HUSY zeolite modified by lanthanum: Effect of lanthanum introduction as a vanadium trap

The use of lanthanum as a vanadium trap in USY-based catalysts was studied. Lanthanum was introduced in a HUSY zeolite by different methods: impregnation, precipitation and ionic exchange. Catalysts were characterized by means of XRD, XPS, FTIR, TEM and textural properties (surface-area and microporous volume). The catalysts were also tested in the catalytic reactions of 2-propanol dehydration and n-hexane cracking. The prevention of zeolite damage caused by vanadium depended on the lanthanum localization in the zeolite, which in turn was a function of the method of lanthanum introduction. Samples prepared by precipitation predominantly showed lanthanum species on the zeolite surface. On the other hand, when ionic exchange was used for the lanthanum introduction, it was located in the zeolite channels and cavities. The impregnation method produced a catalyst in which lanthanum was distributed on the zeolite surface but also in the channels and cavities and this catalyst showed a high tolerance to the vanadium presence, lower zeolite damage in steaming and less amount of acid sites poisoned by vanadium.