Dawson-type polyoxometalates as green catalysts for adipic acid synthesis

Cyclohexanone Oxidation over H3PMo12O40 Heteropolyacid via Two Activation Modes Microwave Irradiation and Conventional Method

“…Preliminary catalytic tests carried out with powers of 100, 180, and 300 watt and reaction times varying between 5 and 60 min, have showed that 100 watt and 30 min are the best parameters to obtain optimal AA yield. While, previous works performed under conventional heating mode have showed that 20 h is the required reaction time to obtain optimal AA yield [14][15][16][22][23][24]. These results evidenced that the use of microwaves irradiation permits to reduce reaction time from 20 h to 30 min and to reduce energy.…”

“…This has as for consequence the formation of peroxocomplexes highlighted by several techniques (X-ray diffraction, FTIR, and Raman spectroscopies). These complexes, with an oxidizing power stronger than that of H2O2, have been shown to be very active in several reactions [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]29]. In our case, we could admit that the reduced POM, from the first stage, oxidizes and simultaneously forms peroxocomplexes "peroxo-POMox".…”

“…The reaction of cyclohexanone oxidation to adipic acid, using conventional method (reflux heating) in the presence of Keggin-type phosphomolydates, has already been the subject of several studies [14][15][16][22][23][24]. In this work, microwaves irradiation (MI), as new activation mode, was introduced to test the feasibility of this reaction using H3PMo12O40 (noted PMo12) as catalyst.…”

“…Hydrogen peroxide oxidizes in its turn the reduced POM to give "peroxo-POMox" species of yellow color indicating that the redox process is reversible. The peroxo-POMox" species could be the active species in the adipic acid formation [14][15][16]. It is noted that the protons necessary to the H2O2 reduction come from the POM.…”

Simple and Green Adipic Acid Synthesis from Cyclohexanone and/or Cyclohexanol Oxidation with Efficient (NH4)xHyMzPMo12O40 (M: Fe, Co, Ni) Catalysts

“…With transition-metalsubstituted POMs, it was reported that their remarkable catalytic activities were due to the multifunctional character of multimetallic active sites as simultaneous activation of oxidants and substrates, reaction intermediates stabilization, oxygen-transfer and multielectron transfer [15][16][17]. In previous studies, we have underlined the efficiency of transitionmetal-substituted POMs [18][19][20][21] as catalysts in the clean oxidation of cyclohexanone and mixture of cyclohexanone/cyclohexanol to adipic acid in the presence of hydrogen peroxide without solvent, phase-transfer agents and adding acid.…”