LACTIC-ACID CONVERSION TO 2,3-PENTANEDIONE AND ACRYLIC-ACID OVER SILICA-SUPPORTED SODIUM-NITRATE - REACTION OPTIMIZATION AND IDENTIFICATIONOF SODIUM LACTATE AS THE ACTIVE CATALYST

Lactic acid is converted to 2,3-pentanedione, acrylic acid, and other products in vapor-phase reactions over silica-supported sodium lactate formed from sodium nitrate. Multiparameter optimization of reaction c onditions using a Box-Benkhen experimental design shows that the highe st yield and selectivity to 2,3-pentanedione are achieved at low tempe rature, elevated pressure, and long contact time, while yield and sele ctivity to acrylic acid are most favorable at high temperature, low pr essure, and short contact time. Post-reaction Fourier transform infrar ed spectroscopic analyses of the catalyst indicate that sodium nitrate as the initial catalyst material is transformed to sodium lactate at the onset of reaction via proton transfer from lactic acid to nitrate. The resultant nitric acid vaporizes as it is formed, leaving sodium l actate as the sole sodium-bearing species on the catalyst during react ion. (C) 1997 Academic Press