Catalyst for isomerizing cuts of high normal paraffins content

In a process comprising hydroisomerizing a cut containing a large proportion of n-paraffins having 4 to 7 carbon atoms per molecule, said hydroisomerizing being conducted in contact with a catalyst, the improvement which comprises employing a catalyst whose basic constituent is a wide pore mordenite capable of adsorbing molecules of a kinetic diameter larger than about 0.66 nm, having a Si/Al atomic ratio from about 5 to 50, a sodium content lower than 0.2% by weight with respect to the total amount of the dry mordenite, a unit cell volume V of elementary mesh from 2.78 to 2.73 nm.sup.3, a benzene adsorption capacity higher than 5% by weight with respect to the weight of the dry mordenite, the mordenite being in major part of needle configuration.