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4275639 
Journal Article 
Dicationic ionic liquids/heteropoly acid composites as heterogeneous catalysts for cyclohexene oxidation with molecular oxygen under solvent-free condition: Insights from theory and experiments 
Nezampour, F; Ghiaci, M; Farrokhpour, H 
2017 
1 
Applied Catalysis A: General
ISSN: 0926-860X
EISSN: 1873-3875 
543 
104-114 
WOS:000407403400013 
This study describes solvent-free oxidation of cyclohexene using dicationic ionic liquids (DIL)/heteropoly acid (HPA) composites with molecular oxygen. Structural characterization of the DIL/HPA composites was carried out by different techniques such as ICP, FT-IR, H-1 NMR, BET, TGA, XRD, FESEM, EDX and TEM. Characterization results confirmed that heteropoly acids i.e., tungstophosphoric (H3PW12O40, TPA) and molybdophosphoric acid (H3PMo12O40, MPA) were incorporated with DILs without distortion of the Keggin structure of the heteropoly acids. Two different dicationic ionic liquids with linear and aromatic linkage, DIL-L and DIL-A, were prepared and applied for synthesis of the composites. Effective parameters including the effect of temperature, time, oxygen pressure, amount of the selected catalyst, i.e., DIL-L/tungstophosphoric acid was thoroughly investigated. The catalyst was found to be stable and recyclable. The main product of the reaction was cyclohexene-2-one (Cy-one) at 70 degrees C and 15 bar oxygen pressure after 6 h. Additionally, theoretical calculations at the PM6 semi-empirical method was performed on DILs/HPA complexes with different number of DIL molecules to explore the capacity of HPA in interaction with DILs and obtained the orientations of DILs around the Keggin oxoanion of the HPA. The calculations showed that the maximum number of DIL molecules around the [H2PW12O40](-) oxoanion was five and the interaction of DIL-L with the oxoanion was stronger than that of DIL-A which was in agreement with the experimental data. 
Oxidation; Cyclohexene; Heteropolyacid; Dicationic ionic liquid; Bis(imidazolium)compounds; Heterogeneous catalyst