Unleaded fuels

The Eurosuper as defined by the European Directive of 16 December 1985, offering a minimum RON of 95 and a minimum MON of 85. Found throughout the European countries, it still is fairly scarce in France with 10% of the total demand for unleaded fuels. 

As of 1 July 1991 all new vehicles registered in Europe should have been adapted for using Eurosuper. However, another quality of unleaded fuel had already appeared in 1988 and has since been well established in some countries, notably France. It is called Superplus, the highest octane level, RON 98, MON 88. Superplus is suitable for vehicles having catalytic converters as well as for a large part of the former automotive fleet requiring an RON of 97 and higher. 

Note that for certain older engines, small quantities lead deposits from combustion could have a positive effect as a solid lubricant and prevent exhaust valve recession. For these motors which still represented in 1993 from 20 to 30% of the French automotive fleet, the use of unleaded fuel is not possible. 

Around 2000, the regulations should become more severe. In this area, a European limit of benzene of 3% appears very probable certain countries such as Germany are even looking at 1%. In Italy, it was decided towards the end of 1991, to limit benzene to 2.5% for leaded and unleaded fuels in the seven largest cities characterized by having heavy atmospheric pollution concurrently, in these same cities, the overall aromatic contents of gasolines should not exceed 33%. 

In the United States, the Clean Air Act of 1970 imposed limitations on composition of new fuels, and as such methanol-containing fuels were required to obtain Environmental Protection Agency (EPA) waivers. Upon enactment of the Clean Air Act Amendments of 1977, EPA set for waiver unleaded fuels containing 2 wt % maximum oxygenates excluding methanol (0.3 vol % maximum). Questions regarding methanol s influence on emissions, water separation, and fuel system components were raised (80). 

In 1957, Ethyl Corp. announced anew antiknock compound, methylcyclopentadienyknanganese tricarbonyl [12108-13-3] (MMT). MMT is almost as effective as lead on a per gram of metal basis, but because manganese was more expensive than lead, MMT was not widely used until limits were placed on the lead content of gasoline. MMT was used in unleaded fuel between 1975 and 1978. After a large fleet test suggested that MMT could increase exhaust emissions because it interfered with catalysts and oxygen sensors, EPA banned its use in unleaded fuel in 1978. MMT is used in Canada in unleaded fuel. 

Would you expect to find the same chemical composition of the hydrocarbons from the exhaust of a gasoline-powered automobile as that of gasoline in the vehicle s tank Why What would be the effect on emissions from a gasoline-powered vehicle if it was designed to be operated on leaded fuel and an unleaded fuel was used ... 

What would be the effect on emissions from a gasoline-powered vehicle if it was designed to be operated on unleaded fuel and a leaded fuel was used ... 

Before 1970 there was very little unleaded gasoline on the market, but by 1974 all gas stations were offering it. In 1974, unleaded fuel had become a necessity for most new cars because of their catalytic converters placed in the exhaust system. These contain platinum or palladium compounds that act as a surface catalyst to bum the hydrocarbons more completely. But lead coats the platinum and palladium and deactivates the converters, so unleaded gas must be used. Up to 4 g/gal of lead could be used in the 1970s, but this was decreased to 0.1 g by 1986. Since 1995 no leaded gas could be used in the U.S. Fig. 7.6 shows the dramatic shift from leaded to unleaded gas between 1975 and 1992. 

This is about a factor of 2 lower than that calculated for 1980 due to the large number of automobiles which used unleaded fuel and the lower lead content in leaded fuel in 1980 (9 ). For the other extreme where primary emissions from all sources become well mixed, a situation which is possible because of the long... 

Not all service stations receiving premium unleaded fuel from the distribution terminal were affected. Only a limited number of stations received fuel containing water and corrosion products. This explained the random nature and limited scope of the vehicle problems. 

Prior to the introduction of unleaded fuels, gasoline combustion in motor vehicles was by far the greatest... 

Copper, lead, cadmium and zinc have been found predominantly in potentially mobile forms by sequential extraction of material collected during road cleaning (Colandini et al, 1995). Cadmium and zinc were found to be more labile than lead and copper. A study of street dust and gully pot sediments confirmed this order of potential availability (Striebel and Gruber, 1997) and also suggested that lead levels in material of the types studied had decreased since the introduction of unleaded fuel in Germany. Lead has also been studied in street dusts from Brisbane, Australia. The element was found mainly in the carbonate phase and in the smaller particle size fraction (Al-Chalabi and Hawker, 1996) except where resuspension caused particle aggregation. 

Low-polarity solvents Oxidative environments Dilute alkaline solutions Aqueous acids Highly aromatic solvents Water and salt solutions Unleaded fuels give some problems due to the presence of methyl alcohol. 

Four unleaded fuels were selected for the octane evaluation program. The fuels ranged from a regular grade of leaded gasoline without the tetraethyl lead to Indolene high octane, the unleaded fuel used for emissions certification. Indolene is the trade name for the test fuel manufactured by Standard Oil Co. to meet the specification called out in Ref. 7. Some of the base fuel properties are given in Table I. 

Clearly, the best catalyst for the reduction reactions may not be the best for the oxidation reactions, so two catalysts are combined. The noble metals, although expensive, are particularly useful. Typically, platinum and rhodium are deposited on a fine honeycomb mesh of alumina (AI2O3) to give a large surface area that increases the contact time of the exhaust gas with the catalysts. The platinum serves primarily as an oxidation catalyst and the rhodium as a reduction catalyst. Catalytic converters can be poisoned with certain metals that block their active sites and reduce their effectiveness. Because lead is one of the most serious such poisons, automobiles with catalytic converters must use unleaded fuel. 

A large and growing source of naphthalenes is the high-boiling byproduct from the reforming processes that are used for the manufacture of high-octane motor fuels, and especially the unleaded fuels. These... 

Stambaugh, R.L., Kopko, R.J. and Frankhn, T.M. (1972) Effect of unleaded fuel and exhaust gas recirculation on sludge and varnish formation. SAE Trans. 81 Paper 720944. 

Figure 1. After aging with unleaded fuel, the Pd-only catalyst can meet LEV standards for MDV2 applications.

The move to unleaded fuels continues worldwide. However, several countries have increased the aromatics content (by up to 50%) to replace alkyl lead. These highly aromatic gasolines can lead to damage of elastomers and increased levels of toxic aromatic emissions if is used without catalysts. 

Some countries are increasing the aromatic content (up to 50% in some super unleaded fuels) to replace the alkyl lead octane enhancing additive. 

Fig. 19. Performance of noble-metal-substituted perovskites in the treatment of exhaust from single-cylinder engines, (a) (LaonSr02) (Coo.9Ruoi) Oj supported on a Torvex alumina honeycomb after 1000-h exposure to exhaust from leaded fuel in the first bed of a dual-bed catalytic system, (b) (Lao6Sr04) (Coo.94Ptfl.ojRuo.03) Oj on a Torvex alumina support after 800-h exposure to exhaust from unleaded fuel in a three-way catalytic system. (Redrawn by permission from Ref. 206.)...

---