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Continuous Anisole Process Flowsheet

A comprehensive flowsheet for anisole (methoxybenzene) was developed as part of a clinic project in conjunction with Rowan University. A summary of this work was presented by Ms. Kerri Shramm at the Fall 2002 AIChE meeting in Indianapolis. The process was modeled in detail on an Excel® spreadsheet and heat and material balances were determined for all components. Kinetic data was supplied by Value Recovery and the mass balance around the phase split was determined from data available in the literature. The thermodynamic calculations supporting the flash separations were modeled on HISYS assuming a one phase flash with simplifying assumptions for water in the vapor.

The feeds to the process are water, phenol, methyl chloride (or bromide) and catalyst. The phenol must be reacted with base prior to entering the system to make sodium phenolate. In most cases, phenol is already present as the phenolate. The CSTR (continuous stirred tank reactor) runs under pressure with an excess of methyl chloride to exhaustively react out all of the phenolate and keep the reactor to one vessel. The methyl chloride is recycled through a flash separation step that also recycles some water and anisole product. The two phase bottoms from the flash step is fed to a phase split step which produces an aqueous rafffinate and an organic stream that contains catalyst, anisole and some small amount of methyl chloride. Since the catalyst is a high boiler, this stream is also flashed at a pressure lower than the methyl chloride flash. Anisole and a small amount of methyl chloride go into the vapor phase and on to the partial condenser that condenses the anisole product and allows the residual methyl chloride to be recycled. The catalyst bottoms is recycled back to the front of the process. Some small amount of catalyst needs to be purged due to let catalyst byproducts out of the process. Work is ongoing to quantify the catalyst losses. The limited data presented in the literature plus our own observations put this at a negligible amount. Catalyst is recycled to the front of the process. As mentioned earlier, variations on this theme are possible with the other combinations of alkyl and acyl halides and water soluble anions. The critical factor in developing flowsheets for other processes is the volatility of the organic feed and the reaction rate in the CSTR.

An economic analysis done by Mr. Ken Battle, Director of Technology for Day & Zimmerman, has put the cost of a plant making 1.3 million lbs/yr of anisole at $1.1 million. Based on the selling price of anisole and cost avoidance from hazardous waste treatment we expect a capital recovery in 12 to 18 months. More detail on the mass balances, kinetics and economics of this process and others are available upon execution of a confidentiality agreement.)

In a similar fasion, a process for making methyl or ethyl acrylate from acrylic acid in water is also possible and details for an economic analyis are available. To obtain this information we will need data on your acrylic acid stream and execution of our standard confidentiality agreement.

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