The reaction of methanol with unsaturated C5 isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) produces TAME. The liquid-phase reversible reactions are
This system is fundamentally a ternary system with inerts. The methanol fresh feedstream is essentially pure. The hydrocarbon feed comes from an upstream catalytic cracking unit. It is a mixed C5 stream that contains not only the two reactants (2M1B and 2M2B) but also other C5s such as isopentane, n-pentane, 1-pentene, and 2-pentene.
Reactive Distillation Design and Control. By William L. Luyben and Cheng-Ching Yu Copyright # 2008 John Wiley & Sons, Inc.
The heavy component is TAME, which leaves the reactive distillation column in the bottoms. The lighter C5 components leave in the distillate stream and take with them a significant amount of methanol that is tied up in the C5-methanol azeotropes. For example, the iC5/methanol azeotrope contains 25 mol% methanol at a pressure of 4 bar with a temperature of 376 K.
The process flowsheet has a prereactor, a reactive distillation column, and a methanol recovery section. The system is simulated in Aspen Plus using UNIFAC physical properties. Figure 14.1 presents the flowsheet with steady-state design conditions and equipment sizes. This flowsheet is slightly modified from that given in Chapter 8. A decanter is used for the reflux drum in extractive distillation column C2. Water is used as the extractive agent in this column. A significant amount of water goes overhead and forms an aqueous liquid phase. The organic phase is mostly inert C5 that comes in with the fresh feedstream (816kmol/h). The aqueous phase (35 kmol/h) is 99.71 mol% water and 0.1 mol% methanol.
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