Catalytic conversion of black liquor under sub/supercritical conditions

Hélène Boucard (1) , Masaru Watanabe , Seiichi Takami (2) , Elsa Weiss-Hortala (1) , Radu Barna (1) , Tadafumi Adschiri (2)

1 RAPSODEE - Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement
2 WPI-AIMR - WPI Advanced Institute for Materials Research

Black liquor is an alkaline liquid residue of paper industry, containing ~80wt% of water and ~20wt% of organic matter and minerals. Our global project explores black liquor conversion by using properties of supercritical water. Exploratory conversion experiments have been made previously without catalyst and revealed the formation of three phases; especially an interesting gaseous phase with a high proportion of H 2 (~80% at 600°C). A solid residue is also observed and results from the polymerisation of phenolic compounds together with aldehyde crosslinks. Based on these results, this study is devoted to the catalytic conversion using CeO 2 nanocatalysts to improve gasification and H 2 production as well as to block coke formation. In sub-/supercritical conditions, water splitting occurs by CeO 2 catalysts, to produce active hydrogen and oxygen species. Thus these actives species react with molecules of the medium. Experiments are performed in sub-/supercritical conditions in batch reactor, during 15-60 min reaction time with and without catalyst. As expected, nanocatalyst of CeO 2 improved the conversion of black liquor at sub and supercritical conditions. Hydrogen production was not significantly affected by the catalyst while amounts of CO and CO 2 are reduced at short reaction time. The high basic pH of raw feedstock and remaining solutions impacts the CO 2 dissolution into carbonates. Supercritical water media and catalyst clearly affects the fragmentation of dissolved lignin compared to subcritical conditions.

Domaines: Génie des procédés; Ingénierie de l'environnement

Hélène Boucard, Masaru Watanabe, Seiichi Takami, Elsa Weiss-Hortala, Radu Barna, et al.. Catalytic conversion of black liquor under sub/supercritical conditions. 14th European meeting on supercritical fluids, May 2014, Marseille, France. 8p. ⟨hal-01725152⟩