Gum formation

Finally, the determination of the induction period (NF M 07-012) also reveals the potential of gum formation during storage. The fuei sampie is contained in a bomb filled with oxygen at 100°C, under a pressure of 7 bar and the oxygen pressure is monitored with time. The time corresponding to the first drop in pressure is noted, symptomatic of incipient oxidation. If no further events take place, the test is stopped after 960 minutes. This time corresponds thus to the maximum induction period. 

These compounds can be malodorous as in the case of quinoline, or they can have a plecisant odor as does indole. They decompose on heating to give organic bases or ammonia that reduce the acidity of refining catalysts in conversion units such as reformers or crackers, and initiate gum formation in distillates (kerosene, gas oil). 

Solvent Extraction - Solvent extraction uses solvents to dissolve and remove aromatics from lube oil feed stocks, improving viscosity, oxidation resistance, color, and gum formation. A number of different solvents are used, with the two most common being furfural and phenol. Typically, feed lube stocks are contacted with the solvent in a packed tower or rotating disc contactor. Each solvent has a different solvent-to-oil ratio and recycle ratio within the tower. 

Autoxidation. Self-catalyzed oxidation in the presence of air. Autoxidation can be initiated by heat, light, or a catalyst. The commercial production of phenol and acetone from cumene is autoxidation. Other examples include the degradation of polymers exposed to sunlight for long periods of time gum formation in lubricating oils and gasoline and the spoilage of fats. 

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

Gums Conjugated diolefins and other olefinic compounds formed during catalytic and thermal cracking processes heterocyclic compounds present in fuel can also initiate gum formation... 

Thermal and catalytically cracked gasoline fractions can contain significant concentrations of phenols, low-molecular-weight organic acids, and alkyl and aryl mercaptans. All of these compounds can initiate gum formation in gasoline. Caustic treatment readily removes these compounds. 

Cracked gasoline FCC gasoline Composed of paraffinic, olefinic, and aromatic compounds branched compounds are present in a relatively high amount typically has a higher RON than MON high-olefin-content FCC gasoline can lead to gum formation and fuel color degradation. 

Antioxidant Helps prevent oxidative degradation and gum formation in fuel... 

Oxygen-containing impurities such as phenols and naphthenic acids can adversely affect water separation properties and initiate gum formation. No limit presently exists to control the amount of oxidized organic compounds found in jet fuel. However, tests for existent gums, neutralization number, and water separation indirectly limit the presence of oxygenated materials in jet fuel. 

Antioxidants - prevent gum formation in fuel. The approved additives are generally phenolic based. Use is mandatory in aviation gasoline. Antioxidants are permitted in civil and military jet fuels. Antioxidants are mandatory in hydroprocessed British and U.S. military jet fuels as well as in international civil Jet A-l. 

Increase in gum formation of stored gasoline and diesel fuel... 

Diesel fuel containing cetane improver generates higher levels of residual carbon than untreated fuel. This is probably due to the fact that the cetane improver decomposes to catalyze fuel polymerization and gum formation during fuel pyrolysis. 

Detergents used in diesel fuel help to control deposit formation on fuel injector nozzles and act to prevent corrosion of the nozzle orifices. Diesel fuel detergents also aid in preventing deposit and gum formation on high-pressure fuel injector parts. 

Fuel olefins have been implicated as the primary cause of deposits in gasoline fuel injectors and carburetors. High-boiling-point, high-molecular-weight aromatic components have also been shown to contribute to intake system deposit and gum formation. Once formed, other compounds in the fuel can adhere to these deposits to form an amorphous-type deposit. 

The result of this testing provides information on whether fuel components are susceptible to attack by oxygen. If fuel components do react with oxygen, then further degradation of the fuel can be expected. The final result could be gum formation, fuel discoloration, and fuel system deposits. 

ANTIOXIDANTS. Usually an organic compound added to various types of materials, such as rubber, natural fats and oils, food products, gasoline, and lubricating oils, for the purposes of retarding oxidation and associated deterioration, rancidity, gum formation, reduction in shelf life, etc. 

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. 

Stability—In petroleum products, the resistance to chemical change. Gum stability in gasoline means resistance to gum formation while in storage. Oxidation stability in lubricating oils and other products means resistance to oxidation to form sludge or gum in use. 

Gasoline hydrorefining is applied to remove polymerizable by-products (isoprene, cyclopentadiene, styrene and indene) from stream-cracked gasoline to prevent gum formation. Partial hydrogenation of dienes to monoalkenes and the hydrogenation of... 

Storage stability (or storage instability) the ability (inability) of a liquid to remain in storage over extended periods of time without appreciable deterioration as measured by gum formation and the depositions of insoluble material (sediment). 

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