Transcript MS PowerPoint - Catalysis Eprints database

Transesterification of triglycerides with alcohols over
MoO3-Al2O3 catalysts
T.M.Sankaranarayananab, A.Panduranganb and S.Sivasanker a
aNational
Center for Catalysis Research ,IITM ,Chennai 600 036.
bDepartment of Chemistry, Anna University, Chennai 600 025.
NCCR 5th Annual Day 30th July 2011
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 COMPOSITION OF VEGETABLE OILS
O
H2C-O-C-R'
O
R’, R”, R’” = C12 to C20 groups
HC-O-C-R''
O
Fatty acid triglyceride
H2C-O-C-R'"
FA Comp.
Sunflower Rapeseed Cotton Soybean Rubber
/Canola
seed
seed
Palmitic C16.0
Stearic C18.0
Oleic C18.1
6.5
0.5
22.5
3.49
0.85
64.4
11.67
0.89
13.27
11.75
3.15
23.26
10.2
8.7
24.6
Linoleic C18.2 70.5
Linolenic C18.3 0
22.3
8.23
57.51
0
55.53
6.31
39.6
16.3
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BIODIESEL & BIOLUBRICANTS
Corn Soybean Animal
oil
fat
oil
TRIGLYCERIDE
Methanol Ethanol Octanol
ALCOHOL
TRANSESTERIFICATIOIN
Glycerol
BIODIESEL
BIOLUBRICANT
Methyl / Ethyl Fatty
Acid Esters
Octyl Fatty Acid
Esters
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 Advantages of Biodiesel over Diesel
•
•
•
•
•
•
•
•
Renewable; lowers dependence on petroleum
Biodegradable in water (98% in 3 weeks)
Negligible S & N compounds
Higher lubricity & cetane numbers (50-60)
Neutral to CO2 emissions
Can lead to rural revitalization
Higher flash point
Better industrial solvents for grease & resins (methyl & ethyl
soyates)
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 PROCESSES FOR BIODIESEL MANUFACTURE
• Homogeneous: COMMERCIAL. NaOH; 65°C; water
and acid washes; yields alkyl esters and glycerol.
• Enzymatic: Lipase; cost of enzyme is a major barrier.
Enzyme denatures in the presence of methanol;
requires additional solvent THF or hexane.
• Heterogeneous: Zn aluminates (Axens), Ca-carbonate,
ETS-4,-10, sulfated/tungstated zirconia.
• We now present our studies on the use of MoO3 supported
on alumina as a catalyst for the transesterification of
sunflower oil.
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 Experimental
Alumina extrudates
Impregnation/
Ammonium heptamolybdate
8, 12, 16wt% MoO3/
Dried/393K/12h
Calcined at 800, 950& 1100K/12h
In discussion, based on the amount of MoO3 impregnated and
calcination temperature, catalyst are noted as
eg., 8 wt % MoO3 loaded on - Al2O3 and calcined at 800K is
8Mo(Al)800,
16 wt% MoO3 loaded on -Al2O3 and calcined at 1100K is
16Mo(Al)1100.
 Reaction procedure and product analysis
SS batch reactor (Parr, USA; 300ml)
Different run durations (1 – 24h)
Different temperatures (343 – 383K)
Different amounts (0.5g to 2.0g).
SS high pressure down-flow fixed-bed reactor (i.d. 15 mm;
vol. 100ml)
30g catalyst (extrudates broken into 1-2 mm particles)
Two separate high pressure pumps were used for the feeds,
methanol and the oil.
The product was collected in a high pressure vessel,
transferred to a low pressure collector
Product Analysis (GC)
 Surface area and Acidity measurements
S.No
Catalysts
composition
Surface area
[m2/g]
1.
Al2O3 800
202
Total surface
acidity
[meq/g]
0.8
2.
Al2O3 950
150
0.61
3.
Al2O3 1100
116
0.53
4.
8 Mo(Al) 800
189
0.78
5.
8 Mo(Al) 950
134
0.42
6.
8 Mo(Al) 1100
52
0.24
7.
12 Mo(Al) 800
166
0.79
8.
12 Mo(Al) 950
96
0.55
9.
12 Mo(Al) 1100
43
0.15
10.
16 Mo(Al) 800
180
0.64
11.
16 Mo(Al) 950
59
0.33
12.
