Ceramic Catalyst Carriers

The results of the characterization of extrusion behaviour are explained using ceramic catalyst carrier compounds based on y-aluminium oxide. The solid phase of all compounds was the same, consisting of y-aluminium oxide and pseudobohmite in a ratio of 2 1. 

Fig. 6. Catalyst inhibition mechanisms where ( ) are active catalyst sites the catalyst carrier and the catalytic support (a) masking of catalyst (b) poisoning of catalyst (c) thermal aging of catalyst and (d) attrition of ceramic oxide metal substrate monolith system, which causes the loss of active catalytic material resulting in less catalyst in the reactor unit and eventual loss in performance.

Alumina produced by the Bayer process is precipitated and then calcined [Krawczyk, Ceramic Forum International, 67(7-8), 342-8 (1990)]. Aggregates are typically 20 to 70 [Lm, and have to be reduced. The standard product is typically made in continuous dry ball or vibra-toiy mills to give a product d o size of 3-7 [Lm, 98 percent finer than 45 [Lm. The mills are lined with wear-resistant alumina blocks, and balls or cylinders are used with an alumina content of 80-92 percent. The products containing up to 96 percent AI9O3 are used for bricks, kiln furniture, grinding balls and liners, high voltage insulators, catalyst carriers, etc. 

Some of these modules were fabricated in solid ceramic materials allowing chemical reactions with highly corrosive reactants or products or even at very high temperatures. Also special ceramic foams were developed which can be used as a catalyst carrier. 

As will be shown later, some ceramic membranes have been used to immobilize some biocatalysts such as enzymes for increasing the reaction rate of bioreactions. Membrane pores when mostly used as catalyst carriers are advantageous over the conventional catalyst carriers in the pellet or bead form in having less mass transfer resistance and more efficient contact of the reactant(s) with the catalysL In a strict sense, the membrane material when used in this mode is not a membrane which is defined as a permselective medium. 

Ceramic monoliths can be manufactured either by extrusion [6-31 ] or by corrugation [32-44], the former being the technique mainly used. By extrusion, ceramic monoliths of various materials can be produced, though cordierite or mullite monoliths are most used, especially as catalyst carriers in exhaust gas treatment [6-31]. 

Use Raw material for special ceramic compositions catalyst carrier. 

Use Filtration clarifying and decolorizing insulation absorbent mild abrasive drilling-mud thickener extender in paints, rubber, and plastic products ceramics paper coating anticaking agent in fertilizers asphalt compositions chromatography refractories acid-proof liners catalyst carrier. 

Use Filler and coatings for paper and rubber, refractories, ceramics, cements, fertilizers, chemicals (especially aluminum sulfate), catalyst carrier, anticaking preparations, cosmetics, insecticides, paint, source of alumina, adsorbent for clarification of liquids, electrical insulators. 

Use Rubber filler ceramics, glass, refractories absorbent for crude oil spills manufacture of permanently dry resins and resinous compositions paints, varnishes, and paper (filler) animal and vegetable oils (bleaching agent) odor absorbent filter medium catalyst and catalyst carrier anticaking agent in foods. 

The catalysts tested were supplied by Degussa AG and consisted of a ceramic honeycomb carrier with 400 cells/in. The washcoat loading was 110 g f with the composition (wt %) as denoted in Table 1. The catalysts had a length of 15 cm and a diameter of 2.5 cm. To reduce the... 

Beshay et al. reported conditions for the short-term continuous cultivation of D. discoideum cells on porous supports (SIRAN beads) in HL-5C medium ]108]. D. discoideum cells actively colonized the porous carrier (Fig. 5.5), after which the colonized beads can be freely suspended in medium. Gell densities of free amoebae remained at about 10 per mL for most of the cultivation time, whereas the cell density on the SIRAN beads reached up to 10 per mL and remained constant for at least 16 days of fermentation [108, 109]. By using broken pumice or CeramTec (a ceramic catalyst support), the immobilized cells reach... 

Other powder metal or ceramic parts may have to become filters or catalyst carriers requiring large numbers of penetrating pores (see Section 5.3.2), uniform structure, and high strength. In those cases sintering of preforms is carried out such that no densification occurs and porosity remains unchanged. 

Dr. Rodney Delano Bagley of Messrs. Coming Glass Works applies for a patent to extmde honeycombs (carriers for catalyst converters) Patents are granted in Japan for the extrusion of ceramic catalyst converters... 

Typical ceramic materials produced on a co-rotating twin screw extruder are for example catalyst carriers. They are commonly shaped into granules for use as bulk material in reactors in the chemical industry or into honeycombs for catalytic converters in automobiles exhaust systems (Fig. 12). After extrusion, the catalyst carriers are cut oversized in the lineal direction, dried and then cut to the proper length. Afterwards the binder is removed and the carriers are calcinated or sintered. Finally, to provide them with catalytic properties, they are impregnated with an active film in a bath [Fri76]. 

Therefore, demands arising from different ceramic masses and binder systems can be individually addressed. Two examples for catalyst carriers - honeycombs and granulated bulk material - give an impression of the variety of machine set ups but also of the feeding and discharge systems possible. 

Ciambelli P, Palma V, Palo E (2008) Comparison of ceramic honeycomb monolith and foam as Ni catalyst carrier for methane autothermal reforming. Catal Today. Catal Today 155 92-100... 

Kraushaar-Czarnetzki, B. (2003) Ceramic foam monoliths as catalyst carriers. 1. Adjustment and description of the morphology. Ind. Eng. Chem. Res., 42 (9), 1863-1869. 

Owing to the low surface area of the monoliths, a catalyst carrier such as alumina or ceria is deposited onto them usually by wash coating [11]. The ceramic construction material is well compatible with these carriers, does not migrate into the catalyst coatings, and the precious active metal species of the catalysts do not migrate into the monoUth bodies [1]. The most widely used construction material for ceramic monolith carriers is cordierite [9] with alumina being an alternative. 

Once the surface has been pretreated, the coating slurry needs to be prepared. The most common method is to prepare a dispersion of finished catalyst, sometimes including gelation steps. Ceramic monoliths are usually wash-coated by these means. The catalyst carrier or the catalyst itself [100] is mixed with a binder such as... 

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