Plant Oils and Fatty Acids

2 Synthesis of Platform Chemicals 2.1 Plant Oils and Fatty Acids 

As already mentioned, the development of metathesis catalysts that can be easily accessed from simple precursors is necessary if a large-scale application is desired. With this in mind, Forman et al. developed a robust ruthenium-based phoban-indenylidene complex through a simple and relatively inexpensive procedure, if compared to the preparation of C3 [40]. This mthenium alkylidene was tested in the bulk SM of methyl oleate. As a result, they could reach up to 50% conversion with 0.005 mol% catalyst at 50°C. 

Another interesting castor oil-derived platform chemical is 10-undecenal, which is at the same time a challenging substrate for olefin metathesis. For the SM of 10-undecenal, Dixneuf et al. modified C3 and C5 by insertion of SnCl2 into one Ru-Cl bond [48]. Modification of C3 led to a binuclear complex, which showed a conversion of 70% at a catalyst loading of 0.33 mol%. On the other hand, both the modified and unmodified C5 gave conversions over 70% with catalyst loadings of 1.25 mol%, but also led to formation of a high amount of by-products. 

The metathesis of oleochemicals in the presence of ethylene, also called ethenolysis, provides an efficient way to a-oleftns and 0)-unsaturated esters, which are useful intermediates for the synthesis of polymers, fragrances, surfactants, lubricants, and others [51, 52], The ethenolysis of methyl oleate was demonstrated in 1994 by Grubbs et al. using C3 [32], They could reach productive turnovers of 130-140. In 2001, Warwel et al. carried out the ethenolysis of the methyl esters of oleic, erucic, 5-eicosenoic, and petroselinic acids also in the presence of C3 [53]. The reactions were performed at 50°C and 10 bar using 0.025 mol% of catalyst and gave conversions from 58% to 74%. 

The bulk ethenolysis of methyl oleate was performed by Forman et al. using a phoban-indenylidene catalyst [38]. As for the SM of methyl oleate, this readily available catalyst demonstrated to be a suitable alternative to C3, affording the desired products in 64% conversion with a catalyst load of 0.005 mol%, at 50°C and 10 bar of ethylene. Using the same conditions, C3 led to a conversion of 43%. 

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Fig. 4 Renewable platform chemicals used in olefin metathesis (a) plant oils and fatty acids, (b) terpenes and terpenoids, (c) phenylpropanoids, (d) natural rubber (cw-1,4-poly isoprene), (e) carbohydrates, (f) amino acids and peptides, and (g) furans...

Plant oils or their derived fatty acids are inexpensive renewable carbon sources. In addition, the theoretical yield coefficient of bioproducts (PHA) from plant oil and fatty acid is considerably higher than that from sugars. High cell density fed-batch cultures produced value-added products from soybean oil or oleic acid as the carbon source. PHAs with high yield were produced by fed-batch culture of R. eutropha or its recombinant strain from soybean oil. High cell concentrations obtained by fed-batch cultures from oleic acid improved lipase activity by C. cylindracea and 10-KSA by Flavobacterium, sp. DS5, compared with those of flask cultures. There are still many industrially important value-added products that can be produced from inexpensive substrates such as soybean oil. 

ADMET has been used to take advantage of several natural polymer feedstocks, mainly plant oils and fatty acids (Figure 13.26) [190]. An initial study optimized the ADMET polymerization of a variety of plant oils, and yields of40—60% were obtained [191]. A set of polyamides were synthesized by ADMET polymerization of monomers ultimately derived from ricinoleic acid, the main fatty acid of castor oil [192]. Similarly, ADMET was utilized to polymerize 1,3-di-lO-undecenoxy-2-propanol, a castor oil-based diene, which was subsequently reacted with... 

In the formation of sustainable thermoset resins, epoxidized and acrylated epoxy-dized plant oils and fatty acids have been largely utihzed, as reported from hterature [51]. For composite applications, acrylated epoxydized soy bean oil (AESO) resin is mainly used because it is commercially accessible [52]. The synthesis of AESO is shown Figure 6.10 the carbon-carbon double bonds in the fatty acid chains are modified to append different polymerizable functionalities, such as epoxides and acrylates, to increase the reactivity of the vegetable oils [53], AESO can be cured at room and high temperatures, depending on the initiator, and can be blended with a reactive diluent such as styrene in order to improve the processing flowability and the mechanical performance. Structural applications such as sandwich beams... 

