M. Kubranová

Thermal properties of Co-, Ni- and Cu-exchanged montmorillonite with 3-hydroxypyridine

Thermal analysis (TG, DTG), powder diffraction analysis (RTG) and infrared absorption spectra (IR spectra) were used to study of release of 3-hydroxypyridine (3-OHpy) from Co-, Ni- and Cu-exchanged montmorillonite (Co-MMT, Ni-MMT, Cu-MMT). It was found that release of 3-OHpy under heating from Co- and Ni-MMT proceeds in three distinct steps while from Cu-MMT in four steps. The first step can be assigned to the release of physically sorbed 3-OHpy while the last one corresponds to the lattice dehydroxylation. The second step (Co-, Ni-MMT) and/or second and third steps (Cu-MMT) can be assigned to release of chemically bonded 3-OHpy. This investigation shows that studied exchanged montmorillonites predominantly exhibit Lewis acid character.

Thermochemical investigation : Ni(II)-3-pyridylcarbinol (ronicol) interactions in solid halogeno and thiocyanato complexes

The stoichiometry of the thermal decomposition and the stereochemistry of the following compounds was studied: NiR4Cl2 (I), NiR4Br2 (II), NiR4I2·2H2O (III) and NiR4(NCS)2 (IV) (R=3-pyridylcarbinol, ronicol). In complexes I and II the loss of the volatile ligands (on the TG curves) occurs in three steps (−2R, −R, −R), in complex III in four steps (−2H2O, −2R, −R, −R) and in complex (IV) in one step (−4R). According to the quasi-equilibrium decomposition temperatures, the thermodynamic stability of NiR4X4 complexes can be ordered in the sequence (according to X):Cl<Br≈I<NCS. The spectral and magnetic data for all initial complexes indicated pseudooctahedral configuration.

Thermochemical investigation of nickel(II)—nicotinamide—solvent interactions in solid halogeno and thiocyanato complexes☆

Abstract Stoichiometries of thermal decompositions have been studied for the following Ni( II ) nicotinamide (NA) complexes: Ni(NA) 2 Cl 2 ·2H 2 O ( I ), Ni(NA) 3 Br 2 ·4H 2 O ( II ), Ni(NA) 4 I 2 ·4H 2 O ( III ) and Ni(NA) 4 (NCS) 2 ·2C 2 H 5 OH ( IV ). Heating the compounds first results in a release of solvent molecules and desolvated compounds I ′- IV ′ are formed. NA molecules are released in two steps for complexes I ′, II ′, and III ′, and in one step for complex IV ′. Magnetic and spectral properties, as well as thermochemical data (quasi-equilibrium decomposition temperatures, DSC data) indicate an octahedral monomeric structure for complexes III , IV , III ′ and IV ′, and a polymeric structure for complexes I , II , I ′ and II ′, with adsorbed ( I ) and crystal water ( II , III ) or ethanol ( IV ).

Thermal and Infrared Study of Desorption of Pyridine and Pyridine Derivatives from Ni-exchanged Montmorillonite

Thermal analysis (TG, DTG) and infrared absorption spectra were used to study desorption of pyridine (py), 4-methylpyridine (4-Mepy) and 4-ethylpyridine (4-Etpy) from Ni(II)-exchanged montmorillonite (Ni-MMT). It is shown that the bonds between the derivatives of pyridine (R-py) and the montmorillonite exhibit predominantly Lewis acid character. The thermal stability of studied samples and the total amounts of R-py inserted in the porous structure of Ni-MMT increase in the following sequence: py/Ni-MMT<4-Mepy/Ni-MMT<4-Etpy/Ni-MMT, i. e. the influence of the substituent on the pyridine ring is evident.

Thermal decomposition reactions of nickel(II) complexes under quasi-equilibrium conditions: Part 3. The study of the relations between the thermal, spectral and structural properties of the Werner clathrates [Ni(4-Mepy)4(NCS)2] · 2G (where G represents naphthalene derivatives)

Abstract The relationship between the quasi-equilibrium decomposition temperature TD, the band shift Δṽ(3A2g → 3T1g) in the electronic spectra and the degree of tetragonal distortion ( R e R a ) of the host complex in the [Ni(4-Mepy)4(NCS)2] · 2G clathrates (where G is 1-methyl-, 2-methyl-, 1-bromo-, and 2-bromonaphthalene) was studied. It was found that with increasing Td the positive band shift also increases, whereas the degree of tetragonal distortion of the coordination polyhedra decreases. The reasons for these differences are discussed.

