Calorimetry-volumetry

The thermal techniques most commonly used to investigate the acid-base or redox character of soHd surfaces are differential thermal analysis (DTA), thermogravi-metric (TG) and differential thermogravimetric (DTG) methods, differential scanning calorimetry (DSG) and calorimetry. These techniques can be used either by themselves, or in conjunction with other techniques (for instance, TG-DSC, calorimetry-volumetry, DSG-chromatography, etc.) [5, 6]. 

Abstract Basic principles of calorimetry coupled with other techniques are introduced. These methods are used in heterogeneous catalysis for characterization of acidic, basic and red-ox properties of solid eatalysts. Estimation of these features is achieved by monitoring the interaction of various probe molecules with the surface of such materials. Overview of gas phase, as well as liquid phase techniques is given. Special attention is devoted to coupled calorimetry-volumetry method. Furthermore, the influence of different experimental parameters on the results of these techniques is discussed, since it is known that they can significantly influence the evaluation of catalytic properties of investigated materials. 

A number of methods have been used successfully for measuring the kinetics of decomposition for azo compounds Volumetry 43 47), UV-spectrophotometry46), derivative UV-spectrophotometry 35), H-NMR 48) and differential scanning calorimetry (DSC)34). Since DSC can yield perhaps the most information for the least... 

H2 adsorption on high surface area Rh/Ce02 catalysts has been studied by calorimetry [77]. As the reduction progresses, the mean heat of adsorption and the amount of hydrogen adsorbed on the metal, as determined by volumetry and calorimetry, decrease considerably. The initial heats were around 37kJ mol" . 

In the direct calorimetric determination (-id/f rta)r), the amount adsorbed (%) is calculated either from the variations of the gas pressure in a known volume (volumetric determination) or from variations of the mass of the catalyst sample in a static or continuous-flow apparatus (gravimetric determination). In a static adsorption system, the gas is brought into contact with the catalyst sample in successive doses, whereas in a dynamic apparatus the catalyst is swept by a continuous flow. Comparative calorimetric studies of the acidity of zeolites by measuring ammonia adsorption and desorption using static (calorimetry linked to volumetry) and temperature-programmed (DSC linked to TG) methods can be found in the literature [17],... 

The measurements have been performed on uniform powders by adsorption volumetry [6], or calorimetry [1], or on single crystal smfaces by Auger spectroscopy [11], LEED [9,12] and ellipsometry [13],... 

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