Disclosed is a process for integrating a butene dimerization process with a metathesis process to remove isobutene from the feed stream to the metathesis reactor. The isobutene is preferentially dimerized in the dimerization process to leave n-butenes for metathesis with ethylene. An upstream selective hydrogenation process also isomerizes 1-butenes to 2-butenes which is the preferred butene reagent in the metathesis process. A common fractionator column for the dimerization and hydrogenation processes is also described.