Lignin Acidolysis Predicts Formaldehyde Generation in Pine Wood

Pinus virginiana wood was heated (200 degrees C, 10 or 60 min) while dry or after aqueous/acid/base pretreatment in order to reveal mechanisms of formaldehyde (CH2O) generation. Consistent with prior reports, among wood structural polymers, lignin was the overwhelming source of biogeriic CH2O (defined as having a carbon source in wood). Effects of wood extractives were ignored and reserved for a later report. The selection of acid catalyst strongly affected CH2O generation as predicted in the acidolysis literature of lignin model compounds and isolated lignins. Lignin methoxyl cleavage was observed but considered an unlikely source of CH2O under the experimental conditions. Alkaline pretreatments did not catalyze CH2O generation above levels observed using neutral water. Regarding wood-based composite manufacture, the implications are that lignin reactions might be manipulated during hot-pressing. Potential benefits include reduced product emissions and/or novel cross-linking strategies using biogenic CH2O. Perhaps even lignin repolymerization could be promoted for benefit, in direct opposition to biorefinery strategies for lignin removal.