EPR Study of CeO2 Nano Particles

In this paper, we have studied the EPR spectra, X-ray diffraction and Raman Analysis, Microstructures-morphology of the Ceria NPs calcined at different temperatures of 700 °C, 850 °C ,these materials have been synthesized by Co precipitation (CPT) method by using Cerium tri-nitrate hexahydrate and potassium carbonate solutions. Then synthesized precipitate was heated at 70 °C for 20 hour. Slow grinding of the precipitate and calcined for 3 hours at different temperatures viz. 700 °C and 850 °C to form fine Cerium oxide powder-Ceria NPs. The EPR measurements were made using continuous wave spectrometer (X-band, Bruker Biospin EMX Plus). The g values were obtained by using diphynelpirichylhydrageyl (DPPH-C18H12N5O6) sample and got g value is around 1.97. This g tensor is decreased when the calcined temperature are increased, EPR parameters are also changed as the calcined temperature increases. When the calcined temperature is increased from 700 °C to 850 °C, a doublet separated, intensity increased. The X-Ray diffraction pattern shows the nature of the Ceria NPs crystal, with a cubic structure and got the lattice parameters 5.392 Å for samples calcined at temperature of 700 °C and 5.357 Å at 850 °C which shows decreasing trend in lattice parameter with calcination temperature. The intensity of Raman peaks is also shifted upwards with a rise in temperature. This intensity difference could be because of the rise in vibrational amplitudes of the closest neighboring bonds because of the increase in particle size 11.3± 1.0 to 15.6± 1.0 nm at calcination temperatures of 700 °C and 850 °C and the Raman peak of peak I, 461 cm-1 and peak II, 463 cm-1 respectively. Other peaks were not observed in this Raman pattern. The EDS analysis confirms the presence of the Ce and O atoms in the synthesized samples. Spherical shapes and homogeneously distributed Ceria NPs and a rather tendency for agglomeration were confirmed.

High Catalytic Performance and Sustainability of Zr Modified Aluminophosphate for Vapor-Phase Selective O-methylation of Catechol with Methanol

Guaiacol produced by O-methylation of catechol with methanol over solid catalysts is a green environmental synthesis route. In order to achieve high catalytic efficiency, it is quite necessary to employ low-cost catalysts with high activity and stability. Herein, series of aluminophosphate catalysts were synthesized by a simple precipitation route modified by Zr. The characterization results indicated that the prepared Al-P-Zr catalysts possessed appropriate weak acid and weak base sites, which were beneficial for the O-methylation of catechol with methanol. Different Zr amount and calcined temperature exerted a significant influence on physicochemical properties of the catalysts and catalytic performance. The Al-P-Zr catalysts containing Zr/Al molar ratio of 0.012 calcined under 400 °C showed the optimal catalytic activity and long-term stability for vapor-phase selective O-methylation of catechol with methanol.

MoO3 Structures Transition from Nanoflowers to Nanorods and Their Sensing Performances

Morphology transformation and crystal growth strategies of metal oxide semiconductors are extensive studied in material science recently, because the morphology and crystallinity of the nanomaterial have significant effect on the physicochemical characteristics. However, understanding the morphology changes of α-MoO3 induced by annealing temperature is still a challenge. Herein, the nanostructure transition of MoO3 induced by calcined temperature has been investigated through XRD and SEM method. It can be found that crystallization is highly dependent on the annealing temperature. In addition, the MoO3 nanoflowers can change into nanosheets at 500 ºC. Afterwards, the nanosheets turn into microrods, especially at 900 ºC due to the growth of MoO3 crystal. On the other hand, MoO3 is a traditional sensing material, which is sensitive to many volatile organic compounds. Thus, the sensing performances of various MoO3 nanostructures were measured. Compared with MoO3 nanoflowers and microrods. The MoO3 nanosheets based sensor has excellent sensing performance towards ethanol, and the maximum gas response value is 8.06.

Tuneable oxidation of styrene to benzaldehyde and benzoic acid over Co/ZSM-5

Co/ZSM-5 prepared via simple impregnation method was used as catalyst for solvent-free oxidation of styrene with molecular oxygen as oxidant. Co/ZSM-5-500 catalyst prepared at calcined temperature 500 oC demonstrated high...

