A DFT-study on the acidity of Mo–O–Al-clusters

Supported molybdenum oxide on e.g. alumina is a useful catalyst for metathesis of olefins. However, the presence of acid sites will influence the selectivity of the metathesis reaction, since they may catalyze double bond isomerisation of olefins. The acidity of supported molybdenum oxide on alumina was modelled using neutral clusters. DFT calculations showed that the strength of acidity of the sites decreases and the activation energy for double bond isomerisation increases with a decrease in the formal oxidation state of the molybdenum oxide.

The acidity of Mo–O–Al clusters can be determined using the deprotonation energy and it increases with increasing formal oxidation state of molybdenum in the cluster. The acidity is related to the activation energy for double bond isomerisation of olefins. Figure optionsDownload as PowerPoint slide