In one exemplary embodiment, a system for reacting a first feed can include a petroleum fraction having at least about 90%, by volume, with a boiling point of at least about 300° C. The system can include a bubble column reactor. The bubble column reactor, in turn, can include a first inlet for the first feed and a second inlet for a second feed including a gas rich in hydrogen. In addition, the petroleum fraction may be in counter-current flow with respect to the gas rich in hydrogen inside the bubble column reactor.