Selective Homologation Routes to 2,2,3-Trimethylbutane on Solid Acids

摘要

2,2,3-Trimethylbutane (triptane) is a valuable fuel additive with a research octane number of 112. It can be produced with high selectivity from methanol (or dimethyl ether (DME)) using solutions of Zn or In halides at approximately 473 K, via steps that seem to involve carbocationic inter-mediates. Inhibition by H2O formed by methanol dehydration, however, limits reactions to a few methanol turnovers (ca. 4) and only around one triptane molecule formed per ZnI2. Acid-catalyzed homologation of meth-anol/DME also occurs on zeolites but at higher temperatures (> 573 K) and forms alkanes, alkenes, and arenes in near-equilibrium isomer distributions, as well as unreactive carbon-containing deposits that cause catalyst deactivation.