Different morphologies of BaCO3 crystals with dendritic structure,spinous sphere structure,and spike-,flower-and rod-like structures were prepared with（C2H5）2CO3 and BaCl2.2H2O as raw materials by homogeneous precip...Different morphologies of BaCO3 crystals with dendritic structure,spinous sphere structure,and spike-,flower-and rod-like structures were prepared with（C2H5）2CO3 and BaCl2.2H2O as raw materials by homogeneous precipitation method.The crystals have been characterized by SEM,FT-IR and XRD,indicating that the different morphology of BaCO3 crystals belongs to the orthorhombic crystal system with uniform distribution and integral shapes.The effect of reaction conditions and the possible formation mechanism on the morphology of BaCO3 crystals have been discussed.展开更多
The purpose of this work was to report excess molar volumes and dynamic viscosities of the binary mixture of diethyl carbonate （DEC）+ethanol. Densities and viscosities of the binary mixture of DEC+ethanol at tempera...The purpose of this work was to report excess molar volumes and dynamic viscosities of the binary mixture of diethyl carbonate （DEC）+ethanol. Densities and viscosities of the binary mixture of DEC+ethanol at temperatures 293.15 K—343.15 K and atmospheric pressure were determined over the entire composition range. Densities of the binary mixture of DEC+ethanol were measured by using a vibrating U-shaped sample tube densimeter. Viscosities were determined by using Ubbelohde suspended-level viscometer. Densities are accurate to 1.0×10-5 g·cm-3, and viscosities are reproducible within ±0.003 mPa·s. From these data, excess molar volumes and deviations in viscosity were calculated. Positive excess molar volumes and negative deviations in viscosity for DEC+ethanol system are due to the strong specific interactions.All excess molar vo-（lumes） and deviations in viscosity fit to the Redlich-Kister polynomial equation.The fitting parameters were presented,and the average deviations and standard deviations were also calculated.The errors of correlation are very small.It proves that it is valuable for estimating densities and viscosities of the binary mixture by the correlated equation.展开更多
Destructive tests of the catalyst was carried out to study the effect oftemperature on the catalytic activity of CO coupling to diethyl oxalate (DEO) over a Pd-Fe/Al_2O_3catalyst. It was found that a temperature jump ...Destructive tests of the catalyst was carried out to study the effect oftemperature on the catalytic activity of CO coupling to diethyl oxalate (DEO) over a Pd-Fe/Al_2O_3catalyst. It was found that a temperature jump could cause the deactivation of the Pd-Fe/α-Al_2O_3catalyst. The catalyst deactivated at different temperatures has different characteristics. Afterdeactivation the crystal structure of α-Al_2O_3 did not change, but the Pd particle size wasenlarged. Most of the Pd^0 were oxidized to Pd^(2+), and Fe^(2+) was oxidized to Fe^(3+) on thesurface of the deactivated catalyst. The catalyst could be regenerated, but its original activitycould not be recovered completely.展开更多
Diethyl carbonate has been synthesized via the alcoholysis of ethyl carbamate in supercritical ethanol under catalyst-free conditions.The influences of various parameters such as reaction temperature,reaction time,rea...Diethyl carbonate has been synthesized via the alcoholysis of ethyl carbamate in supercritical ethanol under catalyst-free conditions.The influences of various parameters such as reaction temperature,reaction time,reaction pressure,ethanol/ethyl molar ratios and reaction loading volume on the yield of DEC were studied systematically.The experimental results indicated that the alcoholysis of ethyl carbamate was greatly improved in supercritical ethanol.The optimal reaction conditions were as follows：a reaction temperature of 573 K,a reaction time of 30 min,a reaction pressure of 13.2 MPa,an ethanol/ethyl carbamate molar ratio of 10 and a reactor loading volume of 285 μL respectively.The optimal yield of DEC was 22.9%.展开更多
CuCl supported on molecular sieves has attracted increasing attention in catalyzing oxidative carbonylation of ethanol to diethyl carbonate. Mesoporous MCM-41 has been widely used as catalyst support due to its large ...CuCl supported on molecular sieves has attracted increasing attention in catalyzing oxidative carbonylation of ethanol to diethyl carbonate. Mesoporous MCM-41 has been widely used as catalyst support due to its large surface area and well defined mesoporous structure. Considering its intrinsic weak acidity, MCM- 41 was modified by a simple impregnation method to incorporate A1. The incorporation of A1 components resulted in the high dispersion of Cu species and the increase of acid sites without changing the mesoporous structure of MCM-41, and thus enhanceed the catalytic activity of CuCl/MCM-41 for diethyl carbonate synthesis.展开更多
文摘Different morphologies of BaCO3 crystals with dendritic structure,spinous sphere structure,and spike-,flower-and rod-like structures were prepared with（C2H5）2CO3 and BaCl2.2H2O as raw materials by homogeneous precipitation method.The crystals have been characterized by SEM,FT-IR and XRD,indicating that the different morphology of BaCO3 crystals belongs to the orthorhombic crystal system with uniform distribution and integral shapes.The effect of reaction conditions and the possible formation mechanism on the morphology of BaCO3 crystals have been discussed.
