ABSTRACT
In 2011/2012, the total production of the nine most important plant oils (palm, soybean, rapeseed, sunflower, palm kernel, cottonseed, peanut, coconut, and olive) amounted to around 156.8 million tons (USDA, 2013-05). The world consumption of vegetable and animal oils and fats was numbered to be in the range of 171.4 million tons in 2010. Around 74% have been used for edibles, 12% for energy production, 10% for production of chemicals and 4% for further use, e.g., animal feed (ISTA-Mielke, 2012; Meo-Carbon-Solutions, 2013).Vegetable oils are frequently utilized renewable raw materials. These oils are often modified for their further usage. One example for such a modification is the epoxidation of oils, which is done for many different applications and will be explained in detail in this chapter. The epoxidation is already established as chemical process on industrial scale, but different problems such as the requirement of a strong acidic catalyst and by-product formation due to ring-opening reactions under acidic conditions are existent (Dinda et al., 2008; Rangarajan et al., 1995; Rüsch gen. Klaas and Warwel, 1999; Swern, 1949). Within the field of epoxidation, the chapter focuses on the chemo-enzymatic oxirane formation using lipases as biocatalysts. Lipases are able to perform the similar epoxidation reaction under mild conditions preventing a strongly acidic medium. This lipase-catalyzed epoxidation is the main topic of this book chapter, but at the beginning a short overview on the characteristic properties and reactions starting from epoxide intermediates will be introduced, followed by a summary of different methods described for their chemical synthesis. A small section gives a survey of general features and applications of triacylglycerol lipases (EC 3.1.1.3). Afterward, the key issue of the chapter, the lipase-catalyzed epoxidation, summarizes achievements within the conversion of plant-oil derivatives and alkenes. Finally, the chapter concludes by giving examples for application of epoxidized fatty compounds. 20.2.1 Epoxides: Oxirane Oxygen Compounds as
Functional IntermediatesThe epoxy or also called oxirane group is a highly reactive structure and epoxides are therefore a common intermediate molecule
in the chemical industry. The most important low-molecular-weight epoxy compounds are ethylene oxide, propylene oxide, and epichlorohydrin. Previously, ethylene oxide has been produced via the so-called chlorohydrin process, which is now almost completely replaced by direct oxidation of ethylene using oxygen or air as oxygen donor and a silver-based catalyst. The most significant applications of ethylene oxide are the use as disinfectant, sterilizing agent, fumigant, or its further conversion to ethylene glycol, which is used in antifreeze and for the synthesis of polyester fibers. Other ethylene oxide derivatives, such as amines and poly(ethylene glycols), are used in surfactants or solvents (Sienel et al., 2000). The world demand for ethylene oxide in 2006 was estimated to be in the range of around 18 million tons, showing the industrial importance of this functional intermediate (Lee et al., 2010).Propylene oxide is produced in lower amounts compared to ethylene oxide, but also is a fundamental organic intermediate with a yearly production of around 6 million tons in 2006 (Tsuji et al., 2006). Propylene oxide is used to obtain a variety of products, including polymers (such as polyurethanes, polyesters), oxygenated solvents (propylene glycol ethers), and industrial fluids (monopropylene glycol and polyglycols) (Kahlich et al., 2000).
