Transcript Sterol glucoside-112607 - Wayne State University

Sterol Glucosides in Biodiesel
Haiying Tang, Steven O. Salley, and
K. Y. Simon Ng
National Biofuels Energy Laboratory
NextEnergy/Wayne State University
Detroit, MI 48202
1
Outline
 Chemical structure and physical properties of sterol
glucosides
 Precipitates formation above cloud point in Soy-,
Cottonseed-, and Poultry Fat-based Biodiesel Blends
 “Filter-Blocking Tendency ” test and cold soak filtration
 Analysis method
 Typical processing technique for oil refining
 Possible techniques to remove sterol glucosides
 Conclusion
2
Plants Sterols
 Free sterols
 Sterol esters
 Sterol glucosides
 Acylated sterol
glucosides
3
Sterol composition in seed oil (mg/kg)
Composition Palm Soy
bean
Rapeseed Cottonseed Corn
oil
Safflower
Sunflower
β-sitosterol
1894 1908 3549
3961
7722
1809
2352
campesterol
358
720
170
2691
452
313
stigmasterol
204
720
42
702
313
313
Δ5avenasterol
51
108
122
85
468
35
156
Δ725
stigmastenol
108
306
-
117
696
588
other
26
36
612
-
173
195
Net % in oil
0.26
%
0.36
%
0.61%
0.43%
0.35%
0.39%
1530
1.18%
Data From Gunston ed al, The lipid handbook, 1994
4
Chemical Structure of Sterols
 Phytosterols mainly include campesterol, β-sitosterol,
stigmasterol, Δ5-avenasterol, Δ7-stigmastenol, and
brassicasterol.
5
What is Sterol Glucoside in Biodiesel?




Sterol Glycosides occurs naturally in vegetable oils, mainly as
soluble fatty acid esters ;
Usually, the acyl sterol glycosides at concentrations are two to ten
fold greater than those of the non-acylated forms;
Hydrolyzed during transesterification process and become insoluble.
β-sitosterol glucoside is the most typical sterol glucoside.
β-sitosterol glucosides
6
Biodiesel Reaction- Base Transesterification
100 lbs of oil +10 lbs methanol
100 lbs of biodiesel +10 lbs of glycerol
7
8
Physical Properties of Free Sterol
Glucosides
 Powdery solid, melting point 283-287°C
 Limited solubility in most organic solvents
except pyridine, chloroform/methanol
(2:1)
 Soluble in fresh biodiesel.
9
Typical Concentration of SG in Biodiesel (ppm)
Feedstock
SG 1
SG 2
β-sitosterol
Total sterol
Soy #1 Crude Grade
272
78
1908
3600
Soy #2 Degummed Grade
54
Soy #3 Refined Grade
190
Soy #4 (processed poorly)
25
Cottonseed oil #1
22
10
3961
4258
Cottonseed oil #2
8
Corn oil
480
45
7722
11700
Palm oil
141
118
1894
2558
Safflower Crude Grade
14
1809
3478
2352
3917
Sunflower
18
Canola
18
Data from 1 Ringwald SC. Biodiesel characterization in the QC environment;
2 Pfalzgraf et al , Identification of sterol glucosides in biodiesel and their effect on filterability.
10
Precipitates Formation above Cloud
Point in Soy-, Cottonseed-, and
Poultry Fat-based Biodiesel Blends
11
Cold Flow Properties: a current issue
with biodiesel
• Precipitates formation in
biodiesel blends may have
serious implications.
– Clogging of fuel filters.
– Formation of deposits on
engine parts such as injectors
and other critical fuel system
components.
12
ASTM Test Methods
• Cold–flow properties: traditional petroleum wax
precipitation
– Cloud point (CP, ASTM 2500): at which crystallization begins.
– Pour point (PP, ASTM 97): at which the fuel no longer will pour.
– Cold filter plugging point (CFPP, ASTM 6371): at which fuel
starts to plug a fuel filter.
• Total insoluble: high temperature in the presence of
oxygen
– ASTM D 2274 (Accelerated Method): Oxidation Stability of
Distillate Fuel (95 ºC for 16 h).
– ASTM D 4625: Storage Stability of Middle Distillate, Petroleum
(43 ºC for selected periods up to 24 weeks).
13
Experimental
• Samples:
 SBO-, CSO-, and PF- based biodiesel
 ULSD, B2, B5, B10, B20, B50, B70, and B100
 300 mL volume
• Storage Temperature and Time
-15 ºC for 24 hr
4 ºC for 24 hr
23 ºC for 24 hr (Control)
Allow to come to room temperature
without external heating
• Filter
 Vacuum pump: ~68 kpa
 0.7 mm glass fiber filter




