Selective ring opening (SRO) is an attractive route for increasing the cetane number of diesel fuels. Noble metal-based catalysts have been proposed for this purpose. However, considering the type of processes producing diesel, more sulfur-resistant catalysts would be preferred for SRO. In the present study, we investigated the performance of bifunctional NiW sulfide catalysts supported onto amorphous silica alumina in gas-phase decalin hydroconversion at high hydrogen pressure (5 MPa) in the presence of 0.8% H2S concentration at 350-380 degrees C. Two-dimensional gas chromatography (GC x GC) was extensively employed to identify the reaction products and determine their distributions in the form of chemical families. The impact of acidity due to two different SiO2 contents (40 and 70 wt.%) in the support, as well as promoting the catalytic systems by P or F doping, were studied on the one hand. On the other hand, the improvement of the hydrogenation function by the use of chelating agents was investigated. Up to 17% in selectivity to ring-opening products was obtained. The reaction mechanism is shown to be mostly governed by the acidic function, which promotes the formation of skeletal-isomerization products, while the sulfide phase allows hydrogen activation. (C) 2015 Elsevier B.V. All rights reserved.