ASTM D7347-07

Standard Test Method for Determination of Olefin Content in Denatured Ethanol by Supercritical Fluid Chromatography

SCOPE
1.1 This test method covers the determination of the total amount of olefins in denatured ethanol to be used as an oxygenate additive in blended spark ignition engine fuels. The method of determination is supercritical fluid chromatography (SFC). The application range is from 0.1 to 1.0 mass percent total olefins. Results are expressed in terms of mass percent olefins.
1.2 This test method can be used for the analysis of denatured ethanol that is intended to be used as an oxygenate additive in commercial spark ignition engine fuels.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Jul-2007
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0C - Liquid Chromatography

Relations

• Replaced By: ASTM D7347-07e1 - Standard Test Method for Determination of Olefin Content in Denatured Ethanol by Supercritical Fluid Chromatography
• Effective Date: 01-Aug-2007
• Referred By: ASTM D4806-21a - Standard Specification for Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Aug-2007
• Referred By: ASTM D8011-19 - Standard Specification for Natural Gasoline as a Blendstock in Ethanol Fuel Blends or as a Denaturant for Fuel Ethanol
• Effective Date: 01-Aug-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation: D 7347 – 07
Standard Test Method for
Determination of Olefin Content in Denatured Ethanol by
Supercritical Fluid Chromatography
This standard is issued under the fixed designation D 7347; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers the determination of the total 3.1 Definitions:
amount of olefins in denatured ethanol to be used as an 3.1.1 critical pressure, n—that pressure needed to condense
oxygenate additive in blended spark ignition engine fuels. The a gas at the critical temperature.
method of determination is supercritical fluid chromatography 3.1.2 critical temperature, n—highest temperature at which
(SFC). The application range is from 0.1 to 1.0 mass percent a gaseous fluid can be converted to a liquid by means of
total olefins. Results are expressed in terms of mass percent compression.
olefins. 3.1.3 supercritical fluid, n—fluid maintained in a thermo-
1.2 This test method can be used for the analysis of dynamic state above its critical temperature and critical pres-
denatured ethanol that is intended to be used as an oxygenate sure.
additive in commercial spark ignition engine fuels. 3.1.4 supercritical fluid chromatography, n—class of chro-
1.3 The values stated in SI units are to be regarded as the matography that employs supercritical fluids as mobile phases.
standard. The values given in parentheses are for information
4. Summary of Test Method
only.
4.1 A small aliquot of the denatured alcohol sample is
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the injectedontoasetofthreeanalyticalchromatographiccolumns
connected in series. The sample is transported through the
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- columns using supercritical carbon dioxide (CO)asthe
mobile phase. The first column is packed with polyvinyl
bility of regulatory limitations prior to use.
alcohol(PVA).Thesecondcolumnintheseriesisananalytical
2. Referenced Documents
column packed with high surface area silica gel particles, and
2.1 ASTM Standards: the third column is packed with silica particles coated with
D 4052 Test Method for Density and Relative Density of strong cation exchange material loaded with silver ions.
Liquids by Digital Density Meter 4.2 Two six-port switching valves are used to direct the
D 5186 Test Method for Determination of the Aromatic different classes of components through the chromatographic
ContentandPolynuclearAromaticContentofDieselFuels system to the detector. In a forward flow mode, saturates,
and Aviation Turbine Fuels By Supercritical Fluid Chro- aromatics,andolefinspassontotheanalyticalsilicagelcolumn
matography whilethealcoholisretainedonthePVAcolumn.Thesaturates,
D 6550 Test Method for Determination of Olefin Content of aromatics, and olefins are maintained on the silica column,
Gasolines by Supercritical-Fluid Chromatography whilethealcoholisback-flushedtothedetector.Thisstepfrees
the flow path of alcohol species allowing for the separation of
the olefins from saturates and aromatics. The forward flow
mode is resumed after the alcohol is eliminated and saturates
This test method is under the jurisdiction of ASTM Committee D02 on
are carried to the detector, while the aromatics are retained on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
the silica column and the olefinic species are trapped on the
D02.04.0C on Liquid Chromatography.
Current edition approved Aug. 1, 2007. Published September 2007.
silver-loaded column. The next step is to back-flush the olefins
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
from the silver-loaded column to the detector. Finally the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
aromatics are carried from the silica column to the detector in
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. a forward flow mode, bypassing the silver-loaded column.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7347–07
TABLE 1 Typical Columns
4.3 A flame ionization detector (FID) is used for quantita-
tion. Calibration is based on the area of the chromatographic Column Type: PVA Silica Silver-loaded silica
Vendor: Selerity, Selerity, Merck Selerity,
signal for olefins, relative to standard reference materials,
Waters Hypersil,
which contain a known mass percent of total olefins as
Corporation Phenomenex
corrected for density. Packing material: PVA High surface Cation exchange
area silica
particles
5. Significance and Use
Particle size, µm: 5 5 5
Length, mm: 50 500, 250 50
5.1 Olefinic hydrocarbons that may be present in denatured
Internal diameter, 1, 4.6 1, 4.6 1, 4.6
ethanolhavebeendemonstratedtocontributetophotochemical
mm:
reactionsintheatmosphere,andthiscanresultintheformation
of smog in susceptible urban areas.
