The invention discloses a preparation method of a mesoporous-microporous composite
molecular sieve. The preparation method comprises the following steps of adding a microporous
molecular sieve subjected to
hydrothermal treatment into a mixed
system of a
silicon source, an acid solution and a surfactant, then carrying out
crystallization,
filtration and washing, and then carrying out
drying and
calcination to obtain the mesoporous-microporous composite
molecular sieve. The preparation method fully utilizes non-framework aluminum falling from the microporous molecular
sieve, avoids an aluminum source used by the conventional molecular
sieve preparation technology, is conducive to improvement of a silica-
alumina ratio of the mesoporous-microporous composite molecular
sieve, realizes a high degree of
crystallization, and improves hydrothermal stability and
thermostability of the mesoporous-microporous composite molecular sieve. The mesoporous-microporous composite molecular sieve is suitable for the field of
macromolecule catalysis, is conducive to improvement of a reaction conversion ratio and reaction selectivity, and is especially suitable for being used in a
cracking catalyst for maximum-degree production of middle distillate from heavy oil as a
raw material.