Methyl tert-butyl ether synthesis from tert-butanol via inorganic solid acid catalysis

Three classes of inorganic solid acid catalyst have been demonstrated to be effective for methyl tert-butyl ether (MTBE) syntheses from methanol/fert-butanol (TBA) feed mixtures using a continuous, plug-flow, reactor system. These catalysts include heteropoly acids, such as 12-tungstophosphoric acid and 12-molybdophosphoric acid, on Group III and IV oxide supports, such as titania, HF-treated montmorillonite clays, as well as mineral acid-activated clays. Changes in the structure of the 12-tungstophosphoric acid-on-titania during etherification service have been investigated using 31P and 1H MAS NMR. An unexpected, in situ, phase separation of the desired MTBE plus isobutene products from aqueous methanol has been observed at high (>80%) tert-butanol conversion levels and operating temperatures greater than or equal 160°C. Milder etherification conditions allow MTBE selectivites to 94 mol% and sustained etherification activity for the HF/clay catalyst even with crude TBA feedstocks. © 1999 Elsevier Science B.V. All rights reserved.