Nanoporous activated carbon fibers (Busofit(TM), BACF) showed effective adsorption of carbon tetrachloride (CTC) vapors. About 2.50mmolxg(-1) of chlorine, in the form of trichloromethyl and chlorine groups, can be grafted onto BACF surface by thermal decomposition of CTC at 450 degrees C. To obtain solid acids, this chlorinated BACF, the brominated and pristine BACFs, taken for comparison, were subjected to progressive sulfidation, hydrolysis and oxidation reactions for grafting sulfonic groups. By this wet route, sulfonic groups can substitute only 1.1-1.4mmolxg(-1) of the grafted chlorine groups. Nevertheless, solid acids obtained in this way have high catalytic performance in the 2-propanol dehydration to propene. For these catalysts, in the range from 180 to 220 degrees C, a 100% alcohol conversion with 100% selectivity to propene could be reached. Thermoprogrammed desorption and thermal analysis revealed that the pyrolytic chlorination triggers the highest thermal stability of grafted sulfonic groups, and, they can repeatedly act in the dehydration reaction.