Analysis and Chromatographic
Separation of Oxygenates in Hydrocarbon
Matrices
Ken Lynam
GC Application Chemist
March 3rd, 2008
Ken Lynam
Pittcon 2008, New Orleans, LA
Presentation Outline
¾ WCOT vs. PLOT columns
¾ OxyPLOT – A highly selective phase for oxygenates
¾ Proposed ASTM methods
¾ Trace oxygenates in reformulated gasoline
¾ Oxygenates in C1-C5 hydrocarbon matrices
¾ Applications beyond oxygenates
¾Summary
¾ Take away message
¾ acknowledgements
Ken Lynam
Pittcon 2008, New Orleans , LA
WCOT vs. PLOT
Type
WCOT
PLOT
Stationary
Phase
Liquid or
gum
Solid
Chromatographic
Process
Gas / Liquid
partition
Gas solid
adsorption
Stationary
Phases
Polysiloxanes
PEG
Porous Polymers,
Al2O3,
Zeolites, etc.
Ken Lynam
Pittcon 2008, New Orleans , LA
WCOT Ethylene Analysis
Ken Lynam
Pittcon 2008, New Orleans , LA
PLOT Ethylene Analysis
Ken Lynam
Pittcon 2008, New Orleans , LA
Capillary Column Types
Porous Layer
Layer Open
Open Tube
Tubular
Porous
(PLOT)
Solid Particles
Carrier Gas
Wall Coated Open Tube (WCOT)
Carrier Gas
Liquid Phase
Ken Lynam
Pittcon 2008, New Orleans , LA
PLOT Columns
"Solid"
Porous
Layer
Fused Silica
Tubing
Ideal for the analysis of gases due to
their increased retention (k) and unique
selectivity (α) compared to WCOT
Ken Lynam
Pittcon 2008, New Orleans , LA
Surface Interactions in PLOT Columns
+
+ +
δ- δ+
+ +
δ-
+ +
+ + + +
neutral
δ+
+ +
+
+
Gas Flow
+
+ + + +
+ + +
+ + +
Vapor pressure always plays a leading role in solute interactions
Ken Lynam
Pittcon 2008, New Orleans , LA
Considerations for PLOT
Column Analysis
• Inlet issues
• split versus direct injection
• gas sampling valves
• low dead volume
• Detector issues
• particle generation or “spiking”; particle traps
• column ID and flow rate
Ken Lynam
Pittcon 2008, New Orleans , LA
Considerations for PLOT
Column Analysis
• Column issues
• selectivity
• capacity; overloaded peaks
• inertness
• temperature limits
•Elution order of major peak
• Column contamination
• efficiency loss; “ghost peaks”; increase in bleed
• water, CO2, high molecular weight hydrocarbons?
•Carrier gas purifiers
Ken Lynam
Pittcon 2008, New Orleans , LA
Oxygenates Applications
Petrochemical and Chemical companies have a need to
quantitatively measure low level oxygenates in petroleum
products
Gas
Oil Fields
Shipping Ctrs
Crude Oil
Refineries
Light HCs
Gas
Jet Fuel
Diesel
Fuel Oil
Distribution
Centers
Fuel
Oil
Diesel
Ken Lynam
Pittcon 2008, New Orleans , LA
Need for Low Level Analyses
Petrochemical and Chemical companies have a need to
quantitatively measure low level oxygenates in petroleum
products
Gas
Oil Fields
Shipping Ctrs
Crude Oil
Refineries
Light HCs
Gas
Jet Fuel
Diesel
Fuel Oil
Distribution
Centers
Fuel
Oil
Diesel
The need to measure trace oxygenates from 10
to 1000 ppm in Gasoline
•Problems with MTBE in reformulated gasoline
•MTBE causing groundwater contamination
•Desire to use ethanol as a renewable, green fuel additive
Ken Lynam
Pittcon 2008, New Orleans , LA
Oxygenates in Gasoline and Naphtha
Why are these measurements needed
• Oxygenated additives in reformulated gasoline
– Needed for clean air regulations and petroleum fuel extenders
• Problems with groundwater contamination
– Ethers in gasoline (MTBE, ETBE, TAME) in underground tanks
– Greater toxicity than alcohol additives
– Move toward biofuels
– Fuels derived from renewable agricultural products
– Ethanol from fermentation of biomass
