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1.
CaS formed from the CaO sorbent during desulfurization in coal gasifiers has to be converted to CaSO4 before disposal. CaS is mainly decomposed to CaO and SO2 by O2 and then CaO is converted to CaSO4 by SO2 and O2. The role of H2O in the oxidative decomposition of CaS with O2 was studied using reagent grade CaS and H218O. The following results were obtained: (1) there is a synergistic effect of H2O and O2 on the oxidative decomposition of CaS to CaO and SO2; (2) H2O reacts with CaS to form CaO, SO2 and H2 in the absence of O2; (3) the oxidative decomposition of CaS to CaO and SO2 occurs stepwise; (4) H2O directly reacts with CaS in the presence of O2; (5) H2O plays an important role in the oxidative decomposition of CaS even if the O2 concentration is high. 相似文献
2.
Sulfuric acid containing limited amounts of water, H2SO4.nH2O with 0.23≤n≤4, has been studied by 1H broad-line NMR at 4 K and MAS NMR at room temperature. The broad-line NMR spectra indicate the formation of H3O+ and HSO4
- ions. H2SO4.2H2O is correctly written as H3O+HSO4
-.H2O. The results are compared with the Nafion- H/water system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The process of recrystallization of apatite phosphogypsum (PHG) in a solution ammonium sulphate (AS) with the subsequent decomposition of the binary salt was investigated and the resulting highly dispersed products with a low P2O5 content have been discussed. The following effects were examined: (NH4)2SO4 concentration, the quantity of ammonium sulphate, the reaction temperature of phosphogypsum with (NH4)2SO4 solution, the time of treatment of phosphogypsum with (NH4)2SO4 solution and the decomposition of the binary salt, as well as the liquid/solid ratio for the binary salts, Based on the results of the chemical and X-ray analysis, it was established that, depending on the technological conditions of the process of recrystallization, binary salts of (NH4)2SO4·CaSO4·H2O and of (NH4)2SO4·CaSO4·H2O and of (NH4)2SO4·5 CaSO4·H2O were formed. As a result of the investigations carried out, a product with a low P2O5 content, suitable for direct processing to secondary products has been prepared. 相似文献
4.
A. K. Biswas N. P. Mohan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1971,21(1):15-18
The rate of dissolution of synthetic cupric sulphide (CuS) which is the analogue of the naturally occurring sulphide mineral covellite, in sulphuric acid solutions of concentration range 5 × 10?3 to 3 mole/l over the temperature range 20–65°c at atmospheric pressure was studied. Thermodynamic considerations suggested that the primary reaction taking place during the leaching is: CuS+1/2O2 + H2SO4 → CuSO4 + S+H2O. It is proposed that up to an initial sulphuric acid concentration of 1 mole/l, the reaction rate is controlled by the diffusion of H+ ions through the sulphur film to the CuS/S interface. For higher sulphuric acid concentrations the oxygen dissolved in the acid decreases and the rate-determining step is believed to be diffusion of dissolved oxygen through the sulphur film to the CuS/S interface. A parabolic model is suggested for the dissolution reaction, and this model is supported by the experimental data. The activation energy for the dissolution reaction was found to be 8000±2000 cal/mole and this was independent of the H+ concentration and hence the nature of the diffusing species. 相似文献
5.
The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na2O-B2O3 systems is investigated. The introduction of sodium fluoride into the Na2O · 2B2O3 and Na2O · 3B2O3 glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity
has been investigated. It is shown that, in glasses of the NaF-Na2O · 2B2O3 system, an increase in the volume concentration of sodium ions from 2.4 × 10−2 to ∼3 × 10−2 mol/cm3 is accompanied by an insignificant decrease in the activation energy Eσ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na2O · 3B2O3 system, an increase in the concentration of sodium ions from 1.8 × 10−2 to ∼2.3 × 10−2 mol/cm3 brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in Eσ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10−2 mol/cm3) virtually does not affect the electric conductivity and Eσ. At the same concentration of sodium ions (∼2.46 × 10−2 mol/cm3) in the 9.8NaF · 90.2[Na2O · 2B2O3] and 57.1NaF · 42.9[Na2O · 3B2O3] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine
content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure. 相似文献
6.
A. A. Pronkin V. N. Naraev I. V. Murin I. A. Sokolov 《Glass Physics and Chemistry》2000,26(3):268-273
The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na2O-B2O3 systems is investigated. The introduction of sodium fluoride into the Na2O · 2B2O3 and Na2O · 3B2O3 glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity
has been investigated. It is shown that, in glasses of the NaF-Na2O · 2B2O3 system, an increase in the volume concentration of sodium ions from 2.4 × 10−2 to ∼3 × 10−2 mol/cm3 is accompanied by an insignificant decrease in the activation energy Eσ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na2O · 3B2O3 system, an increase in the concentration of sodium ions from 1.8 × 10−2 to ∼2.3 × 10−2 mol/cm3 brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in Eσ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10−2 mol/cm3) virtually does not affect the electric conductivity and Eσ. At the same concentration of sodium ions (∼2.46 × 10−2 mol/cm3) in the 9.8NaF · 90.2[Na2O · 2B2O3] and 57.1NaF · 42.9[Na2O · 3B2O3] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine
content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure. 相似文献
7.
