Elucidation of Pt Clusters in the Micropores of Zeolite Nanoparticles Assembled in Thin Films

Abstract

Platinum clusters are prepared by γ radiolysis of beta zeolite suspensions (Pt-Beta) in the presence of a templating agent (tetraethylammonium hydroxide, TEAOH). Further, the Pt-Beta suspensions were stabilized with methyl cellulose and deposited in thin films with a thickness of 220 nm on silicon wafers. Elucidation of the size, distribution, and stability of the Pt clusters in the colloidal suspensions and thin films is provided by high-resolution transmission electron microscopy (HRTEM) combined with grazing incident X-ray diffraction (GI-XRD) measurements. The lateral length of the Pt clusters immobilized in the channels of the beta nanocrystals is between 1 and 2 nm. The presence of crystalline fringes with spacings of 0.23 and 1.26 nm corresponding to cubic Pt and zeolite beta are clearly seen in the HRTEM. The homogeneous distribution of the clusters along the film thickness is confirmed by GI-XRD measurements at two penetration depths. Besides, the location of the Pt clusters in the channels of beta nanoparticles is studied by FTIR spectroscopy. The Pt clusters confined in the channels of beta crystals decrease the total micropore volume and also lower the water sorption capacity in comparison with pure beta zeolite.

TPAOH Template Removal from High-Silica ZSM-5 by Low-Temperature Hydrocracking

“…分子筛膜具有规整的孔道结构、 良好的化学稳 定性、 机械强度、 热稳定性和催化性能, 在膜分离技 术和膜催化反应等领域具有潜在的应用价值, 从而 引起研究者们的广泛关注. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] 其中 MFI 型分子筛晶 体(Silicalite-1 和 ZSM-5 分子筛)具有独特的纳米孔 道结构以及较为成熟的合成工艺, 使得 MFI 型分子 筛膜成为被研究最多的一种分子筛膜. 8-14 制备合成 MFI 型分子筛膜一般需要添加有机胺模板剂, 在使 用前需要去除.…”

Modifiers versus Channels: Creating Shape‐Selective Catalysis of Metal Nanoparticles/Porous Nanomaterials

“…When MNPs are combined with zeolites by reduction of metal precursors, their applications in shape‐selective catalysis are intensively explored. Although the introduction of MNPs in zeolites explores the chemical reaction types in shape‐selective catalysis, such a preparation strategy possesses intrinsic limitation that some metal ions will actually diffuse out from framework matrices to form MNPs on the external surface, rendering the size and shape selectivity of zeolites‐based catalysts hard to be perfectly realized [18, 19] . With the development of synthetic methods, MNPs with various sizes, shapes and compositions can be obtained.…”

“…Although the introduction of MNPs in zeolites explores the chemical reaction types in shape-selective catalysis,such apreparation strategy possesses intrinsic limitation that some metal ions will actually diffuse out from framework matrices to form MNPs on the external surface,r endering the size and shape selectivity of zeolites-based catalysts hard to be perfectly realized. [18,19] With the development of synthetic methods,M NPs with various sizes,s hapes and compositions can be obtained. The catalyst can be prepared by encapsulating pre-synthesized MNPs during the growth of zeolites to keep all MNPs inside the matrices of zeolites and create better shape selectivity.…”

Crystallization pathway from a highly viscous colloidal suspension to ultra-small FAU zeolite nanocrystals

“…During the evaporation of water of the colloidal suspension (3), prior to hydrothermal synthesis, double-six membered rings (D6R), the secondary building units of the FAU structure were detected by insitu 29 Si NMR spectroscopy. Formation of the very first micropores in the nanosized particles was further confirmed by HP 129 Xe NMR spectroscopic measurements.OSDA [14][15][16][17][18][19][20][21][22] which highlights our current inability to use the fundamental understanding of zeolite crystal growth to design zeolites with specific properties, one of the most important challenge in zeolite synthesis.Recently, we published novel OSDA-free synthesis routes for nanosized EMT-, FAU-, SOD-, RHO-and CHA-type zeolites. [23][24][25][26] However, despite the good progress made in the synthesis of nanosized OSDA-…”

“…OSDA [14][15][16][17][18][19][20][21][22] which highlights our current inability to use the fundamental understanding of zeolite crystal growth to design zeolites with specific properties, one of the most important challenge in zeolite synthesis.…”