Pulse Catalytic Isopropanol Dehydration to Propylene Over Natural Acidic Clays: Comparison With Zeolite and Amorphous Silica‐Alumina

ABSTRACT The potential of saponite clays, hydrous magnesium silicates with low content of aluminium, is investigated in the selective isopropanol catalytic dehydration to propylene. Their performances are compared with the activity of montmorillonite clays, low‐alumina zeolite and amorphous silica–aluminas. All solids were characterized by XRD, N 2 sorption isotherms, TGA‐IR, NH 3 adsorption FTIR, NH 3 /SO 2 adsorption microcalorimetry, and solid‐state 1 H and 2 7 Al NMR. The physico‐chemical analyses show that the samples are predominantly mesoporous, except zeolite, with BET surface areas ranging from 130 to 430 m 2 /g. All catalysts display acidic character and are thermally stable below 300°C. Their catalytic performances were evaluated by using a pulse catalytic reactor set inside a calorimeter (DSC‐GC). This technique offers a convenient way to screen industrially relevant temperature regimes that balance activity, selectivity and process economy of different type of solids. Catalytic testing revealed that below 150°C, clays outperformed amorphous silica‐aluminas, whereas the zeolite, although giving high conversion, is not suitable for the application due to a low selectivity to propylene (10%). An optimized activation temperature is the key parameter allowing clays to preserve structural stability, moderate surface area with favorable pore structure and to maintain a suitable number of acid sites.