REACTION AND SPECTROSCOPIC STUDIES OF SODIUM-SALT CATALYSTS FOR LACTIC-ACID CONVERSION

Catalytic conversion of lactic acid to 2,3-pentanedione over sodium sa lts and base on low surface area-silica support has been studied. Yiel d and selectivity toward 2,3-pentanedione are optimal at around 300 de grees C, 3-4 s residence time, and 0.5 MPa total pressure. Anions of i nitial salt catalysts used do not participate-in lactic acid condensat ion to 2,3-pentanedione once steady-state conditions have been achieve d; instead, sodium lactate has been identified by postreaction FTIR sp ectroscopy as the primary,stable species on the support during reactio n. Sodium lactate is believed to be an intermediate in 2,3-pentanedion e formation. Conversion of a sodium salt to sodium lactate is greatest when the salt used has a low melting point and a volatile conjugate a cid; the extent of conversion depends weakly on reaction time and temp erature within experimental conditions. At high temperature (similar t o 350 degrees C), sodium lactate decomposes to sodium propanoate and s odium acetate, which may-explain reduced 2,3-pentanedione yields at hi gher temperatures.