CN111807934B - Preparation method of electronic-grade propylene glycol monomethyl ether and product obtained by preparation method - Google Patents
Preparation method of electronic-grade propylene glycol monomethyl ether and product obtained by preparation method Download PDFInfo
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Abstract
The invention discloses a preparation method of electronic-grade propylene glycol monomethyl ether and an obtained product thereof, belonging to the technical field of fine chemical product preparation. The method comprises the following steps: 1) mixing methanol, propylene oxide and an alkaline ionic liquid catalyst, and reacting in a microchannel reactor to obtain a reaction solution; 2) removing light from the reaction solution to obtain a light-removed reaction solution; 3) evaporating the light component removal reaction liquid obtained in the step 2), and performing negative pressure rectification on the obtained steam to obtain electronic grade propylene glycol monomethyl ether. The preparation method provided by the invention has the advantages of mild reaction conditions, high purity of the prepared product, high yield, and high activity and selectivity of the catalyst.
Description
Technical Field
The invention relates to the technical field of fine chemicals preparation, in particular to a preparation method of electronic-grade propylene glycol monomethyl ether and an obtained product thereof.
Background
Propylene glycol monomethyl ether (PM) is a solvent with excellent performance and lower toxicity, and has the characteristics of strong dissolving capacity, low volatility, high flash point and the like. The electronic grade propylene glycol monomethyl ether is mainly used for TFT-LCD light resistance thinner, light resistance removing liquid, stripping agent, cleaning agent for IC, light resistance removing buffer, etching agent process and other chemical products needing special specification in the production process of liquid crystal display screen and photoresist. And is widely used as a solvent for producing electronic materials. The molecular structure and the physical and chemical properties of PM are similar to those of glycol ether, and the PM is considered to be an ideal substitute product of the glycol ether with higher toxicity. Propylene glycol monomethyl ether is gradually replacing ethylene glycol monomethyl ether with higher toxicity to become a solvent which is increasingly widely used, the annual demand is gradually increased, and the production, development and utilization prospects are very wide.
The common method for preparing propylene glycol monomethyl ether is Propylene Oxide (PO) method, i.e. PO and lower fatty alcohol react under the catalysis of acid or alkali to prepare the product. Due to the asymmetry of the propylene oxide, two isomers of primary ether and secondary ether can be obtained by the reaction, wherein the primary ether has low toxicity and good performance, and therefore, the higher the content of the primary ether in the product, the better the product. The traditional propylene glycol methyl ether production process takes liquid acid or alkali as a catalyst, has poor reaction selectivity and seriously corrodes equipment. Recently reported solid acid catalysts have the advantages of high activity, easy separation of the catalyst from products and the like, but generally require higher alcohol-alkyl ratio, have higher content of secondary ether isomers with higher product toxicity and higher content of non-alcohol ether impurities, thereby affecting the application performance of the solid acid catalysts. Meanwhile, the catalyst is complex to prepare and easy to coke and deactivate when in use. Although the solid base catalyst used for synthesizing propylene glycol methyl ether can overcome the defects of the solid acid catalyst, the activity of the solid base catalyst reported at present is generally low and the stability is poor. Propylene oxide and methanol can also react under the condition of no catalyst, but have the disadvantages of long reaction time, harsh reaction conditions (high temperature and high pressure), low selectivity of propylene glycol monomethyl ether and the like.
Disclosure of Invention
The invention provides a preparation method of electronic grade propylene glycol monomethyl ether and an obtained product thereof, aiming at the technical problems of harsh reaction conditions, low catalyst activity and selectivity and low product purity in the preparation of propylene glycol monomethyl ether in the background technology.
In order to solve the technical problem, the invention provides a preparation method of electronic grade propylene glycol monomethyl ether, which comprises the following steps:
1) mixing methanol, propylene oxide and an alkaline ionic liquid catalyst, and reacting in a microchannel reactor to obtain a reaction solution;
2) carrying out lightness removal on the reaction solution obtained in the step 1) to obtain lightness-removed reaction solution;
3) evaporating the light component removal reaction liquid obtained in the step 2), and performing negative pressure rectification on the obtained steam to obtain electronic grade propylene glycol monomethyl ether.
