Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liq...Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liquidus temperatures for primary crystallization was derived t=1003.5–0.081×A2.3159–5.87×B0.657–0.024×A2.22×B1.14＋ 0.035×A2.17×B1.084, where t is the liquidus temperature in degree Celsius, A denotes the mass fraction of AlF3 in system Na3AlF6-K3AlF6- AlF3, and B denotes K3AlF6/（Na3AlF6＋K3AlF6 ） in mass（%, the value was defined as KR in this paper）. The composition limitations are 0w（AlF3）30%, and 0KR50%. The isothermal diagram of molten salt system Na3AlF6-K3AlF6-AlF3 was obtained in this composition limitation.展开更多
Raman spectrum of molten cryolite was recorded. Based on the new understanding of the scattering coefficients, contents of various structural entities in acidic NaF-AlF3 melts at 942-1 024 ℃ in previous research were...Raman spectrum of molten cryolite was recorded. Based on the new understanding of the scattering coefficients, contents of various structural entities in acidic NaF-AlF3 melts at 942-1 024 ℃ in previous research were reanalyzed. The new quantitative analysis results show that when cryolite ratio（CR） is less than 2, AlF4- is the dominant anion in the melts, and its mole fraction is about 0.70 for melts with CR=1.5 and 0.50 for melts with CR=2. When CR is more than 2.5, the mole fraction of AlF6^3- is relatively large, which is around 0.45 for melts with CR=2.5. Ionic structure of Na3AlF6-Al2O3 melts was investigated by UV-Raman spectroscopy. Octahedral AlF6^3- and tetrahedral AlF4- are proved to exist with possible partial replacement of F- by O^2-. Al2O2F4^2- with a large scattering coefficient also exists in the melts in which alumina concentration is more than 4% （mass fraction）. The increase of temperature causes blue-shift of the bands in the Raman spectra.展开更多
The alumina solubility in the title system within the composition range of KR{m（K3AlF6）/[m（K3AlF6）＋ m（Na3AlF6）]} 10%―50%, a ternary Na3AlF6-K3AlF6-AlF3 molten system with 23%―29%（mass fraction） AlF3 was inv...The alumina solubility in the title system within the composition range of KR{m（K3AlF6）/[m（K3AlF6）＋ m（Na3AlF6）]} 10%―50%, a ternary Na3AlF6-K3AlF6-AlF3 molten system with 23%―29%（mass fraction） AlF3 was investigated by measuring the mass loss of a rotating sintered corundum disc. And the following empirical equation was derived when superheat degree was no more than 60 °C： w（Al2O3）sat=A×（T/1000）B, where A= –1.85774＋ 26.754234w（AlF3）–0.3683–0.00783KR2.363＋0.010266KR2.3048＋0.7902w（AlF3）0.00652, B=112.4625–53.2567w（AlF3）0.4236＋ 5.1079w（AlF3）0.9241＋0.01542w（AlF3）1.3540. Considering both higher alumina solubility and not too high superheat de gree are required, alumina solubility of different compositions at not the same temperature but the same superheat degree was studied, which will be more industrial helpful for selecting prospective compositions. The results show that the composition deserved to be further tested in lower temperature cells is 10%―30% KR and 23%―26%（mass fraction） AlF3.展开更多
The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various elect...The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various electrolyte compositions. The results indicate that the electrical resistivity of cermet studied has negative temperature coefficient, which is the characteristic of semi-conducting material. The proper addition of AlF3 in the bath can improve the corrosion resistance of cermet inert anode, but excess adding amount will cause the catastrophic corrosion. Post-examination of anodes shows that metal Ni leaches preferentially on the anode surface. Chemical dissolution, electrolyte penetration as well as electrochemical dissolution serve as major corrosion mechanisms.展开更多
Experimental technique has been inadequate to anodic overvoltage measurements in aluminum electrolysis. To determine its ohmic/voltage drop precisely, a current interruption technique was modified with a high frequenc...Experimental technique has been inadequate to anodic overvoltage measurements in aluminum electrolysis. To determine its ohmic/voltage drop precisely, a current interruption technique was modified with a high frequency digital oscilloscope, current interrupters with fast switching time, an improved cell configuration and a simulation applied to the oscillating potential decay curve. The results show that the technique can give good reproducibility for overvoltage studies. A substantial increase of anodic overvoltage is observed with graphite powder addition, metallic aluminum addition and CO bubbling in the melts.展开更多
A protocol for the synthesis of some 4-Aryl-1,3,4,6,7,8-hexahydroquinazolin-2,5(1H,6H)-diones (HHQs) was developed by means of a three-component condensation reaction of an aromatic aldehyde, 1,3-cylohexadione and ure...A protocol for the synthesis of some 4-Aryl-1,3,4,6,7,8-hexahydroquinazolin-2,5(1H,6H)-diones (HHQs) was developed by means of a three-component condensation reaction of an aromatic aldehyde, 1,3-cylohexadione and urea in the presence of K3AlF6 (Al2O3/KF) as catalyst. This reaction is carried out under different conditions including 1) solvent free;2) reflux in acetonitrile;3) reflux in ethanol;4) reflux in chloroform;and 5) reflux in water. In all conditions, the desired products are obtained in high yields after relatively short reaction times. Nevertheless, the reactions proceed faster and in higher yields when they were carried out in acetonitrile. This adopted protocol for some Biginelli-type products has offered the advantages of reusability of the catalyst, high yields and ease of separation of pure products. Furthermore, the catalyst is easily prepared, stabilized and efficiently used under reaction conditions.展开更多
基金Supported by the National Basic Research Program of China(No.2005CB623703)the National High-Tech Research and Development Program of China(No.2008AA030503)
文摘Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liquidus temperatures for primary crystallization was derived t=1003.5–0.081×A2.3159–5.87×B0.657–0.024×A2.22×B1.14＋ 0.035×A2.17×B1.084, where t is the liquidus temperature in degree Celsius, A denotes the mass fraction of AlF3 in system Na3AlF6-K3AlF6- AlF3, and B denotes K3AlF6/（Na3AlF6＋K3AlF6 ） in mass（%, the value was defined as KR in this paper）. The composition limitations are 0w（AlF3）30%, and 0KR50%. The isothermal diagram of molten salt system Na3AlF6-K3AlF6-AlF3 was obtained in this composition limitation.
