A series Of Mo2C catalysts have been investigated for the hydrogenation showed no selectivity for ring-opening products (ROP) and, although treating the bulk catalysts in oxygen increased stability and naphthalene conversion, ROP selectivity remained low. Supporting the Mo2C on HY zeolites significantly increased the hydrogenation of naphthalene and the subsequent formation of ROP, as compared to the HY zeolites alone or the bulk materials. ROP yields were dependent upon the HY zeolite SiO2:Al2O3 ratio and the Mo2C loading, the optimum loading being dependent upon the zeolite acidity. The maximum ROP yield of 33 wt.% was obtained with 7.4 wt-% Mo2C supported on HY zeolite of moderate acidity (SiO2:Al2O3 ratio of 12) and the yield is comparable to yields reported for noble metal catalysts on acidic supports. The Mo2C/HY zeolite bifunctional catalysts are most effective for ring opening of naphthalene when the acidity is adjusted to an intermediate level that limits deactivation and the Mo2C loading provides sufficient hydrogenation capability to achieve high conversion to the primary product tetralin. (C) 2007 Elsevier B.V. All rights reserved.