A 13C and 15N Solid State NMR Study of the Reactions of Acetone Oxime Adsorbed on FeZSM-5

The reactions of acetone oxime, a proposed reaction intermediate for the SCR (Selective Catalytic Reduction) of NO with propane on FeZSM-5, have been studied with ¹³C and ¹⁵N solid state MAS NMR (magic angle spinning nuclear magnetic resonance). FeZSM-5 with three different loading levels was prepared by the sublimation method. The thermal reactions of acetone [2-¹³C] oxime adsorbed on FeZSM-5 samples with different iron loadings were monitored by ¹³C MAS NMR by heating to the desired temperature and then cooling to room temperature for data acquisition. For the sample with the lowest iron loading (Fe/Al = 0.11), acetic acid and N-methyl-2-propanamine were formed by the decomposition of acetone oxime. For the samples with the higher iron loadings (Fe/Al = 0.69 and 0.91), acetone, N,N-methyl-2,2-propanediamine, and N-methyl-2-propanimine were formed by the decomposition of acetone oxime. ¹⁵N MAS NMR was used to investigate reactions of ¹⁵NO and acetone oxime on the FeZSM-5 samples. The formation of gas phase N₂ and N₂O was observed.     

Preparation and characterization of WO3/SiO2 catalysts

Two sets of WO₃/SiO₂ catalysts were prepared from (NH_{4 6}H₂W₁₂O₄₀ (aqueous method) and W(³-C₃H₅)₄ (non-aqueous method). The molecular structures and dispersions of the surface tungsten oxide species for the WO₃/SiO₂ catalysts under ambient and in situ dehydrated conditions were investigated by Raman spectroscopy. The samples prepared from (NH₄)₆H₂W₁₂O₄₀ (aqueous method) exhibit very strong Raman features due to the presence of crystalline WO₃ and the samples prepared from W(³-C₃H₅)₄ (non-aqueous method) do not possess crystalline WO₃. These results suggest that the preparation method exerts an influence on the dispersion of the surface tungsten oxide species on SiO₂. The surface tungsten oxide species under ambient conditions possess polytungstate clusters, W₁₂O ₄₂ ^12– , on the silica support. Upon dehydration at elevated temperatures, the hydrated polytungstate clusters decompose and interact with the silica support via the formation of isolated, octahedrally coordinated tungsten oxide species.     

SOLVENT EXTRACTION OF ZINC FROM CHLORIDE MEDIA WITH SECONDARY LONG-CHAIN ALKYLAMINE

In the solvent extraction of zinc from chloride media with a secondary long-chain alkylamine, Amberlite LA-2, aggregations of ammonium chloride salt of alkylamine and zinc-complex with alkylamine and distribution equilibrium of zinc were investigated at 30 "C using n-hexane as a diluent. The ammonium chloride salt of alkylamine exists as monomeric, dimeric, trimeric and tetrameric species (BHCl, (BHCl)₂, (BHCl)₃ and (BHCl)₄, respectively). The zinc-complex exists as monomeric and dimeric species ((BH)₂ZnCl₄ and ((BH)₂ZnCl₄)₂, respectively). Zinc is extracted according to the extraction reaction in the lower loading region of zinc to alkylamine and according to the extraction reaction in the higher loading region.     

Studies on Chlorided Pt/Al2O3 Catalysts: Preparation, Characterization and n-Butane Isomerization Activity

A series of chlorided Pt/Al₂O₃ (both and ) catalysts were prepared and characterized for various physicochemical properties. The chloride content of the catalysts was found to increase with chloride treatment time up to a certain level and then decrease owing to prolonged exposure at high temperature. The surface area and pore volume of the catalysts were decreased by chloride treatment. The activity of the prepared catalysts were tested in n-butane isomerization. The platinum content of the catalysts was found to have no effect on catalytic activity up to 0.2 wt% whereas the chloride content of the catalyst strongly influenced the activity and a >20-fold increase in activity was observed on chloriding Pt/Al₂O₃ catalysts. The catalyst activity was found to be directly related to its acidity.     

