US20090032389A1 - Process for the mild distillative separation of mixtures - Google Patents
Process for the mild distillative separation of mixtures Download PDFInfo
- Publication number
- US20090032389A1 US20090032389A1 US12/206,898 US20689808A US2009032389A1 US 20090032389 A1 US20090032389 A1 US 20090032389A1 US 20689808 A US20689808 A US 20689808A US 2009032389 A1 US2009032389 A1 US 2009032389A1
- Authority
- US
- United States
- Prior art keywords
- column
- process according
- fraction
- feed
- container
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
- B01D3/322—Reboiler specifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S203/00—Distillation: processes, separatory
- Y10S203/07—Start up or shut down
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S203/00—Distillation: processes, separatory
- Y10S203/13—Spirits
Definitions
- the invention relates to a semibatchwise process for the mild distillative separation of mixtures.
- a distillation bulb In batchwise separation processes, which are frequently used for the separation of two, in particular more than two components, a distillation bulb is first filled with the mixture to be separated and heated to the boiling point. The fractions can then be taken off in ascending order of their boiling point via the top of the column, with the bottom temperature simultaneously increasing.
- This procedure proves to be disadvantageous particularly when, because of its boiling point, a component is not taken off as the first fraction and tends to undergo secondary reaction, such as, for example, decomposition, under prolonged thermal load.
- German Offenlegungsschrift 42 26 905 describes a batchwise distillation, with a part-fraction being taken off in a side stream and being recycled into the columns later on. In this way, the specific energy demand is slightly reduced.
- a disadvantage thereof is that the process control is substantially more complicated and an additional container is required for intermediate storage.
- the bottom container is initially filled and higher-boiling components are subjected to thermal load during the entire distillation time in the boiling liquid bottom product.
- EP-A 638 345 describes a column having a container at the bottom and at the top, which can be used as a rectification or stripping section depending on the desired procedure. For mixtures whose medium boiler fraction accounts for a proportion of at least 70% by weight, the distillation time can be reduced by this procedure. However, this process requires complicated apparatus and cannot generally be used.
- Baichun and Zhicai (Huagong Gongcheng, 22, 1994, pages 30-34) describe the separation of a multicomponent system in a column having two containers.
- a complete non-steady-state process of a batchwise mode of operation is divided into n-1 continuous steps in order to separate the mixture having n fractions.
- a container is required as a feed container and a second one is required in order to receive the bottom discharge.
- This procedure permits the simultaneous use of the column as a stripping and rectification section and hence an acceptable specific energy consumption.
- an additional container is required for this process too.
- Maczynski and Maczynska propose, for the separation of a binary mixture, a process which combines the advantages of the continuous procedure and the batchwise procedure.
- a first step the column at whose lower end a distillation bulb is present is supplied with a continuous feed and the first fraction is taken off via the top of the column. The bottom discharge is used for filling the distillation bulb.
- the content of the distillation bulb must be kept at the boiling point, and the thermal loading of the higher-boiling components is therefore very high.
- the invention also relates to a process in which the steps a) and b) are repeated once or several times.
- continuously includes changes of the amount of feed as a function of time as well as temporary interruptions of the feed, as are realized, for example, in the case of an intermittent or stepped feed or a feed changing over a predetermined ramp.
- FIG. 1 is a schematic of the process of separating mixtures, representing: feeding the mixture into the column and separating it fractions, removing the respective fraction into a container and recycling the fraction removed after stopping the feed, and in the alternative recycling the middle and highest boiling fractions.
- FIG. 2 is a schematic of a distillation apparatus for separating mixtures in accordance with the invention.
- the feed point is preferably chosen so that the column has a stripping section and a rectification section.
- the columns used may be the columns known to a person skilled in the art. For example, these are packed columns containing dumped packings or stacked packings or tray columns. If it is intended to take off side stream fractions (medium boiler fractions), the column may also be designed as a dividing wall column or thermally coupled column.
- packings may be used in the rectification section and trays in the stripping section.
- packed columns containing dumped packings or stacked packings and corresponding tray constructions in tray columns are suitable for minimizing the hold-up and pressure drop for mild thermal separation.
- the number of theoretical plates in the column may be, for example, from 2 to 150, preferably from 4 to 70, particularly preferably from 6 to 60.
- a part of the mixture to be separated or a fraction thereof which may originate, for example, from a prior separation can be used for starting up the column before step a).
- the bottom of the column is filled with just sufficient liquid to enable the evaporator to be put into operation.
- high boilers and “high boiler fractions” are to be understood as meaning substances or mixtures which have a higher boiling point than the optionally present medium boilers and medium boiler fractions, which in turn have a higher boiling point than the low boilers and low boiler fractions.
- the terms in each case relate to a partial step and may have a different meaning for step a) and step b) for an individual substance.
- a high boiler from step a) may be a low boiler in step b).
- the feed is separated at least into a low boiler fraction and a high boiler fraction and optionally a medium boiler fraction, one of the fractions being removed continuously into a container.
- step a at least one low boiler fraction is removed via the top column and at least one high boiler fraction via the bottom of the column.
- a low boiler fraction is removed via the top of the column (also referred to as top fraction), a medium boiler fraction via a side stream (also referred to as side stream fraction) and a high boiler fraction via the bottom of the column (also referred to as bottom fraction).
- step a it is also possible to obtain medium boiler fractions which meet very high purity requirements without intermediate steps.
- a low boiler fraction is taken off via the top of the column and a high boiler fraction via the bottom of the column.
- Either a top fraction, optionally a medium boiler fraction or a bottom fraction can be transferred into the container, preferably the top fraction or the bottom fraction.
