Complexes metal deactivators

Metal Deactivation. Compounds capable of forming coordination complexes with metal ions are needed for this purpose. A chelating agent such as ethylene-diaminetetraacetic acid (EDTA) is a good example. 

Metal Deactivators. The abiUty of metal ions to catalyse oxidation can be inhibited by metal deactivators (19). These additives chelate metal ions and increase the potential difference between the oxidised and reduced states of the metal ions. This decreases the abiUty of the metal to produce radicals from hydroperoxides by oxidation and reduction (eqs. 15 and 16). Complexation of the metal by the metal deactivator also blocks its abiUty to associate with a hydroperoxide, a requirement for catalysis (20). 

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). 

Metal deactivators—Organic compounds capable of forming coordination complexes with metals are known to be useful in inhibiting metal-activated oxidation. These compounds have multiple coordination sites and are capable of forming cyclic strucmres, which cage the pro-oxidant metal ions. EDTA and its various salts are examples of this type of metal chelating compounds. 

Retard efficiently oxidation of polymers catalysed by metal impurities. Function by chelation. Effective metal deactivators are complexing agents which have the ability to co-ordinate the vacant orbitals of transition metal ions to their maximum co-ordination number and thus inhibit co-ordination of hydroperoxides to metal ions. Main use of stabilisation against metal-catalysed oxidation is in wire and cable applications where hydrocarbon materials are in contact with metallic compounds, e.g. copper. 

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. 

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... 

Trace levels of soluble metal compounds, particularly copper, catalyze the oxidative degradation of gasoline by promoting the formation of gums and deposits. Metal deactivators overcome this problem by chelating the metal and rendering it inactive. The most widely used metal deactivator is N, N -disalicylidene-l,2-propanediamine, the copper complex of which is shown in Figure 3. 

Figure 3. Structure of the copper complex of the most widely used metal deactivator N, N -disalicylidene-l,2-propanediamine.

The deoxo reaction, performing the reduction of dioxygen with hydrogen, usually catalysed by a noble metal catalyst, was also reported to occur with NaY encapsulated complexes of Cu(embelin) (18) and 2-aminobenzimidazole (19).[134] The Cu(embelin) complex entrapped in NaY is a stable catalyst, that showing enhanced activity compared with the homogeneous case and may be reused many times, the corresponding benzimidazole complex is deactivated rapidly. 

Careful and extensive kinetic studies have been carried out only for hydroaluminations with dialkyl-aluminum hydrides. Adequate kinetic information is still lacking on transition metal catalyzed hydroalumination and on the hydroaluminating action of complex metal hydrides, MAlRnH4 n. Preliminary studies on the nickel-catalyzed process have revealed an unstable rate behavior brought about by the deactivation of the catalyst with time. ... 

Jet fuels are aviation fuels used mainly by the United States and other North Atlantic Treaty Organization (NATO) nations for military establishments. Other fuels called Jet A and Jet A-1 are closely related fuels used by commercial airlines. JP are a complex mixture of primarily aliphatic (but also aromatic) hydrocarbons, derived from crude oil and/or kerosene by refining and adding various other additives such as fuel icing inhibitors, antioxidants, corrosion inhibitors, metal deactivators, and static dissipaters. Gas chromatographic analysis of JP-8, the most recent JP, indicates that it is made up of complex mixture of 9 to 17 different hydrocarbons, including thousands of isomers and three to six performance additives. They are generally colorless liquids and smell like kerosene. 

It has been found that l-butyl-3-methylimidazolium iodide salt can serve simultaneously as a specific stabilizer to protect the transition metal complex against deactivation, a promoter to increase the catalytic performance and a reaction medium to recycle the catalyst. 

Antiozonant Properties. Aromatic secondary diamines are the only class of organic chemicals able to reduce efficiently the ozone crack growth of vulcanizates under dynamic conditions and be acceptable at the same time from both the technical and toxicological points of view. The presence of a secondary aromatic amine moiety itself in a molecule is not a sufficient condition to attain antiozonants efficiency. (E.g., secondary monomaines are only antioxidants and flex-crack inhibitors without appreciable antiozonant activity. On the other hand, all N,N -disubstituted PD antiozonants are also efficient antoxidants and most of them also act as flex-crack inhibitors (1). Both these stabilization activities have to be considered in the complex antiozonant mechanism, together with some metal deactivating activity. 

Complexing agents N,N -bis(o-hydroxybenzal)oxalyl dihydrazide Metal deactivation (not apphcable)... 

Metal deactivators are used in situations where plastics come into contact with metals such as polyethylene cable covers. These antioxidants combine with metal ions to form a stable complex at the interface, thereby preventing metals from accelerating degradation of the polymer. 

Phthalocyanine complexes within zeolites have also been prepared by the ship-in-a-bottle method (see Section 6.6), and have subsequently been investigated as selective oxidation catalysts, where their planar metal-N4 centres mimic the active sites of enzymes such as cytochrome P450, which is able to oxidize alkanes with molecular oxygen. Cobalt, iron and ruthenium phthalocyanines encapsulated within faujasitic zeolites are active for the oxidation of alkanes with oxygen sources such as iodosobenzene and hydroperoxides. Following a similar route, Balkus prepared Ru(II)-perchloro- and perfluorophthalocyanines inside zeolite X and used these composites for the selective catalytic oxidation of alkanes (tert-butylhydroperoxide). The introduction of fluorinated in place of non-fluorinated ligands increases the resistance of the complex to deactivation. 

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