Manifolds monolith

Sulfur oxides resulting from fuel sulfur combustion often inhibit catalyst performance in Regions II, III, and a portion of Region IV (see Fig. 7) depending on the precious metals employed in the catalyst and on the air/fuel ratio. Monolithic catalysts generally recover performance when lower sulfur gasoline is used so the inhibition is temporary. Pd is more susceptible than Rh or Pt. The last is the most resistant. Pd-containing catalysts located in hotter exhaust stream locations, ie, close to the exhaust manifold, function with Httie sulfur inhibition (72—74). 

Because this design has relatively low power density, recent work has focused on a monolithic SOFC, since this could have faster cell chemistry kinetics. The very high temperatures do, however, present sealing and cracking problems between the electrochemically active area and the gas manifolds. 

Minh N Q etal., 1993, Monolithic Solid Oxide Fuel Cells with Integral Manifolds. US Patent 5,526,499. 

Figure 8 A reactor consisting of four cross-flow monoliths in a steel manifold, (a) Reactor before assembly (b) top view of reactor. (From Ref. 36.)...

The scale-up of the traditional cross-flow reactor with corrugated interstitial planes has been solved by Degnan and Wei [35,36], who showed that, for example, four cross-flow monoliths can be positioned in a clever way inside a steel manifold (Fig. 8). This technique is not limited to only four monoliths but may be scaled-up to a much larger... 

Two catalyst formulations were used in this study. The first, a Pd catalyst having a loading of 50 g/ft.3 (0.29 wt.%), was obtained in monolith form (cell density 400 cells/in ). This washcoat formulation is considered to represent a state-of-the-art Pd catalyst for use in a rapid HC lightoff close-coupled (within 10-15" of the exliaust manifold) converter, and has been processed with several additives which serve to promote the activity of the Pd and to thermally stabilize the support and supported metal. The Pt-Rh monolith catalyst was also obtained in monolith fonn, having a cell density of 400 cells/in and a loading of 23.5 g/ft3 Pt, 1.68 g/ft3 Rli (0.13 wt.% Pt, 0.0093 wt.% Rh). This washcoat is designed for use in converters which will be exposed to exhaust temperatures consistent with an underfloor location (at least 25-30" from the exhaust manifold), which are significantly lower than those encountered in a close-coupled location. 

A different approach to monolithic membrane design has been taken by Norsk Hydro [23]. They chose to make a less complex monolithic membrane body while the manifolds applied at the ends of the monolith are more complex than the Amoco design of Fig. 8.7. The Norsk Hydro monoUthic membrane design is shown in Fig. 8.8. In this design, the monolithic body consists of parallel straight channels for the oxidant and reactant gas flows. The oxidant and reactant channels are adjacent to each other, in alternating rows or in a checkerboard pattern in... 

Figure 8.7 Figures 1 (A) and 3 (B) from U.S. Patent 5 356 728 [22] showing a cross flow monolithic reactor (10 and 30) from Amoco consisting of membrane cores (A, 17) or a monolithic block (B, 19). The manifold...

Figure 8.8 The Norsk Hydro monolithic membrane design from Fig. 7 ofWO03/033985 [23] showing the monolithic membrane body with top and bottom manifolds for feeding and withdrawing two gases.

In both cases, the four cordierite monoliths were positioned in a steel manifold shown in Fig. 2. 

SIC was proposed in 2003 as simple, rapid, and inexpensive separation approach (Satmsky et al., 2003 Chocholous et al., 2007 Solich, 2008 Ruzicka, 2014). Due to the low-pressure operation of SIA, direct coupling to conventional packed separation columns is impossible. SIC is actually a development of SIA with a view to achieving direct coupling to a separation column. The development of SIC was the result of the introduction of monolithic stationary phases. In a typical SIC manifold, a low-pressure monolithic separation column is introduced between the multiport selection valve and the detector (Figure 2.7). Monolithic columns consist of a single piece of high-purity... 

A monolithic minicolumn was incorporated in a FIA manifold for the simultaneous analysis of eight analytes, including sweeteners (aspartame, acesulfame-K, saccharin) and a few preservatives and antioxidants (Garcia-Jimenez et al., 2007). The singlechannel FIA system with a short monolithic C18 column, which allowed the separation of analytes according to their retention time, was used for quantification by measuring the intrinsic UV absorption of the analytes. The system was applied to the detection in different foodstuffs and the results obtained were in agreement with a reference FiPLC method. 

A hybrid FIA/HPLC system incorporating monolithic column chromatography was developed for the determination of six opiate alkaloids (morphine, pseudomorphine, codeine, oripavine, ethylmorphine, and thebaine) and four biogenic amines (vanilman-delic acid, serotonin, 5-hydroxyindole-3-acetic acid, and homovanillic acid) in human urine, using tris(2,2 -bipyridyl)ruthenium(III) and acidic potassium permanganate CL detection (Adcock et al., 2007). This hybrid system approaches the automation and separation efficiency of HPLC while maintaining the positive attributes of FIA, such as manifold versatility, speed of analysis, and portability. 

In addition to the planar geometry, inorganic membranes can also be produced in flat disk, tubular (dead-end or not), monolithic multi-channel, or hollow fiber configurations as shown in Figure 1.6. Disk membranes are often used in the laboratory because they can easily be fabricated by the conventional pressing method. In the case of tubes, they can be assembled in a module containing a number of tubes connected to a single manifold system. 

In low pressure gas phase applications such as vent stream cleaning and solvent recovery, high pressure drops are liable to occur due to the low density and high velocity of the fluid. To overcome this problem very shallow adsorption beds are sometimes used. Adsorption beds with low aspect ratios, however, may result in flow distribution problems, and therefore some of the pressure drop that is saved must be sacrificed by adding flow distribution systems of manifolds, baffles and screens. Other ways of keeping the pressure drop to a minimum in low pressure gas phase applications include the use of specially shaped adsorbents such as the trilobe and monolithic materials shown in Figure 2.7 in Chapter 2. 

An evolution of the flat planar design is the monolithic SOFC (Fig. 10). This consists of corrugated thin cell components. The result is that the volumetric power density is very high. On the other hand, the structure is more complex to realize, as well as the manifold system compared to the flat planar one. Based on this configuration, the Japanese Chubu Electric Power Company, INC. (CEPCO) and Mitsubishi Heavy Industries developed the so-called MOLB (Mono-block Layer Built) cells (Nakanishi et al. 2004). 

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