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1.
2.
Sukhe D. Badmaev Galina G. Volkova Vladimir D. Belyaev Vladimir A. Sobyanin 《Reaction Kinetics and Catalysis Letters》2007,90(1):205-211
The steam reforming of dimethyl ether (DME) (SR) to a hydrogen-rich gas over a mechanical mixture of WOx/ZrO2 (the DME hydration catalyst) and CuZnAlOx (the methanol SR catalyst) was studied. The mechanically mixed catalyst was shown to provide almost complete conversion of
DME to the hydrogen-rich gas containing <0.5 vol.% of CO at 300°C, atmospheric pressure, gas hourly space velocity (GHSV)
of 10000 h−1 and molar ratio H2O/DME = 3. The hydrogen production rate in DME SR was found to reach 180–250 mmol H2/(gcat·h) at 250–300°C. 相似文献
3.
Christoph Luef Aloke Paul Jiri Vizdal Ales Kroupa Alexander Kodentsov Herbert Ipser 《Monatshefte für Chemie / Chemical Monthly》2006,137(4):381-395
Summary. The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique
using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed.
Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well
as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found
at 135°C. 相似文献
4.
Christoph Luef Aloke Paul Jiri Vizdal Ales Kroupa Alexander Kodentsov Herbert Ipser 《Monatshefte für Chemie / Chemical Monthly》2006,36(5):381-395
The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique
using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed.
Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well
as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found
at 135°C. 相似文献
5.
M. Saeed Butt Zareen Akhter M. Zafar-uz-Zaman Humaira Masood Siddiqi 《Colloid and polymer science》2008,286(12):1455-1461
The diamine, 4-aminophenyloxy-N-4-[(4-amiophenyloxy)benzylidene]aniline, was prepared via the nucleophilic substitution reaction and was polymerized with
different dianhydrides either by one-step solution polymerization reaction or two-step procedure. The latter includes ring-opening
polyaddition to give poly(amic acid), followed by cyclodehydration to polyimides. The inherent viscosity ranges from 0.61–0.79 dl/g.
Some of the polymers were soluble in most of the organic solvents such as DMSO, DMF, DMAc, NMP, and m-cresol even at room temperature. The degradation temperature of the resultant polymers falls in the ranges from 240–500 °C
in nitrogen with only 10% weight loss. Specific heat capacity at 200 °C ranges from 1.0929–2.6275 J g−1 k−1. The temperature at which the maximum degradation of the polymer occurs ranges from 600–630 °C. The glass transition temperature
(Tg) values of the polyimides ranged from 185 to 272 °C. The activation energy and enthalpy of the polyimides ranged from
47.5–55.0 kJ/mole and 45.7–53.0 kJ/mole and the moisture absorption in the range of 0.23–0.72%. 相似文献
6.
The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry
and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous Tris/HCl buffer and in aqueous
phosphate buffer in the pH range 7–8 using the enzyme glucose isomerase and the cofactors CoCl2 and MgSO4. The temperature range over which this reaction was investigated was 298.15–358.15 K. We have found that the enthalpy of
reaction is independent of pH over the range investigated. A combined analysis of both the HPLC and microcalorimetric data
leads to the following results at 298 15 K:ΔG° = 349 ± 53 J mol-1, ΔH° = 2.78 ± 0.20 kJ mol-1, and ΔC
p
°
= 76 ± 30 J mol-1 K-1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements.
Comparisons are made with literature data. The percent conversion of glucose to fructose has been calculated for the temperature
range 300–373.15 K. 相似文献
7.
The carborane–siloxane copolymers Dexsil 300, a 34.5% bis(dimethylsilyl)-m-carborane–65.5% dimethylsiloxane copolymer, and Dexsil 400, a 24.9% bis(dimethylsilyl)-m-carborane–50.8% dimethyl, 24.3% methylphenylsiloxane copolymer, were coated on fused silica capillary columns and their gas
chromatographic properties were evaluated. Their selectivity was evaluated using both Rohrschneider–McReynolds constants and
triacylglycerol indices. The bis(dimethylsilyl)-m-carborane unit turned out to be equivalent to two dimethylsiloxy units and one half of a diphenylsiloxy unit. The m-carborane unit was found to cause a 15–25 K shift in the elution temperature between 120 and 360 °C. The working range was
from 20 and 0 °C to 380 °C for Dexsil 300 and Dexsil 400, respectively. The column bleeding levels at 380 °C were below 20
and 15 pA for Dexsil 300 and Dexsil 400, respectively. 相似文献
8.
