LAUSR

Abstract To investigate the load-dependent heat of adsorption a sensor gas calorimeter was developed which allows the simultaneous measurement of adsorption capacity and heat of adsorption in porous materials. A commercially available volumetric measurement device was extended by a newly developed calorimetric measuring cell. Using this apparatus, the load-dependent heat of adsorption of alkanes and alkenes on the zeolites 13X-APG and HiSiv 3000 as well as on the activated carbon Norit R1 Extra was investigated. On all three adsorbents the heat of adsorption increases with chain length of the hydrocarbons. On HiSiv 3000 and Norit R1 Extra both load and heat of adsorption for all investigated alkanes and alkenes of the same chain length are very similar due to similar interactions with the adsorbent surface. Presumably dispersion interactions dominate adsorption in these systems. Contrary to these findings on 13X-APG higher loads and enthalpies of adsorption for alkenes than for alkanes occur. These higher heats of adsorption can be attributed to the energetically more attractive quadrupole-cation interactions between the double bond of alkenes and the cations of the zeolite.