CN117069565A - Purification system and purification method of 2, 6-xylenol - Google Patents
Purification system and purification method of 2, 6-xylenol Download PDFInfo
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- CN117069565A CN117069565A CN202311029030.0A CN202311029030A CN117069565A CN 117069565 A CN117069565 A CN 117069565A CN 202311029030 A CN202311029030 A CN 202311029030A CN 117069565 A CN117069565 A CN 117069565A
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- Prior art keywords
- tower
- cresol
- xylenol
- feed mixture
- percent
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- NXXYKOUNUYWIHA-UHFFFAOYSA-N 2,6-Dimethylphenol Chemical compound CC1=CC=CC(C)=C1O NXXYKOUNUYWIHA-UHFFFAOYSA-N 0.000 title claims abstract description 258
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000000746 purification Methods 0.000 title claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 92
- 239000000203 mixture Substances 0.000 claims abstract description 91
- 239000007788 liquid Substances 0.000 claims abstract description 16
- 238000000926 separation method Methods 0.000 claims abstract description 14
- QWVGKYWNOKOFNN-UHFFFAOYSA-N o-cresol Chemical compound CC1=CC=CC=C1O QWVGKYWNOKOFNN-UHFFFAOYSA-N 0.000 claims description 86
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims description 80
- RLSSMJSEOOYNOY-UHFFFAOYSA-N m-cresol Chemical compound CC1=CC=CC(O)=C1 RLSSMJSEOOYNOY-UHFFFAOYSA-N 0.000 claims description 72
- IWDCLRJOBJJRNH-UHFFFAOYSA-N p-cresol Chemical compound CC1=CC=C(O)C=C1 IWDCLRJOBJJRNH-UHFFFAOYSA-N 0.000 claims description 68
- 230000018044 dehydration Effects 0.000 claims description 54
- 238000006297 dehydration reaction Methods 0.000 claims description 54
- 238000000605 extraction Methods 0.000 claims description 43
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 31
- 238000004821 distillation Methods 0.000 claims description 21
- 238000009835 boiling Methods 0.000 claims description 19
- RDOXTESZEPMUJZ-UHFFFAOYSA-N anisole Chemical compound COC1=CC=CC=C1 RDOXTESZEPMUJZ-UHFFFAOYSA-N 0.000 claims description 18
- 238000010992 reflux Methods 0.000 claims description 16
- 238000007701 flash-distillation Methods 0.000 claims description 14
- 239000000126 substance Substances 0.000 claims description 12
- 238000012856 packing Methods 0.000 claims description 10
- UZKWTJUDCOPSNM-UHFFFAOYSA-N methoxybenzene Substances CCCCOC=C UZKWTJUDCOPSNM-UHFFFAOYSA-N 0.000 claims description 9
- NKTOLZVEWDHZMU-UHFFFAOYSA-N 2,5-xylenol Chemical compound CC1=CC=C(C)C(O)=C1 NKTOLZVEWDHZMU-UHFFFAOYSA-N 0.000 claims description 8
- 238000001704 evaporation Methods 0.000 claims description 7
- 230000008020 evaporation Effects 0.000 claims description 7
- 150000000345 2,6-xylenols Chemical class 0.000 claims description 4
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims description 4
- 239000011552 falling film Substances 0.000 claims description 4
- 238000005292 vacuum distillation Methods 0.000 claims description 4
- XRUGBBIQLIVCSI-UHFFFAOYSA-N 2,3,4-trimethylphenol Chemical compound CC1=CC=C(O)C(C)=C1C XRUGBBIQLIVCSI-UHFFFAOYSA-N 0.000 claims description 3
- 125000000113 cyclohexyl group Chemical group [H]C1([H])C([H])([H])C([H])([H])C([H])(*)C([H])([H])C1([H])[H] 0.000 claims 1
- 238000011084 recovery Methods 0.000 abstract description 6
- 239000012071 phase Substances 0.000 description 25
- 239000007791 liquid phase Substances 0.000 description 5
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000005804 alkylation reaction Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 150000002989 phenols Chemical class 0.000 description 3
- 239000011555 saturated liquid Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000000284 extract Substances 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 125000000552 p-cresyl group Chemical group [H]C1=C([H])C(=C([H])C([H])=C1O*)C([H])([H])[H] 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- 238000003809 water extraction Methods 0.000 description 2
- 150000003739 xylenols Chemical class 0.000 description 2
- 239000008346 aqueous phase Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000012074 organic phase Substances 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 229920013636 polyphenyl ether polymer Polymers 0.000 description 1
- 238000001577 simple distillation Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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
- B01D3/146—Multiple effect distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/685—Processes comprising at least two steps in series
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
- C07C37/74—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by distillation
Abstract
The application discloses a purification system and a purification method of 2, 6-xylenol. The method for purifying 2, 6-xylenol comprises the following steps: s1: distilling a first portion of the water from the feed mixture to form a first portion of 2, 6-xylenol that azeotropes with the first portion of water; s2: rectifying the overhead obtained in the step S1 to obtain a purified first part of 2, 6-xylenol; s3: s1, distilling out residual water and a second organic component forming an azeotrope with the residual water from the bottom liquid obtained in the step S1; s4: rectifying the overhead obtained in the step S3 to obtain a second part of 2, 6-xylenol; and (3) rectifying and separating the tower bottom liquid obtained in the step (S3) to obtain a third part of 2, 6-xylenol. The purification method can realize the purification and separation of the 2, 6-xylenol with high purity and high recovery rate in a complex azeotropic system.
Description
Technical Field
The application relates to a purification system and a purification method of 2, 6-xylenol.
