A comprehensive study on crystallization of silica powder and self-bonded silica pellets by solid-state transformation has been made. In particular, crystallization of MFI zeolite precursors under steaming (vapor phase) and boiling (liquid) mode during the transformation process have been examined. It is found that, while hierarchical MFI zeolites containing micro- and mesoporosites may readily be obtained via these synthesis routes, the crystallinity, morphology and mesoporosity of the zeolite products depend not only on the form of silica source (powder vs. pallet), but also on the crystallization phase (liquid vs. vapor phase) invoked during the transformation process. Among them, mesoporous MFI zeolites prepared from self-bonded silica pellets by vapor phase steam-assisted crystallization method show the desirable textural and adsorptive properties rendering for specified applications of zeolites with hierarchical pore structures. (C) 2012 Elsevier B.V. All rights reserved.