Adsorption and diffusion of nitrogen and oxygen in a carbon molecular sieve

✍ Scribed by D.M. Ruthven; N.S. Raghavan; M.M. Hassan

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 588 KB
• Volume: 41
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(86)87105-6

✦ Synopsis

The adsorption and diffusion of Nf and 0, in two samples of carbon molecular sieve (Bergbau-Forschung) have been studied by gravimetric and chromatographic methods. The uptake curves (for N2) show a rapid initial uptake followed by a much slower approach to equilibrium in the long tune region. This behaviour can be accounted for by a dual stage (micropore/macropore) diffusion model. Diffusion of oxygen was too fast to be measured accurately by the gravimetric method although an approximate estimate may be obtained from the initial uptake rate. Over the range of the measurements (O-l atm). the equilibrium isotherms for both Or and Nz are almost linear and there ia very little difference between them. Micropore di&sivities derived from the second moments of the chromotographic response peaks are in reasonable agreement with the values derived from the uptake curves [(&/rf)o, = 3.7 X lo-" s-r; (&/r,f)N % I.2 x 10V4 s-' at 303 K], indicating a kinetic selectivity (Do, /D& of about 30. This is close to the kine& ratio reported by Knoblauch (for a Bergbau-Forsehung sieve) although our values of D&f are considerably larger.