Background
The 2, 6-xylenol, also called 2, 6-xylenol, is an important fine chemical intermediate and chemical raw material, has wide application, can be used for producing pesticide intermediate, medicine raw material and polyphenyl ether engineering plastic, and has very broad industrial application prospect. Commercially available 2, 6-dimethylphenol is obtained by chemical synthesis, and the production process comprises the steps of carrying out gas-phase alkylation reaction on raw materials consisting of phenol or o-cresol, methanol and water in a catalytic reactor, and finally separating the mixture after the reaction to obtain the 2, 6-dimethylphenol.
The mixture after the reaction contains various organic matters including methanol, water, anisole, phenol, o-cresol, m-cresol, p-cresol, 2, 6-dimethylphenol, tricresyl and components and the like. Wherein, various components such as anisole, phenol, 2, 6-dimethylphenol, o-cresol, m-cresol, p-cresol and the like are azeotroped with water, and the azeotropic systems are mutually influenced, so that a reasonable separation sequence cannot be determined simply by phase diagram analysis; and the boiling points of m-cresol, p-cresol and 2, 6-dimethylphenol are very close (the boiling point difference is about 1 ℃), the 2, 6-dimethylphenol with high purity (99.9 wt%) is difficult to obtain, and the 2, 6-dimethylphenol can be purified and the higher product yield is more difficult to obtain.
Accordingly, there is a need to provide a system and method for separating and purifying 2, 6-dimethylphenol with high purity and high product yield.
Disclosure of Invention
The application aims to overcome the defect that the separation and purification of the 2, 6-xylenol with high purity and high yield are difficult to realize in the prior art, and provides a purification system and a purification method of the 2, 6-xylenol. The purification system and the purification method of the 2, 6-xylenol can realize the separation of the 2, 6-xylenol with high purity and high recovery rate.
The application adopts the following technical scheme to solve the technical problems:
the multi-component rectification separation, the conventional separation method in the field adopts a plurality of rectification towers, one or more components are separated from each rectification tower, and the target product is often obtained at the top or bottom of one rectification tower; the application creatively separates and extracts the target product 2, 6-xylenol from a plurality of rectifying towers aiming at a complex azeotrope system, and finally obtains the 2, 6-xylenol with high purity and high comprehensive yield after mixing.
The application provides a method for purifying 2, 6-xylenol, which comprises the following steps:
s1: distilling a first portion of water from the feed mixture and a first portion of 2, 6-xylenol that forms an azeotrope with the first portion of water;
s2: rectifying the tower top distillate obtained in the step S1 to obtain purified first part of 2, 6-xylenol;
s3: s1, distilling residual water and a second organic component forming an azeotrope with the residual water from the tower bottom liquid obtained in the step S1;
s4: rectifying the overhead obtained in the step S3 to obtain a second part of 2, 6-xylenol; rectifying and separating the tower kettle liquid obtained in the step S3 to obtain a third part of 2, 6-xylenol;
wherein the order of S2 and S3 is not sequential; the feed mixture comprises water, 2, 6-xylenol, and an azeotropic heavy component, which refers to an azeotrope with water and an azeotropic point T 2 Greater than the azeotropic point T of 2, 6-xylenol with water 1 Is composed of the components of (1).
In S1, the azeotropic heavy component preferably comprises phenol and/or o-cresol, more preferably also m-cresol and p-cresol, still more preferably also a heavy component having a boiling point higher than 2, 6-xylenol.
Wherein the heavy component preferably comprises tricresyl and/or 2, 5-xylenol.
In S1, preferably more than 95wt% of the azeotropic heavy component is withdrawn from the bottom of the column, more preferably more than 99wt% of the azeotropic heavy component is withdrawn from the bottom of the column.
In S1, the feed mixture preferably further comprises an azeotropic light component, which means that an azeotrope is formed with water and has an azeotropic point T 3 Less than T 1 Is composed of the components of (1).
Wherein the azeotropic light component preferably comprises anisole.
Wherein preferably more than 90wt% of the azeotrope formed by the azeotropic light component and water is distilled off from the top of the column, for example 94.7wt% is distilled off from the top of the column.
In S1, the feed mixture preferably further comprises light components that do not form an azeotrope with water and have a boiling point lower than 2, 6-xylenol.
Wherein the boiling point of the light component is preferably not higher than 100 ℃, more preferably not higher than 70 ℃.
Wherein the light component preferably comprises methanol.
Wherein, preferably, in the distillation, more than 99% of the light component is distilled out from the top of the column, more preferably all is distilled out from the top of the column.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 10-40% of water, 2-15% of phenol, 10-30% of o-cresol and 20-50% of 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 15 to 25 percent of water, 2 to 7 percent of phenol, 10 to 25 percent of o-cresol and 20 to 40 percent of 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol and 29.295% 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol and 0.1 to 5 percent of tricresyl; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol and 0.905% trimethylphenol; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol, 0.1 to 5 percent of tricresyl and 0.01 to 1 percent of anisole; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol, 0.905% tricresyl and 0.088% methyl ether; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol, 0.1 to 5 percent of tricresyl, 0.01 to 1 percent of anisole and 10 to 40 percent of methanol; wherein the percentages are the mass percentages of the components in the feed mixture.
In certain preferred embodiments of the present application, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol, 0.905% tricresyl, 0.088% methyl ether and 26.686% methanol; wherein the percentages are the mass percentages of the components in the feed mixture.
In S1, the distillation is understood by those skilled in the art to mean that the components are separated by exploiting the difference in saturated vapor pressure of the components in a homogeneous liquid mixture.
Wherein the distillation may be any one of equilibrium distillation, simple distillation and rectification, preferably equilibrium distillation, i.e. flash distillation.
