CN107793300B - Separation process of reaction liquid of polymethoxy dimethyl ether - Google Patents
Separation process of reaction liquid of polymethoxy dimethyl ether Download PDFInfo
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- CN107793300B CN107793300B CN201711091422.4A CN201711091422A CN107793300B CN 107793300 B CN107793300 B CN 107793300B CN 201711091422 A CN201711091422 A CN 201711091422A CN 107793300 B CN107793300 B CN 107793300B
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Abstract
The invention discloses a process for separating reaction liquid of polymethoxy dimethyl ether, which comprises the steps of separating formic acid and water in the reaction liquid, well inhibiting the subsequent reaction of formaldehyde disproportionation into acid, adopting a plate-type column aldehyde-removing column, extracting materials of partial tower plates in the aldehyde-removing column by arranging a circulating pump, overheating by a heater, and then mixing the materials back to an upper plate, increasing the number of tower plates at a high-temperature section of the aldehyde-removing column, being beneficial to vaporization separation of thermosensitive formaldehyde, accelerating thermal decomposition of unstable hemiacetal by heating of a superheater, and solving the problem that the separation cannot be carried out due to the fact that a large amount of formic acid is generated by the heated disproportionation reaction of formaldehyde in the previous simple distillation process and the separation of products decomposed by formic acid is not carried out. The dmmn, n-2-8 component can be selectively obtained by matching with the separation process of the previous stage. And the formaldehyde content and the formic acid content in the tower kettle can be ensured to be almost undetectable, and a high-quality product is obtained. The invention has simple and efficient process and greatly reduces the investment cost.
Description
Technical Field
The invention relates to production of polymethoxy dimethyl ether, in particular to a separation process of reaction liquid of polymethoxy dimethyl ether.
Background
At present, polymethoxy dimethyl ether is mostly generated by reacting methylal/methanol with formaldehyde (formaldehyde can be from aqueous formaldehyde solution/trioxymethylene/paraformaldehyde) under the catalysis of an acid catalyst. For the separation of the residual unreacted formaldehyde in the reaction solution, alkali neutralization reaction is generally adopted, and after the alcohol substances are generated by hydrogenation, conventional rectification separation is carried out. Since the alkali neutralizes formaldehyde in the reaction solution, a large amount of raw materials are consumed, and a large amount of sewage is generated. The industrial production is not economical. Hydrogenation results in high power consumption and high hydrogen cost. If formaldehyde is not treated and is directly distilled, the temperature is high, and the formaldehyde is easily subjected to disproportionation reaction to generate formic acid in the process of heating and vaporizing reaction liquid. The formic acid decomposes the product during the separation process to produce methylal and formaldehyde. The process has low separation efficiency, and the product is further decomposed.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of separation of residual unreacted formaldehyde in reaction liquid in production of polymethoxy dimethyl ether and unsatisfactory separation technology in the prior art, and provides a separation process of the reaction liquid of the polymethoxy dimethyl ether.
In order to solve the technical problems, the invention provides the following technical scheme:
a process for separating reaction liquid of polymethoxy dimethyl ether comprises the following steps:
methylal and high-concentration formaldehyde react on a solid acid cation resin catalyst to obtain reaction liquid, and the reaction liquid is separated by a light component removing tower, a dehydration tower and an aldehyde removing tower to obtain dmmn (a product with n being 2-8).
1) The reaction liquid from the reaction system enters a light component removal tower, methylal and methanol which do not participate in the reaction are extracted from the top of the tower and sent back to a reactor to continue to participate in the reaction, the material in the tower kettle is pumped into the middle of a dehydration tower, the light component removal tower is a packed tower or a plate tower, and the number of theoretical plates is 20-50; the tower has the operation pressure of 0.1-0.2 Mpa and the operation temperature of 40-130 ℃; the reflux ratio is 0.5-4;
2) separating the moisture generated by the reaction system and the moisture brought by the raw materials in a dehydration tower, wherein the dehydration tower is a packed tower or a plate tower, and the number of theoretical plates is 10-40; the tower has the operation pressure of 0.01-0.2 MPa and the operation temperature of 80-110 ℃;
3) preheating the reaction liquid subjected to methylal and water removal by a preheater to 140-160 ℃, and then feeding the reaction liquid into an aldehyde removing tower, wherein the aldehyde removing tower is a plate tower, a circulating pump is arranged to extract materials on partial tower plates in the tower, the materials are superheated by the heater and then are back-mixed to an upper plate, and the materials are separated after formaldehyde and formic acid are removed in the aldehyde removing tower to obtain a dmmn product, wherein n is 2-8.
