Patent GB-707993-A (GB)
Title: Process for the production of aliphatic alcohols
IPC: C07C29/16
Filed: 1951-02-02
Abstract: Aliphatic alcohols are made by contacting CO and H2 with an iron catalyst to give mainly oxygen-containing organic compounds, predominantly alcohols, and olefinic hydrocarbons, passing a mixture of the olefines and oxygen-containing compounds so obtained together with CO and H2 over a cobalt catalyst at elevated temperature and pressure and subjecting the product so obtained to catalytic reduction with H2 under such conditions that the greater part of the non-alcohol oxygen-containing compounds are converted into alcohols without reduction of the alcohols themselves.  Each stage may be conducted in several stages with recycling of unconverted reactants. The second stage is preferably effected at 120-220 DEG  C. and above 40 atmospheres with aqueous solutions of cobalt salts as catalysts acidified to a pH of 1-6.  From the products of each stage the CO2 and gaseous hydrocarbons formed are removed before passing to the next stage and it is advantageous to remove the aqueous fractions of the first stage to prevent undue dilution of the cobalt salts in the second stage.  The oxygen-containing organic compounds are separated from this aqueous fraction by distillation and passed to the second stage when also the hydrocarbons removed from the first stage, e.g. by an oil wash, may also be added.  The third stage is preferably effected in two stages.  Firstly aldehydes, ketones, hydroxy-aldehydes and similar oxygen-containing compounds are reduced to alcohols preferably using a fixed bed of reduced cobalt catalyst at 180-200 DEG  C. and upon which further quantities of cobalt deposit.  In the second reduction stage esters are converted into alcohols by using oxide, e.g. copper-chrome, catalysts at 200-250 DEG C. with hydrogen pressures of 150-250 kg./sq. cm.  Acetals obtained during the Oxo-synthesis are also converted to alcohols in the third stage of the process but better yields of alcohols may be obtained by effecting this stage in the presence of water so that hydrating hydrogenation results and aldehydes primarily produced by the decomposition of the acetals are converted to alcohols.  Hydrating hydrogenation is preferably effected with nickel catalysts, especially nickel and magnesium oxide or kieselguhr, although palladium, platinum and cobalt are also specified.  Temperatures are 160-180 DEG  C.  The quantity of water should exceed that required for the ether bonds which are to be split.  It may be added before hydrogenation or supplied in part as an aqueous catalyst solution in the Oxo-stage.  The final products consist mainly of alcohols and saturated hydrocarbons.  The alcohols may be separated, e.g. by azeotropic distillation, esterification with boric acid, fractional adsorption or selective extraction. When removing alcohols by distillation products boiling above 340 DEG  C. may be completely hydrogenated to yield paraffin wax or oxidized to waxes with nitrous gases or by alkali fusion.  In examples (1) in the first stage the catalyst contains 5 parts of Cu, 10 parts of CaO and 10 parts of kieselguhr per 100 parts of Fe and is prepared from the metal nitrates by the addition of boiling Na2CO3 solution at pH 9.2 to give an alkali content of the partially washed mass of 8.4 per cent K2O, which is dried to a 60 per cent water content, moulded and finally dried at 110 DEG  C. and reduced for 90 minutes with a gas comprising 75 per cent H2 and 25 per cent N2 at 310 DEG  C. at a linear gas velocity of 1.2 metres/sec.  Water gas containing 40 vols. CO, 50 vols. H2 and 10 vols. of inert gas is passed over the catalyst at 198 DEG  C. and 30 kg./sq. cm. at 100 vols. of gas per vol. of catalyst per hour with a recycle ratio of fresh feed to recycle gas of 1 : 2, gaseous hydrocarbons being removed by an oil wash and most of the CO2 also being removed, the aqueous phase is separated, distilled and added to the non-aqueous fractions together with distilled olefines and oxygen-containing organic compounds from the oil wash.  A part of this mixture is added to aqueous cobalt sulphate and reacted with water gas of the above composition at 140 DEG  C. and 190 kg./sq. cm. for 50 mins. when the catalyst solution is separated reduced cobalt added and treatment with hydrogen at 180-190 DEG  C. and 150 kg./sq. cm. effected for 20 mins. the product being rehydrogenated at 250 DEG C. and 200-250 kg./sq. cm. with a copper-chromium oxide catalyst to give alcohols which are separated by fractionation; and in (2) part of a fraction boiling between 50 and 360 DEG  C. cut from the initial synthesis products of (1), gaseous hydrocarbons, wax and aqueous products being eliminated, is mixed at pH 5.8 with aqueous cobalt and magnesium sulphates, treated for 90 minutes with water gas at 150-160 DEG  C. and 117-188 kg./sq. cm. and the products hydrogenated for 60 minutes at 160 DEG  C. and 150 kg./sq. cm. with or without the addition of water with a catalyst comprising metallic nickel, magnesium oxide and kieselguhr to give alcohols a higher yield being obtained when water is present.ALSO:A Fischer synthesis catalyst containing 5 parts Cu, 10 parts CaO and 10 parts kieselguhr per 100 parts of Fe is made by treating a solution of the corresponding metal nitrates with boiling sodium carbonate at pH 9.2, filtering, partially washing to a residual alkali content of 8.4 per cent. K2O, drying to a 60 per cent. water content, moulding in a thread press to give threads of 3.5 mms. thickness drying at 110 DEG C., comminuting, sieving and reducing for 90 mins. with a gas comprising 75 per cent. H2 and 25 per cent. N2 at 310 DEG C. with a linear gas velocity of 1-2 metres/secs. to give a catalyst which contains 70 per cent. of free iron relative to the total iron content. There is also described an oxo-synthesis catalyst comprising an aqueous solution which contains 13.6 gms. Co as CoSO4 and 21 gms. MgO as MgSO4 per litre and a pH of 5.8 and a hydration hydrogenation-catalyst comprising 12 parts MgO and 60 parts kieselguhr per 100 parts of metallic nickel.