Ma Xuedan Guo Daishi Jiang Qizhong Ma Zifeng Ma Zhengfei Ye Weidong Li Chunbo 《Frontiers of Chemical Engineering in China》2007,1(1):45-49
Nanosized solid superacids SO4
2−/TiO2 and S2O8
2−/TiO2, as well as MCM-41-supported SO4
2−/ZrO2, were prepared. Their structures, acidities, and catalytic activities were investigated and compared using XRD, N2 adsorption-desorption, and in situ FTIR-pyridine adsorption, as well as an evaluation reaction with pseudoionone cyclization. The results showed that SO4
2−/TiO2 and S2O8
2−/TiO2 possess not only nanosized particles with diameters < 7.0 nm, a BET surface greater than 140 cm2/g and relatively regular mesostructures with pores around 4.0 nm, but also a pure anatase phase and strong acidity. Different
from the Lewis acid nature of SO4
2−/ZrO2/MCM-41, SO4
2−/TiO2 and S2O8
2−/TiO2 exhibit mainly Bronsted acidities. The strongest Bronsted acid sites were produced on SO4
2−/TiO2 promoted with H2SO4, while Lewis acid sites on S2O8
2−/TiO2 even stronger than those on SO4
2−/ZrO2/MCM-41 were generated when persulfate solution was used as sulfating agent. Because of their distinct acid natures, SO4
2−/TiO2 and S2O8
2−/TiO2 exhibited catalytic activities for the cyclization of pseudoionone that were much higher than that of SO4
2−/ZrO2/MCM-41. It can be concluded that the existence of more Br?nsted acid sites was favorable for proton participation in the
cyclization reaction.
Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(2): 239–244 [译自: 高校化学工程学报] 相似文献
8.
Józef Ceynowa 《Polymer》1982,23(2):203-206
The electromotive force of the membrane cells /Hg/Hg2SO4/H2SO4, a′/ lon exchange Nafion membrane /H2SO4 a″/Hg2SO4/Hg/ with different solution concentrations from 0.01 to 2 mol kg?1 H2O were measured. On that basis the apparent transport number of H+-ions and its dependence on external electrolyte concentration were determined. The dependence was then used for the calculation of both the transport number of H+-ions and the water transference numbers. It was found that the apparent transport number of H+-ions decreases with increasing external concentration while the transport number of H+-ions and the transference number of water remain constant up to concentrations of 1.2 moles kg?1 h2O. 相似文献
9.
Jadwiga Tilly Zbigniew Tomaszewski Jacek Toczkowski 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,52(3):311-315
Absorption of SO2 and SO3 in the solutions of waste ferrous sulfate (so-called ‘green salt’) and in the spent acid after TiO2 hydrolysis, at H2SO4 concentrations ranging from 0–5 to 15 g/m3 (STP), was studied. The rate of SO3 absorption has been found to rise linearly with increasing SO3 concentration in the gas and to be independent on H2SO4 concentration in solution. The SO2 absorption also rises linearly with increasing SO2 content in the gas, but diminishes as H2SO4 concentration increases—an upper limit of 100 g H2SO4/kg H2O is indicated. The initial concentration of the solution must not be higher than 40 g H2SO4/kg H2O. 相似文献
10.
Guohua Wu Yu Fan Andrej Atrens Chunquan Zhai Wenjiang Ding 《Journal of Applied Electrochemistry》2008,38(2):251-257
The influence of Cl− and SO42− on the electrochemical behavior of AZ91D, AZCe2, and AZLa1 was studied. For all alloys, there was a current plateau in the
anodic polarization curves in Na2SO4 solutions. In 0.5% NaCl solution, there was a small current plateau, whereas there was none in the 3.5% and 5% NaCl solutions.
This indicated that SO42− is less aggressive than Cl−. The range of the current plateau decreased with increasing SO42− concentration. For all alloys, the high frequency capacitive loop in the Nyquist plots decreased with increasing concentration
consistent with the decrease in corrosion resistance with increasing Cl− and SO42− concentration. 相似文献
11.
Atar Musa Keskin Hakan Güçlü Yavuzcan H. 《Journal of Coatings Technology and Research》2004,1(3):219-224
The impacts of impregnation and bleaching on the varnish layer hardness of Oriental beech (Fagus orientalist L.) wood were investigated. A number of bleaching combinations {[NaOH−H2O2], [NaOH−Ca(OH)2−H2O2], [NaOH−MgSO4−H2O2] [NaHSO3−H2C2O4], [NaSiO3−H2O2], [KMnO4+NaHSO3+H2O3]} were applied at 18% concentration for bleaching to both impregnated and unimpregnated specimens of Oriental beech wood.
