PROCESS FOR PREPARING A CYCLIC DIESTER OR A CYCLIC DIAMIDE BY REACTING A HYDROXYCARBOXYLIC ACID OR AMIDE WITH AN ACIDIC BEA-TYPE (H-BETA POLYMORPH A) ZEOLITE

摘要

A process for preparing a cyclic diester or a cyclic diamide by reacting a hydroxycarboxylic acid or amide with an acidic BEA (H-beta polymorph A) type zeolite. The process is characterised in that the total amount of acid sites is in the range of from 0.25 to 1.0 mmol/g and the amount of medium acid sites is at least 40% of the total amount of acid sites. The total amount of acid sites and the amount of medium acid sites are determined by NH3-TPD (temperature-programmed desorption of ammonia). Preferably, the process refers to the preparation of lactide from lactic acid. The framework structure of the zeolitic material comprises Si, Al, O, and H.