K. De Buysser I. Van Driessche J. Schaubroeck S. Hoste 《Journal of Sol-Gel Science and Technology》2008,46(2):133-136
A novel sol–gel synthetic route using water-soluble precursor salts is presented as a synthetic path for a high-purity negative
thermal expansion material, ZrW2O8. This synthetic route involves a sol–gel method with the use of EDTA as complexing agent. The aqueous solution is transformed
into a ceramic material after a two-step heat treatment: gelation at 60 °C and reactive sintering at 1,180 °C. The decomposition
of the gel is monitored with infrared spectroscopy and TGA. The high-temperature heat treatment results in ZrW2O8 with its characteristic negative thermal expansion behaviour α[75–130 °C]: −9.8 ± 1.6 μm/m °C and α[175–300 °C]: −1.2 ± 0.2 μm/m °C. 相似文献
9.
T. Kaljuvee M. Radin D. Astahhov Y. Pelovski 《Journal of Thermal Analysis and Calorimetry》2006,84(1):59-66
Coupled
TG-FTIR technique was used for identification of gaseous compounds evolved
at thermal treatment of six coal samples from different deposits (Bulgaria,
Russia, Ukraine). The experiments were carried out under dynamic heating conditions
up to 900°C at heating rates of 5, 10 or 50 K min–1
in a stream of dry air. The emission of CO2, H2O,
CO, SO2, COS, methane, methanol, formic acid, formaldehyde,
acetaldehyde, chlorobenzene was clearly identified in FTIR spectra of the
samples studied. The formation of ethanol, ethane, ethylene and p-xylene, at least on the level of traces, was also
identified. At the heating rate of 5°C min–1
the temperature of maximum intensities of the characteristic peaks of COS
was 270°C, of formaldehyde, formic acid, ethane and methanol 330°C,
of SO2, CO, acetic acid, ethylene and p-xylene
400°C and of chlorobenzene 500°C. At 10°C min–1
and 50°C min–1 these temperatures were
shifted, respectively, by 70–300°C and 150–450°C towards
higher temperatures and the respective absorption bands in FTIR spectra were,
as a rule, more intensive. 相似文献
10.
Differential thermal analysis (DTA) of low-rank coals of high lignite to subbituminous rank from coal mines of Pakistan is
reported. The studies carried out in dynamic oxygen atmosphere indicate that the exothermic reactions occur between 300 and
650°C and that the samples undergo stepwise oxidation of the organic matter rather than a continuous process as indicated
by the pattern of shoulders from 250 to 350°C accompanying the main peak around 450°C. The effect of heating rate, particle
size and volatile content was also studied in relation to oxidation. The results show that the increase in heating rate from
10 to 80 deg min−1 results in a marked shift in all the events in the DTA curve towards higher temperatures. As for the effect of particle size,
the DTA records of 100–75, 150–100, 250–150 μm and greater than 250 μm fractions show that the magnitude and position of shoulder
peaks are more sensitive to changes in particle sizes compared to the main peak. The curves recorded to study the effect of
changing volatile content of samples between 30–40% indicate a complex pattern of shoulders accompanying the main peak. In
general, the number of shoulder peaks increases with increasing volatile content of samples but their positions do not follow
any trend. The DTA curves recorded in nitrogen contain ill-de-fined oxothermic effects over the 300–750°C temperature range.
These curves consist of an endothermic peak around 150°C, two exothermic shoulders in the temperature region 300–400°C and
a large broad exothermic whip between 500 and 700°C. The heating rates have similar effects as in oxygen while the particle
size do not influence the results.
It has been concluded that the organic matter in the coals studied here is extremely heterogeneous with different burning
characteristics; as a result it is very difficult to quantify energy changes associated with poorly resolved exothermic events
along the DTA curve. The effects also dominate in N2 atmosphere thus making identification of mineral matter difficult. The overall pattern of DTA events in oxygen can be correlated
with the heating rate, particle size and volatile content of samples. 相似文献
11.
