Cordierite monolith impregnation

FIGURE 35 SEM image (A) and elemental maps of Al (B) and Pd (C) for a standard silica-coated cordierite monolith impregnated with palladium (705). 

Kim et al. [40] made an attempt to oxidize phenol in water solutions using a monolith reactor. Alumina-washcoated cordierite monoliths (62 celLs/cm ) impregnated with copper... 

Crynes et al. [41] continued the study of Kim et al. [40]. The novel monolithic froth reactor, with a monolithic section 0.42 m long and 5 cm in diameter, was used. Cordierite monoliths with a cell density of 62 cells/cm were stacked, one on top of another, to provide a structure 0.33 m long. The monoliths, washcoated with 7-alumina and impregnated with CuO, were tested at 383-423 K and 0.48-1.65 MPa. The liquid flow rate was varied from 0.4 to 3.5 cm sec", and the gas flow rate ranged from 15.8 to 50 cm sec". Phenol in a concentration of 5000 ppm was typically oxidized with air. The reaction rate versus the liquid flow rate showed a distinct maximum of approximately 2 mol g"t sec" at about 1.7 cm sec", while the dependence of the reaction rate on the gas flow rate was rather weak, with a tendency to decrease as the flow rate increased. 

Ru impregnated y-Al203 catalyst was washcoated on cordierite monolith/ceramic forms and pellets. Among them, the Ru supported on ceramic foams exhibited better performance in the autothermal reforming of ethanol probably due to smaller pore size and higher tortuosity of the support. 

Cordierite monoliths were coated with an alumina washcoat and stabilised at 550°C. Some of the samples were then immersed in either an aqueous solution of cerous or cobalt nitrate, dried and calcined in air at 550°C at which the metal nitrates decomposed into their oxides [11]. The samples were weighed and the procedure was repeated until 40 mg of the metal oxide had been deposited onto the alumina washcoated monolith samples. Pt and Pd were applied by direct impregnation using aqueous solutions of HaPtCla and PdCb followed by diying and calcination in air at 550°C [8]. The Pt and Pd loadings (2.0 and 1.09 mg, respectively) of the catalysts were equal on molar basis. The nominal composition of the eight catalysts prepared are listed in Table 1. 

Catalysts were prepared by impregnation of alumina coated cordierite monoliths. Cylindrical catalyst samples (0 = 30 mm, L = 76 mm) were placed in a down-flow reactor. The reaction mixture contained 3 to 9 components among NO, O2, NO2, HC, CO, CO2, H2O, N2, SO2 in most cases NO concentration was 600 ppm with 3000 ppmC HC with a... 

The catalyst was prepared on a cordierite monolith having 62 cells per cm2, xhe support was coated with a promoted alumina-ceria (6 % Ce02) wash-coat and impregnated with 1.06 g/1 of platinum plus rhodium, with a Pt/Rli mass ratio of 5. After impregnation, the catalyst was calcined for 2 hours at 500°C. Activity measurement... 

Vanadium pentoxide catalysts, similar to those used to remove nitrogen oxides from gas turbine effluent, have also been used to treat the effluents from a nitric acid plant. The catalyst is based on extruded titania, impregnated with vanadium pentoxide and any promoters, or cordierite monoliths covered with a washcoat of the active material. 

Figure 1. Front view of a 400 cpsi honeycomb cordierite monolith (a) as received (length 100 mm, diameter 50 mm), (b) after wash-coating by y-alumina and impregnation by iridium and (c) front view of a 30 ppi foam cordierite monolith.

Figure 2. Photo of a channel of a 400 cpsi cordierite monolith (a) coated by y-alumina and (b) impregnated by iridium (first catalyst set). EDS spectrum of the circle inside.

The introduction of automobile exhaust catalysts in the United States and elsewhere has produced a major market for platinum-type oxidation and reduction systems. An innovative consequence of this industry has been the development of ceramic honeycombed monoliths as catalyst supports. These structures contain long, parallel channels of less than 0.1 mm in diameter, with about SO channels per square centimeter. The monolith is composed of cordierite (2MgO - 2AI2O) SSiOj) and is manufactured by extrusion. A wash coat of stabilized alumina is administered prior to deposition of the active metal, either by adsorption or impregnation methods. 

A 400 cpi cordieiite monolith is coated with a polymer made from the polymerization of furfuryl alcohol. The coated cordierite is then heat treated (calcination), and after an activation step the active metal, Pd, is impregnated followed by another heat treatment. One characteristic of the monolith catalyst made this way is its low surface area (13). The hydrogenation of nitrobenzene is used to probe the activity of the monolith catalyst. Table 10 summarizes these results for a series of monolith catalysts. 

The aim of this research project is the design and synthesis of optimal monolithic reactors and its use in deep desulfurization. In order to do so, state-of-the-art HDS powder catalysts were first prepared and their activity in thiophene HDS compared to the monolithic catalysts. These monolithic catalysts were prepared from cordierite and coated first with two layers of a-AI2O3 followed by one layer of Y-AI2O3. The coated monoliths were then impregnated with NiMo solutions (optimized for the powder catalysts) and some parameters were optimized (such as impregnation time and drying procedure). Finally, monolithic catalysts with the same characteristics as powder catalysts were obtained. 

If, however, the selectivity of a reaction is influenced by the presence of a thick support layer on the channel walls, the use of a different type of monolith support than the classical carbon-coated monolith is recommended. This was shown in the ruthenium-catalyzed reaction. EPMA analyses showed that ruthenium species are present both in the pores of the outer carbon washcoat layer and on the surface of the carbon inclusions located inside the monolith walls. No ruthenium was found in the empty macropores of the cordierite, since (1) there is no strong interaction between the precursor and the cordierite, and (2) after impregnation and washing, the macropores are emptied first upon drying, due to the capillary forces. The presence of active phase in the walls of the monolithic substrate is undesired, since it makes the diffusion path of the reactants to the active ruthenium sites longer. To prevent deposition of ruthenium in the waU,... 

The monolithic samples were prepared by coating cordierite honeycombs (cell density 62 cells/cm wall thickness 20 pm) with an aqueous sluny of the desired washcoat oxide. After drying and subsequent calcination at 530°C for 2 h in air, the washcoated supports were impregnated with an aqueous solution of the platinum salt, dried and activated in hydrogen for 2h at 530°C. The total platinum loading was fixed at 50 g/ft3 Pt. 

Catalysts were prepared by impregnating the noble metal chloride onto either an alumina washcoat or a proprietary washcoat containing alumina, ceria and other base metals. The catalyst was supported on a monolithic cordierite substrate with 64 square cells/cm. Cylindrical cores used for laboratory evaluations were 2.5 cm in diameter and, unless otherwise noted, 5 cm in length. The length of each core was composed of smaller segments taken from various locations down the monolith bed in order to minimize sampling biases. 

Honeycombs made of different materials (cordierite, mulUte, muUite-zirconia, alumina, silicon carbide, yttrium-stabilized zirconia) have been supplied by CTI Company [8] as supports to prepare catalysts for lab-scale reactors. They present square channels and a total volume between 1 and 2 cm. The external shape can be parallelepiped or cylindrical. The preparation of square-shaped monoliths for H2O2 decomposition has been presented at the previous Catalyst Preparation Symposium [5], focusing on the influence of the washcoat procedure and the nature of the active phase on the catalytic activity. Figure 4-b displays one example of such catalysts, as received and after washcoating, impregnation and reduction steps. 

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