Densimetric-volumetric method

Abstract Combined volumetric and gravimetric measurements allow one to determine the coadsorption equilibria of binary gas mixtures without sorptive gas analysis, i. e. without using a gas chromatograph or mass spectrometer. The experimental setup, a basic theory and several examples of this method are presented. Two modifications of it, namely densimetric - gravimetric and densimetric - volumetric measurements are outlined. These especially are suited to do quick but still accurate measurements of binary coadsorption equilibria for industrial process control and / or design. These methods also can be used to measure adsorption of gases and vapors on walls of vessels, tubes or surfaces of any other solid materials. List of symbols. References. 

In this chapter we will present experimental information (Sect. 2.1), the theory of measurement (Sect 2.2), and uncertainties (Sect 2.3), and several examples (Sect. 2.4) of this method. Two modified versions of the measurement procedure which may be called densimetric-gravimetric and densimetric-volumetric / manometric methods (which especially seems to be suited for online industrial coadsorption measurements) are also outlined (Sect. 3). These methods also may be used to measure adsorption of gases and / or vapors on surfaces of arbitrary sohd materials as for example the inner walls of vessels, tubes, valves etc. of the experimental device(s) used (Sect.3.6). Advantages and disadvantages of the methods proposed are discussed in Sect. 4. A list of symbols used is given in Sect. 5, followed by references to journal articles and books cited. 

Densimetric-volumetric measurements have been performed recently at our Institute determining again coadsorption equilibria of (CO2, CH4) on AC D47/3 at T = 293 K for pressures up to 1.4 MPa, cp. Sect. 3.4. Results are identical within experimental uncertainties with those received by densimetric-gravimetric measurements. Sect. 3.4. Hence discussion of this method can be postponed to Sect. 4 where all experimental methods outlined in this chapter will be evaluated from both the experimental and the theoretical point of view. 

In this article a short overview is given of the measurement methods for adsorption equilibria of pure and mixed gases most often used today. After presenting the traditional volumetric and gravimenic method, modem combinations of it, namely the densimetric-volumetric and the densimetric-gravimetric method to measure binary coadsorption equilibria are presented in brief (Section 2). 

Figure 4.20. Schematic diagram ofan instrument to measure wall adsorption by using the volumetric - densimetric method.

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