The equilibrium distillation is a phenomenon that saturated liquid at high pressure becomes saturated vapor and saturated liquid at partial pressure of a container due to sudden pressure drop after the saturated liquid enters a container at relatively low pressure, and is also called flash evaporation.
In S1, the proportion of the first portion of water is preferably 50% to 99%, more preferably 55% to 85%, for example 79.55%, 58.4% or 83.58%, wherein the percentage is the mass percentage of the first portion of water in the feed mixture.
The person skilled in the art, knowing the above feed mixture system and the separation design concept of the present application, can obtain a specific separation method, preferably according to the following specific separation method:
in S1, the feed pressure of the feed mixture may be any pressure conventional in the art above that of the vessel for distillation as described in S1, preferably 1800 to 2200mbar, more preferably 2000 mbar.
In S1, the pressure of the distillation is preferably 0.08 to 0.12MPa, more preferably 0.1MPa.
Wherein the pressure of the distillation refers to the pressure in the vessel of the distillation, such as the operating pressure of a flash column, as known to those skilled in the art.
In S1, the temperature of the distillation may be conventional in the art, preferably 80-90 ℃, more preferably 87 ℃, wherein the temperature of the distillation refers to the overhead temperature.
In S1, the distillation overhead reflux ratio can be conventional in the art, preferably 1 to 5, more preferably 2.
In S1, it is known to those skilled in the art that the overhead composition of S1 is determined by the composition of the feed mixture, the azeotrope composition at the operating pressure of the flash column, and the overhead temperature of the flash column.
In S2, the method for obtaining the first part of 2, 6-xylenol by rectification may be conventional in the art, and preferably the first part of 2, 6-xylenol is obtained at the bottom of the column by adding an entrainer which forms a low boiling residue with water.
Wherein the low-boiling-point substance refers to an azeotrope with an azeotropic point not higher than 100 ℃ under normal pressure.
Wherein the entrainer may be conventional in the art, preferably cyclohexane.
Wherein the entrainer may be added in an amount conventional in the art and is generally determined by the composition of the azeotrope formed by the entrainer and water.
Wherein, preferably, the obtained tower top gas enters the phase separator for layering after condensation, water at the upper layer is extracted, and materials at the lower layer are refluxed.
In S2, when the light component is also included in the feed mixture, the overhead from S1 is first separated from the light component and the azeotropic light component, and water and the first portion of 2, 6-xylenol are separated.
In S3, it is known to those skilled in the art that the overhead from S3 comprises the remaining water, the second portion of 2, 6-xylenol, and a portion of the azeotropic heavies.
In S4, preferably, the tower top distillate obtained in S3 is rectified and separated to obtain the residual water, and the obtained organic component is rectified and separated to obtain the second part of 2, 6-xylenol.
The method for separating the residual water by rectification can be conventional in the art, and preferably the entrainer and the residual water are formed into low-boiling substances by adding the entrainer and then rectified and separated.
Wherein the low-boiling-point substance refers to an azeotrope with an azeotropic point not higher than 100 ℃ under normal pressure.
Wherein the entrainer may be conventional in the art, preferably cyclohexane.
Wherein the entrainer may be added in an amount conventional in the art and is generally determined by the composition of the azeotrope formed by the entrainer and water.
Wherein the resulting low boiling residue comprises water and the entrainer, preferably separated by a phase separator, the resulting aqueous phase is recovered and the resulting organic phase is refluxed.
Wherein the purity of the second portion of 2, 6-xylenol may be conventional in the art, preferably not less than 99%, more preferably not less than 99.9%, e.g., 99.977%.
Wherein said separating said obtained organic component by distillation to obtain said second portion of 2, 6-xylenol may be accomplished by distillation means conventional in the art, preferably, when said feed mixture comprises said phenol and said o-cresol, said obtained organic component is distilled to separate said phenol and then distilled to separate said o-cresol and said second portion of 2, 6-xylenol.
Preferably, the rectification separation of the o-cresol and the second portion of 2, 6-xylenol employs a reduced pressure rectification process.
Further preferably, the pressure reduction rectification is operated at a pressure of from 0.01 to 0.5bara, for example 0.1bara.
Further preferably, the reflux ratio of the top of the vacuum rectification is adjusted conventionally according to the purity of the second part of 2, 6-xylenol.
The purity of the resulting o-cresol may be conventional in the art, and is preferably not less than 99%, such as 99.950%, where the percentages are all mass percentages.
In S4, rectifying and separating the tower bottom liquid obtained in S3 to obtain a third part of 2, 6-xylenol by a conventional rectifying method in the field; preferably, when the feed mixture comprises m-cresol and p-cresol, the third portion of 2, 6-xylenol is separated from the m-cresol and p-cresol by vacuum distillation.
The inventors of the present application have creatively found that m-cresol and p-cresol form an azeotrope with a higher azeotropic point, which can be separated from the third part of 2, 6-xylenol by means of rectification to obtain high purity 2, 6-xylenol.
Wherein the pressure of operation of the vacuum distillation is preferably from 0.05 to 0.5bara, more preferably 0.1bara.
Wherein, the reflux ratio of the top of the vacuum rectification column can be as long as the purity requirement of the third part of 2, 6-xylenol is satisfied conventionally in the field, and is preferably 12-20, more preferably 16.
Wherein when the feed mixture further comprises the xylenol and the 2, 5-xylenol, the tower bottoms of the reduced pressure rectification further comprise the xylenol and the 2, 5-xylenol.
The application also provides a method for purifying 2, 6-xylenol from m-cresol and p-cresol, which comprises the following steps: and (3) carrying out reduced pressure rectification on the feed mixture, wherein the operating pressure of the reduced pressure rectification is 0.05-0.5 bara, and the feed mixture comprises m-cresol, p-cresol and 2, 6-xylenol.
