Impregnation titania-supported catalyst preparation

Santos J, Phillips J, Dumesic J (1983) Metal support interactions between iron and titania for catalysts prepared by thermal-decomposition of iron pentacarbonyl and by impregnation. J Catal 84 147... 

Fig. 3 Results for the photocatalytic reduction of nitrate in the presence of 0.04 M HCOOH as hole scavenger over titania and Ag/Ti02 catalysts prepared by impregnation (IMP) or photodeposition (Photo) and comparing use of Degussa P25 (49 m g ) with Hombikat UV 100 (250 m g ) as supports. ...

The pH of the solution can be critical in the impregnation process. In the preparation of Rh/Ti02 catalysts by impregnating titania with aqueous solutions of rhodium chloride it was found that at low pH the interaction between the salt and the support surface takes place in several steps. Initially the oxide particles become more positively charged and, thus, adsorb the anionic species such as RhCl4 . After adsorption, these anions are more firmly anchored to the support by the displacement of one or more chloro ligands by OH groups on the titania... 

Supported Palladium. - For catalysts prepared by impregnation with PdQ2 on silica, titania, and alumina supports and reduced (673 K), the width of the Pd 3c 5/2 lines in the photoelectron spectra was greater than the value for unsupported palladium and decreased in the order... 

Most of the silver catalysts used in chemical industry and research are prepared via conventional techniques using preformed microporous or mesoporous inorganic support materials. Examples are the preparation of 5 wt.% Ag/Si02 by support impregnation with silver nitrate or a titania-based catalyst on which silver was deposited by treatment with AgN03 and Na2C03. ... 

In this work, we will first study the stability of conventional CoMo and NiMo impregnating solutions. NiMo and CoMo oxidic precursors have been prepared by incipient wetness impregnation of y alumina and titania supports. They will be characterized at each step of the preparation by Raman spectroscopy. Characterization results will be discussed by reference to the chemistry of the impregnating solution which will allow us to explain the differences between CoMo and NiMo based catalysts. 

Titania-supported vanadia catalysts have been widely used in the selective catalytic reduction (SCR) of nitric oxide by ammonia (1, 2). In an attempt to improve the catalytic performance, many researchers in recent years have used different preparation methods to examine the structure-activity relationship in this system. For example, Ozkan et al (3) used different temperature-programmed methods to obtain vanadia particles exposing different crystal planes to study the effect of crystal morphology. Nickl et al (4) deposited vanadia on titania by the vapor deposition of vanadyl alkoxide instead of the conventional impregnation technique. Other workers have focused on the synthesis of titania by alternative methods in attempts to increase the surface area or improve its porosity. Ciambelli et al (5) used laser-activated pyrolysis to produce non-porous titania powders in the anatase phase with high specific surface area and uniform particle size. Solar et al have stabilized titania by depositing it onto silica (6). In fact, the new SCR catalyst developed by W. R. Grace Co.-Conn., SYNOX , is based on a titania/silica support (7). 

No examples or recipes of catalysts prepared using commercially available pre-shaped titania or zirconia supports have been found in literature. Therefore, the result of the use of preparation procedures, such as impregnation using chelating compounds, will be of interest as well. 

Many examples can be found in the literature on this point. The reducibility of vanadia catalysts has catalytic implications for selective oxidation reactions where they found real use. The support nature and the preparation method affect the reducibility of the vanadia phase. In Ref. [19] pure titania or bilayered titania/silica supports were chosen and concerning the vanadia deposition method, impregnation and atomic layer deposition procedures were performed. The reducibility of vanadia improved with increasing titania loading as shown by the calculated AOS. The lowest AOS were associated to vanadia on pure titania supports (Uox.av = 3.5) while vanadia on titania-silica supports achieved at maximum nox.av of 3.7-3.S. AOS of vanadium after reduction was independent of the preparation method. 

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