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Li X.,Beijing University of Chemical Technology | Li B.,Beijing University of Chemical Technology | Xu J.,Beijing University of Chemical Technology | Wang Q.,Sino Petrochemical Research Institute | And 4 more authors.
Applied Clay Science

Lanthanide ion-containing (Ln = La3+, Ce3+) micro/mesoporous composite molecular sieves Ln-ZSM-5/MCM-41 were prepared under hydrothermal condition using kaolin as silica and alumina sources. X-ray diffraction patterns and nitrogen adsorption data confirmed the presence of mesoporous MCM-41 and microporous ZSM-5 in the composite. High resolution transmission electron microscope and scanning electron microscope studies revealed that the micro- and mesoporosity of the composite were different from that of the mechanical mixture of ZSM-5 and MCM-41. The overall local environment of lanthanide ion in the composite molecular sieves was investigated by Fourier-transform infrared and ultraviolet-visible spectroscopy. The lanthanide ions were tetrahedrally or distorted tetrahedrally coordinated by oxygen ions. Pyridine-infrared spectroscopy was used to detect the acidic sites of the samples. A large amount of Brønsted and Lewis acidic sites were measured, and the amount of Brønsted acidic sites was increased significantly by La3+ or Ce3+ incorporation. Thus, the inexpensive kaolin can be used as alumina and silica source for ordered micro/mesoporous composite molecular sieves. The catalytic activity of the samples was tested by the esterification of acetic acid with n-butyl alcohol and showed high conversion. © 2010 Elsevier B.V. Source

Mao H.,Beijing University of Chemical Technology | Mao H.,Jiangsu Polytechnic University | Li B.,Beijing University of Chemical Technology | Li X.,Beijing University of Chemical Technology | And 5 more authors.
Microporous and Mesoporous Materials

Facile synthesis of titanium containing silica-pillared clay derivatives with ordered mesoporous structure from a novel intra-gallery templating route is successfully established. The ordered mesoporous titanium containing silica-pillared clay materials obtained by a surfactant-directed assembly of silica species in the interlayer space of natural montmorillonite, are characterized by a mesoporous structure with uniform pores (2.7 nm) between the layers. These results indicate that surfactant plays a decisive role in pore formation, because it acts as a micelle-like template during the hydrolysis of organic precursor. The main titanium species was tetrahedrally coordinated in the gallery silica framework. The increase of Ti content leads to a gradual reduction of quality of pore structure and of the pore volumes. Up to a Ti loading corresponding to Si/Ti = 20 the titanium is mainly tetracoordinated and the highest conversions of cyclohexene with anhydrous tert-butylhydroperoxide are obtained, with excellent selectivity for the epoxide. However, a further increase of Ti content to Si/Ti of 10 and 5, leads to an undesirable decrease of conversion and selectivity. © 2009 Elsevier Inc. All rights reserved. Source

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