Fast preparation of ERI-structure AlPO-17 and SAPO-17 in the presences of isomorphous and heterogeneous seeds

Pure-phase ERI-structure AlPO-17 and SAPO-17 crystals were prepared using isomorphous (AlPO-17) and heterogeneous (zeolite T, SSZ-13 and SAPO-34) seeds. These heterogeneous seeds acts as the sole silica source for SAPO-17 preparation in most of cases. Crystallization mechanism of SAPO-17 and phase transformation process were demonstrated. On contract, SAPO-17 with impurity phases were obtained by in-situ synthesis. Seeded growth using the two kinds of seeds enhanced the crystallization rates by factors of 10–30 compared with in-situ synthesis. Physicochemical properties and Si, Al and P chemical environments of the products were characterized using X-ray diffraction, scanning electron microscopy, N₂ adsorption-desorption, thermogravimetric analysis, inductively coupled plasma elementary analysis, magic-angle-spinning solid-state NMR spectroscopy and temperature-programmed NH₃ desorption. Synthesis of SAPO-17 with all Si in isolated state demonstrated that SAPO-17 crystallization proceeded by a dissolution-construction mechanism. It included twice phase conventions: dissolved silica-rich zeolites inducing the formation of AFI-structure SAPO-5 and AFI structure converting to ERI framework.