Effect of chemical composition on the photocatalytic activity of potassium polytitanates intercalated with nickel ions

Results of a synthesis and study of the photocatalytic properties of nanosize powder compounds based on amorphous potassium polytitanate, modified with nickel ions are reported. The effect of protonation is noted, resulting in an increase in the specific surface area and adsorption capacity of the substances obtained. It is shown that the increase in the photoactivity of potassium polytitanates modified in aqueous solutions of nickel salts is due to the formation of multiple potassium polytitanate-NiO _x semiconductor heterojunctions on the surface and to the doping of potassium polytitanate with nickel ions.     

Synthesis of hexagonal nickel hydroxide nanosheets by exfoliation of layered nickel hydroxide intercalated with dodecyl sulfate ions

One-nanometer-thick nickel hydroxide nanosheets were prepared by exfoliation of layered nickel hydroxides intercalated with dodecyl sulfate (DS) ions. The shape of the nanosheets was hexagonal, as was that of the layered nickel hydroxides intercalated with DS ions. The nickel hydroxide nanosheets exhibited charge-discharge properties in strong alkaline electrolyte. The morphology of the nanosheet changed during the electrochemical reaction.     

Kinetic laws of thermal transformations in nickel nanofilms

Transformations in nickel nanofilms as a function of thickness (d = 3–60 nm) and temperature of heat treatment (T = 373–873 K) are studied via optical spectroscopy, microscopy, and gravimetry. It is found that, depending on the thickness of nickel films and temperature of heat treatment, the kinetic curves of the degree of transformation are satisfactorily described in terms of the linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference for Ni and NiO films and the photovoltage for Ni-NiO systems are measured. An energy band diagram for Ni-NiO systems is constructed. A model of the thermal transformation of Ni films, including the stages of oxygen adsorption, charge carrier redistribution in a Ni-NiO contact field, and the formation of nickel(II) oxide, is proposed.     

Surfactant intercalated alpha-hydroxides of cobalt and nickel and their delamination--restacking behavior in organic media

Dodecyl sulfate and dodecylbenzene sulfonate intercalated alpha-hydroxides of nickel and cobalt were synthesized by ammonia precipitation. These solids delaminate to give a colloidal dispersion of layers in organic solvents such as 1-butanol. The dispersed layers could be reassembled either by evaporation of the colloid or by coagulation by the addition of a polar solvent.     

Liquid-liquid biphasic synthesis of layered zinc hydroxides intercalated with long-chain carboxylate ions and their conversion into ZnO nanostructures

A method for synthesizing layered zinc hydroxide compounds in high yields is developed using an immiscible liquid-liquid system in one pot. Long-chain carboxylate ions such as heptanoate, decanoate, and dodecanoate were successfully intercalated between zinc hydroxide layers in one process starting from a xylene-water system. Typically, a xylene phase dissolving the respective carboxylic acids was allowed to stand in contact with an aqueous phase dissolving zinc nitrate hexahydrate and urea. During keeping the resultant biphasic system at 80 °C, urea was thermo-hydrolyzed to supply OH(-) in the aqueous phase while the carboxylic acids were continuously transferred from the xylene phase under the distribution law. The aqueous phase was then supersaturated, and a solid phase of layered basic zinc carboxylate was precipitated as films on glass substrates through heterogeneous nucleation and subsequent two-dimensional crystal growth. Crystal structures and morphology of the films were modulated by the kind of the carboxylic acids employed. The layered basic zinc carboxylate films could be converted to nanostructured, mesoporous ZnO films by heating at 450 °C in air. The relationship between the initial solution compositions and the final solid products was systematically examined to discuss reaction mechanisms in the biphasic systems.     

Electrochemical synthesis of layered manganese oxides intercalated with tetraalkylammonium ions

Thin films of birnessite-type layered manganese oxides with various interlayer spacings have been prepared on a platinum electrode by a one-step electrochemical procedure. The process involves a potentiostatic oxidation of aqueous Mn(2+) ions at around +1.0 V (Ag/AgCl) in the presence of tetraalkylammonium cations with different alkyl chain lengths. X-ray diffraction indicates that the films deposited with tetrabutylammonium (TBA), tetrapropylammonium (TPA), and tetraethylammonium (TEA) ions are composed of a single phase where unhydrated tetraalkylammonium ions are accommodated as a monolayer between manganese oxide layers. The interlayer spacing of the products increases in an order of TEA < TPA < TBA. The film deposited with tetramethylammonium (TMA) is a mixture of two phases relating to hydrated and unhydrated guest cations, the former being predominant probably as a result of less hydrophobic property of TMA compared to that of other tetraalkylammonium ions. The TBA(+)-intercalated Mn oxide film-coated electrode exhibits a good charge/discharge property in a KCl solution between 0 and +0.8 V. In this case, TBA(+) ions between the Mn oxide layers are rapidly replaced with K(+) in solution by ion exchange, accompanying a shrinkage of the interlayer. The incorporated K(+) ions as well as protons play an important role in the electrochemical conversion between Mn(4+) and Mn(3+) in the oxide layer. In the TBACl solution, the interlayer TBA(+) ions can be excluded electrochemically during the positive-going scan, concomitant with the oxidation of Mn(3+) sites. This causes an anodic current and the accompanying shrinkage of the interlayer. On the reverse scan, however, the compressed interlayer does not allow the incorporation of bulky TBA(+) ions from the electrolyte, with virtually no cathodic current observed. Such an obvious difference in electrochemical behavior between the two electrolytes can be recognized by considering that most of the Mn oxide surface is present inside the layered structure, not on the external surface. This indicates that the layered structure is formed over the entire film.     

