Metal oxides basicity

Sulphur and oxygen are interchangeable in sulphides and oxides. Metal oxides (basic) and non-metal oxides (acidic) combine to form salts. Likewise metal sulphides may combine with sulphides of weakly metallic or non-metallic elements to form salts, the so-called thio-salts, or sulpho-salts. Thio-salts of a few of the elements, notably tin, are very well defined. Stannous sulphide does not form a thio-salt but addition of sulphur converts it to stannic sulphide which does form a soluble thio-salt with the sulphide of an alkali metal. 

Another common kind of reaction of oxides is the combination of metal oxides (basic anhydrides) with nonmetal oxides (acid anhydrides), with no change in oxidation states, to form salts. 

Reaction of a metal oxide (basic) with a nonmetal oxide (acidic) forms a salt. 

Water undergoes reactions with many metals and nonmetals, depending on their reactivity. Water reacts with metal oxides (basic anhydrides) to form bases (hydroxides). 

The first ceramic oxygen membranes were discovered by Nernst [2] in 1899 in the form of mixrnres of zirconia and rare-earth metal oxides. Basically, oxygen transport in oxide ceramics can be realized in three variants (Fig. 1). Materials... 

Some common metal oxides (basic anhydrides) and their corresponding bases. 

In order to decrease ZSM-5 acidic strength, a little of metallic oxides, basic La203 or MgO, were loaded over Si02-CLD/ZSM-5. This may effectively reduce the side-reactions of both disproportionation and dealkylatioa Moreover, the amount of loaded La203 or MgO over ZSM-5 relates to catalytic activity and selectivity. The selectivity of /lara-methyl ethylbenzene and the selectivity of total methyl ethylbenzene increase with... 

Meta.1 Conta.mina.nts and Ash. Alkali metals form basic oxides that are very reactive toward acidic species such as the acid gases, siHcates, and alurninates. These form stable salts with acid gases if the off-gas contains such gases. Sodium, the most common of these metals, prefers to form chlorides ahead of sulfates. Sodium carbonate only forms in the absence of haHdes and sulfur oxides, SO. There usually is too Htde NO present to form nitrates (see Sodium compounds). 

Alkali metal haHdes can be volatile at incineration temperatures. Rapid quenching of volatile salts results in the formation of a submicrometer aerosol which must be removed or else exhaust stack opacity is likely to exceed allowed limits. Sulfates have low volatiHty and should end up in the ash. Alkaline earths also form basic oxides. Calcium is the most common and sulfates are formed ahead of haHdes. Calcium carbonate is not stable at incineration temperatures (see Calcium compounds). Transition metals are more likely to form an oxide ash. Iron (qv), for example, forms ferric oxide in preference to haHdes, sulfates, or carbonates. SiHca and alumina form complexes with the basic oxides, eg, alkaH metals, alkaline earths, and some transition-metal oxidation states, in the ash. 

In the vapor phase, acetone vapor is passed over a catalyst bed of magnesium aluminate (206), 2iac oxide—bismuth oxide (207), calcium oxide (208), lithium or 2iac-doped mixed magnesia—alumina (209), calcium on alumina (210), or basic mixed-metal oxide catalysts (211—214). Temperatures ranging... 

Antimony trioxide is insoluble in organic solvents and only very slightly soluble in water. The compound does form a number of hydrates of indefinite composition which are related to the hypothetical antimonic(III) acid (antimonous acid). In acidic solution antimony trioxide dissolves to form a complex series of polyantimonic(III) acids freshly precipitated antimony trioxide dissolves in strongly basic solutions with the formation of the antimonate ion [29872-00-2] Sb(OH) , as well as more complex species. Addition of suitable metal ions to these solutions permits formation of salts. Other derivatives are made by heating antimony trioxide with appropriate metal oxides or carbonates. 

In general, hydrated borates of heavy metals ate prepared by mixing aqueous solutions or suspensions of the metal oxides, sulfates, or halides and boric acid or alkali metal borates such as borax. The precipitates formed from basic solutions are often sparingly-soluble amorphous soHds having variable compositions. Crystalline products are generally obtained from slightly acidic solutions. 

An extremely wide variety of catalysts, Lewis acids, Brmnsted acids, metal oxides, molecular sieves, dispersed sodium and potassium, and light, are effective (Table 5). Generally, acidic catalysts are required for skeletal isomerization and reaction is accompanied by polymerization, cracking, and hydrogen transfer, typical of carbenium ion iatermediates. Double-bond shift is accompHshed with high selectivity by the basic and metallic catalysts. 

In this method, a metal oxide or hydroxide is slurried in an organic solvent, neodecanoic acid is slowly added, and the mixture is refluxed to remove the water. Salts that are basic can be prepared by using less than stoichiometric amounts of acid. This method has been used in the preparation of metal salts of silver (80) and vanadium (81). The third method of preparation is similar to the fusion process, the difference is the use of finely divided metal as the starting material instead of the metal oxide or hydroxide. This method has been appHed to the preparation of cobalt neodecanoate (82). Salts of tin (83) and antimony (84) have been prepared by the fusion method, starting with lower carboxyHc acids, then replacing these acids with neodecanoic acid. 

Dyes and Pigments. Several thousand metric tons of metallated or metal coordinated phthalocyanine dyes (10) are sold annually in the United States. The partially oxidized metallated phthalocyanine dyes are good conductors and are called molecular metals (see Semiconductors Phthalocyanine compounds Colorants forplastics). Azo dyes (qv) are also often metallated. The basic unit for a 2,2 -azobisphenol dye is shown as stmcture (11). Sulfonic acid groups are used to provide solubiHty, and a wide variety of other substituents influence color and stabiHty. Such complexes have also found appHcations as analytical indicators, pigments (qv), and paint additives. 

Catalysts vary both in terms of compositional material and physical stmcture (18). The catalyst basically consists of the catalyst itself, which is a finely divided metal (14,17,19) a high surface area carrier and a support stmcture (see Catalysts, supported). Three types of conventional metal catalysts are used for oxidation reactions single- or mixed-metal oxides, noble (precious) metals, or a combination of the two (19). 

Critical factors. The basic cause of incomplete fusion is failure to elevate the temperature of the base metal, or of the previously deposited weld metal, to the melting point. In addition, failure to flux metal oxides or other foreign substances adhering to metal surfaces properly may interfere with proper fusion. 

Accelerated sulphur systems also require the use of an activator comprising a metal oxide, usually zinc oxide, and a fatty acid, commonly stearic acid. For some purposes, for example where a high degree of transparency is required, the activator may be a fatty acid salt such as zinc stearate. Thus a basic curing system has four components sulphur vulcanising agent, accelerator (sometimes combinations of accelerators), metal oxide and fatty acid. In addition, in order to improve the resistance to scorching, a prevulcanisation inhibitor such as A -cyclohexylthiophthalimide may be incorporated without adverse effects on either cure rate or physical properties. 

A number of basic materials such as hydroxides, hydrides and amides of alkaline and alkaline earth metals and metal oxides such as zinc oxide and antimony oxide are useful catalysts for the reaction. Acid ester-exchange catalysts such as boric acid, p-toluene sulphonic acid and zinc chloride are less... 

Finally, the strongly basic metal oxides react with silicon dioxide to form a glassy product ... 

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