7/26/2019 Acetylation of Starch in Supercritical CO2
1/37
| 1
H. Muljana, F. Picchioni, L.P.B.M. Janssen and H.J. Heeres
Chemical Engineering Department
University of Groningen
The Netherlands
Acetylation of Starch in Supercritical CO2
7/26/2019 Acetylation of Starch in Supercritical CO2
2/37
| 2
Outline
Introduction
Objectives Why supercritical CO2
Experimental results and discussion
Exploratory process studies
Fundamental studies
Solublity
Conclusions
Acknowledgement
7/26/2019 Acetylation of Starch in Supercritical CO2
3/37
Green chemical reaction engineering at RUG
Catalytic biomass conversions
Biofuels Platform chemicals
Bio based (performance) materials
Catalytic pyrolysis oil upgrading
Biodiesel fromJatropha Curcas
hydroxymethylfurfural levulinic acid methanol diols phenolics
Novel polymers from valerolactone
St a r ch a n d cel l u l o se m od i f i ca t i o n
7/26/2019 Acetylation of Starch in Supercritical CO2
4/37
| 4
General
Objective:
Study potential ofsupercritical CO2assolventfor starchmodification reactions
Literature data:
Remarkably little known on modification chemistry inscCO2
Landmark
patent:R.
Harris,
S.
H.
Jureller,
J.
L.
Kerschner,
P.
T.
Trzasko,
and
R.
W.
Humphreys,U.S.Patent,5977348(1999)
Introduction
7/26/2019 Acetylation of Starch in Supercritical CO2
5/37
| 5
Why use supercritical solvents
Liquid like density and gas like diffusivity
Supercritical conditions for sCO2 relatively mild: Pc = 73 bar, Tc = 31 oC Green properties: non toxic, relatively inert, non flammable
Easy of separation
High pressure equipment required Complex phase behaviour for mixtures
Properties Gas Supercritical
fluid
Liquid
(kg m-3) 1 100 800 1000
(Pa s) 0.001 0.005 0.01 0.05 0.1
D (m2 s-1) 1. 10-5 1.10-7 1.10-9
7/26/2019 Acetylation of Starch in Supercritical CO2
6/37
Introduction
(a) (b)
(c) (d)
7/26/2019 Acetylation of Starch in Supercritical CO2
7/37
Introduction
Approach:
Perform modification reactions in scCO2
System: model reaction, acetylation selected
Approach: screening and focussed studies
Fundamental studies on starch-scCO2 interactions
(solubility, gelatinization); Experimental and modeling
7/26/2019 Acetylation of Starch in Supercritical CO2
8/37
| 8
Introduction
Model reaction : Acetylation of starch
Native starch Starch acetate
Reactants : acetic anhydride
Catalyst : alkaline salt catalyst(NaOH, NaOAc, Na2CO3)
7/26/2019 Acetylation of Starch in Supercritical CO2
9/37
| 9
Introduction
Reaction network:
7/26/2019 Acetylation of Starch in Supercritical CO2
10/37
| 10
Introduction
Drawbacks current aqueous processes:
Solids content limited to 35- 42%-w Lowering of selectivity for starch acetate due to hydolysis (SAA)
High costs associated with water removal in work-up scetion
Lab scale
High DS and SAApossible, however application of pyridine,DMSO instead of water
Toxic, high environmental impact
Supercritical CO2 ??
