NEEDS, STATUS, TECHNIQUES AND PROBLEMS WITH BINARY GAS-ADSORPTION EXPERIMENTS

Microporous adsorbents are gaining ever increasing importance in indus try. ''Almost all applications of adsorption involve mixtures.'' This statement probably appears in the first paragraph of most papers on th e topic. Yet, we cannot reliably predict even the simplest case, binar y gas adsorption, from pure component information. Hence the need for data. Recent improvements in instrumentation made available 'push-butt on' systems for measuring pure component isotherms. Such systems do no t exist for binary measurements which are at least an order of magnitu de more complicated and time consuming. Only a few research groups ope rate custom-made systems to collect binary gas adsorption data utilizi ng different techniques. This paper reviews some of the most commonly used techniques. Thermodynamic relations provide an essential framewor k for the design of experimental techniques, experimental protocols, a nd for the analysis of data. Similar to other experimental methods, th e accuracy of results is proportional to the complexity of measurement s. According to some counts, there are more models of multicomponent a dsorption than accurate data to test them in literature. If the experi ments are not designed and performed carefully, the uncertainties of f inal results mushroom to unacceptable levels especially for variables such as selectivity. A complete error analysis for a typical system is shown. The results with consideration to error analysis show that mos t data available in literature cannot be used to scrutinize between mo dels. Lack of good data also hinders our understanding of the microstr ucture of adsorbents. (C) 1998 Published by Elsevier Science B.V. All rights reserved.