Wenqin Pang

The preparation of highly ordered MCM-41 with extremely low surfactant concentration

Highly ordered pure-silica MCM-41 materials possessing well-defined morphology have been successfully prepared with extremely low surfactant concentration at room temperature. TEM, XRD, and NMR techniques; and synthetic factors (such as pH and amount of water) have been investigated extensively. Experimental results suggested that highly ordered MCM-41 material was formed by a deposition mechanism with silicate rod-like micelles.

Synthesis and structure of the [AlPO4]12 Pr4NF molecular sieve with AFI structure

Large single crystals (500 × 80 μm) of the structure type AFI have been obtained at 170°C using a synthesis medium containing F− anions. The new as-synthesized phase [AlPO4]12 Pr4NF crystallizes in space group P6cc with a = 13.740(5) A and c = 8.474(4) A (Z = 1). The crystal structure has been refined to Rw = 0.042. The Pr4N+ cations are in the large 12-ring channels of the framework, their fourfold inversion axis coinciding with the sixfold axis of the lattice. The F− anions are located in the “wall” of the framework between two (Al,P)O4 4-rings. This unusual position could be confirmed by 31P MAS n.m.r. spectroscopy.

Strategies for the synthesis of large zeolite single crystals

Abstract The formation of large zeolite single crystals can be achieved by controlling the factors affecting the crystallization process. A review of several major strategies for the synthesis of large zeolite single crystals based on our studies is presented. Through the addition of a nucleation suppresser to the reaction mixture and optimization of the synthesis conditions, pure uniform large single crystals of LTA and FAU(X) are obtained. Large single crystals of MOR, MFI and BET are prepared using the ‘two-silicon source’ technique. In the presence of fluoride, a large number of single crystals including silicalite-I, B-, Ti-MFI, AlPO 4 -5, -11, -34. GaPO 4 and InPO are promoted. It is found that a clear homogeneous solution favors the crystallization of large single crystals of AFI. The alcoholic synthesis route has proved to be one of the most effective ways to obtain large single crystals of some zeolites and metal phosphates.

New mineralization agents for the synthesis of MCM-41

Silicate and aluminosilicate MCM-41 molecular sieves have been synthesized in the presence of various new mineralization agents, such as methylamine, dimethylamine, ethylamine and diethylamine. The products were characterized with a series of techniques. XRD, TEM and nitrogen adsorption-desorption measurements suggest that the products possess highly ordered structures. Si-29 NMR results show that the resultant mesophase frameworks are condensed with a higher degree than those of products prepared with NaOH as the mineralization agent. These alkalimetal-free synthesis media offer a simple and effective method for the direct preparation of high quality H-type aluminosilicate MCM-41, as shown by XRD, Al-27 NMR and NH, TPD results. Both the pure silica and the aluminum-containing samples exhibit excellent thermal tin air up to 1373 K) and hydrothermal stability tin hot water of 353 K, 48 h for the former and 72 h for the later). The formation of the high quality MCM-41 material is discussed in terms of a buffer effect of the synthesis media, which is due to the presence of the new mineralization agents. The evidence was obtained by monitoring the pH values of the synthesis

Synthesis of mordenite single crystals using two silica sources

Abstract Starting with the batch composition 1 Al 2 O 3 :85 SiO 2 :19 Na 2 O:575 H 2 O, a study was made to determine the effect of various additives and other modifications of the starting composition on the growth of larger mordenite crystals in this system. It was found that synthesis of larger mordenite single crystals requires the use of two silica sources, the addition of an appropriate salt, and higher basicity. Thermogravimetric analysis showed two ranges of weight loss which might be concerned with diffusional restrictions because of the large dimensions of mordenite crystals. MAS n.m.r. indicated that the as-synthesized mordenite should be small port mordenite, and there is no octahedral aluminum in the framework of the products. Results of the dispro-portionation of β-methylnaphthalene over different sizes of mordenite crystals show that the shape selectivity observed in these reactions might be related to diffusional restrictions inside the channels of mordenite.

Incorporation of luminescent tris(bipyridine)ruthenium(II) complex in mesoporous silica spheres and their spectroscopic and oxygen-sensing properties

Abstract Tris(bipyridine)ruthenium(II) ([Ru(bpy) 3 ] 2+ ) has been assembled into mesoporous SiO 2 spheres. The assembly material, [Ru(bpy) 3 ] 2+ /sphere, was investigated by UV–VIS adsorption and emission spectra. The emission spectra shown that the wavelength of maximum intensity ( λ max ) of [Ru(bpy) 3 ] 2+ increases with the increasing of [Ru(bpy) 3 ] 2+ loading level. The luminescence of [Ru(bpy) 3 ] 2+ /sphere is easily quenched by oxygen. The oxygen-sensing property of [Ru(bpy) 3 ] 2+ /sphere was investigated. It was demonstrated that [Ru(bpy) 3 ] 2+ /sphere can be used to develop oxygen-sensing material.

Preparation by microwave irradiation of nanometre-sized AlPO4-5 molecular sieve

The influence of the synthesis conditions on the crystallization and crystal size of AlPO 4 -5 molecular sieve is investigated in a (TEA) 2 O–Al 2 O 3 –P 2 O 5 –H 2 O system. The initial mixture composition and the crystallization method affect the crystallization and the crystal size of the product. Microwave heating of the synthesis mixture results in the formation of AlPO 4 -5 with nanometre-sized particles.

Synthesis and characterization of a novel aluminophosphate with layer structure

An aluminophosphate with a layer structure has been synthesized hydrothermally. The ratio P/Al = 2 for the framework; its structure consists of Al-centered tetrahedra and P-centered tetrahedra as basic building units to form a two-dimensional layer structure. The protonated ethylenediamine molecules are located in the interlayer space and sustain the framework. The water molecules are located in the space between two layers. Layers are joined together by van der Waals force to form a three-dimensional structure which crystallizes in the space group Pbnb, with a = 8.052(6), b = 8.760(2), c = 17.037(7) {angstrom}, and V = 1201.88 {angstrom}{sup 3}. The crystal structure has been refined to yield values of R = 0.0418, R{sub w} = 0.0447.

Synthesis and structure of a novel microporous crystal AlPO4CJ2

Abstract A novel microporous crystal, AlPO 4 C J 2 , is hydrothermally synthesized. Single crystal X-ray diffraction shows that it is a novel aluminophosphate crystal with an open framework. It crystallizes in space group P 2 1 2 1 2 1 with a = 9.456(3), b = 9.621(5), and c = 9.965(5) A and V = 906.6(7) A 3 . The crystal structure has been refined to R w = 0.045. The framework structure consists of AlO 5 , Al0 5 F, and PO 4 units. The three-dimensional framework constructed by Al, P, O, and F atoms has two kinds of open channels. One is formed by 8- T rings packing along [100], the other is formed by zigzag packing of 8- T rings along [001].

Hydrothermal synthesis and characterization of perovskite-type Ba2SbMO6 (M = In, Y, Nd) oxides

Abstract Perovskite-type Ba 2 SbMO 6 (M=In, Y, Nd) oxides have been synthesized in Ba 2 O–Sb 2 O 5 –M 2 O 3 –K 2 O–H 2 O hydrothermal system. The synthesized Ba 2 SbMO 6 oxide powders were characterized by the techniques such as XRD, IR, SEM, XPS and ICP methods. The results indicated that the Ba/Sb/M ratio is very similar and closing to 2:1:1 in all the products, and the particle sizes of Ba 2 SbMO 6 oxides, where M=In, Y and Nd, are 1–2 μm, 0.5–1 μm and 0.5–2 μm, respectively.