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1.
The data on the thermal decomposition of FeSO4?H2O upon various regimes of heating and gaseous environment prove the formation of intermediate products of the types Fe2O(SO4)2 and FeOHSO4, their stability and amount being determined mainly by temperature and oxygen-reduction potential. This communication aims at presenting results on the synthesis and characterization of Fe2O(SO4)2. The synthesis was carried out using a laboratory thermal equipment operating under isothermal conditions in the temperature range 713–813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe2O(SO4)2 is stable are established. The effect of three basic parameters on the synthesis of Fe2O(SO4)2 is clarified: the oxygen partial pressure, the ratio PH2O/PO2 and the temperature and the mode of heating. Mössbauer spectroscopy and X-ray diffraction data for Fe2O(SO4)2 are presented. 相似文献
2.
The synthesis and thermal decomposition of Na 2(SO 4) 2·2H 2O in both air and nitrogen are described. The synthesis was performed by two different procedures, but in both cases the same product was obtained, corresponding to the general formula given above. The crystals obtained were investigated by methods of X-ray powder diffraction, and chemical and thermal analysis. The differences in thermal decomposition in air and nitrogen are discussed. 相似文献
3.
The thermal decomposition of FeSO 4·6H 2O
was studied by mass spectroscopy coupled with DTA/TG thermal analysis under
inert atmosphere. On the ground of TG measurements, the mechanism of decomposition
of FeSO 4·6H 2O is:
i) three dehydration steps
FeSO 4·6H 2O FeSO 4·4H 2O+2H 2O
FeSO 4·4H 2O FeSO 4·H 2O+3H 2O
FeSO 4·H 2O FeSO4+H 2O
ii) two decomposition
steps
6FeSO 4 Fe 2(SO 4) 3+2Fe 2O 3+2SO 2
Fe 2(SO 4)3 Fe 2O 3+3SO 2+3/2O 2
The intermediate compound was identified as Fe 2(SO 4) 3 and the final product as the hematite Fe 2O 3. 相似文献
4.
The thermal decomposition of tribochemically activated Al 2(SO 4) 3· xH 2O was studied by TG, DTA and EMF methods. For some of the intermediate solids, X-ray diffraction and IR-spectroscopy were applied to learn more about the reaction mechanism. Thermal and EMF studies confirmed that, even after mechanical activation of Al 2(SO 4) 3· xH 2O, Al 2O(SO 4) 2 is formed as an intermediate. Isothermal kinetic experiments demonstrated that the thermochemical sulphurization of inactivated Al 2(SO 4) 3· xH 2O has an activation energy of 102.2 kJ·mol ?1 in the temperature range 850–890 K. The activation energy for activated Al 2(SO 4) 3· xH 2O in the range 850–890 K is 55.0 kJ·mol ?1. The time of thermal decomposition is almost halved when Al 2(SO 4) 3· xH 2O is activated mechanically. The results permit conclusions concerning the efficiency of the tribochemical activation of Al 2(SO 4) 3· xH 2O and the chemical and kinetic mechanisms of the desulphurization process. 相似文献
5.
Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO 4) 2·4H 2O are reported. The first modification, α-Ce(SO 4) 2·4H 2O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO 4) 2·4H 2O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H 2O) 4(SO 4) 2 held together by a hydrogen bonding network. The dehydration of Ce(SO 4) 2·4H 2O is a two step (I) and one step (II) process, respectively, forming Ce(SO 4) 2 in both cases. During the decomposition of the anhydrous form, Ce(SO 4) 2, into the final product CeO 2, intermediate xCeO 2· yCe(SO 4) 2 species are formed. 相似文献
6.
Fully acetylated saccharides are inexpensive and very useful starting materials for the synthesis of many naturally occurring glycosides, oligosaccharides, and glycoconjugates. Ferric sulfate hydrate (Fe 2(SO 4) 3· xH 2O) was found to be a valuable Lewis acid promoter in the per- O-acetylation reaction of saccharides with acetic anhydride in 100% of conversion rate and 88-99% yields. Interestingly, the procedure is perfectly compatible with the presence of a variety of acid-labile protecting groups, such as isopropylidene, benzylidene, trityl, and TBDMS groups. The reactions were simply performed by stirring the mixture of a sugar with a slight excessive acetic anhydride in the presence of 2.0 mol % of Fe 2(SO 4) 3· xH 2O at rt and the pure products were obtained by a simple dilution of the reaction mixture with dichloromethane and washings with aqueous Na 2CO 3. 相似文献
7.
