 |
 |
Office of Technology Transfer |
|
|
|
|
|
|
|
|
|
Frequently Asked Questions about Ethyl Lactate
What is the importance of Argonne's process?Argonne Laboratory 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. Lactate esters are nontoxic, biodegradable, and have excellent solvent properties that can replace toxic and halogenated solvents for a wide range of industrial and consumer uses. Until now they have been too expensive for widespread use. The Argonne process will enable the selling price of lactate esters to be cut in half, from about $1.60 - $2.00/lb to less than $1.00/lb. At such prices, it would be technically and commercially viable to use lactate esters in various formulations to replace of about 80% of the 3.8 million tons of solvents that are used in the United States each year. It could replace a range of environment-damaging halogenated and toxic solvents, including ozone-depleting chlorofluorocarbons, carcinogenic methylene chloride, and toxic ethylene glycol ethers and chloroform. The process is also generally applicable and has been patented (U.S. patent issued March 1998) for producing esters from various 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. The Argonne process, by improving purity and lowering costs, promises to make fermentation-derived organic acids an economically viable alternative to many chemicals and products derived from petroleum feedstocks. What problems does this innovation solve?The innovation overcame three major technical hurdles that had made current production processes for lactate esters technically and economically uncompetitive. In so doing, the innovation will enable the replacement of toxic solvents that are in major industrial and consumer use, expand the use of renewable carbohydrate feedstocks, and reduce pollution and emissions. Cation Elimination: The first technical hurdle was the problem known as "cation elimination." The lactic fermentation process produces a salt of the organic acid (such as ammonium lactate), rather than the acid, in a crude, impure broth. However, it is the purified acid that is required to produce esters or other lactic-acid-based products. The question of how to convert this salt directly to the acid without consuming an equivalent quantity of another acid and producing an equivalent quantity of waste salt has been the major technical challenge of "cation elimination." Water-splitting electrodialysis with bipolar membranes has been one way to achieve cation elimination. Argonne has previously developed and helped commercialize such electrodialysis processes for lactic acid and a variety of other process applications. Argonne's novel process, which is a direct 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 extreme efficiency while retaining the alcohol, acid, and the ester. The ammonia is recovered and reused in the fermentation to make ammonium lactate. Thus the formation of waste salt is eliminated. Contacting and Conversion: The second technical challenge is related to contacting and conversion. In the esterification process, the conversion is driven by removal of water. However, ethanol and other alcohols are more volatile than the water. In a conventional process, ethanol must be used in large excesses in the reactor, then distilled to remove the water with it, then dehydrated and returned for further conversion. Thus, the conventional process has large capital and energy requirements and also produces undesirable by-products because of incomplete conversions and high residence times. The new process keeps the alcohol in the reaction system while selectively removing the water. This leads to very high conversions, fast reaction rates, and fewer undesirable by-products. Purity: The third technical challenge is related to product purity. To be useful, the product esters have to be highly pure. The novel process, because of its high conversions and low levels of undesirable by-products, makes the separation of the reaction mixture very easy, and highly pure lactate esters are readily produced. By overcoming these technical challenges this novel process uses approximately one-tenth of the energy of the conventional process, eliminates the production of waste salt, and will enable the selling price of the esters to be lowered to the $0.85-$1.00/lb range, where they will be very competitive with many other solvents for a multitude of industrial and consumer uses. How will this innovation benefit the average consumer or the public in general?Economics: (1) At the lower prices made possible by the Argonne process,"greener" consumer products could be reformulated with lactate esters without penalizing the consumer through higher prices. (2) Individuals and companies who invest in the technology are likely to see an excellent return as the use of lactate esters expands, requiring the development of new production, formulation, and end use facilities. "Green" products: The availability of low-cost organic acid and ester substrates could open possibilities for many environmentally friendly new or reformulated products for industrial and consumer use. In this way, lactate esters could eventually find their way into the composition or production of a multitude of common household products, including packaging, biodegradable plastics, paints, paint strippers, grease removers, and cleansers, as well as most semiconductor chips in computers and consumer electronics. Thus, the environmental benefits would be pervasive, from lower toxic exposures directly in the consumer's household, to indirect but large-scale benefits from "greener" chemical production and industrial cleaning. Renewable feedstock: Using renewable carbohydrates to replace petrochemicals has the triple benefit of lessening depletion of natural resources, reducing U.S. dependence on foreign oil, and reducing both pollution and net production of carbon dioxide, a greenhouse gas. Reduced energy use: The process uses 90% less energy than current processes, for savings on the order of 50 trillion Btu/yr. Pollution prevention: Substitution for halogenated solvents. Lactate esters produced by the new process could be an environmentally sound and commercially viable alternative to about 80% of the 3.8 million tons of solvents used in the United States each year. Some of these solvents (such as chlorofluorocarbons and ethylene glycol ethers) have been implicated in ozone depletion, cancer and other health effects, and other environmental damage. Ethyl lactate has low volatility and is nontoxic and biodegradable. Table 1 shows some of the applications for which lactate esters can be substituted for halogenated solvents, as well as other uses of these esters. Elimination of salt waste: Under current processes, producing one ton of lactic acid produces one ton of gypsum (a salt, calcium sulfate) as waste. Gypsum is bulky and expensive to dispose of. The Argonne process enables the direct conversion of salts to their esters. It thus produces no salt waste. Reduced emissions: (1) In end use: lactate esters are nonvolatile, so any substitution for volatile solvents will reduce emissions. (2) In production: the Argonne process operates in a closed system with greatly reduced volumes of volatile alcohols, compared to current processes. (3) Overall: the use of renewable feedstocks lowers the net production of carbon dioxide, a greenhouse gas. When was this innovation developed?Laboratory work on the membrane separation and purification process began in 1993. Funding from DOE's Office of Industrial Technology (DOE/OIT) supported sustained work on the fundamental issues limiting bioprocessing. This has led to a U.S. patent which was issued in March 1998, and, with additional funding from the private sector, the process was successfully piloted. The technology has been licensed, and a joint venture is being formed with several industrial partners. A plant with a capacity of 10 million pounds per year is being planned for construction in 1999. This will be followed by a plant capable of producing 100 million pounds per year. The U.S. Army and other agencies have indicated strong interest in developing programs to formulate lactate esters as a solvent replacement for many of the halogenated solvents currently in use. What product or products incorporate this innovation?Lactate esters and other esters produced by using this process could eventually be used in the composition or production of a multitude of common household products, including packaging, biodegradable plastics, paints, paint strippers, grease removers, cleansers, aerosols, adhesives, and recycled paper products. Also, it could be the major solvent in semiconductor manufacturing and thus affect all chip-bearing devices from computers to consumer electronics. For More InformationFor more information, contact Argonne's Office of Technology Transfer (800-627-2596, partners@anl.gov). |
|
||||
|
||||
