A modified seeded growth procedure, which allowed us to prepare the first functional b‐oriented siliceous ZSM‐5 membrane (Z. Lai et al., Science, 2003, 300, 456), is described and discussed in detail. The procedure involves growing a b‐oriented ZSM‐5 seed monolayer into a dense b‐oriented membrane. Preservation of the orientation is achieved by enhancing the growth rate of siliceous ZSM‐5 crystals along the b‐axis using trimer‐TPAOH (bis‐N,N‐(tripropylammoniumhexamethylene) di‐N,N‐propylammonium trihydroxide) as the structure‐directing agent (SDA). Under similar synthesis conditions but using monomer‐TPAOH (tetrapropylammonium hydroxide) as the SDA for the secondary growth of the b‐oriented seed layer, two other films with mixed grain orientations, namely b&a‐ or b&a&h0h/c‐oriented ZSM‐5 membranes were obtained depending on temperature of the secondary growth. Membrane microstructures were characterized by X‐ray diffraction, pole figure analysis, scanning electron microscopy, fluorescent confocal optical microscopy, electron probe microanalysis, and X‐ray photoelectron spectroscopy. The separation performance of the three types of membranes was tested by using a mixture of xylene isomers. Significant improvement in both permeance and separation factor is achieved by the b‐oriented siliceous ZSM‐5 membrane compared to the other two types of membranes described here or other reported ZSM‐5 membranes in the literature. The permeation results indicate that the membrane performance depends strongly on membrane microstructure.

Organosilicon carbodiimides have been successfully applied as single-source precursor compounds for the synthesis of novel ternary Si-, C-, and N-containing solid phases. Their thermally induced decomposition gives either amorphous silicon carbonitrides or polycrystalline silicon nitride and silicon carbide mixtures, materials that are presently of technological interest for their exceptional hardness, strength, toughness, and high temperature resistance even in corrosive environments. This review is concerned with the synthesis, characterization, and thermal stability of element carbodiimides. The main part of this paper is focused on polymeric silicon-based carbodiimides obtained by the reaction of chloro(organo)silanes with bis(trimethylsilyl)carbodiimide. In the case of RSiCl 3 , novel poly(silylcarbodiimide) gels are formed. Starting from silicon tetrachloride, new crystalline SiCN phases (namely, SiC 2 N 4 and Si 2 CN 4 ), have been isolated. Their crystal structures as well as their thermal behavior in the range between room temperature and 1600 °C are discussed. Moreover, preliminary results on the synthesis of germanium-and boron-containing carbodiimides are reported. It is also shown that carbon-based carbodiimides can be obtained by the reaction of cyanuric halides with bis(trimethylsilyl)carbodiimide. These materials are investigated as precursors for the synthesis of new carbon nitrides with high hardness.

In this article we present the synthesis of three-dimensionally ordered ternary BC 2 N crystals produced under hightemperature and high-pressure conditions. Unit cell dimensions are a ‫؍‬ 2.4820 ؎ 0.0007 Å and c ‫؍‬ 6.620 ؎ 0.003 Å. The composition BC 2 N is derived from Vegard's law and quantitative electron energy loss spectroscopy. The ordered arrangement of atoms in the unit cell is discussed.

A fluid catalytic cracking (FCC) catalyst is used in refineries to upgrade crude oil into valuable products. To fulfill the increasing demand for propylene, additives are used to boost propylene production. The hydrothermal conditions in a FCC unit gradually deactivate the Y-zeolite in the catalyst and the ZSM-5 zeolite in the additive by a dealumination of the framework structure. By powder X-ray diffraction, the change in the lattice parameter of the Y-zeolite over time is used to monitor the deactivation process. In this paper, we have shown that with a combination of powder X-ray diffraction and Rietveld analysis we can monitor the deactivation of ZSM-5. The lattice parameters measured for ZSM-5 are used to calculate the unit cell volume, which shows a good correlation with physical properties, such as total acidity and surface area, and the catalytic properties of ZSM-5 based additives. The data demonstrate that the technology can be applied to both laboratory and field deactivated ZSM-5 based additives.

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