The present application also provides a system for performing the method of purifying 2, 6-xylenol as described above, comprising:
a flash column;
the feeding port of the first dehydration tower is connected with the top extraction port of the flash evaporation tower; the first dehydration tower is provided with an entrainer feeding port;
the bottom extraction port of the flash distillation tower is connected with the feed inlet of the first rectification tower;
the top extraction outlet of the flash evaporation tower is connected with the feed inlet of the second dehydration tower, and the second dehydration tower is provided with an entrainer feed inlet;
and the bottom extraction outlet of the second dehydration tower and/or the bottom extraction outlet of the first rectification tower is connected with the feed inlet of the second rectification tower and is used for separating the second part of 2, 6-xylenol from the azeotropic heavy component.
In the present application, the theoretical plate number of the flash column is preferably 40 to 60, for example 50.
In the present application, the number of theoretical plates of the first dehydration column is preferably 15 to 25, for example 20.
In the present application, the theoretical plate number of the second dehydration column is preferably 12 to 18, for example 15.
In the present application, the theoretical plate number of the first rectifying column is preferably 40 to 60, for example, 50.
In the present application, the theoretical plate number of the second rectifying column is preferably 50 to 90, for example 65, 70 or 75.
In the present application, the flash distillation column, the first rectification column, the second rectification column, the first dehydration column and the second dehydration column may be conventional rectification columns in the art, preferably independently a packed rectification column, more preferably independently a high-efficiency structured packing rectification column, and even more preferably independently a high-efficiency plate corrugated structured packing rectification column.
Wherein the equal plate height HETP of the efficient structured packing is preferably 200 mm-300 mm.
The efficient plate ripple structured packing has the advantages of high separation efficiency and low pressure drop. Can effectively reduce the tower height, reduce the tower diameter, reduce the pressure drop of the whole tower, reduce the temperature of the tower kettle, improve the coking condition of materials, improve the product quality and improve the yield.
In the application, the bottoms of the flash distillation tower, the first rectifying tower, the second rectifying tower, the first dehydrating tower and the second dehydrating tower are all provided with tower kettle reboilers as known by the person skilled in the art.
Wherein the bottoms reboiler may be a conventional in the art, preferably a falling film reboiler.
The system to be separated is a thermosensitive system, and the temperature and the residence time are required to be reduced as much as possible in the rectification process. The liquid phase of the falling film reboiler is fed from the top of the reboiler, a liquid phase film is formed under the action of gravity, and the gas phase is generated in the heat exchange tube along with the evaporation of the downward liquid phase, so that the liquid phase film becomes thinner gradually along with the increase of the gas phase quantity. The liquid phase quantity in the heat exchange tube is accelerated to drop due to the action of the gas phase and the gravity. The heat exchanger has the advantages of low pressure drop, low inlet-outlet temperature difference and short residence time, and is especially suitable for thermosensitive systems.
In the application, the person skilled in the art knows that the bottom of the first dehydration tower is provided with a first part of 2, 6-xylenol extraction outlet, and the top of the first dehydration tower is provided with a first part of water extraction outlet.
In the present application, preferably, the top condenser of the first dehydration column is connected to a first phase separator, and the bottom outlet of the first phase separator is connected to the reflux port of the first dehydration column.
In the present application, when the light component as described above is further contained in the feed mixture, preferably, a light component removal column is further disposed between the flash distillation column and the first dehydration column, a top outlet of the flash distillation column is connected to the feed inlet of the light component removal column, a top outlet of the light component removal column is provided, and a bottom outlet of the light component removal column is connected to the first dehydration column.
Wherein, the theoretical plate number of the light component removal tower is preferably 15-25, for example 20.
In the application, the top condenser of the second dehydration tower is connected with a second phase separator, and the bottom outlet of the second phase separator is connected with the reflux port of the second dehydration tower and is used for refluxing entrainer and organic components obtained after water separation.
In the application, the connection of the bottom outlet of the second dehydration tower and/or the bottom outlet of the first rectification tower with the feed inlet of the second rectification tower means any one of three schemes that the bottom outlet of the second dehydration tower and the bottom outlet of the first rectification tower are connected with the feed inlet of the second rectification tower, the bottom outlet of the second dehydration tower is connected with the feed inlet of the second rectification tower, and the bottom outlet of the first rectification tower is connected with the feed inlet of the second rectification tower.
In the application, the system parameters of the second rectifying tower, such as feeding position, theoretical plate number and the like, are calculated and set according to the routine in the field.
In the present application, preferably, when the azeotropic heavy component includes the phenol and the o-cresol, the second rectifying tower includes a phenol tower and a product tower connected in series, a feed inlet of the phenol tower is connected to a bottom outlet of the second dehydrating tower, and a bottom outlet of the phenol tower is connected to a feed inlet of the product tower.
Wherein, preferably, the top of the phenol tower is provided with a phenol extraction outlet.
Wherein, preferably, the top of the product tower is provided with an o-cresol extraction port, and the bottom of the product tower is provided with a second part of 2, 6-xylenol extraction port.
Wherein, preferably, when the azeotropic heavy component further comprises m-cresol and p-cresol, the second rectifying tower further comprises a mixed phenol tower, and the feed inlet of the mixed phenol tower is connected with the bottom extraction outlet of the first rectifying tower and is used for separating the third part of 2, 6-xylenol from the m-cresol and the p-cresol.
Preferably, the top of the mixed phenol tower is provided with a third part of 2, 6-xylenol extraction port, and the bottom of the mixed phenol tower is provided with a mixed phenol extraction port.
Wherein the theoretical plate number of the phenol tower is preferably 55 to 75, for example 65.
