Patent GB-634089-A (GB)
Title: Improvements in and relating to the hydrogenation of cyclic organic compounds
IPC: C07D307/00
Filed: 1946-07-08
Abstract: A copper-containing catalyst used in a hydrogenation process for the production of oxygen containing heterocyclic compounds (see Group IV (b)) may be copper on zinc oxide, copper on gamma alumina, copper chromite which may also contain magnesium, copper-barium chromite, copper on magnesia and copper on kieselguhr.  Copper on zinc oxide may be prepared by adding an aqueous solution of sodium carbonate to a solution of copper and zinc salts, e.g. nitrates or sulphates and calcining the precipitate.  The product is ground and pelleted and reduced in hydrogen diluted with nitrogen at 300 DEG  C. before use. Copper on gamma alumina may be made by igniting alumina mono- or tri-hydrate to form gamma alumina and then impregnating the latter with copper nitrate solution and igniting to form the oxide.  The mass is then reduced with diluted hydrogen at 300 DEG  C. before use. This catalyst may also be obtained by treating activated alumina with copper nitrate and igniting and reducing or by adding sodium carbonate to a mixed solution of copper and aluminium salts, heating the precipitate and reducing with diluted hydrogen at 300 DEG  C. Other copper-containing catalysts are foraminate copper catalysts. Specified catalysts of this type are foraminate copper-aluminium, copper-silicon and copper-zinc.  Such catalysts are described in Specifications 621,749, 624,035 and 634,097. Other copper catalysts mentioned are those prepared by the substantially complete extraction of the alloying metal from particles of alloys comprising copper and an alloying metal or metals more soluble in acid or alkali or other extracting liquid than copper.  Suitable alloys are those with aluminium, silicon zinc and magnesium.  In an example, a foraminate copper - aluminium catalyst is prepared by melting electrolytic copper and pure aluminium in a graphite crucible and then chill-casting and crushing the melt to 1/8 to 1/4 inch mesh granules. These granules are then treated with preheated aqueous sodium hydroxide which is passed upwards through the material at 100 DEG  C. until 20 per cent of the aluminium is removed.ALSO:Saturated heterocyclic organic compounds containing carbon, hydrogen and oxygen only, the oxygen being in the nucleus, are produced by hydrogenating a heterocyclic mono- or poly-ene containing carbon, hydrogen and oxygen only, the oxygen being in the nucleus, and containing no groups external to the nucleus unless saturated hydrocarbon groups, in the liquid phase at elevated temperature and elevated pressure, in the presence of a copper-containing catalyst, particularly a catalyst containing metallic copper.  Preferred reaction conditions are 10-400 atmospheres pressure and temperatures of 100 DEG  to 300 DEG  C.  A foraminate copper catalyst is preferred, especially when the process is continuous.  Suitable foraminate copper catalysts are foraminate copper-aluminium, copper-silicon and copper-zinc. Such catalysts are described in Specifications 621,749, 624,035 and 634,097.  Other copper-containing catalysts specified are copper-on-zinc oxide, copper-on-gamma alumina, copper chromite which may also contain magnesium, copper on magnesia, and copper on kieselguhr.  In the preparation of these catalysts the copper may be obtained as the oxide (see Group III) and it is then necessary to reduce to the metal before use.  This reduction step may be effected in situ if the temperature employed for hydrogenation is sufficiently high.  Very suitable catalysts for batch operation are copper catalysts prepared by the substantially complete extraction of the alloying metal from particles of alloys comprising copper and an alloying metal or metals more soluble in acid or alkali or other extracting liquid than copper.  These catalysts are obtained in powdered form and suitable alloys mentioned are those with aluminium, silicon, zinc and magnesium, the first two of which may be extracted with aqueous alkalis such as sodium and potassium hydroxide and the last two with aqueous acids.  The process may be carried out batchwise or continuously and in the latter case it is desirable to employ a reactor packed on the spaced and an inert granular material such as silica chips. In examples: (1) a copper-aluminium alloy prepared by melting electrolytic copper and pure aluminium in a graphite crucible, is crushed to particles of 1/8 inch to 1/4 inch mesh, and treated with hot aqueous sodium hydroxide at 100 DEG  C. until about 20 per cent of the aluminium is removed (see Group III).  The foraminate catalyst obtained is charged into a tubular converter into which 2,3-dihydropyran is injected and hydrogenation to tetrahydropyran is effected continuously at 250 DEG  C. and at 250 atmospheres pressure; (2) 2,5-dimethyl furan is hydrogenated to 2,5-dimethyl tetrahydrofuran in an autoclave using an excess of hydrogen and a foraminate copper-aluminium catalyst prepared as in (1); (3) and (4) 2,3-dihydropyran is hydrogenated in an autoclave to form tetrahydropyran, using a catalyst as in (10 and a copper-barium-chromite catalyst respectively.  Other starting materials specified are 2,3- and 2,5-dihydrofuran and furan, each of which yields tetrahydrofuran.