Unique Lewis and Bronsted acidic sites texture in the selective production of tetrahydropyran and oxepanefrom1,5-pentanediol and 1,6-hexanediol over sustainable red brick clay catalyst.

Activated red brick (ARB) clay material proved superb catalyst for selective conversion of 1,5-pentanediol (1,5-PDO) to tetrahydropyran (THP) and 1,6-hexanediol (1,6-HDO) to oxepane (OP) via dehydration under vapor phase conditions in a continuous flow reactor. As per scanning electron microscopy (SEM), SEM-EDX and X-ray fluorescence (XRF) techniques, ARB clay catalyst majorly possessed silica (quartz), and iron oxide (hematite) species, and synergistic texture contributed to the catalytic efficiency for prolonged time-on-stream (TOS). The combination of active Lewis and Bronsted acidic sites with weak to mild acidic nature in the ARB clay obviously facilitates the dehydration reaction with high selectivity, tetrahydropyran (82%) and oxepane (89%). ARB clay displayed superior catalytic properties in the dehydration of alcohols compared with activities of commercial silica and α-Fe2O3 as catalysts. Commercial silica and α-Fe2O3 catalysts possessing the Lewis acidic sites only did not facilitate synchronous dehydration mechanism.