- the fraction whose purity requirements are not met in the continuous step is removed into the container.
- the removal into the container is effected continuously, the term continuously being defined as above.
- the fraction which is removed into the container can remain at a temperature which, based on the pressure in the bottom of the column, is below its boiling point, and is therefore subjected to considerably less thermal load, for example in comparison with the batchwise distillation.
- the removal and the residence in the container are preferably effected without additional heat supply or with cooling.
- the residence temperature can be chosen according to the product properties.
- step a) the control is effected via suitable temperature measurements in the rectification and/or stripping section, depending on the desired target purity of the top or bottom product.
- step a) is terminated by stopping the feed and in step b) the content of the container is fed to the column.
- the column can be operated either by the descending, ascending or simultaneously descending and ascending procedure.
- the freedom of arrangement in step b) means that the column is not connected directly to the boiler but preferably via a pipeline with a liquid seal, for example also with a shut-off means.
- the container In the descending procedure, the container is connected to the condensate discharge and the container discharge passes as a reflux to the top of the column. The fractions are taken off as high boiler fractions at the bottom, until finally the last low boiler fraction remains in the container in the desired purity.
- step b) the mixture is preferably separated batchwise by the ascending procedure.
- the container is then integrated into the bottom circulation, the liquid from the bottom being recycled via the container and the evaporator into the column.
- One or more low boiler fractions can be taken off via the top until the last high boiler fraction of the desired purity is in the container. It may also be the distillation residue.
- step b) The simultaneous ascending and descending procedure in step b) can be realized by connection of the container in the middle of the column. Low boiler fractions are taken off at the top and also high boiler fractions at the bottom. This embodiment of step b) is then advantageously completed when a medium boiler fraction—or alternatively an intermediate cut - remains in the desired purity/composition in the container.
- the batch distillation with a middle container is described, for example, in M. Warter et al., Comp. Chem. Eng. Suppl. (1999), page 915-page 918.
- the evaporation can be effected from the container.
- the container can be operated at a temperature below the boiling point, for the mild treatment of the feedstocks.
- Evaporators which may be used are all evaporator types which are known to a person skilled in the art, require a small temperature increase and permit evaporation from thin films. Falling-film evaporators or thin-film evaporators are preferably used.
- one or more preheaters can be connected upstream of the evaporator.
- the invention also relates to a process in which the steps a) and b), in each case independently of one another, are repeated once or several times.
- the process according to the invention is particularly suitable for the separation of multicomponent mixtures.
- multicomponent mixtures are reaction mixtures or solvent mixtures.
- the column 2 is fed continuously with a mixture which is to be separated and comprises the components A (lowest boiling point), B (middle boiling point) and C (highest boiling point) via a feed valve V 1 and the feed 1 , which is located either in the upper (i), in the middle (ii) or in the lower part of the column.
- a feed valve V 1 and the feed 1 which is located either in the upper (i), in the middle (ii) or in the lower part of the column.
- Component A is taken off via the top 5 of the column and the components B and C are at least partly removed via the bottom 6 of the column and via the lines 7 and 9 and the valve (V 2 ) connected in between and the heat exchanger 9 into a container 10 .
- the feed valve V 1 is closed.
- the low boiler of the mixture B is taken off in the desired purity via the line 19 into a collecting apparatus 20 .
- the high boiler C is concentrated in the bottom.
- the step is complete when C has reached the desired target purity.
- the components B and C can also be recycled via feed 1 to the column 2 , component B via the top 5 of the column and component C via the bottom 6 of the column, but then into a separate product container.
- the invention also relates to a process in which steps a) and b), in each case independently of one another, are repeated once or several times.
- the process according to the invention is particularly suitable for the separation of multicomponent mixtures.
- multicomponent mixtures are reaction mixtures or solvent mixtures.
- the invention furthermore relates to a distillation apparatus consisting at least of a column 2 from whose upper part 5 a discharge line 17 leads via a heat exchanger 18 and a line 19 to a valve V 4 , the line 19 being connected to the column, and furthermore leads to at least one collecting apparatus 20 , a feed 1 which is controllable via a feed valve V 1 and enters the column, and a thermostatable container 10 which is spatially separated from the column and is connected to the column via the lines 7 and 9 , which is characterized in that the line 7 leads to a valve V 2 which is connected via the line 9 , which optionally leads via a heat exchanger 8 , to the container 10 and via the line 11 to the valve V 3 , the valve V 3 being connected via the line 12 to the container and via the line 13 to the column, and the line 13 furthermore containing a pump 14 , optionally a preheater 15 and optionally an evaporator 16 , and furthermore the line 19 mounted at the upper end of the column 2 contains a
- the present invention is distinguished by the fact that the entire process can be carried out using apparatus which is not very complicated.
- mixtures comprising thermally sensitive fractions can be separated under mild conditions with very good space-time yields.
- the column 2 was in the form of a column containing stacked packing and was heated by means of a falling-film evaporator 15 .
- the column 2 is heated with bottom product from the last batch or phenol-free phenoxyethanol, which is initially introduced into the container 10 , via the falling-film evaporator 15 and is initially operated with total reflux.
- the amount of product used for this purpose is only a fraction of the container volume and is chosen so that the column 2 can just be started up therewith.
- the column was fed continuously with a gradually increasing and finally constant stream of the reaction mixture described above.
- the feed point was chosen so that the column 2 had both a stripping section and a rectification section (ii).
- a temperature of 130° C. was established at the top of the column 5 and a temperature of 155° C. at the bottom.
