Catalysis

Excerpts of Marika Blondel-Mégrelis text in “Catalysis in France: an Adventure” published by SFC at the 13th International Congress on Catalysis, Paris, July 2004.

First definitions

When he coined the term catalysis in 1835, Berzélius took a certain number of surprising but disparate, extremely diverse and differently described observations, and reunited them to identify a true scientific phenomenon. In the 19th century alone, these phenomena were described by such researchers as Kirchhoff, Davy, Döbereiner and Thénard. It was Berzélius, however, who took these phenomena and gathered them into one family with the following common characteristic: “Combinations are destroyed, new combinations are made, and all this is done without any alteration to the body producing these changes” [1]. In other terms, these bodies remain neutral in what he recognized as a process of chemical decomposition.

At the same time, however, he set these phenomena apart. These bodies, whether single or compounds, soluble or insoluble, which bear such an influence, act under the effect of a force other than chemical affinity. Hence the separate name: analysis is the decomposition of bodies via chemical affinity, whereas decomposition through the action of this newly recognized force would be referred to as catalysis. “This decomposition occurs through the sole presence of a foreign body, due to a force that as yet remains unknown, without the slightest part of this body entering into the new combination.” [2].

We can therefore say that even if the phenomenon had not been satisfactorily explained in even a sketchy way, between 1835 and 1840, it had at least been characterized and taken into account. It would be more than a century later that Marcel Prettre’s definition of a catalyst would introduce the notion of yield, an essential piece of data for the catalytic operations which would drastically change the chemical industry starting in 1900. “The catalyst is a substance that increases the rate of a chemical transformation without modifying the yield, and that is found intact among the final products of the reaction.” [3]