Filtration system from ASTM D4625-04
14
Physical Appearance
(at 23 ºC for 24 hours )
SBO-based Biodiesel
ULSD
B20
B2
B50
B5
B70
B10
B100
15
Physical Appearance (at 4 ºC for 24 hours)
SBO-based Biodiesel
ULSD
ULSD
B20
B2
B50
ULSD
B5
B70
B10
B100
16
Physical Appearance (at -15ºC for 24 hours)
ULSD
B2
B5
B20
B50
B70
B10
B100
17
Optical Images of Precipitates
50X
200X
Taken from B20 SBO-based biodiesel
18
Time to Filter Vs. Temperature
45
40
SBO-based biodiesel
23 º C
4 ºC
Minus 15 º C
Time to filter (min)
35
30
25
20
15
10
5
0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Biodiesel Concentration
19
Insolubles Mass Vs. Temperature
• No significant mass of
“new” insolubles as result
of blending at 23 ºC ;
• Significant effect at 4 ºC;
• Above the cloud point
insolubles are very
different in nature as
compared to the normal
wax-crystal like
insolubles formed below
cloud point.
20
Insolubles Mass Vs. Time
Precipitates (ppm)
50
B100
40
30
20
10
0
0
0.5 hr
1 hr
2 hr
4 hr
8 hr
20 hr
24 hr
72 hr
1 week
2 weeks
12 hr
24 hr
72 hr
1 week
2 weeks
Storage Time
35
B20
Precipitates (ppm)
30
25
20
15
10
• Different
mechanisms for
the insolubles
formation from
B20 and B100;
• For B20, the
relatively fast
appearance of
insolubles can be
attributed to a
solvency effect.
5
0
Control
1 hr
2 hr
4 hr
6 hr
8 hr
Storage Time
21
Insolubles Mass Vs. Feedstock
• CSO- and PF- based
biodiesel had lower
insolubles levels than
the SBO-based
biodiesel;
• The difference may be
attributed to the
presence of naturally
occurring levels of
sterol glucosides in the
feedstocks.
22
Cloud Point, Pour Point, and Cold Filter Plugging Point
Biodiesel-Soybean
Biodiesel-Cottonseed
5
-5
o
5
0
Temperature (o C)
0
Temperature ( C)
10
Cloud point
Pour point
Cold fiiter plugging point
Poly. (Pour point)
Poly. (Cloud point)
-10
-15
-20
-25
-30
-5
-10
-15
z
-20
-25
-30
-35
-35
-40
0%
20%
40%
60%
80%
100%
Biodiesel Concentration
10
5
0
-5
-40
0%
20%
40%
60%
80%
• The CFPP may indicate
relative extent of the
insolubles formation at low
temperature.
Cloud point
Pour point
Cold fiiter plugging point
Poly. (Cloud point)
Poly. (Pour point)
-10
-15
-20
-25
-30
-35
-40
0%
20%
40%
60%
Biodiesel Concentration
100%
Biodiesel Concentration
Biodiesel-Poultry fat
Temperature (o C)
Cloud point
Pour point
Cold fiiter plugging point
Poly. (Cloud point)
Poly. (Pour point)
80%
100%
23
Nature of Insolubles
 Possibilities

Sterol glucosides: Soluble within vegetable oil;
however, hydrolyzed during transesterification process
and become insoluble.

Monoglycerides, diglycerides, triglycerides of total
glycerin;

Dimers, trimers, tetramers of oxidative products;

