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1.
T. Kaljuvee M. Toom A. Trikkel R. Kuusik 《Journal of Thermal Analysis and Calorimetry》2007,88(1):51-58
The extensive use of fossil fuels in energy production causes serious
pollution of atmosphere with SO2, CO2,
NOx, etc. In Estonia the electricity production is
based mainly on the pulverized firing (PF) of low-grade local fuel –
Estonian oil shale (EOS) which is characterized by a low calorific value (~9
MJ kg–1) and a high content of mineral matter
(65–70%) from which approximately 50% are carbonates. Since 2004, also
two boilers based on circulating fluidized bed combustion (CFBC) of EOS are
in exploitation.
The present study is focused on the comparative
investigation of the efficiency of different ashes collected from different
technological points of CFB and PF boilers as sorbents for SO2.
The influence of experimental temperature on the SO2-binding
characteristics of ashes as well as the possibilities of activation of ashes
(grinding, hydration) were investigated. It was shown that the SO2-binding
capacity of initial ashes at 700°C and p(SO2)=190
mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO2
per 100 mg sample, the best binding capacities belonging to economizer ash
(ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively.
However, during initial stage of binding the best results were obtained with
air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved
the SO2-binding ability, being the most effective in
the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF –
increase in binding capacity 2 and 2.3 times, respectively. As compared to
initial CFBC ashes, the binding characteristics of PF ashes remained lower
even after grinding. Hydration and previous calcination improved the binding
characteristics only of PF ashes. Hereby, the SO2-binding
ability of CFBC ashes is better than of PF ashes and they are more promising
sorbents for acidic gases, for example, for sulphur dioxide. 相似文献
2.
A. N. Mansurova R. I. Gulyaeva V. M. Chumarev V. P. Mar’evich 《Journal of Thermal Analysis and Calorimetry》2010,101(1):45-47
Homogeneous manganocolumbite (MnNb2O6) was synthesized from Nb2O5 and MnO oxides. Powder sample was orthorhombic with unit cell parameters: α = 0.5766 nm, b = 1.4439 nm, c = 0.5085 nm and V = 0.4234 nm3. Heat capacity over the temperature range of 313–1253 K was measured in an inert atmosphere with combined thermogravimetry
and calorimetry using NETZSCH STA 449C Jupiter thermoanalyzer. Melting point was 1767 ± 3 K, enthalpy of melting was 144 ± 4 kJ mol−1. Experimental heat capacity of MnNb2O6 is fitted to polynomial C
pm = 221.46 + 3.03 · 10−3 T + −39.79 · 105 T
−2 + 40.59 · 10−6 T
2. 相似文献
3.
The assumption that potassium permanganate may serve as a kinetics standard in solid decomposition kinetics made a priori
on the basis of the mechanism of the congruent dissociative vaporization of KMnO4 and its crystal structure was successfully supported experimentally. As expected, the decomposition rate of KMnO4 does not depend on the kind of foreign gas (He, air, CO2 and Ar) and on the measurement technique (isothermal or dynamic). Other requirements for KMnO4 as an ideal kinetics standard are satisfied as well. The use of the third-law method for determining the molar enthalpy of
a reaction
( \Updelta\textr H\textT\texto / n ) \left( {\Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu } \right) provides an excellent reproducibility of results. The mean value of
\Updelta\textr H\textT\texto / n \Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu from 12 experiments in different gases is 138.3 ± 0.6 kJ mol−1, which coincides with the value of 138.1 kJ mol−1 calculated from the isothermal measurements in different gases by the second-law method. As predicted by theory, the random
errors of the second-law and Arrhenius plot methods are 10–20 times greater. In addition, the use of these methods in the
case of dynamic measurements is related to large systematic errors caused by an inaccurate selection of the geometrical (contraction)
model. The third-law method is practically free of these errors. 相似文献
4.
