Patent GB-670336-A (GB)
Title: Improvements in or relating to separation of the reaction products of the hydrogenation of oxides of carbon
IPC: C07C29/74
Filed: 1948-12-22
Abstract: The reaction product obtained in the hydrogenation of oxides of carbon is cooled to form an uncondensed gas product, an oil condensate product and an aqueous condensate product, each product containing oxygenated organic compounds, the oil condensate product is then scrubbed with water to remove a portion of the dissolved oxygenated compounds and form an aqueous solution thereof, the resulting aqueous solution together with said aqueous condensate product are then charged to a common distillation zone to obtain a relatively high boiling fraction, and said uncondensed gas product is scrubbed with a part of said high boiling fraction to obtain an aqueous solution of oxygenated compounds, and this solution is returned to the said common distillation zone.  The hydrogenation of the oxide of carbon may be effected at varying mol. ratios of hydrogen and an oxide of carbon, e.g. a ratio of 2 : 1 and the reaction may be effected at 300-700 DEG  F. and at pressures between atmospheric and 500 pounds per square inch, in the presence of a hydrogenation catalyst such as a reduced iron or cobalt catalyst according to conventional fixed bed or fluid bed operations.  The product comprises water, methane and higher hydrocarbons and oxygenated compounds comprising C2 and higher acids, methanol and higher alcohols, and aldehydes, ketones and esters.  The water scrubbing of the oil condensate product yields a lower water layer comprising dissolved oxygenated compounds and an upper oil layer containing hydrocarbons and these layers are separated.  The upper oil-layer is extracted with an aqueous solution of a water-soluble alcohol, e.g. aqueous methanol or ethanol, to yield an extract comprising oxygenated compounds and a small portion of hydrocarbons and a raffinate comprising hydrocarbons and a small portion of oxygenated compounds.  The extract is then treated with a hydrocarbon wash oil such as butane, pentane, hexane or heptane or mixtures thereof, to absorb hydrocarbons present in the extract, while the said raffinate is neutralized with alkali to obtain acid-free hydrocarbons and an aqueous solution of salts of organic acids.  The lower water layer from the oil scrubbing is combined with the initial water product liquid phase obtained on cooling the reaction product and the combined streams are fractionated into a low boiling fraction comprising non-acid oxygenated compounds such as alcohols, aldehydes, ketones and esters and a minor portion of organic acids, and a high boiling fraction comprising an aqueous mixture of relatively light organic acids and a portion of this high boiling fraction is used to scrub the uncondensed gas phase while another portion of this fraction is treated for the recovery of water-free organic acids. The scrubbing of the said gas phase yields a scrubbed gaseous effluent comprising mainly hydrocarbons and a minor portion of organic acids and a lower water layer comprising methanol and higher alcohols, C2 and higher aldehydes, ketones, acids and esters, and this lower water layer is then combined with the water layer from the oil scrubbing and with the initial water product liquid phase and the mixture fractionated as above, whereas the scrubbed gaseous effluent is neutralized to obtain acid-free hydrocarbons and an aqueous solution of salts of organic acids.  The extract obtained from the treatment of the upper oil layer with the aqueous alcohol is fractionated to remove the alcohol and the aqueous bottoms mixture comprising relatively heavy alcohols, aldehydes, ketones, acids and some esters is then hydrogenated to convert the aldehydes and ketones to their corresponding alcohols and this mixture is then treated with an aqueous solution of an alkali to yield an aqueous solution of alcohols and salts of the organic acids from which the free acids are obtained by acidifying with an inorganic acid such as sulphuric or hydrochloric acid.  The low-boiling fraction obtained on fractionation of the mixture obtained on combining the initial water product liquid phase and the lower water layers from the gas scrubbing and oil scrubbing is also hydrogenated to convert aldehydes and ketones to their corresponding alcohols and this resulting mixture is then treated with alkali to convert the organic acids present to their salts and to saponify the esters and the alcohols are separated from the salts.  Prior to the latter hydrogenating step the low-boiling fraction may be distilled to remove low-boiling components such as acetaldehyde, propionaldehyde, methanol, methyl ethyl ketone and acetone and the bottoms residue submitted to the hydrogenation.  The Specification as open to inspection under Sect. 91 states that both of the hydrogenation stages referred to above may be conducted so as to selectively hydrogenate the aldehydes to their corresponding alcohols without substantial hydrogenation of the ketones by conducting the hydrogenation at a temperature between 75 DEG  and 575 DEG  F., and at a pressure between 15 and 2000 pounds per square inch, in the presence of a hydrogenation catalyst which may comprise a metal having an atomic number greater than 23. Preferred catalysts are copper oxide, chromium oxide, copper chromite, zinc oxide, zinc chromite, nickel, ruthenium, molybdenum, silver, platinum, cobalt and iron.  The catalysts specified are mixtures of copper oxide and chromium oxide, which is preferably employed at between 200 DEG  and 225 DEG  F. and at a pressure of 300 to 500 pounds per square inch, or a mixture of zinc oxide and chromium oxide which is best employed at 250-300 DEG  F. and at 400-600 pounds per square inch pressure.  this subject-matter does not appear in the Specification as accepted.