Preferably, the cation of the basic ionic liquid catalyst in step 1) is a 1, 3-dialkylimidazolium cation, an alkylimidazolium cation or an alkyl-substituted quaternary ammonium cation; the anion of the alkaline ionic liquid catalyst is hydroxide, carbonate, bicarbonate or acetate.
Preferably, the molar ratio of the methanol to the propylene oxide in the step 1) is (2-11): 1.
Preferably, the adding amount of the catalyst in the step 1) is 0.05-15% of the total weight of the methanol and the propylene oxide.
Preferably, in the step 1), the reaction pressure is 0.5-3Mpa, the reaction temperature is 70-140 ℃, and the reaction time is 3-6 min.
Preferably, the feeding rate of the microchannel reactor is 0.2-1 Kg/min.
Preferably, the light component is removed by adopting negative pressure rectification in the step 2), the vacuum degree during the negative pressure rectification is less than or equal to 5Kpa, and the temperature at the top of the tower is 90-120 ℃; the temperature of the tower kettle is 130-160 ℃.
Preferably, the temperature for evaporation in the step 3) is 115-150 ℃.
Preferably, the vacuum degree during negative pressure rectification in the step 3) is less than or equal to 5Kpa, and the tower top temperature is 110-130 ℃; the temperature of the tower kettle is 140-180 ℃.
The invention provides electronic-grade propylene glycol monomethyl ether prepared by the preparation method in the scheme.
Compared with the prior art, the invention has the following technical effects:
according to the invention, methanol, propylene oxide and an alkaline ionic liquid catalyst are reacted in the microchannel reactor, the efficient mass transfer effect of the microchannel reactor and the sufficient mixing of materials provide guarantee for the reaction of the methanol and the propylene oxide, the reaction time is greatly reduced, the raw materials are in a laminar flow state in the channel, the back mixing phenomenon does not exist, the contact chance of the propylene oxide with propylene glycol monomethyl ether and water is effectively avoided, the occurrence of series reaction is reduced, and the generation of secondary ether products is reduced, so that toxic byproducts are reduced, and the selectivity of primary ether is improved.
The invention adopts the alkaline ionic liquid catalyst, can provide Bronsted and Lewis alkaline centers at the same time, and has the high-density reaction activity of the traditional liquid alkali, stable solid alkali, easy separation, high catalytic efficiency and reusability. Meanwhile, the ionic liquid almost has no vapor pressure, is non-volatile and non-flammable, and cannot pollute the atmosphere. In addition, the Bronsted alkaline ionic liquid catalyst has the advantages of high active site density, uniform strength distribution, difficult loss of active sites and the like, methoxy anion is released in the catalytic process, the alcoholysis reaction is promoted, and the ionic liquid is more beneficial to the activation and ring opening of propylene oxide through the same ion effect and synergistic effect, so that the catalytic activity and selectivity are further improved.
The preparation method of the electronic-grade propylene glycol monomethyl ether provided by the invention takes the alkaline ionic liquid as the catalyst, can be well separated from reaction products after the reaction is finished, and has good stability to water, so that acid is not required to be added for neutralization. And the water content of the reaction materials is low, and no water is generated in the reaction process, so that azeotropic dehydration by adding a water-carrying agent is not needed, and the water content is less than 20ppm by rectification. After reaction in the microchannel reactor, the obtained reaction liquid is sequentially subjected to dealcoholization, evaporation and rectification refining, purification is performed step by step, and the process product is reasonably configured, so that the prepared propylene glycol monomethyl ether has high purity and high yield, and the problems of serious standard exceeding of the ion concentration of the product and the like do not exist.
Drawings
FIG. 1 is a schematic structural diagram of a production apparatus provided by the present invention;
wherein: 1-raw material mixer, 2-raw material preheater, 3-microchannel reactor, 4-dealcoholization tower, 5-thin film evaporator, 6-rectifying tower, 7-first condenser, 8-first reflux tank, 9-second condenser, 10-second reflux tank, 11-first reboiler, 12-second reboiler, 13-storage tank, 14-metering pump, 15-buffer tank, 16-third condenser and 17-catalyst circulation tank.
