Microporous carbons pore-structural regularity

More promising for reactive separations involving gas phase reactions appears to be the development and use in such applications of microporous zeolite and carbon molecular sieve (Itoh and Haraya [2.25] Strano and Foley [2.26]) membranes. Zeolites are crystalline microporous aluminosilicate materials, with a regular three-dimensional pore structure, which are relatively stable to high temperatures, and are currently used as catalysts or catalyst supports for a number of high temperature reactions. One of the earliest mentions of the preparation of zeolite membranes is by Mobil workers (Haag and Tsikoyiannis... 

In order to improve the structural ordering of zeolite-templated carbons, Ma et al. have investigated systematically the synthesis of microporous carbons using zeolite Y as hard template. They used a two-step method to prepare an ordered, microporous carbon with high surface area, which retained the structural regularity of zeolite Y by filling as much carbon precursor as possible into the zeolite pores so as to prevent any subsequent partial collapse of the resulting carbon framework. In the... 

Barata-Rodrigues et al. [73] reported that the CVD technique does not help improve the structural regularity of a zeolite-templated carbon. We indeed found that, when wet impregnation is followed by a CVD treatment, the XRD peak at 6° 20 can be observed, indicating the appearance of an ordered pore structure [75]. However, this XRD peak cannot be resolved for the carbon prepared without using the CVD technique [74]. An alternative route to the synthesis of ordered microporous carbons by using zeolite Y as template has also been described [88]. In addition, the use of other zeolite templates such as EMC-2 to improve structural regularity of replicated microporous carbons has been demonstrated... 

Microporous materials possess pore structures in which the major fraction of the total void colxjune is contained in the pore size region below 20 A. The structures of microporous materials can span the entire range from X-ray amorphous compounds (e.g., small pore oxides xero-gels) and highly disordered materials (e.g., carbon molecular sieves) to quasi-crystalline compounds (e.g., pillared clays) and regular, 3-dimensional crystalline structures (e.g., zeolites). 

As seen from the table, the average size of micropores with 0.6 nm for K1 to 1.6 nm for K3 grows at an increase in the activation degree. Herewith, the mesopore fraction increases. Despite this, the 5bet ue for K3 is very high 2600m /g. It is important to note that all studied carbon samples have a narrow small pore distribution, that is, a rather regular structure. 

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