Weibin Fan

Fe-containing Y as a host for the preparation of a ship-in-a-bottle catalyst

Abstract Encapsulation of Fe(phen) 3 in zeolite Y via directly complexing hydrothermally synthesized FeY with phenanthroline (abbreviated as phen) was first tried. The as-prepared materials have been characterized with XRD, FTIR, diffuse reflectance UV-vis spectroscopy (DRS), TG/DTA and ICP techniques. Further, their catalytic performance was also explored with cyclohexane oxidation and styrene oxidation as model reactions. It has been shown that Fe(phen) 3 is stably immobilized on zeolite Y, as proved by its basically unchanged catalytic property within three reaction recycles for the oxidation of cyclohexane. The as-prepared Fe(phen) 3 /Y exhibits much stronger oxidation ability than FeY and Fe(phen) 3 /Y prepared by the conventional flexible ligand method where Fe ions were introduced into the host by ion-exchanging Na + cations.

Hydrothermal synthesis of Co-rich CoAPO-5 molecular sieves

Arn series of CoAPO-5 materials have been hydrothermally synthesized to maximize the degree of isomorphousrn substitution of Co2+ ions in the AFI framework. The as-synthesized as well as the calcined CoAPO-5 materialsrn have been characterized with XRD, SEM, ICP, DRS (diffuse reflectance spectroscopy) and FT-IR techniques.rn Optimum conditions for the synthesis of Co-rich CoAPO-5 molecular sieves have been obtained by evaluatingrn the influence of the amount and type of cobalt source, the type of aluminium source, the type of templatern molecule, the [template]:rn[P2O5] ratio and the amount of different monovalent cations on the isomorphous substitutionrn of Co2+ in the lattice. It will be shown that highly-crystalline hexagonal CoAPO-5 crystals with a substitution degree of 12% can be obtained from a CsCl·Co(CH3COO)2·4H2O·pseudo-γ-AlO(OH)·H3PO4·(C2H5)3N·H2O gel (with [(C2H5)3N]:rn[P2O5] and [CsCl]:[Co(CH3COO)2] ratios of respectively 1.0 and 0.5) autoclaved forrn 41 h at 190°C. In addition, the effect of monovalent cations on the redox properties of Co2+ in CoAPO-5rn molecular sieves will be discussed. The degree of oxidation of framework Co2+ to Co3+ isrn always relatively low and increases in the order Li+<K+≈Rb+≈Cs+<NH4+≈Na+. Thus, the addition of Li+ results in arn stabilization of Co2+ in the framework of CoAPO-5rn molecular sievesrn upon calcination.

Synthesis and characterization of ZSM-48 in the pure solid system

Abstract NaZSM-48 has been synthesized successfully in a pure solid system of Na 2 Oue5f8SiO 2 ue5f8Al 2 O 3 ue5f8H 2 N(CH 2 ) 6 NH 2 . This method greatly increased the yield of products and decreased the pollution of waste liquid. XRD patterns and data of the as-synthesized sample closely matched those of ZSM-48 synthesized hydrothermally. The sample was also examined with SEM, t.g.-d.t.a., and i.r.; and the crystallization kinetics in the system was studied. The results showed that both the hexan-1,6-diamine (HEXDM) content and the autoclave type greatly influenced the crystallization. Framework FT i.r. bands of the as-synthesized ZMS-48 were shifted toward lower frequencies than those of ZSM-48 synthesized in aqueous and nonaqueous systems.

Novel approaches to synthesize self-supported ultrathin carbon nanowire arrays templated by MCM-41

Ordered self-supported ultrathin carbon nanowire arrays with small mesopore sizes have been fabricated for the first time employing mesoporous silica MCM-41 as the templates, and two possible related mechanisms are proposed.

MWW-type titanosilicate: Novel preparation and high efficiency in the epoxidation of various alkenes

Abstract A novel postsynthesis method has been proposed to prepare a highly efficient titanosilicate catalyst with the MWW topology, Ti-MWW. The so-called reversible structural conversion method is based on a structural interchange between 3-dimensional MWW silicate and its lamellar precursor together a simultaneous incorporation of titanium through the treatment with an aqueous solution of titanium source and cyclic amine. This method overcomes the restriction problem between pore windows and titanium precursor probably encountered in the usual method using TiCl 4 vapour at elevated temperatures. The catalytic properties of postynthesized Ti-MWW have been investigated by comparing with hydrothermally synthesized one as well as the conventional titanosilicates of TS-1 and Ti-Beta in the epoxidation of various alkenes with hydrogen peroxide. Ti-MWW proves to be more effective in the epoxidation of both simple and functionalized alkenens. Particularly, the novel postsynthesis method of a reversible structural conversion incorporates more active Ti species into the framework than the conventional hydrothermal synthesis, leading to the most active epoxidation titanosilicate catalyst so far. Ti-MWW has been further delaminated into thin sheet material which possesses an extremely open and accessible surface area but maintains the basic structure of zeolite. Delaminated Ti-MWW catalyzes the epoxidation of bulky substrates of various cycloalkenes more actively than other titanosilicates including mesoporous Ti-MCM-41.

