Chemical Properties
1,3-Propanediol, an isomer of propylene glycol, is a viscous, colorless, odorless, hygroscopic liquid that has a brackish irritating taste. miscible with various solvents such as water, ethanol, acetone, chloroform (chloroform) and ether, and is insoluble in benzene. Combustible.
Uses
1,3-Propanediol is used as a solvent for thin film preparations, in the production of polymers such as polytrimethylene terephthalate, adhesives, laminates, coatings, moldings, aliphatic polyesters, as an antifreeze and in wood paint. It also acts as a reagent for vinyl epoxide synthon, for epoxide ring-opening, for polymerization reactions and for natural product syntheses.
Definition
ChEBI: Propane-1,3-diol is the simplest member of the class of propane-1,3-diols, consisting of propane in which one hydrogen from each methyl group is substituted by a hydroxy group. A colourless, viscous, water-miscible liquid with a high (210℃) boiling point, it is used in the synthesis of certain polymers and as a solvent and antifreeze. It has a role as a protic solvent and a metabolite.
Application
1,3-Propanediol /PDO/ is mainly used for making polytrimethylene terephthalate polymer, which is used in fibers and fabrics, for example, carpets, textiles, engineering thermoplastics, nonwovens, films, and monofilaments. PDO finds also use as chain extender in thermoplastic polyurethanes, where it contributes to improved thermal, hydrolytic and dimensional stability. In adipate polyesters with other diols these diols are partly substituted by 1,3-propanediol to break crystallinity in order to obtain liquid polyester polyols. In polyesters for powder coatings PDO improves the flexibility but lowers the glass transition temperature somewhat. PDO finds also uses in cosmetics and personal care products, engine coolants, and solvents for ink-jet and screen inks.
Biosynthesis
1,3-Propanediol (1,3-PDO) can be produced by fermentation from glycerol, with different strains such as Klebsiella pneumoniae, Clostridium butyricum, Clostridium pasteurianum, and Citrobacter freundii. Drawbacks of industrial fermentation using these strains are strong inhibition of 1,3-PDO production and by-products during fermentation.
Flammability and Explosibility
Non flammable
Synthesis
1,3-Propanediol is produced commercially by Degussa starting from acrolein.
CH2CHCHO + H2O → HOHCH2CH2CHO
HOHCH2CH2CHO + H2 → HOHCH2CH2CH2OH
The addition of water under mild acidic conditions gives 3-hydroxypropionaldehyde with high selectivity. Preferentially buffer solutions with a pH 4-5 or weak acidic ion exchange resins are used as catalysts. Further hydrogenation of this aqueous solutions gives 1,3-propanediol. There is an alternative route via hydroformylation of ethylene oxide and subsequent hydrogenation of the intermediate 3-hydroxypropionaldehyde.
Purification Methods
Dry this diol with K2CO3 and distil it under reduced pressure. More extensive purification involves conversion with benzaldehyde to 2-phenyl-1,3-dioxane (m 47-48o) which is subsequently decomposed by shaking with 0.5M HCl (3mL/g) for 15minutes and standing overnight at room temperature. After neutralisation with K2CO3, the benzaldehyde is removed by steam distillation and the diol is recovered from the remaining aqueous solution by continuous extraction with CHCl3 for 1day. The extract is dried with K2CO3, the CHCl3 is evaporated and the diol is distilled. [Foster et al. Tetrahedron 6 177 1961, Beilstein 1 IV 2493.]
