Titania-supported catalysts impregnation

It is interesting to note also that the mixed oxide supported catalysts increase their activity with reduction temperature, although the impregnated sample performs better. In all cases ethylene selectivity was lower for alumina-supported sample and higher for titania-supported catalyst, and after an initial period the selectivity remained constant. 

The deactivation constant, obtained by fitting the data to a first order law equation (8), decreases with the reduction temperature for all cases, and is especially low for the impregnated alumina-titania catalyst. These results suggest the formation of carbon deposits and deactivation of catalysts occurs due to the metal activity, The contribution of the acid sites to deactivation seems to be negligible, despite the fact that alumina-titania supports present higher acidity than alumina or titania single oxides (9). 

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... 

Figure 122 shows the results of three series of two-step activations, each of which included one of these chemical dehydroxylation methods. Silica-titania (2.5 wt% Ti) was calcined at 871 °C in air, CO, or CS2. Each support was impregnated with 1 wt% Cr as dicumenechromium(O) in hexane. Then samples were subjected to a second calcination in dry air at lower temperatures ranging from 160 to 871 °C. These catalysts were tested at 107 °C for polymerization activity and the resultant polymer was recovered and analyzed. 

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. 

Varying acidic properties were obtained by changing the impregnation procedure and the phase composition of the titania support. The classification of catalysts in strong or weak acidity was done by pH... 

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). 

Wachowski et al. [13] studied Co-Mo sulphides supported on alumina-modified with La203 for the WGS reaction. Results reveal that only higher concentrations of La203 increase the WGS activity. After that they studied the effect of support (alumina, titania, zirconia) on the WGS activity of Mo and Mo-Ni catalysts. Mo-impregnated Ti02 catalyst shows much better activity compared to alumina and zirconia supported catalysts. The addition of Ni to... 

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. 

---