Large supply of naturally derived lipids can be obtained from plants in which many oils and fatty acids can be readily extracted and purified. Animal sources (e.g., eggs or milkfats) are used to derive complex lipids such as phospholipids and cholesterol. Yield from natural sources is dependent on the weight-percent composition and the efficiency of the extraction procedure. The constitution of fatty acids in vegetable oils varies widely from different sources. For example, oleic acid is present at 64.6% by weight in olive oil but is present at only 0.7% in palm kernel oil. Similarly, castor oil triglyceride is comprised of almost entirely ricinoleic chains. There are numerous raw material suppliers of oils and oil fractions worldwide. As such, the relative cost of bulk purified... 

Although most hpids required for cell structure, fuel storage, or hormone synthesis can be synthesized from carbohydrates or proteins, we need a minimal level of certain dietary hpids for optimal health. These hpids, known as essential fatty acids, are required in our diet because we cannot synthesize fatty acids with these particular arrangements of double bonds. The essential fatty acids a-linoleic and a-linolenic acid are supphed by dietary plant oils, and eicosapentaenoic acid (ERA) and docosa-hexaenoic acid (DHA) are supplied in fish oils. They are the precursors of the eicosanoids (a set of hormone-like molecules that are secreted by cells in small quantities and have numerous important effects on neighboring cells). The eicosanoids include the prostaglandins, thromboxanes, leukotrienes, and other related compounds. 

Figure 22.2 [A] General triglyceride structure and fatty acid percentage composition of common plant oil. [B] Fatty acids commonly used in polymer chemistry [a] oleic acid, [b] linoleic acid, (c) linolenic acid, [d] erucic acid, [e] petroselinic acid, [f] ricinoleic acid, [g] vernolic acid, [h] 10-undecenoic acid (reprinted with permission of Montero de Espinosa et al., 2011, Elsevier [10]].

The modern batch deodorizer has a capacity from 5 to 30 tonnes. It is still frequently constructed of mild steel, though stainless steel is preferred. It is heated by high-pressure steam or, in some cases, by Dowtherm or thermal oil, and its vaporization efficiency has been improved by the inclusion of mammoth pumps and effective head space insulation to prevent refluxing. A vapour scrubber can be installed to recover oil and fatty acids from the distillate vapour. The complete batch cycle time is between 6 and 10 h depending on the feedstock. The unit is not, however, suitable for physical refining and it is expensive to operate compared with continuous and semi-continuous plant. 

Of course, classes/groups of metabolites which occur (almost) ubiquitously or at least frequently in the plant kingdom ( general secondary metabolites ) are also constituents of both large Solanales families (i) phenolics such as simple cinnamic acid derivatives (Sect. 6.4), hydroxycoumarins (Sect. 6.6), hydroxycinnamate conjugates (Sect. 6.7), flavonoids (Sect. 6.8), lignans (Sect. 6.9), (ii) sterols (Sect. 7.6), (iii) carotenoids (Sect. 7.12), (iv) fats/oils and fatty acids (Sect. 8.1), (v) carbohydrates (Sect. 8.2) etc. 

Starch and fatty acids are the main food constituents of biomass. Sugar is derived from starch by hydrolysis or directly by extraction from sugar cane or beet. Fermentation converts sugars into alcohol that can be directly used as fuel, or in principle can be used as the raw material of a bioreftnery plant for further upgrading. Triglycerides, derived from oil seeds, are used to be converted into biodiesel through transesterification processes (Fig. 1.14). 

Primary metabolites are produced in larger quantities than the secondary metabolites and have specific metabolic functions. Primary metabolites obtained from higher plants are used as foods, food additives, and industrial raw materials, such as carbohydrates, vegetable oils, protein, and fatty acids. They are generally high-volume, low-value bulk materials. 

When considering biomass as a source of chemical feedstock, it is also important to remember that it is not a homogeneous organic structure. The carbohydrate structures of terrestrial plants are composed of both five-carbon and six-carbon sugar polymers. The lignin component, which binds the polymers together, is an aromatic polymer of nominally propyl-methoxyphenols. In addition, there are proteins and fatty acids/oils, as well as the trace biocomponents that incorporate much of the mineral content. Therefore, processing biomass to chemical products must take into consideration both its bulk chemical structure and its components. 

