Synthesis and Characterization of the All‐Silica Pure Polymorph C and an Enriched Polymorph B Intergrowth of Zeolite Beta

Abstract

Previously elusive, the all‐silica pure polymorph C of zeolite beta and a material enriched with polymorph B (see picture) are prepared by high‐throughput (HT) synthesis in the presence of a cationic organic structure‐directing agent (SDA). The presence of K+ ions is essential for the formation of these materials; furthermore, a high ratio of OH− ions to silicon atoms favors the crystallization of polymorph C.

Solvent‐Free Synthesis of ITQ‐12, ITQ‐13, and ITQ‐17 Zeolites

“…[15,17] Usually, ITQ zeolite synthesis is performed in the presence of costly organic templates under hydrothermal conditions, where a large amount of water solvents are necessary. [18][19][20][21][22][23][24][25] Obviously, the use of these expensive organic templates increases the ITQ zeolites cost, and a large amount of water solvent occupies a big space in autoclaves, which strongly influence zeolite yields. Therefore, it is desirable to develop the sustainable route for synthesizing ITQ-family zeolites.…”

Understanding the Role of Internal Diffusion Barriers in Pt/Beta Zeolite Catalyzed Isomerization of n‐Heptane

“…Based on the above observations,t he Beta samples are both highly crystalline with similar particle size,but different internal structures.F or polycrystalline Beta-A, numerous internal interfaces are present, and there are potential mismatches in structure and pore alignment, as well as amorphous phase on these interfaces. [22,28,29] Fors inglecrystalline-like Beta-B,n oi nternal interfaces are observed via the above characterization methods.S ome invisible interfaces might exist in both samples; [26,27] their possible effect on diffusion is not the focus of this work, but the impact of additional interfaces for Beta-A is. Figure 2d isplays the acidic properties of the two assynthesized Beta samples.T he NH 3 -TPD curves in Figure 2a are composed of two desorption peaks,o ne at low temperature and the other at high temperature.T he desorption temperature reflects the acid strength, and the peak area corresponds to the number of acid sites.The numbers of weak and strong acid sites are close for Beta-A and Beta-B, although the number of acid sites in Beta-A is slightly higher.…”

“…Theapparent activity and selectivity of the two Pt/Beta catalysts were compared to probe the influence of internal interfaces.E ventually,i nternal diffusion barriers on the interfaces were demonstrated by analyzing the apparent diffusivities of the Beta samples.The experimental details are given in the Supporting Information. Figure 1illustrates the structure,morphology,and texture of the two as-synthesized Beta samples.The XRD patterns in Figure 1a display the characteristic peaks of the typical BEAtype structure,i ndicating the successful synthesis of Beta zeolite.C ompared to Beta-B,B eta-A shows al ower peak intensity and its relative crystallinity is calculated to be 91 %, suggesting that Beta-A contains ah igher fraction of amorphous phase.I ti sw orth noting that any Beta zeolite is considered to be an intergrowth of polymorphs; [26,27] quantifying these polymorphs requires further structural characterization that, however,d oes not impact the comparison [*] Z.…”

“…Theapparent activity and selectivity of the two Pt/Beta catalysts were compared to probe the influence of internal interfaces.E ventually,i nternal diffusion barriers on the interfaces were demonstrated by analyzing the apparent diffusivities of the Beta samples.The experimental details are given in the Supporting Information. Figure 1illustrates the structure,morphology,and texture of the two as-synthesized Beta samples.The XRD patterns in Figure 1a display the characteristic peaks of the typical BEAtype structure,i ndicating the successful synthesis of Beta zeolite.C ompared to Beta-B,B eta-A shows al ower peak intensity and its relative crystallinity is calculated to be 91 %, suggesting that Beta-A contains ah igher fraction of amorphous phase.I ti sw orth noting that any Beta zeolite is considered to be an intergrowth of polymorphs; [26,27] quantifying these polymorphs requires further structural characterization that, however,d oes not impact the comparison between Beta-A and Beta-B.T he SEM images in Figure 1c and ds how that the two Beta samples possess close average particle sizes (240 nm for Beta-A, 300 nm for Beta-B), but different morphologies.Beta-A displays very coarse external surfaces and ill-defined external shapes,s uggesting that the sample could be polycrystalline,w ith numerous internal interfaces;B eta-B,i nc ontrast, has smooth external surfaces and well-faceted external shapes,s uggesting that the sample could be single-crystalline-like,w ith few internal interfaces. TheH RTEM images and SAED patterns in Figure 1e and f prove that Beta-A is polycrystalline,w hile Beta-B is almost single-crystalline.T he Beta-A particle consists of nano-sized crystals with an average size of 28 nm, and its SAED pattern displays diffraction rings,w hile the Beta-B sample shows ordered lattice fringes and aSAED pattern with bright spots.…”

Advances in the synthesis of titanosilicates: From the medium pore TS-1 zeolite to highly-accessible ordered materials

“…The synthesis was done in the presence of a buffered media with hexafluorosilicate species and K + cations using SDA1 as organic structure directing agent (see Figure 4a). 36 After achieving the synthesis of the pure silica polymorph of ITQ-17, the synthesis of the titanosilicate form was attempted under the same synthesis conditions. However, the presence of potassium cations precluded the insertion of Ti species in framework positions.…”