Dual bimodal polyethylene prepared by intercalated silicate with nickel diimine complex

The ethylene polymerization was catalyzed by the intercalated montmorillonite with the nickel complex, [ArN?C(Me)? C(Me)?NAr]NiBr₂ (Ar = 2,6‐C₆H₃ (i‐Pr)₂). Polymer with low melting point and high molecular weight was produced at the early stage of polymerization followed by formation of polymer with high melting point and low molecular weight. It is proposed that the gallery of silicate lowers the propagation rate of polymerization and frequency of “chain walking” process of nickel complex anchored inside the gallery, which produces polymer with low molecular weight and low branching, whereas the nickel complex immobilized on the surface of silicate generates polymer with high molecular weight and high branching. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5506–5511, 2005     

Paramagnetic complexes of 9,10-anthraquinone on zeolite surfaces and their thermal transformations

The concentration of one-electron transfer sites on the surface of H-ZSM-5, H-Y, H-mordenite, and H-β zeolites was measured by EPR using 9,10-antrhraquinone as a probe. It has been found that the hyperfine structure from four protons typical for one-centered complexes of anthraquinone with one acidic site was observed in the EPR spectra after anthraquinone interaction with a zeolite surface in the temperature range of 373 to 423 K. It has been established that an elevated temperature of 473 K promoted the decomposition of the adsorbed anthraquinone and the disappearance of the hyperfine structure. It has been shown that the thermal instability of anthraquinone adsorbed on zeolites changed in the series H-β > H-Y > H-ZSM-5 ～ H-mordenite; the coke-forming ability of zeolites with regard to n-decane at 443 K changed in a similar manner. It has been established that the presence of air promoted coke-forming processes upon interaction between n-decane and zeolites.     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

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Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

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, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

Complexing properties ofSchiff bases with copper and nickel ions

Summary The solution properties ofPPP,QPP, and their complexes with copper and nickel were investigated. The composition and stability of the complexes have been determined using the spectrophotometric method atT=25±1 °C, constant ionic strength (I=0.5M, adjusted with KNO₃) and a volume ratio of methanol/water of =0.10 and 0.16 forPPP andQPP, respectively, due to lower solubility ofQPP. The experimental results have been fitted to the theoretical equations using the computerized iterative method of successive approximation. The influence ofpH and addition of another benzene ring to the ligand molecule has been studied. The structures of isolated solid metal complexes withQPP were investigated by infrared and mass spectroscopy. The use ofPPP andQPP as analytical reagents for spectrophotometric determinations of copper and nickel is discussed.

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Komplexbildende Eigenschaften vonSchiffschen Basen mit Kupfer- und Nickelionen

Zusammenfassung Die Eigenschaften vonPPP,QPP und ihrer Komplexe mit Kupfer und Nickel in Lösung wurden untersucht. Zusammensetzung und Stabilität der Komplexe wurde bei 25±1 °C, konstanter Ionenstärke (I=0.5M, eingestellt mit KNO₃) und einem. Methanol/Wasser-Volumenverhältnis von =0.10 und 0.16 fürPPP bzw.QPP (bedingt durch die geringere Löslichkeit vonQPP) bestimmt. Die experimentellen Ergebnisse wurden mittels eines Algorithmus zur sukzessiven Approximation an die theoretischen Gleichungen angepaßt. Der Einfluß despH-Werts und eines weiteren aromatischen Rings am Liganden wurden studiert. Die Strukturen der isolierten festen Komplexe mitQPP wurden mittels IR- und Massenspektroskopie untersucht. Die Verwendung vonPPP undQPP als analytische Reagenzien zur spektrophotometrischen Bestimmung von Kupfer und Nickel wird diskutiert.

     

Hydrodesulfurization activity and transformations of nickel molybdate hydrate

Nickel molybdate hydrate has been found to be an effective precursor catalyst for the hydrodesulfurization of thiophene. Calcination of the hydrate at 300°C and presulfidation with H₂S are favorable treatments for higher activity.

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, . 300°C H₂S , .