Furthermore, the number of theoretical plates of the aldehyde removal tower is 40-60; the reflux ratio is 0.8-8.
Furthermore, the pressure in the tower is regulated to 0.5-1Mpa by a pressure control valve at the top of the tower, the operation temperature of the tower kettle is 170-200 ℃, and the operation temperature at the top of the tower is 100-140 ℃. The aldehyde removing tower adopts an operation mode of pressure control, the boiling point of the material is increased, the temperature is raised to be higher than the critical temperature (140 ℃) of formaldehyde, and the formaldehyde can not be liquefied.
Further, the materials of the lower layer tower plate above 2 are mixed back to the upper layer plate.
Furthermore, the material at the position of the inner tower plate 19 is extracted by the circulating pump and is overheated by the plate superheater, and then is sent to the position of the inner tower plate 17, the material at the position of the inner tower plate 25 is extracted by the circulating pump and is overheated by the plate superheater, and then is sent to the position of the inner tower plate 23, and the material at the position of the inner tower plate 32 is extracted by the circulating pump and is overheated by the plate superheater, and then is sent to the position of the inner tower plate 30.
Further, the superheater is a plate superheater, the heat exchange area is 10-25 square meters, and the heating medium is 0.5-1.0 Mpa steam.
Further, a reboiler is arranged at the bottom of the aldehyde removing tower. The reboiler adopts the mode of forced circulation, and if the local temperature is too high, the formaldehyde is easy to carry out disproportionation reaction to generate formic acid. Forced circulation can effectively reduce the retention time of the materials in an extreme high-temperature area.
The method firstly separates formic acid and water in reaction liquid, plays a good role in inhibiting the subsequent reaction of formaldehyde disproportionation into acid, adopts a plate-type aldehyde removing tower as a plate-type tower, adopts a circulating pump to extract materials of partial tower plates in the tower, and mixes the materials back to an upper plate after being overheated by a heater, namely, the number of the tower plates at the high-temperature section of the tower is increased, thereby being beneficial to the vaporization separation of heat-sensitive formaldehyde, and the heating of the superheater can accelerate the thermal decomposition of unstable hemiacetal (hemiacetal is in the form of unstable formaldehyde), thereby solving the problems that the prior simple distillation process generates a large amount of formic acid through the thermal disproportionation reaction of formaldehyde, and the separation of formic acid decomposition products cannot be carried out. The dmmn, n-2-8 component can be selectively obtained by matching with the separation process of the previous stage. And the formaldehyde content and the formic acid content in the tower kettle can be almost not detected. Obtaining high-quality products. The invention has simple and efficient process and greatly reduces the investment cost.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic structural diagram of an aldehyde removal column in an embodiment of the invention, wherein 1 is a top pressure control valve, 2 is a preheater, 3 is a superheater, 4 is a circulating pump, 5 is a bottom discharge pump, and 6 is a reboiler.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Examples
A process for separating reaction liquid of polymethoxy dimethyl ether comprises the following steps:
methylal and high-concentration formaldehyde react on a solid acid cation resin catalyst to obtain reaction liquid, and the reaction liquid is separated by a light component removing tower, a dehydration tower and an aldehyde removing tower to obtain dmmn (a product with n being 2-8).
1) The reaction liquid from the reaction system enters a light component removal tower, methylal and methanol which do not participate in the reaction are extracted from the top of the tower and sent back to a reactor to continue to participate in the reaction, the material in the tower kettle is pumped into the middle of a dehydration tower, the light component removal tower is a packed tower or a plate tower, and the number of theoretical plates is 20-50; the tower has the operation pressure of 0.1-0.2 Mpa and the operation temperature of 40-130 ℃; the reflux ratio is 0.5-4; the reaction liquid (40-60% of methylal, 2-15% of methanol, 5-8% of formaldehyde, 1-3% of water and the balance of the product dmm2-8) fed into the light component removal tower has the lowest boiling point of methylal in the composition, only 42 ℃, and the methylal in the composition is distilled out from the top of the tower and continuously participates in the reaction;
2) separating the moisture generated by the reaction system and the moisture brought by the raw materials in a dehydration tower, wherein the dehydration tower is a packed tower or a plate tower, and the number of theoretical plates is 10-40; the tower has the operation pressure of 0.01-0.2 MPa and the operation temperature of 80-110 ℃; and pumping the tower kettle material of the light component removal tower into the middle part of the dehydration tower to realize the separation of the moisture generated by the reaction system and the moisture brought by the raw materials. The small amount of water (2-4%) contained in the bottom of the light component removal tower is decompressed in the dehydration tower to remove residual water (0.2-1%).