Wherein the theoretical plate number of the product column is preferably 65 to 90, for example 75.
Wherein the theoretical plate number of the mixed phenol tower is preferably 60 to 80, for example 70.
The application also provides a method for purifying 2, 6-xylenol and o-cresol from o-cresol, m-cresol and p-cresol, which comprises the following steps: and (3) carrying out reduced pressure rectification on the feed mixture, wherein the operating pressure of the reduced pressure rectification is 0.05-0.5 bara, and the feed mixture comprises m-cresol, p-cresol and 2, 6-xylenol.
In the present application, the theoretical plate number of the vacuum rectification is preferably not less than 60, more preferably 60 to 90, still more preferably 70.
In the present application, the temperature of the top of the vacuum rectification column is preferably 130 to 150 ℃, more preferably 135 to 145 ℃, still more preferably 140 ℃.
In the application, the temperature of the tower kettle of the reduced pressure rectification is preferably 140-160 ℃, more preferably 145-155 ℃, and even more preferably 150 ℃.
In the present application, the reflux at the top of the vacuum rectification is preferably not less than 12, more preferably 15 to 20, still more preferably 16.
In the present application, the feed mixture may further include components having boiling point differences from m-cresol, p-cresol and 2, 6-xylenol of not less than 5.
Wherein, preferably, the boiling point difference is not less than 10, more preferably not less than 20 ℃.
In a preferred embodiment of the application, the feed mixture further comprises tricresyl.
On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the application.
The reagents and materials used in the present application are commercially available.
The application has the positive progress effects that: the purification system and the purification method can realize the purification of the 2, 6-xylenol with high purity and high yield, the purity can reach more than 99.9 percent, and the recovery rate can reach more than 99 percent.
Drawings
FIG. 1 is a purification system for 2, 6-xylenol of example 1.
The reference numerals are as follows:
1-a flash column; 2-a light component removing tower; 3-a first dehydration column; 4-a first rectifying tower; 5-a mixed phenol column; 6-a second dehydration column; 7-phenol tower; 8-a product column; 301-a first phase separator; 601-a second phase separator; 1001-feeding a mixture; 1002-methanol; 1003-first portion of water; 1004-a first portion of 2, 6-xylenol; 1005-remaining water; 1006-phenol; 1007-o-cresol; 1008-a second portion of 2, 6-xylenol; 1009-third portion 2, 6-xylenol; 1010-mixed phenols; 1011-entrainer.
Detailed Description
The application is further illustrated by means of the following examples, which are not intended to limit the scope of the application. The experimental methods, in which specific conditions are not noted in the following examples, were selected according to conventional methods and conditions, or according to the commercial specifications.
Example 1
Referring to fig. 1, the purification system of 2, 6-xylenol of the present embodiment includes:
a flash column 1;
the top extraction outlet of the flash distillation tower 1 is connected with the feed inlet of the light component removal tower 2, and the top of the light component removal tower 2 is provided with a light component extraction outlet;
the tower top extraction outlet of the light component removal tower 2 is connected with the feed inlet of the first dehydration tower 3, and the first dehydration tower 3 is also provided with an entrainer feed inlet; the top condenser of the first dehydration tower 3 is connected with a first phase separator 301 for layering a first part of water 1003, an entrainer 1011 and a small amount of organic components, the top of the first phase separator 301 is provided with a first part of water 1003 extraction outlet, and the bottom of the first phase separator 301 is connected with the top of the first dehydration tower 3 for refluxing the entrainer and the small amount of organic components; the bottom of the first dehydration tower 3 is provided with a first part of 2, 6-xylenol 1004 extraction outlet;
the bottom extraction port of the flash distillation tower 1 is connected with the feed inlet of the first rectifying tower 4;
the feed inlet of the second dehydration tower 6 is connected with the top extraction outlet of the first rectifying tower 4; the second dehydration tower 6 is provided with an entrainer feeding port for adding an entrainer 1011; the top condenser of the second dehydration tower 6 is connected with a second phase separator 601, the top of the second phase separator 601 is provided with a second part of water extraction outlet, and the bottom of the second phase separator 601 is connected with the top of the second dehydration tower 6 for reflux of entrainer and a small amount of organic components;
a phenol tower 7, wherein a bottom extraction outlet of the second dehydration tower 6 is connected with a feed inlet of the phenol tower 7, and a phenol extraction outlet is arranged at the top of the phenol tower 7;
the tower bottom extraction port of the phenol tower 7 is connected with the feed inlet of the product tower 8, the tower bottom of the product tower 8 is provided with a second 2, 6-xylenol extraction port, and the tower top of the product tower 8 is provided with an o-cresol 1007 extraction port;
the bottom extraction outlet of the first rectifying tower 4 is connected with the feed inlet of the mixed phenol tower 5; the top of the mixed phenol tower 5 is provided with a third 2, 6-xylenol extraction port, and the bottom of the mixed phenol tower 5 is provided with a mixed phenol extraction port.
The flash distillation tower 1, the light component removal tower 2, the first dehydration tower 3, the first rectifying tower 4, the first dehydration tower 3, the phenol tower 7, the product tower 8 and the mixed phenol tower 5 are all high-efficiency plate ripple structured packing towers, and the packing model is BX Plus high-efficiency structured packing.
The top of the flash distillation tower 1, the light component removal tower 2, the first dehydration tower 3, the first rectifying tower 4, the first dehydration tower 3, the phenol tower 7, the product tower 8 and the mixed phenol tower 5 are all provided with condensers, the bottom of the tower is all provided with a falling film reboiler, the tower bottoms are all heated by adopting 10barg steam, the theoretical plate numbers of the towers are respectively shown in the table 1, and the feeding positions are conventional in the field.
