The present invention relates to a process and a device for the conversion of aromatic compounds, in which the aromatic compounds of a hydrocarbon feedstock (1) comprising aromatic compounds containing 9 carbon atoms are isomerized in an isomerization unit (A) in the presence of a bifunctional isomerization catalyst having a hydro/dehydrogenating function and a hydroisomerizing function, to produce an isomerization effluent (10) enriched in trimethylbenzenes. The present invention also relates to a process and a device for the production of aromatic compounds, comprising the process and the device for the conversion of aromatic compounds.