Mesoporous alumina

This category includes a large variety of silica, zirconia, and alumina mesoporous films. Although the inorganic scaffold of such layers does not transport electric current, the pore architecture, which can be also used as a host matrix for incorporation of functional molecules, can alter electron transport to and from the conducting surface, thus influencing electronic properties of the complete system. 

This is a process designed to cover a catalyst support, such as silica, alumina, mesoporous molecular sieves, or other supports with a metallic catalyst, or other catalytically active materials. The process is carried out by contacting the solid support, for a precise time, with a solution containing the active elements, to introduce a solution of the precursor into the pores of the support. During the impregnation process, the support can be completely free of the solvent when the precursor is dissolved. In this... 

Alumina. Mesoporous aluminas with high surface area are of great interest because of their potential nse as catalysts and catalyst supports. The first successful synthesis of mesoporous aluminas was reported by Bagshaw and Pinnavaia through assembly process. Aluminas accessible... 

Sophisticated catalysts, such as ZSM-5 or HZSM-5 [22] and other zeolites are also suggested in numerous papers, e.g. KEY [23], HY and H-mordenite [24], Re-zeolite-based Engelhardt FCC commercial catalyst [25], and steamed commercial zeolite catalyst [26]. These investigations are mainly devoted to fundamental studies and the correlation between feed composition, catalyst properties, process parameters and efficiency connected with prodnct distribution. Iron supported on silica-alumina, mesoporous silica and active carbons serves as the next example of materials applied in the waste plastics cracking [27, 28]. On the other hand, according to some results [29] application of cracking catalysts such as Zn-13X, Fe-5A and CoMo-HY are ineffective in waste plastics cracking. 

Kim et al.32 reported the preparation, characterization, and catalytic performance of a finely dispersed and thermally stable nickel catalyst incorporated into mesopo-rous alumina. Mesoporous alumina catalysts that incorporate Ni (Ni-alumina) with different Ni/Al molar ratios were synthesized by a one-step sol-gel method using lauric acid as a template. The prepared Ni-alumina catalysts showed a relatively high surface area with a narrow pore size distribution after calcination at 700 °C these effects were independent of the Ni/Al molar ratio. The Ni-alumina catalysts were found to be highly active in the POX of methane. The deactivation of catalysts examined in this work was not due to catalyst sintering, but mainly to carbon deposition. 

F. Vaudry, S. Khodabandeh, and M.E. Davis, Synthesis of Pure Alumina Mesoporous Materials. Chem. Mater., 1996, 8, 1451-1464. 

The most simple pore morphologies (Figs. 2.1A and B) are those of more or less straight cylindrical or conical-shaped pores. This type of pore is formed in so-called track etch and in "anopore" membranes. The latter is obtained by anodic oxidation of A1 metal foils and results in porous (amorphous) alumina (mesoporous) membranes. A detailed discussion is given by Burggraaf and Keizer in Ref. [1]. These types of membrane are useful for fundamental trans-... 

Membrane systems with pore diameters in the micropore range (gas separation, nanofiltration) are not yet commercially available but are produced for development and marketing purposes by, e.g., Velterop B.V. (Enschede, Netherlands) and Media and Process Technology Inc. (Pittsburgh, USA). These systems have an a-alumina support combined with multilayered y-alumina (mesoporous) layers and a silica (microporous) separation layer. 

As shown in Table 8.2, the minimum required roughness of the support to obtain crack-free membranes is smaller for Ti02 membranes than for y-alumina (mesoporous) membranes. To obtain microporous silica membranes even more stringent requirements prevail. 

Porous membranes used for reactant feed are typically mesoporous or macro-porous. Two problems arise control of the rate of addition and distribution of reactant B, and back-diffusion of reactant A. To control the uniformity of the distribution of B, we want the membrane to present enough resistance to equalize pressure on the reactant B side, giving a constant transmembrane pressure drop along the tube. This may mean modification of thin y-alumina mesoporous membranes or use of Vycor glass tubes.A higher pressure drop also helps reduce the driving force for back-diffusion, which was exploited in the pneumatic... 

Figure 7-12. Synthesis and thermal pathways followed for the preparation of a -alumina mesoporous membrane by the colloidal sol-gel route.

The research group coordinated by Professor Gabriele Centi prepared a series of tubular catalytic membranes (TCM) and tested in the direct synthesis of H202. " Such TCMs are asymmetric a-alumina mesoporous... 

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