03.08.2015   Biomass Conversion

Influence of the Parameters in Lignin Oxidation and Vanillin Oxidation

Several authors have been studying the influence of the reaction conditions and vanillin and syringaldehyde yield as depicted in Table 12.3. The most compre­hensive work found in literature is that developed in LSRE in batch [20, 36, 116, 118, 119, 121, 133, 153] and continuous processes [119, 120, 122, 133].

Reaction time, min Reaction time, min

Fig. 12.9 Vanillin profile during the lignin oxidation with molecular oxygen in aqueous NaOH at different operation conditions [36]:a Effect of pO2 (CL = 60 g/l, CNaOH = 2 M, Tj = 393 K, Pt = 9.2-9.4 bar). b Effect of CNaOH (CL = 60 g/l, Ti = 393 K, pO2i = 3.7 bar, Pt = 9.7 bar. c Effect of CL (CNaOH = 2 M, Tj = 393 K, pO2i = 3.7 bar, Pt = 9.6 bar). d Effect of (CL = 60 g/l, CNaOH = 2 M, pO2i = 3.7 bar, Pt = 9.7-10 bar)

Figure 12.9 shows the vanillin concentration profile during reaction of lignin in aqueous NaOH with molecular oxygen considering variation of O2 partial pressure (pO2), initial concentration of NaOH (CNaOH), concentration of lignin (CL) and initial temperature (Ti) [36].

Vanillin oxidation was also studied [149] since the degradation of the produced vanillin is a key point on the sustainability of the process. Figure 12.10 shows the main results of experimental and simulation work in this subject [121, 149], where the influence of pO2, pH, and Ti are shown.