Four FCC catalysts were compared in a CREC Riser Simulator reactor using an aromatic Brazilian VG feed aiming at maximum low aromatic middle distillate production. Differences in activity were compensated by changes in the contact time. The first catalyst (A) was a maximum LCO commercial grade, the other three being experimental catalysts, including a pair of related materials in which one of the catalysts (M2) was produced by modulating the acidity of the other one (M1). Inert non porous silica was evaluated as a thermal cracking reference. The four catalysts were characterized as tested using temperature-programmed desorption of n-propylamine to determine their Bronsted acidity. The commercial catalyst A was by far the most acidic catalyst, followed by catalyst M1. Bronsted acidity of the two other catalysts M2 and B was about one tenth the value of catalyst A. Lowering the Bronsted acidity reduced catalyst activity, but it was possible to recover conversion by increasing reaction time, which was not the case with the thermal cracking reference. The yields of light naphtha and of aromatic hydrocarbons in the C10 and C11 range (inversely correlated to LCO Cetane) of the low acidity catalysts B and M2 was reduced by 30% and 50% respectively and LCD (C12 to C20 hydrocarbons) was increased by 33%, compared to catalyst A at the same slurry oil yield. (C) 2011 Elsevier B.V. All rights reserved.