Influence of acid prehydrolysis on the process of wood oxidation into vanillin and pulp

The influence of pine wood (Pinus Sylvestris) prehydrolysis on the consumption of main reagents (O-2 and NaOH) in the subsequent catalyzed oxidation of the obtained lignocelluloses into vanillin and pulp has been studied. Prehydrolysis of the feedstock was performed with HCl in the water and gas phases. Catalytic oxidation was performed in an autoclave in an aqueous-alkaline medium in the presence of CuO as a catalyst. Native lignin was shown to be inhomogeneous in the process of oxidation into vanillin, and in the first approximation lignin consists of two fractions: the first, which is easily and selectively oxidized to vanillin, and the second, which is oxidized slowly and non-selectively. Acid-catalyzed prehydrolysis of wood leads to further differentiation of the lignin into the selectively and non-selectively oxidizing fractions. The developed two-stage process (prehydrolysis of wood and oxidation of the resulting lignocelluloses) decreases the consumption of NaOH in the oxidation process by 2-5 times as compared to the known data down to the values of 3.7-5.2 g per g of vanillin obtained.