FERRIERITE NANOCRYSTALS AS SELECTIVE CATALYST IN METHANOL TO DIMETHYL ETHER REATION

Tailoring of physicochemical properties of synthetic zeolites represents an intriguing aspect in the field of zeolite science, in particular when these materials are applied in catalysis. The FER-type zeolite was recently considered as a reliable catalyst for DME synthesis via both one-pot CO2 hydrogenation or methanol dehydration. In this work, the effect of the crystal size on the catalytic behavior of FER-type zeolites during methanol-to-DME is investigated and discussed. For this propose, three FER-type zeolites with different crystal sizes (from 0.1 nm to 10 ?m) were synthesized, characterized in terms of the main physicochemical properties (e.g. crystal morphology, internal/external Brønsted/Lewis acidity, textural properties) and tested in the methanol-to-DME reaction for a wide range of reaction temperature (120-280 °C) in order to investigate the effect of crystal characteristics on methanol conversion, DME selectivity, stability and coke formation. We showed that the decrease in zeolite crystal size from micro- to nano-metric scale offers several benefits in terms of catalytic performances; for instance, an increase of methanol turnover frequency due to reduced intracrystalline mass transfer limitations was observed. Finally the carbon deposition analysis revealed that: (i) carbonaceous consist of polymethyl benzene (PMB) molecules whose composition depends on both the crystal morphology and the reaction time (ii) coke deposition can be reduced and slowed down by using zeolites with smaller crystals (iii) the deposited coke can be removed by combustion at relatively lower temperature for nano-sized crystals.