Effect of calcium catalyst loading procedure on the porous structure of active carbon from plum stones modified in the steam gasification process

The effect of mode of calcium catalyst deposition on the active carbon (produced from plum stones) surface on the formation of micro- and mesoporous structures during gasification of the carbon with steam as well as on the kinetics of this process was investigated. The catalyst (1.44%) was deposited by conventional impregnation or ion exchange. Partial gasification of the modified carbon in the absence of catalyst causes significant increase of micropore volume and small increase of mesopore surface area with the increase of burn-off degree. On the contrary, gasification of the samples in the presence of calcium catalyst causes the decrease of sorption capacity of micropores and the significant increase of mesopore surface. The above changes are more effective for the samples containing the catalyst deposited by ion-exchange. Micropore capacity and surface area of mesopores were determined by means of the alpha(S)-method. The adsorption process on the heterogeneous solids was described by means of integral equation including various local isotherms. This equation has been solved by the regularization method. On the basis of this method changes in the structural parameters were estimated. The activation energies of individual reactions were determined. The mechanism of gasification process as well as the selection of proper concentration of steam optimum from the kinetic viewpoint have been discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.