Production of Phenolic Compounds from Catalytic Oxidation of Kraft Black Liquor in a Continuous Reactor
2022
Hernández Mañas, Antonio | Chaussard, Nicolas | Bertaud, Frédérique | Vilcocq, Léa | Fongarland, Pascal | Djakovitch, Laurent
Black liquor is a side stream from the pulp and paper industry containing lignin and other organic and inorganic materials. Catalytic alkaline oxidation of black liquor was carried out employing a CuO/TiO₂ catalyst in a trickle-bed reactor employing mild reaction conditions (150–200 °C, 80 bar) and short contact times (4–9 min). The effects of temperature, contact time, and presence of catalyst were investigated. In our best operating conditions, i.e., 200 °C and 4 min contact time, lignin conversion was complete, and phenolic monomers were obtained (maximum total yield 6.2 wt %), including vanillin (maximum yield 3.3 wt %). Vanillin represented 53 wt % of phenolic monomers. At longer contact times, the degradation of phenolic compounds was observed. The application of a continuous trickle-bed reactor, allowing short reaction times and limiting degradation reactions, is particularly appropriate for this reaction. Vanillin productivity in this reactor is 936 g m³ h–¹.
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