Phosphoric acid grafted MCM-41 is a novel Bronsted acid
catalyst for Transesterification reaction of Diethyl oxalate
with n-Butyl alcohol
By
D. Nedumaran and A. Pandurangan
Institute of Catalysis and Petroleum Technology
Anna University
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Chennai-600025
Introduction
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CATALYSIS
•Catalysts - a chemical substance which increase the rate of
chemical reaction
•Catalysis - a study of catalytic activity of a chemical reaction
•Homogeneous Catalyst – substrate and catalyst are in same
phase
•Disadvantages of Homogeneous catalyst –
Homogeneous catalyst like sulfuric acid is still the catalyst of
choice in the industry, together with HCl, dissolved aryl sulfonic
acids and H3PO4
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•But these catalysts are toxic, corrosive substances, polluting the
environment and often hard to remove from the reaction mixture for
recycling
•Heterogeneous catalyst – substrate and catalyst are in different phase.
Generally catalyst in solid phase. Substrate may be in liquid or gas
phase
•Advantages of heterogeneous catalyst Ecofriendly, non corrosive, non toxic, recyclable, reusable.
It leads to green chemistry.
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Materials
Activated
charcoal; Mica
Hexagonal
Microporous
5
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10
Cubic
Mesoporous
50
100
Lamellar
Macroporous
50
0
1000
Salient Features of mesoporous
MCM-41
High surface area (>1000m2/g)
Tunable and large pore size (20 to 100 Å)
Ordered pore morphology
Thermal stability up to 800 °C in dry
atmosphere
Higher Hydrothermal stability
Hydrocarbon sorption capacity > 0.7 ml/g
Reusability , Recyclable
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Main Objectives:
To synthesis MCM-41 molecular
hydrothermal crystallization procedure
sieves
by
adopting
the
To characterize the catalysts by various physicochemical techniques.
To test the catalytic activity of the synthesized materials over the
Transesterification reaction of Diethyl oxalate with n-Butyl alcohol
Optimize various reaction parameters for maximum substrate
conversion.
Study the reusability of the catalysts
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Experimental
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SYNTHESIS OF MCM-41
Silicon source
1 hour stirring
Mixture
1 M H2SO4 till gel formation
Gel
30 min stirring
CTAB
Resultant gel
Autoclaved and heated for
48 hours at 145ºC in oven
product
Calcined at 550ºC in
furnace for 6 hours
MCM-41
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SYNTHESIS OF ORTHO PHOSPHORIC ACID
GRAFTED MCM-41
• 1 g of MCM-41 is dissolved in 10 ml deionized water and stirred for
15 minutes.
• 0.2N Ortho Phosphoric acid is added drop wise and Stirred for 30
minutes followed by drying for 6 hr at 110 °C
• After drying ,this material is Calcined at 300 °C for 4 hr.
• This dry material is labeled as PAM 0.2.
• The same method is used to synthesis PAM 0.4, PAM 0.6 and
PAM 0.8
• The catalytic activity of PAM is examined with Trans
esterification reaction.
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GRAFTING OF PHOSPHORUS SPECIES ON
MCM-41
OH
OH
P
P
HO
OH
Si
MCM-41
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OH
OH
O
O
Si
MCM - 41
O
Characterization
The following physicochemical properties of PAM have
to be done
BET – surface area
Pyridine FT-IR – measurement of acid sites
_
FT-IR – different OH groups
XPES – Binding energy of 2p e- of Phosphorus
ICP – Si-P ratio
NH3 – TPD – adsorption profile
N2 adsorption – pore sizes
P MAS NMR – Phosphorus environment
TEM – morphological feature
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Intensity (a.u)
X-ray diffraction pattern of PAM molecular
sieves obtained after calcination
(a)
(b)
(c)
(d)
(e)
2
4
6
8
10
2 theta (deg)
a) Si-MCM-41, b) PAM 0.2, c) PAM 0.4, d) PAM 0.6, e) PAM 0.8
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NH3-TPD
PAM 0.6
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Reaction procedure
A mixture of Diethyl oxalate (5mmol),
n-Butyl alcohol (15mmol).
Freshly activated catalyst (150 mg).
The reactants and the catalyst were taken in
15 ml autoclave and kept it in a Hot air
oven for specified temperature and time.
The product thus obtained was analyzed by
Gas chromatography.
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Proposed Mechanism
+
H oo
o o
C2H5O-C-C-OC 2H5
H+
C2H5O-C-C-OC 2H5
DEO
n-Bu
H oo
C2H5O-C-C-OC 2H5
H-O-C 4H9
+
oo
C-C-OC 2H5 + C2H5OH
O-C4H9
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BEO
H oo
C2H5O-C-C-OC 2H5
HO-C 4H9
+
The effect of various catalysts on
Transesterification reaction
Selectivity (%)
S.No.
Catalyst
1
PAM 0.2
%Conver
sion of
DEO
MONO
ESTER
DIESTER
82.7
56.4
43.6
90.3
49.2
50.8
96.8
40.1
59.9
92.2
32.9
67.1
PAM 0.4
2
PAM 0.6
3
4
PAM 0.8
Reaction conditions: Temp 130 °C, Mole ratio 1:3, Time 3h. Wt.of
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The effect of temperature on
Transesterification reaction
Selectivity (%)
S.No.
Temp. (°C)
1
70
2
%Conver
sion of
DEO
MONO
ESTER
DIESTER
66.7
56.2
43.8
100
71.0
44.3
55.7
3
130
96.2
33.7
66.3
4
150
84.2
27.6
72.4
5
180
80.1
21.0
79.0
Reaction conditions: Catalyst PAM 0.6, Mole ratio 1:3, Time 3h, Wt.of
catalyst 100 mg.
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The effect of time on Transesterification
reaction
Selectivity (%)
S.No.
Time (h)
1
1
2
%Conversio
n of DEO
MONO
ESTER
DIESTER
68.2
51.7
48.3
2
83.6
48.3
51.7
3
3
94.5
41.5
58.5
4
4
94.9
33.1
66.9
5
5
95.4
23.7
76.3
Reaction conditions: Catalyst PAM 0.6, Mole ratio 1:3, Wt.of catalyst
100 mg.
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Conclusion
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Si-MCM-41 was synthesized by hydrothermal method.
Various concentration ratio of orthophosphoric acid is loaded
on Si–MCM-4.
All synthesized mesoporous PAM were found to be typical mesoporous
materials.
XRD investigation shows that the intensity of 100 plane is well retained upto
the optimum loading of PA (0.6 N).
NH3-TPD of the material shows the presence of acid sites while loading PA
on Si-MCM-41.
PAM is the suitable solid acid catalysts for the trans esterification reaction.
The product analysis shows Bronsted acid sites are the reason for absence of
ether product (Butyl ethyl ether).
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