Metal basic carbonates

As mentioned earlier, it has proven difficult to precipitate uniform metal (hydrous) oxides by direct mixing of solutions of metal salts and bases, especially of concentrated ones. Instead, it is possible to control the generation of hydroxide ions in situ, which can be achieved if certain organic compounds, such as formamide or urea, are slowly decomposed in aqueous solutions of metal salts. The rate of these processes depends on the pH, temperature, concentration of the reactants, and the presence or absence of metal complexing agents. In particular, precipitations caused by reactions in solutions of urea have been widely employed, although the products consist primarily of metal carbonates or basic metal carbonates. For this reason, this method is described in more detail in Chapter 7.1 of this volume. 

Rojas-Cervantes, ML Alonso. L Diaz-Teran, J Lopez-Peinado, AJ Martin-Aranda, RM Gomez-Serrano, V. Basic metal-carbons catalysts prepared by sol-gel method. Carbon. 2004 42. 1575-1582. 

Yang, J., Guan, Y., Verhoeven, T., et al. (2009). Basic Metal Carbonate Supported Gold Nanoparticles Enhanced Performance in Aerobic Alcohol Oxidation, Green Chem., 11, pp. 322-325. 

Most metal carbonates are insoluble and they are precipitated either as the simple carbonate or as the basic carbonate when... 

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

Basic copper carbonate is essentially iasoluble ia water, but dissolves ia aqueous ammonia or alkaU metal cyanide solutions. It dissolves readily ia mineral acids and warm acetic acid to form the corresponding salt solution. 

As you can see from the tables in Chapter 1, few metals are used in their pure state -they nearly always have other elements added to them which turn them into alloys and give them better mechanical properties. The alloying elements will always dissolve in the basic metal to form solid solutions, although the solubility can vary between <0.01% and 100% depending on the combinations of elements we choose. As examples, the iron in a carbon steel can only dissolve 0.007% carbon at room temperature the copper in brass can dissolve more than 30% zinc and the copper-nickel system - the basis of the monels and the cupronickels - has complete solid solubility. 

Those basic matrix selection factors are used as bases for comparing the four principal types of matrix materials, namely polymers, metals, carbons, and ceramics, listed in Table 7-1. Obviously, no single matrix material is best for all selection factors. However, if high temperatures and other extreme environmental conditions are not an issue, polymer-matrix materials are the most suitable constituents, and that is why so many current applications involve polymer matrices. In fact, those applications are the easiest and most straightforward for composite materials. Ceramic-matrix or carbon-matrix materials must be used in high-temperature applications or under severe environmental conditions. Metal-matrix materials are generally more suitable than polymers for moderately high-temperature applications or for modest environmental conditions other than elevated temperature. 

Carbon dioxide was once thought essential for the rusting of ferrous metals (viz. the carbonic acid theory of rusting) but is now considered of relatively minor importance . However, basic zinc carbonate is frequently found in the corrosion products of zinc and small amounts of siderite (FeCOs) are found in ferrous rusts. 

It has been found that red lead, litharge and certain grades of metallic lead powder render water alkaline and inhibitive this observation has been confirmed by Pryor . The effect is probably due to a lead compound, e.g. lead hydroxide, in solution. Since, however, atmospheric carbon dioxide converts these lead compounds into insoluble basic lead carbonate, thereby removing the inhibitive materials from solution, these pigments may have only limited inhibitive properties in the absence of soap formation. 

The pale green product is called basic copper carbonate and is responsible for the green patina of copper and bronze objects (Fig. 16.13). The patina adheres to the surface, protects the metal, and has a pleasing appearance. 

The reddish metal was already known in prehistoric times. It occasionally occurs as a native metal, but mostly in conspicuous green ores, from which it is extracted relatively easily. It is convenient to work, but not very hard. Not very optimal as a tool ("Otzi the Iceman" had a copper axe with him). Only through the addition of tin is the more useful bronze obtained. Its zinc alloy is the versatile and widely used brass. Copper is one of the coinage metals. Water pipes are commonly made of copper. Its very good thermal and electrical conductivity is commonly exploited (cable ), as well as its durability (roofs, gutters), as the verdigris (basic copper carbonate) protects the metal. Cu phthalocyanines are the most beautiful blue pigments. Seems to be essential to all life as a trace element. In some molluscs, Cu replaces Fe in the heme complex. A 70-kg human contains 72 mg. 

