Modified Y-type molecular sieve, catalytic crack catalyst comprising the same, their preparation a

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A modified Y-type molecular sieve has 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, and an active element content of about 0.1% to about 5% by weight on the basis of the oxide, with the active element being gallium and/or boron. 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 the pore volume of secondary pores having a pore size of 2-100 nm of about 20% to about 40%; a lattice constant of about 2.440 nm to about 2.455 nm, and a lattice collapse temperature of not lower than about 1060° C.