Lactic acid purification technologies

Table 2.6 Lactic Acid Purification Technology (Henton et al., 2005, Published with Permission)—cont d...

Martak, J. and Schlosser,. (2007) Extraction of lactic acid by phosphonium ionic liquids. Separation and Purification Technology, 57, 483. 

Many industrial organic acids can be produced by fermentation, such as acetic, citric, and lactic acids. Succinic acid is a dicarboxylic acid of potential industrial interest as a platform chemical (1-3). Separation and purification of succinic acid by adsorption was tested to replace current precipitation methods and their associated waste disposal problems. Succinic acid is a valuable intermediate value chemical with a moderate market. For succinic acid to have an economic and energy impact, it will need to become a commodity chemical intermediate with a much lower price. This target price hasbeen estimated to be between 0.22 and 0.30 / lb ( 0.48- 0.66/kg) and is potentially achievable with advanced technology (1). At this price, succinic acid can be catalytically upgraded into other higher valued chemicals suchastetrahydrofuran, 1,4-butanediol, y-butyrolactone, 2-pyrrolidinone, and N-methylpyrrolidinone. 

This salt is isolated by filtration in the final step, washed with water and acidified with sulfuric acid to liberate free lactic acid with formation of calcium sulfate as solids. When ammonia is used for the neutralization, the ammonium lactate is formed and directly converted into butyl lactate by esterification with n-butanol, as shown in Scheme 1.2. Here, the ammonia is recovered and recycled. The following distillation and hydrolysis of butyl lactate gives an aqueous lactic acid with high efficiency. The lactic acid obtained by this method has higher purity than that obtained by the calcium salt method. The technologies for the above lactic acid fermentation and purification have well been established, and the production of both D- and L-lactic acids is conducted industrially in a plant scale of 100000 ton year. ... 

The attractive price and commercial availability of lactic acid were important reasons why PLA became the first mass-produced bio-based polyester. The critical success factor for a final breakthrough of all green chemicals and plastics based on annually renewable materials is economic sustainability. Thus, the very basis of cost-competitive PLA is an industrial fermentative production process for lactic acid with efficient use of carbohydrates followed by excellent purification technology with minimum generation of by-products. 

Datta R, Glassner DA, Jain MK, Vick Roy JR (1992) Fermentation and purification process for succinic acid. US Patent 5,168,055 Datta R, Tsai S-P, Bonsignore P, Moon S-H, Frank JR (1995) Technological and economic potential of poly (lactic acid) and lactic add derivatives. FEMS... 

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