The catalytic pyrolysis of Laminaria japonica was carried out over four different microporous zeolite catalysts, HZSM-5 (SiO2/Al2O3 = 23, 80), HBETA (SiO2/Al2O3 = 25) and HY (SiO2/Al2O3 = 30). The effects of the catalysts on the properties of the resulting pyrolysis products were examined. Py-GC/MS (pyrolysis gas chromatography/mass spectrometry) was used to compare the composition of the bio-oils obtained from the non-catalytic and catalytic pyrolysis. Catalytic upgrading decreased the oil yield but increased the gas yield. The composition of bio-oil was changed to a large extent by catalytic upgrading. Among the oxygenate species contained in the bio-oil, the contents of 1,5-anhydro-d-mannitol and 1,4-anhydro-d-galacitol were reduced considerably by catalytic upgrading, whereas the proportions of furans and cyclopentanones were increased. The formation of high value-added aromatics was enhanced considerably by catalytic upgrading, which was attributed to the acid characteristics of the zeolite catalysts. HZSM-5 (SiO2/Al2O3 = 23), which had the strongest acid sites, showed the highest selectivity for aromatics production. (C) 2013 Elsevier Ltd. All rights reserved.