Comparison of liquid-phase olefin epoxidation catalysed by dichlorobis-(dimethylformamide)dioxomolybdenum(VI) in homogeneous phase and grafted onto MCM-41
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- 作者：Bernardo Monteiro ; Salete S. Balula ; S ; ra Gago ; Carla Grosso ; Só ; nia Figueiredo ; André ; D. Lopes ; Anabela A. Valente ; Martyn Pillinger ; Joã ; o P. Lourenç ; o ; Isabel S. Gonç ; alves
- 关键词：Mesoporous materials ; EXAFS ; Molybdenum ; Oxidation ; Heterogeneous catalysis
- 刊名：Journal of Molecular Catalysis A: Chemical
- 出版年：2009
- 出版时间：14 January 2009
- 年：2009
- 卷：297
- 期：2
- 页码：110-117
- 全文大小：294 K
文摘
A mesoporous silica-supported molybdenum oxide catalyst with a loading of 0.17 Mo/nm2 was prepared by liquid phase deposition of MoO2Cl2(dmf)2 (1) onto MCM-41 (dmf = dimethylformamide). Powder X-ray diffraction and N2 adsorption studies of Mo-MCM-41 indicate that the texture properties of the support were preserved during the grafting experiment. On the basis of evidence from FTIR spectroscopy, 13C and 29Si MAS NMR, and Mo K-edge EXAFS, the Mo atoms in this catalyst are mainly present as isolated {MoO2[(–O)3SiO]2(dmf)2} species, with a small contribution from oxo-bridged dimers. Catalysis tests show that complex 1 and Mo-MCM-41 are highly active oxidation catalysts for liquid-phase epoxidation of unfunctionalised olefins using tert-butylhydroperoxide as oxidant, from ambient to 55 °C. The high stability and recyclability of the heterogeneous Mo-MCM-41 catalyst is attributed to the strong metal oxide–support interaction. With cyclooctene, 1-octene, trans-2-octene and norbornene substrates, the corresponding epoxides were the only observed reaction products. The reactions of the other substrates gave by-products such as 8,9-p-menthen-1,2-diol from (R)-(+)-limonene, campholenic aldehyde from α-pinene, and benzaldehyde from styrene. The addition of dichloromethane as a co-solvent had a beneficial effect on catalytic performance, and in the case of (R)-(+)-limonene allowed the epoxide to be formed as the only reaction product.