SuSChemE 2015
International Conference on Sustainable Chemistry and Engineering
October 8-9, 2015, Hotel Lalit, Mumbai
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Efficient LPO over triple nanocomposite of rGO and Mn-Co Oxides
Bhanu P. Solanki, Ajay Jha, Chandrashekhar V. Rode*
Chemical Engineering and Process development, CSIR National chemical Laboratory, Pune (India)
bp.solanki@ncl.res.in jhajincl@gmail.com cv.rode@ncl.res.in
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1. Introduction
A novel triple nanocomposite of reduced graphene oxide (rGO) with mixed oxides of Mn and Co was developed for the first
time as a solid catalyst for liquid phase oxidation of p-cresol [1]. p-cresol oxidation is a challenging reaction because of
formation of several oxidation products such as p-hydroxybenzylalcohol (PHBAlc), p-hydroxybenzaldehyde (PHBAld) and
p-hydroxybenzoic acid (PHBAcid).
2. Material and Methods
All materials used in this work were purchased from Sigma Aldrich, India.
2.1 Preparation of catalyst
A modified Hummer’s method was used to synthesize GO [2]. r-GO–MnCo nanocomposite was synthesized by solvothermal
method.
2.2 Catalytic Reaction
p-cresol (6.0g), NaOH (6.2g) and methanol (50mL) heated in a round bottomed flask fitted with a reflux condenser until all
NaOH dissolved completely. This reaction mixture was taken in a 300 mL parr autoclave. Then, the catalyst (0.2g) added
and heated to 373K.The reactor was pressurised with Oxygen (2.7 bar) and reaction started by agitating at 1000 rpm. When
the pressure decreased, the reactor was again filled with oxygen. The progress of the reaction was monitored by observing
the pressure drop in reactor as a function of time. After 2 h, the reactor was cooled and the liquid samples were analysed by
HPLC.
3. Significant Results and Discussion
3.1 Characterization
XPS, pXRD and CV were used for characterization of the prepared material. Diffraction peaks in pXRD of MnCo (MO)
confirmed the formation of 3 different spinel oxides (Fig. 1 A), viz. tetragonal CoMn2O4, Mn3O4 and cubic Co3O4. Peaks
due to r-GO-MnCo remained unchanged however, the peak intensities reduced after the formation of nanocomposite
suggesting decrease in the crystallite size. XPS peak of GO and r-GO-MnCo showed the reduction of the oxygen containing
functional group during the synthesis of the catalyst. The unsymmetrical 2p3/2 peak of Co in r-GO-MnCo showed the
presence of Co3+of Co2O3, Co2+ of CoMn2O4 and Co3O4. Broad peak of Mn2p3/2 revealed Mn2+, Mn3+ and Mn4+ of Co2MnO4
and Mn3O4. In CyclicVoltammetry (Fig. 1 B), r-GO-MnCo showed 2 sharp reduction peaks. Higher potential value (0.2V),
showed reduction of Mn3+ to Mn2+ and the lower one (-0.55V) reveal further reduction of Mn2+ and Co2+ to Mn and Co
A
B
1
SuSChemE 2015
International Conference on Sustainable Chemistry and Engineering
October 8-9, 2015, Hotel Lalit, Mumbai
___________________________________________________________________________________________________
Figure: 1. (A) XRD patterns and (B) CV curves of a) MnCo MO and b) r-GO–MnCo.
3.2 Catalyst activity
Scheme 1. P-cresol oxidation
Various catalysts were screened for p-cresol oxidation (Scheme 1) and the results are shown in Table1. It was reported that
a minimum ratio of NaOH/p-cresol is required for oxidation reaction [3]. Among all the catalyst r-GO-MnCo (1:1) showed an
excellent activity giving 71% yield of PHBAld with 96% selectivity.
Table1: Catalyst screening for p-cresol oxidation
Sr.No.
Catalyst
Yield
Selectivity [%]
[%]
PHBAlc PHBAld PHBAcid
1
2
3
4
5
6
7
8
9
r-GO-Co
r-GO-Mn
MnCo(1:1)
r-GO-MnCo(1:1)
r-GO-MnCo(1:2)
r-GO-MnCo(2:1)
r-GO-MnCo(1:1)
MnCo(1:1)/SiO2
MnCo(1:1)/Al2O3
20
28
42
71
57
60
NR[a]
9
31
100
1
1
PHBEth
89
10
1
95
96
97
95
3
3
2
3
1
1
1
1
93
93
6
6
1
1
[a] NR= No reaction(reaction performed without base)
4. Conclusion:
Triple nanocomposite catalyst, r-GO-MnCo proved highly efficient for the selective liquid oxidation of p-cresol to PHBAld
with a product yield of 71% and > 96% selectivity in 1 h.
References
[1] A. Jha, Sagar H. Patil, Bhanu P. Solanki , C.V. Rode, ChemPlusChem 2015,80, 1164-1169
[2] W. S. Hummers and R. E. Offeman, J. Am. Chem. Soc., 1958,80, 1339.
[3] C.V.Rode, M.V. Sonar, J.M. Nadgeri, Org. Process Res. Dev. 2004,8,873-878
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