AM-97-45 NExETHERS - A NEW TECHNOLOGY FOR COMBINED MTBE, TAME AND HEAVIER ETHERS PRODUCTION

Description:

It is evident that the world is gradually shifting to more environmentally friendly motor fuels with no lead compounds tolerated as octane enhancers. The current target areas for lead elimination are Europe, Asia, parts of Africa and South America. The demand for clean burning motor gasoline has recently further increased the need for fuel oxygenates, since they are an important part of the equation for improving the quality of autom6tive fuels by increasing the overall octane content of the gasoline and reducing tailpipe emissions of CO and unburned hydrocarbons. Also, the requirement for limiting volatility of the gasoline pool favors oxygenate usage, since these compounds generally possess lower vapor pressures when compared with the iso-olefins from which they are derived. Production of MTBE was the original solution when lead compounds were first eliminated from fuel gasoline and components with high octane ratings were needed as a substitute. TAME is another recognized potential fuel ether, but with few exceptions the economics for TAME production have not been truly attractive. This is, however, changing now. Recently refiners have recognized the excellent properties of TAME when used in conjunction with MTBE. These two ethers clearly offer increased blending flexibility for volatility control, if available in a single site. ETBE, the ethanol based ether compound, remains a third alternative, although its production potential is limited by the price of the ethanol based feedstocks required. Neste was the first European oil company to start production and marketing of reformulated fuel gasoline (RFG). Properties of the Finnish RFG closely follow those specified in the Clean Air Act Amendments (CAAA) issued by the U.S. Environmental Protection Agency (EPA). When Finnish RFG is compared to fuel gasoline defined by Californian Air Resources Board (CARB), the differences are to be found in the vapor pressure and olefins content. Both are slightly higher in Finland. Production of RFG started in 1994 in two Neste operated refineries. At the beginning of year 1996 roughly 95% of the gasoline sold in Finland was reformulated. Neste has operated an MTBE unit in Porvoo refinery since 1981. The company has also played an active role in MTBE production by being a partner in several world scale MTBE plants. The Porvoo refinery unit made it partly possible to start full production of RFG. However, imported MTBE was required to fulfill the oxygen specification of 2 wt-%. In order to avoid this dependency on purchased blending material, a new process unit using proprietary NExTAME technology was built in Porvoo refinery in 1995. This unit produces significantly more captive oxygenates by etherifying also the isohexenes and isoheptenes present in FCC light gasoline in addition to TAME synthesis. The availability of these additional ether components combined with the output from the existing MTBE unit allowed manufacturing of RFG based on indigenous refining components.