The invention relates to a modification method for a USY
molecular sieve and in particular relates to a combined modification method for a mesopore USY
molecular sieve. The combined modification method for the mesopore USY
molecular sieve comprises that raw materials such as a USY material, an
organic acid solution and an inorganic
salt solution are measured in ratio, stirring in a closed reactor is carried out, temperature is increased to 90 DEG C, an
organic acid-inorganic salt combined dealumination reaction is carried out for 8 hours; reactants are washed at
room temperature, and suction
filtration is carried out until the surface of USY is neutral; and
drying is carried out at constant temperature of 110 DEG C for 16 hours, so that the USY molecular
sieve product is obtained. The combined modification method for the mesopore USY molecular
sieve has the advantages that a mixed
aqueous solution of
organic acid and inorganic salt is adopted for treating the USY type molecular
sieve, so that high
crystallinity of the molecular sieve can be maintained, silica-
alumina ratio of the molecular sieve is increased,
lattice constant is reduced, specific surface of the molecular sieve is increased, and acidity and acid distribution of the molecular sieve are improved; and more secondary holes are formed through dealumination, so that components with larger molecular
diameter can easily enter into pore passages of the molecular sieve or get close to the surface of the molecular sieve, and conversion efficiency of
hydrogen cracking can be improved.