Solvent effects in autocatalyzed alcohol-water pulping comparative study between ethanol and methanol as delignifying agents

The autocatalyzed pulping (without additives) of Eucalyptus globulus with ethanol-water and methanol-water is studied in order to compare the effects of the two more frequently used solvents in Organosolv pulping. The study about the influence of the pulping alcohol on pulp properties (measured as Kappa number, yield and viscosity) is carried out by means of a 2(4) factorial design including the type of alcohol as a categorical variable. The effects for the variables (temperature, time, concentration and type of alcohol) and the interactions among them are determined. The statistical analysis for each response makes it possible to evaluate if the type of alcohol has a significant influence on the properties of the pulp obtained. In the range of temperature, time and solvent concentration studied, methanol yields pulps with lower Kappa number, on average; whereas ethanol provides better delignification at high-intensity cooking conditions. Both alcohols show similar selectivity when pulp total yield is considered, but higher screened yield values can be obtained in ethanol pulping. The viscosity is better for ethanol pulps on average, however, in the 20-30 Kappa number range methanol pulps exhibit higher viscosity. (C) 2002 Elsevier Science B.V. All rights reserved.