Oxygenate fuels: Market expansion and catalytic aspect of synthesis

Periodical oil crises, environmental issues, and energy consumption optimisation brought oxygenated compounds into consideration as fuel additives with the role of enhancer and/or octane booster. Their progressive introduction into the fuel market is examined in the light of technical and legislative motivation. Their different roles played in the fuel formulation are recognised and their past, present and future importance is discussed here. Light alcohols and ethers offer different and specific advantages in meeting the clean fuel requirements. Methyl tert-butyl ether (MTBE) has been the preferred product up to now; positive future perspectives can be envisaged for the less volatile ethyl tert-butyl ether (ETBE) and methyl-tert amyl ether (TAME). A schematic oxygenate production pattern is reported allowing to clarify the complex integration of oxygenate manufacture with, natural gas, refinery and petrochemical. The main reactions involved are outlined. Alcohol addition to tertiary olefins appears to be a focal point in oxygenated production leading to alkyl tert-alkyl ethers (MTBE, ETBE, TAME). The industrial production of ethers started in 1972 in Italy and grew impressively: from 50,000 tons/year to about 30 million tons/year actually. Parallel to the industrial development fundamental studies were done to clarify the mechanism of reaction, the role and criteria of choice of catalysts. This review covers the thermodynamic, kinetic and catalytic aspects of the reaction. The results available in the Literature are referred, compared and discussed. (C) 1998 Published by Elsevier Science B.V. All rights reserved.