Abstract
A new methodology for the assessment of the performance loss in catalytic reactors due to deactivation was developed and applied to fixed- and fluidized-bed CO methanation, with catalyst subject to coking. The methodology is based on the solution of heat and mass balances, by decoupling the reactor and deactivation dynamics. This is possible by using consecutive 1D, steady-state calculations for the characterization of the reactor performance. In this way, the progressively lower values of catalyst activity along the time on stream are computed with the integration of a dedicated dynamic model. This method has shown promising results in the characterization of the loss of performance of the reactor over time. The model correctly describes a progressive deactivation of the catalyst in fixed-bed reactors, while it shows that the decrease in activity is sudden for the whole reactor volume in fluidized bed reactors and occurs after a critical time-on-stream. Besides, it was observed that the fluidized bed reactor is in general more resistant to deactivation by CO, with the time needed to reach 25% conversion being 1.5 to 2 orders of magnitude higher than for a fixed bed in similar conditions – for example around 250 hours against 50 for a fixed bed at 300°C. This will allow optimizing the reactor with respect to deactivation, hinting the modifications possible in the conditions or in the reactor geometry to maximise the time-on-stream prior to loss in the product quality.