Desilicated MFI type zeolite: catalytic performances assessment in Methanol to DME dehydration

The modification of the physicochemical properties of synthetic zeolites is an important element when these materials are applied as heterogeneous catalysts in the view of more sustainable and effective processes. In this work, desilicated ZSM5 samples were tested on the methanol to dimethyl ether dehydration. Desilication time strongly affects the textural and acidic properties of the samples, and those characteristics determined a different catalytic behaviour. Contact time of 60 min with NaOH solution (alkaline desilication) favourably impact on the activity of the catalysts and its stability against deactivation in terms of methanol conversion and yield to DME, in comparison with parent zeolite and sample prepared after 30 min of desilication. This effect is due to a combination of changes in the properties of acidic sites and mesoporous volume, as confirmed by stability test over 80 h of reaction. The analysis of formed coke confirmed this evidence since the most performing catalyst showed the lowest tendency to form coke as the main consequence of the improved accessibility to the acid sites determined by the induced mesoporosity.