7/26/2019 Acetylation of Starch in Supercritical CO2
11/37
| 11
Experimental Setup
Pmax 350 bar
7/26/2019 Acetylation of Starch in Supercritical CO2
12/37
Process studies; initial screening
Process variables
Pressure: 8-25 MPa
Fixed
Temperature (90C)
Catalyst (NaOAc)
Output
Degree of substitution (DS) Acetic anhydride conversion (Xaah)
Selectivity to desired starch acteylation reaction (Ssa)
7/26/2019 Acetylation of Starch in Supercritical CO2
13/37
| 13
4000 3500 3000 2500 2000 1500 1000 500 0
Transmitan
ce(%)
Wavelength (cm-1)
1612 cm-1
1723 cm
-1
1609 cm-1
a
b
Product analyses: FT-IR
7/26/2019 Acetylation of Starch in Supercritical CO2
14/37
Product analyses: NMR
01234567
(b)
ppm
(a)
Acetylgroup
7/26/2019 Acetylation of Starch in Supercritical CO2
15/37
Product analyses: SEM
Native potato starch Acetylated starch
7/26/2019 Acetylation of Starch in Supercritical CO2
16/37
| 16
0
0.05
0.1
0.15
0.2
0.25
0.3
80 100 150 200 250 285Pressure (bar)
DS
Selectivity
Optimization study- Effect of pressure
DS max : 150 bar
SAAn max : 150 bar
Literature [1]:rates maximal near the criticalpoint of mixture
T = 90 C
1. Savage, P. E., Gopalan, S., Mizan, T. I., Martino, C. J.& Brock, E. E. (1995),AIChe Journal, 41, 1723-1778.
7/26/2019 Acetylation of Starch in Supercritical CO2
17/37
| 17
0
0.05
0.1
0.15
0.2
0.25
0.3
80 100 150 200 250 285
Pressur e (bar)
DS
Selectivity
Optimization study- Effect of pressure
Critical point mixture
7/26/2019 Acetylation of Starch in Supercritical CO2
18/37
Overview supercritical properties
Table 2.The critical region of AAH-CO2 mixtures at different temperatures
No T
(oC)
Critical region
(MPa)
yAAH
1 50 9.4 9.8 0.08
2 70 12.4 12.6 0.09
3 90 14.5 14.8 0.09
7/26/2019 Acetylation of Starch in Supercritical CO2
19/37
Effect of starch particle size
Table 3. Comparison of the DS for various starch particle sizes at different reaction conditions
a.fractionated with specified sieve trays, b.determined by laser diffraction c.Experiments at 50 oC, 8 MPa , d.Experiments
at 90oC, 15 MPa
Particle
sizesa
Average Particle Size
(dv)b
Condition Ic Condition II
d
(m) (m) DS DS
36 - 45 43.64 0.21 0.51
45 - 56 52.33 0.18 0.48
56 - 63 62.55 0.18 0.46
> 63 73.5 0.15 0.29
Mainly surface reaction, intra particle mass transfer limited
7/26/2019 Acetylation of Starch in Supercritical CO2
20/37
Catalyst screening
P: 15
MPa T: 90C
C/Sratio 0.1mol/mol
t 1
h
Catalyst basicity plays
a role
NaOAc exception?
7/26/2019 Acetylation of Starch in Supercritical CO2
21/37
Systematic process studies
T: 50-90C
P: 8- 25 MPa C/S: 0.1-0.5 (mol/mol)
AAH/S: 4.35 time: 1 h
Catalyst: K 2CO3
22 experiments
Output analysed by non-linear regression
7/26/2019 Acetylation of Starch in Supercritical CO2
22/37
Results
Max DS: 0.5
7/26/2019 Acetylation of Starch in Supercritical CO2
23/37
Results
AAH intake as additional variable Catalyst intake as additional variable
Pressure shows an optimum
7/26/2019 Acetylation of Starch in Supercritical CO2
24/37
| 24
Solubility of sCO2 in starch
Definition solubility :S = (mCO2 dissolved)/mpolymer
Experimental method : Gravimetric : Magnetic Suspension
Balance (MSB)
Range : max T = 473 K, max P = 50MPa
MSB schematic drawing (Nalawade S, 2005)
7/26/2019 Acetylation of Starch in Supercritical CO2
25/37
| 25
