Staged purification of contaminated propylene oxide
First Claim
1. A process for separating contaminating quantities of hexenes, hexanes, pentenes, pentanes, butenes, methanol, water and oxygen-containing impurities from impure propylene oxide which comprises:
- fractionating said impure propylene oxide in a first distillation column under distillation conditions selected to provide a first overhead distillation fraction comprising essentially all of the pentenes, pentanes and butenes and most of the oxygen-containing and hydrocarbon impurities boiling above propylene oxide and a partially purified first propylene oxide bottoms fraction comprising propylene oxide, hexenes, hexanes, water and only residual quantities of pentenes and pentanes,extractively distilling said first propylene oxide bottoms fraction in a second extractive distillation column in the presence of a C2 to C6 alkylene glycol extractive distillation agent to form a second overhead fraction comprising propylene oxide, hexenes, hexanes, water, residual quantities of pentenes and pentanes and oxygen-containing impurities boiling above propylene oxide, and a second bottoms fraction comprising the extractive distillation agent, water, methanol and oxygen-containing impurities boiling below propylene oxide,extractively distilling said second overhead fraction in a third extractive distillation column in the presence of a C7 to C10 alkane hydrocarbon extractive distillation agent to form a third overhead fraction comprising the extractive distillation agent and propylene oxide enriched with the oxygen-containing impurities boiling above propylene oxide and a third bottoms fraction comprising the extractive distillation agent, propylene oxide, hexenes, hexanes, and residual quantities of pentenes and pentanes, andextractively distilling said third bottoms fraction in a fourth extractive distillation column in the presence of a C7 to C10 alkane hydrocarbon extractive distillation agent to form a fourth overhead fraction consisting essentially of propylene oxide and a fourth bottoms fraction comprising the extractive distillation agent, hexenes, and hexanes.
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Accused Products
Abstract
Contaminants are removed from impure propylene oxide by fractionating in a first column to remove overhead essentially all of the pentenes and pentanes and most of the oxygen-containing impurities to provide a partially purified first propylene oxide bottoms fraction, extractively distilling the first bottoms fraction in a second extractive column using a C2 to C6 alkylene glycol extractive distillation agent to form a second overhead fraction comprising propylene oxide, hexenes, hexanes, water, residual quantities of pentenes and pentanes and oxygen-containing impurities, extractively distilling the second overhead fraction in a third column using a C6 to C10 alkane hydrocarbon extractive distillation agent to form a third bottoms fraction comprising the extractive distillation agent, propylene oxide, hexenes, hexanes, residual quantities of pentenes and pentanes and water, and extractively distilling said third bottoms fraction in a fourth column using a C6 to C10 alkane hydrocarbon extractive distillation agent to form a fourth overhead fraction consisting essentially of propylene oxide.
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Citations
17 Claims
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1. A process for separating contaminating quantities of hexenes, hexanes, pentenes, pentanes, butenes, methanol, water and oxygen-containing impurities from impure propylene oxide which comprises:
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fractionating said impure propylene oxide in a first distillation column under distillation conditions selected to provide a first overhead distillation fraction comprising essentially all of the pentenes, pentanes and butenes and most of the oxygen-containing and hydrocarbon impurities boiling above propylene oxide and a partially purified first propylene oxide bottoms fraction comprising propylene oxide, hexenes, hexanes, water and only residual quantities of pentenes and pentanes, extractively distilling said first propylene oxide bottoms fraction in a second extractive distillation column in the presence of a C2 to C6 alkylene glycol extractive distillation agent to form a second overhead fraction comprising propylene oxide, hexenes, hexanes, water, residual quantities of pentenes and pentanes and oxygen-containing impurities boiling above propylene oxide, and a second bottoms fraction comprising the extractive distillation agent, water, methanol and oxygen-containing impurities boiling below propylene oxide, extractively distilling said second overhead fraction in a third extractive distillation column in the presence of a C7 to C10 alkane hydrocarbon extractive distillation agent to form a third overhead fraction comprising the extractive distillation agent and propylene oxide enriched with the oxygen-containing impurities boiling above propylene oxide and a third bottoms fraction comprising the extractive distillation agent, propylene oxide, hexenes, hexanes, and residual quantities of pentenes and pentanes, and extractively distilling said third bottoms fraction in a fourth extractive distillation column in the presence of a C7 to C10 alkane hydrocarbon extractive distillation agent to form a fourth overhead fraction consisting essentially of propylene oxide and a fourth bottoms fraction comprising the extractive distillation agent, hexenes, and hexanes.
