The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional ...The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional transition state theory （CTST）. The mechanism and rate constant of the five different reaction paths are consid- ered corresponding to HCOCHO＋H2O, HCOCHO＋H2O… H2O, HCOCHO… H2O＋H2O, HCOCHO＋H2O… H2SO4 and HCOCHO… H2O＋H2SOa. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD（T）/6- 311＋＋G（3df, 3pd）//M06-2X/6-311＋＋G（3df, 3pd） level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10-11 cm3/（molecule.s）, about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10-11 cm3/（molecule·s） at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal＋OH under certain atmospheric condi- tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.展开更多
A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applie...A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.展开更多
A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the ex...A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown that V2O5 diffraction peaks gradually strengthen with the increase of the content of V2O5. With the content of 3% V2O5 and the calcination temperature of 573 K, V2O5/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached 18.76% and 77.70% after 5 h, respectively. Moreover, V2O5/C catalyst showed small deactivation after recycling three times, which indicates that V2O5/C has a higher stability than noble metal catalysts in the reaction medium.展开更多
Based on ion chromatography technology, we have developed a new method that combines ion chromatography with a conductivity detector to separate and determine the substances of oxalic acid and glyoxalic acid, which ar...Based on ion chromatography technology, we have developed a new method that combines ion chromatography with a conductivity detector to separate and determine the substances of oxalic acid and glyoxalic acid, which are the main substances in the electrosynthesis of glyoxalic acid. The experimental results demonstrate that the detection sensitivity is ahead of 10 -6 grade, the cofficient of variation of retention time, the height of peak and the area of peak outperform 1%. All the recoveries of the detected substances are ranged between 98% and 102%. The method exhibits advantages of high selectivity, sensitivity, speediness and simple equipment. Furthermore, simultaneous determination of a mixture of several substances can be carried out by the method. We have demonstrated in the current paper that the ion chromatography is a speedy, effective, new detection method, which may be used to determine the substances existing in the electrosynthesis process of glyoxalic acid.展开更多
文摘The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional transition state theory （CTST）. The mechanism and rate constant of the five different reaction paths are consid- ered corresponding to HCOCHO＋H2O, HCOCHO＋H2O… H2O, HCOCHO… H2O＋H2O, HCOCHO＋H2O… H2SO4 and HCOCHO… H2O＋H2SOa. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD（T）/6- 311＋＋G（3df, 3pd）//M06-2X/6-311＋＋G（3df, 3pd） level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10-11 cm3/（molecule.s）, about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10-11 cm3/（molecule·s） at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal＋OH under certain atmospheric condi- tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.
文摘A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.
基金Supported by the Technology Research and Development Project for University of Shanxi Province of China (Grant No. 20051272)
文摘A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown that V2O5 diffraction peaks gradually strengthen with the increase of the content of V2O5. With the content of 3% V2O5 and the calcination temperature of 573 K, V2O5/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached 18.76% and 77.70% after 5 h, respectively. Moreover, V2O5/C catalyst showed small deactivation after recycling three times, which indicates that V2O5/C has a higher stability than noble metal catalysts in the reaction medium.
文摘Based on ion chromatography technology, we have developed a new method that combines ion chromatography with a conductivity detector to separate and determine the substances of oxalic acid and glyoxalic acid, which are the main substances in the electrosynthesis of glyoxalic acid. The experimental results demonstrate that the detection sensitivity is ahead of 10 -6 grade, the cofficient of variation of retention time, the height of peak and the area of peak outperform 1%. All the recoveries of the detected substances are ranged between 98% and 102%. The method exhibits advantages of high selectivity, sensitivity, speediness and simple equipment. Furthermore, simultaneous determination of a mixture of several substances can be carried out by the method. We have demonstrated in the current paper that the ion chromatography is a speedy, effective, new detection method, which may be used to determine the substances existing in the electrosynthesis process of glyoxalic acid.
