Surface and bulk chemistry of charcoal obtained by vacuum pyrolysis of bark: influence of feedstock moisture content

Samples of maple bark and softwood bark with moisture contents ranging from 6 to 42 wt% were pyrolyzed under vacuum at a temperature of 775 K. Vacuum pyrolysis of maple bark yields approximately 30 wt% wood charcoal on an anh ydrous basis. For softwood bark the charcoal yield is smaller (23-28 wt%). The charcoal yield of maple bark pyrolysis depended only slightly on the ba rk moisture. The surface and bulk chemistry development of the charcoals wa s studied by electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy, respectively. With dec reasing bark moisture the charcoal surface becomes more graphite-like, wher eas the bark moisture had only a limited influence on the bulk structure. T he high specific surface area of the charcoals at 200-300 m(2)/g makes thes e materials valuable feedstocks for the production of activated carbons. (C ) 2000 Elsevier Science B.V. All rights reserved.