Sol–gel derived hybrid materials as heterogeneous catalysts for the synthesis of N,N-dimethylformamide from supercritical carbon dioxide
作者:Oliver Kröcher、René A. Köppel、Alfons Baiker
DOI:10.1039/cc9960001497
日期:——
Hybrid materials derived from group VIII metal-chloro complexes of the type MCl(2)X(2) (M = Pt, Pd), MClX(3) (M = Rh, Ir) and especially RuCl(2)X(3) [X = Ph(2)P(CH2)(2)Si(OEt)(3), Me(2)P(CH2)(2)Si(OEt)(3)] by cocondensation with Si(OEt)(4) via a sol-gel process are highly active heterogeneous catalysts for the synthesis of N,N-dimethylformamide (dmf) from CO2, H-2 and dimethylamine under supercritical conditions, affording turnover numbers up to 110 800 at 100% selectivity.
Silica hybrid gel catalysts containing ruthenium complexes: influence of reaction parameters on the catalytic behaviour in the synthesis of N,N-dimethylformamide from carbon dioxide
作者:Oliver Kröcher、René A. Köppel、Alfons Baiker
DOI:10.1016/s1381-1169(98)00224-6
日期:1999.4
The synthesis of N,N-dimethylformamide from carbon dioxide, hydrogen and dimethylamine has been studied in an autoclave using a sol-gel derived heterogeneous catalyst made of RuCl2PPh2(CH2)(2)Si(OEt)(3)}(3) and Si(OEt)(4) in a ratio of 1:50. The effect of the reaction variables on the activity and selectivity of the hybrid gel was examined by varying the initial concentrations of the catalyst and dimethylamine, the partial pressures of hydrogen and carbon dioxide, the temperature and the stirring frequency. Parametric investigations revealed that the measured reaction rates are not disguised by mass transfer phenomena under the conditions applied. The suitable temperature range of the reaction is between 370 and 400 K, with the upper temperature limit given by the thermal stability of the catalyst. Hydrogen appeared to be the Limiting reactant since it significantly influenced the reaction rate. In contrast, the carbon dioxide partial pressure in the range 3-18 MPa and the dimethylamine concentration had only a negligible effect on the turnover frequency, indicating a zeroth order dependence. High concentrations of hydrogen and carbon dioxide in the Liquid dimethylamine phase afford high concentrations of all reactants at the catalytic centres in an ideal reaction design. (C) 1999 Elsevier Science B.V. All rights reserved.