– Lower toxicity than other alcohols
• Improve quality of feedstocks
– Gasoline and naphtha used as feedstock for other HPI products
– Traces of oxygenates poison catalyst
• lower production yields
• lower product quality
Ken Lynam
Pittcon 2008, New Orleans , LA
Traditional Oxygenates Methods
ASTM D4815
• Valve based using TCEP packed/ DB-1 capillary column
• Used to measure oxygenated additives (0.1 wt% to 15 wt%)
• ASTM study shows that D4815 has interference problems
– TCEP column cannot separate trace oxygenates from trace olefins
ASTM D5599
• Single column method using oxygen selective detector (OFID)
• Expensive system that is dedicated to only one application
• Selectivity and sensitivity may not be good enough for low ppm
Ken Lynam
Pittcon 2008, New Orleans , LA
New Method Under Development by ASTM D2
Method Scope
• Trace oxygenates in finished gasoline from 10 ppm to 1000 ppm (wt/wt)
• Oxygenates include:
– methanol, n-propanol, i-propanol, n-butanol, s-butanol, t-butanol, s-butanol,
t-pentanol
– MTBE, ETBE, DIPE, TAME
– Ethanol additive from 1 to 15 wt%
– Internal standard: 1,2-dimethoxyethane (DME)
Other capabilities
• can measure other oxygenate contaminants
– ketones and other alcohols and ethers
• can be used for naphthas
• sensitivity range can be lowered to 1 ppm with no changes in method conditions
Ken Lynam
Pittcon 2008, New Orleans , LA
New Proposed ASTM Method Instrumentation
Configuration
• Uses valve switching 2-D GC
• DB-1 column separates oxygenates/light hydrocarbons
from heavy hydrocarbons
• Agilent GS-OxyPLOT column separates light
hydrocarbons from oxygenates
Ken Lynam
Pittcon 2008, New Orleans , LA
Proposed ASTM Methods Uses 2-D GC with
Oxygenate Selective PLOT column
Vent
4
3
5
1. Sample introduction
of gasoline onto DB-1 pre-column.
Flow
Source
6
S/SL
2
1
DB-1
30m x 0.53mmid x 5um
GS- OxyPLOT
10m x 0.53mmid
FID
Aux
EPC
Vent
2. Oxygenates and light hydrocarbons
transfer to GS-OxyPlot. Heavy
hydrocarbons remain on DB-1 precolumn.
4
3
5
Flow
Source
6
S/SL
2
1
DB-1
30m x 0.53mmid x 5um
GS- OxyPLOT
10m x 0.53mmid
FID
Aux
EPC
Vent
4
3. Heavy hydrocarbons vented from
DB-1 pre-column. Oxygenates
resolved on GS-OxyPlot column.
3
5
Flow
Source
6
S/SL
DB-1
30m x 0.53mmid x 5um
2
1
GS-OxyPLOT
10m x 0.53mmid
FID
Aux
EPC
Ken Lynam
Pittcon 2008, New Orleans , LA
What Is GS-OxyPLOT?
• A 10 m x 0.53 mm I.D., 10 µm film thickness, Porous Layer Open
Tubular (PLOT) Capillary Column. Agilent p/n 115-4912.
• The stationary phase is a “proprietary salt based adsorbent ”.
• Key characteristics are:
– Strong selectivity to oxygenated hydrocarbons.
– Methanol (BP 65 °C) elutes after Tetradecane (BP 254°C)
Solute
RI*
MTBE
1236
IsoButylaldehyde
1368
Methanol
Acetone
1418
1450
*150°C
– Upper temperature limit 350°C with no column bleed
– Stabilized phase coating, minimizing particle generation and
detector spiking
Ken Lynam
Pittcon 2008, New Orleans , LA
GS-Oxy-PLOT “Electronic” Selective Interactions
Distinct Advantages
•
Adsorption interactions are much stronger than the polar/nonpolar interactions in “liquid” stationary phases.
•
Oxygenated hydrocarbons, un-retained in a WCOT column even
at sub-ambient temperatures can exhibit high retention in a PLOT
column at GC oven temperatures above ambient
•
Non-polar solutes are essentially un-retained except for their
vapor pressure interaction at a given oven temperature.
