A Process for Revamping a Plant for the Production of Cyclohexanone

Abstract

A process for the construction of a second chemical plant, which second chemical plant is suitable for the separation of cyclohexanone from a second mixture, which second mixture comprises reaction products from the hydrogenation of phenol, said process comprising: a) providing a first chemical plant, which first chemical plant is suitable for the separation of cyclohexanone from a first mixture, which first mixture comprises reaction products from the oxidation of cyclohexane, and which first plant comprises: i) a distillation column (C) suitable for distilling overhead cyclohexane; ii) a distillation column suitable for distilling overhead cyclohexanone; iii) a cyclohexane oxidation unit (A) suitable for the oxidation of cyclohexane; and iv) a heat recovery unit (B) suitable for the recovery of heat from off-gas from the cyclohexane oxidation unit suitable for the oxidation of cyclohexane; b) disabling in said first chemical plant, said distillation column (C) suitable for distilling overhead cyclohexane, said cyclohexane oxidation unit (A) and said heat recovery unit (B), wherein the second chemical plant comprises a distillation column (F) suitable for distilling overhead cyclohexanone reused from the first chemical plant, wherein each of the first chemical plant and the second chemical plant comprise a distillation column (E) suitable for distilling overhead components having a lower boiling point than cyclohexanone; a distillation column (G) suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1; and a cyclohexanol dehydrogenation unit (H) suitable for the dehydrogenation of cyclohexanol to cyclohexanone.

Claims

1.-15. (canceled)

16. A process for the construction of a second chemical plant, which second chemical plant is suitable for the separation of cyclohexanone from a second mixture, which second mixture comprises reaction products from the hydrogenation of phenol, said process comprising: a) providing a first chemical plant, which first chemical plant is suitable for the separation of cyclohexanone from a first mixture, which first mixture comprises reaction products from the oxidation of cyclohexane, and which first plant comprises: i) a distillation column suitable for distilling overhead cyclohexane; ii) a distillation column suitable for distilling overhead cyclohexanone; iii) a distillation column suitable for distilling overhead components having a lower boiling point than cyclohexanone; iv) a distillation column suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone; v) a cyclohexane oxidation unit suitable for the oxidation of cyclohexane; and vi) a heat recovery unit suitable for the recovery of heat from off-gas from the cyclohexane oxidation unit suitable for the oxidation of cyclohexane; b) disabling i) said distillation column suitable for distilling overhead cyclohexane from said first chemical plant, v) said cyclohexanone oxidation unit and vi) said heat recovery unit, and wherein said second chemical plant comprises a distillation column suitable for distilling overhead cyclohexanone, wherein said cyclohexanone is part of a third mixture, which third mixture comprises said second mixture from which components having a lower boiling point than cyclohexanone have been removed; and c) adding to said first chemical plant a phenol hydrogenation unit.

17. The process according to claim 16, wherein the first mixture comprises cyclohexanol, cyclohexanone, cyclohexane and at least one compound selected from hexanal, pentanal, 2-heptanone, 3-heptanone, 4-heptanone, 1,3-cyclohexanedione and 1,4-cyclohexanedione.

18. The process according to claim 16, wherein the second mixture comprises cyclohexanol, cyclohexanone, phenol and at least one compound selected from 2-phenylcyclohexanol, 3-phenylcyclohexanol, 4-phenylcyclohexanol, cyclohexylphenylether, benzofuran, 2,3-dimethylbenzofuran, 3-methyl-4-octanone, 4-methyl-3-octanone, 3-methyl-3-octanone, methyl-isopropylcyclohexanol, methyl-isopropylcyclohexanone and 1-(4-methylpentane-2-yl)-benzene-phenol.

19. The process according to claim 16, wherein iv) is suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1.

20. The process according to claim 16, comprising adding to the first chemical plant a distillation column suitable for the recovery of phenol from the bottom product of a distillation column suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1.

