THERMAL BEHAVIOR OF THE METACAOLINE-BASED MIXTURE FOR THE SYNTHESIS OF LEA ZEOLITE: THE INFLUENCE OF ULTRASONIC TREATMENT

1970 ◽  
Author(s):  
A.P. Khramtsova ◽  
V. Yu. Prokofev ◽  
N.E. Gordina ◽  
D.S. Cherednikova ◽  
E.M. Konstantinova
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Ultrasonic Treatment ◽  
Solid Phase ◽  
X Ray ◽  
Sodium Aluminosilicate ◽  
Temperature Ranges ◽  
Pre Treatment ◽  
Increasing Temperature ◽  
Ray Patterns

A study of the influence of ultrasonic treatment on the kinetics of solid-phase interaction of metakaolin with the sodium hydroxide was performed.Reflections corresponding to the zeolite LTA were observed on X-ray patterns according to phase analysis before calcination at 500°C for the sample without pre-treatment.The appearance of a new phase of sodium alumosilicate (Na6Al4Si4O17) was observed with increasing temperature to 700°C.The reflections of sodium aluminosilicate (Na8Al4Si4O18) and nepheline were detected on the X-ray pattern when the temperature calcination 800°C besides to the characteristic reflections of the zeolite.Aluminosilicates were obtained by recrystallization of the zeolitepart.Also the process was accompanied by metakaolin decomposition in silica and mullite. Reflections corresponding to the zeolite was not discovered at 900°C.According to the X-ray analysis, it was found that ultrasonic treatment has no effect on the phase composition of the samples.Based on these data, it was determined the temperature range (500-800°C).There was recrystallization of zeolite in aluminosilicates for this temperature range.According to the thermal analysis, especially the data of mass loss in a given temperature interval, the exact temperature ranges were established for each heating rate of the samples without pre-treatment and the samples after ultrasonic treatment. The Ozawa-Flynn-Wall method was selected as an isoconversional analysis.The monotonous growth of apparent activation energy was found in all range of conversion extents after ultrasonic treatment. It smoothes the change of the transition regime (up to 200 kJ/mol) to kinetic one.The apparent activation energy for the sample without ultrasonic treatment gone approximately at one level (350 kJ/mol) upon reaching the conversion extent of 0.5-0.6.The apparent activation energy increases after ultrasonic treatment from 350 to 450 kJ/mol upon reaching the conversion extent above 0.9.

scholarly journals THERMAL BEHAVIOR OF MIXTURE BASED ON METAKAOLIN FOR LTA ZEOLITE SYNTHE-SIS: EFFECT OF ULTRASONIC TREATMENT

2019 ◽  
Vol 62 (2) ◽  
pp. 65-71
Author(s):  
Aleksandra P. Khramtsova ◽  
Valery Yu. Prokof’ev ◽  
Natalya E. Gordina ◽  
Darya S. Cherednikova ◽  
Ekaterina M. Konstantinova
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Ultrasonic Treatment ◽  
Solid Phase ◽  
Conversion Degree ◽  
X Ray ◽  
Temperature Range ◽  
Sodium Aluminosilicate ◽  
Lta Zeolite ◽  
Pre Treatment

A study of the influence of ultrasonic treatment on the kinetics of solid-phase interaction of metakaolin with the sodium hydroxide was performed. Reflections corresponding to the zeolite LTA were observed on X-ray patterns according to phase analysis before calcination at 500 °C for the sample without pre-treatment. The appearance of a new phase of sodium alumosilicate (Na6Al4Si4O17) was observed with increasing temperature to 700 °C. The reflections of sodium aluminosilicate (Na8Al4Si4O18) and nepheline were detected on the X-ray pattern when the temperature calcination 800 °C besides to the characteristic reflections of the zeolite. Aluminosilicates were obtained by recrystallization of the zeolite partisles. Also the process was accompanied by metakaolin decomposition in silica and mullite. Reflections corresponding to the zeolite was not discovered at 900 °C. According to the X-ray analysis, it was found that ultrasonic treatment has no effect on the phase composition of the samples. Based on these data, it was determined the temperature range (500-800 °C). There was recrystallization of zeolite in aluminosilicates for this temperature range. According to the thermal analysis, especially the data of mass loss in a given temperature interval, the exact temperature ranges were established for each heating rate of the samples without pre-treatment and the samples after ultrasonic treatment. The Ozawa-Flynn-Wall method was selected as an isoconversional analysis. The monotonous growth of apparent activation energy was found in all range of conversion degrees after ultrasonic treatment. This allows smoothing the change in the transitional regime (up to 200 kJ / mol) to kinetic one. The apparent activation energy for the sample without ultrasonic treatment gone approximately at one level (350 kJ/mol) upon reaching the conversion degree of 0.5-0.6. The apparent activation energy increases after ultrasonic treatment from 350 to 450 kJ/mol upon reaching the conversion degree above 0.9.

scholarly journals Kinetics of carbothermic reduction of synthetic chromite

2014 ◽  
Vol 50 (1) ◽  
pp. 15-21 ◽  
Author(s):  
Y. Wang ◽  
L. Wang ◽  
J. Yu ◽  
K.C. Chou
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reduction Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chromite Ore ◽  
Current Reduction ◽  
Increasing Temperature ◽  
Isothermal Mode ◽  
Kinetics Of