•
Ideal column for selective solute-value cut applications
•
Column phase is surprisingly inert to the polar compounds it so
strongly interacts with.
•
Good for low concentration, quantitative GC analysis
Ken Lynam
Pittcon 2008, New Orleans , LA
GS-OxyPLOT Column Separation of Trace Oxygenates and
Ethanol Additive in Reformulated Gasoline
Light Hydrocarbons
Ethanol
C3 to C5 Alcohols
Ethers
Methanol
12.5
14.5
15.5
min
22
23
24
25
min.
1,2-DME(IS)
25
t-Pentanol
i,n-Propanol
MeOH
13.5
20
n-Butanol
15
t,s,i-Butanol
10
TAME
DIPE
ETBE
MTBE
5
26
27
min
Ken Lynam
Pittcon 2008, New Orleans , LA
Ethanol Influenced Retention Time Shifts
12 wt% ethanol
1 wt% ethanol
12
14
16
MTBE
12.660
ETBE
12.498
18
12
12.5
22
24
min.
TAME
13.755
DIPE
12.789
MeOH
15.463
12.753
12.601
20
13.852
12.886
13
15.687
13.5
14
14.5
15
15.5
min
Ken Lynam
Pittcon 2008, New Orleans , LA
Excellent Quantitative Precision
High Concentration QA/QC Check Sample
ETBE
MTBE
DIPE
TAME
Methanol
Ethanol*
i,n-Propanol
t,s,i-Butanol
n-Butanol
t-Pentanol
Expected Avg Std Dev
(ppm)* (ppm)* (ppm)*
780
758
1.3
795
816
1.5
795
758
1.1
779
779
1.4
802
759
1.6
12.0%
11.3%
0.0
1619
1566
14.7
2399
2372
4.4
798
791
1.7
801
766
0.6
Low Concentration QA/QC Check Sample
RSD
0.2%
0.2%
0.2%
0.2%
0.2%
0.4%
0.9%
0.2%
0.2%
0.1%
ETBE
MTBE
DIPE
TAME
Methanol
Ethanol*
i,n-Propanol
t,s,i-Butanol
n-Butanol
t-Pentanol
Expected Avg Std Dev
(ppm)* (ppm)* (ppm)*
49
48
0.7
49
46
1.0
49
93
0.7
48
48
0.3
50
67
0.6
1.0%
0.9%
0.0
101
95
1.3
150
152
2.4
50
47
0.8
50
47
0.2
RSD
1.4%
2.1%
0.8%
0.6%
0.8%
2.2%
1.4%
1.6%
1.6%
0.5%
*ethanol results are in wt%
Each QA/QC sample prepared in reformulated gasoline
Five consecutive runs of each sample
Ken Lynam
Pittcon 2008, New Orleans , LA
New Method Under Development by ASTM D2 for
Analysis of Oxygenates in Ethene, Propene, C4
and C5 Hydrocarbon Matrices
Method Scope
•Oxygenates in these light hydrocarbon matrices from 500 ppb to 100 ppm (wt/wt)
•Oxygenates include 25 alcohols, ketones, aldehydes and ethers (e.g.):
–methanol, ethanol, n-propanol, n-butanol, s-butanol, t-butanol, s-butanol
–DME, MTBE, DIPE, TAME
–Acetone, acetaldehyde
Liquid
Sample
Gas
Sample
1 mL
Similar in principle to
the oxygenates in
gasoline method
Fused Silica
Restrictor
2 µL
DB-1
25 m X 0.53mm I.D.,
1.0 µm
GS-OxyPLOT
10 m X 0.53mm I.D.,
10 µm
Ken Lynam
Pittcon 2008, New Orleans , LA
Hydrocarbons and Oxygenates Separation using DB-1
Stripper Column and GS-OxyPLOT Separation Column
Column 1: DB1, 25 m x 0.53 mm x 1 um
P/N 125-102J
Benzene
Isooctane
1.
Dimethyl ether
2.
Diethyl ether
Column 2: GS-Oxy-PLOT, 10 m x 0.53 mm 3.
P/N 115-4912
4.
Carrier gas: Helium, 40 cm/s @ 50°C
Injection volume: 1 uL
5.
8
Inlet: Split, 250
6.
• Temperature: 225 oC
7.
• Split Ratio: 10:1
8.
