Kinetics and Mechanism of the Homogeneous oxidation of n-Butenes to Methyl Ethyl Ketone in a Solution of Mo-V-Phosphoric Heteropoly Acid in the Presence of Palladium Pyridine-2,6-Dicarboxylate
Full article
| Общее |
Language:
Английский,
Genre:
Full article,
Status:
Published,
Source type:
Translated
|
| Journal |
Kinetics and Catalysis
ISSN: 0023-1584
, E-ISSN: 1608-3210
|
| Output data |
Year: 2011,
Volume: 52,
Number: 6,
Pages: 828-834
Pages count
: 7
DOI:
10.1134/S0023158411060164
|
| Authors |
Odyakov V.F.
1
,
Zhizhina E.G.
1
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis SB RAS
|
|
In catalytic two-step n-butene oxidation with dioxygen to methyl ethyl ketone, the first step is the oxidation of n-C4H8 with an aqueous solution of Mo-V-P heteropoly acid in the presence of Pd(II) complexes. The kinetics of n-butene oxidation with solutions of H7PV4Mo8O40 (HPA-4) in the presence of the Pd(II) dipicolinate complex (H2O)PdII(dipic) (I), where dipic2− is the tridentate ligand 2,6-NC5H3(COO−)2, is studied. Calculation shows that, at the ratio dipic2−: Pd(II) = 1: 1, the ligand decreases the redox potential of the Pd(II)/Pdmet system from 0.92 to 0.73–0.77, due to which Pd(II) is stabilized in reduced solutions of HPA-4. The reaction is first-order with respect to n-C4H8. Its order with respect to Pd(II) is slightly below unity, and its order with respect to HPA-4 is relatively low (∼0.63). The activation energy of but-1-ene oxidation in the temperature range from 40 to 80°C is 49.0 kJ/mol, and that of the oxidation of but-2-ene is 55.6 kJ/mol. The mechanism of the reaction involving the cis-diaqua complex [(H2O)2PdII(Hdipic)]+, which forms reversibly from complex I, is proposed. The reaction rate is shown to increase with an increase in the HPA-4 concentration due to an increase in the acidity of the solution.