- the pressure at the top of the column was kept at from 30 to 40 mbar.
- a forerun whose phenol content is checked, is taken off via the top of the column.
- the bottom discharge of bottom 6 of the column is passed into the container 10 .
- the feed was stopped by changing over feed valve V 1 and step b) was immediately started and a further forerun taken off.
- the phenol content in the forerun decreased, and changeover to the main fraction was effected on falling below a certain phenol content dependent on the quality requirements for the main fraction.
- the main fraction was taken off until a temperature of 157° C. was reached at the bottom of the column, and changeover to total reflux was then effected.
- the apparatus was then ready for receiving the next batch. After six batches, the bottom product collected in the distillation bulb was discharged after a fraction containing phenoxyethanol and higher homologs have been separated off in last runnings by rectification.
- step a) the column 2 was fed continuously with a reaction mixture from the nitration of ethylbenzene, which reaction mixture substantially contains ortho- and para-nitroethylbenzene (O-NEB and p-NEB, respectively) and about 7% of meta-nitroethylbenzene (m-NEB) and 0.5% of dinitroethylbenzene (di-NEB).
- the mixture freed from di-NEB and comprising o-NEB, p-NEB and m-NEB was taken off via the top 5 of the column and removed into the container 10 .
- a fraction which contained about 10% by mass of di-NEB was taken off via the bottom 6 of the column.
- step b) the column 2 was fed from the container 10 with the mixture obtained in step a) and comprising o-NEB, p-NEB and m-NEB.
- the fractions forerun, o-NEB, intermediate cut I and intermediate cut II were taken off in succession via the top 5 of the column. Since di-NEB and other high boilers had already been removed in step a), pure p-NEB was present in the bottom. Optionally distillation of last runnings with take-off of pure p-NEB via the top follows.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention relates to a semibatchwise process for the mild distillative separation of mixtures, in a first stage a column being supplied continuously with a feed and the feed being separated at least into different fractions, one of the fractions being removed continuously into a container, and, in a second step, the fraction removed into the container being recycled to the column and being separated again batchwise into different fractions.
Description
- This application is a continuation of U.S. patent application Ser. No. 10/435,886 filed May 12, 2003, incorporated herein by reference.
- 1. Field of the Invention
- The invention relates to a semibatchwise process for the mild distillative separation of mixtures.
- 2. Brief Description of the Prior Art
- Continuous separation processes using a column and batchwise separation processes by means of a distillation bulb with attached column are known. Said processes are described in the form of a synopsis, for example in “Thermische Trennverfahren” [Thermal separation processes] (K. Sattler, 2001 edition, VCH Verlagsgesellschaft, Weinheim).
- In batchwise separation processes, which are frequently used for the separation of two, in particular more than two components, a distillation bulb is first filled with the mixture to be separated and heated to the boiling point. The fractions can then be taken off in ascending order of their boiling point via the top of the column, with the bottom temperature simultaneously increasing. This procedure proves to be disadvantageous particularly when, because of its boiling point, a component is not taken off as the first fraction and tends to undergo secondary reaction, such as, for example, decomposition, under prolonged thermal load.
- In the case of demanding requirements with respect to the purity of these higher-boiling components, it is possible to take off intermediate cuts of lower purity. These are then added to the feed, for example in the next separation. Consequently, a part of the feed is circulated, with the result that the space-time yields decrease considerably. A further disadvantage of the batchwise procedure is the substantially higher specific energy demand in comparison with the continuous procedure (cf. Kaibel, Krug, Chemie Ingenieur Technik [Chemical Engineering] 70, 1998, pages 711-713).
- German Offenlegungsschrift 42 26 905 describes a batchwise distillation, with a part-fraction being taken off in a side stream and being recycled into the columns later on. In this way, the specific energy demand is slightly reduced. However, a disadvantage thereof is that the process control is substantially more complicated and an additional container is required for intermediate storage. Furthermore, in this process, the bottom container is initially filled and higher-boiling components are subjected to thermal load during the entire distillation time in the boiling liquid bottom product.
- EP-A 638 345 describes a column having a container at the bottom and at the top, which can be used as a rectification or stripping section depending on the desired procedure. For mixtures whose medium boiler fraction accounts for a proportion of at least 70% by weight, the distillation time can be reduced by this procedure. However, this process requires complicated apparatus and cannot generally be used.
- Baichun and Zhicai (Huagong Gongcheng, 22, 1994, pages 30-34) describe the separation of a multicomponent system in a column having two containers. A complete non-steady-state process of a batchwise mode of operation is divided into n-1 continuous steps in order to separate the mixture having n fractions. A container is required as a feed container and a second one is required in order to receive the bottom discharge. This procedure permits the simultaneous use of the column as a stripping and rectification section and hence an acceptable specific energy consumption. However, an additional container is required for this process too.
- Maczynski and Maczynska (Przemysl Chemiczny 49, 1970, pages 599-601) propose, for the separation of a binary mixture, a process which combines the advantages of the continuous procedure and the batchwise procedure. In a first step, the column at whose lower end a distillation bulb is present is supplied with a continuous feed and the first fraction is taken off via the top of the column. The bottom discharge is used for filling the distillation bulb. In this process too, the content of the distillation bulb must be kept at the boiling point, and the thermal loading of the higher-boiling components is therefore very high.
- There is therefore the need to provide a process for the distillative separation of mixtures which has an advantageous specific energy demand, keeps the complexity of the apparatus manageable and keeps the thermal loading of sensitive components small. Furthermore, an improvement for mixtures of any desired composition should be achievable.
