IMPROVEMENTS IN OR RELATING TO THE MANUFACTURE OF NAPHTHENIC HYDROCARBONS BY HYDROGENATING THE CORRESPONDING AROMATIC HYDROCARBONS

1,247,278. Hydrogenating aromatics. INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LUBRIFIANTS. 5 Dec., 1969 [9 Dec., 1968], No. 59562/69. Heading C5E. The hydrogenation of aromatic hydrocarbons to naphthenes, e.g. of benzene to cyclohexane, in a liquid phase containing a suspended catalyst, e.g. Raney nickel, is carried out in two elongated and substantially vertical zones located one above the other, the lower zone consisting of a plurality of passageways and acting as a heat exchanger, liquid flowing downwardly through said zones and being externally recycled, and hydrogen gas flowing upwardly, 70-100% of the total H 2 being introduced into the upper zone and 0-30% into the lower zone. When liquid circulation is stopped for any reason, hydrogen is introduced into the bottom of the lower zone to prevent blockage of tubes by catalyst grains. In Fig. 1, circulating liquid comprising mainly cyclohexane plus suspended catalyst enters upper zone 3 from line 13 and descends to lower zone 7 before recycle via line 11 and pump 12. Benzene is introduced via line 1, and hydrogen through lines 2 and 10. Excess hydrogen and product cyclohexane vapour are withdrawn through pipe 6. Fresh catalyst may be introduced from lock chamber 14, the operation of which is described in detail. Lower zone 7 is cooled by coolant liquid, e.g. water, entering at 8 and leaving at 9. In preferred operation the benzene : cyclohexane weight ratio in the liquid phase is below 0À001/1.