To produce propylene glycol from glycerine, using hydrogenation and refining.
Glycerine is fed to a low-pressure, vapor-phase hydrogenation section (1) where the glycerine is vaporized into a circulating hydrogen stream followed by conversion to propylene glycol over a fixed catalyst bed. Crude propylene glycol product is condensed, and the gas is recirculated with a low-head centrifugal compressor.
Crude propylene glycol from hydrogenation section (1) is polished and it passes to the refining section (2). The refining section (2) recovers mixed mono alcohols (methanol, ethanol and propanol) and mixed glycols (mainly ethylene glycol) byproducts, and produces a final-product propylene glycol. Residual glycerine is also recovered and recycled to the hydrogenation section (2).
Economics: Feedstock and utility consumption are heavily dependent on feedstock composition; thus, each must be evaluated on a case-bycase basis.
Licensor: Davy Process Technology, UK