Gasoline, lead free

Trichlorethylene Perchlorethylene Reference Fuel A Reference Fuel B Reference Fuel C Leaded gasoline Lead free gasoline Water... 

The picture we see now is that of new lead-free fuels having lower aromatics content but containing a variety of oxygenates. It is thus likely that the additives entering into the composition of gasoline will be also modified. 

Isomeri2ation of straight-chain hydrocarbons is of particular importance for lead-free gasoline. Addition of high octane aromatic hydrocarbons or olefins is questionable based on environmental considerations (77). An efficient octane enhancing additive is methyl tert-huty ether (MTBE). 

Catalysts can be poisoned, or inactivated. A common cause of such poisoning is the adsorption of a molecule so tightly to the catalyst that it seals the surface of the catalyst against further reaction. Some heavy metals, especially lead, are very potent poisons for heterogeneous catalysts, which is why lead-free gasoline must be used in engines fitted with catalytic converters. The elimination of... 

Because of these damaging effects, most uses of lead that involve direct exposure for humans are being phased out. Unleaded gasoline and lead-free paints have replaced two former major commercial uses of lead. Lead has proved to be Indispensable, however, in the lead storage battery, which now provides the major use of this metal. Although leakage from damaged batteries is still a potential hazard, contemporary batteries are manufactured in such a way that human exposure to battery contents is minimized. 

Catalysts were expensive, however, so the petroleum industry did not solve the problem of cheap, lead-free, knock-free gasoline until the 1970s, after General Motors adopted the catalytic converter. Lead compounds inactivate the catalysts, and sophisticated catalytic cracking techniques had to be developed to replace the fuel additive. Ironically, an even more difficult job was finding a substitute for the protective coating that tetraethyl lead formed on exhaust valve seats not even newly developed, extremely hard materials prevent wear and tear on them as well as tetraethyl lead did. 

CHAPTER 9 Lead-Free Gasoline and Clair C. Patterson... 

Lead-free gasoline an automotive fuel containing no more than 0.05 g of lead per gallon, designed for use in engines equipped with catalytic converters. 

Gasoline and diesel fuels are used worldwide in enormous amounts and are produced by the petroleum industry by oil refining (see Chapter 2). Liquid transportation fuels are conveniently transported, distributed, and dispensed directly into our vehicles and aircraft. Increased environmental concerns did much to begin to assure cleaner burning of our fuels. In the United States, law requires significant reduction of emissions and resulted in lead-free and more recently reformulated gasoline... 

Compositions of lead free gasoline with octane qualities equivalent to present day gasoline are shown in Table IV. These compositions represent the sum total of the many different refinery models presented in the API report. 

The olefin content of the gasoline pool has decreased from 19% on a leaded basis to only 9% on a lead free basis. Aromatics, however, have increased from 21 to 42%, respectively, and are as high as 51% in the premium gasoline. 

Table IV. Lead Free Gasoline—1965 Refining Basis...

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