Hazard in reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw material with sulphuric acid was investigated in ‘hazard’ type calorimetric system. The investigations show the essential influence of initial temperature, particle size distribution and concentration of sulphuric acid on rate and heat power of reaction and determine the limits of safety of the process and also its efficiency.     

Thermal transformations of selected transition metals oxyhydroxides

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

ZnFe2O4 as a new catalyst in theC-methylation of phenol

This paper reports the investigation ofC-alkylation of phenol with methanol over zinc ferrite as a catalyst. The reactions were carried out in gas phase at atmospheric pressure in dependence of increasing temperature. The total selectivity towardsortho-cresol and 2,6-xylenol over 300°C surpassed 90%. ZnFe₂O₄ was obtained by oxidative precipitation method from solution of iron (II) sulphate and zinc sulphate at 60°C. Based on the results, the best equation describing the oxidation reaction rate was found. The obtained products have been investigated using X-ray fluorescence spectrometry and X-ray diffraction analysis.     

Calculation of kinetic parameters from TG curve on the base of dehydration process of hydrous titanium dioxide

A direct method of evaluating of kinetic equation parameters based on TG curve is proposed. The method was applied to calculate kinetic parameters of the process of dehydration of hydrous titanium dioxide.

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Zusammenfassung Es wird ein direktes Verfahren zur Bestimmung der Parameter der kinetischen Gleichung auf der Basis von TG-Kurven gegeben. Das Verfahren wurde zur Berechnung der kinetischen Parameter des Dehydratationsprozesses von wasserhaltigem Titandioxid benutzt.

     

Thermal transformations of hydrous titanium dioxide

During heating hydrous titanium dioxide with a general empirical formula TiO₂·xH ₂O·ySO ₃ prepared by hydrolysis of titanium sulphate solution drying, dehydration, desulphurization and anatase — rutile transformation proceed. The studies applying the DTA, TG, DTG methods have been carried out. To separate the particular effects damp samples, dried up to constant mass samples as well as samples after removing sulphur compounds have been used.

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Zusammenfassung Während des Erhitzens von wasserhaltigem Titandioxid der allgemeinen Formel TiO₂ ·xH₂O ·ySO₃, hergestellt durch Hydrolyse von Titansulfatlösung, verlaufen Trocknung, Dehydratation, Desulfurisation und eine Anatas — Rutil Umwandlung. Die Untersuchungen wurden unter Anwendung von DTA, TG und DTG durchgeführt. Zur Unterscheidung der einzelnen Effekte wurden feuchte, bis zur Massekonstantheit getrocknete als auch entschwefelte Proben verwendet.

     

Intrinsic kinetics of the oxidation of Na2TiF6 and Na3TiF6

The intrinsic kinetics, unaffected by diffusional and mass transfer effects, of the air oxidation of Na₂TiF₆ and Na₃TiF₆ were determined by using a nonisothermal technique. The oxidation of these sodium fluorotitanates proceeds through two-step reactions involving the formation of oxyfluorotitanate, i.e. Na₃TiOF₅, as the intermediate. The oxidation rate shows a first-order dependence on the amount of the unreacted solids for each of the two-step reactions for both fluorotitanates. The activation energy for the further oxidation of Na₃TiOF₅ to a mixture of NaF + TiO₂ was determined to be 52.4 kJ/mol and 55.3 kJ/raol for Na₂TiF₆ and Na₃TiF₆ as reactants, respectively.     

Study of kinetics of reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw materials with sulphuric acid has been studied in a non-isothermal-non-adiabatic type calorimeter. The influence of different starting conditions, temperature and ilmenite particle-size distribution on the thermo-kinetics of the reaction was investigated. A kinetic model is presented for this heterogeneous system for a specified ilmenite particle-size distribution and starting temperature. On the basis of this model and experimentally determined parameters it it possible to analyse by simulation the autothermic reaction of digestion of different titanium ores with sulphuric acid.     

Kinetics of Thermal Transformations of Precipitated Magnetite and Goethite

The aim of the present study was to determine the kinetic equations for the thermal transformations of precipitated iron oxides and hydroxides, namely for the process of thermal dehydroxylation of goethite and consecutive of hematite crystal structure growth as well as for the oxidation of magnetite to maghemite and its thermal transformation into crystalline hematite. The investigations have been carried out using thermogravimetry (TG/DTG/DTA), X-ray powder diffractometry (XRD) and high temperature powder diffractometry (HT-XRD). This presentation contains the continuation of our earlier works. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal transformations of titanium slag of high titania content

Titanium raw materials play important role as a source of titanium and titanium dioxide. The investigation of the rate of oxidation and phase transformation of titanium slag in static air atmosphere by use of thermogravimetry (TG) and X-ray diffractometry (XRD) were presented. The investigation were carried out for three different particle size fractions to determine influence of this parameter on rate of reaction. To estimate kinetic parameters was used the kinetic model of contracting volume. The value of kinetic parameters show that influence of heating rate and particle size on rate of reaction is not so large. The thermogravimetric investigations of the oxidation of titanium slag in air atmosphere shown that reaction proceeds in two stages. The XRD investigation shown that titanium slag has the pseudobrookite structure and its diffraction pattern is very close to the diffractogram of magnesium titanate MgTi₂O₅ and iron magnesium titanium oxide (Fe-Mg-Ti-O). At elevated temperature the structure of slag transforms to the ferric pseudobrookite structure and excess titanium dioxide forms the rutile phase. This revised version was published online in July 2006 with corrections to the Cover Date.