Aluminium catalyst support

Daumengrofes Labor aus Aluminium-Folie, Blick durch die Wirtschafi, June 1997 Heterogeneous gas-phase micro reactor micro-fabrication of this device anodic oxidation of aluminum to porous catalyst support vision of complete small laboratory numbering-up development of new silicon device [225]. 

When controlled nitridation of surface layers is required, as for example in the modification of the chemical properties of the surface of a support, the atomic layer deposition (ALD) technique can be applied." This technique is based upon repeated separate saturating reactions of at least two different reactants with the surface, which leads to the controlled build-up of thin films via reaction of the second component with the chemisorbed residues of the first reactant. Aluminium nitride surfaces have been prepared on both alumina and silica supports by this method wherein reaction cycles of trimethylaluminium and ammonia have been performed with the respective supports, retaining their high surface areas." This method has been applied to the modification of the support composition for chromium catalysts supported on alumina." ... 

Our thanks are due to Schweizerische Aluminium AG (Alusuisse) for providing experimental facilities and partial financial support during this project. He are also grateful to I.C.I. Petrochemicals and Plastics Division for providing some of the catalyst support packings. 

In reporting the results of a spectroscopic study of aluminium phosphate in 1971, Peri drew attention to the isostructural nature of A1P04 and Si02 and the likely value of A1P04 as an adsorbent and catalyst support. Stable high-area A1P04 gels could readily be prepared in 1971, but at that time there was no indication in the open or patent literature that zeolitic forms of aluminophosphate could be synthesized. 

The Smuda process also uses new cracking catalysts based on cobalt resinates which are cobalt salts of resin acids (mainly abietic acid) such as cobalt abietate and cobalt linoleate (these are commonly referred to as driers in the coatings industry) and preferably with admixtures of heavy metal silicates. Smuda has also explored the use of manganese resinate deposited on an aluminium oxide support to maximize active surface area [23]. 

Other chromium catalysts for ethylene polymerization employ chromo-cene [246] and bis(triphenylsilyl) chromate [247] deposited on silica-alumina. The catalyst support is essential for high activity at moderate ethylene pressures (200—600 p.s.i.). The former catalyst is activated further by organo-aluminium compounds. Polymerization rates are proportional to ethylene pressure and molecular weight is lowered by raising the temperature or with hydrogen (0.1—0.5 mole fraction) in the monomer feed wide molecular weight distributions were observed. 

The active structure in the Al-Sb-V-0 system is a bulk phase, which is directly formed in the catalyst synthesis. It is a trirutile-like phase Ali.xSbVx04 (0 < x < 0.5), and the presence in the synthesis of an excess of aluminium is critical for its formation. Thus, the aluminium is not only a catalyst support in the form of 8-AI2O3, but it is also an element in the active phase. The Sb V ratio in the trirutile usually falls in the range 2-5 (cf. Fig. 6). 

Sol-gel chemistry offers flexible methods for the preparation of porous metal oxides such as the transition aluminas used as catalyst supports. The physical properties of sol-gel materials depend on the nature of the reactants, the rate of mixing and the conditions of drying. High surface area aluminas have been prepared from various alkoxide and salt solutions and their textures have been examined extensively. The interest in the use of these chemically prepared materials is largely for catalyst and absorbent applications [1]. The first user of alkoxide precursor was Teichner who prepared pure aluminas by the water vapour action on aluminimn methoxide [2] and reported materials with surface area of 200 m /g. Harris and Sing [3] reported gels prepared from aluminium isopropoxide with water and... 

Extensive recycling of organic and HF is required and catalyst lifetime is a problem. However, subsequent work by Dupont [8] over a variety of metals on an aluminium fluoride support gave extended catalyst lifetimes. 

Such reactions have also been carried out successfully using aluminium chloride supported on MCM-41, prepared by the reaction of the support with AICI3. The activity of this Lewis acid is comparable to that of AICI3 itself, and its selectivity towards monoalkylation is better, because the reaction takes place within the narrow pore structure of the catalyst. 

A quick check of extrusion properties of ceramic compounds can be made using a simplified capillary-rheometric method. A one-point or two-point determination can, for example, make it possible to quickly select promising compound compositions. The accelerated test method was used in the development of a compound from aluminium oxide for making catalyst supports. Two criteria were here taken into account ... 

The thermal decomposition of gibbsite was chosen to illustrate the application of modem instrumental and computing techniques to preparative controlled reaction rate methods for making reproducible catalysts or catalyst supports of high surface area at atmospheric pressure. Gibbsite is one form of aluminium trihydroxide, Al(OH)3, the other being the mineral bayerite [6]. The thermal decomposition of gibbsite is complex, and is influenced both by crystallite size and water vapour pressure. Two processes, which may overly under certain conditions, have been identified [7] ... 

