Catalyst with an omega zeolite base, containing at least one group IIA, IVB, IIB or IVA metal, and use thereof in the isomerization of an aromatic C8 cut

A process for isomerisation of a C.sub.8 aromatic cut at a temperature of between 270.degree. C. and 600.degree. C., a pressure of 0.5 to 100 bars, a spatial speed of charge per unit of charge of catalyst and per hour of between 0.5 and 200 and a H.sub.2 /hydrocarbon molar ratio of between 0.5 and 12, in which process a catalyst is used which has an omega zeolite base and which contains a matrix, at least one group VIII metal and an omega zeolite containing at least one metal selected from group IIa, IIb, IVa and IVb metals and such that:

• its global Si/Al atomic ratio is between 1.5 and 100,
• its content by weight of sodium in relation to the weight of dry omega zellite is less than 2000 ppm,
• the metal(s) is/are deposited on the omega zeolite by grafting with at least one organometallic compound of said metal(s).