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.

Water, benzene, and nitrogen were adsorbed on Al-MCM-41 molecular sieves, both unmodified and modified via controlled deposition of coke, and adsorption isotherms were determined. The mechanism of adsorption most probably includes multilayer adsorption at lower relative pressures, followed by capillary condensation. It is similar for all the adsorbates studied. The sorption capacity of the parent samples for benzene and nitrogen is relatively high and independent of the Al content. Thus, the Al centers do not substantially influence the lyophilic character of MCM-41 in relation to these adsorbates. In the case of water, however, a decrease in sorption capacity with an increase in the Al amount implies that clusters of the adsorbate molecules formed around the Al centers cause a partial clogging of the pores. The Al content is a factor controlling adsorption of water both directly, as a number of adsorption centers, and indirectly via influencing the content of coke. Coke strongly decreases both the surface area and the sorption capacity of the materials. It also causes a random formation of additional macropores. From the adsorption energy distributions, it is inferred that the carbonaceous deposits create centers capable of bonding the benzene molecules.

Two Illinois No. 6 coal liquids (SOH and ASOH) were separated into polar and non-polar fractions and the polar fractions were analyzed to identify the phenols by RP HPLC in tandem with 31P NMR spectroscopy of samples derivatized with ClPOCMe2CMe2O (1). The results obtained from both methods complement one another quite well despite numerous cases of more than one phenol displaying equal retention times or the same 31P chemical shift when derivatized with 1. The total amount of phenolic oxygen was quantitatively determined by 31P NMR spectroscopy for both coal liquids. The results agree very well with values reported by others by an FTIR method.

Sorption of benzene on nonsubstituted AlPO4-5 occurs on adsorption centers originating from surface heterogeneity and created by structure defects. The metallic heteroatoms present in the framework of substituted AFI-type materials form additional centers able to bind the benzene molecules. This is equal to an increase of heterogeneity in comparison to nonsubstituted AlPO4-5. Sorption capacity of the MeAPO-5 materials depends on both the content of metal and its distribution throughout the crystals. The distribution parameter plays an important role and may even dominate the effect of the number of metallic heterocenters. Some of the equations based on the Polanyi−Dubinin potential theory can be accepted as suitable for characterizing the distribution of the adsorption potential and adsorption energy of the AFI-type molecular sieves. The dependence between the adsorption potential and the metal content may likely be disturbed by inhomogeneous distribution of the heteroatom centers.

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