Heat treatment of rockrose char in air. Effect on surface chemistry and porous texture

The surface chemistry and the porous texture of activated carbons prepared from a charred product (C-lex-600), which was obtained from rockrose (Cistus ladaniferus, L.) extracted previously into petroleum ether, were studied. Activated carbons were prepared by heating C-Jex-600 between 350 and 850 degrees C in air to 40% burnoff. Methods of chemical analysis and FTIR spectroscopy as well as techniques of gas adsorption (N-2, 77 K; CO2, 298 K), mercury porosimetry, and density measurements were applied. In the FTIR study of the samples, the presence of surface olefinic C=C double bonds, aromatic rings, and oxygen functional groups was detected. Carbonyl groups were only found to a significant extent in C-Jex-600 and in the activated carbon prepared at 350 degrees C. The microporosity developed with increasing temperature between 350 and 750 degrees C. At higher temperatures, pore narrowings occurred. The gasifying action of air was strongly dependent on the removal of nonorganized matter from C-Jex-600 and on the pore size. The reaction time needed at 850 degrees C in air to reach burnoff 40% was less than a half of that at 350 degrees C, and was comparable to the times required in CO2 and steam under the same experimental conditions. Copyright (C) 1996 Elsevier Science Ltd