Recovery of alcohols from hydration of olefins

摘要

In the production of a pure ether-free alcohol by the reaction of an olefin with steam in a reaction zone in the presence of a hydration catalyst at 150-375 DEG C., preferably 200 to 250 DEG C., and under a pressure of from atmospheric to 3000 and preferably from 50 to 1000 pounds per square inch gauge, whereby a vaporous mixture of reaction products comprising alcohol, ether and unreacted olefin is obtained, the vaporous mixture is continuously fed to an extractive distillation zone, using water as solvent, maintained at substantially the same temperature and pressure as the said reaction zone, additional heat being supplied to said zone, and said reaction products undergoing continuous fractional distillation in said zone whereby the ether and unreacted olefin are substantially completely separated from the alcohol as an overhead stream and the pure ether-free alcohol is obtained from the extractive distillation zone in the form of an aqueous solution, the said ether and unreacted olefin being recycled to the reaction zone. The invention is restricted to the production of saturated aliphatic monohydric alcohols, e.g. ethanol and isopropanol, which are stable and at least partially miscible with water at the temperatures and pressures employed. The hydration catalyst used is generally an acid type catalyst, e.g. an aqueous acid such as dilute sulphuric or dilute phosphoric acid or the catalyst may be in solid form, e.g. phosphoric acid on a carrier such as alumina. The water used in the extractive distillation zone may contain impurities consisting of small amounts of salts, acids or alkalis, e.g. sodium acetate, sulphuric acid or sodium hydroxide. In the figure an olefin-containing gas is admitted to the system through line 1 and after compression is admixed with recycle gas from the extractive distillation column 7 in the hydration reaction zone 3 into which water is fed through line 4 usually in an amount sufficient to furnish the steam used up by the hydration reaction. The vaporous product mixture comprising alcohol, ether, steam, unconverted olefin and other hydrocarbon gases leave the reaction zone via line 5 and pass to the extractive distillation zone 7 where the temperature is substantially the same as in the reaction zone. Usually, however, it is necessary to add small quantities of heat to the vapours by means of a superheater 6, or alternatively the pressure of the vapours may be decreased. Water is fed to the extractive distillation zone via line 8 while additional heat is provided, e.g. in the form of direct steam which is admitted through line 22a to effect distillation throughout the column. The temperature of the water fed to the extractive distillation zone is regulated externally, e.g. by heater 9, so that the distilled vapours of ether, unreacted olefin, hydrocarbon impurities and a little alcohol vapour are saturated with steam in the right ratio for recycling to the reaction zone via line 12, a small sidestream being withdrawn through pressure-reducing valve 11 in order to purge the low boiling hydrocarbons present in the olefin feed. The amount of water added to the top of the extractive distillation zone should be enough to absorb more than 80 per cent of the alcohol present in the vaporous product and should be such that the concentration of the homogeneous internal reflux in the extractive distillation zone is in the range of 65-99.9 mol. per cent water and preferably 95-99 mol. per cent water. Hot dilute aqueous alcohol is removed under pressure via line 14 and passes to the alcohol still 15 in which a large part of the water is removed and returned through line 8 and heater 9 to the top of the extractive distillation zone 7 whilst the concentrated alcohol vapours pass overhead to a condenser from which liquid reflux is returned to the still, the purified alcohol being withdrawn through line 18. Specifications 495,231 and 663,561, [Group III], are referred to.ALSO:In the production of a pure ether-free alcohol by the reaction of an olefin with steam in a reaction zone in the presence of a hydration catalyst at 150-375 DEG C., preferably 200 to 250 DEG C., and under a pressure of from atmospheric to 3,000, and preferably from 50 to 1,000 lb. per sq. in. gauge, whereby a vaporous mixture of reaction products comprising alcohol, ether and unreacted olefin is obtained the vaporous mixture is fed continuously to an extractive distillation zone, using water as solvent, maintained at substantially the same temperature and pressure as the said reaction zone, additional heat being supplied to said zone, and said reaction products undergoing continuous fractional distillation in said zone whereby the ether and unreacted olefin are substantially completely separated from the alcohol as an overhead stream and the pure ether-free alcohol is obtained from the extractive distillation zone in the form of an aqueous solution, the said ether and unreacted olefin being recycled to the reaction zone. The invention is restricted to the production of saturated aliphatic monohydric alcohols, e.g. ethanol and isopropanol, which are stable and at least partially miscible with water at the temperature and pressures employed. The hydration catalyst used is generally an acid type catalyst, e.g. an aqueous acid, such as dilute sulphuric or dilute phosphoric acid, or the catalyst may be in solid form, e.g. phosphoric acid on a carrier such as as alumina. The water used in the extractive distillation zone may contain impurities consisting of small amounts of salts, acids or alkalis, e.g. sodium acetate, sulphuric acid or sodium hydroxide. In the figure an olefin-containing gas is admitted to the system through line 1 and after compression is admixed with recycle gas from the extractive distillation column 7 in the hydration reaction zone 3 into which water is fed through line 4 usually in an amount sufficient to furnish the steam used up by the hydration reaction. The vaporous product mixture comprising alcohol, ether, steam, unconverted olefin and other hydrocarbon gases leave the reaction zone via line 5 and pass to the extractive distillation zone 7 where the temperature is substantially the same as in the reaction zone. Usually, however, it is necessary to add small quantities of heat to the vapours by means of superheater 6, or alternatively the pressure of the vapours may be decreased. Water is fed to the extractive distillation zone via line 8 while additional heat is provided, e.g. in the form of direct steam which is admitted through line 22a to effect distillation throughout the column. The temperature of the water fed to the extractive distillation zone is regulated externally, e.g. by heater 9 so that the distilled vapours of ether, unreacted olefin, hydrocarbon impurities and a little alcohol vapour are saturated with steam in the right ratio for recycling to the reaction zone via line 12, a small sidestream being withdrawn through pressure-reducing valve 11 in order to purge the low boiling hydrocarbons present in the olefin feed. The amount of water added to the top of the extractive distillation zone should be enough to absorb more than 80 per cent. of the alcohol present in the vaporous product and should be such that the concentration of the homogeneous internal reflux in the extractive distillation zone is in the range of 65-99.9 mol per cent. water and preferably 95-99 mol per cent. water. Hot dilute aqueous alcohol is removed under pressure via line 14 and passes to the alcohol still 15 in which a large part of the water is removed and returned through line 8 and heater 9 to the top of the extractive distillation zone 7 whilst the concentrated alcohol vapours pass overhead to a condenser from which liquid reflux is returned to the still, the purified alcohol being withdrawn through line 18. Specifications 495,231 and 663,561 are referred to.