The title ether was synthesised using a single-pass trickle-bed reactor, over the ion-exchange resin catalyst Amberlyst 15, between 80 degrees C and 140 degrees C and 1 and 70 bar from a feed of propylene and water. Varying contact time experiments showed isopropanol to be the primary product in the reaction and diisopropyl ether the secondary product. Ln both the liquid and vapour phase, diisopropyl ether is formed by one of the two parallel, competing reactions: from the etherification reaction of isopropanol with propylene or from the dehydrative etherification of isopropanol. Apparent activation energies of 92 and 75 kJ mol(-1) were measured for the hydration and etherification reactions, respectively. A linear dependence of rate on pressure was found. The Peng-Robinson-Stryjek-Vera equation of state together with the Wong-Sandler mixing rule was used to model the vapour-liquid behaviour of the system. For highest yield, diisopropyl ether synthesis should take place at high pressure and sufficiently high temperature to overcome the kinetic Limitations.