Continuous process for metallocene preliminary polymerization for gas-phase polymerization process

A process for preliminary polymerization may include washing a catalyst mud comprising a supported metallocene catalyst with at least one saturated hydrocarbon at a temperature from 0° C. to 40° C., a pressure from 20 to 40 kgf/cm2, and a residence time of at least 30 minutes; continuously feeding the washed catalytic mud to a continuous pre-polymerization reactor; and pre-polymerizing, in the continuous pre-polymerization reactor, ethylene and at least one C4 to C10 α-olefin as comonomer, with the washed catalytic mud, to produce a pre-polymer; wherein an average residence time in the continuous pre-polymerization reactor is more than 90 minutes and less than 240 minutes, a reactor temperature is from 10° C. to 50° C., and a reactor pressure from 20 to 40 kgf/cm2.