Attempted Removal of Metal Ions and Subsequent Vacuum Pyrolysis of Barks from Five Species of Softwoods

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Abstract
Samples of whole bark were collected from sub-alpine fir, Engelmann spruce, Douglas fir, western larch and lodgepole pine. Attempts to remove metal ions from the barks by ion exchange with dilute acid at room temperature showed that up to one third of these ions (especially calcium) are inaccessable to aqueous acid and hence not removed. The barks were subjected to vacuum pyrolysis before and after acid washing and the tars analyzed by gas chromatography as trimethylsilyl ethers. The incomplete removal of metal ions resulted in significant increase in pyrolytic production of the major products derived from polysaccharides (viz. levoglucosan and anhydroarabinose).