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PROPOSAL:

Rescind Rule 432-Gasoline Specifications

SYNOPSIS:

Rule 432 sets a limit for specific hydrocarbon content in gasoline in terms of the degree of unsaturation or olefin content in gasoline sold or supplied in the District. The limit is Bromine Number 30, which is equivalent to about 15 percent olefins. Beginning in 1996, California refineries have been producing California Reformulated Gasoline (CaRFG) as required by state law. The CaRFG specifications limit the amount of olefins in gasoline to a maximum of 10 percent by volume. Since the CaRFG specification limits olefin content in gasoline more effectively than Rule 432, staff recommends rescinding Rule 432.

COMMITTEE:

Stationary Source, May 22, 1998, Reviewed

RECOMMENDED ACTION:

Adopt the resolution to rescind Rule 432 - Gasoline Specifications.

Barry R. Wallerstein, D.Env.
Acting Executive Officer

Background

Rule 432, Gasoline Specifications, sets a limit of Bromine Number 30 for the level of unsaturation or the olefin content in gasoline sold or supplied in the District (see Attachment A). The rule was adopted by the Governing Board on May 7, 1976, and has never been amended. Prior to its adoption and the formation of the South Coast Air Quality Management District, the same limit was already imposed by Rule 63 of the Los Angeles County Air Pollution Control District, which was effective June 30, 1960. Section 2250 of the California Code of Regulations also requires a Bromine Number limit of 30 for gasoline sold or supplied in the South Coast Air Basin.

California Health and Safety Code Section 39667, Revisions to Vehicular Emission Standards, requires the state to adopt emission standards for vehicular sources and regulations specifying the content of motor vehicle fuel to achieve a maximum possible reduction in public exposure to toxic contaminants. As a result, the ARB adopted the CaRFG regulations, which includes among other things, the olefin content not to exceed 10 percent by volume. The CaRFG specifications became effective on April 1, 1996, except for small refiners where compliance is effective March 1, 1998. Because of CaRFG Regulations, Section 2250 was amended January 26, 1996 and no longer applies to gasoline sold or supplied on or after April 1, 1996 or March 1, 1998 for small refiners.

Rule 432 (see Attachment A) specifies use of a standard test method of the American Society for Testing and Materials, ASTM Method D 1159. The method uses an electrometric titration, the end point of which is indicated by a sudden change in potential due to the presence of free bromine. The CaRFG regulations use ASTM Method D 1319 as a reference test method. Method D 1319 involves a fluorescent indicator adsorption for liquid petroleum products. This method is more reliable and reproducible than ASTM Method D 1159 specified in Rule 432.

Because of the implementation of the more effective limitation on olefin content in gasoline in CaRFG regulations and the availability of a more accurate reference test method, Rule 432 is considered to be unnecessary and no longer has any impact on air quality in the AQMD.

Following is a brief description of olefins and Bromine Number and test methods used for the measurement of olefin content:

Olefins

Olefins or alkenes are a type of unsaturated hydrocarbon having one or more double bonds, which can be produced by the process of cracking heavier hydrocarbons at high temperatures. Olefins, because of the presence of the double bonds, are more reactive than the saturated counterpart. The ARB had considered limits of olefins in gasoline fuels because olefins have high ozone reactivity potential and contribute to reactivity due to the evaporative emissions. Olefins also contribute to higher NOx formation as a result of combustion of gasoline. The increase in NOx formation can be accounted for by the olefins' combustion temperatures being higher than the saturated hydrocarbons. Reducing the olefin content of gasoline also reduces 1,3-butadiene emissions in vehicle exhaust. 1,3-Butadiene has been identified by ARB as a toxic air contaminant.

Several studies showed that reduction of olefins in gasoline from 20 to 5 percent resulted in NOx reductions for both older and new vehicles, but VOC emissions increased in both old and new vehicles. Olefins with carbon numbers 3 through 5 are the highest reactive olefins of the olefinic species but represent a small component of the gasoline's olefinic content.

Bromine Number

Bromine Number is the amount of bromine in grams absorbed by 100 grams of sample. This Bromine Number indicates the degree of unsaturation. The Bromine Number is useful as a measure of aliphatic unsaturation in petroleum samples. The ARB, in its Motor Vehicle Fuels Compliance Assistance Program, indicated that every unit of Bromine Number is equivalent to twice the percentage point of olefin content in gasoline. So, a gasoline with Bromine Number 30 would have an olefin content of not more than 15 percent by volume. One refinery compiled a year's worth of data on Bromine Number and the corresponding olefin content of gasoline. The data showed that the Bromine Number of gasoline is about 2.4 times the olefin content. A gasoline with Bromine Number of 30 would then have an olefin content of about 12.5 percent by volume, which is slightly lower than ARB's assumption, but still is higher than the CaRFG maximum limit of 10 percent by volume.

