the present invention relates to a method for preparing linear alpha olefin comonomers , such as 1 - butene , 1 - hexene or 1 - octene , from ethylene monomer . the comonomer generated is stored on site for use in a subsequent process , such as a polyethylene polymerization reactor . the method includes the steps of feeding an ethylene monomer , and a catalyst in a solvent to one or more comonomer synthesis reactors ; reacting the ethylene monomer and the catalyst in solvent under reaction conditions to produce an effluent stream comprising unreacted ethylene monomer , a catalyst in a solvent , and comonomer ; passing the effluent stream to one or more downstream gas / liquid phase separators to form a gas stream of unreacted ethylene monomer , and a liquid stream of comonomer , and catalyst in a solvent ; recycling to the one or more comonomer synthesis reactors the unreacted ethylene monomer and a portion of the liquid stream ; and storing a remaining portion of said liquid stream for subsequent processing of the comonomer . some of the benefits of the method include process simplification and reduced capital and operating costs from , inter alia , not having to recover ethylene in high purity nor separate catalyst from comonomer .