Solvency effect when blended with ULSD.
24
Distilled and Oxidized Biodiesel
Distillated SBO-B20
Oxidative Biodiesel Blends
• After cold soak test, no insoluble
was observed in distilled or
oxidized B100, or even in B20;
• Insolubles formation is due to
minor component;
• Insolubles formation is not due to
oxidized product.
• The nature of “the above cloud
point insolubles” formation is
different from the oxidized
insolubles observed in the high
temperature stability test of
biodiesel;
25
Nature of Insolubles: FTIR Spectra
-OH
-CH2
-CH2
C-O-C
Insolubles from SBO-B100
Insolubles from SBO-B20
Insolubles fromCSO-B100
Insolubles from CSO-B50
Standard Sterol Glucosides
26
Nature of Insolubles: GC-FID Chromatograms
Insolubles from CSO-B100
Insolubles from SBO-B100
Internal Standard
Standard Sterol Glucosides
Three kinds of
Sterol Glucosides
27
GC-FID Chromatogram (Continued)
Precipitates from PF-B100
Standard Glycerides
28
Summary 1
• Storage temperature, storage time, biodiesel blend
level, and feedstock affect the mass of insolubles
formed;
• Solvency of ULSD has a significant influence on
insolubles formation;
• Insolubles from SBO- and CSO-based biodiesel
are due to sterol glucosides. However, the
insolubles from PF-based biodiesel can be
attributed to glycerides.
29
“Filter-Blocking Tendency ”Test
• Tests
– 300ml of fuel at 20ml/min
– Filter
• ASTM D2068/IP387
• 1.6 micron
– Result calculated based on pressure and
volume measured during the test.
30
Effect of SG on FBT
SG content (ppm)
Filter-blocking tendency (FBT)
22 (Control)
32
52
72
1.05 (pass)
1.47 (fail)
2.90 (fail)
15.03(fail)
 Adding SG to biodiesel caused it to fail to the FBT test;
 SG presence at high enough levels could potentially cause
filter problems.
Data from Lee et al. The role of sterol glucoside on filter plugging,
Biodiesel Magazine 2007.
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Biodiesel Cold Soak Filtration
• Storage temperature and time
– 4 ºC (refrigerator)
– 16 hours
• Allow sample to come to the room temperature
(23 ºC to 24 ºC )
• Filter
– Vacuum pump: 22.5 inches Hg (~76.2 Kpa)
– Whatman 47 mm GF/F, 0.7 mm.
32
33
Biodiesel Cold Soak Filtration
B100 Filtration
1000
900
800
Filtration Time, sec.
700
Lab A
Lab B
Lab C
Lab D
Lab E
Lab F
Lab G
Lab H
600
500
400
300
200
100
0
1
2
3
4
5
6
7
B100 Sample
34
Different Feedstocks of Biodiesel
Biodiesel
1
2
3
4
5
6
7
Feedstock Canola Soy Animal Impr Dist Palm Soy
Fat
Soy Soy
35
Analysis of Sterol Glucosides
 The presence of sterol glucosides in
biodiesel residues has been confirmed
using FTIR and GC-FID
 Qualification will be evaluated by GCFID, HPLC, and FTIR with purchased
known standards
36
Preliminary results :GC-FID Chromatograms
sitosterol glucoside
campesterol glucoside
stigmasterol glucoside
Precipitates from REG
Precipitates from Nextdiesel
Standard sterol glucosides
37
Process of Crude Soybean Oil to
Food-grade Oil
 Refining
 Water degumming
 Caustic refining
 Bleaching
 Deodorization
 Chemical refining
–
–
–
–
Water degumming
Chemical neutralization
Bleaching
Deodorization
 Physical refining
– Acid degumming
– Bleaching
– Deodorization
38
Conventional RBD Process
Phospholi
pids and
gums
Remove
portion of
SG
Free fatty
acids
Reduce
portion of
free sterols
Pigments
(Distillation)
REFINED OIL
Steam
vacuum
DEODORIZATION
Bleaching
clays
BLEACHING
NaOH
CHEMICAL
NEUTRALIZATION
WATER
DEGUMMING
CRUDE OIL
Phosphoric
acid
Trace
component
Reduce
portion of
free sterols
39
Average Composition for Crude and
Refined Soybean oil
Data from Van Gerpen, J.; Biodiesel production technology, 2004
40
Process techniques to remove SG
 Filtering: removal of particulate from media with a
steel screen, cartridge or filter paper


Effect of filter pore sizes
Effect of filter types
 Cold filtering: holding the biodiesel at a lower
temperature for desired time before the filtering
process.


Effects of cold filter temperature
Effect of storage time
Particle
41
Preliminary Results: Effect of temperature on
removing particles with filtration
ppm
ULSD
23 ºC
0.9
4 ºC
0.9
-15 ºC
1.43
B2
B5
B10
B20
1.23
1.43
1.43
1.57
1.67
3.9
6.67
7.77
2.57
4.23
6.67
4.57
B50
B70
B100
2.23
3.33
5.77
14
19.23
9.1
22.33
20.77
32.23
 Cold filtration is better to remove
particles than room temperature
42
Preliminary Results: Effect of storage time on
removing particles with cold filtration (4 ºC )
ppm
0
B100
5.67
B20
1.67
1 hr
2 hr
4 hr
8 hr
3.33
3.33
5
3
4.83
5.83
7.33
20 hr
24 hr
3 days
13.67
11.67
30
7.17
8.5
9.33
40
43
14.33
25.17
1 weeks
2 weeks
 Longer storage time
in cold soak test
could more effective
to remove particles
in biodiesel.
43
Process techniques to remove SG (Con.)

Adsorbent treatment:


Removal of particulate with a
porous pad or a “cake” of
filter-aid-type materials
 Diatomaceous earth (DE)
 Magnesol
 Carbon
 Magnesium silicate
Act as deep filtration
 Effect of concentration
 Effect of incubation time
 Effect of temperature
Adsorbent
Untreated
Biodiesel
Mix
Tank
Finished
product
tank
Filter
44
SG content of biodiesel after incubation
and filtering through DE
Incubation
temperature (ºC)
0
Incubation
time
SG content
(ppm)
(FBT)
0
54
15.03 (fail)
4
6 hr
22
1.2 (pass)
4
12 hr
25
-
10
6 hr
27
-
21
1 day
19
-
21
2 days
16.29
-
21
3 days
17.29
-
Data from Lee et al. Processes of producing biodiesel and
biodiesel produced therefrom; Patent application publication,
2007.
45
Process techniques to remove SG (Con.)
 Water degumming: a basic process to wash
biodiesel product to remove contaminants
 Effect of water ratio
 Effect of mixing temperature
 Vacuum distillation: an energy intensive
technique for biodiesel processing
 Effect of temperature
 Effect of pressure
46
Preliminary Result: GC-FID Chromatography
Sterol glucosides
SBO-biodiesel
Glycerol
Precipitates from SBO-biodiesel
Distillated SBO-biodiesel
47
Conclusions
48
Future Work
• Evaluate and develop processing strategies
to reduce sterol glucosides content in
biodiesel;
• Develop a robust analytical method to
determine the sterol glucosides content in
biodiesel.
49
Thanks!
Questions?
50