Reference Test Methods

Rule 432 test method involves a reaction between bromine and the double bond in the olefin. This method involves an electrometric titration where the end point is indicated by a sudden change in potential on an electrometric end point apparatus due to the presence of free (excess) bromine.

As indicated earlier, Bromine Number is the number of grams of bromine reacting with 100 grams of the sample under prescribed conditions. By this definition, bromine consumed by addition, substitution, oxidation, and reactions with sulfur, nitrogen, and oxygen-containing compounds present in the sample is included in the Bromine Number of the material. Bromine reacts with olefins by addition reaction. The use of Bromine Number for determination in estimating olefinic unsaturation depends on the fact that the addition reaction proceeds rapidly and completely under most conditions. The addition of bromine proceeds readily at temperatures down to or below 0^oC. Decreasing the reaction temperature, contact time, and concentration of free bromine tend to retard both substitution and oxidation reactions. Other factors, such as solvent medium, extent of agitation, etc., also influence the rate of various reactions. Experience has shown that no single set of test conditions will direct the reaction of bromine in one manner to the exclusion of the others. For this reason, the conditions of Bromine Number tests are usually established on an empirical basis to give reasonable values with representative materials.

The possibility of multiple reactions occurring concurrently and the variable behavior to certain materials of bromine imposes an element of uncertainty in the interpretation of results. Also, the method uses 1,1,1-trichloroethane as a solvent, an ozone-depleting compound. There is also a concern about the 1,1,1-trichloroethane evaporating into the atmosphere.

Compliance with California RFG standard for olefins is determined using ASTM Method D 1319. This method is used to determine hydrocarbon types over the concentration ranges from 5 to 99 volume percent aromatics, 0.3 to 55 volume percent olefins (the 10 or 15 % olefin standards are within the range), and 1 to 95 volume percent saturates in petroleum fractions that distill below 315^oC. Analysis by ASTM Method D 1319 is done through fluorescent indicator adsorption, a more reliable and reproducible method than the titration method.

Proposal

Rule 432 sets a limit for unsaturation levels in gasoline at Bromine Number 30. This level is equivalent to olefin content of between 12.5 and 15 percent by volume. Presently, CaRFG's limit for olefin is a maximum of 10 percent, which is more effective in controlling olefins than that of Rule 432. Also at present, refineries are required to comply with both Rule 432 and CaRFG requirements using two different test methods and at an added cost to the refineries. In addition, control of evaporative emissions during storage and handling of gasoline, are already regulated by Rule 461 - Gasoline Transfer and Dispensing; Rule 462 - Organic Liquid Loading; and Rule 463 - Storage of Organic Liquids.

Based on the above, staff has concluded that Rule 432 no longer has any impact on air quality and is no longer necessary to control evaporative emissions. Therefore, Rule 432 should be rescinded.

CEQA

The AQMD has reviewed the proposed project pursuant to State CEQA Guidelines §15002 and AQMD CEQA Implementation Guidelines §1.2, which involves a three step process for determining the appropriate CEQA document. The first step involves a determination of whether CEQA applies at all. If the project is exempt, the process does not need to proceed any further, and a Notice of Exemption may be prepared (State CEQA Guidelines § 15002 (k)(1)).

As a result of the enactment of the CaRFG regulations, Rule 432 has no further air quality impacts on controlling gasoline evaporative emissions. The CaRFG regulations impose a more effective olefin limit on gasoline manufactured for sale or use in the District than that required by Rule 432. Additionally, the test method used to determine compliance in the CaRFG regulations is more accurate and reproducible than the compliance test method in Rule 432. Therefore, Rule 432 is no longer necessary since it no longer provides an air quality benefit to the District.

Based on the discussion above, the proposed rule rescission is exempt from the requirements of CEQA because it can be seen with certainty that the proposed actions have no significant adverse effect on air quality or any other environmental category [State CEQA Guidelines §15061 (b)(3) and AQMD CEQA Implementation Guidelines §5.1 (b)(3)]. A Notice of Exemption has been prepared in accordance with State CEQA Guidelines §15062 and AQMD CEQA Implementation Guidelines §5.2, - Notice of Exemption and a copy has been included in the Public Hearing agenda item (see Attachment B). The Notice of Exemption will be filed with the county clerks of the District counties immediately following the rescission of Rule 432 at the Public Hearing.

Comment from ARB

ARB indicated that because ARB's "cleaner burning gasoline" regulations contain limits on the olefin content of gasoline that are more effective, Rule 432 is no longer needed. ARB, therefore, is in concurrence with the AQMD's proposal to rescind the rule (see Attachment C).

Attachments

A. Resolution

B. Rule 432 – Gasoline Specifications, adopted May 7, 1976

C. Notice of Exemption and letter to County Clerk, Counties of San Bernardino, Orange, Riverside and Los Angeles

D. Letter dated April 20, 1998, from Dean C. Simeroth, Chief Criteria Pollutants Branch, ARB, to Mohsen Nazemi, Sr. Engineering Manager, AQMD.

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