Continuous Synthesis and Separation of Glycerol
Acetates Using Supercritical Carbon Dioxide as a
Benign Solvent
1

Introduction
• Supercritical Fluids
• SCCO2 Properties
• Chemical Reaction in SC-CO2
• Extraction & Separation by SC-CO2
•

Glycerol acetates
Experimental
• Synthesis of acetins
• Separation using SCCO2

Conclusion
2
3
4
Phase diagram for pure CO2
Pressure (bar)
SOLID
SUPERCRITICAL
Critical
FLUID
•
point
74
LIQUID
Triple
point
•
5.1
GAS
1
-78 ºC
-56.3ºC
31.1ºC
Temperature (ºC)
5
Low Density
and Viscosity
Heat
transfer
6
7

Effect of extraction parameters:
• Pressure and Temperature
• Difference in density between the
liquid and SC-CO2
• Time
• Feed/Solvent
8
9
10
+ 3CH 3OH
R2OCOHC
HOHC
+
CH2OH
CH 2OCOR1
Triglyceride
CH 3OCOR1
CH2OH
CH 2OCOR3
Methanol
Glycerol
CH 3OCOR2
CH 3OCOR3
Methyl esters
(biodiesel)
11
Monoacetin
(MA)
Acetic acid
Acid Catalyst
Glycerol +
Acetic anhydride
Diacetin
(DA)
Organic Solvent
Triacetin
(TA)
Colored
Odorous
Problems
Impure
12
OH
OH +
HO
Acetic acid
Glycerol
OH
HO
OCOCH3
HO
+
OCOCH3
HO
OH
Monoacetylglycerol
(MA)
CH3COOH
OCOCH3
OCOCH3
+ H3COCO
OH
H3COCO
OCOCH3
OCOCH3
+ H 2O
OCOCH3
Diacetylglycerol
(DA)
Triacetylglycerol
(TA)
13
Continuous Flow Reactor
14









CO2 (99.95%)
Glycerol (>98%)
Acetic acid (99-100%)
Absolute Ethanol (>99.0%)
1-hexanol (Riedel-deHaën)
Triacetin (99.0%)
Diacetin (50%)
Monoaectin (synthesized)
Amberlyst15®
15
HO
OH
PTSA
Acetone - CHCl3
OH
H 3C
O
H 3C
O
OH
2
1
(AcO)2O
O
O
HO
HO
O
CH 3
AcOH 70%
H 3C
H 3C
Monoacetin
O
O
CH 3
O
3
16
Yield =
Total moles of detected esters
Moles of glycerol in feed solution
Conversion =
Selectivity =
× 100
Total moles of detected esters
× 100
Moles of detected esters and glycerol in exit flow
Moles of each ester
× 100
Total moles of detected esters in exit flow
17
18