3) And preheating the reaction liquid subjected to methylal and water removal to 140-160 ℃ by a preheater 2, then feeding the reaction liquid into an aldehyde removal tower, wherein the aldehyde removal tower is a plate tower, a circulating pump is arranged to extract materials on partial tower plates in the tower, the materials are superheated by the heater and then are back-mixed to an upper plate, and the materials are separated after formaldehyde and formic acid are removed in the aldehyde removal tower to obtain a dmmn product, wherein n is 2-8. The overhead reflux (stream 2) is methylal with a content of 90 to 99%. Qualified products are extracted by a tower bottom discharge pump. The light components of methylal and formaldehyde are extracted from the top of the tower and sent to a reaction system.
The number of theoretical plates of the aldehyde removal tower is 40-60; the reflux ratio is 0.8-8. The pressure in the tower is adjusted to 0.5-1Mpa by a pressure control valve 1 at the top of the tower, the operation temperature of the tower kettle is 170-200 ℃, and the operation temperature at the top of the tower is 100-140 ℃. The aldehyde removing tower adopts an operation mode of pressure control, the boiling point of materials is improved, and the temperature is raised to be higher than the critical temperature (140 ℃) of formaldehyde, so that the formaldehyde cannot be liquefied. The top of the tower adopts methylal to reflux without condensation, and returns the methylal and formaldehyde to the reactor in a gas phase for further reaction.
The method comprises the steps of extracting materials at the position of a tower inner plate 19 through a circulating pump 4, overheating the materials through a plate superheater 3, conveying the materials to the position of a tower inner plate 17, extracting the materials at the position of a tower inner plate 25 through the circulating pump 4, overheating the materials through the plate superheater 3, conveying the materials to the position of a tower inner plate 23, extracting the materials at the position of a tower inner plate 32 through the circulating pump 4, overheating the materials through the plate superheater 3, and conveying the materials to the position of a tower inner plate 30. The temperature of the upper section of the tower is improved by realizing the back mixing of partial materials. Thereby promoting the formaldehyde to be separated cleanly in a reasonable temperature range. Meanwhile, due to the overheating effect of the plate-type superheater, the decomposition and vaporization of the formaldehyde dissolved in the material flow are accelerated.
The superheater 3 is a plate superheater, the heat exchange area is 10-25 square meters, and the heating medium is 0.5-1.0 Mpa steam.
The bottom of the dealdehyding tower is provided with a reboiler 6. The reboiler 6 adopts a forced circulation mode, and if the local temperature is too high, the formaldehyde is easy to generate formic acid through disproportionation reaction. Forced circulation can effectively reduce the retention time of the materials in an extreme high-temperature area.
Sampling the outlet of the circulating pump to test the formaldehyde content as follows:
| plate 19 | Plate 17 | Plate 25 | Plate 23 | Plate 32 | Plate 30 | |
| Formaldehyde w% | 1-3 | --- | 0.5-1 | --- | 0.01-0.05 | --- |
| Temperature of | 120-160 | 110-150 | 140-180 | 130-170 | 160-200 | 150-190 |
When dmmn (n ═ 3-8) product was obtained in the column. The operation pressure is 0.1-0.3Mpa, and the operation temperature is 140-. At this time, a large amount of M2 distilled out from the top of the column was returned to the reactor to continue the reaction.
Sampling the outlet of the circulating pump to test the formaldehyde content as follows:
| plate 19 | Plate 17 | Plate 25 | Plate 23 | Plate 32 | Plate 30 | |
| Formaldehyde w% | 1-3 | --- | 0.5-1 | --- | 0.01-0.05 | --- |
| Temperature of | 105-145 | 100-140 | 125-165 | 120-160 | 145-185 | 140-180 |
This column effectively removes formaldehyde, leaving the product dmmn (n ═ 2-8), and does not produce the formic acid decomposition product phenomenon. The operating parameters can be freely changed through the regulating valve at the tower top to realize the required product composition. The selection of whether to take dmm2 out as a product is based on the market and the business itself. Or dmm2 can be used as a reaction intermediate to continue the reaction back to the reactor.
