Porosimetry

Porosimetry is an important technique in the analysis of solids. It gives information about the surface area and porosity of solids and thus about the structure of the porous material and its surface architecture. It has a wide range of applications including catalysts, adhesives, ceramics, clays, fibers, films, fertilizers, filters, fillers, food additives, pharmaceuticals, pigments, polishes, polymers, resins, soils and sediments. The Green Chemistry lab uses this technique routinely to characterise the surface properties of a variety of materials and catalysts prepared in the lab. It is also applied for the study of structural changes brought about by physical and chemical modifications and also for the determination of surface acidity of catalyst materials.

The gas adsorption technique is performed by the addition of a known volume of adsorbate, typically nitrogen, to the solid material. At cryogenic temperatures, weak molecular attractive forces will cause the gas molecules to adsorb onto thje solid material. The adsorbate is added to the sample in a series of controlled doses, the pressure in the sample vessel is measured after each dosing. By measuring the reduced pressure due to adsorption, the ideal gas law can then be used to determine the volume of gas adsorbed by the sample. The resulting relationship of volume of gas adsorbed vs. relative pressure at constant temperature is known as an adsorption Isotherm. From the analysis, and the cross-sectional area of the adsorbate gas molecule, the surface area and pore size distribution of the sample can be derived.

The Green Chemistry Lab is equipped with a Micromeritics ASAP2010