- A process for the distillative separation of mixtures has now been found which is characterized in that
-
- a) a column is continuously supplied with a feed and the feed is separated at least into a low boiler fraction and a high boiler fraction and optionally a medium boiler fraction, one of the fractions being removed continuously into a container, and
- b) after stopping of the continuous feed, the fraction removed in step a) into the container is recycled to the column and is separated again batchwise, in any desired arrangement of boiler and column, at least into a low boiler fraction and a high boiler fraction and optionally a medium boiler fraction.
- The invention also relates to a process in which the steps a) and b) are repeated once or several times.
- The term “continuously” includes changes of the amount of feed as a function of time as well as temporary interruptions of the feed, as are realized, for example, in the case of an intermittent or stepped feed or a feed changing over a predetermined ramp.
- It should be pointed out that the scope of the invention, as more fullydescribed hereunder, also comprises any desired combinations of features and preferred ranges thereof.
-
FIG. 1 is a schematic of the process of separating mixtures, representing: feeding the mixture into the column and separating it fractions, removing the respective fraction into a container and recycling the fraction removed after stopping the feed, and in the alternative recycling the middle and highest boiling fractions. -
FIG. 2 is a schematic of a distillation apparatus for separating mixtures in accordance with the invention. - According to the separation problem and depending on the position of the feed point, the column serves either as a stripping column (
FIG. 1 , feed i), i.e. all theoretical plates are below the feed point (nA=n), as a rectification column (FIG. 1 , feed iii), i.e. all theoretical plates are above the feed point (nA=0), or as a column having a stripping section and rectification section (FIG. 1 , feed ii), i.e. nA theoretical plates are below and n-nA theoretical plates are above the feed point, n being the total number of theoretical plates of the column. - The feed point is preferably chosen so that the column has a stripping section and a rectification section.
- The columns used may be the columns known to a person skilled in the art. For example, these are packed columns containing dumped packings or stacked packings or tray columns. If it is intended to take off side stream fractions (medium boiler fractions), the column may also be designed as a dividing wall column or thermally coupled column.
- Furthermore, it is also possible to equip the column both with trays and with packing elements. For example, packings may be used in the rectification section and trays in the stripping section.
- Preferably, packed columns containing dumped packings or stacked packings and corresponding tray constructions in tray columns are suitable for minimizing the hold-up and pressure drop for mild thermal separation.
- The trays, dumped packings and stacked packings which can be used for the process according to the invention are described, for example, in Henry Kister, Distillation Design, McGrawHill, 1992, K. Sattler, Thermische Trenntechnik [Thermal Separation Technology], Verlag VCH, 2001.
- The number of theoretical plates in the column may be, for example, from 2 to 150, preferably from 4 to 70, particularly preferably from 6 to 60.
- For example, a part of the mixture to be separated or a fraction thereof which may originate, for example, from a prior separation can be used for starting up the column before step a). In a preferred embodiment, the bottom of the column is filled with just sufficient liquid to enable the evaporator to be put into operation.
- Furthermore, it is preferable to start up the column with a high boiler fraction of the mixture to be separated, in order to keep the content of low boilers in the bottom of the column as low as possible from the outset.
- The terms “high boilers” and “high boiler fractions” are to be understood as meaning substances or mixtures which have a higher boiling point than the optionally present medium boilers and medium boiler fractions, which in turn have a higher boiling point than the low boilers and low boiler fractions. The terms in each case relate to a partial step and may have a different meaning for step a) and step b) for an individual substance. Thus, for example, a high boiler from step a) may be a low boiler in step b).
- In the distillative separation of the feed, the feed is separated at least into a low boiler fraction and a high boiler fraction and optionally a medium boiler fraction, one of the fractions being removed continuously into a container.
- Preferably, in step a), at least one low boiler fraction is removed via the top column and at least one high boiler fraction via the bottom of the column.
- Furthermore preferably, in step a), a low boiler fraction is removed via the top of the column (also referred to as top fraction), a medium boiler fraction via a side stream (also referred to as side stream fraction) and a high boiler fraction via the bottom of the column (also referred to as bottom fraction).
- Particularly when the column is used as a rectification and stripping section during step a), it is also possible to obtain medium boiler fractions which meet very high purity requirements without intermediate steps. Particularly preferably, in step a), a low boiler fraction is taken off via the top of the column and a high boiler fraction via the bottom of the column.
- Either a top fraction, optionally a medium boiler fraction or a bottom fraction can be transferred into the container, preferably the top fraction or the bottom fraction.
- Preferably, the fraction whose purity requirements are not met in the continuous step is removed into the container.
- The removal into the container is effected continuously, the term continuously being defined as above.
- In the case of thermally sensitive products, the fraction which is removed into the container can remain at a temperature which, based on the pressure in the bottom of the column, is below its boiling point, and is therefore subjected to considerably less thermal load, for example in comparison with the batchwise distillation.
- The removal and the residence in the container are preferably effected without additional heat supply or with cooling. The residence temperature can be chosen according to the product properties.
- All customary control concepts and control concepts mentioned, for example, by Kister, Sattler and Stichlmair (Distillation—Principles and Practice, Wiley VCH, 1998) for the continuous and batchwise columns can be used for automating the process according to the invention. In a preferred embodiment of the process according to the invention, in step a) the control is effected via suitable temperature measurements in the rectification and/or stripping section, depending on the desired target purity of the top or bottom product.
- Once the container is at least partly full, step a) is terminated by stopping the feed and in step b) the content of the container is fed to the column. In step b), the column can be operated either by the descending, ascending or simultaneously descending and ascending procedure. The freedom of arrangement in step b) means that the column is not connected directly to the boiler but preferably via a pipeline with a liquid seal, for example also with a shut-off means.
