transfers between the heating plane and the granular materials in both the “Stationary heating-plane type” and the “Moving heating-plane type” of the conductive-heating agitated dryers were discussed mainly from the view point of the scale-up of the dryer. Under the condition of complete mixing in the bed of bulk materials, the heat transfer models proposed for both the two types of dryers can predict the heat transfer coefficients in any sizes of the dryers. However, the complete mixing is not usually accomplished in the large scale of dryer. Hence, an “Incomplete mixing model” was proposed to estimate the effect of the incompleteness of mixing on the heat transfer coefficient. In this model, the incompleteness of mixing can be apparently taken into consideration only by increasing the contact time.     

Mass Spectra of 4,4-Dimethyloxazoline Derivatives of Oxooctadecanoic Acids

The mass spectrometrical fragmentation patterns of the 4,4-dimethyloxazoline derivatives (DMOX) of the studied oxo fatty acids are easily to understand. The oxo group positions can be assigned unequivocally. The spectra are similar to those of the corresponding pyrrolidide derivatives. Since DMOX derivatization proofed to be good for the GC-MS analysis of epoxy fatty acids as well, the method could be interesting for studies on oxidized fatty acids, as well.     

Surface Science and Catalysis—Studies on the Mechanism of Ammonia Synthesis: The P. H. Emmett Award Address

About 5 years ago a Battelle Colloquium on “The Physical Basis of Heterogeneous Catalysis” was held in honor of Professor Emmett where he presented an introductory talk on 'Fifty Years of Progress in the Study of the Catalytic Synthesis of Ammonia' [1], a field to which he had made significant contributions during this whole period. So why another report on this topic? Justification can perhaps partly be obtained by some of Professor Emmett's concluding remarks which were not completely decisive with respect to the mechanism of this reaction: 'The experimental work of the past 50 years leads to the conclusion that the rate-determining step in ammonia synthesis over iron catalysts is the chemisorption of nitrogen. The question as to whether the nitrogen species involved on the surface is molecular or atomic is still not conclusively resolved. In fact, our own work in this field was mainly induced by this paper, and continuing discussions and correspondence with Professor Emmett were extremely helpful during its progress. I am therefore very much honored to be this year's recipient of the Emmett Award.     

Precipitate formation contributing to sump screens clogging of a nuclear power plant during an accident

For many years, the French “Institut de Radioprotection et de Sûreté Nucléaire” has developed studies concerning chemical effects, which can occur during a loss of coolant accident (LOCA) on a nuclear power plant, due to precipitate formation leading to an increase of head loss to sump screens. This increase can cause the loss of emergency core cooling system (ECCS) and of the containment spray system (CSS), which are the two removal heat safety systems which ensure the accident mitigation.These precipitates are formed by recombination of mineral species, which are released due to corrosion of immersed debris (particles of concrete, glass fibre insulation, piece of paint…). PHREEQC software has been used to identify nature and mass of precipitates that can be formed during a LOCA.This report presents the results of sensitivity studies carried out with PHREEQC. Chemical precipitate formation is studied as a function of several physical parameters, such as temperature, pH, nature and debris concentration. The optimal conditions in order to reduce the formation of precipitates are drawn from these calculations.     

13‐Oxo‐9(Z),11(E),15(Z)‐octadecatrienoic Acid Activates Peroxisome Proliferator‐Activated Receptor γ in Adipocytes

Peroxisome proliferator‐activated receptor (PPAR)γ is expressed in adipose tissue and plays a key role in the regulation of adipogenesis. PPARγ activators are known to have potent antihyperglycemic activity and are used to treat insulin resistance associated with diabetes. Therefore, many natural and synthetic agonists of PPARγ are used in the treatment of glucose disorders. In the present study, we found that 13‐oxo‐9(Z),11(E),15(Z)‐octadecatrienoic acid (13‐oxo‐OTA), a linolenic acid derivative, is present in the extract of tomato (Solanum lycopersicum), Mandarin orange (Citrus reticulata), and bitter gourd (Momordica charantia). We also found that 13‐oxo‐OTA activated PPARγ and induced the mRNA expression of PPARγ target genes in adipocytes, thereby promoting differentiation. Furthermore, 13‐oxo‐OTA induced secretion of adiponectin and stimulated glucose uptake in adipocytes. To our knowledge, this is the first study to report that 13‐oxo‐OTA induces adipogenesis through PPARγ activation and to present 13‐oxo‐OTA as a valuable food‐derived compound that may be applied in the management of glucose metabolism disorders.