CFCMS

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

Fig.ll. SEM micrograph showing the macrostructure of CFCMS (scale bar represents lOOpm). 

Fig. 12. Mercury intrusion pore size distribution for an unactivated sample of CFCMS monolith.

The development of microporosity during steam activation was examined by Burchell et al [23] in their studies of CFCMS monoliths. A series of CFCMS cylinders, 2.5 cm in diameter and 7.5 cm in length, were machined from a 5- cm thick plate of CFCMS manufactured from P200 fibers. The axis of the cylinders was machined perpendicular to the molding direction ( to the fibers). The cylinders were activated to bum-offs ranging from 9 to 36 % and the BET surface area and micropore size and volume determined from the Nj adsorption isotherms measured at 77 K. Samples were taken from the top and bottom of each cylinder for pore sfructure characterization. 

Table 1. Micropore sfructure development during steam activation for CFCMS...

Fig.l3. Variation of DR micropore volume in a large CFCMS monolith with 10 4 wt% bum-off [27],... 

Table 2. Micropore structure data for large CFCMS monoliths activated via the O2 chcmisorption/activation route [7,27]...

Typical physical properties of our CFCMS monoliths are given in Table 3. The exaet value of a particular property is dependent upon the fabrieation route, eomposition, density, ete. Consequently, property ranges are given in Table 3 rather than absolute values. 

Table 3. Physical properties of CFCMS monoliths developed by ORNL/UKCAER...

Fig. 17. The voltage-current relationship (a) and resistive heating curve (b) for a CFCMS monolith (sample 21-2B, 18% bum-off, 2.5-cm diameter x 7 5-cm length) [23]...

Fig. 20. Typical C02/CH4 breakthrough plot for CFCMS monolith sample 21-11 (9% bum-off) at 25° C...

Fig. 21. A typical HjS breakthrough plot for a CFCMS monolith 21-2B (18% burn-off) at 25 C...

Fig. 22. CO2/CH4 breakthrough plots for CFCMS sample 21-lF (10% bum-off) showing the benefit of eleetrically enhanced desorption A. 1 volt, He purge 04 sipm B 1 volt, He purge 0.06 slpm, and C. 0 volt. He purge 0.06 slpm...

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