Diffusion in catalyst pellets

✍ Scribed by N. Wakao; J.M. Smith

• Publisher: Elsevier Science
• Year: 1962
• Tongue: English
• Weight: 805 KB
• Volume: 17
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(62)87015-8

✦ Synopsis

A theory is proposed for predicting diffusion rates at constant pressure through bi-disperse porous media. The total rate is the sum of separate contributions for diffusion through macropores, micropores and a series path. To apply the theory requires a knowledge of the pore volume-pore radius distribution for the porous material.

Experimental diffusion measurements are reported for five high-area alumina pellets of different densities made from the same Boehmite powder. The results show that for the least dense pellets macropore diffusion is dominant. In contrast the micropore contribution controls the diffusion rate in the most dense pellet. The theory predicts rates in good agreement with the data over the pressure range investigated, 1-12 atm. Comparison with other diffusion data is hindered by the lack of porevolume-distribution information. However, such data are available for a silver catalyst and for a lowarea alumina. For these different materials the theory also predicts reliable diffusion rates.