Pressure
Temperature
Molar ratio (Acetic acid/Glycerol)
Flow rate
Reactor geometry
Time
Glycerol
HO
k1
HO
CH3COOH
OCOCH 3
H 3COCO
k2
H3COCO
OCOCH 3
k3
OH
OH
OH
HO
Triacetin
Diacetin
Monoacetin
HO
H 3COCO
OH
OCOCH 3
CH3COOH
CH3COOH
H 3COCO
OH
H3COCO
OCOCH 3
19
100
100
40
20
0
0
50
100
150
65 bar
80 bar
150 bar
200 bar
250 bar
300 bar
80
60
40
20
0
200
0
50
100
Time / min
150
200
Time / min
100
Monoacetin Selectivity/%
Triacetin Selectivity/%
60
Diacetin Selectivity/%
300 bar
250 bar
200 bar
150 bar
80 bar
65 bar
80
80
60
65 bar
80 bar
150 bar
200 bar
250 bar
300 bar
40
20
0
0
50
100
150
200
Time/min
20
100
Selectivity, Conversion or Yield / %
Conversion / %
Yield / %
80
MA Selectivity
DA Selectivity
60
TA Selectivity
40
20
0
65
80
150
200
250
300
Pressure /bar
21
Selectivity, Conversion or Yield / %
100
Conversion / %
Yield / %
MA
DA
TA
80
60
40
20
0
100
120
140
Temperature /°C
150
22
Selectivity, Yield or Converstion / %
100
Conversion / %
Yield / %
80
TA
DA
60
MA
40
20
0
1.5
4.5
6
12
18
24
Substrates molar ratio (acid/glycerol)
23
Reactor Length (cm) Conversion (%)
25
100
100
100
Condition Conversion (%)
1a
35
2b
100
Yield (%)
29
41
Yield (%)
41
48
TA (%)
0
100
TA (%) DA (%) MA (%)
100
0
0
82
19
0
DA (%)
0
0
MA (%)
100
0
A
without catalyst
b with catalyst
24
Times catalyst
recycled
Conversion (%)
3a
100
3b
100
Yield (%)
82
49
TA (%)
27
92
DA (%)
42
8
MA (%)
31
0
a acid/glycerol
ratio was 6.0.
b acid/glycerol ratio was 24.
Yield / %
Selectivity or Yield / %
100
TA
DA
80
60
40
20
0
0.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
Time/h
25
Yield%
TA%
DA%
Selectivity or Yield / %
100
Acetic acid/Glycerol= 30
80
60
40
20
0
0.0
2.0
4.0
6.0
8.0
10.0
Time/h
Yield%
TA%
DA%
Acetic acid/Glycerol= 40
Selectivity or Yield / %
100
80
60
40
20
0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Time/h
26
TA%
DA%
100
Selectivity / %
80
60
40
20
0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Time/h
27
Flow rate= 3.0 mL.min-1
Yield%
TA%
DA%
Selectivity or Yield / %
100
80
60
40
20
0
0.0
2.0
4.0
6.0
8.0
10.0
Time / h
28
29



Catalyst bed: 4 mm (i. d.), 25 cm (length)
T = 110 °C
Flow rateSub.=0.2 mL.min-1
30
Flow rate= 1.1 mL.min-1
Molar ratio= 24
Selectivity or Yield / %
Yield%
TA
DA
100
80
60
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Time / h
Yield %
DA
100
Selectivity or Yield / %
Flow rate= 1.5 mL.min-1
Molar ratio= 24
TA
80
60
40
20
0
0.0
1.0
2.0
Time / h
3.0
4.0
31
Yield%
Flow rate= 1.1
Molar ratio= 30
80
60
40
20
0
Selectivity or Yield / %
0.0
Flow rate= 2.0 mL.min-1
Molar ratio= 30
DA%
100
Selectivity ot Yield/ %
mL.min-1
TA%
1.0
2.0
3.0
Time / h
TA
4.0
DA
5.0
Yield
100
80
60
40
20
0
0.0
1.0
2.0
3.0
Time / h
4.0
5.0
32
% Selectivity and Yield of the Reaction at different CO2
Flow Rates and Molar Ratio of 30 vs. Time Using Silica
Sulfuric Acid as Catalyst at Pressure of 250 bar
Yield
TA
DA
100
Selectivity or Yield / %

80
60
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Time / h
33
34





T = 110 °C
P = 200 bar
Molar ratio = 24
1 g catalyst was dispersed within crushed glass (~12 g)
Catalyst bed = 9 mm i. d., 15 cm long
Catalyst
H-ZSM-5(30)
H-ZSM-5(170)
Conversion (%)
75
92
Yield (%) TA (%)
31
0
51
0
DA (%) MA (%)
2
97
8
92
35
Catalyst bed: 4 mm (i. d.), 25 cm (length)
Selectivity or Yield or Conversion / %
Catalyst
H-ZSM-5(80)
H-ZSM-5(120)
Conversion (%)
57
100
Yield (%) TA (%)
43
0
43
0
DA (%) MA (%)
0
100
0
100
MA
Yield%
Conversion%
100
80
60
40
20
0
0
50
100
150
200
250
Time / min
36
N
HSO4
N
H
H3C
37





T = 110 °C
P = 200 bar
Molar ratio = 24 and 30
Catalyst dispersed on SiO2
Catalyst bed = 4 mm i. d., 25 cm long
38
DA
Yield%
MA
Selectivity or Yield / %
100
80
60
40
20
0
0
50
100
150
200
Time / min
39
DA
Yield
Selectivity or Yield / %
100
80
60
40
20
0
0
50
100
Time / min
150
200
40
DA
Yield
Selectivity or Yield / %
100
80
60
40
20
0
0
50
100
150
200
Time / min
41
Conclusion:








