Hydrothermal synthesis of nanosized SAPO-34 molecular sieves by different combinations of multi templates

In the present study, the silicoaluminophosphate (SAPO-34) nanoparticles were synthesized under hydrothermal conditions in the presence of a single or a mixture of tetraethyl ammonium hydroxide (TEAOH), morpholine, diethylamine (DEA) and triethylamine (TEA) as structure-directing agents (SDAs). The effects of different types, amounts and combinations of templates on the structure and morphology of SAPO-34 molecular sieves were investigated by XRD, SEM, EDX and BET analyses. Compared with the single template synthesized, using two, three and four SDAs leads to the crystallinity increase, the crystallite size reduction and the morphology change to spherical aggregates of several cubic nanosized crystals. Furthermore, decreasing molar ratio of TEAOH in initial gel from 2 to 0.4 do not change the purity of SAPO-34, but affect its crystallinity and particle size. Small SAPO-34 particles and large BET surface area are obtained when three or four templates are used as SDAs.