Example 2
The purification system of example 1 was used to separate and purify 2, 6-xylenol from the product of the vapor phase alkylation reaction, with feed mixture 1001 shown in Table 2, as follows: the feed mixture 1001 is rectified in flash column 1, methanol 1002, anisole, a first portion of water 1003 and a first portion of 2, 6-xylenol 1004 are fractionated from the top of flash column 1; the top produced liquid of the flash evaporation tower 1 enters a light component removal tower 2, methanol 1002 is separated from the top of the light component removal tower 2, the bottom produced liquid of the light component removal tower 2 enters a first dehydration tower 3, meanwhile, entrainer 1011 (cyclohexane) enters the first dehydration tower 3 from an entrainer feeding port, entrainer and water form low-boiling substances, the low-boiling substances are distilled out from the top of the first dehydration tower 3, condensed by a condenser and enter a first phase separator 301, a first part of water 1003 and entrainer (containing a small amount of 2, 6-xylenol) are layered in the first phase separator 301, a first part of water 1003 is extracted from a first part of water 1003 outlet of the first phase separator 301, and entrainer and other organic components are refluxed to the top of the first dehydration tower 3 from a top reflux; the bottom of the first dehydration column 3 produces a first portion of 2, 6-xylenol 1004. Wherein the first portion of water 1003 comprises 79.55% by mass of the total water in the feed mixture 1001. Wherein the mass percent of the first portion of water 1003 to the total water in the feed mixture 1001 is calculated from the data in table 2 according to the formula: 730×99.952%/(4568×20.079%) = 79.55%.
The bottom produced liquid of the flash distillation tower 1 also contains a small part of water and various phenolic compounds, the bottom produced liquid enters the first rectifying tower 4 for rectification, the rest water 1004, phenol 1006, o-cresol 1007 and the azeotrope formed by the second part of 2, 6-xylenol 1008 are distilled off from the top of the first rectifying tower 4, and the rest phenolic compounds (mainly comprising the third part of 2, 6-xylenol 1009, m-cresol, p-cresol and tricresyl) are produced from the bottom of the first rectifying tower 4.
The top gas of the first rectifying tower 4 is condensed by a condenser, then partially reflows and partially is extracted to enter a second dehydrating tower 6, meanwhile, an entrainer 1011 (cyclohexane) enters the second dehydrating tower 6 from an entrainer feeding port, the entrainer and the rest water 1005 form low-boiling-point substances, the low-boiling-point substances are distilled out from the top of the second dehydrating tower 6, the low-boiling-point substances enter a second phase separator 601 after being condensed, the rest water 1005 and the entrainer are layered in the second phase separator 601, the rest water 1005 is extracted from the top outlet of the second phase separator 601, and the entrainer flows back to the top of the second dehydrating tower 6 from the bottom outlet of the second phase separator 601.
The bottom produced liquid of the second dehydrating tower 6 enters a phenol tower 7 for rectification, phenol 1006 is distilled out from the top of the phenol tower 7, the bottom produced liquid of the phenol tower 7 enters a product tower 8 for continuous rectification, o-cresol 1007 is produced from the top of the product tower 8, and a second part of 2, 6-xylenol 1008 is produced from the bottom of the product tower 8.
The bottom liquid of the first rectifying column 4 enters the mixed phenol column 5, and m-cresol and p-cresol form an azeotrope having a higher azeotropic point in the mixed phenol column 5, so that the mixed phenol is extracted from the bottom of the mixed phenol column 5 together with trimethylphenol 1010, and a third part of 2, 6-xylenol 1009 is distilled from the top of the mixed phenol column 5.
The operating parameters of each rectifying column are shown in table 1.
The amount of entrainer added in the first dehydration column 3 and the second dehydration column 6 is determined according to the composition of the first part of water 1003 and the entrainer to form low boiling substances and the composition of the rest of water 1005 and the entrainer to form low boiling substances.
The composition, temperature, pressure and flow rate of the produced fluid at each production port are shown in Table 2.
TABLE 1
TABLE 2
Stream 1004, stream 1009 and stream 1008 are all purified 2, 6-xylenols, and the three streams, when mixed, result in a purified 2, 6-xylenol having a purity greater than 99.9% and a recovery of 99.96%.
Example 3
Example 3 the purification system of example 1 was used to separate and purify 2, 6-xylenol from the product of the vapor phase alkylation reaction, with only a first portion of water 1003 being adjusted to 58.4% by mass of the total water in feed mixture 1001 as compared to example 2, wherein the mass of first portion of water 1003 being calculated as follows from the data in table 3: 536×99.952%/(4568×20.079%) =58.4%.
Other operating parameters were the same as in example 2, and the composition, temperature, pressure and flow rate of the produced fluid at each production port were as shown in Table 3.
TABLE 3 Table 3
Stream 1004, stream 1009 and stream 1008 are all purified 2, 6-xylenols, and the three streams, when mixed, result in a purified 2, 6-xylenol having a purity greater than 99.9% and a recovery of 99.99% 2, 6-xylenol.
Example 4
In comparison to example 2, only the mass percentage of the first portion of water 1003 to the total water in the feed mixture 1001 was adjusted to 83.58%, the mass percentage of the first portion of water 1003 to the total water in the feed mixture 1001 was calculated according to the following formula from the data in table 4: 767 x 99.952%/(4568 x 20.079%) = 83.58%.
Other operating parameters were the same as in example 2, and the composition, temperature, pressure and flow rate of the produced fluid at each production port were as shown in Table 4.
TABLE 4 Table 4
Where n/a in stream 1005 indicates that the component is almost free of extract stream 1004, stream 1009 and stream 1008 are all purified 2, 6-xylenols, and the three streams, when mixed, result in a purified 2, 6-xylenol having a purity of greater than 99.9% and a recovery of 99.6%.
