The invention discloses a preparation method of pseudo-
boehmite with high purity and high
crystallization degree. The method comprises the following steps: (1)
bottom water is added into a pressure zone and a
reaction zone of a reactor, and a stabilizing agent is added into water in the
reaction zone; (2) an
aqueous solution of
aluminium salts and an alkaline solution are respectively injected into a feed inlet I and a feed inlet II at the upper part of the
reaction zone of the reactor, a
sol forming reaction is carried out, during the
sol forming reaction process, when
aluminium hydroxide sol reaches a certain concentration, a pressure pump pumps water in the pressure zone into a reaction zone through a semi-permeable membrane, the sol is kept in a concentration range, and the reaction is continuously carried out for a period of time; (3) after the reaction ends, a stirring
paddle at the bottom of the reactor is started, pH value of the reactor is adjusted, temperature is rapidly raised to an aging temperature, after aging, filtering, washing and
drying are carried out, the pseudo-
boehmite is obtained. The pseudo-
boehmite is prepared by a semi-permeable
membrane penetration mode, and the obtained pseudo-boehmite has the advantages of high purity, high
crystallization degree, and uniform
particle size distribution; and the pseudo-boehmite is suitable for preparing carriers and catalysts of hydrotreatment catalysts for
wax oil, heavy oil and other inferior raw materials.