EFFECT OF PRETREATMENT OF OAK BARK TO DEVELOP POROSITY IN THE CELL TISSUE ON SUBSEQUENT IRON-CATALYZED HYDROGASIFICATION

Oak bark was immersed in boiling water or extracted with supercritical carbon dioxide in the presence of water to develop porosity in the ce ll tissue before iron catalyst was loaded by wet impregnation. The iro n-loaded bark was carbonized at 500 degrees C, and the resulting char was hydrogasified in a thermobalance to measure the reactivity by the temperature-programmed method. The reactivity up to 700 degrees C was higher than that of raw bark char at 5wt% iron loading because of impr oved dispersion of the metal particles. Supercritical extraction was s uperior to boiling in its effect. These pretreatments following demine ralization with HCl enhanced the activity of iron to a greater degree, so that demineralized and extracted char with 5wt% iron gave a conver sion of 90% at 700 degrees C. Demineralized and boiled char also excee ded demineralized char in reactivity at the same iron loading. These r esults showed the significance of development of porosity for higher c atalytic activity of iron in subsequent gasification. The X-ray diffra ction intensity of metallic iron was found to be useful for judging it s dispersion on bark char containing a large amount of mineral matter. Copyright (C) 1996 Elsevier Science Ltd.