Process for the preparation of five- or six-membered cyclic ethers and anhydrohexite mixtures

摘要

Process for producing 5- or 6-membered cyclic ethers (anhydropolyols) comprises subjecting polyols having at least 4 C atoms and at least 2 OH groups to cyclodehydration at at least 100 degrees C in the presence of water, an acid catalyst, an acid-stable hydrogenation catalyst and hydrogen. Preferably the reaction temperature is 100-380 degrees C, preferably 180-280 degrees C. The H2 pressure is 1-20 MPa, preferably 3-10 MPa. The hydrogenation catalyst comprises Ru, Rh, Pd and/or Pt as metals or metal compounds. The hydrogenation catalyst is used in an amount of 0.001-10 (preferably 0.01-1) wt.% based on the polyol. The acid catalyst is a 1-10C aliphatic carboxylic acid, preferably formic, acetic or propionic acid. The acid catalyst is used in an amount of 0.1-20 (especially 0.5-10) wt.% based on the polyol. The polyol is a tetritol, pentitol or hexitol.