基金Project (51004034) supported by the National Natural Science, ChinaProject(N090302009) supported by the Fundamental Research Funds for the Central Universities, China
文摘Raman spectrum of molten cryolite was recorded. Based on the new understanding of the scattering coefficients, contents of various structural entities in acidic NaF-AlF3 melts at 942-1 024 ℃ in previous research were reanalyzed. The new quantitative analysis results show that when cryolite ratio（CR） is less than 2, AlF4- is the dominant anion in the melts, and its mole fraction is about 0.70 for melts with CR=1.5 and 0.50 for melts with CR=2. When CR is more than 2.5, the mole fraction of AlF6^3- is relatively large, which is around 0.45 for melts with CR=2.5. Ionic structure of Na3AlF6-Al2O3 melts was investigated by UV-Raman spectroscopy. Octahedral AlF6^3- and tetrahedral AlF4- are proved to exist with possible partial replacement of F- by O^2-. Al2O2F4^2- with a large scattering coefficient also exists in the melts in which alumina concentration is more than 4% （mass fraction）. The increase of temperature causes blue-shift of the bands in the Raman spectra.
基金Supported by the National Basic Research Program of China(No.2005CB623703)the National High-Tech Research and Development Program of China(No.2008AA030503)
文摘The alumina solubility in the title system within the composition range of KR{m（K3AlF6）/[m（K3AlF6）＋ m（Na3AlF6）]} 10%―50%, a ternary Na3AlF6-K3AlF6-AlF3 molten system with 23%―29%（mass fraction） AlF3 was investigated by measuring the mass loss of a rotating sintered corundum disc. And the following empirical equation was derived when superheat degree was no more than 60 °C： w（Al2O3）sat=A×（T/1000）B, where A= –1.85774＋ 26.754234w（AlF3）–0.3683–0.00783KR2.363＋0.010266KR2.3048＋0.7902w（AlF3）0.00652, B=112.4625–53.2567w（AlF3）0.4236＋ 5.1079w（AlF3）0.9241＋0.01542w（AlF3）1.3540. Considering both higher alumina solubility and not too high superheat de gree are required, alumina solubility of different compositions at not the same temperature but the same superheat degree was studied, which will be more industrial helpful for selecting prospective compositions. The results show that the composition deserved to be further tested in lower temperature cells is 10%―30% KR and 23%―26%（mass fraction） AlF3.
基金Project(2005CB623703) supported by the National Basic Research Program of China Project(50474051) supported by the National Natural Science Foundation of China Project(03JJY3080) supported by the Natural Science Foundation of Hunan Province, China
文摘The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various electrolyte compositions. The results indicate that the electrical resistivity of cermet studied has negative temperature coefficient, which is the characteristic of semi-conducting material. The proper addition of AlF3 in the bath can improve the corrosion resistance of cermet inert anode, but excess adding amount will cause the catastrophic corrosion. Post-examination of anodes shows that metal Ni leaches preferentially on the anode surface. Chemical dissolution, electrolyte penetration as well as electrochemical dissolution serve as major corrosion mechanisms.
文摘Experimental technique has been inadequate to anodic overvoltage measurements in aluminum electrolysis. To determine its ohmic/voltage drop precisely, a current interruption technique was modified with a high frequency digital oscilloscope, current interrupters with fast switching time, an improved cell configuration and a simulation applied to the oscillating potential decay curve. The results show that the technique can give good reproducibility for overvoltage studies. A substantial increase of anodic overvoltage is observed with graphite powder addition, metallic aluminum addition and CO bubbling in the melts.
文摘A protocol for the synthesis of some 4-Aryl-1,3,4,6,7,8-hexahydroquinazolin-2,5(1H,6H)-diones (HHQs) was developed by means of a three-component condensation reaction of an aromatic aldehyde, 1,3-cylohexadione and urea in the presence of K3AlF6 (Al2O3/KF) as catalyst. This reaction is carried out under different conditions including 1) solvent free;2) reflux in acetonitrile;3) reflux in ethanol;4) reflux in chloroform;and 5) reflux in water. In all conditions, the desired products are obtained in high yields after relatively short reaction times. Nevertheless, the reactions proceed faster and in higher yields when they were carried out in acetonitrile. This adopted protocol for some Biginelli-type products has offered the advantages of reusability of the catalyst, high yields and ease of separation of pure products. Furthermore, the catalyst is easily prepared, stabilized and efficiently used under reaction conditions.
