Aluminum Phosphate Supported Metals

The neutral molecular sieve, aluminum phosphate (ALPO, Chapter 10) can also serve as a shape selective support for metal catalysts. These catalysts are normally prepared by the incipient wetness process followed by appropriate drying and reduction procedures. Fig. 13.19 illustrates the selectivity observed using a Ni/ALPO catalyst to hydrogenate a mixture of styrene and a methyl styrene (Eqn. 13.13). The rates of hydrogenation of cyclic alkenes over a Rh/ALPO catalyst decreased in the order cyclopentene cyclohexene cycloheptene cyclooctene but no selectivity was observed in a competitive hydrogenation of a mixture of cyclohexene and cyclooctene. 75 

As described in Chapter 10, clays are laminar aluminosilicates. While these materials are most commonly used as solid acids their ion exchange capability provides a means of incorporating catalytically active metals into the laminar 

The use of pillared clays as metal supports has also been reported. The more defined interlamelar spacing available with these supports should give a more predictable shape selectivity to the resulting supported metal catalysts. Further, since the pillars prevent the collapse of the layers on drying and further heating, the pillared clay supported metals salts can be calcined and reduced under conditions that can give the best metal dispersion without any concern for a change in the structure of the support.  

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Title Aluminum Phosphate-Supported Group VI Metal Amide Catalysts for Oligomerization of Ethylene... 

Although palladium occupies the dominant position in semi-hydrogenation catalysts, it is by no means the only metal suitable for formulation into a viable catalyst. Mention has already been made of the nickel boride alternatives, with or without copper promotion, for example. Other examples include the skeletal catalyst Raney nickel [69], alumina-supported nickel [70], and aluminum phosphate-supported nickel [71] (Eqs 21 and 22) ... 

Our research on supported transition-metal phosphides started with the preparation of nickel phosphides supported on an amorphous Si02 carrier. Si02 was preferred to AI2O3 as it interacts to a lesser extent with phosphates, which are known to form aluminum phosphates in the presence of AI2O3 [21]. The latter was already used as a support for MoP [22], but the authors had to introduce high loadings of molydenum and phosphorus... 

Aluminum phosphates are the most commonly used phosphates for polymerization catalyst supports because they can be made with the high porosity that is necessary for fragmentation. However, many other metal phosphates are also known and are used in other areas of catalysis. These materials are often quite acidic and can also serve as supports for chromium oxide. 

Correlations between concentrations of dissolved metals (iron and/or aluminum) and of either DOM or organic acids in infiltrating waters suggest that DOM, or some component of DOM, facilitates metal solubilization and translocation in soils (14). The role of DOM in metal mobilization is also supported by the occurrence of organically complexed metals in soil solutions (3, 15, 16). Precipitation and transformations of soil minerals can be inhibited by DOM, which tends to stabilize metastable phases [such as amorphous aluminum hydroxide and pseudoboehmite (17), ferrihydrite (18), and octacal-cium phosphate (19)] and to prevent formation of more crystalline phases. 

The following metal compounds are used for the preparation of the catalysts oxides, metal carbonyls, halides, alkyl and allyl complexes, as well as molybdenum, tungsten, and rhenium sulfides. Oxides of iridium, osmium, ruthenium, rhodium, niobium, tantalum, lanthanum, tellurium, and tin are effective promoters, although their catalytic activity is considerably lower. Oxides of aluminum, silicon, titanium, manganese, zirconium as well as silicates and phosphates of these elements are utilized as supports. Also, mixtures of oxides are used. The best supports are those of alumina oxide and silica. 

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