A. M. L. Silva R. W. C. Li J. R. Matos J. Gruber 《Journal of Thermal Analysis and Calorimetry》2000,59(3):675-680
The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under
very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable
in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g–1) . The activation energy (116±4 kJ mol–1 ) was determined by Ozawa's method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
V. Balek E. R. Vance V. Zeleňák Z. Málek J. Šubrt 《Journal of Thermal Analysis and Calorimetry》2007,88(1):93-98
Emanation thermal
analysis (ETA) was used to characterize the thermal reactivity of amorphous
brannerite mineral of general formula U1–xTi2+xO6
(locality El Cabril, near Cordoba, Spain). It was demonstrated that on sample
heating up to 880°C microstructure changes taking place in the sample
were accompanied by the formation of new radon diffusion paths, followed by
their closing up during the final transformation of amorphous to crystalline
brannerite in the range 900–1020 °C. Relative changes in structure
irregularities that served as radon diffusion paths during heating and subsequent
cooling of the sample to temperatures of 300, 550, 750, 880, 1020 and 1130°C,
respectively, were determined from the ETA results. Mass losses in temperature
ranges of 230–315, 570–760 and 840–1040°C were observed
by thermogravimetry. Mass spectrometry indicated the release of CO2 mainly
due to the decomposition of minor carbon amount in the brannerite mineral
sample. 相似文献
13.
A. V. Davidov S. S. Travnikov B. F. Myasoedov 《Journal of Radioanalytical and Nuclear Chemistry》1973,14(2):285-293
The possibility has been investigated of separating rare-earth fission fragment elements from106Ru and137Cs by high-temperature sublimation (950°C) of chlorides, with their subsequent gas adsorption separation in a quartz tube
under a temperature gradient in a flow of the carrier-gas Ar+SOCl2. The temperature corresponding to the maxima of the element precipitation zones are: 630–660°C (144Ce), 770–780°C (0.7–6 μg140La+La), 920°C (1.5 mg Ce or La), 420–450°C (106Ru), 280–300°C (137Cs). The coefficients of element separation have been calculated. For the separation of indicator amounts of rare-earth elements
and106Ru and137Cs, fractional sublimation of the chlorides of the latter at 650°C has been used. Rate constants and effective activation
energies of the overall processes of chlorination-sublimation of the elements have been determined. 相似文献
14.
Influence of the calcined paper sludge on the development of hydration heat in blended cement mortars 总被引:1,自引:0,他引:1
O. Rodríguez M. Frías Ma I. Sánchez de Rojas 《Journal of Thermal Analysis and Calorimetry》2008,92(3):865-871
The present study is based on the influence of the addition of a pozzolanic material as a result of the activation of an industrial
waste coming from the Spanish paper industry on the heating as well as hydration heat of the cement mortars made with 10 or
20% of active addition.
Once the sludge has been calcined at different temperatures (700–800°C) and stays in furnace (2 and 5 h), the calcined products
showed high pozzolanic activity. The maximum activity corresponded to the paper sludge calcined at 700°C for 2 h (S1). Besides,
it can be proved that there was an increase both of the heating and also of the hydration heat in the first 23–25 h for both
additions (10 and 20% of S1) regarding the reference cement mortar. This behaviour would be related to the influence of different
effects: filler and pozzolanic during the first hours of reaction, and by the dilution effect for longer hydration times,
mainly when 20% of S1 was added. 相似文献
15.
Simultaneous
thermogravimetry (TG) and differential thermal analysis (DTA) techniques were
used for the characterization the thermal degradation of loratadine, ethyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidine)-1-piperidinecarboxylate.
TG analysis revealed that the thermal decomposition occurs in one step in
the 200–400°C range in nitrogen atmosphere. DTA and DSC curves showed
that loratadine melts before the decomposition and the decomposition products
are volatile in nitrogen. In air the decomposition follows very similar profile
up to 300°C, but two exothermic events are observed in the 170–680°C
temperature range.
Flynn–Wall–Ozawa method was used
for the solid-state kinetic analysis of loratadine thermal decomposition.
