Membrane chromatography velocity

Mass-related reaction rates, tm, were determined at normal pressure for the following ranges of operating conditions T = 473 to 503 K, xc6h12 = 2-6 vol%, normal pressure conditions at both membrane sides, gas hourly space velocity (GHSV) 400-1000 h-1. The composition of the effluent was measured under steady-state conditions using gas chromatography (GC). 

Kinetic separations, in which components are separated on the basis of different diffusive or convective velocities (Fig. 4) can lead to much higher resolutions in a single stage. These are shown as differently sized arrows in Fig. 4 to illustrate respectively membrane based and chromatographic separations. Unfortunately, many membrane separations are not yet sufficiently selective to discriminate between very similar molecules, such as protein mixtures. Although fixed bed chromatography is well suited to separate mixtures of similar components, often substantial flows are required to obtain sufficiently different convective velocities which leads to a substantial eluent consumption. 

Fig. 4. Kinetic separations on the basis of differences in convective (chromatography) or diffusive (membranes) velocities...

The static cell used for reverse osmosis and ultrafiliration experiments can be used to test the separation of gas mixtures Air in the feed chamber of the test cell and the feed gas line is removed by flushing them with the feed gas stream. The feed gas is then supplied to the feed gas chamber under pressure. The gas permeation velocity is measured by a bubble flow meter connected to the permeate side of the test cell. The permeate sample is also subjected to analysis by gas chromatography. This simple device is useful when an asymmetric membrane is tested and when the permeation rate is high. 

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