Synthesis of lactide from L-Lactic acid over iso-reticular zeolites derived from Al-UTL

Controlling the reaction selectivity by use of rationally designed catalysts provides high yields of desired products rendering the process more efficient and sustainable. In this study, we investigated a series of isoreticular zeolites (Al-IPC-n, n = 2, 4, 6, and 7), in the synthesis of lactide from L-Lactic acid as an intermediate for the polylactic acid production. Catalytic tests allowed a thorough understanding of the structure-acidity-activity relationship and the control of the shape selectivity. The lactide and the dimers of the lactic acid were obtained in one step with a high selectivity (>55% for lactide and >70% for the dimer of the lactic). The selectivity to L,L-lactide was comparable with that on more acidic commercial BEA. A balance between the acidity and the pore size afforded high yields of the dimer, avoiding the poisoning of the catalyst and the production of the larger oligomers.