5.2 The CaliforniaAir Resources Board (CARB) has speci-
fied a maximum allowable limit of total olefins in spark
Section 8. Typically, a 50-cm long, 1-mm internal diameter, or
ignition engine fuel. Denatured ethanol will be added at the
a 25-cm, 4.6-mm internal diameter column is used. This
terminals as an oxygenate additive and can contain olefinic
column is packed with particles having an average diameter of
speciescontributingtothetotalolefinspresentinsparkignition
5-µm or less, 600-nm (60-Å) pores, and a surface area of
engine fuel. An analytical method is therefore necessary to
$350-m /g.
determine total olefins in denatured ethanol intended for spark
NOTE 2—Columns suitable for Test Method D 5186 and D 6550 are
ignition engine fuel use.The test method is intended to be used
also suitable for this test method. Sources and typical dimensions are
by both regulators and producers.
shown in Table 1.
5.3 The present test method is automated, does not require
6.1.4.2 A silver-loaded silica or cation exchange column
anysamplepreparation,andhasarelativelyshortanalysistime
capable of separating olefins from alkanes. Typically, a 5-cm
of approximately 20 min.
long by 1-mm internal diameter column packed with particles
having an average diameter of 5-µm is used for the analysis.
6. Apparatus
NOTE 3—Silver-loaded silica columns suitable for Test Method D 6550
6.1 Supercritical Fluid Chromatograph (SFC)—Any SFC
are also suitable for the present method. Sources and typical dimensions
instrumentation can be used that has the following character-
are shown in Table 1.
istics and meets the performance requirements specified in
6.1.4.3 A polyvinylalcohol (PVA) column capable of sepa-
Section 8.
rating alkanes, olefins, and aromatics from alcohol. Typically,
NOTE 1—SFCinstrumentssuitableforTestMethodD 6550aresuitable
a 5–cm long by 1–mm or 4.6–mm internal diameter column
for this test method if equipped with a second column heater as described
packed with PVA particles is used for the analysis.
in 6.1.5.1 and columns as described in 6.1.4.
NOTE 4—PVA columns that have been used successfully are shown in
6.1.1 Pump—The SFC pump shall be able to operate at the
Table 1.
required pressures (typically up to about 30 MPa) and deliver
a sufficiently stable flow to meet the requirements of retention 6.1.5 Column-Temperature Control—The chromatograph
time precision (better than 0.3%) and detection background shall be capable of controlling column temperature to within
(Section 8). The characteristics of the pump largely determine 0.5ºC or less.
the optimum column diameters. Columns with an inside 6.1.5.1 A secondary column heater mounted in the column
diameter of 1.0-mm ID require a pump flow capacity of chamber can be used to heat the silver-loaded column inde-
approximately 50-µL/min of liquid carbon dioxide, whereas
pendently of the silica and PVA columns. This supplemental
columns with an inside diameter of 4.6-mm require a pump heating is recommended for faster clearance of the olefins and
capacity of at least 1-mL/min of liquid carbon dioxide.
saturates from the silver-loaded column. The supplemental
6.1.2 Detectors—A flame-ionization detector (FID) is re- column heater box is typically maintained at 150ºC.
quired for quantitation. A flow restrictor shall be installed 6.1.6 Computer or Electronic Integrator—Means shall be
immediately before the FID. The restrictor serves to maintain providedforthedeterminationofaccumulatedpeakareas.This
the required pressure in the column, while allowing the pump can be done by means of a computer or electronic integrator.
and detector to perform as specified in 8.2. The computer or integrator shall have the capability of correct-
6.1.3 Sample Inlet System—Aliquid-sample injection valve ing for baseline shifts during the run.
is required that is capable of introducing a sub-microliter 6.1.7 Switching Valves—Two six-way switching valves are
volume with a precision better than 0.5%.A0.200 to 0.060-µL configured in accordance with the scheme shown in Figs. 1-4.
injectionvolumewasfoundtobeadequateincombinationwith Four different positions are shown in these figures and are
1-mm diameter columns. The sample inlet system shall be defined as follows:
installed and operated in a manner such that the chromato- 6.1.7.1 Position LC (Load Column)—PVAcolumn (forward
graphic separation is not negatively affected. flush mode), silver column (forward flush mode), and silica
6.1.4 Columns—Threecolumnsofequalinsidediameterare column (forward flush mode) connected in series. The flow
required: enters the PVAcolumn first, then the silica column second, and
6.1.4.1 A high surface area silica column, capable of sepa- the silver-loaded silica column third. This position is used to
rating alkanes and olefins from aromatics as specified in (1) inject the sample onto the columns and (2) retain the
D7347–07
FIG. 4 Valve Position EA—High Resolution of Aromatics, Step 5
FIG. 1 Valve Position LC—Load Columns, Step 1 and 3
6.1.7.3 Position BO (Back-Flush Olefins)—The silica col-
umnisnotintheflowpath.ThePVA(back-flushmode)andthe
silver-loaded silica (back-flush mode) columns are connected
in series. The olefinic species are eluted in this position (see
Fig. 3).
