The hydrothermal synthesis of silicalite—an in situ small-angle neutron scattering study

Zeolite growth by synergy between solution-mediated and solid-phase transformations

“…Then, the soluble T-O À , T-OH species may regroup around the hydrated cations (Na + , TPA + ) to form the structure-directing agent containing T-O (SDA-T-O) species [52][53][54][55][56][57] which can undergo aggregation to form <3 nm primary sub-colloidal particles. 25,28,57,58 The primary sub-colloidal particles aggregate and densify into condensed aggregates (equilibrated gel). 25,27,28,59 The nucleation occurs in the equilibrated gel phase by gel reorganization.…”

“…25,27,28,59 The nucleation occurs in the equilibrated gel phase by gel reorganization. 21,25,27,58 Local energy dispersive X-ray (EDX) analysis showed that Na + cations were more concentrated at the surface of the equilibrated gel phase than at the surfaces of the gel particles and of the coffin shaped aggregates (Fig. 7).…”

“…The nucleation that occurred at the equilibrated gel with further dissolution of the T-O bonds could lead to the movement of the nuclei into both the liquid phase and the interface of the equilibrated gel phase. The formation process of the condensed primary aggregates and the crystallization that occurred in the equilibrated gel can be considered in the light of the model proposed by Dokter et al 27,58 for crystallization of silicalite from a clear homogeneous solution. However, in contrast to these models in which the nuclei are formed and Fig.…”

A thermosyphon-driven hydrothermal flow-through cell forin situand time-resolved neutron diffraction studies

“…Fortunately, techniques utilizing electromagnetic radiation or neutron waves are able to provide in situ information using specially designed hydrothermal cells because they can couple and penetrate certain materials. For example, many researchers have explored in situ hydrothermal reactions using techniques including UV-vis spectroscopy (Kawamura, 2002), Raman spectroscopy (Hurst et al, 2002;Maslar et al, 2009), IR spectroscopy (Kieke et al, 1996;Kazarian & Martirosyan, 2002), X-ray absorption spectroscopy (Brugger et al, 2007;Liu et al, 2007), angular dispersive X-ray diffraction (ADXRD) (Norby, 1997;Webster et al, 2009), energy dispersive X-ray diffraction (EDXRD) (Evans et al, 1995;Francis et al, 1999;Jorgensen et al, 2008), neutron diffraction (ND) (Walton et al, 1999;O'Neill et al, 2006), small-angle X-ray scattering (Testemale et al, 2005), small-angle neutron scattering (Dokter et al, 1994) and nuclear magnetic resonance (Gerardin et al, 2000).…”

Colloidal zeolites and zeolite membranes

“…6 The SANS technique is particularly appropriate because it can be used for in situ measurements even under hydrothermal conditions, and also when the colloidal particle concentration is very high. 7,8 Work on another zeolite system, zeolite A (LTA), will also be described. For this system the hydrothermal synthesis conditions have again been optimised so as to favour homogeneous nucleation and colloid formation.…”