Yingjie Li Rongyue Sun Jianli Zhao Kuihua Han Chunmei Lu 《Journal of Thermal Analysis and Calorimetry》2012,107(1):241-248
The calcination characteristics, sulfation conversion, and sulfation kinetics of a white mud from paper manufacture at fluidized
bed combustion temperatures were investigated in a thermogravimetric analyzer. Also, the comparison between the white mud
and the limestone in sulfation behavior and microstructure was made. Although the white mud and the limestone both contain
lots of CaCO3, they are different in the alkali metal ions content and microstructure. It results in a marked difference in sulfation behavior
between the white mud and the limestone. The CaO derived from white mud achieves the maximum sulfation conversion of 83% at
about 940 °C which is 1.7 times higher than that derived from limestone at about 880 °C. The shrinking unreacted core model
is appropriate to analyze the sulfation kinetics of the white mud. The chemical reaction activation energy E
a and the activation energy for product layer diffusion E
p for the sulfation of the white mud are 44.94 and 55.61 kJ mol−1, respectively. E
p for the limestone is 2.8 times greater than that for the white mud. The calcined white mud possesses higher surface area
than the calcined limestone. Moreover, the calcined white mud has more abundant pores in 4–24 nm range which is almost optimum
pore size for sulfation. It indicates that the microstructure of the white mud is beneficial for SO2 removal. 相似文献
5.
S. K. Tripathi Balbir Singh Patial Nagesh Thakur 《Journal of Thermal Analysis and Calorimetry》2012,107(1):31-38
Differential scanning calorimetry data at different heating rates (5, 10, 15 and 20 °C min−1) of Se70Te15In15 chalcogenide glass is reported and discussed. The crystallization mechanism is explained in terms of recent analyses developed
for use under non-isothermal conditions. The value of Avrami exponent (n) indicates that the glassy Se70Te15In15 alloy has three-dimensional growth. The average values of the activation energy for glass transition, E
g, and crystallization process, E
c, are (154.16 ± 4.1) kJ mol−1 and (98.81 ± 18.1) kJ mol−1, respectively. The ease of glass formation has also been studied. The reduced glass transition temperature (T
rg), Hruby’ parameter (K
gl) and fragility index (F
i) indicate that the prepared glass is obtained from a strong glass forming liquid. 相似文献
6.
The poly(o-anisidine)–sulfuric acid–glucose oxidase (POA–H2SO4–GOx) electrode has been investigated in the present work. Platinum electrode was used for the synthesis of poly (o-anisidine)–sulfuric acid (POA–H2SO4) film using galvanostatic method with 0.2 M o-anisidine, 1.0 M H2SO4 solution, 1.0 pH and 2 mA/cm2 applied current density. The synthesized film was characterized using electrochemical technique, conductivity measurement,
UV–visible spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. GOX was immobilized on synthesized POA–H2SO4 film by cross-linking via glutaraldehyde in phosphate and acetate buffer. The Michaelis–Menten constant (
K\textm¢K_{\text{m}}^\prime ) was determined for the immobilized enzyme. The glucose oxidase electrode shows the maximum current response at pH 5.5 and
potential 0.6 V. The sensitivity of POA–H2SO4–GOX electrode in phosphate and acetate buffer has been recorded. The results of this study reveal that the phosphate buffer gives
fast response as compared to acetate buffer in amperometric measurements. 相似文献
7.
The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory,
the molar enthalpy of solution of the title compound at infinite dilution was calculated to be DsolHm¥ = 14.34 kJ·mol-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters bMX(0)L, bMX(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and CMXfLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies (
φ
L) and relative partial molar enthalpies of the compound ([`(L)]2)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the
cation C5H7N2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be DfHmo(C5H7N2+,aq)=-(2.096±0.801) kJ·mol-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}. 相似文献
8.
Quantum-chemical calculations of the geometry and energies of nine possible isomers of 12-vertex cobaltacarborane CpCoC2B9H11 (1) were carried out by the DFT method (PBEPBE/DGDZVP/DGA1). Thermodynamic stability of the isomers increases with increasing
distance between the carbon atoms in the cage and is virtually independent of the position of the CpCo vertex. The relative
stabilities of the 1,2,3-(17.57 kcal mol−1), 1,2,4-(3.72 kcal mol−1), and 1,2,9-isomers of 1 (0 kcal mol−1) are similar to the corresponding values for the ortho (17.61 kcal mol−1), meta (3.21 kcal mol−1), and para isomers (0 kcal mol−1) of carborane C2B10H12. The results of the present study confirm a close similarity of the CpCo and BH fragments in metallacarborane chemistry.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1557–1559, July, 2005. 相似文献
9.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
10.