6.1.7.4 Position EA (Elute Aromatics)—PVA column (for-
ward flush mode), silver column (forward flush mode), and
silica column (forward flush mode) connected in series. The
flow enters the PVA column first, then the silver-loaded silica
column second, and the silica column third. This position
differs from position LC in that the silica column is the last
columnintheseries.Thearomaticsareelutedtothedetectorin
the forward flow mode (see Fig. 4).
FIG. 2 Valve Position BE—Back-flush PVA, Step 2
7. Reagents and Materials
7.1 Air—Zero-grade (hydrocarbon-free) air is used as the
FID oxidant. (Warning—Air is usually supplied as a com-
pressed gas under high pressure, and it supports combustion.)
7.2 Calibration Solution—An ethanolic mixture containing
olefins of a known mass % of the type found in typical
denatured alcohol. An example of this mixture would be
99.50% ethanol, 99.995% purity and 0.50% olefin solution
containing 2-pentene, 1-hexene and cyclohexene.
7.3 Carbon Dioxide (CO )—Supercritical fluid chromato-
graphic grade, 99.995% minimum purity, supplied pressurized
in a cylinder with a dip tube for removal of liquid through a
CGA320 fitting. (Warning—Liquid at high pressure. Release
of pressure results in production of extremely cold, solid CO
and gas, which can dilute available atmospheric oxygen.)
FIG. 3 Valve Position BO—Back-flush silver-loaded column,
7.4 Hydrogen—Hydrogen of high quality (hydrocarbon
Step 4
free) is used as the fuel for the FID. (Warning—Hydrogen is
usually supplied under high pressure and is extremely flam-
mable.)
alcohol on the PVAcolumn while allowing all other species to
7.5 Loading-Time Mixtures—Four loading time mixtures
pass onto the silica column. After the alcohol is flushed from
are recommended to determine the switching times for this test
the system in Position BE (back-flush ethanol) this position
method and to protect the silica column from exposure to
will again be used to (1) elute the saturates, (2) load the olefins
ethanol and the silver-loaded column from contamination by
onto the silver-loaded silica column, and (3) retain the aromat-
aromatics and ethanol.
ics on the silica column (see Fig. 1).
7.5.1 Loading-Time Mixture A—Amixture of 10 % alkanes
6.1.7.2 Position BE (Back-Flush Ethanol)—PVA column
(n-hexane and cyclohexane), 10 % aromatics (benzene, tolu-
(back-flush mode).This position directs the flow from the PVA
ene, and naphthalene), and 80 % ethanol can be used to
column to the detector. The silica and silver-loaded silica determine the loading time of saturates, olefins, and aromatics
columns are not in the flow path. The alcohol is eluted in this
onto the silica column while protecting the silica and silver-
position (see Fig. 2). loaded column from ethanol contamination.
D7347–07
TABLE 2 Typical SFC Conditions
usedsuccessfully.Iftheperformancecharacteristicsintermsof
Parameter Value retention and resolution specified in 8.2 are not achieved,
temperatures, pressure, or mobile-phase flow rate can be
Pump pressure, atm 200
Temperature, °C 40
modified to achieve compliance.
Injection volume, µL 0.06
FID temperature, °C 400, range 0
System Performance
Secondary column heater temperature, °C 150 to 200
Air, mL/min 300
8.2 System Optimization—The operation of the SFC system
Hydrogen, mL/min 50
Analysis time, min 15 to 25
shall be optimized in order to achieve the required separation
on the silica column. Individual pure components and a
performance mixture can be used to optimize the system.
7.5.2 Loading-Time Mixture B—Amixture of 10 % alkanes
8.3 Column Requirements:
(n-hexane and cyclohexane), 7 % aromatics (benzene, toluene,
8.3.1 Silica Column—The critical requirement for the silica
and naphthalene), 3 % olefins (2-pentene, 1 hexene, and
column is the ability to achieve a quantitative separation of the
cyclohexene) and 80 % ethanol can be used to determine the
olefins and saturates from the aromatics. The performance of
loading time of saturates and olefins onto the silver-loaded
this column is verified independently of the silver-loaded
column and protect it from aromatic contamination.
column by
...