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2. A distillation process for the purification of impure propylene oxide contaminated with isobutylene, hexenes, hexanes, pentenes, pentanes, methanol, water and oxygen-containing and hydrocarbon impurities which comprises the steps of:
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charging said impure propylene oxide to a first distillation column under distillation conditions selected to provide a first overhead distillation fraction comprising essentially all of the isobutylene, pentenes and pentanes and most of the oxygen-containing and hydrocarbon impurities boiling above propylene oxide and a partially purified first propylene oxide bottoms fraction comprising propylene oxide, hexenes, hexanes, water and only residual quantities of isobutylene, pentenes and pentanes, separately charging said first propylene oxide bottoms fraction and a C2 to C6 alkylene glycol extractive distillation agent to a second extractive distillation column and separating said first proylene oxide bottoms fraction therein into a second overhead fraction comprising propylene oxide, hexenes, hexanes, residual quantities of pentenes and pentanes, water, methanol and oxygen-containing impurities boiling above propylene oxide, and a second bottoms fraction comprising the extractive distillation agent, water, methanol and oxygen-containing impurities boiling below propylene oxide, separately charging said second overhead fraction and a C7 to C10 alkane hydrocarbon extractive distillation agent to a third extractive distillation column at ascending charge points and separating said second overhead fraction therein into a third overhead fraction comprising the extractive distillation agent and propylene oxide enriched with oxygen-containing impurities boiling above propylene oxide, methanol and water and a third bottoms fraction comprising the extractive distillation agent, propylene oxide, hexenes, hexanes and residual quantities of pentenes and pentanes and other impurities, separately charging said third bottoms fraction and a C7 to C10 alkane hydrocarbon extractive distillation agent to a fourth extractive distillation column at ascending charge points and separating said third bottoms fraction therein into a fourth overhead fraction consisting essentially of propylene oxide and a fourth bottoms fraction comprising the extractive distillation agent, hexenes, and hexanes.
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3. A distillation process for the purification of impure propylene oxide contaminated with isobutylene, hexenes, hexanes, pentenes, pentanes, water and oxygen-containing and hydrocarbon impurities including propylene, propane, acetaldehyde, methyl formate, propionaldehyde, acetone, methanol, tertiary butyl alcohol, isopropyl alcohol, and tertiary butyl formate which comprises the steps of:
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fractionating said impure propylene oxide in a first distillation column under distillation conditions selected to provide a first overhead distillation fraction comprising essentially all of the isobutylene, pentenes and pentanes and most of the oxygen-containing impurities boiling above propylene oxide including the propylene, propane, acetaldehyde, and substantially all of the pentenes and pentanes and a partially purified first propylene oxide bottoms fraction comprising propylene oxide, hexenes, hexanes, water and only residual quantities of pentenes and pentanes and isogutylene, separately charging said first propylene oxide bottoms fraction and a C2 to C6 alkylene glycol extractive distillation agent to a second extractive distillation column at ascending charge points and separating said first propylene oxide bottoms fraction therein into a second overhead fraction comprising propylene oxide, hexenes, hexanes, residual quantities of pentenes and pentanes, acetaldehyde, methyl formate, methanol, isobutylene and water, and a second heavier distillation fraction comprising the extractive distillation agent, water, methanol and other oxygen-containing impurities boiling below propylene oxide, separately charging said second overhead fraction and a C7 to C10 alkane hydrocarbon extractive distillation agent to a third extractive distillation column at ascending charge points and separating said second overhead fraction therein into a third lighter distillation fraction comprising the extractive distillation agent and propylene oxide enriched in oxygen-containing impurities including acetaldehyde, methyl formate, methanol and water and a third bottoms fraction comprising the extractive distillation agent, propylene oxide, hexenes, hexanes, residual quantities of pentenes and pentanes and water, separately charging said third bottoms fraction and a C7 to C10 alkane hydrocarbon extractive distillation agent to a fourth extractive distillation column at ascending charge points and separating said third bottoms fraction therein into a fourth overhead fraction consisting essentially of propylene oxide and a fourth heavier fraction comprising the extractive distillation agent, hexenes, hexanes, residual quantities of pentenes and pentanes and water. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification