Thermochemical Treatment of Radiata Pine (Pinus radiata) Bark with Hydrogen Peroxide Solutions at Temperatures Higher than 100 °C

Abstract

Abstract Radiata pine bark was treated with 0—15% hydrogen peroxide (H2O2) solutions at temperatures higher than 100 °C, and fractionated into water soluble, insoluble, and gas fractions. The distribution of these fractions was calculated on the basis of weight and carbon content, and compared with the aim of finding the optimum conditions for efficiently obtaining water-soluble materials for producing wood adhesives. The yield of water-soluble materials 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 obtained with 15% H2O2 solution at 120 °C. The yield increased with increasing temperature up to 120 °C and then decreased at higher temperatures. Under the latter conditions, gases such as CO2 and CO were generated. When the bark was treated with 15% H2O2 solution at 140 °C, an exothermic 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-soluble 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 present in the water-soluble fraction. The water-insoluble material is the oxygenated cellulose compound.