Methyl t-Butyl Ether (MTBE) Production: A Comparison of Montmorillonite-Derived Catalysts with an Ion-Exchange Resin

J. M. Adams, K. Martin, R. W. McCabe and S. Murray
Edward Davies Chemical Laboratories, University College of Wales Aberystwyth SY23 1NE, United Kingdom

Abstract: Montmorillonite-based catalysts were compared with an acidic ion-exchange resin of the type used industrially for the production of methyl t-butyl ether (MTBE) from methanol and isobutene or t-butanol. When 1,4-dioxan was used as solvent, Al3+-exchanged montmorillonites had about half the efficiency of the resin Amberlyst 15 at 60°C they were, however, about twice as efficient at this temperature at Ti3+-montmorillonite or K10, a commercially available acid-treated bentonite. Montmorillonite exchanged with Chlorhydrol solutions to give interlayer [Al13O4(OH)2(H2O)12]7+ ions and pillared clays derived from such materials were poor catalysts, as was K306, a more drastically acid-treated bentonite-based commercial catalyst. Freeze-drying of the Al3+-clay before reaction to produce a more open, porous structure had no effect on its catalytic efficiency. The activation energy for the reaction of isobutene and methanol in dioxan was 44 kJ/mole for an Al3+-clay catalyst compared with 25 kJ/mole for reactions catalyzed by Ambelyst 15. With no solvent (as in industrial processes), the rates of reaction were considerably slower for both the clay- and resin-catalyzed reactions. As has been found previously for resin-catalyzed reactions using stoichiometric amounts or an excess of methanol, the rate was proportional to the isobutene concentration, and the rate-determining step appeared to be protonation of the alkene. The performance of the Al3+-clay catalyst was increased by reducing the water content of the clay. In most reactions the clay catalysts were equilibrated at 12% relative humidity. Exposure of the clay to a low vacuum (10−1 torr) before use increased its catalytic activity from 50 to 60% of that of Amberlyst 15.

Key Words: Amberlyst 15 • Catalysis • Chlorhydrol • Ion-exchange resin • Methyl t-butyl ether • Montmorillonite

Clays and Clay Minerals; October 1986 v. 34; no. 5; p. 597-603; DOI: 10.1346/CCMN.1986.0340515
© 1986, The Clay Minerals Society
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