Solubility Study: Results
Sstarch acetate
> Snative
DS SA: 0.5
Muljana et al. Accepted for publication in Polymer Engineering and Science
7/26/2019 Acetylation of Starch in Supercritical CO2
26/37
Solubility data; comparison
Polymer Pressure Temperature Solubility
(MPa) (oC) (mg CO2/g sample)
Polystyrene (PS) 0 - 9.5 40 30.9 134
2 - 19.8 100 12.7 - 121.8
Poly(ethylene terephthalate)(PET) 0- 39.5 80 0 38
0 - 39.5 120 0 - 32.5
5 - 30 120 9.1 - 37.2
Polypropylene (PP) 5 - 10 40 29.9 - 54.2
5 - 10 120 22.6 - 43.8
Poly(butylenes succinate)(PBS) 1 - 9.9 50 9.8 73
2.3 - 19.9 120 21.7 - 176.1Polycaprolactone (PCL) 8 - 20 50 29.3 - 1637.9
Poly(L-lactide)(PLLA) 10.73 - 29.9 50 190 - 699.5
Starch 2-16 120 8-31
Starch acetate 2-26 120 14-80
7/26/2019 Acetylation of Starch in Supercritical CO2
27/37
FT-IR measurements for SA at high pressure
S starch acetate> S native
Lewis acid baseinteraction
7/26/2019 Acetylation of Starch in Supercritical CO2
28/37
| 28
Concluding Remarks
sCO2 is a suitable solvent for starch acetylation reactions
DS is tunable with pressure
Highest DS values at critical points of mixture
Reactions are intra-particle mass transfer limited
In the range T = 120oC and P = 20 300 bar : Max S native : 31 mgCO2/g starch Max S starch acetate : 79 mgCO2/g starch
S starch acetate > S native
7/26/2019 Acetylation of Starch in Supercritical CO2
29/37
Acknowledgement
Sjoerd van der Knoop
Danielle Keyzer Prof. Z. Knej (University of Maribor)
AVEBE for stimulating discussions
7/26/2019 Acetylation of Starch in Supercritical CO2
30/37
| 30
7/26/2019 Acetylation of Starch in Supercritical CO2
31/37
080908 | 31
Good performance of scCO2
Acetylation Study Results
T , DS T, SAA
7/26/2019 Acetylation of Starch in Supercritical CO2
32/37
080908 | 32
Acetylation Study Effect of pressure and temperature
0 50 60 70 80 90 100
0,00
0,05
0,10
0,150,20
0,25
0,30
0,35
0,40
0,45
0,50
0,55
50 deg C
70 deg C
90 deg C
DS
Pressure (bar)
P , DSconstant
Working at higherpressure (P > 100 bar)
0 50 60 70 80 90 100
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0,160,18
0,20
0,22
0,24
50oC
70oC
90oC
SAAn
Pressure (bar)
7/26/2019 Acetylation of Starch in Supercritical CO2
33/37
Determination of supercritical properties
(a) (b) (c) (d)
(e) (f) (g) (h)
7/26/2019 Acetylation of Starch in Supercritical CO2
34/37
080908 | 34
Gelatinization study (1) DSC Results
T > , P >, DG >
P : 80 bar 250 bar
7/26/2019 Acetylation of Starch in Supercritical CO2
35/37
080908 | 35
Gelatinization study (2) XRD results
P , broader amorphous region
P (bar)
Degree of
crystallinity
Relative
crystallinityNative 0.132 1.00
80 0.125 0.94
150 0.108 0.82
250 0.102 0.77
P , Crystallinity , DG
7/26/2019 Acetylation of Starch in Supercritical CO2
36/37
080908 | 36
Optimization study- Effect of pressure
b. 150 bar, 24 h, DS = 0.61
a. 150 bar, 1 h, DS = 0.29 b. 200 bar, 1 h, DS = 0.23
d. 200 bar, 24 h, DS = 0.31
7/26/2019 Acetylation of Starch in Supercritical CO2
37/37
Rationalise
Liquid phase
AAH
Catalyst
DissolvedCO2
Possibly
some water
AA
Gas phase
Mainly
scCO2
Dissolved
AAH
StarchParticle
Water
AAH
Catalyst
AA
Dissolved
CO2
Gas-liquid-solid Supercritical -solid
Supercriticalphase
CO2
AAH
Catalyst
Possibly
some water
AA
StarchParticle
Water
AAH
Catalyst
AA
Dissolved
CO2
Top Related