Purification of N,N-dimethylacetamide
AssigneeMallinckrodt Inc.
InventorMichael J. Gentilcore
Life of this patent
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Abstract
A method to purify N,N-dimethylacetamide (DMAc) from an aqueous solution containing acetic acid as a contaminant. Two fractional distillation columns are arranged in a series. The solution containing the contaminant is provided to the first column with a temperature profile to result in acetic acid partitioning into the overhead water. The material remaining in the bottom portion of the first column is recycled to the first column and also provided into a second column, whereby DMAc free of acetic acid contamination is recovered, and remaining DMAc and acetic acid are returned to the first column for further separation. The method uses standard fractional distillation procedures and equipment, thus eliminating the need for more complex extractions and/or chromatographic separations.
Claims27
A method of separating DMAC from an aqueous DMAC solution containing acetic acid comprising
- (a) providing said solution to a first distillation column, said column having a feed port and an entry port, and having top and bottom portions, said bottom portion having upper, mid, and lower bottom portions, at a temperature sufficient to render the lower bottom portion of the column substantially dry and the upper bottom portion of the column substantially wet, and to partition acetic acid between an overhead stream and a bottom stream of the first column,
- (b) providing the bottom stream of the first column to an entry port of a second distillation column to partition purified DMAc into an overhead stream and a mixture of DMAc and acetic acid into a bottom stream, and
- (c) partitioning an additional portion of the acetic acid from the mixture of DMAc and acetic acid to the overhead stream of the first column.
An apparatus to separate fluid components in a feed solution comprising
- (a) a first distillation column in series with a second distillation column, the first distillation column having a feed port for a solution, an overhead condenser for an overhead distilled stream, a reboiler for a bottom distilled stream, and an exit port, the column having top and bottom portions, the bottom portion having upper, middle, and lower bottom portions,
- (b) the second distillation column having a feed port for the distilled bottom stream from the first column, an overhead condenser for a distilled overhead stream, an optional bottoms reboiler, and an exit port,
- (c) a pump to provide the bottoms product stream from the second column to the first column, and
- (d) a control to regulate a temperature profile wherein the upper bottom portion of the column is substantially wet and the lower bottom portion of the column is substantially dry.
A method to purify N,N-dimethylacetamide (DMAc) from acetic acid in an aqueous solution comprising
- providing said solution to a feed port of a first distillation column under conditions sufficient to partition aqueous acetic acid as a distillate from the first column,
- providing a pumparound of a non-distillate bottoms product from a bottom of the first column to the first column feed port and to a second distillation column under conditions sufficient to distill substantially purified DMAc as a distillate from the second column, and
- providing a non-distillate bottoms product from the second column containing DMAc and acetic acid to the first column to further partition aqueous acetic acid to the overhead of the first column, and separating DMAc to the bottoms of the first column.
A purification method for at least one component in a solution having a first lower boiling component, a second higher boiling component, and a third component that forms a binary high boiling azeotrope with the second component, the method comprising
- (a) providing said solution to a first distillation column, said column having a feed port and an entry port, and having top and bottom portions, said bottom portion having upper, mid, and lower bottom portions, at a temperature sufficient to render the lower bottom portion of the column substantially free of the first component and the upper bottom portion of the column substantially rich in the first component, and to partition the third component between an overhead stream and a bottom stream of the first column,
- (b) providing the bottom stream of the first column to an entry port of a second distillation column to partition a substantially purified second component into an overhead stream and a mixture of the second and third components into a bottom stream, and
- (c) providing the bottom stream from the second column to the feed port of the first column to partition an additional portion of the third component from the mixture of second and third components to the overhead stream of the first column, wherein (i) the first component is a low boiling compound and is present in a feed stock, a concentration of at least about 25%;
- (ii) the second component is a high boiling compound relative to the first component and is present in the feed stock, at a concentration of at least about 5%;
- (iii) the third component is present in the feed stock, that is, at a concentration of at most about 5% and forms a high boiling azeotrope with the second component;
- and
- (d) the first component can cancel, control, or mitigate the two component azeotrope.
Dependencies are inferred from the claim text.