Detailed Description
The invention provides a preparation method of electronic-grade propylene glycol monomethyl ether, which comprises the following steps:
1) mixing methanol, propylene oxide and an alkaline ionic liquid catalyst, and reacting in a microchannel reactor to obtain a reaction solution;
2) carrying out lightness removal on the reaction solution obtained in the step 1) to obtain lightness-removed reaction solution;
3) evaporating the light component removal reaction liquid obtained in the step 2), and performing negative pressure rectification on the obtained steam to obtain electronic grade propylene glycol monomethyl ether.
The method mixes methanol, propylene oxide and an alkaline ionic liquid catalyst, and reacts in a microchannel reactor to obtain a reaction solution. In the present invention, the molar ratio of methanol to propylene oxide is preferably (2 to 11): 1, and more preferably 5: 1. In the present invention, the cation of the basic ionic liquid catalyst is preferably a 1, 3-dialkylimidazolium cation, an alkylimidazolium cation, or an alkyl-substituted quaternary ammonium cation; the anion of the basic ionic liquid catalyst is preferably hydroxide, carbonate, bicarbonate or acetate. In the present invention, the basic ionic liquid catalyst is more preferably 1-ethyl-3-methylimidazole hydroxide, 1-butyl-3-methylimidazole hydrogen carbonate, 1-butyl-3-methylimidazole carbonate or 1-butyl-3-methylimidazole acetate. In the invention, the addition amount of the catalyst is preferably 0.05-15% of the total weight of methanol and propylene oxide, and more preferably 3.5%. In the invention, the alkaline ionic liquid catalyst has high catalytic activity and catalytic selectivity, can be recycled, is easy to separate from reaction products, and is efficient, green and environment-friendly. This is because the key step of the conventional base-catalyzed mechanism is deprotonation of the alcohol by the action of a basic catalyst to form an electron donor alkoxide ion, which promotes the ring-opening addition of the epoxide. The basic ionic liquid catalyst provided by the invention has different action mechanism from the traditional basic catalyst on propylene glycol ether synthesis, and the imidazole cation of the imidazole basic ionic liquid catalyst has stronger hydrogen bond donor capacity, so that five-membered ring hydrogen bond clusters are easier to form, and the generation of a target product primary ether is more facilitated, thereby having higher selectivity. Meanwhile, the ionic liquid almost has no vapor pressure, is non-volatile, cannot pollute the atmosphere, is easy to separate from reactants and reaction products, and realizes cyclic utilization.
In the invention, the reaction pressure during the reaction in the microchannel reactor is preferably 0.5-3Mpa, and more preferably 1 Mpa; the reaction temperature is preferably 70-140 ℃, and more preferably 100-120 ℃; the reaction time is preferably 1-20 min, and more preferably 3-6 min. In the invention, the feeding rate of the microchannel reactor is preferably 0.2-1 Kg/min. In the present invention, the microchannel reactor is preferably a corrugated plate type, single screw type, double screw type or horizontal bar type static mixer. In the invention, the material of the microchannel reactor is preferably stainless steel, hastelloy or silicon carbide.
According to the invention, methanol, propylene oxide and a catalyst are reacted in the microchannel reactor, the efficient mass transfer effect of the microchannel reactor and the sufficient mixing of materials provide guarantee for the reaction of the methanol and the propylene oxide, the reaction time is greatly reduced, the raw materials are in a laminar flow state in the channel, the back mixing phenomenon does not exist, the contact chance of the propylene oxide with propylene glycol monomethyl ether and water is effectively avoided, the occurrence of series reaction is reduced, and the selectivity of the propylene glycol monomethyl ether is effectively improved.
After the reaction liquid is obtained, the invention carries out lightness removal on the reaction liquid to obtain lightness-removed reaction liquid. In the present invention, the light ends are preferably removed by negative pressure distillation. The vacuum degree during negative pressure rectification is preferably less than or equal to 5Kpa, and more preferably 2 Kpa. The tower top temperature is preferably 90-120 ℃, and more preferably 100-110 ℃; the temperature of the tower kettle is preferably 130-160 ℃, and more preferably 140-150 ℃. In the invention, the dealcoholization tower is preferably used for removing light by negative pressure rectification.