- In the descending procedure, the container is connected to the condensate discharge and the container discharge passes as a reflux to the top of the column. The fractions are taken off as high boiler fractions at the bottom, until finally the last low boiler fraction remains in the container in the desired purity.
- In step b), the mixture is preferably separated batchwise by the ascending procedure. The container is then integrated into the bottom circulation, the liquid from the bottom being recycled via the container and the evaporator into the column. One or more low boiler fractions can be taken off via the top until the last high boiler fraction of the desired purity is in the container. It may also be the distillation residue.
- The simultaneous ascending and descending procedure in step b) can be realized by connection of the container in the middle of the column. Low boiler fractions are taken off at the top and also high boiler fractions at the bottom. This embodiment of step b) is then advantageously completed when a medium boiler fraction—or alternatively an intermediate cut - remains in the desired purity/composition in the container. The batch distillation with a middle container is described, for example, in M. Warter et al., Comp. Chem. Eng. Suppl. (1999), page 915-page 918.
- For steps a) and b), heating with live steam is also possible. In the ascending procedure, the evaporation can be effected from the container. In the preferred case, however, the container can be operated at a temperature below the boiling point, for the mild treatment of the feedstocks. For the process according to the invention, it is therefore preferable to use an evaporator. Evaporators which may be used are all evaporator types which are known to a person skilled in the art, require a small temperature increase and permit evaporation from thin films. Falling-film evaporators or thin-film evaporators are preferably used. Optionally, one or more preheaters can be connected upstream of the evaporator.
- The invention also relates to a process in which the steps a) and b), in each case independently of one another, are repeated once or several times.
- The process according to the invention is particularly suitable for the separation of multicomponent mixtures. Examples of multicomponent mixtures are reaction mixtures or solvent mixtures.
- The process according to the invention is further described by way of the following non-limiting example with reference to
FIGS. 1 and 2 : - The
column 2 is fed continuously with a mixture which is to be separated and comprises the components A (lowest boiling point), B (middle boiling point) and C (highest boiling point) via a feed valve V1 and thefeed 1, which is located either in the upper (i), in the middle (ii) or in the lower part of the column. When thecolumn 2 is fed via the middle part (ii), as shown inFIG. 2 , thecolumn 2 is consequently divided for step a) into a strippingsection 4 and arectification section 3. Component A is taken off via thetop 5 of the column and the components B and C are at least partly removed via thebottom 6 of the column and via thelines heat exchanger 9 into acontainer 10. When a predetermined level is reached incontainer 10, the feed valve V1 is closed. Thecontainer 10 is now connected to the bottom circulation (bottom 6 of the column =>lines container 10=>line 13, pump 14,preheater 15,evaporator 16=> andbottom 6 of the column). At thetop 5 of the column, the low boiler of the mixture B is taken off in the desired purity via theline 19 into a collectingapparatus 20. The high boiler C is concentrated in the bottom. The step is complete when C has reached the desired target purity. Alternatively, the components B and C can also be recycled viafeed 1 to thecolumn 2, component B via thetop 5 of the column and component C via thebottom 6 of the column, but then into a separate product container. - The invention also relates to a process in which steps a) and b), in each case independently of one another, are repeated once or several times.
- The process according to the invention is particularly suitable for the separation of multicomponent mixtures. Examples of multicomponent mixtures are reaction mixtures or solvent mixtures.
- The invention furthermore relates to a distillation apparatus consisting at least of a
column 2 from whose upper part 5 adischarge line 17 leads via aheat exchanger 18 and aline 19 to a valve V4, theline 19 being connected to the column, and furthermore leads to at least one collectingapparatus 20, afeed 1 which is controllable via a feed valve V1 and enters the column, and athermostatable container 10 which is spatially separated from the column and is connected to the column via thelines line 7 leads to a valve V2 which is connected via theline 9, which optionally leads via a heat exchanger 8, to thecontainer 10 and via theline 11 to the valve V3, the valve V3 being connected via theline 12 to the container and via theline 13 to the column, and theline 13 furthermore containing apump 14, optionally apreheater 15 and optionally anevaporator 16, and furthermore theline 19 mounted at the upper end of thecolumn 2 contains a valve V4 which connects thecolumn 2 via theline 19 and the line 21 to thecontainer 10. - The present invention is distinguished by the fact that the entire process can be carried out using apparatus which is not very complicated. In particular mixtures comprising thermally sensitive fractions can be separated under mild conditions with very good space-time yields.
- A mixture consisting of:
- 100 kg of n-hexane
- 700 kg of n-heptane
- 200 kg of n-octane
- was separated without an intermediate cut, the purity in each case being at least 99.0%.
- For this purpose, a column having twenty theoretical plates were used under the following conditions:
-
- Top pressure PTop=1 bar
- Pressure drop Δp=1 mbar/plate
- Energy supply (Q)=constant 50 kW
- The separation was carried out batchwise from a distillation bulb with attached column (I) and according to the invention (II). Comparisons were based on simulation calculations, but on the basis of a measured material system and with a validated column model.
- The following procedure was adopted and the times in brackets determined:
- (I) Not according to the invention (cf. EP-A 638 345):
-
- Initially introduced mixture in the boiler
- Distillation of n-hexane via the top of the column (350 min)
- Distillation of n-heptane (150 min) as second fraction via the top of the column
- n-Octane remained as a bottom residue.
- Total distillation time: 500 min.
