Ethylene Glycol/Soda Organosolv Pulping of Olive Tree Trimmings


  • Luis Jiménez
  • Alejandro Rodríguez
  • Ildefonso Pérez
  • Antonia María Calero
  • José Luis Ferrer


Ethylene glycol, organosolv, soda, pulp, composition, viscosity, olive tree wood


This paper reports on the influence of independent variables in the ethylene glycol/soda pulping of olive wood trimmings [viz. cooking temperature (165-195°C) and time (30-90 min), ethylene glycol concentration (5-15%), soda concentration (2.5-7.5%), and liquid/solid ratio (4/1-6/1)], on the yield and viscosity and holocellulose, α-cellulose, and lignin contents of the pulps. By using a central composite factorial design, equations that relate each dependent variable to the different independent variables were obtained that reproduced the experimental results for the dependent variables with errors less than 8%. Obtaining pulp with maximum possible holocellulose content (78.9%), α-cellulose content (61.8%), and viscosity (426.8 mL/g), in addition to the minimum possible lignin content (19.1%), entails using high ethylene glycol and soda concentrations (15% and 7.5%, respectively), a long cooking time (90 min), and a low liquid/solid ratio (4/1). A high temperature (195°C) is also required to maximize the holocellulose and α-cellulose contents and viscosity, and one of 175°C to minimize that of lignin. On the other hand, the maximum yield (59.4%) is obtained by using a long cooking time (90 min) and low values of the other operating variables. The use of intermediate operating conditions (viz. a temperature of 187.5°C, an ethylene glycol concentration of 15.0%, a soda concentration of 7.5%, a liquid/solid ratio of 4/1, and a cooking time of 30 min) results in a yield, holocellulose content, α-cellulose content, lignin content, and viscosity values (52.2%, 76.5%, 58.8%, 20.40%, and 352.7 ml/g, respectively) that differ by only 12.1%, 3.0%, 4.9%, 6.8%, and 17.4% from the respective optimum values, all with substantial savings on power consumption and immobilized capital in commercial operations. The strength-related properties of this pulp can be improved with an appropriate refining treatment.


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