Carbon-based monolithic structures

Recently, there has been a growing interest in the use of monohthic structures for (bio)chemical conversion and adsorption processes. A very versatile type of monolith is based on carbon. The combined properties of carbon and monolithic structures create a support with great potential. In this chapter we describe recent developments in the field of carbon-based monolithic structures with respect to preparation, support properties, and application in catalytic processes. Furthermore, two examples are used to demonstrate the approach and possible pitfalls when using carbon (coated) monoliths in catalysis. 

Carbon-based monolithic structures are only occasionally a topic in scientific literature. However, there are several patents that describe a variety of preparation procedures for these materials [58]. 

Carbon-based monoliths can be of the integral or coated type [5,6]. For practical applications, several requirements are set to monolithic structures. For a coated type of monolithic support, the mechanical properties are adopted from the ceramic or metallic monoliths. It is, however, important that the coating adhere well to the monolith to prevent flaking and subsequent loss of active... 

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... 

Ceramic matrix composites (CMCs), in which carbon or ceramic fibers are embedded in a ceramic matrix, have been designed to overcome the intrinsic brittleness of monolithic ceramics with a view toward structural uses at extremely high service temperatures. The most commonly used are carbon (C/C) and SiC matrix composites (C/SiC and SiC/SiC). Ceramic matrix composites with a silica based glass or glass-ceramic matrices have also been studied [12] [53-56]. 

---