Carbonaceous compounds deposited on aluminosilicate mesoporous molecular sieves of the MCM-41 type during conversion of cyclohexene at various temperatures were investigated using TGA; DRIFT, UV-vis, and 13 C solid state NMR spectroscopies; and a sorption technique. The chemical composition of the deposits is not significantly affected by the Al content of Al-MCM-41 and depends mainly on the temperature and the duration of the reaction. At lower applied temperatures, both aliphatic and aromatic compounds are formed; they are relatively weakly bound to the surface of the material. After a longer reaction period, some deposits appear that are strongly bound to the surface. At higher temperatures, a fraction of the coke migrates out of the pores. Then, part of the coke (most likely aliphatics) desorbs and moves away, while the other part (presumably aromatics) adsorbs on the external surface of the sieve. The coke remaining both in the pores and on the external surface mostly forms multilayered polyaromatic structures that are strongly bound to the surface of the material. The water sorption capacity of the studied materials decreases with the content of the deposits.

Aluminosilicate MCM-41 samples in the as-prepared form and modiÐed by deposition of carbonaceous compounds formed during conversion of cyclohexene were investigated by nitrogen adsorption. The amount of the deposits decreases with the reaction temperature and increases with the quantity of aluminium incorporated into the materials. The formation of coke occurs primarily in the aluminium-rich pores. The modiÐcation leads to a lowering of adsorption capacity, surface area, pore volume and relative pressure corresponding to the adsorption isotherm step that reÑects the capillary condensation. The nitrogen adsorption measurements appeared to be a useful tool for characterisation of structural and surface properties of both the original and the novel surface-modiÐed porous materials.

Additional component(s) introduced into the reaction gel allow for a stable framework substitution of Cr in significant amounts. Appropriate component(s) and metal compounds, especially those of Al, are primary factors determining the substitution. The products of the system {triethylamine−acetate ions−Cr³⁺ ions} have been characterized in more detail and compared with those from other synthesis procedures. The Cr heteroatoms are 4-fold bonded to the framework and their coordination is complemented by two ligands from the pores (water molecules in the calcined form) to give the favored octahedral-like coordination. The coordination can be changed reproducibly from 6 to 4 by heating the crystals over 550 K (dehydration) and vice versa by cooling (hydration). The framework Cr(III) cannot be oxidized and causes no framework charge. The reaction conditions, differing from those in the classical syntheses, enable the control of the crystal morphology. The crystals can be grown as flat hexagonal pellets of a perfect morphology with high crystallinity and sorption properties