Supported on Carrier Materials

Supported catalysts were prepared by Smith [2]. Carrier materials of various shapes were coated with solutions of monomers, which were then polymerized by UV light, creating a surface film. Mechanical stability was poor. Swelling forces led to crumbling of the film, loss of adhesion, and loss of polymer. The ion-exchange capacity was poor because only the outer surface of the carrier is available for polymer attachment. 

Childress evaporated solutions of polymers on the surface of carrier materials ]12]. To avoid removal of the polymer by swelling forces, he heated the polymer above the melting point. This led to a non-porous polymer coating on the outer surface of the carrier. 

Hiramatsu also prepared films on a carrier material [13]. Halogenated polymers containing noble metals were prepared on the carrier surface. These catalysts had no acidic properties they were used in hydrogen peroxide synthesis. 

Bareis et al. and Eiceman impregnated porous powders with polymers and sul-fonated them to get an acidic ion-exchange catalyst [14,15]. The powders were used in chromatographic applications. The resins were non-porous, so pore-forming agents were not used. 

Dromard impregnated porous inorganic carrier materials (4 pm-S mm) with solutions of monomers and polymers [16]. After evaporation of the solvent, films on the carrier surface were obtained. These catalysts can be activated with sulfonic or phosphonic add groups. The catalysts were used for the production of silicones. The preparation procedure seems to be problematic, because during polymeriza- 

---

Tacky-dry—See tack-dry. Tape. A film form of adhesive which may be supported on carrier material. 

Several diphosphine ligands have been applied and the corresponding complexes have been tested for the immobilization (Fig. 2.1.6.3). The activity of different free and immobilized complexes in the enantioselective hydrogenation of dimethyl itaconate and methyl a-acetamidoacrylate was investigated. In blank reactions over pure mesoporous materials no reaction took place. When rhodium supported on carriers was used as catalyst, no enantiomeric excess was observed. 

In this study it was demonstrated that with the aid of solventless ball-milling of catalyst components, dispersions of active components on carrier materials could be achieved, as measured by TPR, XPS and XANES, that are comparable to the dispersions achieved through conventional impregnation techniques of catalyst preparation. Comparable catalytic results are obtained by both preparation methods. Specifically, catalysts supported... 

Zelinsky and Turowa-Pollak141 describe the specific properties of an osmium catalyst. Hydrogenation on osmium catalysts usually occurs at lower temperatures than on platinum, palladium, or nickel catalysts. Osmium asbestos is a very resistant catalyst that can be used for months on end without loss in activity disadvantages are that osmium catalysts that are not supported on carriers must be frequently regenerated and that when the temperature exceeds 150° osmium tends to decompose the material under hydrogenation. 

Pure metallic preparations normally do not have a very high intrinsic activity the total activity ctf a catalyst depends very much on the development of the surface. Lattice imperfections are usually observed only in the presence of impurities (incomplete reaction of starting materials) or in metals supported on carriers. The carriers prevent sintering of metal particles [73] on heat treatment during preparation or use, and in addition they stabilize crystal modifications beyond their normal range of existence. 

Consequently the absolute potential is a material property which can be used to characterize solid electrolyte materials, several of which, as discussed in Chapter 11, are used increasingly in recent years as high surface area catalyst supports. This in turn implies that the Fermi level of dispersed metal catalysts supported on such carriers will be pinned to the Fermi level (or absolute potential) of the carrier (support). As discussed in Chapter 11 this is intimately related to the effect of metal-support interactions, which is of central importance in heterogeneous catalysis. 

It is very seldom that a commercial catalyst consists of only a single chemical compound or element. Often the active constituent is supported on a carrier material that may or may not possess catalytic activity of its own. Enhanced catalytic activity, selectivity, or stability may also be achieved by the addition of other materials referred to as promoters or inhibitors. 

Early workers viewed carriers or catalyst supports as inert substances that provided a means of spreading out an expensive material like platinum or else improved the mechanical strength of an inherently weak material. The primary factors in the early selection of catalyst supports were their physical properties and their cheapness hence pumice, ground brick, charcoal, coke, and similar substances were used. No attention was paid to the possible influence of the support on catalyst behavior differences in behavior were attributed to variations in the distribution of the catalyst itself. 

One should distinguish between true catalyst supports and diluents. A catalyst support (or carrier) is a material on which a thin layer of catalyst is deposited a diluent is an inert material thoroughly mixed with the catalyst to enhance the binding properties of a powdered catalyst or to assist in pelleting or extrusion fabrication procedures. 

Table V shows the results obtained for the carbonylation of dimethyl ether and methyl acetate with molybdenum catalysts supported on various carrier materials. In the case of dimethyl ether carbonylation, molybdenum-activated carbon catalyst gave methyl acetate with an yield of 5.2% which was about one-third of the activity of nickel-activated carbon catalyst. Silica gel- or y-alumina-supported catalyst gave little carbonylated product. Similar results were obtained in the carbonylation of methyl acetate. The carbonylation activity occured only when molybdenum was supported on activated carbon, and it was about half the activity of nickel-activated carbon catalyst.

Besides some conventional supports, a new carrier material, poly-alumazane, was tested. Poly-alumazane, which was recently reported by Chinese researchers8, is a silica carrier, the surface of which is modified by subsequent treatments with aluminum chloride and ammonia, forming an Al-N phase on the silica surface. This coating is able to interact with two-valent noble metal ions (like Pd11) which is found to result -after reduction- in a catalyst with very high dispersion. 

In all of the spectral studies of gases chemisorbed on supported metals, a background spectrum has been recorded prior to the chemisorption of the gas. The spectrum of the chemisorbed gas is then obtained by subtracting out the background by means of an automatic per cent transmission recorder. The background contains bands due to the surface hydroxyls and Si-0 or Al-0 bands of the carrier material. It is necessary that both the... 

Supported nickel catalysts catalyze steam-methane reforming and the concurrent shift reaction. The catalyst contains 15-25 wt% nickel oxide on a mineral carrier. Carrier materials are alumina, aluminosilicates, cement, and magnesia. Before start-up, nickel oxide must be reduced to metallic nickel with hydrogen but also with natural gas or even with the feed gas itself. 

In this study, a novel Monolith alumina structure was of interest as a base (or a carrier) material for Co-Mo-Alumina catalysts. The specific interest centered around assessing the suitability of the catalyst prepared by impregnating the novel alumina support with Co and Mo for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of a relatively high boiling stock. The Monolith catalyst was also tested on a low boiling coal-derived liquid. 

When a substance is supported on a carrier, its chemical reactivity is fundamentally altered Comparing reactions of a nonsupported compound with those of the same compound dispersed on a earner indicates that the kinetics in exactly the same conditions are always altered, and that they may even lead to different products, namely different catalytic materials... 

---