AlPO-18 nanocrystals synthesized under microwave irradiation

Abstract

AlPO-18 nanocrystals (AEI type structure) were synthesized from clear precursor solutions by employing microwave energy. The samples were heated at 130 °C for 5–60 min, and complete crystallization of nanosized AlPO-18 occurred after 30 min. Additionally, micron-sized AlPO-18 molecular sieve was synthesized in a dense gel precursor system; the crystallization behaviour of both nano- and micron-sized AlPO-18 was investigated. The size and morphology of micron-sized AlPO-18 crystals differ substantially from the nanosized molecular sieve exhibiting a high degree of monodispersity and stability in H₂O suspensions. The stability of AlPO-18 crystal suspensions was followed with zeta potential measurements at different pH and sol concentrations. According to thermogravimetric analyses and isothermal adsorption/desorption of both nitrogen and water, the nanosized AlPO-18 possesses a larger accessible pore volume and a higher water affinity than the micron-sized crystals.