Oxygen analyser, paramagnetic

Fig. 6.S8. Dumbell-type paramagnetic oxygen analyser (a) arrangement of dumbell and magnetic poles (b) principle of operation...

Fig. 14-3. Determination of oxygen concentration using its paramagnetic properties (a) principle of the Pauling cell (b) analytical cell of Taylor Servomex OA272 oxygen analyser.

NMR-characterization. 27 Corbin et al. (35) were able to show by a systematic study that Z/A1 MAS NMR gives the true Si/Al ratio with a mean error of 10 %, if two conditions are met a) The amount of paramagnetic species is less than 0.05 % and b) the sample does not contain "NMR-invisible" aluminium. Chemical analyses of the samples under study showed that condition one is fulfilled. If samples contain "NMR-invisible" aluminium a difference between the concentration determined by chemical analysis and the framework aluminium concentration determined by NMR should be observed. From the absence of such a difference we conclude that "NMR-invisible" aluminium species do not exist in our samples. Also a line at the position of about 0 ppm due to octahedrally coordinated non-framework aluminium and a broad line at about 30 ppm due to tetrahedrally coordinated nonframework aluminium (36) could not be observed. The values for the concentration of framework aluminium atoms derived from the intensities of the line at about 60 ppm (see below) are in good agreement with those corresponding to the amount of alumina used in the synthesis mixtures. In conclusion, through the Al MAS NMR measurements it was possible to show that all aluminium atoms are incorporated in tetrahedrally oxygen coordinated framework positions. 

For injection of gas tracer, a similar system was used with oxygen as tracer. The concentration of oxygen in the output gas was monitored with a paramagnetic analyser. The liquid phase (water) was first saturated with oxygen in the tank (2) before introduction into the column. Preliminary analyses of the feed gas and output gas have shown that absorption or desorption of the tracer was negligible up to a pressure of 1.3 MPa. 

Figure 6.132 demonstrates the assembly of such a modular analyser system. The different analysers are based upon infrared absorption (see Figs 6.130 and 6.131), thermal conductivity, ultraviolet absorption (e.g. for C6H6, Cl2, 03, Hg (as a vapour), S02, H2S, N02, and toluene QH5-CH3), paramagnetism of oxygen and electrochemical cell for oxygen. 

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