ASTM: Gasoline Today and Tomorrow – An Executive Report

Octane Week | ASTM: Gasoline Today and Tomorrow - An Executive Report
ASTM Issues Ethanol Sulfate Test Method Ballots
This story appeared on October 23, 2006.
ASTM members are considering three ballots,
each proposing a different test method in support of the
4 ppm sulfate limit recently added to D-4806, ASTMʼs
denatured fuel ethanol specification. If one or more
of the test methods is acceptable, fuel providers will
have solved a difficult issue that threatened to divide
the subcommittee's ethanol, refiner and auto company
representatives.
The methods - two ion chromatography (IC)
procedures and a lead potentiometric titration method -
have been round-robin tested twice, and the latest results
are solid, sources close to the effort told Octane Week.
The goal is to have ASTM D0.2 Committee and
subcommittee members review the latest data, and
if negative votes are cast, “adjudicate” them using
ASTMʼs mediation process prior to the ASTM winter
meeting, which begins Dec. 4.
ASTMʼs D02 Committee on Petroleum Fuels
issued numerous ballots Friday afternoon. A quick
scan prior to Octane Weekʼs press time indicated two of
the three methods – potentiometric titration and direct
injection IC – were included among the ballots. The
standard is to be published next month. The balloting
will close Nov. 20.
Subcommittee members are feeling pressure
to complete the standard-setting process. Sulfate
contamination can cause filter plugging in the fuel
distribution system and in vehicle fuel injectors. That was
the case in 2003, when widespread vehicle fuel injector
plugging was reported. The events triggered the start of
the ethanol sulfate debate within D02.A a year later.
Despite the need to limit fuel sulfate content, it
took more than another year of delicate negotiations to
bring D02.A subcommittee members into agreement on
the appropriate level. After much debate, subcommittee
members voted last June to approve the 4 ppm sulfur
limit, overcoming limited support for a 1 ppm standard.
At the time of the vote, test method data was
lacking. It was expected that an ASTM Inter Laboratory
Study (ILS) conducted prior to the meeting would have
provided results demonstrating the adequacy of one or
more of the test methods. Instead, the ILS failed because
of sample-related problems. Sodium sulfate precipitated
out of the samples, and test results were not useful.
A second round robin was conducted this summer.
This latest round robin included a sample composition
that solved the earlier problem and an oxidation step
in the IC methods to convert any sulfate that may have
been reduced over time back to sulfate.
This time around, both the aqueous injection and
direct injection IC methods produced “good data” from
a dozen or so participants, a source familiar with the
round robin told Octane Week.
The lead titration method, which did not include an
oxidation step, also produced “very good results from
about 10 participants.”
Some 21 labs participated in the direct injection IC
tests, the source said. “The statistician tried to pool the
data and could not get convergence. Instead, there was
a bimodal result.”
The two leading IC devices, manufactured by
Metrohm and Dionex, use different column suppression
configurations (tri-chamber and continuous), and that
may account for the majority of difference in results.
“The instruments are different and give different
responses. Both are in use, so there is an effort to get
an idea of how the results will appear so that both
instruments will be allowed in the test method with
their own precision statements,” our source told us.
The precision correlation was reworked and now
there is “different but good convergence for each of the
two suppressor configurationsʼ data.”
Ballots for the aqueous injection IC method and
the potentiometric titration method were submitted to
ASTM in September. ASTM also extended the ballot
deadline so ILS leaders could submit the revised
direct injection IC method for ballot. That method will
have two precision statements for the two types of IC
suppression configurations that were tested.
“From the results of our round robin, I am fully
confident any of the three methods will support the 4
ppm sulfate specification. They all will also support a 1
ppm specification,” he said.
That doesnʼt mean the test method ballots will pass
easily, ASTM sources warn. If the negatives cannot be
adjudicated successfully, the ballot could fail in December.
In that event, the methods would need to be reworked to
address the negatives and reballoted in the spring.
14 February 2007