Gasoline additive, , toxicity

Some elements come in and out of fashion, so to speak. Sixty years ago, elemental silicon was a chemical curiosity. Today, ultrapure silicon has become the basis for the multibillion-dollar semiconductor industry. Lead, on the other hand, is an element moving in the other direction. A generation ago it was widely used to make paint pigments, plumbing connections, and gasoline additives. Today, because of the toxicity of lead compounds, all of these applications have been banned in the United States. 

Due to methanol s corrosivity and its affinity for water, it cannot be readily distributed in today s fuel infrastructure. Methanol burns with a nearly invisible flame. Available luminosity additives won t reform in the low-temperature methanol steam reformers. Methanol is more acutely toxic than gasoline. Additives that are likely to be needed for safety and health reasons will impact the fuel processor s performance and cost. 

Synonym tetraethylplumbane, lead tetraethyl Formula Pb(C2H5)4 MW 323.47 CAS [78-00-2] used in motor gasoline as an additive to prevent knocking such an application, however, is currently curtailed because of environmental pollution boils at 200°C vapor pressure 0.2 torr at 20°C density 1.653 g/mL at 20°C insoluble in water slightly soluble in alcohols dissolves in benzene, toluene, hexane, petroleum ether, and gasoline highly toxic (Patnaik, 1992). 

Triphenylphosphate is a colorless, odorless, crystalline solid (mp, 49°C bp, 245°C). It is moderately toxic. A similar, but much more toxic, compound is tri-o-cresyl-phosphate (TOCP), an aryl phosphate ester with a notorious record of poisonings.3 Before its toxicity was fully recognized, TOCP was a common contaminant of commercial tricresylphosphate. Tricresylphos-phate is an industrial chemical with numerous applications and consists of a mixture of phosphate esters in which the hydrocarbon moieties are meta and para cresyl substituents. It has been used as a lubricant, gasoline additive, flame retardant, solvent for nitrocellulose, plasticizer, and even a cooling fluid for machine guns. Although modem commercial tricresylphosphate contains less than 1% TOCP, contaminant levels of up to 20% in earlier products have resulted in severe poisoning incidents. 

Ge Tetraethyl lead has been widely used as a gasoline additive to improve combustion but is being phased out because of the toxic hazard associated with all lead compounds. 

Nature produces a tremendous amount of methyl alcohol, simply by the fermentation of wood, grass, and other materials made to some degree of cellulose. In fact, methyl alcohol is known as wood alcohol, along with names such as wood spirits and methanol (its proper name the proper names of all alcohols end in -ol). Methyl alcohol is a colorless liquid with a characteristic alcohol odor. It has a flash point of 54°F, and is highly toxic. It has too many commercial uses to list here, but among them are as a denaturant for ethyl alcohol (the addition of the toxic chemical methyl alcohol to ethyl alcohol in order to form denatured alcohol), antifreezes, gasoline additives, and solvents. No further substitution of hydroxyl radicals is performed on methyl alcohol. 

Ethanol is also a common laboratory solvent, which is sometimes made unfit to ingest by adding small amounts of benzene or methanol (both of which are toxic). Ethanol is used as a gasoline additive because it readily combusts with the release of energy. Other simple alcohols are listed in Figure 9.4. 

Development of tetraethyllead as gasoline additive. Its toxicity causes special handling measures to be developed. 

Methanol is toxic to humans, causing blindness in low doses (15 mL) and death in larger amounts (100-250 mL). Industrially, it is used both as a solvent and as a starting material for production of formaldehyde (CHgO), acetic acid (CH3COOH), and the gasoline additive methyl ier -butyl ether IMTBE, CHj,OC(CH3)al. 

For some time, methylcymantrene ( / -CH3C5H4)Mn(CO)3 (MMT) has been used as a substitute for the highly toxic tetraethyllead (C2H5)4Pb as a gasoline additive. For one period, 40 % of the car gasoline sold in the United States contained MMT. It has been claimed by General Motors, however, that MMT is disadvantageous... 

Particular attention has also been given to the reconstruction of recent Pb emissions into the atmosphere, as detected in Greenland and Antarctic snow and ice. Owing to its well known toxicity and wide dispersion in the environment, caused in turn by the massive use as a component in a variety of products such as batteries, pigments, rolled and extruded items, cables sheaths and above all gasoline additives in the form of highly volatile alkyl-Pb compounds, Pb is classified as one of the... 

---