Combination of spray drying encapsulation and steaming transformation toward robust hierarchical zeolite microspheres: Synthesis, formation mechanism and acid catalysis

Binder-free zeolite microspheres with hierarchical porosities are prepared by combining spray-drying encapsulation and steaming transformation. Amorphous aluminosilicate microspheres encapsulating tetrapropylammonium hydroxide (TPAOH) are first synthesized by spray drying. Then, they are successfully transformed into robust zeolite microspheres by using a steam-assisted crystallization (SAC) process. The drying temperature plays a decisive role in encapsulation and preservation of TPAOH guiding zeolite crystallization, as well as the morphology and sizes of the obtained zeolites. The morphology, structure and crystallinity of the resulted zeolites can also be controlled by adjusting the water/gel mass ratio and SAC time. The detailed structure and crystallization evolution over the SAC transformation process is studied and discussed. The typical obtained zeolite microspheres possess surface buckled morphologies, uniform large particle sizes, hierarchical porosities, good mechanic strength and intrinsic strong acid sites. They demonstrate enhanced catalytic activity and stability in acid catalytic aldol condensation. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Binder-free zeolite microspheres with hierarchical porosities were prepared by combining spray-drying encapsulation and steaming transformation. The morphology, structure, and crystallinity of the resulted zeolites can be controlled by adjusting the water/gel mass ratio and SAC time. The zeolite microspheres possess surface buckled morphologies, uniform large particle sizes, hierarchical porosities, good mechanic strength, and intrinsic strong acid sites, demonstrating enhanced catalytic activity and stability in acid catalytic aldol condensation.