• Column flow: 11 mL/min
5 6
2
4
n-Octane
Acetaldehyde
Ethyl t-butyl ether
Methyl t-butyl ether
Diisopropyl ether
Propionaldehyde
14.
Isovaleraldehyde
15.
Valeraldehyde
16.
MEK
17.
Ethanol
18.
1-Propanol
19.
Isopropyl Alcohol
20.
Allyl Alcohol
21.
Isobutyl Alcohol
9.
Propyl ether
22.
t-Butyl Alcohol
10.
Isobutylaldehyde
23.
s-Butyl Alcohol
11.
Butylaldehyde
24.
n-Butyl Alcohol
25.
2-Methyl-2-pentanol
Methanol
21,22,23
9
12
Oven
7
10
14
17
19
18 20
11 13 15
1
Acetone
Tert-amyl methyl ether
12.
3
Backflush occurs here
13.
16
24
•
Initial temp 50 oC
•
Initial hold 5 min
•
Ramp rate: 10 oC/min
•
Final temp 240 oC
25
Ken Lynam
Pittcon 2008, New Orleans , LA
GS-OxyPLOT and ASTM
A New Proposed ASTM Method for Trace Oxygenates in Reformulated
Gasoline
• designed to measure 10 to 1000 ppm oxygenates in gasoline with 1 to 15
wt% ethanol additive
Agilent 7890A GC System with GS-OxyPlot Column meets method
requirements
• excellent separation of oxygenates from light hydrocarbons
• resolves all ethers (ETBE, MTBE, DIPE, and TAME)
• high quantitative precision for both high and low concentrations in the
presence of percent ethanol
A New Proposed ASTM Method for Trace Oxygenates in Light Hydrocarbon
Matrices
• designed to measure 500 ppb to 100 ppm oxygenates in matrices with
BPts less than 200°C
Ken Lynam
Pittcon 2008, New Orleans , LA
Is GS-OxyPLOT also Selective for Sulfur Species?
•
Oxygen and Sulfur same group on periodic chart
•
Similar chemistries
•
Some sulfur species added deliberately to gaseous fuels
•
Both are found in hydrocarbon fuels and feed stocks
•
Sulfur species and oxygenates levels need to be controlled
Ken Lynam
Pittcon 2008, New Orleans , LA
GS-OxyPLOT C5-16 Carbon
Ladder/Spectrum Mix Comparison
FID1 B, (021508A\021508A 2008-02-15 13-10-25\002B0302.D)
Norm.
180
160
140
120
100
80
60
40
20
2
4
6
8
10
12
14
min
8
10
12
14
min
FID1 B, (021908B\021908B 2008-02-18 17-07-44\013B0402.D)
Norm.
24
22
20
18
16
14
12
10
8
6
2
4
6
Ken Lynam
Pittcon 2008, New Orleans , LA
Spectrum Mix GS-OxyPLOT
GC:
Oven:
Injection:
Carrier:
Column:
Detection:
Agilent 6890
60% (0.5 min),10% C/min to 120, then 25% C/min to 310% (3min)
1 µl 25:1 split 250%C, gas saver on at 2 min
He 30 cm/sec at 60%C constant flow mode
GS-OxyPLOT 10 m x 0.53mm x 10 µm
FID 350%C H2 40 ml/min, air 450 ml/min N2 makeup 30 ml/min
FID1 B, (021908B\021908B 2008-02-18 17-07-44\013B0402.D)
Norm.
