REACTION AND KINETIC-STUDIES OFF LACTIC-ACID CONVERSION OVER ALKALI-METAL SALTS

Studies of lactic acid catalytic conversion over alkali salts and base s on silica demonstrate that the yield of 2,3-pentanedione (23P) incre ases with decreasing Lewis acidity of the alkali metal, from 15% for l ithium hydroxide at 320 degrees C to 49% for cesium hydroxide at 280 d egrees C. The rate of 23P formation varies linearly with alkali metal loading up to saturation at 2 mmol of catalyst/g of support. Experimen ts with different silica supports showed that acetaldehyde formation i ncreases with support acidity, reducing 23P yield. Postreaction FTIR s tudies indicate the presence of alkali lactate as the dominant species on the support surface at reaction conditions. These results, along w ith the kinetic model developed, support the proposed mechanism of 23P formation as a condensation between lactic acid and alkali lactate.