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.

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Recent advances in the oxidation of alcohols to methyl esters using metal nanoparticles have paved the way for more environmentally benign processes, operating at lower reaction temperatures with high product selectivity. Here, we demonstrate the use of bimetallic 1 wt % Au–Pd/TiO2 catalysts that achieve high activity for the oxidation of methanol to methyl formate at low temperature. The application of a water extraction treatment to retain size-stabilized Au–Pd nanoparticles, in contrast to a more standard thermal treatment, provides the most active catalyst for this reaction. Using in situ DRIFTS, we demonstrate that in situ activation during methanol oxidation enhances the catalytic activity at low temperature and that this is a long-lived effect. Surface adsorbates, particularly formate species, build up on the catalyst surface during the reaction and are proven vital to enhancing the catalytic effect.

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.

A new preparative route for vanadium phosphate catalysts is described using supercritical CO2 as an antisolvent. The amorphous microspheroidal VPO produced is shown to be more active than comparable crystalline VPO catalysts for the selective oxidation of n-butane to maleic anhydride and, furthermore, does not require an extensive pre-treatment or activation period to establish full catalytic activity. VPO catalysts prepared using supercritical CO2 as an antisolvent maintain their amorphous nature throughout the catalyst test period. In contrast, amorphous VPO catalysts can also be prepared using liquid CO2 as antisolvent, or by solvent evaporation in vacuo, however, these materials are found to partially crystallise during the oxidation of n-butane. The wholly amorphous catalysts are characterised using transmission electron microscopy, X-ray absorption spectroscopy, 31 P spin echo mapping NMR spectroscopy and X-ray photoelectron spectroscopy. The role of amorphous material in vanadium phosphate catalysis is discussed in detail.