Copper ions, deactivation

In addition to bonding with the metal surface, triazoles bond with copper ions in solution. Thus dissolved copper represents a "demand" for triazole, which must be satisfied before surface filming can occur. Although the surface demand for triazole filming is generally negligible, copper corrosion products can consume a considerable amount of treatment chemical. Excessive chlorination will deactivate the triazoles and significantly increase copper corrosion rates. Due to all of these factors, treatment with triazoles is a complex process. 

The second example is the electro-oxidative polymerization of phenols bearing functional substituents. It is known that salicylic acid forms a stable chelate with copper ion, thus the copper catalyst is deactivated and the polymerization does not occur. On the other hand, salicylic acid was electro-oxidatively polymerized to produce the poly(phenyleneoxide) bearing carboxylic group. 

Metal Ion Deactivators. These generally chelate ions of copper and the transition metals which might otherwise catalyze the decomposition of hydroperoxides to free radicals,... 

Depressants (or deactivators) are chemicals that ensure that undesired particles remain hydrophilic and therefore do not get floated. Conversely to the activation of zinc sulfide by copper ions above, zinc ions from zinc sulfate act as a depressant for zinc sulfide. Another example is the use of cyanide to complex with copper and prevent adsorption of collectors in the flotation of base-metal sulfides with xanthates. There are many other depressants but they tend to be quite specific to one of a few types of minerals. In some cases, such as some uses of cyanide as a depressant, the mechanism of depressant action remains unclear. 

Copper ions in zeolites are mainly responsible for NO reduction activity therefore, deactivation would occur if alteration of their state or the zeolite structure were accompanied. The origin of the deactivation of Cu-exchanged zeolites due to their hydrothermal excursion has been published in several literatures. Solid state Al MAS NMR spectra of a Cu-MFI catalyst appeared to have a loss of 23% of framework aluminum after hydrothermal aging at 410°C in flowing 10% H20/90% air for 113 h. Kharas et reported the formation of... 

Since Cu ions on the zeolite surface exist in an isolated environment, they may interact with the sulfate species on the catalysts deactivated by SOj. The sulfate groups might partially surround the copper ions, as previously supested by Choi et al. [37] and Hamada et al. [38]. The sulfate may also have some characteristics of a coordinate covdent bond, where Cu ions and sulfate species may act as a Lewis acid and base, respectively [39], Ligands such as HjO, NHj, (C2Hj)3P, CO molecules and Cf, CN, OH , NOj, and C204 ions should at least contain a lone pair of electron to form a coordinate covalent bond between metal ions [40]. It should be noted that the sulfate catalyst species formed on the catalysts deactivated by SO2 contains lone electron pairs on O atoms which surround S atom of SO4 groups. Therefore, it is expected that the electrostatic interaction between Cu ions and sulfate species probably influences the local structure of Cu ions on the zeolite catalyst surface. 

This paper deals with the hydrothermal deactivation, under an air + 10 vol. % H2O mixture between 923 and 1173 K, of Cu-MFI solids, catalysts for the selective reduction of NO by propane. Fresh and aged solids were characterized by various techniques and compared with a parent H-ZSM-5 solid. The catalytic activities were measured in the absence and in the presence of water. The differences between fresh and aged Cu-ZSM-5 catalysts (destruction of the framework, extent of dealumination...) were shown to be small in spite of the strong decreases in activity. Cu-ZSM-5 is more resistant to dealumination than the parent H-ZSM-5 zeolite. The rate of NO reduction into N2 increases with the number of isolated Cu VCu ions. These isolated ions partially migrate to inaccessible sites upon hydrothermal treatments. At very high aging temperatures a part of the copper ions agglomerates into CuO particles accessible to CO, but these bulk oxides are inactive. Under catalytic conditions and in the presence of water, dealumination is observed at a lower temperature (873 K) than under the (air + 10 % H2O) mixture, because of nitric acid formation linked to NO2 which is either formed in the pipes of the apparatus or on the catalyst itself... 

The partial substitution of the copper ions gives rise to a decrease in GBL conversion, with the following order Cu/Cd/Cr > Cu/Mg/Cr > Cu/Zn/Cr. In particular, cadmium gives rise to considerable deactivation and the magnesium puts down edmost completely the hydrogenolis activity, while smaller differences are observed with the zinc. 

Standard application of metal deactivator is jacketing of the cable because it contacts to copper wire. Copper ions can accelerate the degradation by changing valance. 

Metal deactivators act as electron donors to form a stable complex with copper ions and the degradation reaction is retarded. Here is an example of adding 0.2% copper ion and with/without 0.2% IRGANOX MD 1024 (Figure 6.9). IRGANOX MD 1024 helps to retain the mechanical properties. 

Metal ion deactivators (MD) act, primarily, by retarding metal-catalyzed oxidation of polymers (see Scheme 1, reaction 4c). They are used in polymers that are in contact with metals such as copper in wires and power cables. Metal deactivators are normally polyfunctional metal chelating compoimds (eg, AOs 33,... 

Unfortunately, Cu-ZSM-5 catalyst suffers from thermal and water deactivation leading to segregation of extra-framework copper ions, and/or to the sintering of CuO-like species. To improve the durability or the low-temperature activity. 

Reversible atom transfer free radical polymerization of n-butyl acrylate was conducted in miniemulsion systems using the water-soluble initiator 2,2 -azobis(2-amidinopropane) dihydrochloride (V-50) and the hydrophobic ligand 4,4 -di(5-nonyl)-4,4 -bipyridine to form a complex with the copper ions [67, 80]. The resultant Cu(II) complex has a relatively large solubility in the continuous aqueous phase, but this should not impair its capability of controlling the free radical polymerization. This is because the rapid transport of the Cu(II) complex between the dispersed organic phase and the continuous aqueous phase assures an adequate concentration of the free radical deactivator. As a consequence, the controlled free radical polymerization within the homogenized monomer droplets can be achieved. 

Efficient metal (ion) deactivators are based on their ability to form stable complexes with the metal, especially with copper ions. Mainly polyolefins and mbbers need to be stabilized by those metal (ion) deactivators that must resist extraction in aqueous surroundings. An important commercial product is 2, 3-bis[[3-[3,5-di- ert-butyl-4-hydroxyphenyl]propionyl]] pro-pionohydrazide (Irganox MD-1024, BASF). 

The copper sulfide formed on the surface of the sphalerite mineral reacts readily with the xanthate, and forms insoluble copper xanthate, which makes the sphalerite surface hydro-phobic. Such a reaction for activating sphalerite occurs whenever the activating ions are present in the solution. It is thus necessary to deactivate sphalerite (to prevent the occurrence of natural activation) in the case of some ores. With lead-zinc ores, for example, natural activation occurs due to Pb2+ in solution... 

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. 

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