Claims (10)
1. A method for purifying 2, 6-xylenol, comprising the steps of:
s1: distilling a first portion of water from the feed mixture and a first portion of 2, 6-xylenol that forms an azeotrope with the first portion of water;
s2: rectifying the tower top distillate obtained in the step S1 to obtain purified first part of 2, 6-xylenol;
s3: s1, distilling out residual water and a second organic component forming an azeotrope with the residual water from the bottom liquid obtained in the step S1;
s4: rectifying the overhead obtained in the step S3 to obtain a second part of 2, 6-xylenol; rectifying and separating the tower bottom liquid obtained in the step S3 to obtain a third part of 2, 6-xylenol;
wherein the order of S2 and S3 is not sequential; the feed mixture comprises water, 2, 6-xylenol, and an azeotropic heavy component, which refers to an azeotrope with water and an azeotropic point T 2 Greater than the azeotropic point T of 2, 6-xylenol with water 1 Is composed of the components of (1).
2. The method for purifying 2, 6-xylenol as set forth in claim 1, wherein: the azeotropic heavier components include phenol and/or o-cresol, preferably also m-cresol and p-cresol, more preferably also heavier components having a boiling point higher than 2, 6-xylenol; the heavy component preferably comprises tricresyl and/or 2, 5-xylenol;
in S1, more than 95wt% of the azeotropic heavy component is withdrawn from the bottom of the column, preferably more than 99wt% of the azeotropic heavy component is withdrawn from the bottom of the column;
in S1, the feed mixture further comprises an azeotropic light component, which means that an azeotrope is formed with water and has an azeotropic point T 3 Less than T 1 Is composed of the components of (1); the azeotropic light component preferably comprises anisole; preferably, in the distillation, more than 90wt% of the azeotrope formed by the azeotropic light component and water is distilled off from the top of the column, for example 94.7wt% is distilled off from the top of the column;
in S1, the feed mixture further comprises light components that do not form an azeotrope with water and have a boiling point below 2, 6-xylenol; the boiling point of the light component is preferably not higher than 100 ℃, more preferably not higher than 70 ℃; the light component preferably comprises methanol; preferably, more than 99wt% of the light component in the distillation is distilled off overhead, more preferably all;
wherein in S2, when the light component is also included in the feed mixture, the overhead from S1 is first separated into the light component and the azeotropic light component, and water is separated from the first portion 2,6-Xylenols.
3. The method for purifying 2, 6-xylenol as set forth in claim 1, wherein: the feed mixture comprises the following components: 10-40% of water, 2-15% of phenol, 10-30% of o-cresol and 20-50% of 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 15 to 25 percent of water, 2 to 7 percent of phenol, 10 to 25 percent of o-cresol and 20 to 40 percent of 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol and 29.295% 2, 6-xylenol; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol and 0.1 to 5 percent of tricresyl; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol and 0.905% trimethylphenol; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol, 0.1 to 5 percent of tricresyl and 0.01 to 1 percent of anisole; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol, 0.905% tricresyl and 0.088% methyl ether; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 10 to 40 percent of water, 2 to 15 percent of phenol, 10 to 30 percent of o-cresol, 20 to 50 percent of 2, 6-xylenol, 0.01 to 1 percent of m-cresol, 0.05 to 1 percent of p-cresol, 0.1 to 5 percent of tricresyl, 0.01 to 1 percent of anisole and 10 to 40 percent of methanol; wherein the percentages are the mass percentages of the components in the feed mixture;
alternatively, the feed mixture comprises the following components: 20.079% water, 5.113% phenol, 17.129% o-cresol, 29.295% 2, 6-xylenol, 0.088% m-cresol, 0.118% p-cresol, 0.905% tricresyl, 0.088% methyl ether and 26.686% methanol; wherein the percentages are the mass percentages of the components in the feed mixture.
4. The method for purifying 2, 6-xylenol as set forth in claim 1, wherein: in S1, the proportion of the first portion of water is 50% to 99%, preferably 55% to 85%, for example 79.55%, 58.4% or 83.58%, wherein the percentage is the mass percentage of the first portion of water to the water in the feed mixture;
and/or, in S1, the feed pressure of the feed mixture is 1800 to 2200mbara, preferably 2000mbara;
and/or, in S1, the pressure of the distillation is 0.08-0.12 MPa, preferably 0.1MPa;
and/or, in S1, the temperature of the distillation is 80-90 ℃, preferably 87 ℃, wherein the temperature of the distillation refers to the overhead temperature;
and/or in S1, the reflux ratio of the top of the distillation column is 1-5, preferably 2;
and/or, in S2, the method for obtaining the first part of 2, 6-xylenol by rectification comprises the steps of adding entrainer which forms low-boiling-point substances with water for rectification, and obtaining the first part of 2, 6-xylenol at the bottom of a tower, wherein the low-boiling-point substances are azeotrope with the azeotropic point not higher than 100 ℃ under normal pressure; the entrainer is preferably cyclohexane.
5. The method for purifying 2, 6-xylenol as set forth in claim 1 or 2, characterized in that: in S4, rectifying the tower top distillate obtained in S3 to separate out the residual water, and rectifying and separating the obtained organic component to obtain the second part of 2, 6-xylenol;
preferably, when the feed mixture comprises phenol and o-cresol, the resulting organic component is first distilled to separate the phenol, and then distilled to separate the o-cresol and the second portion of 2, 6-xylenol; preferably, the rectification separation of the o-cresol and the second part of 2, 6-xylenol adopts a method of vacuum rectification; the pressure at which the vacuum distillation is operated is preferably from 0.01 to 0.5bara, for example 0.1bara; the purity of the resulting o-cresol is preferably not less than 99%, e.g. 99.950%, wherein the percentages are all mass percentages;
and/or, in S4, when the feed mixture contains m-cresol and p-cresol, separating the third part of 2, 6-xylenol from the m-cresol and the p-cresol by adopting a reduced pressure rectification method from the tower bottom liquid obtained in S3; the operating pressure of the vacuum rectification is preferably from 0.05 to 0.5bara, more preferably 0.1bara; the reflux at the top of the vacuum distillation column is preferably 12 to 20, more preferably 16.
