Global gasoline, diesel quality continues to improve

Global fuel quality trends include reduced use of lead, increased gasoline research octane number (RON), reduced diesel sulfur levels, and increased diesel cetane number.

These are the findings of a recently released 1995 fuel quality survey conducted by Associated Octel Co. Ltd., Milton Keynes, U.K.

Octel's survey quotes officially published statistics, if available. When possible, the survey uses the actual quality of fuels found in the marketplace rather than legislated specifications.

Gasoline demand

Growth in gasoline demand was evident only in the Far East during 1995. Crude distillation capacity was checked in the U.S. and Europe during 1995, and investments in downstream processing units remain low.

"The only significant construction is in hydrotreating units, so that refiners can meet ever stricter sulfur limits imposed on automotive fuels," according to Octel.

Again, the Far East runs against the trend with planned increases in distillation and secondary processing capacities.

Gasoline quality

Thailand and Malaysia eliminated leaded gasoline production during 1995, following a trend started in the U.S. and Japan. Singapore, Taiwan, and Korea, have begun their phase-out programs.

While reduced lead levels are considered beneficial to human health, unleaded gasolines typically contain higher concentrations of aromatics to boost octane.

In the U.K. for example, unleaded gasoline contains an average of about 31.5 vol % aromatics, compared to 26 vol % for leaded gasoline. Similarly, in France unleaded and leaded grades contain, respectively, about 41.5 and 33.5 vol % aromatics.

Because aromatics are linked to increased emissions, especially in cars without catalytic converters, some U.K. marketers have stopped selling 98 RON unleaded gasoline. And the British government has reduced tax subsidies on this grade. Because of these two factors, the grade will disappear from the U.K. market, predicts Octel.

Increases in isomerization and alkylation capacity in the U.S. and Europe have given refiners in these regions the flexibility to increase octane without adding more aromatics to the pool. So, despite the fact that unleaded gasolines tend to contain higher levels of aromatics than leaded grades, aromatics levels in the U.S. and Europe are, in general, declining.

Outside these regions, refiners rely on the catalytic reforming process to increase octane. Octel says this results in gasoline aromatics concentrations as high as 40-50 vol % in parts of the Far East and Latin America.

Gasoline octane also varies widely by region. Gasolines in the U.S., Japan, and Australia, for example, typically are rated at 91-92 RON, while European gasolines are rated at 95-97 RON (Fig. 1).

Gasoline octanes of 97-98 RON are common in the Far East, says Octel, and there is a trend toward increased use of premium grades there (Fig. 2). Fig. 2 omits China and other Southern Asian countries that lag behind in tightening fuel specifications.

"China's average octane is the lowest in the region," says Octel, "although the Chinese are aiming to improve their gasoline octane, primarily by eliminating the 70 motor octane number (MON) product over the next few years. This will be achieved by increasing catalytic cracking and reforming capacities, and by adding lead."

Octel predicts average octane in the Far East will increase from 90 RON in 1994 to 92 RON by 2000, placing even greater pressure on the region's refineries.

Increased octane requirements have led to greater use of oxygenates, such as methyl tertiary butyl ether (MTBE), in many regions, although the U.S. and Finland use MTBE for its emissions benefits.

Diesel quality

Diesel demand is increasing in a number of markets because of what Octel calls "perceived emissions and fuel economy benefits attributed to diesel-engined vehicles." Legislation reducing diesel sulfur levels is coming into effect in many countries, while others are introducing low-sulfur product ahead of legislation.

Use of low-sulfur diesel (defined by Octel as 0.05 wt % or less) has been mandatory in the U.S. since October 1993. Germany, Nordic countries, and some U.K. marketers have introduced the product ahead of the 0.05 wt % limit to be imposed by the European Union in October 1996 (Fig. 3).

Sulfur reductions also have been proposed in Japan, Taiwan, Korea, and Thailand. Other countries in the Asia/Pacific region are expected to follow suit by 2000.

Cetane quality is another important focus for diesel producers. According to Octel, although cetane index historically has been the preferred measure of diesel quality, cetane number has gained in popularity.

In Europe, cetane numbers greater than 50 are now common. In fact, Octel's survey reveals a cetane number of almost 54 for U.K. diesel.

Research has shown that high diesel cetane can reduce both emissions and engine noise. Diesel cetane can be increased via crude oil selection, processing scheme, or additive use.

In the Far East, diesel cetane numbers depend on crude choice, says Octel. As a result, in many cases, product quality exceeds specifications. Some marketers in the region, however, are increasing cetane further through the use of cetane-improving additives.

Additive use

Fuel additives have gained widespread acceptance from refiners and marketers. According to Octel, "Performance-enhancing additive packages containing detergents are now used extensively by marketers in Europe, the U.S., and the Far East, as well as by some marketers in South America, to differentiate their products."

An historical analysis of Octel's surveys shows that, in 1993, 40% of the European leaded gasoline samples collected contained performance additives. By 1995, the percentage had increased to about 75%. By contrast, about 65% of European unleaded gasolines sampled in 1993 contained additives, compared to 100% in 1995.

Since Jan. 1, 1995, all gasoline sold in the U.S. must contain low dosages of additives. Higher concentrations are likely to be required when the U.S. Environmental Protection Agency finalizes its detergent requirements, says Octel.

The U.S. does not require use of additives in diesel fuel. "However, several major fuel marketers perceive such additives as an opportunity to differentiate their product and gain market share by promoting 'premium' diesel," says Octel.

Europe does not mandate the use of additives in either gasoline or diesel. In spite of this, detergent additives are used widely there.

Use of performance additives has increased recently in Latin American and Asian countries. Thailand, Korea, and Argentina, for example, use additives.

These areas currently favor use of U.S. performance requirements, rather than Europe's more demanding ones.