- (II) According to the invention:
-
- Step a): continuous feeding of the column with the mixture and take-off of n-hexane as a top product with simultaneous filling of the container with n-heptane/n-octane (150 min), followed by feeding of the column from the container and separation of n-heptane (150 min) via the top of the column, n-octane remaining as a bottom residue. Total distillation time: 300 min
- The reaction of phenol and ethylene oxide gives a mixture which contains 94% of phenoxyethanol. The remaining 6% substantially comprise high boilers and unconverted phenol. This mixture was worked up according to the invention as follows (substantially corresponds to the exemplary explanations for
FIGS. 1 and 2 ). - The
column 2 was in the form of a column containing stacked packing and was heated by means of a falling-film evaporator 15. Thecolumn 2 is heated with bottom product from the last batch or phenol-free phenoxyethanol, which is initially introduced into thecontainer 10, via the falling-film evaporator 15 and is initially operated with total reflux. The amount of product used for this purpose is only a fraction of the container volume and is chosen so that thecolumn 2 can just be started up therewith. After the temperature profile in the column has stabilized, the column was fed continuously with a gradually increasing and finally constant stream of the reaction mixture described above. - The feed point was chosen so that the
column 2 had both a stripping section and a rectification section (ii). - In this way, the phenol contents of about 10 ppm were achieved in the bottom.
- Under reflux conditions and an absolute pressure of 30 mbar, a temperature of 130° C. was established at the top of the
column 5 and a temperature of 155° C. at the bottom. At a pressure difference regulated to 18 mbar, the pressure at the top of the column was kept at from 30 to 40 mbar. During step a), a forerun, whose phenol content is checked, is taken off via the top of the column. - The bottom discharge of
bottom 6 of the column is passed into thecontainer 10. When the container was filled to its maximum level, the feed was stopped by changing over feed valve V1 and step b) was immediately started and a further forerun taken off. The phenol content in the forerun decreased, and changeover to the main fraction was effected on falling below a certain phenol content dependent on the quality requirements for the main fraction. The main fraction was taken off until a temperature of 157° C. was reached at the bottom of the column, and changeover to total reflux was then effected. The apparatus was then ready for receiving the next batch. After six batches, the bottom product collected in the distillation bulb was discharged after a fraction containing phenoxyethanol and higher homologs have been separated off in last runnings by rectification. - In step a), the
column 2 was fed continuously with a reaction mixture from the nitration of ethylbenzene, which reaction mixture substantially contains ortho- and para-nitroethylbenzene (O-NEB and p-NEB, respectively) and about 7% of meta-nitroethylbenzene (m-NEB) and 0.5% of dinitroethylbenzene (di-NEB). The mixture freed from di-NEB and comprising o-NEB, p-NEB and m-NEB was taken off via thetop 5 of the column and removed into thecontainer 10. A fraction which contained about 10% by mass of di-NEB was taken off via thebottom 6 of the column. - In step b), the
column 2 was fed from thecontainer 10 with the mixture obtained in step a) and comprising o-NEB, p-NEB and m-NEB. The fractions forerun, o-NEB, intermediate cut I and intermediate cut II were taken off in succession via thetop 5 of the column. Since di-NEB and other high boilers had already been removed in step a), pure p-NEB was present in the bottom. Optionally distillation of last runnings with take-off of pure p-NEB via the top follows. - By means of this procedure, it was possible to reduce the residence time of the thermally sensitive di-NEB at high temperatures to about 6 h compared with about 150 h in the conventional batchwise distillation with a column attached to the distillation bulb.
- Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
Claims (13)
1. A process for the distillative separation of mixtures, comprising:
a) continuously supplying a column having a stripping section and a rectification section with a feed, separating the feed into fractions containing at least a low boiler fraction and a high boiler fraction, removing the high boiler fraction continuously into a container; and
b) stopping the feed, recycling the high boiler fraction, removed in step a) into the container, to the column, separating the high boiler fraction batchwise by an ascending procedure into at least a further low boiler fraction and a further high boiler fraction.
2. The process according to claim 1 , wherein the fractions separated in step a) further comprise a medium boiler fraction, and the fraction being separated in step b) further comprise a medium boiler fraction.
3. The process according claim 1 , wherein the step a) or step b) or the step a) and step b), independently of one another, is or are repeated once or several times.
4. The process according to claim 1 , wherein at least one packed column selected from the group consisting of dumped packings, stacked packings, tray columns, dividing wall columns, and thermally coupled columns, is used as the column.
5. The process according to claim 1 , wherein the removal and the residence of the removed fraction in the container are effected without additional heat supply or with cooling.
6. The process according to claim 1 , wherein the residence of the removed fraction in the container is affected with cooling.
7. The process according to claim 1 , wherein step a) is automated.
8. The process according to claim 1 , wherein in step b) the feeding of the column is effected from the container via an evaporator.
9. The process according to claim 8 wherein the evaporator used is a falling-film evaporator or thin-film evaporator.
10. The process according to claim 8 , wherein at least one preheater is connected upstream of the evaporator.
11. The process according to claim 8 , wherein the bottom of the column is filled with sufficient liquid to enable the evaporator to be put into operation, thereby starting up the column.
12. The process according to claim 1 , wherein the continuously supplying a column with a feed is by an intermittent feed or a predetermined ramp feed.