Subsequently, water-based (WB) varnish was coated over the samples and the varnish layer hardness values were determined in
accordance with ASTM D 4366-95.
All of the chemicals used for bleaching reduced the surface hardness. However, after varnish coating, the hardness of most
samples was similar to that of the varnish-coated natural (control) samples. 相似文献
12.
Phosphogypsum (PG) severely pollutes the environment and is difficult to recycle. PG is primarily composed of CaSO4 · 2H2O. In this study, the characteristics of SO2 released from the solid–solid reaction between calcium sulphide (CaS) and CaSO4 were thoroughly investigated using thermodynamic calculations. Experiments were performed by tuning the molar ratio of CaS to CaSO4, reaction atmosphere (S, CH4, N2, and air), and the heating rate. As shown by the phase diagram, high reaction temperatures favour CaO stability, and the corresponding maximum SO2 equilibrium partial pressure increases. The total SO2 production significantly increased with increasing molar ratio and slightly increased when the ratio exceeded 1:3. The SO2 productions were ranked from highest to lowest as follows: S, CH4, N2, CO, and air. The total SO2 production decreased with increasing heating rate. For the reaction between CaS and CaSO4, a higher molar ratio of CaS to CaSO4 no less than 1:3, both S and CH4 reductive atmospheres, and a lower heating rate (2°C/min) favour the total SO2 emission. 相似文献
13.
Dai-Shi Guo Zi-Feng Ma Qi-Zhong Jiang Hai-Hong Xu Zheng-Fei Ma Wei-Dong Ye 《Catalysis Letters》2006,107(3-4):155-159
Solid acid catalysts of SO42−/TiO2/MCM-41 and S2O82−/TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and
better selectivity for cyclization reaction of pseudoionone compared to traditional SO42−/TiO2. A combination of XRD, N2 adsorption–desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted
TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O82−/TiO2/MCM-41 higher S content and more Br?nsted acid sites can be achieved by persulfation, which is favorable for the protons
participated cyclization reaction. The similar Si–O–Ti–O–S=O structure of all acid sites on pore surface of the catalysts
is attributed to the improvement of selectivity in comparison with SO42−/TiO2. 相似文献
14.
X-ray diffraction and neutron diffraction experiments with H/D isotopically substituted aqueous 21 mol% hydrochloric acid solutions were carried out in order to obtain detailed features concerning the intermolecular hydrogen-bonded structure in highly concentrated aqueous acidic solutions. Structure parameters, namely, intermolecular distance, root-mean-square amplitude, and coordination number, for the nearest neighbor H3O+···H2O interaction were determined from the least-squares-fitting analysis of the observed X-ray interference term. These were, respectively, r(H3O+···H2O) = 2.45(1) Å; l(H3O+···H2O) = 0.11(1) Å; and n(H3O+···H2O) = 1.8(1). The intermolecular nearest neighbor distances, r(H···H) = 2.02(5) Å and r(O···H) = 1.69(2) Å, were determined from the least-squares fit to partial structure factors, aij (Q), derived from the observed neutron intermolecular interference terms for sample solutions with different H/D isotopic ratios. The present values of intermolecular distances are significantly shorter than those for pure liquid water, implying that extremely strong hydrogen bonds exist in concentrated aqueous acidic solutions. 相似文献
15.
The extraction of potassium from a tablet mixture of K-feldspar ore and CaSO_4by roasting was studied with a focus on the effects of the decomposition behavior of CaSO_4on the potassium extraction process.The roasted slags were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy,and thermogravimetric(TG)analysis.The XRD analysis revealed that hydrosoluble mischcrystal K_2Ca_2(SO_4)_3was obtained by ion exchange of Ca~(2+)in CaSO_4and K~+in KAlSi_3O_8.Meanwhile,the intermediate product,SiO_2,separated from KAl Si_3O_8and reacted with CaSO_4to decompose CaSO_4.The SEM results showed that some blowholes emerged on the surface of the CaSO_4particles when they reacted with SiO_2at 1200°C,which indicates that SO_2and O_2gases were released from CaSO_4.The TG curves displayed that pure CaSO_4could not be decomposed below 1200°C,while the mixture of K-feldspar ore and CaSO_4began to lose weight at 1000°C.The extraction rate of potassium and decomposition rate of CaSO_4were 62%and 44%,respectively,at a mass ratio of CaSO_4to K-feldspar ore of 3:1,temperature of 1200°C,tablet-forming pressure of6 MPa,and roasting time of 2 h.The decomposition of CaSO_4reduced the potassium extraction rate;therefore,the required amount of CaSO_4was more than the theoretical amount.However,excess CaSO_4was also undesirable for the potassium extraction reaction because a massive amount of SO_2and O_2gas were derived from the decomposition of CaSO_4,which provided poor contact between the reactants.The SO_2released from CaSO_4decomposition can be effectively recycled. 相似文献
16.