文摘The purpose of this work was to report excess molar volumes and dynamic viscosities of the binary mixture of diethyl carbonate （DEC）+ethanol. Densities and viscosities of the binary mixture of DEC+ethanol at temperatures 293.15 K—343.15 K and atmospheric pressure were determined over the entire composition range. Densities of the binary mixture of DEC+ethanol were measured by using a vibrating U-shaped sample tube densimeter. Viscosities were determined by using Ubbelohde suspended-level viscometer. Densities are accurate to 1.0×10-5 g·cm-3, and viscosities are reproducible within ±0.003 mPa·s. From these data, excess molar volumes and deviations in viscosity were calculated. Positive excess molar volumes and negative deviations in viscosity for DEC+ethanol system are due to the strong specific interactions.All excess molar vo-（lumes） and deviations in viscosity fit to the Redlich-Kister polynomial equation.The fitting parameters were presented,and the average deviations and standard deviations were also calculated.The errors of correlation are very small.It proves that it is valuable for estimating densities and viscosities of the binary mixture by the correlated equation.
基金Supported by National"Ninth-Five" Scientific Research Project(Grant number:96-539-01)
文摘Destructive tests of the catalyst was carried out to study the effect oftemperature on the catalytic activity of CO coupling to diethyl oxalate (DEO) over a Pd-Fe/Al_2O_3catalyst. It was found that a temperature jump could cause the deactivation of the Pd-Fe/α-Al_2O_3catalyst. The catalyst deactivated at different temperatures has different characteristics. Afterdeactivation the crystal structure of α-Al_2O_3 did not change, but the Pd particle size wasenlarged. Most of the Pd^0 were oxidized to Pd^(2+), and Fe^(2+) was oxidized to Fe^(3+) on thesurface of the deactivated catalyst. The catalyst could be regenerated, but its original activitycould not be recovered completely.
基金supported by the National Natural Science Foundation of China(No.21073064)
文摘Diethyl carbonate has been synthesized via the alcoholysis of ethyl carbamate in supercritical ethanol under catalyst-free conditions.The influences of various parameters such as reaction temperature,reaction time,reaction pressure,ethanol/ethyl molar ratios and reaction loading volume on the yield of DEC were studied systematically.The experimental results indicated that the alcoholysis of ethyl carbamate was greatly improved in supercritical ethanol.The optimal reaction conditions were as follows：a reaction temperature of 573 K,a reaction time of 30 min,a reaction pressure of 13.2 MPa,an ethanol/ethyl carbamate molar ratio of 10 and a reactor loading volume of 285 μL respectively.The optimal yield of DEC was 22.9%.
基金Financial support from the National Natural Science Foundation of China （Grant No. 21325626, 20936003, 20876112）, Specialized Research Fund for the Doctoral Program of Higher Education （SRFDP） （No. 20090032110021） and the Program of Introducing Talents of Discipline to Universities （No. B06006） is gratefully acknowledged.
文摘CuCl supported on molecular sieves has attracted increasing attention in catalyzing oxidative carbonylation of ethanol to diethyl carbonate. Mesoporous MCM-41 has been widely used as catalyst support due to its large surface area and well defined mesoporous structure. Considering its intrinsic weak acidity, MCM- 41 was modified by a simple impregnation method to incorporate A1. The incorporation of A1 components resulted in the high dispersion of Cu species and the increase of acid sites without changing the mesoporous structure of MCM-41, and thus enhanceed the catalytic activity of CuCl/MCM-41 for diethyl carbonate synthesis.