     

Potassium and oxygen diffusion and segregation in nickel

Nickel is used as catalyst in alkaline electrochemical systems like batteries, electrolyzers and fuel cells. Adsorption experiments from potassium on a thin NiO(100) epitactic layer on an Ag(100)-single crystal substrate showed that potassium intrudes in that NiO-layer where at a temperature of 350 K a mixed oxide phase was built. At 120 K metallic potassium was adsorbed on the NiO surface. A symmetric K2p-peak showed that potassium is in the oxidized state compared to the asymmetric peak of metallic potassium. No potassium diffused into metallic nickel at a temperature of 450 K. The electrochemically oxidized surface layer consisted of nickel, oxygen and also potassium. After heating and ion-etching no more potassium was detectable by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDX). But it was visible again after oxidizing and heating of the sample to 670 K. Therefore, the potassium must have been in the bulk. It diffused to the surface if there was oxygen at sufficiently high temperatures. Further heating reduces the surface and the potassium also disappeared. Received: 6 September 1998 / Revised: 1 April 1999 / Accepted: 16 April 1999     

Sorption of nickel and cobalt ions onto cobalt and nickel ferrites

The corrosion of the metal parts in the primary circuit of pressurized water reactors leads to the release of colloidal particles (NiFe(2)O(4), CoFe(2)O(4), NiO, Ni...) and ionic species (Co, Ni, Cr...). Particles can interact with ionic species in the primary medium, contributing to their transport and to their deposition onto surfaces outside the neutron flux generating radioactive contamination. Sorption and zetametry experiments at 25 °C were performed on the Ni(2+)/CoFe(2)O(4) and Co(2+)/NiFe(2)O(4) systems in order to determine the behaviour of corrosion products in the fluid of the primary circuit. Sorption appears as surface complexation starting from pH 6 and is followed by precipitation of hydroxide above pH 7.5. Complexation and solubility constants were obtained from the modelling of sorption curves. The two oxide systems present a very similar sorption behaviour, but some differences, due to their different isoelectric points, could be observed on zetametric measurements.     

Photochemical and thermal transformations of azomethine imines

The thermal and photochemical fragmentations of a few bisazoalkenes have been investigated. 2-Phenyl-4,5-disubstituted-1, 2,3-triazoles were obtained both in the thermolysis and photolysis of 1, 2-bisphenylazo-(4, 4′-dichloro) stilbene, 1, 2-bisphenylazo(4, 4′-dimethoxy)stilbene, 1, 2-bisphenylazocyclohexene and o-(phenylazo) phenyldiazocyanide. Both 2, 3-bisphenylazo-2-butene and 1, 2-bisphenylazoethylene failed to undergo either photolysis or thermolysis in the expected manner. However, 2, 3-bisphenylazo-2-butene underwent an acid-catalysed valence isomerisation to anhydro 1-phenylimino-2-phenyl-4, 5-dimethyl-1, 2, 3-trizolium hydroxide, which on photolysis gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. The same iminotriazolium intermediate gave a cycloadduct, 2, 6-diphenyl-3, 3a-dimethyl-4, 5-dicarbomethoxypyrazolino [2.3.c][1.2.3] triazole, on treatment with dimethyl acetylenedicarboxylate, whereas treatment with carbon disulphide gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. Both photolysis and thermolysis of C-biphenylene-N^α(4-chlorophenyl)-N^β-cyanoazomethine imine gave 9-fluorenone-N- (4-chlorophenyl) anil. Photolysis of 1, 2-bisphenylazoacenaphthylene in methanol gave acenaphthenequinone monophenylhydrazone.     

Study of the structure and thermal behaviour of intercalated kaolinites

Intercalation complexes of three different Hungarian kaolinites with hydrazine and potassium acetate were investigated by FT-IR (DRIFT) spectrometry, X-ray diffraction, and thermogravimetry combined with mass spectrometry. Differences were found in the thermal behaviour of the complexes as well as in the rehydration — reexpansion patterns of the heated intercalates. An XRD method is proposed for the distinction of kaolinite and 7.2 Å halloysite present in the same mineral.The authors wish to thank Dr. E. Máttyás for providing the kaolinite samples and for carrying out their chemical analysis. Financial support from the Hungarian Scientific Research Fund under grant No. OTKA-014179 is gratefully acknowledged.     

Catalytic and thermal transformations of methyl- and isopropylcyclobutanes

Conclusions The thermal decomposition of the methyl- and isopropylcyclobutanes in the presence of quartz powder proceeds only with cleavage of the ring at two bonds, while in the presence of amorphous aluminosilicate and zeolite NM the additional reactions of ring opening, cleavage of groups containing one carbon atom, and hydrogen redistribution take place.Translated from Izvestya Akademii Nauk SSSR, Seriya Khimieheskaya, No. 1, pp. 170–172, January, 1973.