Effects of introduction of different alkali metal halides on crystallization and characteristics of ZSM-48 in a solid reaction mixture system Effects of alkali metal chlorides

Abstract Alkali metal chlorides have significant effects on the crystallization and characteristics of MNaZSM-48 (M = Li, Na, K, Rb, Cs) zeolites. XRD patterns showed that introduction of different alkali metal chlorides does not strongly affects the structures of the products, but it greatly slows down zeolites crystallization rates. The as-synthesized samples are also characterized by SEM, TG/DTA, XPS and plasma spectra. It was shown that the crystal morphologies and sizes, and the thermal properties depend on the kinds of alkali metal chlorides. KNaZSM-48 and RbNaZSM-48 are not stable, and easily transform into α-SiO2 through calcination. The SiO2/Al2O3 ratios in the bulk of MNaZSM-48 are basically the same, but the SiO2/Al2O3 ratios on the surface are strongly different. The catalytic measurement showed that KNaZSM-48, RbNaZSM-48 and CsNaZSM-48, used as supports of catalysts, respectively, possess better catalytic properties in the CO hydrogenation to light olefins.

07-P-10 - Preparation and catalytic property of FeL/Y composite by a new method

Publisher Summary This chapter describes the preparation and catalytic property of FeL/Y composite by a novel method. A novel method––that is, the recrystallization of MCM-41 impregnated metal complex in the synthesis system of zeolite Y––has been developed to immobilize the guest complex in zeolite host. In this way, a series of FeL/Y composites have been prepared. The as-prepared materials are characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and ultraviolet-visible (UV-vis) technique. Their catalytic properties in the reaction of cyclohexane oxidation are also investigated. This method made it possible to immobilize different metal complexes, including the cationic, the anionic, and the neutral. The content of metal complex can be controlled by varying its amount impregnated on MCM-41.

Ti-MWW and related materials as efficient oxidation catalysts

A novel titanosilicate with the MWW topology, Ti-MWW, has been prepared by direct hydrothermal synthesis using boric acid as a structure-supporting agent, and also by post-incorporation of tetrahedral Ti species into MWW silicalite through controlled structural conversions between 3-dimensional crystalline MWW silicalite and its lamellar precursor. The catalytic properties of Ti-MWW have been compared with those of conventional titanosilicates. Hydrothermally synthesized Ti-MWW proves to be more effective in the epoxidation of linear alkenes including functionalized ones, and also exhibits considerable activity for cycloalkenes using hydrogen peroxide as oxidant. Postsynthesized Ti-MWW, almost free of boron, catalyzes the alkene epoxidation more effectively as a result of the tetrahedral Ti species different from those resulting from the direct synthesis, which turns out to be the most active titanosilicate catalyst for epoxidation so far. The activity of Ti-MWW in the ammoximation of cyclohexanone is superior to that of TS-1, which is being industrially used. A new interlayer-expanded structure analogous to MWW has been prepared in the form of titanosilicate and denoted by Ti-YNU-1. Ti-MWW is further converted by phase delamination into a thin sheet material. Ti-YNU-1 and delaminated Ti-MWW catalyze the epoxidation of bulky cycloalkenes more actively than Ti-MWW or large pore titanosilicates as well as mesoporous Ti-MCM-41.

Crystallization mechanism study on ZSM-48 in the system Na2O-Al2O3-SiO2-H2N(CH2)6NH2

Abstract The crystallization mechanism of ZSM-48 in the system Na2O-Al2O3-SiO2-H2N(CH2)6NH2 was studied by using XRD, SEM, TG/DTA, FTIR, XPS and plasma spectra techniques. It is shown that the reaction mixture is crystallized through solid—solid mass transformation. It was found, by tracing the crystallization process, that a secondary gel composed of silicate and aluminosilicate, in which SiO4 and AlO4 tetrahedra quickly form with some Al atoms, transferred to the surface, before generating nuclei. Possibly, a C-model (can and cement model) may be used to elucidate the evolution of nucleation. SEM showed that dendritic and entangled nuclei first form in the inner portion of the solid fraction. TG/DTA showed that the organic amine content in the solid sample increases with increasing crystallinity, which gives strong evidence for the organic amine being a template. FTIR revealed that the structure consisting of six-membered rings and double five-membered rings forms after about eight days through rearrangement and coalescence.

Synthesis of Co-rich CoAPO-CHA Molecular Sieves in the Presence of Ethanol and Caesium

CoAPO-CHA molecular sieves with Co(II) occupying n75% of the framework Al sites can be synthesized in the presence of ethanol nand caesium.