Vanadium physical properties

Several forms of magnesium vanadates have been characterized. Some physical properties ate summarized in Table 27 (28—30) (see also Vanadium AND VANADIUM ADLOYS). 

Table 1. Physical Properties of Some Industrial and Other Selected Vanadium Compounds ...

Vanadium-Sodium Compounds Most Corrosive. Physical property data for vanadates, phase diagrams, laboratory experiments, and numerous field investigations have shown that the sodium vanadates are the lowest melting compounds and are the most corrosive to metals and refractories. These compounds are thought to form by either the vapor phase reaction of NaCI and V2O5 or by the combination of fine droplets of these materials upon the cooler parts of combustion equipment. 

Steel is essentially iron with a small amount of carbon. Additional elements are present in small quantities. Contaminants such as sulfur and phosphorus are tolerated at varying levels, depending on the use to which the steel is to be put. Since they are present in the raw material from which the steel is made it is not economic to remove them. Alloying elements such as manganese, silicon, nickel, chromium, molybdenum and vanadium are present at specified levels to improve physical properties such as toughness or corrosion resistance. 

The basic corrosion behaviour of stainless steels is dependent upon the type and quantity of alloying. Chromium is the universally present element but nickel, molybdenum, copper, nitrogen, vanadium, tungsten, titanium and niobium are also used for a variety of reasons. However, all elements can affect metallurgy, and thus mechanical and physical properties, so sometimes desirable corrosion resisting aspects may involve acceptance of less than ideal mechanical properties and vice versa. 

Loop Tests Loop test installations vary widely in size and complexity, but they may be divided into two major categories (c) thermal-convection loops and (b) forced-convection loops. In both types, the liquid medium flows through a continuous loop or harp mounted vertically, one leg being heated whilst the other is cooled to maintain a constant temperature across the system. In the former type, flow is induced by thermal convection, and the flow rate is dependent on the relative heights of the heated and cooled sections, on the temperature gradient and on the physical properties of the liquid. The principle of the thermal convective loop is illustrated in Fig. 19.26. This method was used by De Van and Sessions to study mass transfer of niobium-based alloys in flowing lithium, and by De Van and Jansen to determine the transport rates of nitrogen and carbon between vanadium alloys and stainless steels in liquid sodium. 

The 5th group metals a summary of their atomic and physical properties Vanadium, niobium and tantalum have only the bcc, W-type, structure no high-temperature or high-pressure polymorphs are known. 

Recently, the kinetics of the ammoxidation of m-xylene (1) and xylene isomers (2) over vanadium catalyst, and of m-xylene over mixed vanadium catalysts (3) were reported. This paper summarizes the results concerning the specific rate constants for each reaction path obtained in the above studies and adds some data on physical properties of each catalyst. 

On the other hand, a catalyst in which the CrV04 was one of major constituents had little catalytic activity for the ammoxidation of xylene. These observations indicate that the nature and the distribution of metal ions and oxygen ion on the catalyst surface affect the catalytic activity and selectivity. It is difficult to predict the relationship between the adsorptivity of reactants and the physical properties of catalyst, but it may be assumed that adding more electronegative metal ions affects the electronic properties of the vanadium ion, which functions as an adsorption center. Further details on the physical properties of catalysts for the ammoxidation of xylenes will be reported later. 

TABLE 1. PHYSICAL PROPERTIES OF SOME INDUSTRIAL AND OTHER SELECTED VANADIUM COMPOUNDS3... 

Bis( )6-arene)vanadium complexes applications, 5, 47 physical properties, 5, 47 reactivity, 5, 46 synthesis, 5, 45... 

Residua and heavy oils contain impurities other than sulfur, nitrogen, and oxygen, and the most troublesome of these impurities are the organometallic compounds of nickel and vanadium. The metal content of a residuum or heavy oil can vary from several parts per million (ppm) to more than 1000 parts per million (Table 6-15), and there does seem to be more than a chance relationship between the metals content of a feedstock and its physical properties (Reynolds, 1997 Speight, 1999). In the hydrodesulfurization of the heavier feedstocks the metals (nickel plus vanadium) are an important factor since large amounts (over 150 ppm) will cause rapid deterioration of the catalyst. The free metals, or the sulfides, deposit on the surface of the catalyst and within the pores of the catalyst, thereby... 

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