Recovery of purified and substantially anhydrous propylene oxide
First Claim
1. In a distillation method for the purification of crude propylene oxide containing contaminating quantities of water, acetaldehyde and methanol wherein the crude propylene oxide is partially purified in a plural stage distillation zone to provide a vaporized overhead distillate propylene oxide fraction consisting essentially of propylene oxide and not more than about 0.2 wt. % of vaporized water, the improvement which comprises the step of:
- passing said propylene oxide vapor fraction through a drying chamber containing a porous hygroscopic solid absorbent at a temperature of about 34°
to about 100°
C. and a pressure of about 15 to about 30 psia, to selectively absorb water vapor onto the absorbent,and liquefying and recovering the thus-dehydrated purified propylene oxide.
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Accused Products
Abstract
A distillation method for the purification of crude propylene oxide containing contaminating quantities of water and methanol by partially purifying the crude propylene oxide in a plural stage distillation zone to provide a vaporized overhead distillate propylene oxide fraction containing a minor contaminating amount of vaporized water, and
passing the propylene oxide vapor fraction through a drying chamber containing a porous hygroscopic solid absorbent to selectively absorb water vapor onto the absorbent,
and liquefying and recovering the thus-dehydrated purified propylene oxide.
24 Citations
17 Claims
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1. In a distillation method for the purification of crude propylene oxide containing contaminating quantities of water, acetaldehyde and methanol wherein the crude propylene oxide is partially purified in a plural stage distillation zone to provide a vaporized overhead distillate propylene oxide fraction consisting essentially of propylene oxide and not more than about 0.2 wt. % of vaporized water, the improvement which comprises the step of:
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passing said propylene oxide vapor fraction through a drying chamber containing a porous hygroscopic solid absorbent at a temperature of about 34°
to about 100°
C. and a pressure of about 15 to about 30 psia, to selectively absorb water vapor onto the absorbent,and liquefying and recovering the thus-dehydrated purified propylene oxide. - View Dependent Claims (2, 3)
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4. A distillation method for the purification of crude propylene oxide containing contaminants comprising water, acetaldehyde and methanol which comprises the steps of:
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charging the crude propylene oxide to a first distillation column and operating the first distillation column under distillation conditions of temperature and pressure selected to provide a first lighter liquid distillation fraction comprising acetaldehyde and a first heavier liquid distillation fraction comprising propylene oxide, water and methanol, charging the first heavier distillation fraction to a second distillation column and operating the second distillation column under distillation conditions of temperature and pressure selected to provide a second lighter liquid distillation fraction comprising propylene oxide, less than half of the water charged to the second distillation column and more than half of the methanol charged to the second distillation column and a second heavier liquid distillation fraction comprising more than half of the water charged to the second distillation column and less than half of the methanol charged to the second distillation column, charging the second lighter distillation fraction to a third extractive distillation column and also charging an effective amount of a C8 to C10 paraffinic hydrocarbon extractive distillation agent thereto and operating the third distillation column under extractive distillation conditions of temperature and pressure selected to provide a third lighter liquid distillation fraction comprising the extractive distillation agent, substantially less than 50% of the water charged to the third distillation column and substantially all of the methanol charged to the third distillation column and a third heavier liquid distillation fraction comprising propylene oxide and than less than half of the water charged to the third distillation column, charging the third heavier distillation fraction to a fourth extractive distillation column and also charging an effective amount of a C8 to C10 paraffinic hydrocarbon extractive distillation agent thereto and operating the fourth distillation column under extractive distillation conditions of temperature and pressure selected to provide a fourth lighter vapor overhead distillate fraction comprising propylene oxide and less than half of the water charged to the fourth distillation column and a fourth heavier liquid distillation fraction comprising the extractive distillation agent and more than half of the water charged to the fourth distillation column, passing said propylene oxide vapor fraction through a drying chamber containing a porous hygroscopic solid absorbent at a temperature of about 34°
to about 100°
C. and a pressure of about 15 to about 30 psia, to selectively absorb water vapor onto the absorbent,and liquefying and recovering the thus-dehydrated purified propylene oxide. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A distillation method for the purification of crude propylene oxide containing contaminating quantities of water, C5 and C6 hydrocarbons, methyl formate, acetaldehyde, propionaldehyde, methanol, tertiary butyl alcohol and acetone which comprises the steps of:
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charging the crude propylene oxide to a first distillation column and operating the first distillation column under distillation conditions of temperature and pressure selected to provide a first lighter liquid distillation fraction comprising C5 hydrocarbons, methyl formate, acetaldehyde and a first heavier liquid distillation fraction comprising propylene oxide, water, methanol, tertiary butyl alcohol, acetone, acetaldehyde, propionaldehyde and C6 hydrocarbons, charging the first heavier distillation fraction to a second distillation column and operating the second distillation column under distillation conditions of temperature and pressure selected to provide a second lighter liquid distillation fraction comprising propylene oxide, less than half of the water charged to the second distillation column, more than half of the methanol charged to the second distillation column, methyl formate, acetaldehyde and C6 hydrocarbons, and a second heavier liquid distillation fraction comprising more than half of the water charged to the second distillation column, less than half of the methanol charged to the second distillation column, acetone, tertiary butyl alcohol and propionaldehyde, charging the second lighter distillation fraction to a third extractive distillation column and also charging an effective amount of a C8 to C10 paraffinic hydrocarbon extractive distillation agent thereto and operating the third distillation column under extractive distillation conditions of temperature and pressure selected to provide a third lighter liquid distillation fraction comprising the extractive distillation agent, substantially less than 50% of the water charged to the third distillation column, substantially all of the methanol charged to the third distillation column, methyl formate and acetaldehyde and a third heavier liquid distillation fraction comprising propylene oxide, less than half of the water charged to the third distillation column, and C6 hydrocarbons, charging the third heavier distillation fraction to a fourth extractive distillation column and also charging an effective amount of a C8 to C10 paraffinic hydrocarbon extractive distillation agent hereto and operating the fourth distillation column under extractive distillation conditions of temperature and pressure selected to provide a fourth lighter vapor overhead distillate fraction comprising propylene oxide and less than half of the water charged to the fourth distillation column and a fourth heavier liquid distillation fraction comprising the extractive distillation agent, more than half of the water charged to the fourth distillation column, and C6 hydrocarbons, passing said propylene oxide vapor fraction through a drying chamber containing a porous hygroscopic solid absorbent at a temperature of about 34°
to about 100°
C. and a pressure of about 15 to about 30 psia, to selectively absorb water vapor onto the absorbent,and liquefying and recovering the thus-dehydrated purified propylene oxide. - View Dependent Claims (15, 16, 17)
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Specification