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S. Mouanni et al. / C. R. Chimie xxx (xxxx) xxx
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Mots cles:
Les heteropolysels H3ꢀ2(xþy)MnxCoyPMo12O40 (x þ y ꢁ3/2 et x, y: 0e1,5) ont ete prepares par
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une methode d'echange cationique basee sur la precipitation du sulfate de baryum. Les
Cobalt
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Phosphomolybdates de manganese
Oxydation de la cyclohexanone
proprietes structurales et texturales des sels ont ete examinees par plusieurs techniques
physico-chimiques telles que les spectroscopies IR, MEB/EDX et RMN 31P, la diffraction
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Peroxyde d'hydrogene
des rayons X et l'analyse TG. Leurs proprietes catalytiques ont ete evaluees dans l'oxydation de
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Acide adipique
la cyclohexanone en utilisant le peroxyde d'hydrogene (30%). Les produits de la reaction,
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acides adipique, glutarique, succinique, hexanoïque, 6-hydroxyhexanoïque, 7,7-dimethoxy,
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heptanoïque et 1,1-dimethoxy octane, ont ete identifies par analyse GC-MS. Seuls les acides
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adipique, glutarique et succinique ont ete quantifies par chromatographie (HPLC), les autres
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produits ont ete notes X. L'acide adipique (AA) est le principal produit de la reaction. Les
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effets des rapports molaires catalyseur/reactif et cyclohexanol/cyclohexanone, de la compo-
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sition du sel et du temps de reaction sur le rendement en AA ont ete etudies. La stabilite du
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systeme catalytique a egalement ete examinee. Les catalyseurs H3ꢀ2(xþy)MnxCoyPMo12O40 se
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sont reveles etre efficaces pour l'oxydation de la cyclohexanone avec des conversions >95%.
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Parmi eux, H1Mn0.25Co0.75 conduit au rendement le plus eleve en AA (75%).
© 2019 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
H3ꢀ2xNixPMo12O40 and (NH4)3ꢀ2xNixPMo12O40 [37],
(NH4)xAyPMo12O40 (Anþ
¼
Sb3þ
,
Bi3þ
,
or Sn2þ
)
[38],
2-K6P2Mo5W13O62
1-K7P2Mo5VW12O62 [40]. They
showed high activities and led to high AA yields. Seventy
One of the major drawbacks in the actual adipic acid
(AA) production process is the N2O emission [1e3]. It is one
of the ozone depleting agents with a strong greenhouse
effect and a very long residence time in the atmosphere,
thus leading to serious environmental problems [4,5].
AA is an important raw material for nylon-6,6 produc-
tion [6,7] and other compounds as synthetic fibers and fine
chemicals [1]. It is usually produced via the oxidation of a
mixture of cyclohexanone and cyclohexanol (KA oil) in the
presence of an excess of HNO3 (40e60%) using CuII/NH4VO3
as a catalyst [1,5]. The HNO3 reduction causes inevitably the
release of nitrous oxides (N2O, NO, and NO2), which are
harmful gases. Others powerful oxidants as Na2Cr2O7,
NaClO, MnO2, KMnO4 are cited in the literature [8e14], but
they are noxious too. Therefore, the development of a
process that would belong to the “green chemistry” domain
is more than necessary. So, several studies have focused on
the search for benign oxidants for environment as H2O2, O2,
and air. Among them, hydrogen peroxide is the most used,
easier to handle, and moreover, its reduction leads only to
water. It was used for KA oil production from cyclohexane
oxidation using transition metal based catalysts as Cu/
Cr2O3 [15], CoFe2O4 [16], Co3O4 [17], Ce1ꢀxMnxO2 [18], Cu/
Co/AC [19], WO3/V2O5 [20], HMS [21], MCM-48 [22], Cu/
Cr2O3, AlPO-5 modified with rare earth elements [23,24],
and A-HMS (A ¼ Ce, Ti, Co, Al, Cr, V, and Zr) [21] and
MnAlPO [25]. It was found that the most effective systems
for cyclohexane oxidation are those based on Mn and Co
elements [26,27].
H3ꢀ2xCoxPMo12O40 (x: 0e1.5) [39], and
-K6P2Mo6W12O62, and
a
,
a
a
percent of AA yield was attained with
from the mixture of ol/one oxidation.
a-K6P2Mo6W12O62
On the basis of the literature highlighting the efficiency
of Mn- and Co-based catalysts for the oxidation of cyclo-
hexane, in this study, we propose to introduce these two
elements as counterion of [PMo12O40
POMs of formula 3ꢀ2(xþy)MnxCoyPMo12O40, noted
]
3ꢀ. So, a series of
H
H3ꢀ2(xþy)MnxCoy (x þ y ꢁ 3/2 and x, y: 0e1.5) were pre-
pared, characterized by several physicochemical tech-
niques (infrared [IR], scanning electron microscopy-energy
dispersive X-ray [SEM/EDX], and 31P nuclear magnetic
resonance [NMR] spectroscopies, X-ray diffraction [XRD]
diffraction, and thermogravimetric analysis [TGA]) and
used as catalysts for the oxidation of cyclohexanone using
hydrogen peroxide (30%) as an oxidant. The reaction
products, AA, glutaric acid (GA), succinic acid (SA), hex-
anoic, 6-hydroxyhexanoic, 7,7-dimethoxy, and heptanoic
acids and 1,1-dimethoxy octane were identified by gas
chromatographyemass spectrometry (GCeMS) analysis.
Only AA, GA, and SA were quantified by high-performance
liquid chromatography (HPLC), the other products were
noted X. The effects of POMs' counterion nature, molar
ratios of catalyst/-one and cyclohexanone/cyclohexanol,
and reaction time on the reaction product distribution were
investigated. The used catalysts were analyzed by 31P NMR.
H1Mn0.25Co0.75PMo12O40 catalytic stability was examined
in five consecutive cycles.
Furthermore, polyoxometalates (POMs) have received
great attention in the catalysis field because of their
multifunctional properties. They were extensively studied
for various reactions as olefin epoxidation [28], organo-
silane oxidation [29], organic pollutant photo-oxidative
degradation [30], oxidation of alcohols [31e33], cyclo-
hexane [34,35], and cyclohexanol/cyclohexanone [36e40].
In this last case, the examined catalytic systems are
MxPMo12O40 (M ¼ Fe, Ni, Co and x ¼ 1 or 1.5) [36],
2. Experimental section
2.1. Material synthesis
H3PMo12O40 heteropolyacid (noted H3PMo12) was pre-
pared according to the classical method described by
Tsigdinos [41].
H3ꢀ2(xþy)MnxCoy mixed heteropolysalts
Please cite this article as: S. Mouanni et al., Preparation and characterization of H3ꢀ2(xþy)MnxCoyPMo12O40 heteropolysalts.
Application to adipic acid green synthesis from cyclohexanone oxidation with hydrogen peroxide, Comptes Rendus Chimie,