Carbon monoliths applications

In addition to the particulate adsorbents listed in Table 16-5, some adsorbents are available in structured form for specific applications. Monoliths, papers, and paint formulations have been developed for zeolites, with these driven by the development of wheels (Fig. 16-60), adsorptive refrigeration, etc. Carbon monoliths are also available as are activated carbon fibers, created from polymeric materials, and sold in the forms of fabrics, mats, felts, and papers for use in various applications including in pleated form in filters. Zeolitic and carbon membranes are also available, with the latter developed for separation by selective surface flow [Rao and Sircar, J. Membrane Sci., 85, 253 (1993)]. 

Hu YS, Adelhelm P, Smarsly B, Hore S, Antonietti M, Maier J. Synthesis of hierarchically porous carbon monoliths with highly ordered microstructure and their application in rechargeable lithium batteries with high-rate capability. Adv Funct Mater. 2007 17(12) 1873-8. 

Ga.s S5mthesis and application of carbon monoliths Environmental Reduction of NO with NH3 Low-temperature de-NO realistic conditions Vanadium oxide/ carbon-coated monohth (164)... 

Liquid S5mthesis and application of carbon monoliths Biocatalysis... 

The variety of activated carbons, carbon fiben, and carbon monoliths present on the market along with differences in the molecules to be adsorbed— removed causes that the choice of the adsorbents for a desired application becomes a difficult task. The capacities, for H2S, SO2, NO,., HCN, or VOCs removal depend on the type of carbon used (Fig. 21.3). The problem is even more complex when multicomponent adsorption is expected to occur and the regeneration options have to be considered. Usually carbon specifications... 

In catalytic applications, monoliths can provide better control of the contact time of reactants and products with the catalyst. This leads to a potential increase in selectivity. Together with the advantages over conventional trickle-bed reactors (pressure-drop surface area, short diffusion lengths), this makes the monohth reactor very suitable for use in consecutive reaction schemes, such as selective oxidation or hydrogenation. Literature dealing with carbon monolith structures is not yet extensive, however, and a limited number of applications have been reported, as shown in Table 11.2. 

The decision as to which monolith type to use is therefore dependent on the type of application, but commercial availability and carbon type should also be evaluated. Cordierite and Mast monoliths are commercially available, whereas ACM is not. When cordierite is used in combination with CNFs, possible cracking of the support can occur. For ACM monoliths, the open structure allows high carrier loading and prevents cracking upon the growth of CNF. For integral carbon monoliths in combination with biocatalysts, the pore size and chemistry of the carbon must be tuned to match the properties of the biocatalyst. 

Because the application of carbon-based monoliths forms an emerging field in (bio)chemical engineering, new applications and process developments can be expected in the future. One might think of applications of monoUth-CNF combinations in water-air filter systems [66], carbon precnrsors with tailored porons texture for production of integral/coated monoliths, ultrathin coatings on ACM monoliths for higher mass-transfer rates, and carbon monoliths in adsorption processes or as high-surface-area electrodes. 

For successful application of carbon-coated monolithic catalysts, the deposition of active phase in the walls of a monolithic substrate should be prevented. To prevent deposition of ruthenium in the wall (1) substrates with nonporous walls can be used, or (2) the cordierite monolithic substrates can be modified with a-AEOs, blocking the macroporosity of the cordierite and rounding the channel cross section to enable a more uniform thickness of the carbon coating layer. Alternatively, ACM monoliths or integral carbon monoliths with very thin walls having a characteristic diffusion length similar to the activated carbon slurry catalysts can be employed. 

From an application point of view, the volumetric capacities are even more important than that on a gravimetric basis, due to the limited volume of the gas storage tank. Under this consideration, Qian et al. [131] optimized the stractural features of hierarchical porous carbon monolith by incorporating the advantages of MOFs (Cu3(BTC)2) to maximize the volumetric based CO2 capture capability (CO2 capacity in cm per cm adsorbent). The mesoscopic structure of the HCM-Cu3(BTC)2 composites and the parent materials (HCM and Cu3(BTC)2) were characterized by SEM. The SEM micrograph (Fig. 2.24) clearly displays that Cu3(BTC)2 crystallites are bom within the macropores of the HCM matrix. The sponge-like skeleton of HCM before and after the MOF growth remains... 

The high density hybrid monoliths would thus appear to be well suited to storage applications. However, the data presented here are for hybrid monoliths that are far from optimum as storage carbons. A great deal of development work is required to increase the micropore volume and storage capacity of the monoliths. Some of our preliminary work in this context is discussed subsequently. 

Chemical vapor deposition (C VD) is a versatile process suitable for the manufacturing of coatings, powders, fibers, and monolithic components. With CVD, it is possible to produce most metals, many nonmetallic elements such as carbon and silicon as well as a large number of compounds including carbides, nitrides, oxides, intermetallics, and many others. This technology is now an essential factor in the manufacture of semiconductors and other electronic components, in the coating of tools, bearings, and other wear-resistant parts and in many optical, optoelectronic and corrosion applications. The market for CVD products in the U.S. and abroad is expected to reach several billions dollars by the end of the century. 

Tamainot-Telto, Z., and R.E. Critoph, 2001. Monolithic carbon for sorption refrigeration and heat pump applications, Appl. Thermal Eng., 21 (1), 37-52. 

A recently developed adsorbent version of ORNL s porous carbon fiber-carbon binder composite is named carbon fiber composite molecular sieve (CFCMS). The CFCMS monoliths were the product of a collaborative research program between ORNL and the University of Kentucky, Center for Applied Energy Research (UKCAER) [19-21]. The monoliths are manufactured in the manner described in Section 2 from P200 isotropic pitch derived fibers. While development of these materials is in its early stages, a number of potential applications can be identified. 

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