From Bodenstein to Péclet – Dimensionless Numbers for Axial Dispersion in Chemical Reactors

In the present contribution, the historical development of dimensionless numbers describing axial mixing effects in chemical reactors is analyzed. While the Bodenstein number has become established in Europe, the American literature often uses the Péclet number for this purpose. A journey through the historical reaction engineering literature shows that the development was complex and that Langmuir's decisive role in particular has hardly been acknowledged to date. Unfortunately, despite decades of using dimensionless numbers for mass and heat transport in chemical reactors, no consensus has yet been reached on a uniformly accepted nomenclature. To remedy this shortcoming, a proposal for consistently defined numbers at the molecular and the reactor level is made.