The calculated activation energy (E
a)
was 91±1 kJ mol–1 for α between
0.02 and 0.2, where the mass loss is mainly due to the decomposition than
to the evaporation of the decomposition products. 相似文献
16.
It has been found that the Cl− and Br− anions change the microstructure of their hydration shells in the temperature range 30–35 °C. The effect was observed for
simple salt solutions and ternary systems with different organic compounds. Probably this effect can be responsible for the
thermoregulation of warm-blooded animals. 相似文献
17.
A. Miyake M. Wakakura T. Uchida A. Ushikubo 《Journal of Thermal Analysis and Calorimetry》2006,85(3):643-649
Cellulose, chitosan and piroxicam were investigated
by TG and DSC at heating up to 215°C, and by X-ray powder diffraction
before and after the heating.
Dehydration of cellulose and chitosan
comes to the end near 160°C. Thermal decomposition of chitosan starts
at the final stage of its dehydration, and the mass losses after these two
reactions overlap with one another. Enthalpy of dehydration is 47.1±2.4
kJ mol–1 of water for cellulose and 46.2±2.0
kJ mol–1 for chitosan. Thermal decomposition
of chitosan is an exothermic process. Crystal structure of cellulose after
heating remains unchanged, but that of chitosan contracts.
Piroxicam
melts at 200.7°C with the enthalpy of melting 35 kJ mol–1.
Heat capacity of the liquid phase is greater than that of the solid phase
by approximately 100 J mol–1K–1.
Cooled back to ambient temperature, piroxicam remains glassy for a long time,
crystallizing slowly back into the starting polymorph. 相似文献
18.
A. S. Rozenberg E. I. Aleksandrova G. I. Dzhardimalieva A. N. Titkov A. D. Pomogailo 《Russian Chemical Bulletin》1993,42(10):1666-1672
The thermal decomposition of iron (III) acrylate, [Fe3O(CH2=CHCOO)6 · 3H2O]OH (FeAcr), a monomer with a complex cluster cation, has been studied at 200–370 °C. Thermal transformations of FeAcr occur
in two temperature regions. The rates of gas evolution in the low temperature region (200–300 °C) and the high temperature
region (300–370 °C) are described by first-order equations withk=4.2 · 1021exp[−59000/(RT)] s−1 andk=1.3 · 106exp[−30500/(RT)] s−1, respectively. A study of the qualitative and quantitative composition of the products of FeAcr thermolysis was carried out.
The thermal transformation of FeAcr is a complex process of dehydration, degradation, and polymerization in the solid phase
followed by decarboxylation of the metal-carboxyl groups of the polymer.
for part 33 see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1743–1750, October, 1993. 相似文献
19.
The characteristics of bioaragonite of shells of recent T. decussatus during heating were studied by the means of TG-DTA-EGA (FTIR), XRD, XRF and FTIR. The mass loss recorded up to 2.5% appeared
with the higher rates at 110–150, 200–250, 295–300, and 390–415°C at heating of 10°C min−1 up to 500°C. IR analysis of the evolved gases revealed the emission of water and CO2. The lattice constants tend to change with anisotropy character (parameters a and c diminish whilst b tends to grows) and with an overall contraction of cell volume (from 227.36 to 226.84 ?3) during heating was established. The peculiarity of bioaragonite was explained by substitution of H2O and sulphate ion into the lattice. In spite of those substitutions, bioaragonite reveals an orthorhombic structure, which
is preserved during the changes up to calcite formation above 380°C. 相似文献
20.
Mojtaba Shamsipur Mohsen Irandoust Kamal Alizadeh Vito Lippolis 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):203-209
Proton NMR was used to study the complexation reaction of Ag+ with octathia-24-crown-8 (OT24C8) in a number of binary dimethylsulfoxide (DMSO)–nitrobenzene (NB) mixtures at different
temperatures. In all cases, the exchange between free and complexed OT24C8 was fast on the NMR time scale and only a single
population average 1H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined
by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability
and the amount of DMSO in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated
from the temperature dependence of formation constants. In all solvent mixtures studied, the resulting complex is enthalpy
stabilized but entropy destabilized. The TΔS° versus ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy
compensation in the complexation reaction. 相似文献