The preparation and adsorptive properties of ammonia-activated viscose rayon chars

Abstract

Viscose rayon chars have been activated in ammonia under varying conditions in order to investigate whether the presence of N-containing groups in the char structure led to a limitation of pore development in the micropore range, as is the case for polyarylamide-derived chars. It was found that two types of nitrogen species are formed and that the resultant chars are all, except in one case, essentially microporous. The amount of nitrogen present is limited as the process of "deactivation" of active sites by reaction with ammonia occurs. This may account for the limitation of pore development. Introduction of nitrogen into the char does not produce significant pore narrowing. This tends to confirm the predominant role of precursor crystallinity in determining the nature of the pore structure formed during activation. © 1993.