Organic chemical structure and structural shrinkage of chars prepared from rockrose

Chars were prepared by heating rockrose (Cistus ladaniferus L) under dynamic and isothermal conditions between 200 and 1000 degrees C in nitrogen. Several techniques including chemical analysis, Fourier transform infrared (FTIR) spectroscopy, molecular simulation, density measurements, mercury porosimetry and adsorption were used to study the chemical structure and pore structure. The chars prepared at high temperatures in particular contain oxygen in ether type structures, which may cross-link aromatic sheets. The degree of development of porosity in the chars and the porosity distribution seem to depend on the amount of volatile matter removed at each temperature during pyrolysis and on the structural shrinkage of the residual carbon. Both factors act contrarily on the pore structure of the chars, the latter effect being stronger at high temperatures. The shrinkage of the carbon structure may be caused by break down of interlayer carbon-oxygen bonds. (C) 1998 Elsevier Science Ltd. All rights reserved.