Limonene from citrus

Isolate The term for a single constituent that has been separated from a mixture of volatiles such as an essential oil, e.g. citral from lemongrass, limonene from citrus oils. 

Most of the hydrocarbons emitted by plants are terpenes, which are produced by conifers (evergreen trees and shrubs such as pine and cypress), plants of the genus Myrtus, and trees and shrubs of the genus Citrus. Three of the most common terpenes emitted by trees are a-pinene from pine trees, limonene from citrus trees and fruit, and isoprene (2-methyl-l,3-butadiene), a hemiterpene, from the Hevea brasilinesis tree, the main source of isoprene from which natural rubber is synthesized (see Figure 7.7). In many areas, terpenes from plants, which are highly reactive with atmospheric oxidants including ozone and hydroxyl ladicaL constitute the main source of hydrocarbons... 

Cide-Kick Spray Adjuvant [Brewer Int l.j Chem. Descrip. D-Limonene (from citrus peel) and nonylphenol polyethylene glycol ether... 

The other class of acrylic compatible tackifiers includes those based on ter-penes. Terpenes are monomers obtained by wood extraction or directly from pine tree sap. To make the polyterpene tackifiers, the monomers have to be polymerized under cationic conditions, typically with Lewis acid catalysis. To adjust properties such as solubility parameter and softening point, other materials such as styrene, phenol, limonene (derived from citrus peels), and others may be copolymerized with the terpenes. 

The three main platform molecules employed in terpene chemistry are a-pinene and / -pinene, which are extracted from turpentine oil (350000 t a-1) a co-product of paper pulp industry, and limonene extracted from citrus oil (30000 t a-1). 

TERPENELESS OIL. An essential oil from which the teqoene components have been removed by extraction and fractionation, either alone or in combination. The optical activity of the oil is thus reduced. The terpene-less grades are much more highly concentrated than the original oil (15—30 times). Removal of terpenes is necessary to inhibit spoilage, particularly of oils derived from citrus sources. O11 atmospheric oxidation the specific terpenes form compounds that impair the value of the oil for example, d-limonene oxidazes to carvone and y-terpinene to p-cymene. Terpeneless grades of citrus oils are commercially available. 

The effects of biochemical use are at various folds, but the major direct substation of biochemicals for petrochemicals is found at the upstream of chemical production processes. For instance, the oil distraction from crops is far less harmful than the oil extraction from petroleum. In the case of phenol, making phenol from plants is estimated to generate 80 percent less pollutants than making phenol from petroleum. Another example is limonene. Limonene derived from citrus fruit... 

Another major feedstock, limonene, is derived from citrus oils, e.g. as a byproduct of orange juice production, to the extent of around 300001 a-1 [213]. 

Biosolvents or green solvents —as they are sometimes called—are derived from agrochemicals (see Figure 12.24). Some of the better known biosolvents are limonene (derived from citrus fruits), methyl soyate (produced from soy), and ethyl lactate (produced mainly from com). 

Polyterpene resins are related to the oldest reported polymerization, as they were first observed in 1789 by Bishop Watson by treatment of turpentine with sulfuric acid [92]. Commercial polyterpene resins are synthesized by cationic polymerization of /3- and a-pinenes extracted from turpentine, of rf,/-limonene (dipentene) derived from kraft-paper manufacture, and of d-limonene extracted from citrus peels as a by-product of juice industry [1,80,82,93]. The batch or continuous processes are similar for the three monomers. The solution polymerization is generally performed in mixed xylenes or high boiling aromatic solvent, at 30-55° C, with AlCl3-adventi-tious water initiation. The purified feedstream (72-95% purity, depending on monomer) is mixed in the reactor with solvent and powdered A1C13 (2—4 wt% with respect to monomer), and then stirred for 30-60 min. After completion of the reaction, the catalyst is deactivated by hydrolysis, and evolved HC1 is eliminated by alkaline aqueous washes. The organic solution is then dried, and the solvent is separated from the resin by distillation. 

D-Limonene is regulated as an air pollutant in Florida when released from citrus processing plants, because it can combine with NO to form ozone, contributing to smog, on hot days. The legislation establishes that 65% of the citrus oil (o-limonene) be captured for all plants. Most plants now capture between 40% and 45% of the oil. 

On a commercial basis, lemon Petitgrain oil is produced from citrus leaves in Italy. In contrast to other Petitgrain oils, its composition resembles more to the peel oil of the corresponding fruits. The main constituents are limonene (app. 30%), P-pinene (10-20%) and citral (15-28%) [104, 109-114]. 

Limonene is widespread in essential oils. The main source for (-i-)-limonene are citrus peel oils. From this source it is obtained in large quantities as a by-product of the orange juice production. Therefore nature-identical products (e.g. from pinene) are not of great importance. The 5 C-values of natural limonene from orange peel oil has been found to range from -26.1 to -28.5%o, and the reported 5 H-values are from -215 to -264%o, in agreement with results for other natural isoprenoids. 

D-Limonene Another class of low-temperature HTF is based on naturally derived terpenes such as D-limonene. U.S. Patent 3,597,355 describes o-limo-nene as being particularly preferred among all the monocycloterpenes because of its characteristic properties such as low viscosity at low temperatures. D-Limonene is the major component in the oil of citrus fruit and is present in trace quantities in orange juice. It is recovered in commercial quantities by distilling orange oil obtained from citrus peels. Being derived from the citrus industry, o-limonene is considered a safe and environmentally friendly HTF, and hence it is preferred in many food and pharmaceutical processes. However, the melting point of D-limonene is about —78°C. Below this temperature, it becomes a thick white gel like substance that is impossible to pump. Therefore, the use of o-limonene is limited to... 

The epoxidation of terpenic substrates is of interest in the flavor and fragrance industry [55,56]. Terpenes are derivatives of isoprene, which has formula CsHg (2-methyl-frans-butadiene). There are tens of examples of terpenes, including limonene, a-pinene, geraniol, citronellol, myrcene, ocimene, camphene, a-terpin-eol, menthol, and isopugelol. Limonene is an abundant monoterpene extracted from citrus oil, which can be epoxidized to obtain fragrances, perfumes, and... 

The substrate specificity of 1,8-cineole, a-terpineol, limonene, and terpin-olene synthetases from sage has not yet been determined however, it is quite clear that the sage preparations, and similar preparations from Citrus (George-Nascimento and Cori, 1971 Chayet et al., 1977), can utilize both GPP and NPP for the biosynthesis of monocyclic monoterpenes. Only when such cell-free preparations are free of all competing enzyme activities can the true specificities of the monoterpene synthetases be accurately determined. 

Ethyl acetate is a solvent found in nature and is environmentally safe and acceptable for food applications. For instance, it is used in the packaging industry because it provides high printing resolution on plastics and metals. D-Limonene is a major compound found in oil extracted from citrus and is present in orange and fruit juices. It is also used in cleaning products as a solvent or a water dilutable product. It is a very versatile chemical and therefore used in a wide variety of applications. Scalping of D-limonene from... 

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