Eastman Chemical Company acetic anhydride process

The period from 1970 to 1985 saw radical changes in the production of acetic acid and acetic anhydride. By 1985, both products would be generated not from ethylene, but from synthesis gas which in turn could be generated fi om abundant resources such as coal, natural gas, and in the future, biomass. At the end of this period, acetaldehyde became a very small contributor to the total acetyl product stream since it was no longer required to make acetic acid or acetic anhydride and ethylene would only be required to produce vinyl acetate and to meet a much diminished acetaldehyde market. These advances were the result of two significant process breakthroughs - the Monsanto Acetic Acid Process and the Eastman Chemical Company Acetic Anhydride Process which will be discussed below. 

The Eastman Chemical Company Acetic Anhydride Process/ "... 

Eastman Chemical Company has operated a coal-to-methanol plant in Kingsport, Tennessee, since 1983. Two Texaco gasifiers (one is a backup) process 34 Mg/h (37 US ton/h) of coal to synthesis gas. The synthesis gas is converted to methanol by use of ICl methanol technology. Methanol is an intermediate for producing methyl acetate and acetic acid. The plant produces about 225 Gg/a (250,000 US ton/a) of acetic anhydride. As part of the DOE Clean Coal Technology Program, Air Products and Cnemicals, Inc., and Eastman Chemic Company are constructing a 9.8-Mg/h (260-US ton/d) slurry-phase reactor for the conversion of synthesis gas to methanol and dimethyl... 

The recovery of heavy metals from solid waste poses more challenges. The Eastman Chemical Company process for the manufacture of acetic anhydride by the carbonylation of methyl acetate involves a proprietary process for the continuous recovery of rhodium and lithium from the process tar (see Section 4.6). 

Eastman Chemical Company, together with Halcon, developed a commercial acetic anhydride process to an industrial scale [41b, 47]. This process starts with coal to make a hydrogen-rich synthesis gas, which is purified (Figure 4). A portion of the syn gas is separated to produce methanol from 2 1 H2/CO. Part of the methanol is used to scrub H2S from the coal-gasification step. The remainder of the methanol is combined with acetic acid to make methyl acetate. The methyl acetate is carbonylated to give acetic anhydride. The acetic anhydride is used to produce cellulose acetate in another process, and the resulting acetic acid is recycled to the esterification section. The acetic anhydride step of the pro-... 

On the basis of this development afforded by Eastman and Halcon, in 1983 the Eastman Chemical Company (Kingsport, TN) started the commercial process for the manufacture of acetic anhydride (Figure 5). Methyl acetate, the feedstock for the carbonylation reaction, was produced in a separate esterification step from acetic acid and methanol. The process was designed to produce 225 000 tons of acetic anhydride and 75 000 tons of acetic acid/year. The overall yield of acetic anhydride based on methanol is approximately 96 % [2, 47]. 

While the process was commercialized in 1983, Eastman Chemical Company and Halcon began a joint development of the Rh catalyzed carbonylation of methyl acetate to acetic anhydride in the late 1970 s. While the catalyst was similar to the Rh catalyst used in the Monsanto process, there were some unique challenges since (i) under anhydrous conditions the active catalyst, Rh(CO)2l2, failed to form, (ii) unlike water, acetic acid did not react with acetyl... 

One of the main uses of acetic anhydride is in the manufacture of cellulose acetate. Cellulose acetate is used in the production of plastics, coating chemicals, etc. Eastman Chemical Company has operated a highly successful rhodium-based acetic anhydride manufacturing process, based on the carbonylation of methyl acetate, for over 25 years. 

Because acetic anhydride is more useful to the chemical industry than acetic acid, there was economic incentive to develop a process that would yield the anhydride directly without first producing the acid as a separate operation. By the early 1980s, Eastman Chemicals, in conjunction with Halcon Chemical Company, developed a procedure that provided acetic anhydride using technology similar to the Monsanto process, and since 1991 a plant run by Eastman has produced anhydride in excess of 500,000 metric tons per year.89 The Eastman-Halcon (E-H) operation amounts formally to inserting CO into the C-0 bond of methyl acetate according to equation 9.36.90... 

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