13. The process according to claim 1 , wherein reaction mixtures or solvent mixtures are used as the feed.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/206,898 US20090032389A1 (en) | 2002-05-13 | 2008-09-09 | Process for the mild distillative separation of mixtures |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10221122.1 | 2002-05-13 | ||
DE10221122A DE10221122A1 (en) | 2002-05-13 | 2002-05-13 | Process for gentle distillative separation of mixtures |
US10/435,886 US7435319B2 (en) | 2002-05-13 | 2003-05-12 | Process for the mild distillative separation of mixtures |
US12/206,898 US20090032389A1 (en) | 2002-05-13 | 2008-09-09 | Process for the mild distillative separation of mixtures |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/435,886 Continuation US7435319B2 (en) | 2002-05-13 | 2003-05-12 | Process for the mild distillative separation of mixtures |
Publications (1)
Publication Number | Publication Date |
---|---|
US20090032389A1 true US20090032389A1 (en) | 2009-02-05 |
Family
ID=29265251
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/435,886 Expired - Fee Related US7435319B2 (en) | 2002-05-13 | 2003-05-12 | Process for the mild distillative separation of mixtures |
US12/206,898 Abandoned US20090032389A1 (en) | 2002-05-13 | 2008-09-09 | Process for the mild distillative separation of mixtures |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/435,886 Expired - Fee Related US7435319B2 (en) | 2002-05-13 | 2003-05-12 | Process for the mild distillative separation of mixtures |
Country Status (5)
Country | Link |
---|---|
US (2) | US7435319B2 (en) |
EP (1) | EP1362625A1 (en) |
JP (1) | JP2004066222A (en) |
CN (1) | CN1309439C (en) |
DE (1) | DE10221122A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10569192B2 (en) | 2015-07-03 | 2020-02-25 | Basf Se | Distillation device comprising a column which as three or a plurality of cells in series through which fluid flows and method for distilling or extractive distillation by use of the distillation device |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4500077B2 (en) * | 2004-03-24 | 2010-07-14 | 四日市合成株式会社 | Production method of high purity phenol / ethylene oxide adduct |
JP4500076B2 (en) * | 2004-03-24 | 2010-07-14 | 四日市合成株式会社 | Method for producing high purity phenol / ethylene oxide adduct |
US7525004B2 (en) * | 2007-05-23 | 2009-04-28 | Uop Llc | Process for producing ethylbenzene |
US7498471B2 (en) * | 2007-05-23 | 2009-03-03 | Uop Llc | Process for producing cumene |
US7498472B2 (en) * | 2007-05-23 | 2009-03-03 | Uop Llc | Process for producing ethylbenzene |
US7525005B2 (en) * | 2007-05-23 | 2009-04-28 | Uop Llc | Process for producing cumene |
US7525006B2 (en) * | 2007-05-23 | 2009-04-28 | Uop Llc | Process for producing cumene |
US7713386B2 (en) * | 2007-05-23 | 2010-05-11 | Uop Llc | Apparatus for producing ethylbenzene or cumene |
US7525003B2 (en) * | 2007-05-23 | 2009-04-28 | Uop Llc | Process for producing ethylbenzene |
CA2706104C (en) | 2010-06-17 | 2011-11-22 | Poutrelles Modernes Ltee | Top-chord bearing joist |
US9714388B1 (en) * | 2015-06-23 | 2017-07-25 | Rohit D. Joshi | Method for recycling liquid waste |
CN106693431A (en) * | 2017-03-17 | 2017-05-24 | 河南中托力合化学有限公司 | Novel heptane precise fractionation device |
CN113617041B (en) * | 2021-07-21 | 2022-11-29 | 邳州市鑫盛创业投资有限公司 | Reboiler for alcohol processing |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5223101A (en) * | 1991-02-22 | 1993-06-29 | Phillips Petroleum Company | Low color, low turbidity sulfolane |
US5443695A (en) * | 1993-02-26 | 1995-08-22 | Athens Corporation | Distillation apparatus for concentrating less volatile liquids |
US5705039A (en) * | 1995-10-13 | 1998-01-06 | Albemarle Corporation | Process for purifying a 2,6-dialkylphenol |
US6485613B1 (en) * | 1997-11-04 | 2002-11-26 | Continental Engineering B.V. | Batch-continuous countercurrent mass transfer process |
US6550274B1 (en) * | 2001-12-05 | 2003-04-22 | Air Products And Chemicals, Inc. | Batch distillation |
Family Cites Families (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2939293A (en) * | 1958-04-07 | 1960-06-07 | Phillips Petroleum Co | Start-up procedure-gas fractionator |
US3493468A (en) * | 1966-03-24 | 1970-02-03 | Giovanni Mascarini Soc Ing | Apparatus for automatic starting and control of vapor compression distillation |
US3666633A (en) * | 1969-10-28 | 1972-05-30 | Du Pont | Recovery of chlorinated alkane solvent |
US4568356A (en) * | 1978-11-09 | 1986-02-04 | Chambers John M | Process for making anhydrous alcohol for mixing with gasoline to make gasohol motor fuel |
JPS5688791A (en) * | 1979-12-22 | 1981-07-18 | Tsukishima Kikai Co Ltd | Distillation device for ethyl alcohol with added salt |
DE3446265A1 (en) * | 1984-12-19 | 1986-06-19 | Haarmann & Reimer Gmbh, 3450 Holzminden | METHOD FOR PURIFYING RAW SS PHENYLETHYL ALCOHOL |
DE3725925A1 (en) * | 1987-08-05 | 1989-02-16 | Basf Ag | METHOD FOR OBTAINING N-ETHYLPIPERAZINE |
US5059288A (en) * | 1989-11-21 | 1991-10-22 | Harborchem | Recovery of isopropyl acetate and ethanol from an isopropyl acetate, ethanol and water-containing stream |
US5268073A (en) * | 1990-04-07 | 1993-12-07 | Bayer Aktiengesellschaft | Continuous process for concentrating solutions containing salts and resins |