Electrochemical reduction of 2-nitroimidazole in aprotic medium: Influence of its dissociation equilibrium on the reduction mechanism

The electrochemical reduction of 2-nitroimidazole in a non-aqueous medium using cyclic voltammetry (CV) at a mercury electrode was carried out.The 2-nitroimidazole derivative in DMF + 0.1 M tetra(n-butyl)ammonium hexafluorophosphate (TBAHFP6) resulted in the following dissociation equilibrium:

HNRNO₂ ? ⁻NRNO₂ + H⁺     

Reduction of oxygen by hydroxylammonium salt or hydroxylamine over supported Au nanoparticles for in situ generation of hydrogen peroxide in aqueous or non-aqueous medium

Reaction of O₂ with hydroxylamine or its salts over a number of supported gold catalysts containing Au nanoparticles (at 10–70 °C) has been studied at atmospheric pressure for the in situ generation of H₂O₂ (required for organic oxidation reactions in the synthesis of fine/specialty chemicals) in aqueous (water) or non-aqueous medium. Hydrogen peroxide in high yields with harmless by-products (viz. water and nitrogen) can be generated in situ by the reduction of O₂ by hydroxylammonium sulfate (or chloride) or hydroxylamine using the supported gold catalysts particularly Au/Gd₂O₃, Au/La₂O₃ and Au/MgO, in aqueous (water) or non-aqueous (viz. methanol) medium at close to ambient conditions. The reduction of O₂ by hydroxylammonium salt to H₂O₂, however, requires preneutralization of the salt by alkali; in the absence of the neutralization, only water is formed in the reaction.     

Electrochemical investigation on prostaglandin F2α derivatives. II. Cathodic reduction of the iodinated prostaglandin F2α and its methyl ester

Based on voltammetric studies, preparative controlled potential reduction on an Hg cathode of iodinated PGF₂ (IPG) resulted in the production of either PGF₂ (nearly quantitatively) or PGF₂ and the biologically active PGI₁ (in a 2:3 ratio at maximum), depending on the medium and the potential used. The 5-Z isomer percentage in the PGF₂ thus formed varied between 50 and 60, while originally, before the anodic iodination and the subsequent reduction of IPG, this ratio was 98%. The electrochemically formed PGI₁ contained 95% 6-S and 5% 6-R isomer. In any selected medium the first voltammetric wave can be ordered to PGF₂ formation, and that of the second wave (in aqueous and non-aqueous media) to PGI₁ formation. On the basis of the experimental results a mechanism is proposed for the electroreduction process in aqueous media.     

Iron‐Promoted Electrophilic Annulation of Aryl Enynes with Disulfides or Diselenides Leading to Polysubstituted Naphthalenes

An iron‐promoted electrophilic annulation of aryl enynes with disulfides or diselenides has been developed. In the presence of iron(III) chloride (FeCl₃) and iodine (I₂,), a variety of trifluoromethyl‐containing aryl enynes underwent electrophilic annulation with various disulfides or diselenides successfully to afford the corresponding polysubstituted naphthalenes in moderate to excellent yields.

     

Decontamination of 1,2-Dichloroethane DNAPL in Contaminated Groundwater by Polymer-Modified Zero-Valent Iron Nanoparticles

Remediation of dense non-aqueous phase liquids (DNAPLs) contaminants in groundwater has received considerable attention in the environmental field. Generally, DNAPLs can flow with groundwater and further infiltrate down to deeper aquitard zone that is difficult to be removed by pumping. The DNAPLs may also contaminate the soil and groundwater concurrently in the duration of flowing with groundwater slowly. In this study, remediation of 1,2-dichloroethane (1,2-DCE) in DNAPL contaminated groundwater was studied by a reductive reaction with polyethylenimine (PEI) surface-modified zero-valent iron nanoparticles (PEI-nZVI). The prepared PEI-nZVI was injected into upstream wells and reach the plume of DNAPLs down with the flowing groundwater. Moreover, nZVI was further characterized after field injection and 1-day reaction with the contaminants to assess its effectiveness for the on-site reduction of 1,2-DCE. After direct injection of PEI-nZVI into the contaminated plume, the concentrations of 1,2-DCE was significantly reduced. Moreover, the plume was decontaminated to nontoxic species onto the highly active nZVI. By using resistivity image profiling (RIP), the conductivity data of modified nZVI solution and sampled groundwater were similar. In addition, RIP can reveal complex subsurface DNAPLs structures by dense sampling of resistivity variation at shallow depth. Additionally, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy studies indicated that after the reductive reaction, nZVI and PEI-nZVI were oxidized to Fe₃O₄. The interatomic distances for the reacted samples were 1.95 Å and 1.93 Å, respectively. The combined technique of floating surface-modified nZVI and RIP method would be economically and environmentally attractive.