Mohammad T. Baei Ali Reza Soltani Ali Varasteh Moradi Masoumeh Moghimi 《Monatshefte für Chemie / Chemical Monthly》2011,21(6):573-578
Abstract
The behavior of N2O adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the N2O interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the N2O are calculated to be in the range 4–21 kJ mol−1. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of N2O adsorption on the electronic properties of the nanotubes. 相似文献11.
Chemisorption of SO2 and O2 on the In2O3 surface containing a zinc additive (0.4–2.7 at.%) was studied in a temperature range of 22–200 °C. At least three forms of
sorbed SO2 exist on the modified In2O3 surface. The temperature affects the contribution of single forms of SO2 sorption and, hence, the change in the electric conductivity. The preliminary sorption of O2 favors the formation of a donor form of chemisorbed SO2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2228–2232, October, 2005. 相似文献
12.
At present, carbon dioxide is considered the largest contributor among greenhouse gases. This review covers the current state
of problem of carbon dioxide emissions from industrial and combustion processes, the principle of photocatalysis, existing
literature related to photocatalytic CO2 reduction over TiO2 based catalysts and the effects of important parameters on the process performance including light wavelength and intensity,
type of reductant, metal-modified surface, temperature and pressure.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
13.
Thin nylon-SiO2 membranes made by sol–gel SiO2 coating of a nylon weaving were impregnated in a second step with an aqueous carbonic anhydrase solution. The biocatalytic
hybrid membranes obtained were applied to the capture of CO2 from a N2–CO2 gas mixture containing 10% CO2, under a total pressure ≈ 1 atm. The CO2 permeance of these membranes was at least similar to those previously reported for liquid membranes. When impregnated with
a 0.2 mg mL−1 enzyme solution in a pH ≈ 8 NaHCO3 buffer, the permeance of a nylon-SiO2 membrane was multiplied by a factor ≈ 3 when the buffer molarity was increased from 0.1 to 1 M. By comparison, this permeance
only increased by a factor ≈ 1.3 without any enzyme in the same buffers. The permeance was also higher with the enzyme than
without it: respectively ≈3.7 10−8 and ≈4.7 10−9 mol
\textm\textmembrane - 2 {\text{m}}_{\text{membrane}}^{{^{ - 2} }} s−1 Pa−1 with and without enzyme, in a 1 M NaHCO3 buffer. A maximum permeance was observed for an enzyme concentration of ≈0.2 mg mL−1, possibly due to a competition between the H+ ions produced from CO2,aq by the enzyme and the H+ captured by the buffer. Besides, when the SiO2–CO2 contact was enhanced by the membrane architecture, SiO2 improved the CO2 permeance. The influence of an in situ CaCO3 deposit was also investigated and it improved the CO2 permeance when no enzyme was added. 相似文献
14.
Sara Goñi Francisca Puertas María Soledad Hernández Marta Palacios Ana Guerrero Jorge S. Dolado Bruno Zanga Fulvio Baroni 《Journal of Thermal Analysis and Calorimetry》2010,102(3):965-973
This research is part of a European project (namely, CODICE project), main objective of which is modelling, at a multi-scale,
the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments
were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium–silicate–hydrate (C–S–H) gel structures during
their hydration. The characterization of those C–S–H gels and matrices will provide experimental parameters for the validation
of the multi-scale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been
used for the determination of the chemical composition of the C–S–H gel together with the degree of hydration and quantitative
evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain
length (MCL) were studied by scanning electron microscopy (SEM) and 29Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C–S–H gels
have a CaO/SiO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H2O/SiO2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C3S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C2S (increase). The MCL values of the C–S–H gels, determined from 29Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods. 相似文献
15.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
16.
