Chemical vapour deposition catalyst preparation

Chemical Vapour Deposition (CVD). - Another example of deposition is the vapour plating of the support with a volatile inorganic or organometaUic compound. The process requires only a moderate vacuum and is currently one of the methods under research in industry as a means of preparing catalysts with a purely surface deposition. 

Binuclear oxo-Fe species in Fe/ZSM-5 catalyst prepared by chemical vapour deposition... 

Figure 1.8a showed a scheme of the CNTs NO2 sensor layout for NO2 detection with limits as low as 10 ppb [108], It was prepared by a radio frequency plasma enhanced chemical vapour deposition (r.f. PECVD) on Si/Si3N4 substrates. The thin film (5 nm) of Ni catalyst was deposited onto Si3N4/Si substrates provided with platinum interdigital electrodes and a back-deposited thin-film platinum heater... 

The CNTs used in the experiments were prepared by chemical vapour deposition (CVD) of propylene gas at 700 °C using Ni as a catalyst. The diameters of raw nanotubes vary from 20 to 50 nm, and lengths vary from 100 to 1 mm. A TEM image of raw CNTs is shown in Figure 6.13. 

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. 

In Takahashi et al. (2005) a suspended MEMS based micro-fuel reformer was designed and manufactured, and the performance of the reformer evaluated. In this study, in-situ chemical vapour deposition (CVD) of the alumina catalyst bed on a membrane was used as the preparation method for better mechanical and thermal isolation of the reaction zone on the membrane. Most of the microfabricated Pd-based MMs are much more efficient than the conventional thicker or large scale devices, as reported by many authors. 

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. 

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