Cylindrical monoliths

The synthesis of self-supporting monolithic cylindrical rods ( lcmxlOcm) again with compositions and morphologies similar to resins has been reported [51]. These can also be prepared with a texture that allows each rod to be cleaved into discs. ( lcmx0.2cm, mass 250-500mg) (Fig. 1.10). The latter can be handled by a robot arm and soHd phase synthesis on one disc allows up to 0.5 mmole of a single compound to be produced. Similar disc and alternative shaped macroscopic supports have now been reported [52-54]. 

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... 

Fig. 2. Temperature profile in the middle of a 5 cm cylindrical mould during the polymerization of a GMA-EDMA monolith. The increase of the temperature by 77 °C significantly influences the structure of the GMA-EDMA monolith...

In a follow-up study, Koptyug et al. 115) reported images of both liquid and gas flow and mass transport phenomena in two different cylindrical monolith catalysts (one with triangular channels, the other with square channels) at various axial locations within the monolith. Heibel et al. 116,117) addressed two-phase flow in the film flow regime and reported investigations of liquid distributions in the plane perpendicular to the direction of superficial flow, in particular, addressing the accumulation of liquid in the corners of the square channels of the monolith. 

Catalytic combustion in a monolith channel provides an illustration of boundary-layer flow in a channel [322], Figure 17.18 shows a typical monolith structure and the particular single-channel geometry used in this example. Since every channel within the monolith structure behaves essentially alike, only one channel needs to be analyzed. Also a cylindrical channel is used to approximate the actual shape of the channels. 

Figure 2 shows the shape and size of the Monolith alumina supports. These are in the form of cylindrical segments of about 2.54 cm in length and about 1.0 cm in diameter. These have longitudinal and parallel channels along their length. The size, shape and thickness of the walls of the channels are also shown in Figure 2. The Monolith structure has about 60 to 80 percent of its cross-sectional area open. Therefore, a bed of regularly stacked Monoliths would offer significantly less pressure drop than that encountered in conventional packed beds. This has been observed by Satterfield and Ozel (1) for a water-air system.

Adiabatic fixed-bed reactors constitute the oldest fixed-bed reactor configuration. In the simplest case they consist of a cylindrical jacket in which the catalyst is loosely packed on a screen support and is traversed in the axial direction (Fig. 9A). To avoid catalyst abrasion by partial fluidization, random catalyst packings arc always traversed from top to bottom. If fixed-beds composed of monolith catalyst sections are used, the flow direction is arbitrary. 

One way to improve the performance of photocatalytic air-treatment reactors is to decouple between cleaning the air and degrading the pollutants. Figure 14 shows schematically such a system (Chin et al., 2006 Shiraishi et al., 2003). The system includes two independent continuous flow systems interconnected by a rotating, cylindrical ceramic honeycomb. The rotation cycles the honeycomb rotor through a low temperature zone, where adsorption takes place, and a high temperature zone where desorption takes place, thus regenerating the monolith. The contaminated air flows... 

In this study mercury intrusion porosimetry (MIP) analyses were employed to determine the pore size distribution and pore volume over the range of approximately 100 pm down to 7.5 nm diameter, utilising CE Instruments Pascal 140/240 apparatus, on samples previously dried overnight at 150°C. The pressure/volume data were analysed by use of the Washburn Equation [14] assuming a cylindrical nonintersecting pore model and taking the mercury contact angle as 141° and surface tension as 484 mN m [10]. For the monolith... 

Many commercial ceramic membranes nowadays come in the form of a monolith consisting of multiple, straight channels parallel to the axis of the cylindrical structure (Figure 3.6). The surfaces of the open channels are deposited with permselective membranes and possibly one or more intermediate support layers. The porous suppon of these multi-channel structures are produced by extrusion of ceramic pastes described above with a channel diameter of a few millimeters. Their lengths are somewhat limited by the size of the furnaces used to dry, calcine and sinter them and also by such practical considerations as the total compact weights to be supported during heat ueatment and the risk of distortion in the middle section. It should be noted that this type of honeycomb... 

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