Effect of La2O3 Derived from Thai Monazite Ore Chemical Processing on the Properties of SO4-1/ZrO2

La2O3 derived from Thai monazite ore chemical processing was used as a precursor to prepare SO4-1-1%La2O3/ZrO2 solid acid catalyst. The SO4-1-1%La/ZrO2 catalyst was synthesized by co-precipitation with subsequent impregnation method. Various characterization techniques such as X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and Fourier transform infrared spectroscopy (FTIR) were used to study crystalline structural, textural and acid properties of the prepared catalysts. XRD results revealed that the presence of stable La2O3/ZrO2 tetragonal phase for SO4-1-1%La2O3/ZrO2 was observed at calcined temperature up to 600 °C. No diffraction peaks of La2O3 appeared in the profile of SO4-1-1%La2O3/ZrO2, indicated that the La2O3 was finely dispersed on the ZrO2 support. The doping of SO4-1-ZrO2 with La2O3 led to a significant decrease in its BET surface area, total pore volume and pore diameter. A relatively uniform pore size distribution of SO4-1-1%La2O3/ZrO2 catalyst with average pore diameter of 6 nm was found at the calcined temperature of 600 °C. Lewis acid sites existed in the synthesized SO4-1-1%La2O3/ZrO2 were lower than that counterpart. A loss of sulfate species was noted at high calcined temperature. The prepared SO4-1-1%La2O3/ZrO2 will be further used as a solid catalyst for transesterification of waste cooking oil to biodiesel, and the addition of La2O3 on the support could lead to enhance the catalytic activity and thermal stability.

Systematic Study of Calcination Temperature on Photocatalytic Activity of Luminescent Copper(I) Pyrazolate Complex/Titanium Oxide Composites

Columnar assembly of luminescent 3,5-dimethyl pyrazolate complexes/titanium oxide composites with different metal ions has shown significant improvement in its photocatalytic activity for the removal and degradation of 2, 4-dichlorophenoxyacetic acid (2,4-D). Since photocatalytic activity of semiconductor titanium oxide (TiO2) with an anatase phase can be improved by calcination temperature, we report the effect of heat treatments on the preparation of copper(I) 3,5-dimethyl pyrazolate complex/titanium oxide composite ([Cu3Pz3]/TiO2) for the removal and degradation of 2,4-D. Photocatalyst composites [Cu3Pz3]/TiO2 were successfully prepared using an impregnation method with different calcination temperature at 373, 473 and 573 K. Although, the activity of photocatalyst composites [Cu3Pz3]/TiO2 was significantly improved with increasing of calcination temperature on pure TiO2, it was slightly reduced with an increase of calcined temperature to 473 and 573 K. These results showed that [Cu3Pz3]/TiO2 was unstable at high temperature due to the decomposition of molecular structure of [Cu3Pz3] during the preparation of the photocatalyst. Hence, suitable calcination temperature is an important parameter to increase photocatalytic activity of photocatalyst composites [Cu3Pz3]/TiO2.

Fabrication and Characterization of ZnO Nanofibers by Electrospinning

ZnO nanofibers were successfully prepared by electrospinning a precursor mixture of polyvinylpyrrolidone (PVP)/zinc acetate, followed by calcination treatment of the electrospun composite nanofibers. The effect of applied voltage to the morphology of nanofibers was studied. Both PVP/Zn acetate and ZnO nanofibers were characterized by FESEM and XRD. The results show that the diameter of the nanofibers changed with applied voltage. Results found that the optimum calcined temperature was 500°C to produce continuous ZnO nanofibers.

Effect of the calcination temperature of cerium–zirconium mixed oxides on the structure and catalytic performance of WO3/CeZrO2 monolithic catalyst for selective catalytic reduction of NOx with NH3

The calcined temperature of the carrier obviously affected SCR activity of catalysts, WO3/Ce0.68Zr0.32O2-500 showed the best low-temperature NH3-SCR activity due to its more Lewis acid sites and stronger redox property.