Abstract: The invention relates to a catalyst for isomerization of a C8 aromatic cut containing a mordenite characterized in that said mordenite contains at least one metal of groups IIa, IVb, IIb or IVa and is such that:its overall Si/Al atomic ratio is between 6 and 15,its sodium content by weight relative to the weight of dry mordenite is less than 2000 ppm,its elementary mesh volume is between 2.725 and 2.785 nm.sup.3,its n-hexane adsorption capacity is greater than 0.065 cm.sup.3 of liquid/gram,its isooctane adsorption capacity is less than 0.068 cm.sup.3 of liquid/gram.The invention also relates to the preparation of this mordenite by grafting on an H-shaped mordenite of at least one organometallic compound of said metal.

Abstract: The invention relates to a catalyst for isomerization of a C8 aromatic cut containing a mordenite characterized in that said mordenite contains at least one metal of groups IIa, IVb, IIb or IVa and is such that:its overall Si/Al atomic ratio is between 6 and 15,its sodium content by weight relative to the weight of dry mordenite is less than 2000 ppm,its elementary mesh volume is between 2.725 and 2.785 nm.sup.3,its n-hexane adsorption capacity is greater than 0.065 cm.sup.3 of liquid/gram,its isooctane adsorption capacity is less than 0.068 cm.sup.3 of liquid/gram.The invention also relates to the preparation of this mordenite by grafting on an H-shaped mordenite of at least one organometallic compound of said metal.

Abstract: Improved process of metathesis of olefins by contact of one or more olefins with a catalyst comprising a tungsten complex with two phenoxy groups, carrying substituents and four other ligands, the complex carrying as coordination groups a halogen atom, an alkyl radical and a carbene. The catalyst preferably is of the formula ##STR1## where X is halogen, R is hydrocarbon or an electronegative group or atom, R.sup.1 is alkyl and R.sup.2 and R.sup.3 are individually hydrogen or alkyl groups.