Imaging individual catalyst pellets

These experiments have revealed the possibility of the ignition of individual catalyst pellets within the bed. Such pellets can stay dry after the ignition due to the efficient progress of reaction despite the fact that they are surrounded by liquid filled pellets [Figure 5.4.4(a)], The images also reveal the presence of the beads with the characteristic concentric pattern of liquid distribution, similar to that observed earlier (Figure 5.4.2) for individual cylindrical pellets. 

Clearly by working with typical spatial resolutions of approximately 30-50 pm, individual pores within the material are not resolved. However, a wealth of information can be obtained even at this lower resolution (53,54,55). Typical data are shown in Fig. 20, which includes images or maps of spin density, nuclear spin-lattice relaxation time (Ti), and self-diffusivity of water within a porous catalyst support pellet. In-plane spatial resolution is 45 pm x 45 pm, and the image slice thickness is 0.3 mm. The spin-density map is a quantitative measure of the amount of water present within the porous pellet (i.e., it is a spatially resolved map of void volume). Estimates of overall pellet void volume obtained from the MR data agree to within 5% with those obtained by gravimetric analysis. 

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