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Presidential Green Chemistry Challenge: 1998 Greener Reaction Conditions Award

Argonne National Laboratory


Novel Membrane-Based Process for Producing Lactate Esters—Nontoxic Replacements for Halogenated and Toxic Solvents


Innovation and Benefits: Argonne developed a novel process to synthesize organic solvents from sugars. These solvents can replace a wide variety of more hazardous solvents, such as methylene chloride. Argonne's process requires little energy, is highly efficient, eliminates large volumes of salt waste, and reduces pollution and emissions. These solvents can potentially replace 7.6 billion pounds of toxic solvents used annually by industry, commerce, and households.

Summary of Technology: Argonne National Laboratory (ANL) has developed a process based on selective membranes that permits low-cost synthesis of high-purity ethyl lactate and other lactate esters from carbohydrate feedstock. The process requires little energy input, is highly efficient and selective, and eliminates the large volumes of salt waste produced by conventional processes. ANL's novel process uses pervaporation membranes and catalysts. In the process, ammonium lactate is thermally and catalytically cracked to produce the acid, which, with the addition of alcohol, is converted to the ester. The selective membranes pass the ammonia and water with high efficiency while retaining the alcohol, acid, and ester. The ammonia is recovered and reused in the fermentation to make ammonium lactate, eliminating the formation of waste salt. The innovation overcomes major technical hurdles that had made current production processes for lactate esters technically and economically noncompetitive. The innovation will enable the replacement of toxic solvents widely used by industry and consumers, expand the use of renewable carbohydrate feedstocks, and reduce pollution and emissions.

Ethyl lactate has a good temperature performance range (boiling point: 309 °F, melting point: 104 °F), is compatible with both aqueous and organic systems, is easily biodegradable, and has been approved for food by the U.S. Food and Drug Administration (FDA). Lactate esters (primarily ethyl lactate) can replace most halogenated solvents (including ozone-depleting chlorofluorocarbons (CFCs), carcinogenic methylene chloride, toxic ethylene glycol ethers, perchloroethylene, and chloroform) on a 1:1 basis. At 1998 prices ($1.60–2.00 per pound), the market for ethyl lactate is about 20 million pounds per year for a wide variety of specialty applications. The novel and efficient ANL membrane process will reduce the selling price of ethyl lactate to $0.85–1.00 per pound and enable ethyl lactate to compete directly with the petroleum-derived toxic solvents currently in use. The favorable economics of the ANL membrane process, therefore, can lead to the widespread substitution of petroleum-derived toxic solvents by ethyl lactate in electronics manufacturing, paints and coatings, textiles, cleaners and degreasers, adhesives, printing, de-inking, and many other industrial, commercial, and household applications. More than 80 percent of the applications requiring the use of more than 7.6 billion pounds of solvents in the United States each year are suitable for reformulation with environmentally friendly lactate esters.

The ANL process has been patented for producing esters from all fermentation-derived organic acids and their salts. Organic acids and their esters, at the purity achieved by this process, offer great potential as intermediates for synthesizing polymers, biodegradable plastics, oxygenated chemicals (e.g., propylene glycol and acrylic acid), and specialty products. By improving purity and lowering costs, the ANL process promises to make fermentation-derived organic acids an economically viable alternative to many chemicals and products derived from petroleum feedstocks.

A U.S. patent on this technology has been allowed, and international patents have been filed. NTEC, Inc. has licensed the technology for lactate esters and provided the resources for a pilot-scale demonstration of the integrated process at ANL. The pilot-scale demonstration has produced a high-purity ethyl lactate product that meets or exceeds all the process performance objectives. A 10-million-pound-per-year demonstration plant is being planned for early 1999, followed by a 100-million-pound-per-year, full-scale plant.

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