Time-Resolved in Situ X-ray Powder Diffraction Study of the Formation of Mesoporous Silicates

Abstract

In situ, time-resolved energy-dispersive X-ray diffraction has been used to investigate the formation of the mesoporous silicates FSM-16 and MCM-41. The data suggest that the silicasurfactant mesophases formed are highly dependent on the reactant medium, the effect of the silica source being one of the main determining factors. Kanemite, a layered polysilicate, proves to be an excellent silicate source, giving rise to relatively ordered mesophases and subsequent highly ordered mesoporous silicate products. The time-resolved in situ X-ray diffraction data of the kanemite-alkytrimethylammonium system indicated that the silicasurfactant mesophase precursor to FSM-16 forms from a medium containing a number of intercalated silicate phases, while in contrast, the hexagonal mesophase precursor to MCM-41 forms from a medium containing no other ordered silicate-surfactant phases detectable by in situ X-ray diffraction.

Catalytic oxidation of cyclohexene over metalloporphyrin supported on mesoporous molecular sieves of FSM-16 type—Steric effects induced by nanospace constraints

“…It is worthwhile to note that the reported catalytic results and the conclusions concerning the distribution of Al in FSM-16 solids have important implications for understanding the mechanism of FSM-16 formation. In particular, they represent an indirect evidence for the postulated occurrence of fragmentation of kanemite layers [10][11][12][13], since only then a preferential accumulation of Al at the inner pore walls of directly aluminated solids is conceivable. This issue will be discussed in detail in our forthcoming paper.…”

“…The present work reports the results of catalytic oxidation of cyclohexene with iodosylbenzene over metalloporphyrin supported on aluminated mesoporous silicas of FSM-16 type, which are materials obtained from synthetic layered mineral kanemite [9]. It has been demonstrated that the kanemitederived materials are formed via mechanism essentially different from that of MCM-41, despite the use in both cases of cationic surfactants as structure directing agents [10][11][12][13]. It has been proposed that, after intercalation of the surfactant cations between the silicate layers, a transformation occurs to a layered mesophase containing fragmented silicate sheets, which is the actual precursor of the FSM-16 structure.…”

Catalytic performance of iron-mesoporous nanomaterials synthesized by a microwave-hydrothermal process

“…FSM-16 materials are formed via a folded sheet mechanism in which the condensation of the reactive silanol groups present on the adjacent silicate layers in CTMA kanemite complex leads to the formation of a hexagonal array of channels with uniform pore size [2]. This mechanism is further substantiated by in situ energy dispersive X-ray diffraction (EDXRD) measurements [6]. Moreover, the M-H synthesis of molecular sieves is a relatively new area of research [7][8][9][10][11][12][13][14].…”

Ordered Mesoporous Silica Derived from Layered Silicates

“…In contrast, they claimed that 2D hexagonal FSM-16 is formed via dissolving silicate sheets, meaning that FSM- 16 formation of FSM-16. [86,87] On the other hand, a 2D hexagonal phase was formed directly for MCM-41 without any intermediates. These results show the difference in the formation mechanisms of FSM-16 and MCM-41 but do not verify whether the materials themselves (FSM-16 and MCM-41) are different or not.…”