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Modelling of the sodium-ferrous chloride electrochemical cell

A computer model of the discharge behaviour of the Na-FeCl₂ cells is presented. The cell comprises a liquid sodium anode and a porous iron/iron chloride cathode impregnated with NaCl-saturated AlC₃ : NaCl molten electrolyte. The anode and cathode are separated by a -alumina solid electrolyte. Both cylindrical (inner and outer cathodes) and flat-plate cell geometries can be simulated. Macroscopic porous electrode theory is used. The cathode reaction is considered to be effectively a solid state process, in that the solubilities of FeCl₂ and NaCl are not taken into account. The model predictions show good correspondence with experimental data. The results provide useful insight into cell performance in general and the detailed performance of the cathode in particular.     

Preparation of nanosize Pt clusters using ion exchange of Pt(NH3) 4 2+ inside mesoporous channel of MCM-41

Mesoporous molecular sieve MCM-41 with a Si/Al ratio of 35 was obtained by hydrothermal synthesis using a gel mixture with a molar composition of 6 SiO₂0.1 Al₂O₃1 hexadecyltrimethylammonium chloride 0.25 dodecyltrimethylammonium bromide 0.25 tetrapropylammonium bromide0.15 (NH₄)₂O1.5 Na₂O300 H₂O. The MCM-41 sample was calcined in O₂ flow at 813 K and subsequently ion exchanged with Ca²⁺. A small Pt cluster has been supported on the MCM-41 sample following a procedure using ion exchange of Pt(NH₃) ₄ ²⁺ . The Pt(NH₃) ₄ ²⁺ ion supported on MCM-41 has been activated in O₂ flow at 593 K and subsequently reduced with Fh flow at 573 K, in the same way used for the preparation of a Pt cluster entrapped inside the supercage of zeolite NaY. The resulting Pt cluster supported on the MCM-41 shows hydrogen chemisorption oftotal two H atoms per Pt at 296 K (based on the total amount of Pt) and high catalytic activity for hydrogenolysis of ethane. The chemical shift in¹²⁹Xe NMR spectroscopy of adsorbed xenon indicates that the Pt cluster is located inside the mesoporous molecular sieve.     

1,4-pentadien-3-one-1-p-hydroxyphenyl-5-p-phenyl Acrylate: Crosslinking Studies and Reactivity Ratios with Glycidyl Methacrylate

1,4-pentadien-3-one-1,5-bis(p-hydroxyphenyl) (PBHP) was synthesized by reacting p-hydroxybenzaldehyde and acetone in the presence of HCl gas. 1,4-pentadien-3-one-1-p-hydroxyphenyl-5-p-phenyl acrylate (HPA) was prepared by reacting PBHP with acryloyl chloride in ethyl methyl ketone (EMK) medium at 0°C. Copolymerization of different feed compositions of HPA with glycidyl methacrylate (GMA) was carried out using benzoyl peroxide (BPO) as initiator in EMK solvent under nitrogen atmosphere at 70±1°C. Polymers thus synthesized were characterized by IR and NMR (¹H/¹³C) spectroscopic techniques. Reactivity ratios of the monomers were calculated from the ¹H NMR data by applying linearization methods such as Fineman–Ross, Kelen–Tudos and extended Kelen–Tudos methods. Photocrosslinking property of the polymer samples was studied using the solvent method. Thermal stability of the polymers were measured using thermogravimetric analysis. Molecular weights (M _w and M _n) and polydispersity value of the polymer were determined using gel permeation chromatographic technique.     

One-step preparation of carbonaceous solid acid catalysts by hydrothermal carbonization of glucose for cellulose hydrolysis

Carbonaceous materials (CM-SO₃H, CM-COOH) were prepared and functionalized in-situ in a single step with SO₃H or COOH groups by hydrothermal carbonization of glucose in the presence of sulfosalicylic acid or acrylic acid as co-monomer. The prepared materials were evaluated as solid acid catalysts and exhibited good catalytic activity for the hydrolysis of cellulose in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). Remarkably, the carbonaceous materials obtained by the hydrothermal carbonization of glucose could be used directly for the catalytic hydrolysis of cellulose without any post-modification or in-situ functionalization and were surprisingly efficient.     

Role of indium in promoting anodic dissolution of Al-In alloys in non-aqueous electrolyte

Exploratory work on the anodic dissolution behaviour of aluminium and aluminium binary alloys in electrolytes in non-aqueous organic solvents is reported. Commonly used electrolytes for non-aqueous battery systems were selected on the basis of their conductivities and activities for anodic dissolution of Al and Al-alloy anodes. It is found that Al–In alloy electrodes exhibit an exceptionally active anodic dissolution behaviour in a 1 M solution of AlCl₃ in anhydrous acetonitrile. The steady-state Tafel polarization plots for dissolution of pure Al, Al–Sn, Al–Ga and Al–In alloy anodes are compared, and a.c. impedance spectra for an Al–In alloy anode in 1 M solution of AlCl₃ in CH₃CN are evaluated and discussed. The In component, like Ga or Hg, interferes with passivation of Al during its anodic dissolution and thus promotes an active condition on the metal surface leading to relatively high anodic dissolution current-densities at substantially negative electrode potentials.     

