PHASE-DIAGRAMS FOR OIL METHANOL/ETHER MIXTURES/

One-phase transmethylations of vegetable oils with methanol to form me thyl esters occur considerably faster than conventional two-phase reac tions. Addition of simple ethers is an efficient method for producing a single phase. Ternary phase diagrams have been determined at 23 degr ees C for oil/methanol/ether mixtures; these are useful when applying the one-phase method across a wide range of conditions. Soybean, canol a, palm, and coconut oils were used in combination with five ethers, n amely, tetrahydrofuran (THF), 1,4-dioxane (DO), diethyl ether (DE), di isopropyl ether (DI), and tert-butyl methyl ether (TBM). All five ethe rs can produce miscibility for all methanol/oil compositions. The ethe r/methanol volumetric ratios required for miscibility at a methanol/so ybean or canola oil volumetric ratio of 0.20 (5.4 molar ratio) at 23 d egrees C are: THF, 1.15; DO, 1.60; DE, 1.38 DI, 1.57; and TBM, 1.57. F or THF, this results in one-phase mixtures that contain 65 vol% oil. S oybean and canola oil form identical diagrams. Palm oil requires sligh tly less ether at the lower methanol concentrations, but coconut oil r equires considerably less across the whole concentration range. Acid-c atalyzed reactions, when performed at the boiling point of the most vo latile component, require less ether than predicted from the diagrams.