Titanyl Oxalate Research Articles

A new and simple method for the preparation of active Ti-? zeolite catalysts

Incorporation of titanium into the framework of zeolite beta was achieved by simply treating Al-β zeolite with an ammonium titanyl oxalate solution followed by air calcinations; the material obtained is a very active catalyst for the epoxidation of olefins.

Effect of atmosphere on decomposition of rare earth oxide-activated barium titanyl oxalate

Abstract The effects of atmosphere on the thermal decomposition of rare earth oxide-activated barium titanyl oxalates were investigated under various oxygen partial pressures. The fact that all of the oxygen partial pressures decrease indicates that oxidation of activated oxalates can occur under a lower oxygen partial pressure because the rare earth oxides behave as catalysts. The oxidation reactions are promoted significantly by the addition of empty (La3+) or half-filled (Gd3+) 4f rare earth oxides during the decomposition processes. The La- and Gd-activated barium titanyl oxalates showed a higher activity in oxidation than the others. The activation energies of oxalate decomposition by the addition of rare earth oxides were also determined.

Synthesis of PLZT powders via a molecularly modified precursor route

A new aqueous metallo-organic precursor, namely, lead lanthanum zirconyl titanyl oxalate (PLZTO) has been developed using complexes of Pb 2+, La 3+, Zr 4+ and Ti 4+ with required stoichiometry. Controlled pyrolysis of the PLZTO precursor at sufficiently low temperatures ( T ≈ 525° C) in air resulted in cubic powders of lead lanthanum zirconate titanate (PLZT). Thermal analysis (DTA/TG/DTG), X-ray diffraction (XRD), micro- and chemical analysis, X-ray fluorescence (XRF) and IR studies were used to characterize the precursor and resulting PLZT powder. The dielectric ( K, tan δ) and ferroelectric ( P s , E C ) properties of the sintered compacts were measured at room temperature.

Preparation of strontium titanate using strontium titanyl oxalate as precursor

The synthesis of strontium titanyl oxalate (STO) from Sr and Ti chlorides and oxalic acid is described. Thermal decomposition of STO was studied by means of TG and DTG and compared to X-ray diffraction measurements. Highly crystalline strontium titanate can be obtained by heating the STO precursor in air at 900°C.

On the deposition of thin TiO2 films from Langmuir Blodgett film precursors. An electron spectroscopy study

X-Ray photoemission and reflection electron energy loss spectroscopies have been used to characterize ultrathin TiO2 films obtained by thermal decomposition of Langmuir Blodgett films of n-octadecyl amine which were used to pick up titanyl oxalate ions from the aqueous subphase. The dielectric function of the film was obtained by a Kramers-Krönig analysis of the electron energy loss spectra, which show features characteristic of TiO2. A detailed Tougaard analysis of the photoemission core level background signal was performed to obtain the composition depth profile of the various elements and make an estimate of the film thickness.

Kinetics and mechanism of the thermal decomposition of barium titanyl oxalate

Thermal analysis of barium titanyl oxalate reveals that the decomposition proceeds through four distinct rate processes. Among them, the decomposition of oxalate occurs in the temperature range 230–350°C, and has been studied by TG and gas pressure measurements, supplemented by IR spectroscopy, electron microscopy and chemical analysis. Oxalate decomposition proceeds differently in vacuum and in flowing gas atmospheres. Analytical results indicate the formation of a complex carbonate together with CO, CO2 and water vapour below 400°C. Schemes for each type of decomposition are proposed and discussed. For decomposition in vacuum, kinetic observations fitted the three-dimensional, diffusion controlled, rate equation for almost the entire α-range (0.028≤α≤0.92). The activation energy is calculated to be3 189±6 kJ mol−1.

Tougaard background deconvolution study of the deposition of Langmuir–Blodgett films of long‐chain hydrocarbon amines with titanyl oxalate ions

AbstractMultilayers of a titanyl oxalate complex with n‐octadecylamine were picked up onto quartz substrates by the Langmuir–Blodgett technique. X‐ray photoemission was used to detect the various species in the film and their relative concentrations. A Tougaard background deconvolution analysis of the photoelectron spectra was performed using the differential inelastic scattering cross‐section determined from reflection electron energy‐loss spectroscopy. By contrast with previous work on layer‐structured arachidate films, this analysis indicated that the various elements in the film were present with homogenous depth distributions. This is consistent with XPS take‐off angle studies and with x‐ray diffraction and electron microscopy studies, which showed the film to be amorphous. The composition of the film was determined to be TiO6.7C49N1.7, in reasonable agreement with the expected composition of TiO9C40N2.

