Supercritical water gasification (SCWG), an effective wet biomass conversion technique which circumvents the energy intensive drying process, does not proceed substantially without high reaction temperatures (>600�C). In the present work, microalgae (Chlorella vulgaris) gasification in supercritical water was attempted at lower reaction temperatures with Ru or Ni catalysts. A 5wt% Chlorella suspension was gasified in a batch reactor at 385�C and 26MPa. Carbon conversion was low (ca. 20%) without catalyst but almost complete with supported or unsupported Ru or Ni catalyst, producing methane as the main gas component. Chlorella SCWG over supported Ru catalysts appeared to be a structure insensitive reaction in terms of selectivity similar to the case of ethanol stillages,1,2)while specific activity varied with Ru particle sizes.Characterization of fresh and spent Raney-Ni catalysts in SCWG of Chlorella using XRD and XPS found that the carbon deposition on the catalyst was not significant in the present reaction and Ni particle size increased after the reaction. It was also observed that Ni surface was oxidized during the reaction. Supported Ru catalysts also showed insignificant carbon deposition and increased metal particle size after the reaction but no surface oxidation. The differences in deactivation characteristics between these two catalysts will further be elaborated.1) Nguyen H.T., Yoda E., Komiyama M., Chem. Eng. Sci., 109, 197 (2014).2) Nguyen H.T., Lu H., Kobayashi E., Ishikawa T., Komiyama M., Topics Catal., in press.

Catalyst activity and deactivation characteristics in supercritical water gasification of <i>Chlorella vulgaris</i>

248th National Meeting (2014)

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Catalyst activity and deactivation characteristics in supercritical water gasification of Chlorella vulgaris