The thermodynamic equilibrium of the bimolecular dehydration of 1-butanol to di-n-butyl ether (DNBE) and water in the liquid phase was studied. Equilibrium experiments were performed at 4 MPa and in the temperature range of 413-463 K over the ion exchange resin Amberlyst-70.The thermodynamic equilibrium for the side reactions (dehydration to 1-butene, olefins isomerization, olefins hydration and branched ether formation) was also studied. The equilibrium constant for the dehydration reaction of 1-butanol to di-n-butyl ether and water was found to be independent of the operating temperature, within the limits of the experimental error