Aluminium substrates are frequently pre-treated by anodic oxidation to generate a porous surface, which may serve as the catalyst support itself or as an adhesion layer for a catalyst support [122]. The surface area of the obtained alumina layer may reach 25 m g , with a thickness of 70 pm or higher. Assembled alumina micro-channel reactors can also be oxidised. The layer generated by anodic oxidation of aluminium and aluminium alloys is amorphous hydrated alumina. It is believed to contain boehmite, pseudoboehmite and physically adsorbed water [123]. It has the morphology of a packed array of hexagonal cells, each containing a pore in the centre. Thus the layer has a highly ordered porous structure and uniform thickness, when an... 

Although the yield of propene does not exceed about 12% at best, the performance of the catalysts is remarkable insofar as, for the first time, the yield of propene is higher than that of COx, with the 10% vanadium catalyst. The good performance of the aluminium fluoride-supported VOx catalysts is due to the nature of the support and not a result of the sol-gel preparation route as follows from a direct comparison of VOx/aluminium fluoride ( VAIF ) and VOx/aluminium oxide ( VAIO ) catalysts prepared similarly via the sol-gel route. 

Aluminium levels of individual component foils of a model catalyst support fabricated from Aluchrom YHfAl following aiuminising (Diffusion Alloys Ltd). 

The standard catalyst, denoted as CHsONa/MSU-y, was prepared by wet impregnation with a methanol solution of CHsONa on a mesoporous aluminium oxide support. After impregnation, the wet material was dried in air at 60°C, compressed and sieved to form pellets with a diameter ranging from 0.5 to 1 nun. Before use in transesterification of rapesed oil with methanol, in situ activation of the catalysts was done at 200°C imder nitrogen for 3 and 6 h, respectively. 

Abstract Membrane reactors with a catalyst bed are designed to be used in various reactions, such as hydrogenation, dehydrogenation, oxidation and reforming reactions. The catalyst can be introduced into the reactor as a bed in several ways in the form, for example, of pellets, extrudates or tablets or it can be incorporated in the reactor as a catalytic membrane wall. However, in many cases, the studies concentrate on the membrane itself, the development of catalysts is ignored, and commercial catalysts are used in the experiments. Most of the catalysts tested are aluminium oxide (alumina, AI2O3) based, as alumina is a mature support and already well proven in convectional reactors. However, some new catalyst materials such as carbon nanotubes (CNTs), carbon black, gels and anodic aluminium oxide (AAO) are developed as innovative catalyst supports and catalysts, since there is also a need for new catalysts for membrane reactors. 

The product distribution in the reaction of benzene with dodecene was determined for a number of catalysts (Table 5.1-4). As can be seen, the reaction with the zeolite H-Beta gave predominantly the 2-phenyldodecane, whereas the reaction in the pure ionic liquid gave a mixture of isomers, with selectivity similar to that of aluminium chloride. The two supported ionic liquid reactions (H-Beta / IL and T 350 / IL) again gave product distributions similar to aluminium(III) chloride (T350 is a silica support made by Degussa). 

The ability of iron(III) chloride genuinely to catalyze Friedel-Crafts acylation reactions has also been recognized by Holderich and co-workers [97]. By immobilizing the ionic liquid [BMIM]Cl/FeCl3 on a solid support, Holderich was able to acetylate mesitylene, anisole, and m-xylene with acetyl chloride in excellent yield. The performance of the iron-based ionic liquid was then compared with that of the corresponding chlorostannate(II) and chloroaluminate(III) ionic liquids. The results are given in Scheme 5.1-67 and Table 5.1-5. As can be seen, the iron catalyst gave superior results to the aluminium- or tin-based catalysts. The reactions were also carried out in the gas phase at between 200 and 300 °C. The acetylation reac-... 

Catalysts can be metals, oxides, sulfides, carbides, nitrides, acids, salts, virtually any type of material. Solid catalysts also come in a multitude of forms and can be loose particles, or small particles on a support. The support can be a porous powder, such as aluminium oxide particles, or a large monolithic structure, such as the ceramics used in the exhaust systems of cars. Clays and zeolites can also be solid catalysts. 

Owing to its excellent thermal and mechanical stability and its rich chemistry, alumina is the most widely used support in catalysis. Although aluminium oxide exists in various structures, only three phases are of interest, namely the nonporous, crys-tallographically ordered a-Al203, and the porous amorphous t]- and y-Al203. The latter is also used as a catalyst by itself, for example in the production of elemental sulfur from H2S (the Claus process), the alkylation of phenol or the dehydration of formic acid. 

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