Morphology/crystallographic evolution of nanostructured SAPO-34 using simultaneous surfactant and Si source towards production of lower olefins: enhancement of lifetime and regenerative properties

In this research, simultaneous effect of Si source and CTAB application as surfactant was investigated in SAPO-34 preparation used for MTO process. Prepared samples were evaluated by FESEM, XRD, FTIR, BET and EDX analysis. TEOS application as Si source results in small crystallites of SAPO-34 due to its better solubility and smaller size. Consequently, in this case, CTAB cations could perform their hydrophobic capping effect more efficiently, because it is easier to create a hydrophobic cap around small crystallites compared to large ones. In case of fumed silica application, it seems that CTAB molecules cannot function as hydrophobic cap due to the larger crystallite size. The mentioned explanation was supported by the presented FESEM analysis. SAPO-34 with fumed silica as Si source has large crystallites which is leading to longer intracrystalline diffusion length enough for the reaction species and finally turning out to be coke deposition.

Automated summary

The simultaneous effect of Si source and CTAB application as a surfactant on SAPO-34 preparation was investigated. TEOS as the Si source resulted in small crystallites of SAPO-34, while fumed silica led to larger crystallites.