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US 4,064,147 AGranted
Process for the production of aromatic mononitro compounds
AssigneeBayer Aktiengesellschaft
InventorsBernd Thelen, Wolfgang Auge, Karl-Werner Thiem
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AssigneeBayer Aktiengesellschaft
InventorsBernd Thelen, Wolfgang Auge, Karl-Werner Thiem
Estimating the term…
Aromatic mononitro compounds are prepared by nitrating aromatic compounds with nitric acid having a concentration between 70 and 100% by weight, working up of the nitration mixture in a rectification column and separation of the aromatic mononitro compound. In the nitration mixture and in the rectification column, depending upon the concentration of the nitric acid present, the ratio by weight of nitric acid plus water is controlled and not lowered below defined figures. Optionally water or nitric acid is introduced into the rectification column. BACKGROUND
In a process for the production of aromatic compounds by nitrating aromatic compounds with nitric acid having a concentration between 70 and 100% by weight, working up of the nitration mixture by distillation and separation of the aromatic nitro compounds, the improvement which comprises, that in the nitration mixture, depending from the concentration of the nitric acid being present, the ratio by weight of nitric acid plus water to organic components is not lower than 3 (when nitric acid having a concentration of 70% by weight is present) and 8 (when nitric acid having a concentration of 100% by weight is present), that the nitration mixture is worked up in a rectification column, whereby in said rectification column the minimum value of the ratio by weight of nitric acid plus water to organic components are not lower than 3 (when nitric acid having a concentration of 70% by weight and aromatic compounds having 1 aromatic nucleus or when nitric acid having a concentration of 78% by weight and aromatic compounds having more than one aromatic nucleus are present) and 8 (when nitric acid having a concentration of 100% by weight and aromatic compounds having one or more aromatic nucleus are present), that the nitration mixture is fed into the rectification part of said rectification column, that at the top of said rectification column a more concentrated nitric acid than in the nitration mixture is withdrawn and that in the sump of said rectification column a concentration of nitric acid between 66 and 70% by weight is maintained when nitration mixtures from the nitration of relatively reactive aromatic compounds are worked up and a concentration of nitric acid between 66 and 85% by weight is maintained when nitration mixtures from the nitration of relatively low reactive aromatic compounds are worked up, but a concentration of nitric acid lower than in the nitration mixture is always maintained, and that the aromatic mononitro compounds are separated out of the product discharged at the sump of the rectification column.
In a process for the production of 1-nitro anthraquinone by nitrating anthraquinone with nitric acid having a concentration between 85 and 100% by weight, working up of the nitration mixture by distillation and separation of 1-nitro anthraquinone by mechanical separation, the improvements comprising that the process is carried out in such a manner that in the nitration mixture, depending upon the concentration of nitric acid being present, the ratio by weight of nitric acid plus water to organic components is not lower than 5 (when nitric acid having a concentration of 85% by weight is present) and 8 (when nitric acid having a concentration of 100% by weight is present) and, that the nitration mixture is worked up in a rectification column, that in said rectification column, depending on the concentration of the nitric acid present, the ratio by weight is not below 3 (when nitric acid having a concentration of 78% by weight is present) and 8 (when nitric acid having a concentration of 100% is present), that the nitration mixture is introduced into the part of the rectification column where rectification takes place, that at the top of said rectification column a nitric acid having a higher concentration than the nitric acid in the nitration mixture and a concentration between 90 and 100% by weight is withdrawn, that below the point where the nitration mixture is introduced water or nitric acid having a concentration below the concentration of nitric acid in the nitration mixture but not higher than 90% by weight is added, that in the sump a lower concentration of nitric acid than in the nitration mixture and between 66 and 85% by weight is set up and that 1-nitro anthraquinone is separated out of the product discharged at the sump of the rectification column.
In the production of mononitro benzene, mononitro toluene, chlorobenzene, mononitro dichlorobenzene or mononitro naphthalene by nitration of benzene, toluene, chlorobenzene, dichlorobenzene or naphthalene, the improvement comprising that the process is carried out in a manner that the nitration is carried out in nitric acid having a concentration between 70 and 100% by weight, depending upon the concentration of the nitric acid being present during the nitration, the ratio by weight of nitric acid plus water to organic components is not lower than 3 (when nitric acid having a concentration of 70% by weight is present) and 10 (when nitric acid having a concentration of 100% by weight is present), that the nitration mixture is introduced into the rectification part of a rectification column which contains altogether 1 to 20 theoretical plates, in which the ratio by weight of nitric acid plus water to organic components is not below the values given above for the nitration, at the top of which a more concentrated nitric acid than in the nitration mixture is withdrawn and in the sump of which a concentration of nitric acid between 66 and 70% by weight but always a lower concentration of nitric acid than in the nitration mixture is set up, and from the product discharged at the sump mononitro benzene, mononitro toluene, mononitro chlorobenzene, mononitrodichlorobenzene or mononitro naphthalene is obtained, optionally after dilution and/or cooling by phase separation.
Dependencies are inferred from the claim text.