Preparation of Stoichiometric Fine Lead Barium Titanate Powder

Lead barium titanate powder with 0.03–0.15 μm particle sizes was prepared from lead barium titanyl oxalate which was previously prepared by reacting high‐purity ammonium titanyl oxalate with barium and lead acetate. The critical factor in preparing the barium titanyl oxalate was the reaction time. It was necessary to allow 2–4 h to synthesize the oxalate to get a single‐phase barium titanate. The critical factors in preparing the lead titanyl oxalate were pH and the concentration of the solution. It was necessary to adjust the pH to around 0.5 and the concentration to <0.08M. When lead barium titanyl oxalate is prepared, low pH, low concentration, and a long reaction time are necessary.

Effect of Composition and Size of Crystallite on Crystal Phase in Lead Barium Titanate

Lead titanate, barium titanate, and lead barium titanate powders (>99.9% pure), the particle size of which varied from 0.03 to 0.15 μm depending on the calcination temperature and the composition, was prepared from barium lead titanyl oxalate, which was previously prepared by reacting high‐purity ammonium titanyl oxalate with barium and lead acetate. The critical crystallite size of BaTiO3 powder from the cubic to the tetragonal phase is around 1 μm. Pb0.3Ba0.7TiO3 powder with an average size of 0.057 μm showed the tetragonal phase.

Effect of atmosphere on decomposition of gadolinium-activated barium titanyl oxalate

The thermal decomposition of Gd-activated barium titanyl oxalate (BaTiO(C 2O 4) 2-4H 2O) is investigated by using differential thermal analysis in air and N 2 under various O 2 partial pressures. As a result, it indicates that the decomposition temperature is reduced with the addition of Gd +3. The Gd-added precipitated oxalate decomposition allows the reaction to occur at a lower O 2 partial pressure than that of the precipitated oxalate decomposition with no addition of Gd +3.

Preparation, characterization and photoreactivity of titanium(IV) oxide encapsulated in zeolites

The preparation, characterization and photoreactivity of titanium(IV) oxide encapsulated inside either sodium- or ammonium-exchanged zeolite Y (NaY and NH4Y), mordenite (NaM and NH4M) or potassium zeolite L (KL) are presented. The material was prepared by an ion-exchange method with ammonium titanyl oxalate monohydrate aqueous solution, (NH4)2TiO(C2O4)2·H2O. The results of X-ray photoelectron spectroscopy, chemical analysis and photolysis studies support the contention that the exchanged titanium species locate dominantly inside the zeolite cavities, and not on the external surfaces. The TiO2+-exchanged zeolite exhibits characteristics of TiO2, such as photoreduction of methyl viologen to methyl viologen radical cation. A significant blue shift of the UV–VIS reflectance spectrum (onset ca. 330 nm), compared with those of bulk anatase and rutile TiO2, and a lack of an X-ray diffraction pattern of TiO2 in the TiO2–zeolite samples indicate that the particle size of the TiO2 encapsulated inside the zeolite is on the nanometre scale.

Synthesis and crystal structure of barium titanyl oxalate, BaTi(O)(C2O4)2.5H2O: a molecular precursor for barium titanate (BaTiO3)

Synthesis and crystal structure of barium titanyl oxalate, BaTi(O)(C2O4)2.5H2O: a molecular precursor for barium titanate (BaTiO3)

Preparation of PbTiO 3 powder through oxalate precipitation route

Pure lead titanyl oxalate (PTO) has been prepared at room temperature from a mixed aqueous solution of Pb(NO 3) 2, TiO(NO 3) 2 and oxalic acid at pH⩽0.45. The TiO(NO 3) 2 solution has been prepared by dissolving Ti(OH) 4 in HNO 3 and stabilized by maintaining the pH at ⩽0.2 and storing at 10–15 °C. Calcination of pure PTO yields PbTiO 3 and a titania-rich phase (PbTi 3O 7) due to volatilization of lead. Pure PbTiO 3 is obtained from a mixture of PTO and PbC 2O 4. Presence of the latter is necessary to compensate for lead loss during calcination. The precipitation of PTO takes place by initial formation of PbC 2O 4 followed by its reaction with titanyl oxalate species.

