Formation, trapping and kinetics of H atoms in wet zeolites and mesoporoussilica

Pulse radiolysis and time-resolved EPR were used to study mobile H atoms in wet porous solids, including zeolites and mesoporous molecular sieves. The time-resolved study was accompanied by measurements of trapped H atoms at low temperatures. Radiolytic H atoms arise from both the solid matrix and a dsorbed water. Under conditions of high dose rate, the H atoms mainly decay by reaction with matrix defects. An interesting detail of H atom diffusion in these systems is the apparent segregation into different "phases". The different phases can be silica and water (MCM-41) or they can be different pore systems in the solid (Y zeolite). Published by Elsevier Science Ltd.