As the pellets are extrudates we co

As the pellets are extrudates we could not vary the pellet radius because is constant in all of them. In order to confirm the micropore control, experiments with almost the same mass of adsorbent but with cylinders of different length (2.3 310 m) and the same radius (R 51.1310 m) were performed. A reasonable assumption to analyze the data is to perform all the calculations assuming the shape of the adsorbent as spheres. In these ‘small extrudates’ a sphere of equivalent volume can describe the geometry to perform the calculations. If the control step is in the macropores, some differences in the slope will be observed (in fact to keep the same pore diffusivity, as the roots of Eq. (3) are different, a different value of apparent diffusivity should be obtained). If is the controlling step, no difference should be observed in diffusion in micropores the curves (within the accuracy of the measurements). Desorption curves obtained with these ‘small extrudates’ are shown in Fig. 13. The flow-rate used was also 6.2– 6.8310 m /s, a flow-rate where no film mass transfer was observed in the larger extrudates. The slope of the desorption curves is similar indicating that no variation occurs when we change the external geometry of the pellet, confirming the micropore control of the propylene diffusion in this CMS sample.