Measurement of monobranched alkane mobility in the silicalite framework in the presence of dibranched and linear molecules

This paper presents an experimental method for evaluating the apparent diffusivity of monobranched alkane isomers in mixtures with different molecules, based on the classical inverse chromatography technique and on moments theory. This method, which does not necessitate any complicated model or parameter estimation procedure, has been applied to the study of C6 and C7 alkanes diffusion in silicalite at 185 degrees C in the liquid phase. Experimental results show that the presence of dibranched molecules in the silicalite network reduces greatly the apparent diffusivity of monobranched isomers, questioning the possibility of separation. However, further adding a fast-diffusing species such as n-heptane in the adsorbent network can compensate for this effect. Although the new method proposed in this paper only gives access to an apparent diffusion coefficient (and not to the self-diffusion coefficient), it is a useful tool for a rapid evaluation of a given adsorbent diffusion selectivity.