Formation of silica–surfactant mesophases studied by real-time in situ X-ray powder diffraction

Abstract

Real-time in situ energy dispersive synchrotron X-ray powder diffraction data provides evidence for the formation of an intermediate lamellar silica-surfactant intercalate during the synthesis of the hexagonal mesophase derived from the layered polysilicate kanemite, whereas n o intermediate phases are observed during the formation of the silica-surfactant mesophase that leads t o the mesoporous material MCM-41.

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.…”

From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis

“…There is a particularly interesting study which follows the formation of silica-surfactant mesophases by real time in situ X-ray powder diffraction. 267 226 found that the pore size distribution is broader in the case of FSM-16, where the total pore volume and hydrocarbon sorption capacity is about 5 times higher in the case of the MCM-41 materials. On the other hand, due to a higher degree of condensation in the silica walls in the FSM-16, this has a higher thermal and hydrothermal stability than MCM-41.…”

Synthesis of Layered Platinum-Based Materials Through Thermal Decomposition of Self-Assembled Metal Carbonyl-Surfactant Phases

“…This pattern closely resembles that displayed by mesoporous materials in an early stage of formation or decomposition with randomly ordered tubes. [8,19] Transformations from a layered to a hexagonal phase have been observed before, [20] however TEM images of this sample show a completely amorphous structure. The C, H, and N elemental analysis of this material was virtually identical to that of the material heated at 70 C for two days, indicating that there was no further loss of CO or surfactant, but only a reordering of the structure into an ill-defined mesostructured phase.…”