Unusual iron-mediated C–N bond formation and synthesis of the Fe(III) complex of a polypyridine ligand with one carboxamide group

A high-spin iron(III) chloro complex [(PaPPy₃)Fe(Cl)](ClO₄) (1, where =N,N-bis(2-pyridylmethyl)amine-N-propyl-2-pyridine-2-carboxamide) has been synthesized via the “template effect” and structurally characterized. The template reaction leads to the formation of a new carbon–nitrogen bond from coupling of a primary alkyl chloride with a secondary amine.     

Preparation and electrochemical characterization of Ti/Ru x Mn1−x O2 electrodes

DSA^® type electrodes of ruthenium–manganese mixed oxides (30 at % Ru < 100) supported on titanium were prepared by the spray-pyrolysis technique, using Ru(NO)(OH) _x (NO₃)_3–x and Mn(NO₃)₂ as precursors. Electrodes were characterized by SEM, XRD and cyclic voltammetry. Their behaviour as anode for the chlorine and oxygen evolution reactions was also evaluated by polarization curves. The stability of the mixed oxides was determined through accelerated tests of service life. It has been verified that the best performance on the apparent electrocatalytic activity of both reactions as well as on stability is achieved at a composition of about 70% Ru.     

Understanding heterogeneous catalysis on an atomic scale: a combined surface science and reactivity investigation for the dehydrogenation of ethylbenzene over iron oxide catalysts

In order to study the dehydrogenation of ethylbenzene to styrene, epitaxial iron oxide model catalyst films with Fe₃O₄(111), -Fe₂O₃(0001) and KFe _x O _y (111) stoichiometry were prepared in single crystal quality on Pt(111). They were investigated using surface science techniques before and after atmospheric pressure reaction experiments in a newly designed single crystal flow reactor. As expected from low-pressure measurements, Fe₃O₄(111) is catalytically inactive. The catalytic activity of -Fe₂O₃(0001) starts after an activation period of about 45 min. After that, the surface is essentially clean but shows a high concentration of defects. On the potassium-promoted films, however, the activation period is much longer, the activity then is higher and the surface gets covered completely with carbon and oxygen during reaction. This indicates a different reaction pathway on the promoted films with a carbon–oxygen species as catalytically active species.     

An Electrochemical and XPS Study of Ag–Pb Binary Alloys incorporated in Nafion® Coatings

Glassy carbon electrodes coated with thin films of Nafion^® metalized with silver and lead species were investigated by cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS). Metalization of Nafion^® film was accomplished by dipping the coated electrodes in 3 mM AgNO₃ + 3mM Pb(NO₃)₂ solution for 10 min. The resulting chemically modified electrodes were electrochemically characterized toward the oxidation of amino compounds in carbonate solutions buffered at pH 10. Under chronoamperometric experiments carried out at a constant applied potential of 0.95 V vs SCE, the linear range (r ²>0.995) was determined to be at least three decades and the limit of detection range from 26M (ethylamine) and 65M (tert-butylamine), for the investigated amino compounds. The perm-selective properties of the Nafion^® film with respect to anion species were investigated toward the electrooxidation of ethylamine in presence of large concentration of chloride ions. The XPS analysis revealed heterogeneous distribution of the catalytic species dispersed in the metalized Nafion^® film. Thus, a comparison of the spectra of Ag3d and Pb4f acquired at various take-off angles, indicates an increase in the atomic ratio Ag:Pb and a notable enrichment of lead oxide species in the outer surface of the film when compared with the bulk membrane coated electrode.     

Synthesis of Titanates with a Ramsdellite-Type Tunnel Structure Crystallizing in the Li<Subscript>2</Subscript>O-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> System in Different Gaseous Media

The ramsdellite-type phases crystallizing in the Li₂O-Fe₂O₃-TiO₂ system in the course of synthesis in gaseous media at different oxygen partial pressures are studied. Solid solutions based on the ramsdellite structure with the composition Li₂Ti_3?xFe _x O_{7 ? δ} (0 ≤ x ≤ 0.7) are prepared in an oxidizing medium (P_O2 = 1 atm) for the first time. Analysis of the results obtained by electron paramagnetic resonance and Mossbauer spectroscopy revealed that, in these solid solutions, all iron ions are in the oxidation state Fe⁺³.