21. The process according to claim 20, comprising adding to the first chemical plant a feed line from the distillation column suitable for the recovery of phenol from the bottom product of a distillation column suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1 to a phenol hydrogenation unit.

22. The process according to claim 21, wherein each of the first chemical plant and second chemical plant comprises: vii) a cyclohexanol dehydrogenation unit suitable for the dehydrogenation of cyclohexanol to cyclohexanone.

23. The process according to claim 16, wherein the capacity of the second chemical plant for separating cyclohexanone is at least 10% greater than the capacity of the first chemical plant for separating cyclohexanone, wherein capacity means the mass of cyclohexanone separated in a given time.

24. A chemical plant suitable for the separation of cyclohexanone from a second mixture, which second mixture comprises reaction products from the hydrogenation of phenol, which chemical plant comprises: a) a distillation column suitable for distilling overhead components having a lower boiling point than cyclohexanone; b) a distillation column suitable for distilling overhead cyclohexanone; c) a distillation column suitable for distilling overhead a mixture comprising cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1; d) a cyclohexanol dehydrogenation unit suitable for the dehydrogenation of cyclohexanol to form a mixture comprising cyclohexanol and cyclohexanone; e) a feed line suitable for recycling said mixture comprising cyclohexanol and cyclohexanone formed in d) from d) to a); and f) a phenol hydrogenation unit that produces a mixture comprising reaction products from the hydrogenation of phenol; characterised in that at least one of a) and d) have been used in a chemical plant for the separation of cyclohexanone from a first mixture, which first mixture comprises reaction products from the oxidation of cyclohexane; and wherein at least one of c) and d) has a capacity greater than that necessary for the separation of cyclohexanone from the second mixture, based on the chemical plant operating at full capacity of a) and b), wherein capacity of the plant or distillation column means the mass of cyclohexanone separated in a given time, and wherein capacity of the cyclohexanol dehydrogenation unit means the weight of cyclohexanol that is converted into cyclohexanone unit per unit time.

25. The chemical plant according to claim 24, wherein at least one of c) and d) has a capacity of at least 10% greater than that necessary for the separation of cyclohexanone from the second mixture, based on the chemical plant operating at full capacity of a) and b).

26. A process for the separation of cyclohexanone from a second mixture, which second mixture comprises reaction products from the hydrogenation of phenol, said process comprising: a) distilling overhead in a distillation column components having a lower boiling point than cyclohexanone; b) distilling overhead in a distillation column cyclohexanone; c) distilling overhead in a distillation column a mixture of cyclohexanol and cyclohexanone in a wt.:wt. ratio of at least 4:1; d) dehydrogenating in a cyclohexanol dehydrogenation unit cyclohexanol distilled overhead in c) to form a mixture comprising cyclohexanol and cyclohexanone; e) recycling the mixture comprising cyclohexanol and cyclohexanone formed in d) from d) to a); and f) hydrogenating phenol in a phenol hydrogenation until that produces a mixture comprising reaction products from the hydrogenation of phenol; characterised in that at least one of the distillation column of a) and the cyclohexanol dehydrogenation unit of d) have been used in a chemical plant for the separation of cyclohexanone from a first mixture, which first mixture comprises reaction products from the oxidation of cyclohexane; and wherein at least one of c) and d) is carried out at a rate below the capacity of, respectively, the distillation column of c) and the cyclohexanol dehydrogenation unit of d), wherein capacity of the plant or distillation column means the mass of cyclohexanone separated in a given time, and wherein capacity of the cyclohexanol dehydrogenation unit means the weight of cyclohexanol that is converted into cyclohexanone unit per unit time.

27. The process according to claim 26, wherein at least one of c) and d) is carried out at a rate of at most 90% of the capacity of, respectively, the distillation column of c) and the cyclohexanol dehydrogenation unit of d).

