Zeolite A compacts were directly prepared from allophane compacts by hydrothermal reaction with NaOH solution. With increasing concentration of NaOH solution formation rate of zeolite A from allophane increased and crystal size of formed zeolite A decreased. Higher reaction temperature resulted in increases in formation rate and crystal size of zeolite A. Spaces are formed by the aggregated zeolite A crystals and are the macro pore which shows narrow size distribution. The macro pore size increased linearly with an increase in the crystal size of zeolite A.
