Patent GB-682154-A (GB)
Title: Improvements in or relating to a process for recovering the products of catalytic hydrogenation of oxides of carbon
IPC: C07C9/14
Filed: 1948-02-12
Abstract: The products of catalytic hydrogenation of oxides of carbon are recovered by cooling said products to effect substantial condensation of normally liquid components to form an oil product liquid phase and a water product liquid phase, subjecting the oil product liquid phase to extraction treatment with an aqueous solution of a non-acid solvent for oxygenated organic compounds to obtain a raffinate containing hydrocarbons and an extract containing oxygenated compounds, solvent and water, subjecting said extract to distillation to obtain a fraction containing said oxygenated compounds and water and a fraction containing said solvent, and separating said oxygenated compounds from said water. The preferred extracting solvent is an alcohol especially methanol and the solvent containing fraction is preferably recycled to the first mentioned extraction step.  The gas phase which separates on cooling the initial reaction product may be scrubbed with water or an aqueous solution containing oxygenated organic compounds and the water used may then be employed to scrub the oil product liquid phase.  The resulting aqueous solution containing dissolved oxygenated compounds may then be combined with the water product liquid phase resulting from the extraction of the oil phase.  The scrubbed oil comprises a mixture of organic acids, alcohols, esters, aldehydes, ketones and hydrocarbons and is then subjected to the extraction treatment with the aqueous solution of a solvent for oxygenated compounds, e.g. aqueous methanol.  The resulting extract may contain some hydrocarbons in solution as well as the oxygenated compounds and before subjecting it to distillation it is therefore preferable to remove these hydrocarbons by treating the extract with a hydrocarbon wash oil which is readily separable from the oxygenated compounds by distillation.  Suitable wash oils are n-pentane or other hydrocarbon having not more than eight carbon atoms per molecule, e.g. butane, hexane, heptane or octane or a mixture thereof.  Olefins such as isobutylene, butylene, pentene and hexene may also be used.  The wash oil is preferably added to the vessel in which the extraction treatment with the aqueous solvent is carried out so as to effect a single extraction step.  Besides aqueous methanol the extraction may be effected with an aqueous solution of other solvents, e.g. ethanol, propanol, glycols, ketones such as acetone or methyl ethyl ketone; aldehydes, e.g. acetaldehyde, esters, e.g. ethyl acetate or methyl acetate; or mixtures of the said solvents.  The fraction containing oxygenated compounds obtained on distillation of the extract is treated with alkali to convert the organic acids present to their salts which are then separated.  The salts may then be acidified with an inorganic acid which has a boiling point higher than that of water, e.g. sulphuric acid, or which forms a maximum boiling azeotrope with water, e.g. hydrochloric acid, to convert them to the organic acids.  The latter may then p  be combined with the aqueous light organic acids obtained on distillation of the water product liquid phase.  The fraction containing oxygenated compounds and water obtained on distillation of the extract separates into two phases on standing and the lower water layer which contains alcohols may be combined with the water product liquid phase.  The water product liquid phase may be fractionated into a relatively high boiling fraction comprising acids having at least two carbon atoms per molecule and a relatively low boiling fraction comprising alcohols having not more than six carbon atoms per molecule and these alcohols may be combined with the alcohols obtained from the extraction of the oil product liquid phase and the mixture subjected to extraction treatment, e.g. with a low boiling hydrocarbon such as n-pentane, to extract any relatively high boiling contaminating hydrocarbons.  The relatively low boiling fraction containing alcohols obtained on fractionation of the water product liquid phase may be treated with alkali to convert the organic acids present to their salts and to polymerize aldehydes and the product of the alkali treatment separated into an aqueous lower phase containing said salts and a non-aqueous upper phase containing aldehyde polymers.  The process is described in detail with reference to conventional apparatus and methanol, acetaldehyde, propionaldehyde, acetone, methyl ethyl ketone, aqueous ethanol, anhydrous propanol, C4 and higher alcohols, anhydrous acetic acid and other water-free light and heavy organic acids are recovered at various stages of the process the alcohols being previously purified by catalytic hydrogenation to to convert any aldehydes and ketones present to the alcohols.