Drying Oils and Resins. Segregation of Fatty Acids and their Derivatives by Extractive Crystallization with Urea.

Urea complexation for the rapid, ecologically responsible fractionation of fatty acids from seed oil

“…FFA of shorter chainlengths or containing constituents such as double bonds, as well as epoxy or hydroxy functional groups, are less likely to form complexes. As expected, the abundance of good "guest" molecules in a mixture may enhance the complexation of poorer "guests" (4)(5)(6)(7)(8)(9)(10).…”

“…A low urea to FFA ratio (≤7:1 mol/mol) prevents indiscriminate FFA complexation. Most previous FFA fractionation studies (5)(6)(7)(8)(9)(10)15) allowed solutions to slowly cool over a long period of time, e.g., 24 h (15), in order to maximize complex formation. This is not suitable for applications involving use of a complex formation-based unit operation in an ongoing industrial process, or in regional settings where efficient refrigeration is not pos-sible.…”

“…Research from the 1940s to 1960s demonstrated that urea complexation protects guest molecules from oxidation (5) and can be used to fractionate FFA and derivatives such as esters from various seed, fish, and other oils (5)(6)(7)(8)(9)(10). Much of this early research was reviewed by Swern (4).…”

Urea‐based fractionation of seed oil samples containing fatty acids and acylglycerols of polyunsaturated and hydroxy fatty acids

“…Polyunsaturated FFA (PUFA) and branched FFA have been isolated through removal of saturated and monounsaturated FFA by UC formation. Examples include the isolation of 20:5 5c,8c,11c,14c,17c (eicosapentaenoic acid, or EPA) and 22:6 4c,7c,10c,13c,16c,19c (docosahexaenoic acid, or DHA) from fish oil FFA (2-5), 18:3 6c,9c,12c (γ-linolenic acid, or GLA) from black currant and borage oil FFA (6,7), and 18:3 9c,12c,15c (α-linolenic acid) from linseed oil (8,9). In addition, UC formation effectively discriminated against cyclic FFA, such as malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) FFA derived from Bombax munguba (cotton) and Sterculia foetida (kapok) seed oils, respectively (10).…”

Improving the Cold Flow Properties of Biodiesel by Fractionation

“…In contrast, molecules with less than six carbon atoms or with branched or cyclic moieties in their structure formed less stable clathrates when mixed with urea (Bengen & Schlenk, 1949;Hayes, 2002;Schlenk, 1954). Furthermore, increasing the degree of unsaturation, particularly with respect to cis-type double bonds, in fatty acids and esters also decreases the tendency to form stable UIC (Abu-Nasr et al 1954;Domart et al, 1955;Newey et al 1950;Schlenk & Holman, 1950;Swern & Parker, 1952a, 1952b, 1953. These early findings suggested that processes for separating mixtures of organic compounds with high degrees of selectivity could be based on their tendencies to form clathrates when mixed with urea.…”