Metal mesoporous aluminas

Mesoporous alumina membranes ( anodic aluminium oxide , or AAO) are prepared by anodic oxidation of aluminium metal [1,2]. The cylindrical pores, perpendicular to the membrane surface, form hexagonal arrays of straight non-intersecting channels with pore densities up to lO Vcm. Their diameters are controllable within the range 5 - 100 nm as a linear function of anodisation voltage. These membranes are used as molecular sieves, and have also found application as templates for metallic nanowires [3,4,5,6], metal elusters and colloids [7,8], and carbon nanotubes [9,10]. 

Mesoporous aluminas are hypothesized as efficient supports in terms of catalysis for anchoring metal nanoparticles. They offer higher stabihty and dispersion of the nanoparticles apart from facilitating easy diffusion of reactants and product... 

Mesoporous oxides from elements other than sihca have been reported as early as 1994. Cieslaetal. [169] found that metals such as Sb, Fe, Zn, Pb,W, and Mo also form mesoporous oxides. However, many of the mesophases obtained were lamellar and were not porous after template removal (calcination). Antonelli and Ying reported the transformation of titanium, niobium, and tantalum alkoxides into stable mesophases [170]. Subsequently, mesoporous oxides based on zirconium, hafnium, and manganese have been synthesized (for a recent review on these materials see [171]). Bagshaw and Pinnavaia [172] prepared mesoporous alumina with worm-like pores and a specific surface area of more than 400 m g . Mesoporous alumina with surface areas above 700 m g have been reported by Vaudry et al. [173]. 

Alkali metal supported on mesoporous alumina as basic catalysts for fatty acid methyl esters preparation... 

The contribution deals with the catalytic performance of V-, Co-, and Ni-based microporous (MFI), mesoporous (HMS) and alumina catalysts in ODH of ethane. Representative catalysts contained between 2.9 and 3.9 wt.% of metal. Ni-, V- and Co-A1203, and V- and Ni-HMS were effective catalysts in ODH of ethane. However, Ni-A1203 had the best selectivity-conversion behavior. The most favorable set up corresponded to 46 % in the ethane conversion, 30 % in the ethene yield 30 %, 65 % in the selectivity to ethene, and 0.91 g(C2=).gca, 1.h 1 in the ethene productivity for Ni-A1203. The activity was stable for 6 hours time-on-stream. 

Ordered mesoporous materials of compositions other than silica or silica-alumina are also accessible. Employing the micelle templating route, several oxidic mesostructures have been made. Unfortunately, the pores of many such materials collapse upon template removal by calcination. The oxides in the pore walls are often not very well condensed or suffer from reciystallization of the oxides. In some cases, even changes of the oxidation state of the metals may play a role. Stabilization of the pore walls in post-synthesis results in a material that is rather stable toward calcination. By post-synthetic treatment with phosphoric acid, stable alumina, titania, and zirconia mesophases were obtained (see [27] and references therein). The phosphoric acid results in further condensation of the pore walls and the materials can be calcined with preservation of the pore system. Not only mesoporous oxidic materials but also phosphates, sulfides, and selenides can be obtained by surfactant templating. These materials have pore systems similar to OMS materials. 

Up to now, a variety of non-zeolite/polymer mixed-matrix membranes have been developed comprising either nonporous or porous non-zeolitic materials as the dispersed phase in the continuous polymer phase. For example, non-porous and porous silica nanoparticles, alumina, activated carbon, poly(ethylene glycol) impregnated activated carbon, carbon molecular sieves, Ti02 nanoparticles, layered materials, metal-organic frameworks and mesoporous molecular sieves have been studied as the dispersed non-zeolitic materials in the mixed-matrix membranes in the literature [23-35]. This chapter does not focus on these non-zeoUte/polymer mixed-matrix membranes. Instead we describe recent progress in molecular sieve/ polymer mixed-matrix membranes, as much of the research conducted to date on mixed-matrix membranes has focused on the combination of a dispersed zeolite phase with an easily processed continuous polymer matrix. The molecular sieve/ polymer mixed-matrix membranes covered in this chapter include zeolite/polymer and non-zeolitic molecular sieve/polymer mixed-matrix membranes, such as alu-minophosphate molecular sieve (AlPO)/polymer and silicoaluminophosphate molecular sieve (SAPO)/polymer mixed-matrix membranes. 

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... 

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