• Gly.
• AcOH
-H2O
-H2O
• AcOH
• MA
Pressure
The molar ratio of acetic acid to glycerol
CO2 flow rate
Substrates flow rate
TA synthesized selectively (100%)
MA synthesized selectively(100%)
MA synthesized selectively (<100%)
DA Synthesized selectively (100%)
• DA
TA
• AcOH
-H2O
Without
Catalyst
H-ZSM-5(x)
[x= 30 , 170]
IL , Methyl imidazolium
[HSO4]
42
Selective extraction of TA from a mixture of TA, DA, and
MA with the composition of 1:2:1 molar
43
The standard mixture of
TA, DA and MA ( 1:2:1)
Extraction yield (Y):
Selectivity (S):
%Y = (wext/w0) × 100
S = (YA/YB)
44
k
k
i j
i 1
i 1
i
Y  b0   bi xi   bii xi2   bij xi x j  e
j
Range of selected levels for four variables in the semi-continuous SFE process
Variables
Low level (-1)
Medium level (0) High level (+1)
P (bar)
100
120
140
T (oC)
48
60
72
f (mL·min-1)a
0.5
0.8
1.1
t (min)
30
45
70
a
Liquid CO2 flow rate at 60 bar and 0°C.
45
100
80
Predicted values / %
Predicted values / %
100
60
40
R2 = 0.9653
20
80
60
40
R2 = 0.9364
20
0
0
0
20
40
60
80
100
Experimental values / %
P = 140 bar
T = 48 °C
f = 1.1 mL·min-1
t = 60 min
The maximum
extraction yield
0
20
40
60
80
100
Experimental values /%
TA = 95.6%
DA = 96.9%
46
Regression coefficients, t-test, and significance p-values for the model estimated by Minitab
software.
Term
Constant
%DA
Coefficient
t-value
%TA
p-value
Coefficient
t-value
p-value
128.401
1.269
0.224
-157.482
-1.388
0.185
P (bar)
-1.180
-1.046
0.312
1.885
1.490
0.157
T (°C)
-1.448
-0.969
0.348
0.520
-0.310
0.761
-45.396
-0.855
0.406
48.278
0.811
0.430
t (min)
-0.848
-0.788
0.443
2.300
1.905
0.076
P2 (bar)2
0.012
2.754
0.015
-0.013
-2.689
0.017
T2 (°C)2
0.048
5.328
0.000
-0.016
-1.557
0.140
f2 (mL·min-1)2
2.579
0.179
0.860
-26.138
-1.619
0.126
t (min)2
-0.001
-0.239
0.814
-0.010
-1.551
0.142
P (bar)*T (°C)
-0.037
-5.147
0.000
0.020
2.569
0.021
P (bar)*f (mL·min-1)
1.057
3.714
0.002
0.780
2.443
0.027
P (bar)*t (min)
0.015
2.711
0.016
0.005
0.842
0.413
T (°C)*f (mL·min-1)
-1.043
-2.198
0.044
-0.689
-1.295
0.215
T (°C)*t (min)
-0.009
-0.978
0.343
-0.018
-1.707
0.108
f (mL·min-1)*t (min)
0.134
0.345
0.728
-0.387
-0.910
0.377
f (mL·min-1)
47
Response Optimizer Tools
P = 109 bar
T = 56 °C
f = 0.86 mL·min-1
t = 61 min
TA =62%
DA=17%
48
Response Surface Plots of DA and TA % Extraction Yield
(a)
f = 0.86 mL.min-1
t = 61.0 min
150
100
100
% TA
% DA
50
50
0
0
80
100
120
P (bar)
0.5
140
1.5
1.0
f (mL/min)
-50
35
160
45
55
65
75
T (°C)
85
160
140
120
100 P (bar)
80
(b)
T = 56.0 °C
t = 61.0 min
150
100
100
% DA
% TA
50
50
1.5
0
80 100
120
P (bar)
140 160
1.0
0.5 f (mL/min)
1.5
1.0
0.5 f (mL/min)
0
80 100
120
140 160
P (bar)
49
Practicable Region of The DA and TA % Extraction Yield
(a)
160
DA
150
140
130
120
10
110
100
90
80
40
50
60
70
80
T (°C)
(b)
160
150
140
100
P (bar)
P (bar)
f = 0.86 mL.min-1
t = 61.0 min
95
TA
130
120
110
10
100
90
80
40
50
60
70
80
T(°C)
50
