Adsorption and desorption properties of toluene on an Ni-encapsulated Beta zeolite catalyst

Hydrocarbon trap (HCT) catalysts are promising automotive catalysts for purifying hydrocarbons in exhaust gas. Zeolites are suitable for use in these catalysts because of their high durability under hydrothermal conditions. Ni-encapsulated Beta zeolite (Ni@Beta) was obtained with Ni phyllosilicate as the Ni precursor. Ni@Beta exhibited higher toluene adsorption and desorption capabilities than those of Ni-impregnated Beta (Ni/Beta), and the Ni@Beta structure was stable after thermal aging at 900 °C. Moreover, Ni@Beta chemically adsorbed toluene after aging owing to the encapsulated Ni particles, which functioned as adsorption sites. In addition, the introduction of Ga into Ni@Beta improved the structural stability, and thus, the specific surface area was maintained at 80% after thermal treatment. Thus, this study provides an effective strategy for synthesizing HCT catalysts.