A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation e...A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.展开更多
The title complex (enH2){NH4[Co(en)3][Mo2O7(C2O4)]}22H2O (C18H70Co2Mo4- N16O24, Mr = 1396.52) was obtained under hydrothermal conditions and its crystal structure has been determined by single-crystal X-ray diffractio...The title complex (enH2){NH4[Co(en)3][Mo2O7(C2O4)]}22H2O (C18H70Co2Mo4- N16O24, Mr = 1396.52) was obtained under hydrothermal conditions and its crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 17.8023(8), b = 7.7527(4), c = 16.9781(4) ? b = 103.878(7), V = 2274.8(2) 3, Dc = 2.039 g/cm3, Z = 2, m(MoKa) = 1.878 mm-1 and F(000) = 1408. The final R = 0.0410 and wR = 0.1070 for 4065 observed reflections with I≥2s(I). The crystal structure is composed of bi- nuclear [Mo2O7(C2O4)]4- anions, complex [Co(en)3]2+ cations, protonated ethylenediamine cations, ammonium cations and crystal water molecules, which are held together into a three-dimensional network via hydrogen-bonding interactions. The binuclear structure of [Mo2O7(C2O4)]4- consist of one MoO4 and one MoO6 octahedra through sharing a bridging oxygen atom, where the oxalate ligand acts as a bidentate ligand coordinating to the octahedral molybdenum atom though two deprotonated corboxylate groups.展开更多
The production of higher terminal alcohols through CO hydrogenation according to the Fischer–Tropsch(F–T) process has been a topic of interest since the Institut Fran?ais du Pétrole(IFP) demonstrated shortchain...The production of higher terminal alcohols through CO hydrogenation according to the Fischer–Tropsch(F–T) process has been a topic of interest since the Institut Fran?ais du Pétrole(IFP) demonstrated shortchain C_1–C_6mixed alcohols production over cobalt–copper based catalysts. A number of catalyst formulations were screened for their suitability at that time. In particular, the addition of Cr, Zn, Al, Mn and V to Co Cu was investigated. In a number of patents, it was shown that catalyst preparation is crucial in these catalyst formulations and that high alcohols selectivity can only be achieved by carefully respecting the procedures and recipes. This short critical review highlights recent developments in Co Cu-based catalysts for higher terminal alcohols synthesis via F–T synthesis. Special attention will be given to catalyst preparation which according to developments in our group is based on oxalate precipitation. This way we show that the close association of Co and Cu on the one hand and promoter/dispersant on the other are of utmost importance to ensure high performance of the catalysts. We shall concentrate on 'Co Cu Mn','Co Cu Mo' and 'Co Cu Nb' catalyst formulations, all prepared via oxalate precipitation and combined with'entrainment techniques' if necessary, and show high total alcohols selectivity can be obtained with tunable Anderson-Schulz-Flory chain-lengthening probability. Either long-chain C_8–C_(14)terminal alcohols as feedstock for plasticizers, lubricants and detergents, or short-chain C_2–C_5alcohols as 'alkanol' fuels or fuel additives can be formed this way.展开更多
Well-defined two-dimensional(2D)cobalt oxalate(CoC_(2)O_(4)·2H_(2)O)nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of io...Well-defined two-dimensional(2D)cobalt oxalate(CoC_(2)O_(4)·2H_(2)O)nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of ion and electron.However,the delicate control of the 2D morphology of CoC_(2)O_(4)·2H_(2)O during their synthesis remains challenging.Herein,2D CoC_(2)O_(4)·2H_(2)O nanosheets(M1),grown by straightforward chemical precipitation,can be tuned from three-dimensional(3D)structure during their synthesis with no templates or capping agents.This control is obtained by rationally changing the ratio of reactants with ethylene glycol as solvent.Moreover,Co_(3)O_(4)/CoC_(2)O_(4)composites(M1-250)have been fabricated through low-temperature thermal treatment of the M1 precursor in air,which possess porous surfaces with the 2D morphology maintained.Benefiting from the porous surfaces,more redox-active sites and better electrical conductivity of Co_(3)O_(4),the constructed M1-250//AC aqueous device manifest improved kinetics of the electrochemistry process with energy density of 27.9 Wh/kg at 550.7 W/kg and good cycling stability with sustaining 73.0 m Ah/g after 5000 cycles.展开更多
文摘A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.