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Preparation of nitro compounds: by substitution of hydrogen atoms by nitro groups
Containing only six-membered rings: anthracenes; Hydrogenated anthracenes
Acyclic or carbocyclic compounds
Term ended 20 Dec 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to a process for the production of aromatic mononitro compounds in which aromatic compounds are nitrated with nitric acid having a concentration between 70 and 100% by weight, working up of the nitration mixture by distillation and separation of the aromatic mononitro compounds.
It is known that certain aromatic mononitro compounds can be obtained by nitrating aromatic compounds with highly concentrated nitric acid. For example, it is known to produce 1-nitro anthraquinone from anthraquinone using nitric acid having a concentration of 85 to 100% by weight, to produce mononitro chlorobenzene from chlorobenzene with nitric acid having a density of 1.52 (this corresponds to nitric acid having a concentration of 98% by weight) to produce mononitro benzene from benzene using nitric acid having a concentration from 65 to 70% by weight. Thereby an excess of nitric acid is generally applied.
Because also nitro compounds having more than one nitro moiety in the molecule can be obtained in the nitration of aromatic compounds, the nitration mixture is normally diluted with a great amount of ice or water followed by isolation of the mononitro compound. Thereby the nitric acid is diluted to such a degree that it is not possible to reconcentrate it in an economic manner for a re-use in nitrations with highly concentrated nitric acid.
In a mixing vessel 123.55 kg/h of nitric acid having a concentration of 95.5% and 11.18 kg/h of anthraquinone are mixed and dissolved continuously at 20.degree. to 25.degree. C with an average residence time of about 8 minutes. In the following tubular reactor the nitration is continued at 25.degree. to 45.degree. C with an average residence time of about 21 minutes in an adiabatic manner. The reaction mixture discharged from the reactor contains besides nitric acid having a concentration of 93.9% in dissolved form a mixture of 74.5 percent by weight 1-nitro-anthraquinone, 8.7 percent by weight of 2-nitro-anthraquinone, 9.5% by weight of dinitroanthraquinones and 6.9% by weight of anthraquinone. The reaction mixture is introduced on the third plate of a rectification column having 5 plates. At the top of the column 83.5 kg/h of nitric acid having a concentration of 99% is withdrawn, whereby a reflux ratio of 0.35:1 is maintained. Into the sump of the rectification column 31.69 kg/h of nitric acid having a concentration of 70% by weight is added. At the sump of the column 81.99 kg/h of a mixture is obtained, which shows a concentration of nitric acid of 77.5% and a ratio by weight of nitric acid + water to organic components of 5. The rectification column is operated at a pressure at the top of 200 Torr. The temperature at the top is 50.degree. C. The temperature at the sump is 83.degree. C. The product discharged from the sump is simultaneously cooled to 25.degree. to 30.degree. C and diluted with water or nitric acid having a concentration of 70%. After filtration 1-nitroanthraquinone is obtained in a purity of 90%.
In a vessel 20.80 kg/h of anthraquinone and 572.73 kg/h of nitric acid having a concentration of 88% are mixed at a temperature of 20.degree. C. The nitration reaction is continued in a reaction cascade having four stages with an average residence time of 3 hours at a temperature of 60.degree. to 65.degree. C. The reaction mixture discharged from the reaction cascade contains nitric acid having a concentration of 86.5% and in dissolved form a mixture consisting of 76% 1-nitro-anthraquinone, 10% 2-nitro-anthraquinone, 9% dinitroanthraquinones and 5% anthraquinone. The reaction mixture is introduced into a rectification column which contains 6 plates in the stripping section and 4 plates in the rectifying section. From the top of the rectification column 305.14 kg/h of nitric acid having a concentration of 99% are withdrawn. The reflux ratio is adjusted to 1:1. Out of the sump of the rectification column 263.04 kg/h of nitric acid and 25.38 kg/h organic components are withdrawn. In the sump of the rectification column the concentration of nitric acid is 72%. The column is operated at a pressure of 150 Torr at the top and at a temperature at the top of 42.degree. C. The temperature in the sump is 86.degree. C. 1-nitro-anthraquinone having a purity of 92% is obtained by cooling the product discharged from the sump to 20.degree. to 30.degree. C and filtration.
In a chamber reactor 20.80 kg/h of anthraquinone are continuously nitrated at 25.degree. C with 205.71 kg/h nitric acid having a concentration of 98 to 99%. The average residence time is 15 minutes. The product discharged from the reactor has a concentration of nitric acid of 95.6% and contains in dissolved form a mixture of 78.8% 1-nitro-anthraquinone, 7.8% 2-nitro-anthraquinone, 6.3% dinitroanthraquinones and 6.1% anthraquinone. The reaction mixture is introduced on the third plate of a rectification column having 5 plates. At the top of the column 141.77 kg/h nitric acid having a concentration of 99% is withdrawn. The reflux ratio is adjusted to 0.25:1. Into the sump of the column 114.13 kg/h of nitric acid having a concentration of 70% are introduced. From the sump of the rectification column 173.67 kg/h nitric acid having a concentration of 76% and 25.24 kg/h of dissolved solids are withdrawn. The column is operated at the same conditions as stated in Example 1. After cooling to 25.degree. to 30.degree. C and filtration 1-nitro-anthraquinone having a purity of 93 to 94% is obtained.