Abstract: The trimodal porous structured hierarchical FAU/alumina composite (macro-pores/meso-pores/micro-pores) were hydrothermally synthesized using macro-mesoporous alumina monoliths as substrates by seeding and secondary growth method. The influences of supports with different physicochemical features and the seed gel assistant on the properties of the resultant composites were studied. The zeolite seed and composites were characterized by XRD, SEM, nitrogen adsorption-desorption isotherms and DTA/TG. The results show that the coverage of zeolite on monoliths was determined by both of the physicochemical features of the substrates and the chemical compositions of the seed suspension or secondary crystallization solution. After being seeded, the substrate of γ-Al2O3 was partially transformed into zeolite structure with the retainment of the original substrate morphology. The zeolite coverage on α-Al2O3 support is improved significantly by the assistant of seed gel.

Key words: hierarchically porous structure, NaY seed, secondary growth method, FAU/ Al2O3 composites, alumina type, seed gel assistant