In the process, the content of formaldehyde measured by a discharge pump 5 at the bottom of the tower is as follows:
| obtaining m2-8 | Obtaining m3-8 | Normal mode | |
| Content of Formaldehyde | <10ppm | Can not detect | 100-1000ppm |
The pumped product dmmn (n2-8) or dmmn (n ═ 3-8) is subjected to separation under reduced pressure in this column. The product is selectively separated as desired. Different separation conditions are selected according to the separation requirements.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A process for separating reaction liquid of polymethoxy dimethyl ether is characterized by comprising the following steps:
1) the reaction liquid from the reaction system enters a light component removal tower, methylal and methanol in the reaction liquid are extracted from the top of the tower and sent back to a reactor to continue to react, the material in the tower kettle is pumped into the middle of a dehydration tower, the light component removal tower is a packed tower or a plate tower, and the number of theoretical plates is 20-50; the tower has the operation pressure of 0.1-0.2 Mpa and the operation temperature of 40-130 ℃; the reflux ratio is 0.5-4;
2) separating the moisture generated by the reaction system and the moisture brought by the raw materials in a dehydration tower, wherein the dehydration tower is a packed tower or a plate tower, and the number of theoretical plates is 10-40; the tower has the operation pressure of 0.01-0.2 MPa and the operation temperature of 80-110 ℃;
3) preheating the reaction liquid subjected to methylal and water removal by a preheater to 140-160 ℃, and then feeding the reaction liquid into an aldehyde removing tower, wherein the aldehyde removing tower is a plate tower, a circulating pump is arranged to extract materials on partial tower plates in the tower, the materials are superheated by the heater and then are back-mixed to an upper plate, and the materials are separated after formaldehyde and formic acid are removed in the aldehyde removing tower to obtain a dmmn product, wherein n is 2-8.
2. The process for separating a reaction liquid of polymethoxy dimethyl ether according to claim 1, wherein the number of theoretical plates of the aldehyde removal column is 40 to 60; the reflux ratio is 0.8-8.
3. The process for separating a reaction solution of polymethoxy dimethyl ether according to claim 2, wherein the column internal pressure of the aldehyde-removing column is adjusted to 0.5 to 1MPa by a pressure control valve at the column top, the operating temperature at the column bottom is 170 to 200 ℃, and the operating temperature at the column top is 100 to 140 ℃.
4. The process for separating a reaction solution of polymethoxy dimethyl ether according to claim 2, wherein the material of the lower tray at 2 or more is backmixed to the upper tray.
5. The process for separating poly (methoxy-dimethyl ether) reaction liquid according to claim 4, wherein the material at the inner tower plate 19 is extracted by a circulating pump and superheated by a plate superheater, and then sent to the inner tower plate 17, the material at the inner tower plate 25 is extracted by a circulating pump and superheated by a plate superheater, and then sent to the inner tower plate 23, and the material at the inner tower plate 32 is extracted by a circulating pump and superheated by a plate superheater, and then sent to the inner tower plate 30.
6. The process for separating a reaction liquid of polymethoxy dimethyl ether according to claim 3, wherein the superheater is a plate superheater having a heat exchange area of 10 to 25 square meters and a heating medium of 0.5 to 1.0MPa of steam.
7. The process for separating a reaction solution of polymethoxy dimethyl ether according to claim 1, wherein a reboiler is provided at the bottom of the dealdehydizing column.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2015067610A (en) * | 2013-09-29 | 2015-04-13 | 蘇州奥索特新材料有限公司Ｓｕｚｈｏｕ ＯＳＴ Ａｄｖａｎｃｅｄ Ｍａｔｅｒｉａｌｓ Ｃｏ．， Ｌｔｄ． | Reaction system and method for producing polymethoxy dimethyl ether |
| CN105693479A (en) * | 2016-03-15 | 2016-06-22 | 江苏凯茂石化科技有限公司 | Process device special for preparing polyoxymethylene dimethyl ethers through formaldehyde gas |
| CN106365960A (en) * | 2016-10-12 | 2017-02-01 | 江苏凯茂石化科技有限公司 | Device and method for removing formaldehyde in polyoxymethylene dimethyl ethers |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015067610A (en) * | 2013-09-29 | 2015-04-13 | 蘇州奥索特新材料有限公司Ｓｕｚｈｏｕ ＯＳＴ Ａｄｖａｎｃｅｄ Ｍａｔｅｒｉａｌｓ Ｃｏ．， Ｌｔｄ． | Reaction system and method for producing polymethoxy dimethyl ether |
| CN105693479A (en) * | 2016-03-15 | 2016-06-22 | 江苏凯茂石化科技有限公司 | Process device special for preparing polyoxymethylene dimethyl ethers through formaldehyde gas |
| CN106365960A (en) * | 2016-10-12 | 2017-02-01 | 江苏凯茂石化科技有限公司 | Device and method for removing formaldehyde in polyoxymethylene dimethyl ethers |
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