FIELD: chemistry.
SUBSTANCE: method of modifying a Y-type zeolite catalyst with phosphorus involves: exchanging a crystallized catalyst with an ammonium salt to provide a sodium oxide content of less than about 2 wt % Na2O, treating the ammonium exchanged catalyst with the first phosphate solution, sufficient to add 0.5 to 2 wt % P2O5 to the catalyst, the ammonium ion exchange of the phosphorus-treated catalyst with the possibility of producing a catalyst with a low sodium oxide content, which is less than about 0.5 wt % Na2O, treating the catalyst with a low sodium oxide content with the second phosphate solution sufficient to provide a P2O5 content in the catalyst in the amount of 2-4 wt %, and the ion exchange of the catalyst for rare earth cations following the first ammonium ion exchange or after the first phosphorus treatment, with the possibility of including from 0.5 to 10 wt % of the rare earth elements in form of rare earth oxides in the composition of said catalyst, where, after the rare-earth exchange, the catalyst is calcined under calcination conditions, in which the size of the Y-type zeolite unit cell is not significantly reduced and where the said calcination is carried out in the absence of the additional vapour.
EFFECT: high hydrothermal stability and catalyst activity.
6 cl, 4 tbl, 7 ex