Jian-Long Xia Wei-Cheng Xiong Gang Chen Guang-Ao Yu Shan Jin Sheng-Hua Liu 《Transition Metal Chemistry》2009,34(4):389-393
Abstract Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H2O)(NBD)][BF4] (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BF4]2. The reaction of [Cp*Ru(H2O)(NBD)][BF4] with 1,4-diphenylbutadiyne generates the unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C9H8–Ph in addition to the organometallic compound [Cp*Ru(η6-C6H5–C≡C–C≡C–Ph)][BF4]. [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BPh4]2 is generated after the reaction of compound [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BF4]2 with Na[BPh4]. The structure of this compound was confirmed by X-ray diffraction. A possible approach to form Ph–C≡C–C9H8–Ph and [Cp*Ru(η6-C6H5–C≡C–C≡C–Ph)][BF4] is suggested.
Graphical Abstract Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H2O)(NBD)]BF4 (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BF4]2. The reaction of [Cp*Ru(H2O)(NBD)][BF4] with 1,4-diphenylbutadiyne simply generates unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C9H8–Ph in addition to the organometallic compound [Cp*Ru(η6-C6H5–C≡C–C≡C–Ph)][BF4]. [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BPh4]2 is generated after the reaction of compound [C9H9-η6-C6H4(RuCp*)–C6H4(RuCp*)-η6-C9H9][BF4]2 with Na[BPh4]. The structure of this compound was confirmed by X-ray diffraction. And the possible approach to form Ph–C≡C–C9H8–Ph and [Cp*Ru(η6-C6H5–C≡C–C≡C–Ph)][BF4] was suggested.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
E. I. Sal’nikova D. I. Kaliev P. O. Andreev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(12):2121-2125
The sequence of phases occurring during treatment of lanthanum sulfate, La2(SO4)3 and lanthanum oxysulfate, La2O2SO4 in a hydrogen flow is established. The temperature ranges in which homogeneous La2O2S is produced are revealed: when La2(SO4)3 is a precursor, the range is 770–1220 K; in the case of La2O2SO4, the interval is 950–1220 K. The kinetic curves showing the time dependence of the yield of La2O2S is constructed and treated using the Avrami-Erofeev and contracting volume equations. The activation energies of the reactions
are determined. 相似文献
18.
Aleksandra Yu. Tarasova Yu. V. Seryotkin V. M. Pashkov Ludmila I. Isaenko 《Journal of Thermal Analysis and Calorimetry》2011,104(2):795-796
The temperature dependence of unit cell parameters for monoclinic KPb2Cl5 and tetragonal RbPb2Br5 crystals was studied in the range of 100–298 K. Linear and volume thermal expansion coefficients were determined. 相似文献
19.
I. A. Sokolov I. V. Murin V. E. Kriyt A. A. Pronkin 《Russian Journal of Electrochemistry》2011,47(4):410-415
The influence of the SO42− ion on the temperature and concentration dependences of electric conductivity and the structure of sodium phosphate oxide
glasses was studied. The increased electric conductivity of sulfate-phosphate glasses was explained by the formation of mixed
sulfate-phosphate fragments with terminal SO42− ions in the structure of glasses in the Na2SO4-NaPO3 system. The dissociation energies of the sodium sulfate fragments are lower than those of pure oxide sodium phosphate structural
units. As a result, the number of dissociated sodium ions increases, the activation energy of electric conductivity falls,
and the conductivity (at 25°C) increases approximately 270-fold relative to the conductivity of NaPO3. The arrangement of SO42− ions in the structure was evaluated from the IR spectra of the glasses. 相似文献
20.
Summary. Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents
the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics
information on the formation of calcium sulfate phases, including CaSO4-based double salts and solid solutions.
Uncertainties in the solubility diagram CaSO4–H2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization.
Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed
experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions
decrease the transition temperatures in dependence on water activity.
Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason
of which is still unclear. However, crystal morphology has a strong influence.
Gypsum forms solid solutions by incorporating the ions HPO4
2−, HAsO4
2−, SeO4
2−, CrO4
2−, as well as ion combinations Na+(H2PO4)− and Ln3+(PO4)3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases
and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of
gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite
hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline
earth sulfates (esp. Na2SO4, K2SO4, MgSO4, SrSO4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na2SO4–CaSO4 and K2SO4–CaSO4–H2O.
Corresponding author. E-mail: daniela.freyer@chemie.tu-freiberg.de
Received December 17, 2002; accepted January 10, 2003
Published online April 3, 2003 相似文献