FTIR spectroscopy is used for the investigation of hydrogen bonding of the Bronsted hydroxyls in H-ZSM-5 zeolite with a number of weak bases (Ar, H2,02, N2, CH4, C2H6, CsHs, CO, C2H4). The following correlation for the increase in intensity of the hydroxyl band, due to its shift resulting from perturbation, is observed: M I A 0 = 0.018Auo~. Applying this correlation to the HF-LF pair in the infrared spectra of H-Y, H-EMT, and H-EM0 zeolites, it is shown that the distribution of Bronsted hydroxyls between super and @cages is approximately 1: 1 whereas in SAPO-37 samples this ratio is close to 3: 1. This is in agreement with results for the deconvolution of the hydroxyl region of the lH MAS N M R spectra. The estimated values of the extinction coefficients for the HF and LF band in H-Y zeolite (Si/Al = 2.7) are 3.2 and 8.5 cmpmol-l, respectively.

Catalysts comprising zeolite ZSM-5 impregnated with precious metals including Ag, Cu, Ni, Pd, Ir and Ru, have been tested for the methanol to hydrocarbons reaction in a continuous flow fixed bed reactor. Comparison with the activity of unmodified ZSM-5 showed that Ag, Cu and Ni enhanced the selectivity to C 6 -C 11 aromatic products by a factor of two or higher. Moreover, Ag/ ZSM-5 showed improved selectivity for the C 6 -C 7 fraction of aromatic products. Ni/ZSM-5 was found to be selective to naphthalene, while Cu/ZSM-5 was selective for C 9 -C 11 aromatic products. It was ascertained that all the impregnated metals were present as metal oxides in the starting materials. It is therefore proposed that the enhanced selectivity to aromatic products is due to the interaction of the acid sites of the zeolite with the basic sites of the metal oxide at the edge of the zeolite crystals, as well as the possible coordination of propene molecules formed during the reaction, that are likely to be the building blocks for the formation of aromatics.

Composites of Ga 2 O 3 clusters and zeolite ZSM-5 were evaluated for the transformation of methanol to hydrocarbons. Comparison of the activity with ZSM-5 showed that the Ga 2 O 3 clusters are responsible for the enhanced selectivity to aromatics via contact synergy, thus showing the importance of non framework gallium species for this reaction. TEM analysis of fresh and spent catalysts allowed the identification of the formation of carbonaceous products at the Ga 2 O 3 /zeolite interface region, and this interface is also the probable location of the catalyst active sites.

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The influence of niobium on the physicochemical properties of the Mo-V-O system and on its catalytic properties in the oxidation of ethane to ethylene and acetic acid is examined. Solids based on