DE4226905A1 (en) | 1992-08-14 | 1994-02-17 | Basf Ag | Process for carrying out distillative separations in a batch mode |
US5374767A (en) * | 1993-04-15 | 1994-12-20 | E. I. Du Pont De Nemours And Company | Process for the production of cyclohexyladipates and adipic acid |
EP0638345B2 (en) | 1993-07-08 | 2001-04-18 | BASF Aktiengesellschaft | Process for performing destillative separations in a discontinuous method of operation |
DE19602640A1 (en) * | 1996-01-25 | 1997-07-31 | Basf Ag | Process and evaporator for evaporating compounds sensitive to oxidation |
US6982026B2 (en) * | 2001-03-15 | 2006-01-03 | Tate & Lyle Ingredients Americas, Inc. | Azeotropic distillation process for producing organic acids or organic acid amides |
-
2002
- 2002-05-13 DE DE10221122A patent/DE10221122A1/en not_active Withdrawn
-
2003
- 2003-05-02 EP EP03009997A patent/EP1362625A1/en not_active Withdrawn
- 2003-05-12 US US10/435,886 patent/US7435319B2/en not_active Expired - Fee Related
- 2003-05-13 CN CNB031312950A patent/CN1309439C/en not_active Expired - Fee Related
- 2003-05-13 JP JP2003135039A patent/JP2004066222A/en active Pending
-
2008
- 2008-09-09 US US12/206,898 patent/US20090032389A1/en not_active Abandoned
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5223101A (en) * | 1991-02-22 | 1993-06-29 | Phillips Petroleum Company | Low color, low turbidity sulfolane |
US5443695A (en) * | 1993-02-26 | 1995-08-22 | Athens Corporation | Distillation apparatus for concentrating less volatile liquids |
US5705039A (en) * | 1995-10-13 | 1998-01-06 | Albemarle Corporation | Process for purifying a 2,6-dialkylphenol |
US6485613B1 (en) * | 1997-11-04 | 2002-11-26 | Continental Engineering B.V. | Batch-continuous countercurrent mass transfer process |
US6550274B1 (en) * | 2001-12-05 | 2003-04-22 | Air Products And Chemicals, Inc. | Batch distillation |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10569192B2 (en) | 2015-07-03 | 2020-02-25 | Basf Se | Distillation device comprising a column which as three or a plurality of cells in series through which fluid flows and method for distilling or extractive distillation by use of the distillation device |
Also Published As
Publication number | Publication date |
---|---|
DE10221122A1 (en) | 2003-12-04 |
US7435319B2 (en) | 2008-10-14 |
CN1309439C (en) | 2007-04-11 |
EP1362625A1 (en) | 2003-11-19 |
CN1457913A (en) | 2003-11-26 |
US20040020757A1 (en) | 2004-02-05 |
JP2004066222A (en) | 2004-03-04 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20090032389A1 (en) | Process for the mild distillative separation of mixtures | |
US7649108B2 (en) | Process for the distillation of a mixture of isomeric diisocyanatodiphenylmethanes | |
CN101980758B (en) | Batch process and system for the production of olefins | |
US4327184A (en) | Inert-gas stripping and distillation apparatus | |
CN1896047B (en) | Method for preparing toluenediamine | |
EP0160553B1 (en) | Process for distillation of styrenes | |
US4390398A (en) | Modified process for resin manufacturing using a continuous separate distillation column | |
EP2177501B3 (en) | Method and plant for the production of ethanol amines | |
EP3556745B1 (en) | Toluene diisocyanate purification method | |
US3897314A (en) | Process for removing distillation residue from crude isocyanates | |
EP3366664B1 (en) | Phenol purification method | |
KR102357192B1 (en) | Complex Heat Exchange Type Fractionation Distillation Device of Multi-Component Azeotropic Mixture and Fractionation Distillation Method Using the Same | |
US4994152A (en) | Removal of small amounts of a medium-boiling fraction from a liquid mixture by distillation | |
CN107837552B (en) | Operation and control method of dividing wall rectifying tower | |
US3493470A (en) | Volatile components by vaporization while maintaining the desired rate of vaporization by overhead flow control | |
CN107837553B (en) | Operation control method of dividing wall tower | |
US6365006B1 (en) | Method for distilling a mixture of substances and device for realizing the same | |
JPH07136403A (en) | Method for performing distillation separation by means of batch process | |
US3325532A (en) | Manufacture of adiponitrile | |
CA2101461A1 (en) | Carrying out batchwise distillative separations | |
US20210292270A1 (en) | Method for obtaining pure cyclohexyl(meth)acrylate by distillation | |
US2400370A (en) | Process and apparatus for producing in the pure state, butyl alcohol, acetone, and ethyl alcohol from watery solutions | |
US4075287A (en) | Separation process | |
US20240009591A1 (en) | Distillation unit and method for separating a liquid substance mixture into two to six liquid product flows with different compositions | |
WO2021096421A1 (en) | Method for purification of meta-phenylenediamine |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: LANXESS DEUTSCHLAND GMBH, GERMANY Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BAYER AG;REEL/FRAME:021608/0543 Effective date: 20061122 Owner name: BAYER AKTIENGESELLSCHAFT, GERMANY Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:DEIBELE, LUDWIG;HEINZ, DIETER;LEU, JAN THOMAS;AND OTHERS;REEL/FRAME:021608/0397;SIGNING DATES FROM 20030708 TO 20030729 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |