Antioxidants in Gasolin

Urea derivatives are an important class of carbonyl compounds and useful chemical intermediates in the synthesis of pharmaceuticals, agricultural chemicals, and dyes and they are also used as antioxidants in gasoline and additives in plastics [51-54]. 

Use Antioxidant in gasoline and oils, including jet-engine oils. 

Antioxidants in gasoline, derived from aniline, have been determined using the anodic oxidation waves at a wax-impregnated graphite electrode directly in an alcoholic solution of the sample. 

Toluenesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene—sulfonic acid. By proper control of conditions, /)i7n7-toluenesulfonic acid is obtained. The primary use is for conversion, by fusion with NaOH, to i ra-cresol. The resulting high purity i7n -cresol is then alkylated with isobutylene to produce 2 (i-dii-tert-huty -para-cmso (BHT), which is used as an antioxidant in foods, gasoline, and mbber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

Isopropyl Ether. Isopropyl ether is manufactured by the dehydration of isopropyl alcohol with sulfuric acid. It is obtained in large quantities as a by-product in the manufacture of isopropyl alcohol from propylene by the sulfuric acid process, very similar to the production of ethyl ether from ethylene. Isopropyl ether is of moderate importance as an industrial solvent, since its boiling point Hes between that of ethyl ether and acetone. Isopropyl ether very readily forms hazardous peroxides and hydroperoxides, much more so than other ethers. However, this tendency can be controlled with commercial antioxidant additives. Therefore, it is also being promoted as another possible ether to be used in gasoline (33). 

Gasoline is a mixture of different compounds. A typical blend contains nearly 200 different hydrocarbons and additives such as antioxidants and antiknock agents. Thirteen of the chemicals commonly found in gasoline (nine hydrocarbons and four additives) are regulated as hazardous substances under CERCLA. Table 18.1 lists the chemicals along with the values of toxicity, water solubility, vapor pressure, and biodegradability.19... 

Studies of the hydrogenation of aromatic nitroso compounds have rarely been published. One of the earliest studies is the Pd/C catalyzed hydrogenation of p-nitrosothymol to its corresponding amine (100%) in ethanol at 1 atm hydrogen.289 Useful antioxidants and gasoline stabilizers are made from diamines, which can be produced by hydrogenating their relatively easily formed nitroso derivatives.290 As a result, the hydrogenation of 4-nitroso-diphenylamine has been studied more heavily than others.291-293... 

Metal deactivation, in antidegradant selection, 22 787 Metal deactivators antioxidants, 3 115 in gasoline, 22 407 for lubricating oil and grease, 15 221 Metaldehyde, 2 103... 

Uses Intermediate for dyes and antioxidants inhibits gum formation in gasoline corrosion inhibiter organic synthesis (preparation of p-phenylenediamine). 

Anisole Additives in gasoline to boost octane, used for the production of dyes, agricultural chemicals and antioxidants. 

Hindered phenol and phenylenediamine (PDA) compounds are commonly used and quite effective at preventing free-radical oxidative degradation of fuel. They can be used in gasoline, kerosene, jet fuel, and certain distillates and lubricants. Often, a synergistic effect can be obtained by using a combination of a hindered phenol and a phenylenediamine antioxidant in the same application. 

Hindered phenol compounds usually possess alkyl groups on ortho and para sites. The alkyl groups are typically t-butyl or methyl in functionality. The lower cost of hindered phenol antioxidants makes them attractive for use in fuel applications. In gasoline, hindered phenols are typically used at treat rates of 5 to 50 ppm. The limitations placed on jet fuel additives often control the rate at which phenolic antioxidants can be used. 

Perform as an effective substitute for a hindered phenol or phenylenediamine antioxidant in inhibiting free radical reactions in gasoline or jet fuel. 

The formation of additional gums in gasoline can be minimized by treating fuel with an antioxidant... 

Hydrocarbon oxidation may also be considered a free radical chain-type reaction. At elevated temperatures, hydrocarbon free radicals (R) are formed which react with oxygen lo form peroxy radicals (R(X These, in turn, take up a hydrogen atom from the hydrocarbon to form a hydroperoxide (ROOH) and another hydrocarbon free radical. The cycle repeals itself with the addition of oxygen. The unstable hydroperoxides remaining are the major points for degradation and lead to rancidity and color development in oils, fats, and waxes decomposition and gum formation in gasolines sludging in lubricants and breakdown of plastics and rubber products. Antioxidants, such as amines and phenols, are often introduced into hydrocarbon systems in order lo prevent this free radical oxidation sequence. 

Figure 2. The chemical structures of the two different types of antioxidants used in gasoline are phenylenediamines (PDA) and hindered phenols (such as BHT).

The substituted phenols and cresols constitute about half the total volume of this group. Para-t-butylphenol is produced by the alkylation of phenol with isobutylene. The principal applications for this derivative are in the manufacture of modified phenolic resins for the rubber industry and in surface coatings. BHT is obtained from isobutylene and p-cresol. Technical-grade BHT is an antioxidant for plastics and elastomers, and is a gum inhibitor in gasoline. Food-grade BHT is an antioxidant in edible oils, preserves, and many other foods. 2,6-Di-t-butylphenol is used to produce a wide range of plastics additives, antioxidants, and gasoline additives. 

Use Intermediate, antioxidant, satisfies ASTM D910-64T for use as antioxidant in aviation gasoline. 

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