Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Electronegativity of metal ions

Figure 15 Highest acid strength versus average electronegativity of metal ions of mixed oxides (molar ratio =1)... Figure 15 Highest acid strength versus average electronegativity of metal ions of mixed oxides (molar ratio =1)...
Variation of bond strength with electronegativities of metal ions and ligand donor atoms. [Pg.293]

Xi electronegativity of metal ion, Density bulk density, relative amount of propylene. [Pg.458]

The selectivity increases with decreasing the electronegativity of metal ion added. The highest selectivity is obtained with the Ag-CsOH/Si02 catalyst. [Pg.461]

It is also found that the degradation of HCHO to methanol and CO2 is enhanced, increasing the electronegativity of metal ions corresponding to the metal hydroxides or oxides. This may due to the fact that the dimerization of HCHO expressed by Equation (4) is promoted by acid-base bifunctional action. ... [Pg.178]

Pure silica gel shows a certain activity with a high selectivity, for example, yield of acrolein reaches 78 mol% based on the charged acetaldehyde with a selectivity of 98 mol% at a contact time of 10 s. The activity is markedly enhanced by incorporation of a small amount of an oxide of alkali or alkaline earth metal or ZnO into the silica gel. However, it is difficult to obtain a clear correlation between the electronegativity of metal ions and the activity. On the other hand, pure oxides of alkali and alkaline earth metal that are not supported on silica gel are clearly less active than the supported oxides. [Pg.184]

Figure 1. The range of the highest acid strength, changes with averaged electronegativity of metal ions of binary oxides (on the basis of ref. 1). Figure 1. The range of the highest acid strength, changes with averaged electronegativity of metal ions of binary oxides (on the basis of ref. 1).
Chelation of cellulose ethers with metal ions increased their thermal stability, except for the case of CMC-Cu(II), HEC-Cr(III), and HEC-Cu(ll) complexes. The extent of increasing the thermal stability depends on the type of cellulose ether [anionic or neutral), electronegativity of metal ion, and the nephlauxetic parameter (degree of covalence in the metal-ligand-o bond). [Pg.277]

Fig. 4.2 Trans/1 ratio from isomerization of ru-2-butene over metal sulfates on silica gel plotted against the electronegativity of metal ion. Fig. 4.2 Trans/1 ratio from isomerization of ru-2-butene over metal sulfates on silica gel plotted against the electronegativity of metal ion.
The reaction rate usually increases with the acid strength of catalyst for El and C -like E2 mechanisms, while it increases with the base strength for lcB and C -like E2 mechanisms. Therefore, the catalytic activity often shows an inverse volcano pattern when the activity is plotted as a function of add-base strength of catalyst. Elxamples are shown in Fig. 4.14 where the log of the rate is plotted ag ainst the electronegativity of metal ion which represent the add strength of metal sulfate catalysts. The difference in the positions of minima reflects the relative ease of the breaking of the C —H and C —X bonds. The /3-H of 1,1,2-trichloroethane is more addic, so the minimum is observed at a more strongly acidic catalyst. [Pg.273]

Fig. 4.14 Ratei of elimination reactions of 2-bromobutan (O) and 2,3-dibromobutane (9) over metal-ion exchanged silica gels at 433 K See note for electronegativity of metal ion. )... Fig. 4.14 Ratei of elimination reactions of 2-bromobutan (O) and 2,3-dibromobutane (9) over metal-ion exchanged silica gels at 433 K See note for electronegativity of metal ion. )...
The electronegativity of metal ion, i, was first proposed by Tanaka, Oaaki, and Tamaru (Shokubai, 6, 262 (1964)) the values were calculated by the equation z - (1 +Z) xo — (1), where Z and xo are the oxidation number of metal ion and the electronegativity of metal as element, respectively. Later, Tanaka and Ozaki revised the values by using xi - (1 + 2Z) xo — (2). Since xi from eq. (1) did not fit the data, Misono el al derived an independent equation of xi - xo + (E/n)ii — (3), where / is the n-th ionization potential, in order to explain the catalytic activity and selectivity of metal sulfates for butene isomerization. However, there is fairly good correlation between the revised x-, from eq. (2) and Xi from eq. (3). The electronegativity used here is from eq. (3). ... [Pg.275]

Colloids of more electronegative metals such as cadmium and thallium also act as catalysts for the reduction of water. In the colloidal solution of such a metal, an appreciable concentration of metal ions is present. The transferred electrons are first used to reduce the metal ions, thus bringing the Fermi potential of the colloidal particles to more negative values. After all the metal ions have been reduced, excess electrons are stored as in the case of silver. [Pg.120]

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. [Pg.292]

As described above, the catalytic activity of metal ion-exchanged zeolites for aniline formation has a good correlation with electronegativity and with the formation constant of ammine complexes of metal cations. The order of the activity agrees with the Irving-Williams order. These facts give irrefutable evidence that the transition metal cations are the active centers of the reaction. [Pg.503]

Figure 6.12. A separation of metal ions and metalloid ions [As(III) and Sb(IU)] into three categories class A, borderline, and class B. The class B index is plotted for each ion against the class A index 2 /r. In these expressions, X is the metal-ion electronegativity, r its ionic radius, and Z its formal charge. (Adapted from Nieboer and Richardson, 1980.)... Figure 6.12. A separation of metal ions and metalloid ions [As(III) and Sb(IU)] into three categories class A, borderline, and class B. The class B index is plotted for each ion against the class A index 2 /r. In these expressions, X is the metal-ion electronegativity, r its ionic radius, and Z its formal charge. (Adapted from Nieboer and Richardson, 1980.)...
Recently Parr and Pearson have used the b parameter to investigate the hard and soft properties of metal ions and ligands. They have termed this the absolute hardness in comparison to the Mulliken-Jaff6 a parameter which they call absolute electronegativity. They provide strong arguments for the use of the absolute hardness parameter in treating hard-soft acid-base (HSAB) interactions. [Pg.710]

The above discussion shows that the bonding of metallic ions with O atom is of ionic character and for the bonding of metallic ions(II) with S atom is covalent. Pauling has used electronegativity difference (Ax) as a criterion of ionic character, the ionic character being equal to 50% when Ax = 1.7. The Ax values for the three kinds of bonding are given in Table 5.6. [Pg.149]


See other pages where Electronegativity of metal ions is mentioned: [Pg.185]    [Pg.187]    [Pg.191]    [Pg.43]    [Pg.218]    [Pg.219]    [Pg.323]    [Pg.185]    [Pg.187]    [Pg.191]    [Pg.43]    [Pg.218]    [Pg.219]    [Pg.323]    [Pg.234]    [Pg.8]    [Pg.91]    [Pg.469]    [Pg.721]    [Pg.311]    [Pg.70]    [Pg.407]    [Pg.291]    [Pg.51]    [Pg.100]    [Pg.337]    [Pg.3621]    [Pg.263]    [Pg.592]    [Pg.78]    [Pg.308]    [Pg.312]    [Pg.12]    [Pg.213]    [Pg.146]    [Pg.179]    [Pg.10]    [Pg.76]   
See also in sourсe #XX -- [ Pg.113 ]




SEARCH



Electronegative metals

Electronegativity of metals

Metals, electronegativity

© 2024 chempedia.info