Thermochemical treatment of radiata pine (Pinus radiata) bark with hydrogen peroxide solutions at temperatures higher than 100 degrees C

Radiata pine bark was treated with 0-15% hydrogen peroxide (H2O2) solutions at temperatures higher than 100 degrees C, and fractionated into water sol uble, insoluble, and gas fractions. The distribution of these fractions was calculated on the basis of weight and carbon content, and compared with th e aim of finding the optimum conditions for efficiently obtaining water-sol uble materials for producing wood adhesives. The yield of water-soluble mat erials was significantly dependent on the temperature and the concentration of H2O2 solution. The highest yields of water-soluble materials (47.4 and 47.9% on the basis of weight and carbon content, respectively) were obtaine d with 15% H2O2 solution at 120 degrees C. The yield increased with increas ing temperature up to 120 degrees C and then decreased at higher temperatur es. Under the latter conditions, gases such as CO2 and CO were generated. W hen the bark was treated with 15% H2O2 solution at 140 degrees C, an exothe rmic reaction took place and 47.4% of the carbon of the bark was converted into gases. At the same time, most of the H2O2 was decomposed. The water-so luble fraction mainly consisted of low molecular weight acidic components, which are degaradated and oxygenated products of lignin and polyflavanoids. This bark solubilization process consists of very complicated combinations of various reactions. Many organic compounds, other than acids, might be p resent in the water-soluble fraction. The water-insoluble material is the o xygenated cellulose compound.