The effect of lignin concentration on the reaction rate of vanillin production is depicted in Fig. 12.9c. The calculated maximum yield on lignin basis (wt%) decreases with the CL: 10, 8.3, and 3.0% for CL of 30, 60, and 120 g/l, respec­tively. The slope of the straight line found for initial vanillin production rate as a function of the initial lignin concentration provides the reaction order of 1 with respect to lignin concentration [116].

Considering the results of vanillin production from a kraft lignin in alkaline medium, under the reported conditions, the following kinetic law was achieved:

rv = k[O2]175 [L] (12.1)