Device and process for the conversion of a feedstock of aromatic compounds, in which the feedstock is treated notably by means of a fractionation train (4-7), a xylene separation unit (10) and an isomerization unit (11), and in which a pyrolysis unit (13) treats a second hydrocarbon feedstock, produces a pyrolysis effluent feeding the feedstock, and produces a pyrolysis gas comprising CO, CO2 and H2; a reverse water gas shift RWGS reaction section (50) treats the pyrolysis gas and produces an RWGS gas enriched in CO and in water; a fermentation reaction section (52) treats the RWGS gas enriched in CO and in water, to produce ethanol and recycle the ethanol to the inlet of the pyrolysis unit.