基金the Natural Science Foundation of Fujian province
文摘The title complex (enH2){NH4[Co(en)3][Mo2O7(C2O4)]}22H2O (C18H70Co2Mo4- N16O24, Mr = 1396.52) was obtained under hydrothermal conditions and its crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 17.8023(8), b = 7.7527(4), c = 16.9781(4) ? b = 103.878(7), V = 2274.8(2) 3, Dc = 2.039 g/cm3, Z = 2, m(MoKa) = 1.878 mm-1 and F(000) = 1408. The final R = 0.0410 and wR = 0.1070 for 4065 observed reflections with I≥2s(I). The crystal structure is composed of bi- nuclear [Mo2O7(C2O4)]4- anions, complex [Co(en)3]2+ cations, protonated ethylenediamine cations, ammonium cations and crystal water molecules, which are held together into a three-dimensional network via hydrogen-bonding interactions. The binuclear structure of [Mo2O7(C2O4)]4- consist of one MoO4 and one MoO6 octahedra through sharing a bridging oxygen atom, where the oxalate ligand acts as a bidentate ligand coordinating to the octahedral molybdenum atom though two deprotonated corboxylate groups.
基金supported by the National Science Foundation under contract No.CBET-1438227
文摘The production of higher terminal alcohols through CO hydrogenation according to the Fischer–Tropsch(F–T) process has been a topic of interest since the Institut Fran?ais du Pétrole(IFP) demonstrated shortchain C_1–C_6mixed alcohols production over cobalt–copper based catalysts. A number of catalyst formulations were screened for their suitability at that time. In particular, the addition of Cr, Zn, Al, Mn and V to Co Cu was investigated. In a number of patents, it was shown that catalyst preparation is crucial in these catalyst formulations and that high alcohols selectivity can only be achieved by carefully respecting the procedures and recipes. This short critical review highlights recent developments in Co Cu-based catalysts for higher terminal alcohols synthesis via F–T synthesis. Special attention will be given to catalyst preparation which according to developments in our group is based on oxalate precipitation. This way we show that the close association of Co and Cu on the one hand and promoter/dispersant on the other are of utmost importance to ensure high performance of the catalysts. We shall concentrate on 'Co Cu Mn','Co Cu Mo' and 'Co Cu Nb' catalyst formulations, all prepared via oxalate precipitation and combined with'entrainment techniques' if necessary, and show high total alcohols selectivity can be obtained with tunable Anderson-Schulz-Flory chain-lengthening probability. Either long-chain C_8–C_(14)terminal alcohols as feedstock for plasticizers, lubricants and detergents, or short-chain C_2–C_5alcohols as 'alkanol' fuels or fuel additives can be formed this way.
基金the National Natural Science Foundation of China(No.U1904215)Natural Science Foundation of Jiangsu Province(No.BK20200044)Program for Young Changjiang Scholars of the Ministry of Education,China(No.Q2018270)。
文摘Well-defined two-dimensional(2D)cobalt oxalate(CoC_(2)O_(4)·2H_(2)O)nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of ion and electron.However,the delicate control of the 2D morphology of CoC_(2)O_(4)·2H_(2)O during their synthesis remains challenging.Herein,2D CoC_(2)O_(4)·2H_(2)O nanosheets(M1),grown by straightforward chemical precipitation,can be tuned from three-dimensional(3D)structure during their synthesis with no templates or capping agents.This control is obtained by rationally changing the ratio of reactants with ethylene glycol as solvent.Moreover,Co_(3)O_(4)/CoC_(2)O_(4)composites(M1-250)have been fabricated through low-temperature thermal treatment of the M1 precursor in air,which possess porous surfaces with the 2D morphology maintained.Benefiting from the porous surfaces,more redox-active sites and better electrical conductivity of Co_(3)O_(4),the constructed M1-250//AC aqueous device manifest improved kinetics of the electrochemistry process with energy density of 27.9 Wh/kg at 550.7 W/kg and good cycling stability with sustaining 73.0 m Ah/g after 5000 cycles.
