Modified Y-type molecular sieve, catalytic cracking catalyst comprising the same, their preparation and application thereof

A modified Y-type molecular sieve, having a rare earth content of about 4% to about 11% by weight on the basis of the oxide, a phosphorus content of about 0.05% to about 10% by weight on the basis of P2O5, a sodium content of no more than about 0.5% by weight on the basis of sodium oxide, a gallium content of about 0.1% to about 2.5% by weight on the basis of gallium oxide, and a zirconium content of about 0.1% to about 2.5% by weight on the basis of zirconia, based on the weight of the modified Y-type molecular sieve on a dry basis,

• wherein the modified Y-type molecular sieve has a total pore volume of about 0.36 mL/g to about 0.48 mL/g, a percentage of a pore volume of secondary pores having a pore size of 2-100 nm relative to the total pore volume of about 20% to about 40%,
• a lattice constant of about 2.440 nm to about 2.455 nm, a lattice collapse temperature of not lower than about 1060° C., a percentage of non-framework aluminum content to the total aluminum content of no more than about 10%, and a ratio of B acid to L acid in the strong acid content of the modified Y-type molecular sieve of no less than about 3.5.