Description

EXAMPLE 1

[0119] A chemical plant for the production of cyclohexanone by hydrogenation of phenol, comprising: [0120] a phenol hydrogenation unit; [0121] a lights distillation column; [0122] a cyclohexanone distillation column; [0123] a cyclohexanol distillation column; [0124] a phenol distillation column; and [0125] a cyclohexanol dehydrogenation unit;
as described before and substantially as depicted in FIG. 2 was simulated in Aspen Plus® chemical engineering software with input data obtained from an operating chemical plant as described herein. The simulated plant was designed with an identical cyclohexanone distillation column and an identical cyclohexanol dehydrogenation unit as in Comparative Example A. The cyclohexanone distillation column limited the overall capacity of the plant.

[0126] The hydrogenation of phenol in the phenol hydrogenation unit was performed in the gas phase in the presence of a palladium-comprising catalyst. The resulting gas mixture, comprising phenol, hydrogen gas, cyclohexanol and cyclohexanone, was partially condensed by cooling and separated into a liquid mixture comprising phenol, cyclohexanol and cyclohexanone that was fed to the lights distillation column, and a gaseous flow comprising hydrogen.

[0127] In the lights distillation column, components with boiling points lower than that of cyclohexanone were distilled overhead. The bottom flow from the lights distillation column was fed to the cyclohexanone distillation column, where essentially pure cyclohexanone was distilled overhead. The bottom flow from the cyclohexanone distillation column was fed to the cyclohexanol distillation column, where a mixture comprising mainly cyclohexanol was distilled overhead. This mixture comprising mainly cyclohexanol was fed to the cyclohexanol dehydrogenation unit, in which cyclohexanol was converted into cyclohexanone. Hydrogen gas formed was separated therefrom. The resulting reaction mixture was then fed to the lights distillation column.

[0128] The bottom flow of the cyclohexanol distillation column was fed to a phenol distillation column where heavies were separated from a mixture comprising mainly cyclohexanol and phenol.

[0129] The pressure at the top of the cyclohexanone distillation column was identical to the pressure in Comparative Experiment A. The cyclohexanol concentration in the cyclohexanone that was distilled overhead in the cyclohexanone distillation column was on average about 250 ppm by weight, which is equal to that in Comparative Experiment A.

[0130] The cyclohexanol dehydrogenation unit was identical to the cyclohexanol dehydrogenation unit in Comparative Experiment A.

[0131] The feed rate to the cyclohexanone distillation column was about 16.9 ton/hr. The weight ratio of cyclohexanone to cyclohexanol in the feed was almost 11. The reflux rate is about 27.2 ton/hr. The hourly capacity of this column was about 15.0 metric tons of essentially pure cyclohexanone, which is equivalent to an annual plant capacity of approximately 120 kta of essentially pure cyclohexanone.

[0132] The flow rate from the bottom of the cyclohexanone distillation column was about 1.9 ton/hr and the flow consisted of mainly cyclohexanol and phenol, and about 6% by weight of cyclohexanone. This bottom flow was fed to the cyclohexanol distillation column where mainly cyclohexanol was distilled overhead. The top flow of this cyclohexanol distillation column was fed to a cyclohexanol dehydrogenation unit. The weight ratio of cyclohexanone to cyclohexanol in the outlet of the cyclohexanol dehydrogenation unit was about 6 to 4. The outlet flow of the cyclohexanol dehydrogenation unit was, after hydrogen gas had been separated off, fed to the lights distillation column. The cyclohexanol dehydrogenation unit was operated at approximately 15% of its capacity.

[0133] Comparison of Comparative Experiment A and Example 1 shows that the vacuum distillation column where essentially pure cyclohexanone was distilled overhead (with auxiliaries including reboiler and condenser unit) used in the production of cyclohexanone from reaction products of the oxidation of cyclohexane, can be re-used for the production of cyclohexanone from reaction products of the hydrogenation of phenol. The annual capacity is increased from approximately 100 kta of essentially pure cyclohexanone to approximately 120 kta of essentially pure cyclohexanone, so by about 20%.