After the lightness-removed reaction solution is obtained, the invention evaporates the lightness-removed reaction solution, and carries out negative pressure rectification on the obtained steam to obtain the electronic grade propylene glycol monomethyl ether. In the invention, the temperature during evaporation is 115-150 ℃, and more preferably 120-135 ℃. In the present invention, the evaporation is preferably performed by a thin film evaporator.
In the present invention, the degree of vacuum at the time of negative pressure rectification is preferably 5Kpa or less, more preferably 2 Kpa. The tower top temperature is preferably 110-130 ℃, and more preferably 115-120 ℃; the temperature of the tower kettle is preferably 140-180 ℃, and more preferably 155-165 ℃. In the present invention, it is preferable to carry out the dealcoholization by negative pressure rectification using a rectifying column.
The invention provides electronic-grade propylene glycol monomethyl ether prepared by the preparation method in the scheme. The electronic grade propylene glycol monomethyl ether provided by the invention has metal ions such as sodium, potassium, calcium, magnesium, lead, zinc, iron and the like which are less than 5ppb, and has the moisture content of less than 20ppm, thus meeting the requirements of electronic grade chemicals.
The invention provides a preparation device of electronic grade propylene glycol monomethyl ether, which comprises a micro-channel reactor, a dealcoholization tower, a thin film evaporator and a rectifying tower, wherein the micro-channel reactor is connected with the dealcoholization tower; the microchannel reactor is connected with the dealcoholization tower through a discharge pipeline; the dealcoholization tower is sequentially connected with the thin film evaporator and the rectifying tower through a discharge pipeline of the tower kettle; a circulating pipeline of the dealcoholization tower is connected with the microchannel reactor; the circulating pipeline of the rectifying tower is connected with the dealcoholization tower.
When the device works, raw materials of methanol, propylene oxide and a catalyst enter a microchannel reactor for reaction, the obtained reaction liquid enters a dealcoholization tower through a discharge pipeline for light component removal, and unreacted methanol and propylene oxide with lighter components return to the microchannel reactor through a circulating pipeline at the top of the dealcoholization tower; the crude propylene glycol monomethyl ether enters a thin film evaporator through a discharge pipeline of a tower kettle of a dealcoholization tower to be evaporated, steam in the thin film evaporator enters a rectifying tower through the discharge pipeline to be refined, the crude propylene glycol monomethyl ether with lighter components returns to the dealcoholization tower through a circulating pipeline at the top of the rectifying tower in the rectifying process, heavy component multi-condensed propylene glycol ether is obtained at the tower kettle of the rectifying tower, and electronic-grade propylene glycol monomethyl ether is obtained at the lateral line of the rectifying tower.
In order to enable the raw materials to react sufficiently, in the present invention, the microchannel reactor is preferably a static mixer of a corrugated plate type, a single screw type, a double screw type or a horizontal bar type. In the invention, the material of the microchannel reactor is preferably stainless steel, hastelloy or silicon carbide.
In order to maintain the heat balance in the tower, the invention preferably further comprises a first condenser and a second condenser; the first condenser is respectively connected with the dealcoholization tower and the microchannel reactor through a circulating pipeline; and the second condenser is respectively connected with the rectifying tower and the dealcoholization tower through a circulating pipeline.
In order to enable the reflux, the present invention preferably further comprises a first reflux tank and a second reflux tank; the first reflux tank is respectively connected with the dealcoholization tower and the first condenser through a circulating pipeline; and the second reflux tank is respectively connected with the rectifying tower and the second condenser through a circulating pipeline.
In order to maintain the heat balance in the column, it is preferable in the present invention to further include a first reboiler and a second reboiler; the first reboiler is connected with the dealcoholization tower through a discharge pipeline of a dealcoholization tower kettle; the second reboiler is connected with the rectifying tower through a discharge pipeline of the rectifying tower kettle.
In order to facilitate the storage of the multi-propylene glycol ether obtained at the bottom of the rectifying tower, the invention preferably further comprises a storage tank, and the storage tank is connected with a discharge pipeline of the bottom of the rectifying tower.
In order to shorten the reaction time in the microchannel reactor, it is preferable in the present invention to further include a raw material preheater which is connected to the microchannel reactor through a discharge line.
In order to fully perform the reaction, the invention preferably further comprises a raw material mixer, and the raw material mixer is connected with the raw material preheater through a discharge pipeline.
In order to receive the electronic-grade propylene glycol monomethyl ether, the invention preferably further comprises a buffer tank which is connected with the rectifying tower through a side line discharge pipeline of the rectifying tower.
In order to facilitate cooling of the electronic grade propylene glycol monomethyl ether, it is preferred in the present invention that a third condenser is further included, which is connected to the buffer tank via a discharge line.
In order to facilitate the recovery of the catalyst, it is preferable in the present invention to further include a catalyst circulation tank connected to the thin film evaporator through a discharge line.
In order to facilitate the transportation of the raw materials and the reaction products, in the present invention, it is preferable that transportation pumps are respectively provided on the feeding pipeline, the discharging pipeline and the circulating pipeline of each section connected with the microchannel reactor, the dealcoholization tower, the thin film evaporator, the rectifying tower, the first reflux tank, the second reflux tank, the first reboiler, the second reboiler, the raw material preheater and the raw material mixer.
In order to further illustrate the present invention, the following embodiments are described in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
Respectively injecting propylene oxide, methanol and alkaline ionic liquid catalyst (1-butyl-3-methylimidazole bicarbonate) into a raw material mixer through a metering pump (the feed rate of propylene oxide is 14Kg/h, the feed rate of methanol is 23Kg/h, and the addition of the alkaline ionic liquid catalyst is 0.5 percent of the mass of the raw material), mixing multiple raw materials through the raw material mixer, then entering a raw material preheater, preheating the raw material to 50 ℃ by the raw material preheater, then entering a microchannel reactor for reaction (controlling the temperature in the microchannel reactor to be 100 ℃, the pressure to be 0.3MPa and the retention time of the material to be 6 min), detecting and analyzing a reaction liquid by using a gas chromatograph (under a selected chromatographic condition, gasifying a sample, passing through a chromatographic column, separating all components in the sample, detecting by using a hydrogen flame detector, calculating the contents of propylene oxide, propylene glycol monomethyl ether and an isomer by an area normalization method, methanol content calculated by external standard method), the conversion rate of propylene oxide is more than 85 percent, and the isomer selectivity is more than 70 percent.
Transferring the obtained reaction liquid into a dealcoholization tower for light component removal (controlling the vacuum degree of the dealcoholization tower to be less than or equal to 5KPa, the temperature of the top of the tower to be 90-120 ℃, the temperature of the bottom of the tower to be 130-160 ℃, and the reflux ratio to be 5), condensing unreacted methanol and propylene oxide at the top of the tower, returning the unreacted methanol and propylene oxide to a microchannel reactor, and feeding the crude propylene glycol monomethyl ether as a material at the bottom of the tower into a film evaporator.
And (2) conveying the crude propylene glycol methyl ether from the tower bottom of the dealcoholization tower to a thin film evaporator by a conveying pump, controlling the temperature of the thin film evaporator to be 115-130 ℃, directly feeding steam to a subsequent rectifying tower, controlling the concentration of the catalyst to be 50-60% by performing gas chromatography analysis on the residual liquid in the thin film evaporator by fixed-point sampling, and returning the residual liquid to a synthetic catalyst circulating tank.
After steam enters a rectifying tower, (the vacuum degree of the rectifying tower is controlled to be less than or equal to 5KPa, the temperature of the top of the tower is controlled to be 110-130 ℃, and the temperature of a kettle of the tower is controlled to be 140-180 ℃), a light-component-containing propylene glycol monomethyl ether crude product obtained at the top of the tower returns to a dealcoholization tower, the recombination obtained at the kettle of the tower is sent to a multi-propylene glycol ether recovery device, an electronic-grade propylene glycol monomethyl ether product is extracted at the side line, the product purity is 99.9%, the product chromaticity is 15, the metal ion content is 10 ppb.
The purity detection method comprises the following steps: by gas chromatography, under selected chromatographic conditions, a sample is vaporized through a chromatographic column to separate the components therein. Detecting by a hydrogen flame detector, and calculating the contents of propylene glycol monomethyl ether and isomers by an area normalization method according to the chromatographic peak areas of the components.
Chroma: the measurement is carried out by adopting a platinum-cobalt colorimetric method.
Content of metal ions: graphite furnace atomic absorption spectrophotometry is adopted.
Moisture content: the measurement was carried out by the Karl Fischer volumetric method.
Example 2
Propylene oxide, methanol and an alkaline ionic liquid catalyst (1-butyl-3-methylimidazole hydroxide) are respectively injected into a raw material mixer through a metering pump (the feeding amount of the propylene oxide is 14Kg/h, the feeding amount of the methanol is 30Kg/h, and the adding amount of the alkaline ionic liquid catalyst is 1.5 percent of the mass of the raw material), a plurality of strands of raw materials are mixed by the raw material mixer and then enter a raw material preheater, the raw material preheater preheats the raw materials to 50 ℃ and then enters a microchannel reactor for full reaction (the temperature in the microchannel reactor is controlled to be 120 ℃, the pressure is controlled to be 0.2MPa, the retention time of the raw materials is 3 min), a reaction liquid is detected and analyzed by using a gas chromatograph, the PO conversion rate is more than 99 percent.
Transferring the obtained reaction liquid into a dealcoholization tower for light component removal (controlling the vacuum degree of the dealcoholization tower to be less than or equal to 5KPa, the temperature of the top of the tower to be 90-120 ℃, the temperature of the bottom of the tower to be 130-160 ℃, and the reflux ratio to be 5), condensing unreacted methanol and propylene oxide at the top of the tower, returning the unreacted methanol and propylene oxide to a microchannel reactor, and feeding the crude propylene glycol monomethyl ether as a material at the bottom of the tower into a film evaporator.
And (3) conveying the crude propylene glycol methyl ether from the bottom of the dealcoholization tower to a thin film evaporator by a conveying pump, controlling the temperature of the thin film evaporator to be 130-150 ℃, directly feeding steam to a subsequent rectifying tower, and returning the residual liquid in the thin film evaporator to a synthetic catalyst circulating tank, wherein the concentration of the catalyst is controlled to be 50-60 percent and the residual liquid is a solution containing an ionic liquid catalyst.
After steam enters a rectifying tower, (controlling the vacuum degree of the rectifying tower to be 2KPa, the temperature of the top of the tower to be 110-130 ℃ and the temperature of a kettle of the tower to be 140-180 ℃), returning a light-component-containing propylene glycol monomethyl ether crude product obtained at the top of the tower to a dealcoholization tower, sending a recombinant product obtained at the kettle of the tower to a condensed propylene glycol ether recovery device, extracting an electronic-grade propylene glycol monomethyl ether product from a side line, wherein the product purity is more than or equal to 99.99%, and the product chromaticity is less than or equal to; the metal ion content is less than or equal to 1ppb, and the water content is less than or equal to 20 ppm. The detection methods of purity, chromaticity, metal ion content and moisture content were the same as in example 1.
Example 3
Propylene oxide, methanol and an alkaline ionic liquid catalyst (1-butyl-3-methylimidazolium carbonate) are respectively injected into a raw material mixer through a metering pump (the feeding amount of the propylene oxide is 14Kg/h, the feeding amount of the methanol is 56Kg/h, and the adding amount of the alkaline ionic liquid catalyst is 3.5 percent of the raw material mass), a plurality of strands of raw materials are mixed by the raw material mixer and then enter a raw material buffer tank, the materials in the raw material buffer tank are preheated to 50 ℃ by a preheater and then enter a microchannel reactor for full reaction (the temperature in the microchannel reactor is controlled to be 140 ℃, the pressure is controlled to be 1MPa, and the retention time of the materials is 5 min), a reaction solution is detected and analyzed by using a gas chromatograph, the conversion rate of the propylene oxide is more than.
Transferring the obtained reaction liquid into a dealcoholization tower for light component removal (controlling the vacuum degree of the dealcoholization tower at 2KPa, the temperature of the top of the tower at 90-120 ℃, the temperature of a tower kettle at 130-160 ℃ and the reflux ratio at 5), condensing unreacted methanol and propylene oxide at the top of the tower, returning the condensed unreacted methanol and propylene oxide to a microchannel reactor, and feeding crude propylene glycol monomethyl ether as a material in the tower kettle into a film evaporator.
