With the addition of ethanolamine into alkaline pulping liquor, delignification was improved due to the increase of cleavage of fi-O-4 ether linkages and decrease of condensation of lignin [156]. This ideal has been realized in pulping of olive wood trimmings [157]. Under the optimal conditions, i. e., 15% ethanolamine concen­tration, 7.5% soda concentration and liquid to solid ratio of 4 at 195°C for 30 min, pulp was produced with acceptable yield and viscosity.

In addition, ethanolamine can be used as a cooking agent at a high concen­tration without the addition of alkali, and this pulping process was applied to oil palm EFB, rice straw [158-160] and hesperaloe funifera [161]. A comparison of pulping of EFB with ethyleneglycol, diethyleneglycol, ethanolamine and dietha­nolamine suggested that pulp obtained by using ethanolamine exhibited the best properties [158]. With regard to yield, kappa number and brightness, the properties

Fig. 11.4 Process of solvents and by-products recovery stages of ethylene glycol fractionation [140] of EFB ethanolamine pulp were comparable to those of kraft pulp from holm oak or eucalyptus wood. In addition, this process can be operated under a lower solvent concentration, temperature and time, with reduced energy and immobilized capital costs.