Low temperature synthesis of ultrafine strontium titanate (SrTiO3) powders

Ultrafine (≍0.4 μm) strontium titanate powder was synthesized using strontium nitrate and potassium titanyl oxalate as precursors. An aqueous (0.1 M) potassium titanyl oxalate solution was added dropwise to a (0.1 M) strontium nitrate solution with continuous stirring at room temperature to precipitate strontium titanyl oxalate (STO). The precipitate, after careful washing with distilled water several times, was air-dried and calcined at 550 °C/6 h to obtain homogeneous, spherical, stoichiometric powder of SrTiO3 ≍0.4 μm in size. The calcined powder was characterized using different techniques such as XRD, DTA/TG/DTG, SEM, and IR.

Occurrence of excess titania in strontium titanate prepared by the oxalate precipitation route

Strontium titanyl oxalate has been prepared by allowing a mixed solution of TiCl 4 and SrCl 2 to react with an aqueous solution of oxalic acid under different experimental conditions. Coprecipitation of hydrous TiO 2 with strontium titanyl oxalate is observed at room temperature due to hydrolysis of Ti(OH) 2 2+ species. Calcination of the dried precipitate results in excess TiO 2 as a second phase in SrTiO 3. However, the hydrolysis of Ti(OH) 2 2+ can be nearly eliminated by either increasing the precipitation temperature or adding excess oxalic acid at room temperature, and thereby forming an additionally quantity of Ti()OH) 2C 2O 4 complex which has less tendency to hydrolyse.

Crystal structure of barium titanyl oxalate BaTiO(C 2O 4) 2 · 4.5H 2O

The hydrated phase of barium titanyl oxalate, BaTiO(C 2O 4) 2 · 4.5H 2O, is monoclinic with a = 13.382(2), b = 13.812(2), c = 14.044(2) Å, β = 91.48(1)°, space group P2 1/ n, Z = 8. The structure has been determined from Patterson and Fourier syntheses. The refinement was done by the method of least-squares. The final R values were R = 0.056 and R w = 0.079 for 3261 unique reflections. The structure is characterized by a body-centered arrangement of finite groups consisting of four vertex-sharing TiO 6 distorted octahedra. These groups are connected by barium polyhedra and oxalate groups. The study shows that the water molecule number is 4.5 by formula rather than 4 reported previously. This conclusion is supported by TG measurements.

Preparation, Characterization and Sintering Behaviour of Complex Titanate Powders

AbstractThree methods were used for the preparation of complex barium titanate powders containing Sr, Ca, Mn and La or Pb, Ca and La, respectively: titanyl oxalate route, peroxide route, conventional solid state reaction. The powders are characterized with respect to their analytic and morphologic properties. The isothermal sintering behaviour is studied at 900, 1200, and 1320 °C. Powders prepared by the wet chemical synthesis show an excellent densification with final densities of about 97–98%. Possible sintering mechanisms are discussed.

Thermal Analysis of Precursors of Barium Titanate Prepared by Coprecipitation

Thermal analysis was performed on coprecipitated materials and on individual components. The detailed decomposition schemes of coprecipitates and individual components are proposed and discussed. According to the proposed decomposition schemes, the values of the observed weight loss are in good agreement with those of the theoretical values of the coprecipitated materials and individual components. The results indicate that barium titanyl oxalate is an inserting compound, i.e., a structure of distorted barium hydrogen oxalate hydrate being inserted by Ti(OH)3+. The results also verify that copreciptation of barium and titanium ions in an oxalate aqueous solution at pH 7 is a mixture of BaC2O4· 0.5H2O and TiO(OH)2· 1.5H2O and coprecipitation of barium and titanium ions using the process of Yamamura et al. is a mixture of Ba(NO3)2 and Ti(OH)2C2O4.

Low-temperature synthesis of ultrafine barium titanate (BaTiO 3) using organometallic barium and titanium precursors

Nano size (< 200 nm) barium titanate was synthesized using barium acetate and potassium titanyl oxalate as precursors. Aqueous (0.01 M) potassium titanyl oxalate was added dropwise to a 0.01 M aqueous barium acetate solution with continuous stirring at room temperature to precipitate barium titanyl oxalate (BTO). The precipitate, after careful washing with distilled water several times, was dried in an oven at 70°C and calcined in air at 550°C/6 h to produce spherical, homogeneous, stoichiometric powder of BaTiO 3 < 200 nm in size. The calcined powder was characterized using different techniques such as XRD, DTA/ TG/DTG, SEM/TEM and IR techniques.

Effect of calcination on characteristics, surface texture and sinterability of chemically prepared barium titanate

Highly pure and finely divided barium titanate powders have been obtained by the pyrolysis of barium titanyl oxalate. The effect of time and temperature of calcination on the degree of crystallinity, fineness, and surface texture of the powders obtained have been demonstrated. The densification properties of the sintered bodies are discussed in relation to the characteristics of the calcined materials.