The relative stability of SCM-14 germanosilicate with different distributions of germanium ions in the absence and presence of structure-directing agents

Abstract

We report computational study of the distribution of germanium ions among the double four-membered rings (D4Rs) in SCM-14 germanosilicate and the influence of the structure-directing agent (SDA) on the stability...

Variation of the Orientations of Organic Structure-Directing Agents inside the Channels of SCM-14 and SCM-15 Germanosilicates Obtained by Ab Initio Molecular Dynamic Simulations

“…The conclusions made in the previous work [ 21 ] were based on structural optimization using quantum chemical calculations performed at zero Kelvin. Those structures are denoted below as SO (from structural optimization).…”

“…The unit cell of the SCM-14 zeolite framework was taken from Ref. [ 21 ], where it was optimized as a pure periodic silicate structure with dimensions a = 20.92770 Å, b = 17.70280 Å, c = 7.58770 Å; α = β = γ = 90°. Since the unit cell in direction c is relatively small, we modeled the structure with a doubled unit cell in that direction, e.g., with c = 15.17540 Å.…”

“…Both zeolite materials have been synthesized with protonated 4-pyrrolidinopyridine as OSDA, compensated by fluoride anion. In our previous works, we considered various structures with this OSDA inside the zeolite channels with initial positions and orientations extracted from the XRD of the as-synthesized materials [ 21 ]. Those models have been optimized to the corresponding local minima and the obtained structures have been used to estimate the influence of the orientation of the OSDA on the relative stability of the zeolites with different distribution of germanium centers in the tetrahedral positions of the framework.…”

Synthesis and structure of the medium-pore zeolite PST-35 with two interconnected cages of unusual orthorhombic shape

“…It should be noted here that alternative assignments of F À encapsulation within d4rs have also been proposed. 42,43 Therefore, the preference of Ge substitution into the d4r cages of PST-35 does not appear to be high compared to the so-called ADORable germanosilicate zeolites such as IM-12 (UTL). 44 This can be further supported by the fact that all the 29 Si MAS NMR spectra of the as-synthesised PST-35(2.2), PST-35(3.9) and PST-35(6.6) show a featureless line shape (Fig.…”

Investigating the Physicochemical Properties of an Extra-large Pore Aluminosilicate ZEO-1

“…Note, however, that the presence of the template in the zeolite channels during the synthesis of the samples may influence to some extent the preferable crystallographic positions for aluminum in the framework, as shown both for aluminum and for other T atoms. 70,71 The most acidic hydroxyls are also at the T11 position of Al, followed by T16, T17, T8, and T21. As shown above, T8 and T17 are among the least stable positions for Al substitution, and Al is unlikely to be present in those sites.…”