In order to optimize the current reduction process of chromite, a good knowledge of reduction mechanism involved is required. The basic component in chromite ore is FeCr2O4, thus, kinetic investigation of synthetic FeCr2O4 with different amount of carbon were carried out in the temperature range of 1473K to 1673K under both isothermal and non-isothermal mode. The iron can be easily reduced compared with chromium. And higher reduction degree of chromite can be achieved by increasing temperature and carbon content. With the supporting of X-ray Diffraction and Scanning Electron Microscope methods, the formation of metallic products followed the sequence: Fe-C alloy, (Fe,Cr)7C3and Fe-Cr-C alloy. Kinetics analysis showed that the first stage was controlled by nucleation with an apparent activation energy of 120kJ/mol, while the chromium reduction was controlled by crystallochemical transformation with an apparent activation energy of 288kJ/mol.

Synthesis and Ionic Conductivity of MAlSi3O8 (M = Li, Na, K)

2018 ◽  
Vol 790 ◽  
pp. 9-14
Author(s):  
Shin Ichi Furusawa ◽  
Yohei Minami
Keyword(s):  
Activation Energy ◽  
Ionic Conductivity ◽  
Ionic Radius ◽  
Ionic Conduction ◽  
Solid Phase ◽  
Solid Phase Reaction ◽  
Phase Reaction ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray

MAlSi3O8 (M = Li, Na, K) was synthesized by solid-phase reaction at 1000 °C using M2CO3 (M = Li, Na, K), Al2O3, and SiO2 as the starting materials, and its ionic conduction was studied in the temperature range 475–800 K. It was confirmed from powder X-ray diffraction profiles that the crystalline phases of the prepared MAlSi3O8 were the same as those of orthoclase. Moreover, the ionic conductivity of NaAlSi3O8 was about 10 times higher than that of LiAlSi3O8 and KAlSi3O8. The activation energies for ionic conduction were estimated to be in the range of 0.70–0.77 eV, with NaAlSi3O8 exhibiting the lowest activation energy. The result suggests that the magnitude of the activation energy cannot be determined only from the ionic radius.

Apparent Activation Energy in Low Temperature Aging of Y-TZP Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 100-103
Author(s):  
Qi Fei Xie ◽  
Cheng Wang ◽  
Qing Feng Zan ◽  
Li Min Dong
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Apparent Activation Energy ◽  
Coordinate Systems ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Temperature Aging ◽  
Diffraction Patterns ◽  
Straight Lines ◽  
Temperature Aging

Apparent activation energy in low temperature aging of two kinds of Y-TZP ceramic was studied in this paper. The ceramics were processed into small pieces, and aging in 100°C, 110°C, 120°C, 130°C and 140°C respectively. The content of monoclinic phase was calculated by X-ray diffraction patterns and the microstructure was scanned by SEM. According to MAJ law and Arrhenius formation, straight lines were fitted in coordinate systems of ln (ln (1/(1 − f )))-ln t and ln b-1/T, and the kinetic parameters of low temperature aging of Y-TZP ceramic were calculated according to these lines. The results revealed that grain size significantly affected apparent activation energy of Y-TZP ceramics.

Effects of Reaction Temperature on Hydrocracking of Asphaltene over NiMo/γ-Al2O3

2011 ◽  
Vol 393-395 ◽  
pp. 1189-1192
Author(s):  
Ying Xian Zhao ◽  
Bo Shen
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Molecular Weight ◽  
Kinetic Equation ◽  
Apparent Activation Energy ◽  
Average Molecular Weight ◽  
Liquid Product ◽  
Order Kinetic ◽  
Increasing Temperature ◽  
Order Kinetic Equation

The hydrocracking of a pentane-insoluble asphaltene over NiMo/γ-Al2O3 at 623 - 703 K was investigated. The second order kinetic equation fits experimental data of asphaltene conversion adequately, giving the apparent activation energy to be 144 kJ/mol over the temperature range. Average molecular weight of liquid product was reduced significantly with increasing temperature.

scholarly journals Synthesis and catalytic properties of nickel (II) - copper (II) ferrite

2021 ◽  
Vol 247 ◽  
pp. 01020
Author(s):  
Nina Shabelskaya ◽  
Asatullo Radzhabov ◽  
Vitalii Taranushich ◽  
Victor Chernyshev ◽  
Vasilii Demyan ◽  
...  
Keyword(s):  
Activation Energy ◽  
Industrial Wastewater ◽  
Single Phase ◽  
Catalytic Properties ◽  
Organic Dyes ◽  
X Ray ◽  
Production Cycles ◽  
Phase Spinel ◽  
Bet Technique ◽  
Increasing Temperature

This work studies the process of formation of the spinel structure of nickel (II) -copper (II) ferrite. A possible mechanism for the formation of single-phase spinel samples is considered. It consists of the stage of formation of chelate complexes of nickel (II), copper (II), iron (III) cations with citric acid and their subsequent thermal decomposition. The materials obtained are studied by X-ray phase analysis and the BET technique. The catalytic activity of the synthesized ferrite Cu0.5Ni0.5Fe2O4 in the process of oxidative destruction of methyl orange in the presence of hydrogen peroxide is established. It is shown that the process is significantly accelerated with increasing temperature. The activation energy of the reaction was computed. It was found that the activation energy decreases in the presence of a catalyst. The results can be used to obtain materials suitable for industrial wastewater treatment using organic dyes in production cycles.