Studies of model macroscopic-defect-free materials. Part 1.—Investigations of the system 4CaO · Al2O3· Fe2O3–4CaO · 3Al2O3· SO3–hpmc–H2O by X-ray, thermoanalytical and NMR techniques

Model macroscopic-defect-free (MDF) materials representing selected compositions in the system 4CaO · Al2O3· Fe2O3–4CaO · 3Al2O3· SO3–hpmc–H2O have been prepared, with a variety of water-to-solid ratios and reactions quenched at varying times. Product mixtures were examined by analytical X-ray powder diffraction, thermal analyses and 27Al MAS NMR spectroscopy. Inhibition of crystallisation of hydrated products and elevated temperatures for thermal transformations of those products occur in materials prepared under MDF processing conditions, which incorporate organopolymer (hpmc, hydroxypropylmethylcellulose) into an amorphous hydrated product. Al–O–C crosslinks can be invoked to explain the 27Al spectra, and also the elevation in temperatures of thermal events.

Thermal decomposition reactions of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and thermal (thermodynamic) stability was studied for the Werner clathrates [Ni(4-Mepy)4(NCS)2]·G, whereG = benzene(I), toluene(II) andp-xylene(III). The loss of the volatile components occurs in five steps in compounds I and II and in four steps in the complex III.According to the quasi-equilibrium data the thermodynamic stability of these compounds can be ordered in the following sequence: I<II<III. The increasing host-guest interaction (larger positive band shift in the visible spectra) was accompanied by increasing in the quasi-equilibrium temperature (TD) for the complexes under study.ZusammenfassungAn den Werner-Klathratverbindungen [Ni(4-Mepy)4(NCS)2]G mitG=Benzol (I), Toluol (II) und p-Xylol (III) wurde die Stöchiometrie der thermischen Zersetzung und die thermische (thermodynamische) Stabilität untersucht. Der Verlust der flüchtigen Komponenten erfolgt in fünf Schritten bei den Verbindungen I und II und in vier Schritten bei Komplex III. In Übereinstimmung mit den Quasigleichgewichtsangaben kann die Reihenfolge der thermodynamische Stabilität dieser Verbindungen wie folgt angegeben werden: I II III. Die steigende Wechselwirkung zwischen Wirts- und Gastkomponente (größeres positives Band wird im sichtbaren Bereich verschoben) wird von einem Anwachsen der QuasigleichgewichtstemperaturTD der untersuchten Komplexe begleitet.

Thermochemical Properties of Neutral Complexes in Layer Silicates I. [Ni(4-Etpy)4(NCS)2] complex in montmorillonite and pillared montmorillonites

The stoichiometry of thermal decomposition and enthalpy and structural changes were studied for the compounds formed by penetration of [Ni(4-Etpy)4(NCS)2] (I) into Ca-montmorillonite (II) or Cr-, Zr- and Al-pillared analogues (III, IV and V, respectively). The mass fractions of complex I in II, III, IV or V are different. It was found for all studied compounds that the release of L (L=4-Etpy) is a three-step process (-2L, -1L, -1L), and differences occurred in enthalpy changes (δH in kJ per mole of I) corresponding to the individual processes. These differences and the changes in diffraction and spectral properties of the species formed after intercalation are assumed to have their roots in different intramolecular guest-host interactions in the studied compounds.

Cross-linking of atoms and thermal stability of new MDF compositions

We have summarized Al, Fe, C and P atoms incorporations within cross-linking interaction and location of those after MDF procedure of sulphobelitic clinker — hydroxypropylmethyl cellulose (hpmc) — sodium salt of polyphosphates (poly-P) compositions. Design of Al/Fe-O-C/P cross links is given and discussed. Thermoanalytical patterns (i) give the evidence of the presence of polymers in the reaction products and (ii) confirm the linkages of solidified polymers throughX=C or P of Al/Fe-O-X cross links in interphase regions with decomposition temperature interval higher than this in classical hydraulic materials. Designed local structure of interphase regions gives atomic level explanation of the densification of a bulk, its microstructure and exceptional technological properties. Similar phenomenon has been reported for the high aluminium — polyvinylalcohol/acetate MDF compositions. Moreover, variant clinker as well as polymers employed in syntheses represent one of the proposals aimed to the increase of the moisture resistence; our results are in the power of the above alternative for phases of sulphobelitic clinker.

The acidity of dealuminated clinoptilolite investigated by DSC, DTA and TG methods

Abstract Dealuminated NH 4 + -clinoptilolite samples, prepared using (NH 4 ) 2 SiF 6 and calcined at various temperatures, were used for the investigation of acidity properties. The strength of the acid sites was measured by a combination of TG and DSC measurements. It was found that the dealumination process starts preferentially at the weak acid sites. The intensive removal of aluminium from the strong acid sites started at the highest extent of dealumination.