Catalytic chemical vapour

Review on Catalytic Chemical Vapour Deposition (CCVD) Growth of Single Walled Carbon Nanotubes and their Characterization... 

One major issue of the nanotube elaboration processes is to produce nanotubes with controlled dimensions (diameter, length) and without byproducts (catalytic residues, other carbonaceous particles). This is nearly achieved with processes such as catalytic chemical vapour decomposition using supported catalysts. However, the arc discharge method remains the most common one and is perhaps the easiest way to produce the large quantities of nanotubes required for the elaboration of composites (49). The dimensions of... 

Unalan HE, Chhowalla M. Investigation of single-waUed carbon nanotube growth parameters using alcohol catalytic chemical vapour deposition. Nanotechnology 2005 16 2153-63. 

Mukhopadhyay K, Koshio A, Sugai T, Tanaka N, Shinohara H, Konya Z, et al. Bulk production of quasi-ahgned carbon nanotube bundles by the catalytic chemical vapour deposition (CCVD) method. Chem Phys Lett 1999 303 117-24. 

Lu M, Liu W-M, Guo X-Y, Li H-L. Coiled carbon nanotubes growth via reduced-pressure catalytic chemical vapour deposition. Carbon 2004a 42(4) 805-811. 

Since their discovery by Ijima in the early nineties as a byproduct of fullerene synthesis [1], carbon nanotubes have received a growing interest. A huge number of synthesis routes have been proposed, ranging from laser ablation of carbon target, catalytic chemical vapour deposition (CCVD), liquid phase synthesis, plasma methods, and so forth [2]. Also, a large variety of application niches have been identified that render nanotubes a promising material [3]. 

Jourdain V, Bichara C (2013) Current understanding of the growth of carbon nanotubes in catalytic chemical vapour deposition. Carbon 58 2-39... 

Several methods have been reported to deactivate the catalytic activity of the external surfaces of zeolites. Bhat et al. have modified the catalytic behaviour of ZSM-5 by chemical vapour deposition (CVD) of tetraethyl orthosilicate (TEOS).18 The CVD technique does not affect the channel size or acidity of the zeolite but deactivates the external surfaces by coating them with an inert layer of silica. As a result, the shape selectivity of the zeolite is greatly enhanced. 

Chemical vapour deposition (CVD) processes have become a very important group of film-formation methods. Basically CVD is a material synthesis in which constituents of the vapour phase react chemically to form thin solid films as a solid-phase reaction product which condenses on the substrate. The reaction should take place very near to or on the substrate surface (heterogeneous reactions) and not in the gas phase to avoid powdery deposits. Activation of the reaction can be performed by various means such as the application of heat, high-frequency electrical fields, light or X-ray radiation, electric arc, electron bombardment or catalytic action of the substrate surface. A marked influence of the process parameters such as sub-... 

Porous metal membranes are commercially available in stainless steel and some other alloys (e.g.. Inconel, Hastelloy) and they are characterized by a macroporous structure. On the other hand, porous ceramic membranes can be found commercially in various oxides and combination of oxides (e.g., Al203,li02,Zr02, Si02) and pore size families in the mesopore and macropore ranges (e.g., from 1 nm to several microns). Most of the literature studies on three-phase catalytic membrane reactors have been carried out by developing catalytic ceramic membranes. The deposition techniques for the preparation of catalytic ceramic membranes involve methods widely used for the preparation of traditional supported catalysts (Pinna, 1998), and methods specifically developed for the preparation of structured catalysts (Cybulski and Moulijn, 2006). Other methods to introduce a catalytic species on a porous support include the chemical vapour deposition and physical vapour deposition (Daub et al, 2001). The catalyst deposition method has a strong influence on the catalytic membrane reactor performance. 

A new preparation method is described to synthesize porous silicon carbide. It comprises the catalytic conversion of preformed activated carbon (extrudates or granulates) by reacting it with hydrogen and silicon tetrachloride. The influence of crucial convoaion parameters on support properties is discussed for the SiC synthesis in a ftxed bed and fluidized bed chemical vapour deposition reactor. The surface area of the obtained SiC ranges ftiom 30 to 80 m /g. The metal support interaction (MSI) and metal support stability (MSS) of Ni/SiC catalysts are compared with that of conventional catalyst supports by temperature programmed reduction. It is shown that a Ni/SiC catalyst shows a considnable Iowa- MSI than Ni/Si(>2- and Ni/Al203-catalysts. A substantially improved MSS is observed an easily reducible nickel species is retained on the SiC surface after calcination at 1273 K. 

Heterogeneous reaction systems are modelled by detailed chemical kinetics and transport models and numerically simulated for two simple configurations, an cataJytically active wire and disk. As special case for the latter configuration, chemical vapour deposition of diamond is simulated. Elementary reaction mechanisms are applied in the gas phase and on the surface, and the coupling of the catalytic surface with the surrounding reactive fiow is accounted for by a detailed transport model. 

The catalytic activity is a manifestation of the chemical lability of metal alkoxides especially their reactivity with hydroxyl-containing molecules. The volatility and solubility in common organic solvents of certain metal alkoxides has made them attractive precursors for depositing pure metal oxides by chemical vapour deposition (MOCVD) or by the sol-gel process. The requirement for heterometal oxides as useful materials in the electronics industry has stimulated research in this field in recent years and led to renewed interest in the preparation and characterization of alkoxides of some of the p-block elements which had previously been neglected. In particular, the discovery of the high Tc copper oxide-based superconducting heterometal oxides has made a tremendous impact on this field. 

An integrated process, which combines catalytic EniChem TS-1, catalyzed direct ammoximation of cyclohexanone and Sumitomo Chemical vapour-phase Beckmann rearrangement, both exploiting MFI based zeolite-like materials, is now industrially used for greener caprolactam production from cyclohexanone without co-producing any ammonium sulfate (Fig. 15.2). ... 

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