Novel surfactant-free route to delaminated all-silica and titanosilicate zeolites derived from a layered borosilicate MWW precursor

Abstract

a Layered borosilicate zeolite precursor ERB-1P (Si/B = 11) is delaminated via simultaneous deboronation and SDA removal, to yield material DZ-1 consisting of silanol nests, using a simple aqueous Zn(NO 3 ) 2 treatment. Characterization of this synthesis process by PXRD shows loss of long-range order, and transmission electron microscopy (TEM) demonstrates transformation of rectilinear layers in the layered zeolite precursor to single and curved layers in the delaminated material. N 2 physisorption confirms the expected decrease of micropore volume and increase in external surface area for delaminated materials relative to their calcined 3D zeolite counterpart. Elemental analysis shows loss of B and absence of Zn in the delaminated material. Resonances corresponding to silanol nests are evident via 29Si solid-state NMR spectroscopy in DZ-1, which should be located within 12-MR pockets near the external surface. We have successfully utilized these nests as tetrahedral recognition sites for incorporation of Ti within an isolated framework coordination environment in material Ti-DZ-1. Diffuse-reflectance ultraviolet (DR-UV) spectroscopy of Ti-DZ-1 confirms isolated framework Ti sites, which are assigned to bands in the range of 210 nm-230 nm. Infrared spectra of Ti-DZ-1 consist of a distinct absorption band at 960 cm, which is absent in DZ-1 prior to Ti incorporation and has been previously correlated with the presence of framework Ti species. Infrared spectra after pyridine adsorption demonstrate bands consistent with Lewis-acid sites in the resulting Ti-substituted delaminated zeolite. The accessibility of these Lewis-acid sites is confirmed when using Ti-DZ-1 as a catalyst for cyclohexene epoxidation using tert-butyl hydroperoxide as the organic oxidant -a reaction for which both DZ-1 and TS-1 are inactive.

Insights into Redox Dynamics of Vanadium Species Impregnated in Layered Siliceous Zeolitic Structures during Methanol Oxidation Reactions

“…From a practical perspective, Si‐ITQ‐6 proved to be a promising siliceous support to obtain a good dispersion of vanadium by applying a simple impregnation method and a low‐cost salt precursor. Herein, we based our study on the classical methodology for synthesis of these supports, however recent studies have been developed to simplify the exfoliation methods in lamellar zeolitic structures, providing a good perspective on expanding the application of these materials in catalytic processes.…”

“…From a practical perspective, Si-ITQ-6 proved to be a promising siliceous support to obtain a good dispersion of vanadium by applying a simple impregnation method and a low-cost salt precursor. Herein, we based our study on the classical methodology for synthesis of these supports, [58] however recent studies have been developed to simplify the exfoliation methods in lamellar zeolitic structures, [59][60][61][62][63][64] providing a good perspective on expanding the application of these materials in catalytic processes. After preparation and stirring, the solution was heat treated in a stainless-steel autoclave at 150°C for 120 h. The solid product was separated by filtration, washed with distilled water and dried at 80°C for 24 h. Preparation of supports.…”

Heteroatom-Substituted Delaminated Zeolites as Solid Lewis Acid Catalysts

“…All spectra in Figure S2 show the absence of a QS5 NMR spectra of DZ-1 ( Figure S2(b)) shows a very sharp resonance at -98 ppm, which is assigned to hydroxyls of silanol nests, as well as a shoulder at -101 ppm 13 …”

New Trends in Layered Zeolites

“…The obtained delaminated Al-containing ERB-1-del showed a similar morphology of single thin layers as the conventional delaminated ITQ-2 material and showed higher activity in Friedel-Crafts acylation reactions involving bulky substrates compared to 3D ERB-1C zeolite, due to the enhanced external surface area (133 vs 53 m 2 /g). An all-silica analog of ERB-1-del can be obtained by treating ERB-1 lamellar precursor with warm Zn(NO 3 ) 2 solution with a pH value of ~1 [68]. However, the one-step mild delamination strategy is now restricted to ERB-1 lamellar precursor and has its limitations in the general application.…”