Metal deactivators, antioxidants

Metal-deactivating antioxidants. Transition metal compounds decompose hydroperoxides with the formation of free radicals, thereby increasing the rate of oxidation. Such an enhanced oxidation can be slowed down by the addition of a compound that interacts with metal ions to form complexes that are inactive with respect to hydroperoxides. Diamines, hydroxy acids, and other bifunctional compounds exemplify this type of antioxidants. 

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... 

The stabili2ation of polyolefins used to insulate copper conductors requires the use of a long-term antioxidant plus a copper deactivator. Both A[,Ar-bis(3,5-di-/ A-butyl-4-hydroxycinnamoyl)hydra2ine (29) and 2,2 -oxamidobisethyl(3,5-di-/ A-butyl-4-hydroxycinnamate) (30) are bifimctional. They are persistent antioxidants that have built-in metal deactivators. Oxalyl bis(ben2yhdenehydra2ide) (28) is an effective copper deactivator when part of an additive package that includes an antioxidant. 

It is possible to deactivate a metal ioa by adding a compouad such as disahcyhdeae alkyl diamiae, which readily forms a chelate with most metal atoms to reader them iaeffective. Metal deactivator has beea showa to reduce oxidatioa deposits dramatically ia the JFTOT test and ia single tube heat exchanger rigs. The role of metal deactivator ia improving fuel stabiUty is complex, siace quantities beyond those needed to chelate metal atoms act as passivators of metal surfaces and as antioxidants (13). 

The peroxide decomposer will drastically reduce the number of radicals, which can then be more effectively mopped up by the chain-breaking materials. A widely used combination is 4-methyl-2,6,di-t-butylphenol and dilauryl thiodipropionate. It is possible to envisage most powerful combinations where a chain-breaking antioxidant, a regenerating agent, a peroxide decomposer, a metal deactivator and an ultraviolet absorber are all employed together. 

There have been some examples of the use of LDMS applied to the analysis of compounds separated via TLC, although not specifically dealing with polymer additives [852]. Dewey and Finney [838] have described direct TLC-spectroscopy and TLC-LMMS as applied to the analysis of lubricating oil additives (phenolic and amine antioxidants, detergents, dispersants, viscosity index improvers, corrosion inhibitors and metal deactivators). Also a series of general organics and ionic surfactants were analysed by means of direct normal-phase HPTLC-LMMS [837]. Novak and Hercules [858] have... 

The mechanisms of inhibition by peroxide decomposers, metal deactivators, and ultraviolet absorbers are fairly well understood in general terms, although many details of the individual reactions remain to be elucidated. Classifying a preventive antioxidant into one of the three categories above will only rarely describe its entire function. The dual behavior of dialkyl dithiophosphates in the liquid phase has been mentioned. Many other phosphorus- and sulfur-containing antioxidants commonly classified as peroxide decomposers can also act as chain breakers. Similarly, the structure of many metal deactivators and ultraviolet absorbers indicates that they must also have some chain-breaking activity. 

These products have been marketed for many years. They are effective at preventing deposit formation and corrosion of carburetors and fuel injectors, but often do not prevent deposit formation on intake valves. Most products contain an amine-based detergent, demulsifier, and sometimes an antioxidant and metal deactivator. The effective treat rate for preventing deposit formation on carburetors and fuel injectors can range from a minimum of 20 ppm to a maximum of about 75 ppm. 

If a gasoline does not meet this specification, antioxidants can be added to the fuel to provide an increase in induction time. Antioxidant treat rates of 5 to 50 ppm are typical. Also, the addition of a metal deactivator at a 1 to 2 ppm treat rate may improve induction time. 

Although water usually does not emulsify readily with jet fuel, certain compounds added to the fuel to improve performance such as antioxidants, corrosion inhibitors, and metal deactivators may tend to emulsify and hold water in the jet fuel. Also, if... 

Additive A chemical substance added to a product to impart or improve certain properties. Typical fuel additives include antioxidants, cetane improvers, corrosion inhibitors, demulsifiers, detergents, dyes, metal deactivators, octane improvers, and wax crystal modifiers. 

Scheme 2 Schematic presentation of the cyclical oxidation process and some of the main reactions/products formed from the propagating radicals. The antioxidant mechanisms interrupting the oxidative cycles are also shown. AO antioxidant, CB-A chain breaking acceptor, CB-D chain breaking donor, PD peroxide decomposer, UVA UV-absorber, MD metal deactivator...

The nature of existing fuels as a complex liquid mixture of hydrocarbons lends itself well to adjustment of properties by choice of fraction, blending, treatment, etc., so that the properties of the fuel can be tailored to meet the demands of particular applications. The fuels are essentially non-polar organic solvents, and readily dissolve a variety of additives. Thus, military fuels can be based on commercial fuels, but with adjusted properties. For example, JP 8 is essentially identical to commercial Jet A-l, but with the addition of a military additive pack to account for the more demanding military requirements. This includes antioxidants to prevent fuel oxidation, metal deactivators to counteract metals, fuel system icing inhibitor to prevent water in fuel from freezing, and a corrosion inhibitor/lubricity enhancer to prevent corrosion and fuel pump failure.1... 

Fuels— The antioxidant and detergent funetions of Mannieh bases are the ones mainly exploited. They are also claimed to assist in improving storage stability,as metal deactivators," and in reducing soot ignition temperatures." ... 

Metal deactivator. Metal deactivator prevents precipitation of metal ion oxidation reactions and precipitation of insoluble metal compounds. Metal deactivator in combination with other antioxidants, shows strong synergistic effects. Oxygen and moisture present, diffuse through oil film and cause corrosion. Amine derivative, used in the additive has good water-displacing properties. They impede sludge formulation, disperse sediments and reduce corrosion in various fuel systems. 

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