A simple method of calculating mass transfer factors for heterogeneous catalytic gas reactions

✍ Scribed by D.M. Ruthven

• Publisher: Elsevier Science
• Year: 1968
• Tongue: English
• Weight: 479 KB
• Volume: 23
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(68)85010-9

✦ Synopsis

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effect of external mass transfer on the overall rate of heterogeneous catalytic reactions is briefly discussed and general equations are developed which make it possible to calculate mass transfer ,factors directly from kinetic data, for any system in which diffusion within the catalyst pores occurs by a molecular mechanism. The application of these equations is illustrated by considering published kinetic data for the water gas shift reaction. It is shown that if the ratio of superficial gas velocity to catalyst pellet diameter is greater than about 24 set-* (at 400°C) resistance to mass transfer is small. This condition is generally met in industrial shift converters and mass transfer restriction therefore becomes significant only at high temperatures. In laboratory reactors lower gas velocities are often used and mass transfer resistance may be quite large. In order to avoid this type of error when measuring design rate constants it is essential to use the same size of catalyst pellet and the same gas velocity in the laboratory as are to be used in the full scale converter.