Using the thermal decomposition of [Co(NH 3) 6] 2(C 2O 4) 3·4H 2O as a basis, the paper presents results which show how computed values of kinetic parameters are influenced by experimental conditions (ambient atmosphere, sample mass, linear heating rate) when using the non-isothermal methods and the Coats-Redfern (CR) modified equation. It also illustrates the influence of the experimental methods i.e. non-isothermal and isothermal (conventional) methods and also a quasiisothermal-isobaric one which can be recognised as equivalent to Constant Rate Thermal Analysis (CRTA). The results obtained have confirmed the significant influence of the experimental parameters as well as that of the experimental method used on the estimated values of kinetic parameters. The correlation between activation energy ( E) and sample mass ( m) or heating rate (β) is generally of a linear nature: E=a+bx 相似文献
8.
Osmotic coefficients of water have been measured isopiestically for the entire region of homogeneous ternary solutions for the Rb 2SO 4- (NH 4) 2SO 4-H 2O system at 25°C. One might expect that water isoactivity lines should be straight since this system involves a continuous series of solid solutions. The related systems (K 2SO 4-Rb 2SO 4-H 2O and (K 2SO 4- (NH 4) 2 SO 4-H 2O) obey the linearity of water isoactivity lines rule. Contrary to expectations, the (Rb 2SO 4-(NH 4) 2-SO 4-H 2O appears to be the first water–salt system containing continuous solid solutions in which the mentioned rule is not obeyed. 相似文献
9.
Interaction energies between two similar plane parallel double layers for (NH 4) 2Fe(SO 4) 2 or (NH 4) 2Cu(SO 4) 2 type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y e < y 0 ≤ 20. The general expressions were given for the interaction energies of A ν +B ν′ +C ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl 2, Na 2SO 4, FeCl 3, Na 3PO 4, Mg 3(PO 4) 2, Al 2(SO 4) 3, and complex salts (NH 4) 2Fe(SO 4) 2 or (NH 4) 2Cu(SO 4) 2 at y 0 = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH 4) 2Fe(SO 4) 2 was close to that for simple salt Na 3PO 4. Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file. 相似文献
10.
Fe 2(SO 4) 3· xH 2O can be used as an efficient and reusable catalyst for the synthesis of pyrano- and furanotetrahydroquinolines via one-pot three-component Povarov reaction involving aromatic aldehydes, aromatic amines, and cyclic enol ethers. The catalyst is recyclable, economically viable, and environmentally benign. This protocol provides good yields and diastereoselectivity as well as applicability on a wide range of substrates. 相似文献
11.
A Raman study of K 3H(SO 4) 2 as a function of temperature reveals that this compound undergoes a phase transition at Tc = 483 K prior to the decomposition at 508 K. 相似文献
12.
A series of Zr(SO 4) 2/SiO 2 solid acid catalysts with different Zr(SO 4) 2 loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N 2, and temperature-programmed desorption of NH 3. The results showed that the active component Zr(SO 4) 2 was successfully adhered to the mesoporous SiO 2, and the acid amount of Zr(SO 4) 2/SiO 2 increased with the increasing of the Zr(SO 4) 2 loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO 4) 2/SiO 2 to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO 4) 2/SiO 2 exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO 4) 2 loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation. 相似文献
13.
Abstract Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb 2U(SO 4) 3) employing isotope dilution thermal ionisation mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb 2U(SO 4) 3 by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb 2U(SO 4) 3 could be determined with an accuracy better than 0.1% employing the HClO 4 treatment for proper isotopic exchange between the spike and sample isotopes. 相似文献
14.
