Two series of unsupported CoMgMoAl hydrotreating catalysts were prepared starting from CoMgAl-terephthalate layered double hydroxides (LDHs) with nominal aluminum molar fractions (Al/(Al + Ni +Mg) ratios) 0.3 (A130 series) and 0.5 (A150 series), and nominal cobalt atom fractions (Co/(Co + Mg)) in the 0.2-1.0 range in each series. The materials were prepared by ion exchange with ammonium heptamolybdate, followed by calcination at 723 K. Mixed oxides containing ca. 14-32 wt.% molybdenum and Ni/Mo atomic ratios in the 0.5-1.6 range were obtained. Despite the observed loss in long-range ordering and, in some cases, magnesium leaching during the ion-exchange, there was evidence that molybdenum-intercalated LHDs were indeed produced. The catalysts were sulfided in situ and subsequently tested in simultaneous thiophene HDS and cyclohexene hydrogenation (OHYD reaction) in a tubular flow micro-reactor at 573 and 623K and 20 bar. In each series, both the HDS and the OHYD activities of the catalysts increased with increasing Mg content, possibly due to improved Co/Mo ratio. Although there was a trend of decreasing selectivity for the HDS reaction with increasing HDS activity, the HDS selectivity of the most active catalysts was higher than that of a commercial alumina-supported CoMo catalyst. (C) 2014 Elsevier B.V. All rights reserved.