| Autor: |
David M. Vandenberg, Toshishige M. Suzuki, Peter C. Ford |
| Rok vydání: |
1984 |
| Předmět: |
|
| Zdroj: |
Journal of Organometallic Chemistry. 272:309-320 |
| ISSN: |
0022-328X |
| DOI: |
10.1016/0022-328x(84)80473-8 |
| Popis: |
The water gas shift reaction, H 2 O + CO ⇌ H 2 + CO 2 , catalyzed homogeneously by a system based on tetrairidiumdodecacarbonyl (Ir 4 (CO) 12 ) in alkaline 2-ethoxyethanol/water solution was examined at moderate temperatures (90–130°C) and pressures ( P CO 0.5–2.0 atm). The catalytic reaction showed an approximate first-order dependence on base concentration and on the concentration of iridium. The catalytic cycle was shown to have a zero order dependence on the partial pressure of CO. An apparent activation energy of 10.7 kcal mol −1 was obtained from a linear Arrhenius plot based on hydrogen production over the temperature range 90–130°C. The predominant pathway of the reaction can be explained by a mechanism in which activation of CO by nucleophilic attack of hydroxide on the metal hydride species HIr 4 (CO) 11 − produces the dihydride species, H 2 Ir 4 (CO) 10 2− in the rate-limiting step. Subsequent reaction of this anion with H 2 O gives H 2 plus HIr 4 (CO) 11 − again. The complex Ir 8 (CO) 20 2− is shown to be a catalytically poor component of the solution. The system has also been shown to be active toward the decomposition of formate. This pathway however, is concluded to make an insignificant contribution to the catalysis rate under water gas shift reaction conditions. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
