Preparation of porous ZnAl2O4 spinel monoliths through sol-gel route accompanished with phase separation

Abstract:

zinc chlorideand aluminum chloride (AlCl₃.6H₂O, Aladdin, 97%) were chosen as zinc and aluminum precursors, a mixture of distilled water (H₂O) and ethanol was used as the solvents. Propyleneoxide was used to immediate the gelation process, and poly(ethylene-oxide) was used as a phase-separation inducer. All the chemical reagents were used as received. Porous ZnAl₂O₄ spinel monolith has been successfully prepared via the sol–gel route accompanied by phase separation. The as-prepared samples were characterized by means of XRD, DTA, SEM and FTIR, the inpact of heat-treatment on the structure and phase transmition were discussed. The results show that phase separation can be induced by PEO, thus obtain a prous monoliths with a interesting pore structure with co-continuous solid skeletons and well-controlled pores. The as-prepared samples shows a phase of(ZnAl-LDHs, The ZnAl₂O₄ crystalline phase is obtained after the decomposition of –OH and carbonate anions during the heat treatment at 600 _oC in air. The materials can be widely applied in many catalytic fileds in the future.