Catalysis contact

In heterogeneous catalysis, the kinetics we use must account for the fact that the reaction takesplacenotinthegasphasebutonthesurfaceofthesolid.Henceheterogeneouscatalysis is also referred to as contact catalysis in the older literature. In fact reaction takes place in... 

GrenzflSjchen-erscheinung, /. interfacial phenomenon, -katalyse, /, contact catalysis, -spannung, /. interfacial tension. Grenz-gesetz, n. limit law (one which natural phenomena approximate but never actually fulfill), -kohlenwasserstoff, m, any hydrocarbon of the methane series, alkane, paraffin, limit hydrocarbon, -kurve,/, limiting curve, limit curve, -last, /. limit ioad, maximum load, -leistung, /, peak performance, maxi-... 

In 1836 Jons Jakob Berzelius considered eight seemingly unrelated experimental results and concluded that there was a common thread among them. The commonality he defined as catalysis. In doing tliis, Berzelius proposed that a catalytic force was responsible for catalytic action. The concept of catalysis is today considered by most researchers to be due to Berzelius, probably because of the popularity of his annual Handbook of Chemistiywhere he published his definition of catalytic action. For the next one hundred years many referred to the phenomenon as contact catalysis or contact action, as proposed by Mitscherlich. 

Ostwald first came to catalysis through his work on the acceleration of homogeneous reactions by acids. This work was popular at the time although ultimately it would be shown to be incorrect because he believed that the acid, acting as a catalyst, did not enter into the chemical change which it influenced but rather acted by its mere presence (contact catalysis). 

Conformational effects, on reactivity of cycloamyloses, 23 242, 245-249 Constant Ci, values for, 33 273, 274 Contact catalysis, mechanism of, 2 251 Contact catalysts, surface area measurements for studying, 1 65... 

H. S. Taylor, Fourth report of the committee on contact catalysis, J. Phys. Chem. 30, 145-171 (1926). 

About the Mechanism of Contact Catalysis Georg-Maria Schwab... 

Catalysis of a reaction wherein one or more reactants is (are) in one phase and the catalytic process takes place at an interface between the phases. This phenomenon is also termed contact catalysis and surface catalysis. See Homogeneous Catalysis... 

In all above mentioned applications, the surface properties of group IIIA elements based solids are of primary importance in governing the thermodynamics of the adsorption, reaction, and desorption steps, which represent the core of a catalytic process. The method often used to clarify the mechanism of catalytic action is to search for correlations between the catalyst activity and selectivity and some other properties of its surface as, for instance, surface composition and surface acidity and basicity [58-60]. Also, since contact catalysis involves the adsorption of at least one of the reactants as a step of the reaction mechanism, the correlation of quantities related to the reactant chemisorption with the catalytic activity is necessary. The magnitude of the bonds between reactants and catalysts is obviously a relevant parameter. It has been quantitatively confirmed that only a fraction of the surface sites is active during catalysis, the more reactive sites being inhibited by strongly adsorbed species and the less reactive sites not allowing the formation of active species [61]. 

Emmett, P. H., and Teller, E., 12th Report of Comm, on Contact Catalysis 68, New York, 1940. 

One of the most useful applications of this formula is in the calculation of the number of molecules striking unit area of a surface in a given time. This calculation is of importance in connexion with the interaction of a gas with a solid substance, or in problems relating to contact catalysis, where we may require to know how many molecules strike the solid catalyst in each second. Suppose... 

Hydrogen Fluoride Catalysis J. H. Simons Entropy of Adsorption Charles Kemball About the Mechanism of Contact Catalysis... 

The mechanism of contact catalysis may vary in details, depending on the nature of the reactants. Consider the example of hydrogenation of ethene in presence of nickel. In this casse, ethene adds hydrogen in the presence of nickel as a catalyst to yield ethane. 

Schwab and Ketsch4 have developed a theory of the kinetics of contact catalysis based on the assumption that the active patches are located at such interfaces, using the term adlineation for adsorption there but though their assumption seems a very probable one, at any rate for many cases of promoter action, it is scarcely possible to test it by comparison of rates of reaction with a theoretically derived equation there are too many adjustable constants, and other factors. One of these is the rate of surface diffusion to the active linear interfaces, or other active patches, which as many writers have pointed out, may be very considerable.5... 

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