Patent GB-608538-A (GB)
Title: Conversion products of 2:3-dihydropyran
IPC: C07D309/04
Filed: 1946-02-26
Abstract: An aluminium silicate dehydration catalyst is prepared by spraying a solution of sodium silicate into a solution of aluminium nitrate and completing the precipitation by addition of ammonia, whereafter the precipitate is ignited and pelleted with the aid of graphite.  Other specified dehydration catalysts are acid-extracted kaolin, artificial and natural zeolites such as acid-extracted bentonite and acid-extracted Terrana earth, phosphoric acid on kieselguhr, and alumina on silica gel.ALSO:Resinous products are obtained by heating 2 : 3-dihydropyran to 150-350 DEG  C. in the presence of a dehydration catalyst.  The process may be effected at atmospheric or raised pressure in the vapour or liquid phase and in the presence or absence of an inert gas.  The dihydropyran may be produced in situ by heating vapourised tetrahydrofurfuryl alcohol to about 350 DEG  C. in the presence of a dehydration catalyst, and in this modification the process may be effected with a mass of dehydration catalyst having a temperature gradient such that tetrahydrofurfuryl alcohol comes into contact with the catalyst at about 350 DEG  C. and the products pass to a zone containing catalyst at 150-350 DEG  C. Specified catalysts are aluminium silicate, acid-extracted kaolin, artificial and natural zeolites such as acid-extracted bentonite and acid-extracted Terrana earth, phosphoric acid on kieselguhr, and alumina on silica gel.  The products may be used as modifiers of synthetic resins and other polymers.  Examples of the process are given, and Specification 573,507 is referred to.  According to one of the Provisional Specifications the process may be effected at 100-400 DEG  C. and steam may be present.  The other Provisional Specification states that, when tetrahydrofurfuryl alcohol is the starting material, the process may be effected at 250-500 DEG  C.ALSO:Liquid products of unstated constitution are obtained by heating 2 : 3-dihydropyran to 150-350 DEG  C. in the presence of a dehydration catalyst.  The process may be effected at atmospheric or raised pressure in the vapour or liquid phase and in the presence or absence of an inert gas.  The dihydropyran may be produced in situ by heating vapourised tetrahydrofurfuryl alcohol to about 350 DEG  C. in the presence of a dehydration catalyst, and in this modification the process may be effected with a mass of dehydration catalyst having a temperature gradient such that tetrahydrofurfuryl alcohol comes into contact with the catalyst at about 350 DEG  C. and the products pass to a zone containing catalyst at 150 DEG -350 DEG  C.  Specified catalysts are aluminium silicate, acid-extracted kaolin, artificial and natural zeolites such as acid-extracted bentonite and acid-extracted Terrano earth, phosphoric acid on kieselguhr, and alumina on silica gel.  The products are useful as hydraulic liquids and as modifiers of synthetic resins and other polymers.  Examples of the process are given.  Specification 573,507 is referred to.  According to one of the Provisional Specifications the process may be effected at 100-400 DEG  C. and steam may be present.  The other Provisional Specification states that, when tetrahydrofurfuryl alcohol is the starting material, the process may be effected at 250-500 DEG  C.