A process for etherifying iso-olefins, comprising - feeding a fresh olefinic hydrocarbon feedstock, containing at least one isoolefin selected from the group of tertiary C 4-7 olefins, to a reactor train system including - at least one primary reaction zone, - at least one primary distillation zone connected to an effluent outlet of the primary reaction zone, - at least one sidedraw being circulated from the primary distillation zone to the primary reaction zone to recycle unreacted olefins and alkanol, - at least one secondary reaction zone connected to an overhead draw of the distillation zone, and - at least one secondary distillation zone connected to an effluent outlet of the secondary reaction zone, - contacting said olefinic hydrocarbon feedstock in the primary reaction zone with an acidic catalyst in the presence of alkanol, the mole ratio of alkanol-to-olefin being 0.7 to 2, calculated from the amount of tertiary C 4-7 olefins of the fresh feedstock, at conditions in which at least a part of the olefins are etherified to produce a first reaction mixture containing etherified isoolefins, unreacted olefins and alkanol, - conducting an effluent comprising said first reaction mixture from said primary reaction zone to said primary distillation zone, where at least a part of the etherified isoolefins is separated from said effluent, - withdrawing at least one flow comprising unreacted olefins and alkanol from the side of the primary distillation zone and circulating said flow from said distillation zone back to the primary reaction zone, - conducting the overhead of the primary distillation zone, comprising unreacted components of the feedstock, including alkanol and isoolefins, to the secondary reaction zone, - contacting said unreacted isoolefins in the secondary reaction zone with an acidic catalyst in the presence of an alkanol at conditions in which at least a part of the isoolefins are etherified to produce a second reaction mixture containing etherified isoolefins, - conducting an effluent comprising said second reaction mixture from the secondary reaction zone to the secondary distillation zone, where at least a part of the etherified isoolefins are separated from said effluent, and - recovering etherified isoolefins, further comprising - decomposing at least a part of the etherified isoolefins of the product so as to form the corresponding alkanol and isoolefin, at least a part of the alkanol being recycled to the reactor train system and at least part of the isoolefin(s) being recovered and stored separate from any converted isoolefins. - feeding a fresh olefinic hydrocarbon feedstock, containing at least one isoolefin selected from the group of tertiary C 4-7 olefins, to a reactor train system including - at least one primary reaction zone, - at least one primary distillation zone connected to an effluent outlet of the primary reaction zone, - at least one sidedraw being circulated from the primary distillation zone to the primary reaction zone to recycle unreacted olefins and alkanol, - at least one secondary reaction zone connected to an overhead draw of the distillation zone, and - at least one secondary distillation zone connected to an effluent outlet of the secondary reaction zone, - at least one primary reaction zone, - at least one primary distillation zone connected to an effluent outlet of the primary reaction zone, - at least one sidedraw being circulated from the primary distillation zone to the primary reaction zone to recycle unreacted olefins and alkanol, - at least one secondary reaction zone connected to an overhead draw of the distillation zone, and - at least one secondary distillation zone connected to an effluent outlet of the secondary reaction zone, - contacting said olefinic hydrocarbon feedstock in the primary reaction zone with an acidic catalyst in the presence of alkanol, the mole ratio of alkanol-to-olefin being 0.7 to 2, calculated from the amount of tertiary C 4-7 olefins of the fresh feedstock, at conditions in which at least a part of the olefins are etherified to produce a first reaction mixture containing etherified isoolefins, unreacted olefins and alkanol, - conducting an effluent comprising said first reaction mixture from said primary reaction zone to said primary distillation zone, where at least a part of the etherified isoolefins is separated from said effluent, - withdrawing at least one flow comprising unreacted olefins and alkanol from the side of the primary distillation zone and circulating said flow from said distillation zone back to the primary reaction zone, - conducting the overhead of the primary distillation zone, comprising unreacted components of the feedstock, including alkanol and isoolefins, to the secondary reaction zone, - contacting said unreacted isoolefins in the secondary reaction zone with an acidic catalyst in the presence of an alkanol at conditions in which at least a part of the isoolefins are etherified to produce a second reaction mixture containing etherified isoolefins, - conducting an effluent comprising said second reaction mixture from the secondary reaction zone to the secondary distillation zone, where at least a part of the etherified isoolefins are separated from said effluent, and - recovering etherified isoolefins, further comprising - decomposing at least a part of the etherified isoolefins of the product so as to form the corresponding alkanol and isoolefin, at least a part of the alkanol being recycled to the reactor train system and at least part of the isoolefin(s) being recovered and stored separate from any converted isoolefins.