Furfural, a biomass-derived platform chemical, was produced by acid-catalyzed reaction of alginic acid extracted from brown seaweed. Three acid catalysts, H2SO4, Amberlystl5 and 12-tungstophosphoric acid (H3PW12O40), were compared to evaluate their catalytic performance for the alginic acid conversion. The H3PW12O40 catalyst showed the highest catalytic activity, yielding the maximum furfural yield (33.8%) at 180 degrees C for 30 min in tetrahydrofuran/water co-solvent. Higher reaction temperature promoted the conversion of alginic acid to furfural, but the transformation of furfural to humin was also accelerated. To our knowledge, this is the highest furfural yield among studies about the direct catalytic conversion of alginic acid. Furthermore, products distribution with time-on-stream was investigated in detail, which led us to propose a reaction pathway. (C) 2016 Elsevier Ltd. All rights reserved.