[0134] In addition, this comparison shows that a cyclohexanol dehydrogenation unit used in a process for the production of cyclohexanone by oxidation of cyclohexane whereby the oxidation of cyclohexane is performed without addition of any catalyst, can be re-used in a process for the production of cyclohexanone by hydrogenation of phenol. In this case, the simulation showed that the cyclohexanol dehydrogenation unit had a huge over-capacity. In practice the capacity of the cyclohexanol dehydrogenation unit could be easily reduced by, for example, blinding off a large fraction of the pipes in case the cyclohexanol dehydrogenation unit comprises a multi-tubular heated reactor.

EXAMPLE 2

[0135] A chemical plant for the production of cyclohexanone by hydrogenation of phenol, comprising: [0136] a phenol hydrogenation unit; [0137] a lights distillation column; [0138] a cyclohexanone distillation column; [0139] a cyclohexanol distillation column; [0140] a phenol distillation column; and [0141] a cyclohexanol dehydrogenation unit;
as described before and substantially as depicted in FIG. 2 was simulated in Aspen Plus® chemical engineering software with input data obtained from an operating chemical plant as described herein. The simulated plant was designed with an identical cyclohexanone distillation column and an identical cyclohexanol dehydrogenation unit as in Comparative Example B. The cyclohexanone distillation column limited the overall capacity of the plant.

[0142] The cyclohexanone plant simulated was identical to that of Example 1, except that it included an additional buffer vessel upstream and an additional buffer vessel downstream of the cyclohexanol dehydrogenation unit.

[0143] The process was also identical to that of Example 1, except that:

[0144] i) the hydrogenation of phenol in the phenol hydrogenation unit was performed in the liquid phase with a palladium-comprising catalyst; and

[0145] ii) the resulting reaction mixture that comprised phenol, cyclohexanol and cyclohexanone had a similar composition to that of Example 1.

[0146] The top flow of the cyclohexanol distillation column was fed to the buffer tank located upstream of the cyclohexanol dehydrogenation unit. The cyclohexanol dehydrogenation unit was fed from this buffer tank. The cyclohexanol dehydrogenation unit was only operated in a discontinuous manner. It was started when the buffer tank located upstream of the cyclohexanol dehydrogenation unit became about 80% full and was stopped when this tank became less than about 15% full. The weight ratio of cyclohexanone to cyclohexanol in the outlet of the cyclohexanol dehydrogenation unit is about 6 to 4. The outlet flow of the cyclohexanol dehydrogenation unit was, after hydrogen gas had been separated off, fed to the buffer tank located downstream of the cyclohexanol dehydrogenation unit. From this tank a mixture comprising cyclohexanol and cyclohexanone was fed to the lights distillation column in a continuous manner.

[0147] The hourly capacity of the cyclohexanone plant was about 15.0 metric tons of essentially pure cyclohexanone, which is equivalent to an annual plant capacity of approximately 120 kta of essentially pure cyclohexanone.

[0148] Comparison of Comparative Experiment B and Example 2 shows that the vacuum distillation column where essentially pure cyclohexanone is distilled overhead (with auxiliaries including reboiler and condenser unit) used in the production of cyclohexanone from reaction products of the oxidation of cyclohexane, can be re-used for the production of cyclohexanone from reaction products of the hydrogenation of phenol. The annual capacity is increased from approximately 96 kta of essentially pure cyclohexanone to approximately 120 kta of essentially pure cyclohexanone, so by about 25%.

[0149] In addition this comparison shows that the cyclohexanol dehydrogenation unit used in a process for the production of cyclohexanone by oxidation of cyclohexane whereby the oxidation of cyclohexane is performed with addition of catalyst, can be re-used in a process for the production of cyclohexanone by hydrogenation of phenol by operating the cyclohexanol dehydrogenation unit in a discontinuous mode after addition of just two simple buffer tanks.