The 18-crown-6.2 chloroacetonitrile complex. X-ray crystal structure and solid phase motions of guest and host as studied by variable temperature 13C CPMAS NMR spectroscopy

1992 ◽  
Vol 70 (4) ◽  
pp. 1033-1041 ◽  
Author(s):  
G. W. Buchanan ◽  
A. Rodrigue ◽  
C. Bensimon ◽  
C. I. Ratcliffe
Keyword(s):  
Activation Energy ◽  
Correlation Time ◽  
Molecular Motion ◽  
Solid Phase ◽  
Variable Temperature ◽  
13C Cpmas Nmr ◽  
X Ray ◽  
Guest Species ◽  
Motional Correlation Time ◽  
13C Cpmas Nmr Spectroscopy

The title complex has two distinct 18-crown-6 moieties of approximate D3d symmetry in the unit cell. The 45.3 MHz 13C CPMAS spectra have two regions of broadening for the crown ether carbons. At high temperatures a dipolar washout mechanism is operative, leading to broadening when molecular motion has a correlation time approximately equal to the inverse of the decoupling field. At lower temperatures broadening occurs when the motional correlation time is equal to the inverse of the chemical shift difference. The activation energy for 18-crown-6 reorientation in this solid is calculated to be ca. 48 kJ/mol. For the chloroacetonitrile, the CH2 carbon also shows dipolar washout, but at a temperature much lower than the 18-crown-6. The activation energy for reorientation for this "guest species" is ca. 42 kJ/mol.

Preparation and Properties of Rectorite/Epoxy Nanocomposites

2014 ◽  
Vol 875-877 ◽  
pp. 145-149
Author(s):  
Ting Ting Zeng ◽  
Lai Chen ◽  
Da Peng Li ◽  
Jin Liang Sun ◽  
Ze Zhou ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Organic Cation ◽  
Epoxy Composites ◽  
X Ray Diffraction ◽  
Epoxy Nanocomposites ◽  
X Ray ◽  
Working Temperature ◽  
Curing Agents ◽  
Exchange Agent

The Org-rectorite, which was used as a filler in the Rectorite/Epoxy nanocomposites, was prepared by the intercalation and exfoliation of rectorite with dodecyl-bis (2-hydroxyethyl)-methylazanium chloride as the organic cation exchange agent. The two curing agents methyl hexahydrophthalic anhydride (MHHPA) and m-phenylenediamine were employed at working temperature ranging from 70 °C to 190 °C. The samples were characterized by Fourier Transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The results show that the d001 (55.9 Å) of Rectorite/Epoxy composites cured with MHHPA at 70 °C was larger than the Org-rectorite (28.7 Å), and the Org-rectorite was exfoliated at 90 °C working temperature. While the d001 of Rectorite/Epoxy composites cured with m-phenylenediamine at 70 °C and 90 °C were 40.9 Å and 42.1 Å , and were exfoliated at 140 °C. The apparent activation energy (Ea) of Rectorite/Epoxy composites cured with MHHPA and m-phenylenediamine were obtained to be 74.85 and 59.15 KJ/mol, respectively. The higher apparent activation energy (Ea) of MHHPA systems may be responsible for the lower exfoliation temperature.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

Impact of Rutile Fraction on TiO2 Visible-Light Absorption and Visible-Light-Induced Photocatalytic Activity

2018 ◽  
Author(s):  
David Maria Tobaldi ◽  
Luc Lajaunie ◽  
ana caetano ◽  
nejc rozman ◽  
Maria Paula Seabra ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Light Absorption ◽  
Solid Phase ◽  
Diffraction Method ◽  
Band Alignment ◽  
Quantitative Phase Analysis ◽  
Transmission Microscopy ◽  
Visible Light Absorption ◽  
X Ray

<div>Titanium dioxide is by far the most utilised semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile−anatase mixture would improve its visible-light absorption.</div><div>In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2. </div><div>The structural characterisation was done via advanced X-ray diffraction method, namely the Rietveld-RIR method, to attain a full quantitative phase analysis of the specimens. The microstructure was also investigated via an advanced X-ray method, the whole powder pattern modelling. These methods were validated combining advanced aberration-corrected scanning transmission microscopy and high-resolution electron energy-loss spectroscopy. The photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range.</div><div>Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light?</div><div>We tried to give a reply to that question.</div><div>Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-induced catalytic activity (i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects). That is: not photocatalysis <i>sensu-strictu</i>.</div><div>On the other hand, the gas-solid phase results showed that a higher amount of the rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for an actual photocatalytic oxidation of isopropanol.</div>

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