A two-step procedure for separating isobutene from mixed C4 hydrocarbon streams, such as Raffinate-1, has been demonstrated using solid acid catalysis. The procedure involves initial etherification of the C4 mixture with a suitable aliphatic diol, such as ethylene glycol or 1,2-propylene glycol, to give the corresponding glycol mono-t-butyl ethers, followed by deetherification of the said monoethers at higher temperatures to yield pure isobutene plus regenerated glycol. Suitable classes of solid acid catalysts include acidified montmorillonite clays and heteropoly acids dispersed on Group IV oxides, such as 12-tungstophosphoric acid on titania. Preliminary etherification parameter, and catalyst characterization, studies for these two very different classes of strongly acidic catalyst are also detailed herein.