Recent History of Kinetic Studies

In today s competitive climate, investigators cannot spend much time on the clarification of the kinetics for a new process. At Union Carbide Corporation in the 1970s the study to replace the old and not very efficient butyraldehyde hydrogenation was done in three months. In another three months a kinetic model was developed and simultaneously tested in an existing single tube in a pilot-plant (Cropley et al,1984). Seldom is a completely new process studied for which no similar example exists in the industry. 

The first reactor plugged up irreversibly in the first minutes of operation. A second reactor was made and production started. The polyethylene was dark and stinking but the Navy needed the material. As the war ended, the product was improved when competition started, quality accelerated significantly. Fourteen year after production started, the first pilot-plant was built, since the continuous process was difficult to study in small scale. A few more years later, three polyethylene pilot-plants were running day 

Humans can not know the ultimate and detailed true reaction mechanism of any reaaJon, or the kinetics that can be derived from it.. Bodenstein (1906) studied the mechanism of the H2 + Br2 = 2 HBr reaction and after several decades of work and dozens of publications wrote the final paper on the subject. Within a few years one of his students published a correction to Bodenstein s explanations. 

The present author was worried about the lack of knowledge concerning the quality of the kinetic models used in the industry. A model is by definition a small, scaled-down imitation of the real thing. (Men should remember tliis when their mothers-in-law call them model husbands.) In the industry all we require from a kinetic model is that it describe the chemical rate adequately by using traditional mathematical forms (Airhenius law, power law expressions and combinations of these) within the limits of its applications. Neither should it rudely violate the known laws of science. 

No industrial process enjoys a knowledge of mechanism and kinetics so complete that models can be compared to it. Aris (1975) and Cropley (1978) simulated experimental results using a rate model. From the data a new model was derived and compared with the original. 

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