Fats and oils are triesters of the trivalent alcohol glycerol and three (different) even-numbered aliphatic carboxylic acids, the fatty acids. Fats and oils differ in the length and the number of unsaturated bonds in the carbon chain. The shorter Cio-Ci4-fatty acids are obtained from coconut oil and palm kernel oil. These fatty acids are mostly saturated, and they are used in the manufacture of detergents. Cig-fatty acids are more widely used. Oleic acid, a Cig-fatty acid with an unsaturated bond on the ninth carbon atom, can be produced from many crops. Specific varieties or genetically modified plants, such as rape, have a content of over 90% oleic acid [4]. 

The tropical oil crops, coconut and palm, are the most efficient oil-producing crops, with coconut plantations yielding up to 2 tonnes per hectare of oil and the best performing palm plantations from 5-6 tonnes per hectare. By comparison, oil yields of temperate oil crops are typically of the order of 1-2 tonnes per hectare for the best oil-yielding crops (oilseed rape and sunflower). Clearly, Table 2.1 represents only a small fraction of oil-bearing plant species. Many other seed, fruit and nut oils are extracted for food use, however unless they contain fatty acid profiles or fatty acid derivatives of specific industrial interest, total oil-yield, fatty acid yield and cost of the final oil product tends to limit their use in industrial applications on all but a small or localised scale. 

The alkylhydroperoxides are also interesting because of their formation in natural products. Unsaturated fatty acids and their esters (plant oils) are oxidized in air to peroxides (auto-oxidation). This leads to a stepwise breaking of the double bonds leading to the formation of aldehydes, ketones and fatty acids, all of which make their presence known through their strong odor intensities (e.g. rancid oil). 

CLA refers to a mixture of positional and geometric isomers of linoleic acid (cis-9, cis-12 octadecadienoic acid) with a conjugated double bond system. The structure of two CLA isomers is contrasted with linoleic and vaccenic acids in Figure 3.1. The presence of CLA isomers in ruminant fat is related to the biohydrogenation of polyunsaturated fatty acids (PUFAs) in the rumen. Ruminant fats are relatively more saturated than most plant oils and this is also a consequence of biohydrogenation of dietary PUFAs by rumen bacteria. Increases in saturated fatty acids are considered undesirable, but consumption of CLA has been shown to be associated with many health benefits, and food products derived from ruminants are the major dietary source of CLA for humans. The interest in health benefits of CLA has its genesis in the research by Pariza and associates who first demonstrated that... 

Robertson, J. A., Morrison, W. H., Ill, and Wilson R. L., Effects of Planting Location and Temperature on the Oil Content and Fatty Acid Composition of Sunflower Seeds, USDA Agric. Results ARR-S-3, U.S. Dept. Agriculture, Washington, DC, 1979. 

When considering the addition of a bioactive to food, it is useful to classify them as oil-soluble (e.g., polyunsaturated fatty acids, carotenes, lycopene), water-soluble (e.g., anthocyanins, proteins and peptides), or water/oil dispersible components (e.g., probiotics). Bioactives may be added directly to food if they are in a compatible format with the food matrix and provided their direct addition does not impact negatively on food quality or the bioavailability of the bioactive. When the solubility in a food matrix is limiting, its hydrophilicity/lipophilicity may be modified to enable improved incorporation. An example is the conversion of free plant sterols to fatty acid esters in order to make them more oil-soluble and readily incorporated into spreads (Deckere de and Verschuren 2000). 

Most commodity oils contain fatty acids with chain lengths between Cie and C22, with Cig fatty acids dominating in most plant oils. Palm kernel and coconut, sources of medium-chain fatty acids, are referred to as lauric oils. Animal fats have a wider range of chain length, and high erucic varieties of rape are rich in this C22 monoene acid. Potential new oil crops with unusual unsaturation or additional functionahty are under development. Compilations of the fatty acid composition of oils and fats (6, 9, 11, 12) and less-common fatty acids (13) are available. 

In 1957, scientists in Australia and California independently reported a mutation that came to be known as oleic safflower (54-56). This mutation occurred naturally and produces a plant and seed that look exactly like linoleic safflower, except for an oil whose fatty acid distribution is a mirror image of linoleic safflower oil (Table 2). The initial oleic safflower variety released by Knowles, UC-1 (57), was lower in oil content and had a poorer yield than conventional varieties available at the time. This meant that oleic safflower oil was initially sold at a premium. But agronomic research has since produced varieties that equal or even exceed normal safflower in yield and that are comparable in oil content. 

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