Pine extractives strongly affect lignin thermochemical pathways

Interactions between Pinus virginiana wood and the corresponding extractives played a large role in lignin thermochemistry and selectivity of lignin acidolysis pathways, as determined by thioacidolysis and biogenic formaldehyde analysis. Heating wood (dry wood, 200 °C, 10 min) generates formaldehyde, principally via lignin acidolysis; this was studied as a function of extractives removal. Formaldehyde generation in P. virginiana and P. radiata woods was substantially reduced by extractives removal, but extraction had no effect on yellow-poplar (Liriodendron tulipifera). Isolated P. virginiana extractives generated thermochemical formaldehyde at low levels; but the greater extractives effect appeared to be catalysis of formaldehyde generation in whole wood, probably by lignin acidolysis. According to thioacidolysis, lignin in P. virginiana wood was thermally stable when extractives were present; whereas substantial lignin degradation occurred after extractives removal. In nearly opposite fashion, yellow-po...