Using butenes to fractionate methanol from methyl-tertiary-butyl ether

Claim 1

A process for the production of a substantially pure MTBE stream which comprises: (a) feeding methanol and isobutene to an MTBE reactor means, (b) reacting in said MTBE reactor means methanol with isobutene under reaction conditions under liquid phase conditions employing an ion exchange resin catalyst, thereby producing a reaction stream comprising unreacted methanol, unreacted isobutene, and MTBE, (c) feeding added n-butenes to a fractionation means, (d) feeding said reaction stream to said fractionation means, (e) fractionating in fractionating means said reaction stream with said added n-butenes, and taking an overhead vapor stream comprising unreacted isobutene and an azeotrope of said n-butenes with said unreacted methanol, wherein said n-butenes are present in an amount effective to take unreacted methanol overhead as an azeotrope, thereby producing substantially pure MTBE as liquid bottoms, (f) withdrawing a sample stream from said fractionation means said sample stream taken from said fractionation means below the input of said reaction stream and above the outlet of said bottoms stream, (g) monitoring the methanol content of said sample stream and generating a signal in response to the methanol content thereof, (h) controlling the addition of said added n-butenes in said step (c) to said fractionation means in response to said signal, whereby said signal controls the increase or decrease of addition of said added n-butenes, thereby maintaining an effective level of said n-butenes in said fractionation means to maintain substantially methanol-free bottoms.