The effects of polyvinyl sulfonate (PVS) and polyglutamic acid (PGA) on the precipitation of 2CaSO4· H2O and CaSO4 · 2H2O were compared. PGA strongly retards CaSO4 · 2H2O precipitation from sea water, and also significantly changes its crystal habit. PVS has a similar effect on 2CaSO4 · H2O precipitated at ca. l00°C. The selectivity is related to structural compatibility between the additive and the crystal lattice. A possible mechanism of heterogeneous nucleation of the two crystallographic species upon the suitable polymers is proposed. The hardening of scale in the presence of an unsuitable additive is explained within the framework of the proposed mechanism. 相似文献
17.
A positive-electrolyte-negative (PEN) assembly solid oxide fuel cell (SOFC) with a thin electrolyte film for intermediate
temperature operation was fabricated. Instead of the traditional screen-printing method, both anode and cathode catalysts
were pressed simultaneously and formed with the fabrication of nano-composite electrolyte by press method. This design offered
some advantageous configurations that diminished ohmic resistance between electrolyte and electrodes. It also increased the
proton-conducting rate and improved the performance of SOFCs due to the reduction of membrane thickness and good contact between
electrolyte and electrodes. The fabricated PEN cell generated electricity between 600°C and 680°C using H2S as fuel feed and air as oxidant. Maximum power densities 40 mW·cm−2 and 130 mW·cm−2 for the PEN configuration with a Mo-Ni-S-based composite anode, nano-composite electrolyte (Li2SO4+Al2O3) film and a NiO-based composite cathode were achieved at 600°C and 680°C, respectively. 相似文献
18.
We used commercial activated coke (AC) as adsorbent and fixed-bed, FTIR, N2 adsorption, ion chromatograph as research methods to study the SO2 removal mechanism in the presence of O2 and H2O and adsorbate (H2SO4) desorption mechanism by combined regeneration. The results showed that AC saturation sulfur retention (52.6 mg/g) in SO2+O2+H2O atmosphere was 4.6 times as much as that (11.4 mg/g) in SO2+O2 atmosphere and 5.0 times as much as that (10.6 mg/g) in SO2+O2 atmosphere at 90 °C. O2 and H2O were necessary in AC desulfurization process. Reaction of SO3 and H2O (g) and condensation of sulfuric acid vapor were the dynamic of AC desulfurization process. Water vapor blowing in combined
regeneration inhibited the reaction between H2SO4 and carbon, and consequently reduced the chemical lost of carbon. AC cumulative quality loss (53.6%) of five-times in C-R
was still less than that (62.4%) of three-times in H-R. Water vapor blowing inhibited reactivation effect, as a result reducing
the changes of AC pore structure and surface functional groups. Adsorbate H2SO4 generated in desulfurization evaporated to sulfuric acid vapor due to the high temperature in regeneration and was carried
out by water vapor. 相似文献
19.
Co–BaCO3 catalysts exhibited high catalytic performance for oxidative dehydrogenation of ethane (ODE) using CO2 as oxidant. The maximal formation rate of C2H4 was 0.264 mmol · min−1 · (g · cat.)−1 (48.0% C2H6 conversion, 92.2% C2H4 selectivity, 44.3% C2H4 yield) on 7 wt% Co–BaCO3 catalyst at 650 °C and 6000 ml. (g · cat.)−1. h−1. Co–BaCO3 catalysts were comparatively characterized by XRF, N2 isotherm adsorption-desorption, XRD, H2-TPR and LRs. It was found that Co4+–O species were active sites on these catalysts in ODE with CO2. The redox cycle of Co–O species played an important role on the catalytic performance of Co–BaCO3 catalysts. On the other hand, the co-operation of BaCO3 and BaCoO3 was considered to be one of possible reasons for the high catalytic activity of these catalysts. 相似文献
20.
We investigated the mechanical and electrochemical properties of aluminum alloys. Aluminum alloys do not corrode due to the
formation of an anti-corrosive passive film, such as Al2O3 or Al2O3 · 3H2O, which resists corrosion in neutral solutions. In seawater, however, Cl− ions destroy this passive film. The current density in the first passivity range during the application of anodic protection
had a similar value as that for concentration polarization by dissolved oxygen during the application of cathodic protection.
The current density in the first passivity range had the lowest value overall. The lowest current densities in the potentiostatic
and galvanostatic tests occurred at potentials of −1.4 to −0.7 V and −0.9 to −0.7 V, respectively. 相似文献