Freshly cast lead has a bright, silvery appearance. On exposure to the atmosphere, however, lead in the surface layer combines with atmospheric oxygen and carbon dioxide to form a dark, stable gray coating of mixed lead oxide and basic lead carbonate. This layer usually protects the metal from further oxidation and corrosion (see Fig. 38). Protected by a weathered surface layer, solid lead is stable to further corrosion. Lead is also very ductile and soft, being the softest metal known in antiquity. It is mainly because of these properties that lead was widely used for building, to make pipes and roofs, and in naval construction, for example. Solid lead flows, albeit very... 

The effect of metal basicity on the mode of reactivity of the metal-carbon bond in carbene complexes toward electrophilic and nucleophilic reagents was emphasized in Section II above. Reactivity studies of alkylidene ligands in d8 and d6 Ru, Os, and Ir complexes reinforce the notion that electrophilic additions to electron-rich compounds and nucleophilic additions to electron-deficient compounds are the expected patterns. Notable exceptions include addition of CO and CNR to the osmium methylene complex 47. These latter reactions can be interpreted in terms of non-innocent participation of the nitrosyl ligand. 

Carbyne complex chemistry of osmium and ruthenium is discussed in this section. These studies demonstrate clearly the parallels that exist between the metal-carbon bonds in carbene and carbyne complexes and again emphasize the importance of metal basicity in determining complex reactivity. 

In the propagation process of Ziegler-Natta polymerization, the insertion of olefin into a metal-carbon bond is the most important basic step, but many questions concerning to this process remained unanswered for a long time. 

Dutch An obsolete process for making basic lead carbonate pigment (white lead) by exposing metallic lead to vinegar and carbon dioxide. Reportedly first described by Theophrastos around 300 BC. Also known as the Stack process because the metal ingots were arranged in vertical stacks. See also Thompson-Stewart. 

The basic assumptions common to most mechanism studies relative to transition metal catalyzed polymerizations are as follows (i) The mechanism is essentially monometallic and the active center is a transition metal-carbon bond.13-15,18,19 (ii) The mechanism is in two stages coordination of the olefin to the catalytic site followed by insertion into the metal-carbon bond through a cis opening of the olefin double bond.13,20,21... 

Many promoters have been used to improve the performance of Ni/Al203 catalysts. The effect of the basic oxides of Na, K, Mg, and Ca on Ni/Al203 was examined by a number of authors (178,203,211 -213). They found that these added oxides markedly decrease the carbon deposition. The kinetics results showed that the added metal oxides changed the reaction order in CH4 from negative to positive and that in C02 from positive to negative. This observation implies that the surface of a nickel catalyst incorporating basic metal oxides is abundant in adsorbed C02, whereas the surfaces devoid of these oxides are abundant in adsorbed CH4 (178). The coverage of nickel with C02 is most likely unfavorable to CH4 decomposition... 

MgO is a basic metal oxide and has the same crystal structure as NiO. As a result, the combination of MgO and NiO results in a solid-solution catalyst with a basic surface (171,172), and both characteristics are helpful in inhibiting carbon deposition (171,172,239). The basic surface increases C02 adsorption, which reduces or inhibits carbon-deposition (Section ALB). The NiO-MgO solid solution can control the nickel particle sizes in the catalyst. This control occurs because in the solid solution NiO has strong interactions with MgO and, as indicated by TPR data (26), the former oxide can no longer be easily reduced. Consequently, only a small amount of NiO is expected to be reduced, and thus small nickel particles are formed on the surface of the solid solution, smaller than the size necessary for coke formation. Indeed, the nickel particles on a reduced 16.7 wt% NiO/MgO solid-solution catalyst were too small to be observed by TEM (171). Furthermore, two additional important qualities stimulated the selection of MgO as a support its high thermal stability and low cost (250,251). 

Elliott et a/.71,72,78,96 conducted extensive investigations on the homogeneous WGS reaction using various metal carbonates as well as other basic catalysts. Testing was carried out in a 1-liter autoclave at 500 psig CO pressure ( 35 atm) with 500 g of H20 and 0.32 M solutions of salts in the temperature range 200 100 °C. They... 

To uncover new reaction pathways towards unprecedented target materials, the understanding of structure formation principles is important. One of the lead structural principles in lithium organic chemistry is the /X3-capping of the metalated carbon atom Ca to a lithium triangle. This motif can further aggregate to form deltahedra. The tetrahedra and octahedra can either be free of solvent or be coordinated by Lewis-basic donor molecules... 

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