The standard mixture:
TA, DA , MA
( 1:2:1)
51
Recovery a
Compound extracted(g)
P
f
Feed
Extracted
(bar)
(mL/min)
(g)
(g)
TA
DA
MA
TA
DA
MA
1
140
0.86
7.137
0.650
0.5740
0.0800
N.D.b
28.69
2.24
0.00
18
2
140
1.5
7.020
0.889
0.8224
0.1072
N.D.
41.79
3.05
0.00
23
3
100
1.5
7.020
0.130
0.0890
0.0305
0.0050
4.52
0.87
0.33
5
4
109
1.5
7.371
0.288
0.2242
0.0508
N.D.
10.85
1.38
0.00
9
5
109
0.86
7.020
0.124
0.1042
0.0233
N.D.
5.29
0.66
0.00
8
6
100
0.86
7.254
0.093
0.0607
0.0220
0.0039
2.98
0.61
0.25
5
Run
a
b
c
Sc
Recovery is the weight percent of recovered compound by scCO2 to the original weight % in the feed.
N.D. = No MA was detected at this conditions.
S is the selectivity defined as the weight % of TA to DA in the extract.
52
The interaction plots for the continuous supercritical fluid fractionation set up:
DA
TA
53
TA (8.9 %)
DA (4.9 %)
AcOH (86 %)
54
Experimental matrix for a 2×4×2 general factorial design and experimental
data obtained for continuous scCO2 fractionation
Variabls
Extracted (%)
P
(bar)
T
(°C)
1
70
45
F
(mL.min1)
1
2
70
45
3
70
4
Run
Raffinate (%)
AcOH
TA
DA
AcOH
TA
DA
MA
73.37
2.08
1.80
85.17
10.07
6.50
0.00
1.5
87.37
4.31
8/76
82.32
10.33
5.94
0.00
70
1
98.99
1.97
2.59
81.84
10.43
5.97
0.00
70
70
1.5
103.19
0.00
0.00
78.13
12.99
7.74
0.00
5
100
45
1
114.79
1.03
0.00
84.58
13.54
7.01
0.00
6
100
45
1.5
101.28
1.65
0.00
70.45
17.83
10.54
0.00
7
100
70
1
127.87
0.79
0.00
83.27
12.76
7.45
0.00
8
100
70
1.5
97.72
3.60
0.00
53.20
22.15
17.33
2.27
9
100‌
45
1
110.31
1.47
0.00
88.17
8.76
13.88
2.14
10
120
45
1.5
101.94
3.71
0.00
61.15
20.04
15.36
2.70
11
120
70
1
106.85
1.06
0.00
72.47
22.46
13.55
0.00
12
120
70
5/1
100.06
4.84
0.00
50.31
21.73
19.51
2.04
13
140
45
1
94.17
5.80
1.06
69.02
13.25
12.14
0.00
14
140
45
1.5
94.10
9.20
1.61
67.80
10.57
14.73
0.00
15
140
70
1
102.94
5.95
0.00
72.91
14.87
14.13
0.00
16
140
70
1.5
94.12
7.64
1.52
64.17
11.88
17.7
2.14
55
The interaction plots for the continuous supercritical fluid fractionation set up:
Raffinate
Extract
56
Conclusion:
DA
MA
TA
?





Removal of MA from the mixture of TA, DA and MA using a
semi-continuous SFE.
Prediction of the best condition toward TA 100% extraction
selectively.
A mixture of 31.50 and 19 (w/w %)
62% of TA & 17%
of DA.
Continuous fractionation process
41.8% of TA & 3.0%
DA.
Continuous fractionation process for selective extraction of
AcOH from the esterification product.
57






Removal of produced water by using proper azeotrope.
Catalyst screening towards the synthesis of TA, DA, and MA
selectively.
Variation of packing and column size towards selective extraction of
TA.
Reduction of pressure and/or temperature for extracting excess
AcOH from the esterification products before entering into packed
column.
On-line Continuous synthesis and separation of glycerol acetate
Using SCF technology to convert glycerol to the other valuable
products.
58
59