Pyrolysis of apple pulp: effect of operation conditions and chemical additives

The objective of this work was to evaluate the feasibility of using apple pulp (residue from apple pressing in cider manufacture) as a feedstock for activated carbon production. To this end, pyrolysis of apple pulp was studied using thermogravimetry. The effect of a series of operation variables (heating rate, temperature/time programs, gas flow and nature) was studied, attempting to increase the char yield at 400degreesC. Apple pulp exhibits two weight-loss steps, ascribable to decomposition of light fractions (hemicellulose) and cellulose. Changes in pyrolysis conditions had no effect on these two weight-loss steps and did not affect the yield of the process. Chemical additives (AlCl3, FeCl3, H3PO4, NH4Cl, KOH and ZnCl2) slightly affect the first step by inhibiting hemicellulose decomposition. while accelerating cellulose decomposition through dehydration reactions. Phosphoric acid exhibited the largest influence on the pyrolysis process. At concentrations higher than 30 wt.% H3PO4, the two weight loss steps ascribed to hemicellulose and cellulose decompositions overlapped, and above 100 wt.%, a single step was observed. It was concluded that impregnation with phosphoric acid can enhance the preparation of activated cartons by chemical activation of apple pulp. (C) 2002 Elsevier Science B.V. All rights reserved.