Ethers, particularly methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME), have long been used in reformulated gasoline, owing to their attractive blending and engine burning characteristics. Although in North America ethers are being removed gradually from the gasoline pools, they remain the additives of choice in other regions not having groundwater contamination issues.
Another approach now viewed as an option for sustainable development is to add ethanol to gasoline pools. However, direct blending of ethanol in the gasoline pool gives rise to potential problems such as increased Rvp, volume reduction, phase separation and logistics (mixing at terminals). Indirect incorporation of ethanol via the etherification routes producing ethyl tertiary butyl ether (ETBE) or tertiary amyl ethyl ether (TAEE) is an interesting option for sustainable gasoline production as these materials boast excellent blending and engine burning properties. Pioneered by IFP in the 1990s, these processes complement Axens’ technology strategy for providing high-quality reformulated and renewable fuels.
Besides, Axens offers a full set of technologies to produce high-purity, polymer-grade butene-1 from cracked C4s, which involves selective hydrogenation of butadiene, purification stages, high-conversion MTBE and butene-1 superfractionation.
Our experience includes the design and operation of a large number of units since the 1980s. At present, more than 30 units are in operation worldwide. Design configurations applicable to all units include:
• Main reaction section where the major part of the reaction takes place on an acidic catalyst. Fixed-bed reactors or expanded bed reactors may be used depending upon operating severity.
• Fractionation section for separating unconverted raffinate from produced ethers. This separation column may be filled with several beds of conventional etherification catalyst to allow thermodynamic equilibrium and increase conversions. This reactive distillation concept is called Catacol and is well-suited for ethers production maximization or isobutylene extinction (99.9%+ conversion) when locating a MTBE unit upstream
of a butene-1 recovery section.
• Alcohol recovery section consisting of a raffinate washing column and alcohol recovery column for recycling unconverted alcohol to the main section to improve reaction selectivity. This is optional in the ethanol mode.