Process Studied

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.

Extractive Distillation Flowsheet
Figure 14.1 Flowsheet for TAME process with extractive distillation methanol recovery.

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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