16 Mo(Al) 1100
25
0.09
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 The temperature programmed desorption-curves
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 Cumene Cracking Studies on 16% MoO3 /Alumina
In order to study the nature
of acidic sites, Cumene
cracking reaction has been
Carried out at 723K, it
shows that sample calcined
at 950K having some
bronsted acidity it mainly
due
to
the
polyoxo
molybednum oxides specie
on alumina surface at this
calcination temperature.
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 Powder XRD patterns of 16wt %MoO3-Al2O3
The XRD patterns of the
16%MoO3-alumina Calcined
at 800, 950 and 1100K are
presented in Fig. The XRD
lines have been examined with
the
help
of
JCPDS
(PCPDFWIN v.200) data to
identify the species present in
the samples.
( Al2O3, Mo13O33, Mo9O26,
Mo18O52,Al2(MoO4)3, MoO3).
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 Uv-Vis. spectra of 16wt %MoO3-Al2O3
There is a decrease in the
intensity of the bands with
calcination presumably due to
the formation of new specie with
lower extinction coefficients and
the loss of Mo on heating the
16% sample at 1100K.
Various
oxomolybdenum
compounds give absorption bands
in UV-Vis region due to ligand–
metal charge transfer (O2-  Mo6+).
The
position
of
this
electronic transition depends on the
ligand field symmetry surrounding
the Mo centre. For oxygen ligands,
a higher energy transition is
expected for tetrahedral Mo6+ than
for an octahedral one.
Absorption bands in the
range 250–280 nm have been
assigned to Mo(Td), and bands
from 300 to 330 nm have been
assigned to Mo(Oh)
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 Raman spectra of MoO3-Al2O3 samples
300 -500
1000
~950
~210
380
360
560
810
900
1030
~950
Raman spectroscopy is an
ideal tool to identify
individual specie present in
MoO3 supported on Al2O3.
The Raman spectra of
samples calcined at 950K
and recorded at room
temperature are presented
in this Figure, Which is
16% MoO3-Al2O3 calcined
at the three temperatures.
(a) 16Mo(Al)800, (b) 16Mo(Al)950,
(c) 16Mo(Al)1100
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 Effect of Mo-loading and calcination temperature on
conversion of triglycerides
A: calcined at (a) 800K (b) 950K and (c) 1100K;
B: Catalyst, 16Mo(Al)950 at run times of (a) 6h, (b) 12h and (c)
24h)
(Catalyst, 1g; 373K; Oil, 20g; MeOH/oil (mole), 9; Run duration,
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24h for A).
 Effect of reaction temperature
(Catalyst: 16Mo(Al)950, 1g; Oil, 20g; MeOH/oil (mole), 9).
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 Effect of run duration
(Catalyst: 16Mo(Al)950, 1g; 373K; Oil, 20g; MeOH/oil (mole), 9).
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 Catalyst reusability and Mo-leaching
Catalyst reusability (A) and Mo-leaching (B) (16Mo(Al)950,
1g; Temp.,373K; Oil, 20g; MeOH/oil (mole), 9;
Run duration, 24h).
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 High pressure fixed bed reactor studies
(A) and feed rate (B) on conversion
(a) Al950, (b) 8Mo(Al)950 (c) 12Mo(Al)950 and (d) 16Mo(Al)950
(A: Press. = 45 bars; WHSV (h-1), 0.5; MeOH/oil (mole), 9; B:
Press. = 45 bars; Temp., 533K; MeOH/oil (mole),
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 Influence of alcohol chain length on conversion and product
selectivity
(16Mo(Al)950;Press=45 bars;
Temp., 533K;
WHSV (h-1), 0.5; MeOH/oil
(mole), 9).
Decrease in the conversion of TG with an increase in chain length
of alcohol. This is because of increasing the diffusional issues and
dilution effect with increasing molar mass of alcohols.
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 Influence of time on stream on conversion
(16Mo(Al)950; Press. = 45 bars; Temp., 533K;
WHSV (h-1), 0.5; MeOH/oil (mole), 9).
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 Conclusions
 MoO3 supported on -Al2O3 is active in the transesterification
of sunflower oil with alcohols
 MoO3 loading and calcination temperature affect the activity
of the catalyst; activity increases with Mo-loading, but goes
through a maximum at a calcination temperature of 950K.
 The reasons for the good performance of this catalyst are the
presence of the active polyoxo molybdenum species.
 The catalyst is suitable for use in a continuous fixed-bed process.
Thank you
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