24
22
20
18
16
14
12
10
8
6
2
4
6
8
10
12
14
min
Ken Lynam
Pittcon 2008, New Orleans , LA
DB-1 C5-16 Carbon Ladder/Spectrum Mix Comparison
FID1 A, Front Signal (021508A\021508A 2008-02-15 13-37-17\002F0302.D)
pA
180
160
140
120
100
80
60
40
20
0
2
4
6
8
10
12
min
8
10
12
min
FID1 A, Front Signal (021908A\021908A 2008-02-18 15-04-54\011F0202.D)
pA
24
22
20
18
16
14
12
10
8
6
2
4
6
Ken Lynam
Pittcon 2008, New Orleans , LA
DB-1 Spectrum Mix
GC:
Oven:
Injection:
Carrier:
Column:
Detection:
Agilent 7890
60% (0.5 min),10% C/min to 120, then 25% C/min to 310% (3min)
1 µl 25:1 split 250%C, gas saver on at 2 min
He 30 cm/sec at 60%C constant flow mode
DB-1 30 m x 0.25mm x 1.0 µm
FID 350%C H2 40 ml/min, air 450 ml/min N2 makeup 30 ml/min
FID1 A, Front Signal (021908A\021908A 2008-02-18 15-04-54\011F0202.D)
pA
27.5
25
22.5
20
17.5
15
12.5
10
7.5
5
2
4
6
8
10
12
min
Ken Lynam
Pittcon 2008, New Orleans , LA
Observed Retention Times on DB-1 and GSOxyPLOT for C5-C16 alkanes and sulfur species
Coumpound
Compound
n-pentane
n-hexane
n-heptane
trimethyl pentane
n-octane
n-nonane
n-decane
n-undecane
n-dodecane
n-tridecane
n-tetradecane
n-pentadecane
n-hexadecane
toluene
Ret. Time
DB-1
Ret. Time
OxyPLOT
BP
2.412
3.038
4.045
3.963
5.397
6.910
8.150
9.120
9.912
10.580
11.169
11.703
12.197
4.836
1.3
1.5
2.1
2.2
3.0
4.4
5.9
7.3
8.2
8.9
9.5
10.8
10.6
6.2
36
69
98
99
125
151
174
196
216
234
253
270
287
111
Alkanes less retained
1-propanethiol
ethyl methyl sulfide
2 methyl thiophene
3 methyl thiophene
ethyl disulfide
methyl disulfide
thianaphthene
thiophene
2,3,4 trimethyl benzo thiophene
2,3,6 trimethyl benzo thiophene
2,5,7 trimethyl benzo thiophene
Ret. Time
DB-1
3.040
3.080
4.872
4.972
7.074
4.464
9.870
3.621
12.273
12 .019
11.797
Ret. Time
OxyPLOT
5.4
6.8
6.1
6.3
8.9
7.6
10.3
4.9
12.4
12.2
12.4
BP
67-68
67
113
114
151-153
108
221-222
84
145-146
143-144
145-146
Sulfur species more retained
Ken Lynam
Pittcon 2008, New Orleans , LA
Interesting Observations
•
Sulfur species are retained on GS-OxyPLOT
•
high selectivity for some sulfur species
•
more relative retention for lower boiling sulfur species vs.
methyl silicone column
•
shift in retention may be useful for shifting sulfur species away from
hydrocarbon interferences
•
preliminary results are encouraging
Ken Lynam
Pittcon 2008, New Orleans , LA
Spectrum Mix Composition
Speturm Mix Composition
Level
methanaethiol
ethanethiol
dimethyl suldide
1-propanethiol
1-butanethiol
2-propanethiol
thiophene
diethyl suflide
t-butanethiol
diethyl disuflide
thiophenol
bromothiophene
phenyl sulfide
benzothiophene
98.4 ppm
99.3 ppm
99.6 ppm
88.9 ppm
100 ppm
101 ppm
99.9 ppm
100 ppm
100 ppm
100 ppm
100 ppm
101 ppm
100 ppm
99.7 ppm
Base Fuel Components
isootane 40%
hexane 40%
toluene 20 %
40%
40%
20%
Next steps
Follow up on initial study
Look at gaseous sulfurs
Evaluate using FPD
Evaluate dual column approach
similar to oxygenates
Ken Lynam
Pittcon 2008, New Orleans , LA
Summary
•
Attributes of a PLOT Column
•
GS-OxyPLOT’s characteristics
•
Proposed ASTM methods for oxygenates
• Reformulated gasoline
• C1-C5 hydrocarbon matrices
•
GS-OxyPLOT highly selective for
• oxygenates
• and indications are for sulfur species
Ken Lynam
Pittcon 2008, New Orleans , LA
Colleague Acknowledgements
Abby Folk
Simon Jones
John J. Harland
James D. McCurry
Mark Sinnot
Bruce Quimby
Allen K. Vickers
Ken Lynam
Pittcon 2008, New Orleans , LA
Thank you!
TECHNICAL SUPPORT
Agilent 1-800-227-9770 #4, #1
E-mail: [email protected]
Ken Lynam
Pittcon 2008, New Orleans , LA