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.