Real-time in situ ATR-FTIR analysis of the liquid phase hydrogenation of γ-butyrolactone over Cu-ZnO catalysts:: A mechanistic study by varying lactone ring size

Real-time in situ attenuated total reflection (ATR) FTIR spectroscopy is a powerful tool for both kinetic and mechanistic studies of heterogeneous catalytic liquid phase reactions at high temperature and pressure. This is illustrated by the liquid phase hydrogenation of T-butyrolactone (five ring) to 1,4-butanediol over a copper zinc oxide catalyst at 453 K and a total hydrogen pressure of 5.0 MPa. The concentration profiles of the hydrogenation reaction obtained by this real-time analysis technique are in excellent agreement with conventional off-line GC analysis. Complementary results were found for the hydrogenation of delta-valerolactone (six ring) to 1,5-pentanediol. When investigating g-caprolactone (seven ring), a severe change in reaction selectivity was observed. This was explained by a significant change in reaction mechanism. However, by conduction several additional experiments a clear mechanistic picture could be created for the three lactone hydrogenation reactions. (C) 2004 Elsevier Ltd. All rights reserved.