The fuel ether ethyl tert-butyl ether (ETBE) is produced from ethanol and isobutene in liquid phase. Acid ion-exchange resins are used as catalyst. The chemical reaction on the active sites of the solid catalyst (microkinetics) involves adsorption and desorption processes, thus leading to a Langmuir-Hinshelwood-Hougen-Watson or Eley-Rideal type approach. Based on this assumption, both Fite et al. and Sundmacher et al. derived different approaches and evaluated parameter values for them. Fite et al. received their parameters from their own measurements, so the parameters fit the experimental results well. Sundmacher et al. fitted parameters based on experiments of Francoisse and Thyrion. These constants cause a much worse fit to the measurements of Fite et al., however, the approach of Sundmacher er nl. predicts the results as well if its parameters are newly fitted to the data of Fite et al. and our own. If both approaches are applied to the investigations of Francoisse and Thyrion, the predictions are almost equal but differ from the experiment by a factor of two.