ASTM: Gasoline Today and Tomorrow – An Executive Report

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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
Octane Week | ASTM: Gasoline Today and Tomorrow - An Executive Report ASTM Committee Reaches Agreement on Ethanol Sulfate Specification This story appeared on December 11, 2006. After nearly two years of debate, the ASTM D02 committee on petroleum fuels has approved three new test methods in support of a 4 ppm sulfate specification in D 4806, ASTMʼs denatured fuel ethanol specification. The final discussions at the Committeeʼs winter meeting in Orlando, Fla., were characterized as congenial and cooperative, as ethanol producers joined with refiners to make the new methods possible. ASTM will assign identifying numbers to the new methods probably sometime in December, and the specification containing the test methods should be published by ASTM in February, sources tell Octane Week. “The specification becomes effective when it is available to the general public,” our source told us. The three methods, two by ion chromatography (IC) and one by a lead potentiometric titration, underwent extensive round-robin testing by the D02.03 Subcommittee on Elemental Analysis. One set of tests conducted this spring failed because of sample stability problems. Sodium sulfate can precipitate out of ethanol and ethanol-blended gasoline, making accurate sulfate measurements impossible. But the first round robin did produce acceptable data for measuring up to 50 ppm total chloride in fuel ethanol using the IC methods, which is also included in the specification. Eager to proceed, the 4 ppm specification was approved by the D02.A Subcommittee on Gasoline and Oxygenated Fuels in June, pending approval of one or more of the methods in December. That was accomplished, so no time was lost by the shortcomings of the first round robin. Another ASTM inter-laboratory study (ILS) that corrected for the sulfate stability problems was conducted over the summer. That study included an oxidation step in the IC methods to convert sulfate that may have been reduced back to sulfate prior to testing. This gives a “potential” sulfate result along with the total sulfate result. The summer ILS produced positive results, but study organizers faced another challenge in compiling a precision statement for one of the IC methods. Direct injection IC devices utilize different column suppression configurations – tri-chamber and continuous. Statisticians could not get all of the data from the different devices to converge into a single precision statement for the method. Under intense time pressure this fall, they reworked the data in a way that yielded acceptable convergence for the two suppressor configurations, and two precision statements were added to the method. By late November, D02 Committee members had completed balloting of the three methods, all backed by solid ILS results. The ballots yielded only three negative votes that were successfully resolved at last weekʼs meeting. Two involved a procedural misunderstanding and were withdrawn. The other negative vote challenged the data pooling technique for the direct injection IC method, which had confounded statisticians this fall. “The negative voter had no problem with the test method, only the way the data for the precision statement were pooled,” our source explained. “There is a possible different way of grouping data in the precision statement, and that will be considered for a method revision this spring.” With all negatives successfully adjudicated, the full committee approved the three sulfate test methods for use in D 4806, bringing a controversial issue to a successful resolution. “Ethanol producers are pleased,” said one attendee. “They were extremely cooperative, participated in the round robins and provided good data. None of them voted against the ballots.” Now it is up to Subcommittee A to determine how the test methods will be listed. Members could make one test the “primary” method and the others “alternative” methods, or they could say that any of the methods is acceptable. All three methods are capable of measuring total sulfate in concentrations as low as 1 ppm. The debate over the level of the sulfate specification, 1 ppm versus 4 ppm, was one of the early and most divisive fights among Subcommittee A members. Refining and auto groups support a 1 ppm sulfate limit, ethanol producers have not to this time. Given ethanol producersʼ increased membership (continued on p16) February 2007 15
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