Balandin number

The number of active centres is therefore generally less than the total number of surface atoms,the ratio of the two being termed the Taylor fraction Fj (or Taylor ratio). A.A. Balandin attempted to make Taylor s ideas more precise by proposing a Multiplet Hypothesis by which each type of reaction required a multiplet of several atoms to be an active centre. So for example to chemisorb a benzene molecule either for its hydrogenation or in its formation by dehydrogenation, a hexagonal multiplet with one central atom as found in the fcc(l 11) plane would be needed. If the number of atoms composing the multiplet (or ensemble as it was called by Kobozev ) is the Balandin number Nb, then... 

Here the role of the geometrical factors in chemisorption is especially vividly expressed. These factors have been analyzed in detail by A. A. Balandin and co-workers in their papers (see, for example, ref. 18) on the multiplet theory of catalysis, in which they show their prime importance in a number of cases of the catalytic process. The electronic mechanism of chemisorption does not at all exclude these factors, but just stresses their role it retains the geometrical schemes of the multiplet theory but gives them physical content. 

Paraffins with more than eight carbon atoms can dehydrocyclize to form bicyclic products. According to Shuikin and Bekauri, bicyclic products can be formed from paraffins by either successive dehydrocyclization or by simultaneous closure of several carbon-carbon bonds (35). The second possibility follows Balandin s sextet model (56). A large number of hydrocarbons follow the consecutive mechanism (27). Thus far there is no evidence for simultaneous closure. 

This method was applied in our laboratory to a number of oxides (82), in particular to Zr02 in the work of Balandin et al. (83). In the investigations of the author and Tolstopyatova (84, 85, 86) the effect of the method of preparation of Cr203 on the bond energy with the catalyst was deter-... 

Numerous investigations on the ultrasonic treatment of molten ferrous and nonferrous metals and alloys were carried out in the 1960s. We should mention the works by Teumin and Abramov [6,8] on the basics of the ultrasonic treatment of a melt during solidification of ferrous metals and alloys, as well as the investigations by Balandin [9] on solidification of aluminum alloys. Further studies by Rostoker and Richards [10] and Seemann [11], and by a number of other scientists were devoted to the effect of UST on structure formation in nonferrous alloys. 

A description of the present state of this theory will be presented in the following discussion [cf. Balandin 8-11)]. The multiplet theory deals with numerical values of bond lengths and bond energies, as well as with the geometrical form of reacting molecules and the crystal lattices of catalysts. This allows fairly definite results to be obtained for many reactions on an atomic level. It is this point that singles out the multiplet theory from a number of other theories on catalysis. 

Therefore, the data briefly published in Balandin 67) are also discussed in the present paper but now recent quantitative data are given and the number of such data is much larger. 

Recently there have appeared papers by other authors in which volcano-shaped curves have been obtained. Fahrenfort, van Reijen, and Sachtler (467) have carried out complex kinetic, IR spectroscopic, calorimetric, and mass spectrometric investigations on the decomposition of formic acid on various metals. The authors come to the conclusion that the reaction proceeds via the intermediate formation of an adsorption complex of the surface nickel formate type. By comparing the heat of formation of the formate of the corresponding metal with the temperature Tr at which a fixed depth of conversion r (log r = —0.8) is reached, the authors have obtained a broken line similar to the Balandin volcano-shaped curves (Fig. 63). The catalyst half-covered with the adsorption complex is the most active one. The reaction investigated by the authors differs from those investigated by us. It is characteristic, however, that in the case of oxides the selectivity is the same with respect to the decomposition of alcohols and of formic acid [Fig. 1 in Mars (468)). In their report at the Paris Congress on Catalysis Sachtler and Fahrenfort (469) give additional data on volcano-shaped curves for a number of reactions and point out that this relationship between the catalytic activity and the stability of the intermediate complex has been qualitatively predicted by Balandin. ... 

Colloid catalysts with chiral stabilizing agents can be used as asymmetric catalysts in the reactions of prochiral compounds. One such catalyst is the well-known "Skita-catalyst"(colloidal Pt or Pd with gum-arabicum as an optical active polysaccharide as a protective colloid). These catalysts have been used very often in a number of hydrogenations of unsaturated compounds, including prochiral molecules, but never were their asymmetrizing action noted. Nevertheless, including chiral components as protective colloids in such catalysts allowed for the discovery of asymmetric effects in their action. Indeed, Balandin, Klabimovskii et al. found small... 

Only a few years after the existence of active centers was first postulated, Dohse and coworkers in 1930 ( ) determined the site density by what amounts to determining the number of chemisorbed reactant molecules when the reaction is zero order. For isopropanol dehydration over alumina they found a site density— asji min their alumina had a normal surface area—of about 10 cm. In 1937 Kubokawa ( ) used a poisoning method, measuring the amount of mercuric ion which inhibited > 2 decomposition over platinum black. Balandin and Vasser i rg obtained in 1946 ( ) a site density of the order of 10 cm for the dehydration of isopropanol over a mixed oxide of zinc and alumina. 

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