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.