Hydrogen peroxide (H 2O 2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By
using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition
reaction of H 2O 2 mixed with sulfuric acid (H 2SO 4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic
onset temperature ( T
0), heat of decomposition (Δ H
d), pressure rise rate (d P/d t), and self-heating rate (d T/d t), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations
of H 2SO 4, the experimental data of T
0, Δ H, d P/d t, and d T/d t were obtained. Comparisons of the reactivity for H 2O 2 and H 2O 2 mixed with H 2SO 4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems. 相似文献
15.
KAl(SO 4) 2·12H 2O was found to catalyze efficiently a one-pot three-component cyclocondensation of isatoic anhydride and primary amines or ammonia sources such as (NH 4) 2CO 3, NH 4OAc and NH 4Cl with aromatic aldehydes under mild conditions to afford the corresponding mono- and disubstituted 2,3-dihydroquinazolin-4(1 H)-ones in good yields. 相似文献
16.
The physical properties and phase transition mechanisms of MCr(SO 4) 2·12H 2O ( M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T1 of the 87Rb and 133Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the 87Rb and 133Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T1 are related to variations in the symmetry of the octahedra of water molecules surrounding Rb + and Cs +. We also compared these 87Rb and 133Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO 4) 2·12H 2O and MAl(SO 4) 2·12H 2O crystals. 相似文献
17.
Raman and FTIR spectra of guanidinium zinc sulphate [C(NH 2) 3] 2Zn(SO 4) 2 are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO 42− tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN 3 group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH 2) 3] 2 and HC(NH 2) 3 are computed using Gaussian 03 with HF/6-31G* as basis set. 相似文献
18.
The key problem for the removal of SO 2 by electrical discharge methods is how to obtain the hydroxyl radicals at high concentration and large production rates. With the micro-gap discharge method, O 2 and H 2O in simulated gas streams (N 2/O 2/H 2O/SO 2) are ionized into a large number of OH . radicals to oxidize SO 2 into SO 3 which reacts with H 2O forming H 2SO 4 droplets at 120 °C in the absence of any catalyst or absorbent. The droplets are captured with an electrostatic precipitator. As a result, conversion of SO 2 to primarily H 2SO 4 is limited by the generation of OH . radicals. By increasing the reduced field and concentrations of O 2 and H 2O, the amount of OH . radicals increase resulting in more removal of SO 2 from gas streams. The removal efficiency of SO 2 reaches 100% when the residence time is only 0.74 s. Therefore, a new gas-phase oxidation method for removal of SO 2 without NH 3 additive is found. 相似文献
19.
The incorporation mechanism of Cs + ions from CsNO 3 into NH 4Zr 2(PO 4) 3 was studied on a mixture of CsNO 3 and NH 4Zr 2(PO 4) 3 by powder X-ray diffraction analysis and by monitoring off-gases released from the mixture upon heating with a thermogravimetry
analyzer connected to an infrared spectrometer. With increasing temperature, the decomposition of CsNO 3 first started, followed by the conversion of NH 4Zr 2(PO 4) 3 to HZr 2(PO 4) 3 with the release of NH 3. At around 500°C, the Cs Zr 2(PO 4) 3 phase started to appear as a result of the H +/Cs + ion exchange. No Cs + ion loss was observed at thermal treatment temperatures of 900°C and lower. 相似文献
20.
The thermal decomposition of Co(NO 3) 2·6H 2O ( 1) as well as that one of NO[Co(NO 3) 3] (Co(NO 3) 2·N 2O 4) ( 2) was followed by thermogravimetric (TG) measurements, X-ray recording and Raman and IR spectra. The stepwise decomposition reactions of 1 and 2 leading to anhydrous cobalt(II)nitrate ( 3) were established. In N 2 atmosphere, cobalt oxides are finally formed whereas in H 2/N 2 (10% H 2) cobalt metal is produced. Rapid heating of cobalt(II)nitrate hexahydrate causes melting (formation of a hydrate melt) and therefore side reactions in the hydrate melt by incoupled reactions and evolution/evaporation of different species as, e.g., HNO 3, NO 2, etc. In case of larger amounts in dense packing in the sample container, the formation of oxo(hydoxo)nitrates is possible at higher temperature. For 2, its thermal decomposition to 3 was followed and its decomposition mechanism is proposed. 相似文献
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