And (3) conveying the crude propylene glycol methyl ether from the bottom of the dealcoholization tower to a thin film evaporator by a conveying pump, controlling the temperature of the thin film evaporator to be 120-135 ℃, directly feeding steam to a subsequent rectifying tower, controlling the concentration of the catalyst in the residual liquid of the thin film evaporator to be 50-60% and returning the residual liquid to a synthetic catalyst circulating tank, wherein the concentration of the catalyst is controlled to be 50-60%.
After steam enters a rectifying tower, (the vacuum degree of the rectifying tower is controlled to be less than or equal to 5KPa, the temperature of the top of the tower is controlled to be 110-130 ℃, and the temperature of a kettle of the tower is controlled to be 140-180 ℃), a light-component-containing propylene glycol monomethyl ether crude product obtained at the top of the tower returns to a dealcoholization tower, the recombination obtained at the kettle of the tower is sent to a condensed propylene glycol ether recovery device, an electronic-grade propylene glycol monomethyl ether product is extracted at the side line, the product purity is 99.95, the metal ion content is 5ppb, and the. The detection methods of purity, chromaticity, metal ion content and moisture content were the same as in example 1.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (4)
1. The preparation method of the electronic grade propylene glycol monomethyl ether is characterized in that the adopted preparation device comprises a micro-channel reactor, a dealcoholization tower, a film evaporator, a rectifying tower and a catalyst circulating tank; the catalyst circulating tank is connected with the thin film evaporator through a discharge pipeline; the microchannel reactor is connected with the dealcoholization tower through a discharge pipeline; the dealcoholization tower is sequentially connected with the thin film evaporator and the rectifying tower through a discharge pipeline of the tower kettle; a circulating pipeline of the dealcoholization tower is connected with the microchannel reactor; a circulating pipeline of the rectifying tower is connected with the dealcoholization tower;
the preparation method comprises the following steps:
1) mixing methanol, propylene oxide and an alkaline ionic liquid catalyst, and reacting in a microchannel reactor to obtain a reaction solution;
2) the reaction liquid obtained in the step 1) enters a dealcoholization tower through a discharge pipeline for light component removal and light component removal, and unreacted methanol and propylene oxide with lighter components return to a microchannel reactor through a circulating pipeline at the top of the dealcoholization tower; the dealcoholization is carried out by adopting negative pressure rectification, wherein the vacuum degree during the negative pressure rectification is less than or equal to 5Kpa, and the temperature at the top of the tower is 90-120 ℃; the temperature of the tower kettle is 130-160 ℃;
3) step 2), the light component-removed reaction liquid obtained by light component removal enters a thin film evaporator through a discharge pipeline of a tower kettle of a dealcoholization tower to be evaporated, steam in the thin film evaporator enters a rectifying tower through a discharge pipeline to be rectified under negative pressure, a propylene glycol monomethyl ether crude product with light components returns to the dealcoholization tower through a circulating pipeline at the top of the rectifying tower in the rectifying process, heavy component multi-condensed propylene glycol ether is obtained at the tower kettle of the rectifying tower, and electronic grade propylene glycol monomethyl ether is obtained at the side line of the rectifying tower; the temperature in the evaporation in the step is 115-150 ℃, the vacuum degree in the negative pressure rectification is less than or equal to 5Kpa, and the temperature at the top of the tower is 110-130 ℃; the temperature of the tower kettle is 140 ℃ and 180 ℃;
the cation of the basic ionic liquid catalyst in the step 1) is a 1, 3-dialkyl imidazole cation; the anion of the basic ionic liquid catalyst is hydroxide, carbonate, bicarbonate or acetate; the adding amount of the catalyst in the step 1) is 0.05-15% of the total weight of the methanol and the propylene oxide.
2. The method according to claim 1, wherein the molar ratio of methanol to propylene oxide in step 1) is 2-11: 1.
3. The preparation method of claim 1, wherein the reaction pressure in the microchannel reactor in step 1) is 0.5 to 3Mpa, the reaction temperature is 70 to 140 ℃, and the reaction time is 3 to 6 min.
4. The process of claim 3 wherein the microchannel reactor is fed at a rate of 0.2 to 1 Kg/min.
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