Study of cloverite molecular sieves modified by grafting organometallic complexes inside the pores - II. Adsorption properties of cloverite modified by grafting -SnR3 fragments (R = Me, Et, nBu, Cy)

\The adsorption properties of as-synthesized cloverite and of cloverite mod ified by grafting -SnR3 (R=Me, Et, nBu, Cy) organometallic tin complexes we re studied by a volumetric method. Three hydrocarbons, rt-hexane, benzene a nd iso-octane, were investigated. The adsorption capacities of unmodified c loverite correspond to a filling of the 20 T channel system for benzene and iso-octane, and to a filling of the 8 T and 20 T channel systems for n-hex ane. Grafting -SnCy3 fragments onto the external surface of cloverite has n o effect on the adsorption capacities of the three hydrocarbons but decreas es significantly the diffusion rate of iso-octane, Tn contrast, the adsorpt ion capacities of cloverite modified by -SnR3 fragments grafted inside the crystal (R=Et,nBu: one fragment per window of the supercage; R = Me: 4 frag ments per window) are completely modified: (i) iso-octane is completely exc luded from the pore channels, due to steric constraints; (ii) n-hexane can only fill the 20 T pore channel system, and (iii) the decrease of the pore volume by grafting the organometallic fragment results in a reduction of th e adsorption capacities of n-hexane and benzene. (C) 1999 Elsevier Science B.V. All rights reserved.