ABSTRACT
Comparative studies of the adsorption of benzene (B), toluene (T), pyridine (P), and 3-methyl pyridine (MP) on polycrystalline V205 samples at 250 and 350°C [132] revealed that benzene is practically not adsorbed as compared to other hydrocarbons (Table 8.5). This indicates that iT electrons of the aromatic ring do not participate in the adsorption bond and the other aromatic molecules are adsorbed end-on through their functional groups. The amount of toluene adsorbed does not change on raising the temperature, which indicates that it must be strongly held at the surface at variance with pyridine which is only weakly adsorbed. The sum of the amounts of toluene and pyridine adsorbed was equal to the amount of adsorbed 3-methyl pyridine, which was taken as an indication that toluene and pyridine are adsorbed on different crystal planes. It may be assumed that pyridine will be adsorbed on the highly polar non-(010) planes either on Bronsted or Lewis acid sites; toluene and-by analogy-2-xylene must be thus adsorbed on the basal (010) plane through the donor-acceptor interactions.
