Preparation alumina-supported

Nagai and co-workers prepared alumina-supported niobium nitride from the eVD of NbCls, using a mixture of NH3 and H2 as a nitridation gas at 823 K under reduced pressure (65). NbN thin film of submicrometer thickness on carbon plate was prepared via the RF-sputtering method (RF power of 2.5 W/cm ) with a Nb plate and N2 atmosphere under vacuum chamber (66). A NbN thin film retained the fine particles of 100 nm. 

Fe Mossbauer spectra of the as-prepared alumina-supported PtFe f alloy nanoparticles at room temperature, also including that of the as-prepared fee disordered PtFe alloy nanoparticles and Fe/AbOs. 

Zom et al. prepared well-defined high-surface-area palladium catalysts and prepared alumina-supported palladium nanoparticles in three different oxidation states Pd° (reduction in 1 bar H2 flow at 573 K for 1 h), PdO < 1 (oxidation in 1 bar O2 flow at 673 K for 1 h), and PdO (oxidation in 1 bar O2 flow at 1,073-1,273 K for 1 h) [76], The CO oxidation activities of the three different pretreated supported catalysts and commercial PdO were compared using a mixture of 50 mbar CO, 50 mbar O2, and balance He to 1,000 mbar. Commercial unsupported PdO was basically unreac-tive with the reaction rate at least 4 orders of magnitude smaller than that of... 

By adopting a similar approach, Reddy et alP prepared alumina-supported nanosized ceria-terbia solid solutions by deposition coprecipitation at ambient conditions. The literature reveals several... 

Alkylthiazoles can be oxidized to nitriles in the presence of ammonia and a catalyst. For example, 4-cyanothiazole was prepared from 4-methylthiazole by a one-step vapor-phase process (94) involving reaction with a mixture of air, oxygen, and ammonia at 380 to 460°C. The catalyst was M0O3 and V Oj or M0O3, VjOj, and CoO on an alumina support. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

The sol—gel technique has been used mosdy to prepare alumina membranes. Figure 18 shows a cross section of a composite alumina membrane made by sHp coating successive sols with different particle sizes onto a porous ceramic support. SiUca or titanium membranes could also be made by the same principles. Unsupported titanium dioxide membranes with pore sizes of 5 nm or less have been made by the sol—gel process (57). 

Organochromium Catalysts. Several commercially important catalysts utilize organ ochromium compounds. Some of them are prepared by supporting bis(triphenylsilyl)chromate on siUca or siUca-alumina in a hydrocarbon slurry followed by a treatment with alkyl aluminum compounds (41). Other catalysts are based on bis(cyclopentadienyl)chromium deposited on siUca (42). The reactions between the hydroxyl groups in siUca and the chromium compounds leave various chromium species chemically linked to the siUca surface. The productivity of supported organochromium catalysts is also high, around 8—10 kg PE/g catalyst (800—1000 kg PE/g Cr). 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Polyethylene. Low pressure polymerization of ethylene produced in the Phillips process utilizes a catalyst comprised of 0.5—1.0 wt % chromium (VI) on siUca or siUca-alumina with pore diameter in the range 5—20 nanometers. In a typical catalyst preparation, the support in powder form is impregnated with an aqueous solution of a chromium salt and dried, after which it is heated at 500—600°C in fluid-bed-type operation driven with dry air. The activated catalyst is moisture sensitive and usually is stored under dry nitrogen (85). 

Alumina supported sodium metaperiodate, which can be prepared by soaking the inorganic support with a hot solution of sodium metaperiodate, was also found to be a very convenient reagent for the selective and clean oxidation of sulphides to sulphoxides79. The oxidation reaction may be simply carried out by vigorous stirring of this solid oxidant with the sulphide solution at room temperature. As may be expected for such a procedure, solvent plays an important role in this oxidation and ethanol (95%) was found to be... 

Thiazolines (2,3-dihydrothiazoles) were also prepared under microwave irradiation. Hamelin and coworkers have described the alumina-supported solvent-free synthesis of various 4-iminothiazolines by condensation of disymmetric thioureas and a-chloro ketone (Scheme 10). The experiments... 

Active heterogeneous catalysts have been obtained. Examples include titania-, vanadia-, silica-, and ceria-based catalysts. A survey of catalytic materials prepared in flames can be found in [20]. Recent advances include nanocrystalline Ti02 [24], one-step synthesis of noble metal Ti02 [25], Ru-doped cobalt-zirconia [26], vanadia-titania [27], Rh-Al203 for chemoselective hydrogenations [28], and alumina-supported noble metal particles via high-throughput experimentation [29]. 

Figure 9.13. Preparation of a bifunctional Pt/Al203 catalyst. The alumina support is impregnated with an aqueous solution of hexachloroplatinic acid (H2PtCl6) and HCl.The competitive adsorption between C and...

Suppose you prepared an iron oxide catalyst supported on an alumina support. Your aim is to use the catalyst in the metallic form, but you want to keep the iron particles as small as possible, with a degree of reduction of at least 50%. Hence, you need to know the particle size of the iron oxide in the unreduced catalyst, as well as the size of the iron particles and their degree of reduction in the metallic state. Refer to Chapters 4 and 5 to devise a strategy to obtain this information. (Unfortunately for you, it appears that electron microscopy and X-ray diffraction do not provide useful data on the unreduced catalyst.)... 

Catalysts were normally prepared by double impregnation of the alumina support, first with ammonium paramolybdate solution to give 12 wt% MoO (8% Mo) after 500°C calcination, then with cobalt... 

After the calcination step, experimental data (XRD, 29 i maSNMR) show that a zeolite with the silicalite structure has been formed. 29 i MASNMR indicates for the zeolite material a Si/Al ratio depending on the sample prepared it has been observed that both the natures of the silicon source and of the alumina supports may originate these fluctuations. 

The 3 mm disc was covered by a 3 pm thick polycrystalline nickel foil, then a polycrystalline molybdenum disc was placed on top of the nickel foil. This composite sandwich was placed between two alumina supports and heated for 30 min at 1350°C. The cross-sections used for microanalysis were prepared by cutting with a wire saw in a direction perpendicular to the grain boundary, then mechanically and chemically polished. 

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