THE DELIGNIFICATION OF WOOD BY STRONG ALKALINE SOLUTIONS

The delignification of wood by means of sodium, potassium, and lithium hydroxides has been determined with alkaline concentrations from 1.4 to 14.3 molar, and at temperatures from 120° to 180 °C. A small-scale experimental technique was used by means of which the time, temperature, and concentration variables could be closely controlled.It was found that delignification increased with concentration. A 2.9 M solution reacted about twice as fast as a 1.4 M solution of sodium hydroxide at 160 °C. The difference in rate of reaction is less for solutions of concentrations of 2.9 and 4.5 M. Potassium hydroxide of 1.4 M concentration reacts only slightly more readily than sodium hydroxide of the same concentration, but the difference in reaction rate becomes more marked with increase in concentration. Lithium hydroxide reacts much more slowly than either of the other two hydroxides. There is a marked increase in reaction rate with increase in temperature. A ten degree rise in temperature somewhat more than doubles the rate of delignification. The rate of reaction is considerably diminished by the presence of sodium chloride or of reaction products in the cooking liquor.