For an industrial reaction engineer, trouble shooting catalytic reaction systems that have “suddenly” begun to perform poorly is a common occurrence. The initial request is typically framed as a need to “fix” the catalyst, but further investigation often results in a more nuanced narrative.
In this paper, a study of the sudden deterioration in performance of a chlorocarbon hydrolysis reactor is presented. What was originally thought to be a catalyst issue was eventually found to be the result of changes in a ppm-level impurity in the feed material that had not been recognized as important. In order to satisfactorily diagnose the problems and prescribe solutions, a dynamic reactor model that included the effects of reversible poisoning by a minor impurity was required. As the study evolved, the reasons for 20 years of puzzling phenomena observed in this plant became apparent, including moving hot spots, partial catalyst reactivation by steaming and the recent emergence of exaggerated hot spots. The talk concludes with a brief outline of reactor designs that would make the process much more robust to variable poison levels with no changes to the catalyst.