Hierarchical Porous Zeolite Composite with a Core−Shell Structure Fabricated Using β-Zeolite Crystals as Nutrients as Well as Cores

Abstract

A hierarchical porous zeolite composite possessing β-zeolite cores and Y-zeolite polycrystalline shells (denoted as BFZ) is synthesized by a two-step hydrothermal crystallization procedure and characterized by X-ray diffraction (XRD), N2 adsorption−desorption, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-dispersive spectrometry (EDS), NMR, intelligent gravimetric analyzer (IGA), and in situ infrared (IR) spectrometry of pyridine. The results show that a hierarchical pore structure with the pore size centered around 6.9, 10.3, and 16 nm is created in the composite. A more than 2 orders of magnitude gas transport improvement is, therefore, achieved in the composite as compared with the corresponding physical mixture. The conversion of liquid-phase hydrogenation of benzene over H-BFZ supported by 3 wt % Ru is much higher than those over H-Y or H-β-zeolites supported by the same Ru loading due to the improved diffusion and acid accessibility as well as the enhanced Ru dispersion because of the introduction of hierarchical pores.

Synthesis of Wool-Ball-Like ZSM-5 with Enlarged External Surfaces and Improved Diffusion: A Potential Highly-Efficient FCC Catalyst Component for Elevating Pre-cracking of Large Molecules and Catalytic Longevity

“…Contrarily, the uptake rate of n-octane in the hierarchical NZSM-5 is greatly enhanced, especially in the initial stage where the uptake is sharply increased and a similar uptake of 80 % is achieved only after 20 min. It is well known that the formation of nanos-sized zeolite crystals does not change the micropore properties in terms of adsorption and diffusion [3,38]. The intrinsic diffusivity of n-octane in the micropores should be the same in the hierarchical NZSM-5 and in the reference sample TZSM-5.…”

“…This fitting leads to a characteristic diffusion time of L 2 /D = 1.5 9 10 5 s. Combined with L = 20 lm, a diffusivity ''D'' of approximately 2.6 9 10 -17 m 2 s -1 is obtained. Since the diffusivity in the micropores of both the NZSM-5 and the reference TZSM-5 is the same [3,38], the n-octane uptake curve over the reference TZSM-5 can then be used to estimate the characteristic diffusion length in the hierarchical NZSM-5 zeolite. The characteristic diffusion time has been determined during the initial uptake up to q(t)/ q(m) = 0.5, where a straight line has been obtained (Fig.…”

Structural features of core–shell zeolite–zeolite composite and its performance for methanol conversion into gasoline and diesel

“…53 Although there is a difference by the different analysis technology, Elemental analysis obtained by XPS and EDS (in Table I) displays that shell layer zeolite is not "Silicalite-1", but an MFI-type zeolite with the different Si/Al ratios. It can be seen from Table I that the SiO 2 / Al 2 O 3 ratios (mol/mol, obtained by XPS) of the shell layer zeolites of MMZsa1 and MMZsa2, which were prepared by the similar procedure while with a different precursor yielding the shell, are about 42-81 and 62-111, respectively.…”

“…Obviously, not only does the Si/Al ratio of the shell layer zeolite in the zeolite-zeolite composites, but the diffusion length of the catalysts plays an important role in the catalytic performances also. 51,53 As compared with ZSM-5(orig.) and ZSM-5(at), the higher average yields of fuel oil over the core-shell composite MMZsa catalysts as shown in Fig.…”

Magnetic hetero-structures as prospective sorbents to aid arsenic elimination from life water streams

“…The sorbents so far used to remove arsenic from aqueous solutions and waste water streams include, novel fabricated copper ferrite (Yao et al, 2012), magnetic ion exchange resins, magnetic graphene oxide composites, granular ferric hydroxide, hydrous ion oxide particles, sulfur modified iron, activated alumina, iron oxide-coated microsand (Sinha et al, 2011), iron oxide/activated carbon magnetic composite (Yao et al, 2014), metal oxide heterostructures , nanocrystalline magnetite (Mayo et al, 2007), Fe 3 O 4 nanoparticle-coated boron nitride nanotubes (Chen et al, 2011), FeO nanoparticles (Wu et al, 2009), dendrimer-conjugated magnetic nanoparticles (Chou and Lien, 2011), magnetic multi-granule nanoclusters (Lee et al, 2014), maghemite nanoparticles (Tuutijärvi et al, 2009), bi-metal doped nanosorbent (Kumar et al, 2011), poly(acrylo-amidino ethylene amine) nanofiber (Dinhthao et al, 2013). Moreover, development of materials with heterogeneous structures, like porous (Li et al, 2007;Xin et al, 2008), spheres Jia et al, 2012;Wu et al, 2010), hierarchical materials (Koekkoek et al, 2011;Xin et al, 2013;Zheng et al, 2010;Xin et al, 2010), nanotubes (Yan et al, 2010), nanocomposites (Wang et al, 2013a), ultrafine magnetic nanoparticles (Rostamnia et al, 2013;Tang et al, 2011), sheets (Yan and Xue, 2005;Koekkoek et al, 2013;Wang et al, 2013b), nanowires (Wang et al, 2007;Han et al, 2011), and binary metal oxides (Xin et al, 2004;Zhao et al, 2013). These sorbents are anticipated to detect and rectify the problem of water pollution by various researchers.…”