Experimental measurements of heats of adsorption published in the literature are often in disagreement: differences of 10-20% are common.
The three most widely used experimental methods are:
(1) differentiation of adsorption isotherms at constant loading;
(2) measurement of adsorption isosteres;
(3) calorimetry. Results from these methods were compared for the
system nitrogen on CaA, oxygen on CaA, and carbon dioxide on NaX.
Although the same materials and similar degassing procedures were used
for all experiments, calorimetric heats are about 2 kJ/mol higher
than the heats from isosteric measurements. Additional experiments
are needed to bring these methods into exact agreement.
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