6. The method for purifying 2, 6-xylenol as claimed in claim 5, wherein the reduced pressure rectification has a top temperature of 130-150 ℃, preferably 135-145 ℃, more preferably 140 ℃;
and/or the temperature of the tower kettle of the reduced pressure rectification is 140-160 ℃, preferably 145-155 ℃, more preferably 150 ℃;
and/or the reflux ratio of the top of the vacuum rectification is not lower than 12, preferably 15-20, more preferably 16;
and/or the feed mixture further comprises components having boiling point differences from m-cresol, p-cresol and 2, 6-xylenol of no less than 5; the boiling point differences are preferably not less than 10, more preferably not less than 20;
and/or, the feed mixture further comprises tricresyl.
7. A purification system for performing the method for purifying 2, 6-xylenol as defined in any one of claims 1 to 6, comprising:
a flash column;
the feeding port of the first dehydration tower is connected with the top extraction port of the flash evaporation tower; the first dehydration tower is provided with an entrainer feeding port;
the bottom extraction port of the flash distillation tower is connected with the feed inlet of the first rectification tower;
the top extraction outlet of the flash evaporation tower is connected with the feed inlet of the second dehydration tower, and the second dehydration tower is provided with an entrainer feed inlet;
and the bottom extraction outlet of the second dehydration tower and/or the bottom extraction outlet of the first rectification tower is connected with the feed inlet of the second rectification tower and is used for separating the second part of 2, 6-xylenol from the azeotropic heavy component.
8. The purification system of claim 7, wherein the theoretical number of plates of the flash column is 40 to 60, preferably 50;
and/or the theoretical plate number of the first dehydration tower is 15-25, preferably 20;
and/or the theoretical plate number of the second dehydration tower is 12-18, preferably 15;
and/or the theoretical plate number of the first rectifying tower is 40-60, preferably 50;
and/or the theoretical plate number of the second rectifying tower is 50-90, such as 65, 70 or 75.
9. The purification system of claim 8, wherein the flash column, the first rectification column, the second rectification column, the first dehydration column, and the second dehydration column are independently packed rectification columns, preferably are independently high efficiency structured packing rectification columns, more preferably are independently high efficiency plate corrugated structured packing rectification columns; the equal plate height HETP of the efficient structured packing is preferably 200 mm-300 mm;
and/or tower bottom reboilers of the flash tower, the first rectifying tower, the second rectifying tower, the first dehydrating tower and the second dehydrating tower are respectively arranged; the tower kettle reboiler is preferably a falling film reboiler;
and/or the top condenser of the first dehydrating tower is connected with a first phase separator, and the bottom outlet of the first phase separator is connected with the reflux port of the first dehydrating tower;
and/or the top condenser of the second dehydration tower is connected with a second phase separator, and the bottom outlet of the second phase separator is connected with the reflux port of the second dehydration tower and is used for refluxing entrainer and organic components obtained after water separation;
and/or when the feed mixture also contains light components and/or azeotropic light components, a light component removing tower is further arranged between the flash distillation tower and the first dehydrating tower, a top extraction port of the flash distillation tower is connected with a feed port of the light component removing tower, a light component extraction port is arranged at the top of the light component removing tower, and a bottom extraction port of the light component removing tower is connected with the first dehydrating tower; the theoretical plate number of the light component removal tower is preferably 15-25, more preferably 20;
and/or the theoretical plate number of the vacuum rectification is not less than 60, preferably 60 to 90, more preferably 70;
and/or, when the azeotropic heavy component comprises phenol and o-cresol, the second rectifying tower comprises a phenol tower and a product tower which are connected in series, wherein a feed inlet of the phenol tower is connected with a bottom extraction outlet of the second dehydrating tower, and the bottom extraction outlet of the phenol tower is connected with the feed inlet of the product tower; the theoretical plate number of the phenol tower is preferably 55-75, more preferably 65; the theoretical plate number of the product column is preferably 65 to 90, more preferably 75;
preferably, the top of the phenol tower is provided with a phenol extraction outlet; preferably, the top of the product tower is provided with an o-cresol extraction port, and the bottom of the product tower is provided with a second part of 2, 6-xylenol extraction port;
and/or, when the azeotropic heavy component comprises m-cresol and p-cresol, the second rectifying tower further comprises a mixed phenol tower, wherein a feed inlet of the mixed phenol tower is connected with a bottom extraction outlet of the first rectifying tower and is used for separating the third part of 2, 6-xylenol from the m-cresol and the p-cresol;
preferably, the top of the mixed phenol tower is provided with a third part of 2, 6-xylenol extraction port, and the bottom of the mixed phenol tower is provided with a mixed phenol extraction port; the theoretical plate number of the mixed phenol tower is preferably 60 to 80, more preferably 70.
10. A process for the purification of 2, 6-xylenol and o-cresol from o-cresol, m-cresol and p-cresol comprising the steps of: and (3) carrying out reduced pressure rectification on a feed mixture, wherein the operating pressure of the reduced pressure rectification is 0.05-0.5 bara, and the feed mixture comprises o-cresol, m-cresol, p-cresol and 2, 6-xylenol.
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