CN108409568B - Process for preparing hydroxyalkyl (meth) acrylates - Google Patents
Process for preparing hydroxyalkyl (meth) acrylates Download PDFInfo
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Abstract
Disclosed is a method for preparing hydroxyalkyl (meth) acrylate, which comprises the steps of: adding (methyl) acrylic acid and alkylene oxide into a reactor for reaction to obtain reaction liquid; separating and purifying to obtain hydroxyalkyl (meth) acrylate; the method is characterized in that a catalyst and a polymerization inhibitor composition are added into (methyl) acrylic acid and alkylene oxide, the polymerization inhibitor composition comprises a polymerization inhibitor and polyolefinic amine, and the weight ratio of the polymerization inhibitor to the polyolefinic amine is 1: 1-1: 5, the weight average molecular weight of the polyolefinic amine is 250-150,000.
Description
Technical Field
The present invention relates to a process for preparing hydroxyalkyl (meth) acrylates. The method adopts an optimized separation process to purify the product, thereby obtaining the high-purity hydroxyalkyl (meth) acrylate. The method has the advantages of low content of byproducts, continuous production and higher production strength.
Background
The hydroxyalkyl (meth) acrylate is an important organic monomer, and has two active functional groups of carbon-carbon double bond and hydroxyl inside the molecule, so that the hydroxyalkyl (meth) acrylate is widely used for producing water-soluble resin, thermosetting (meth) acrylic resin and crosslinked resin to improve the heat resistance, wear resistance and water resistance of the product.
At present, the following batch processes are widely used in industry for producing hydroxyalkyl (meth) acrylates: under certain temperature and pressure, alkylene oxides such as ethylene oxide and propylene oxide are dripped into (methyl) acrylic acid in a batch reactor, and under the action of a catalyst, carbon-oxygen bonds of the ethylene oxide and the propylene oxide are broken and opened, so that the carbon-oxygen bonds of the ethylene oxide and the propylene oxide and the (methyl) acrylic acid undergo addition reaction to generate hydroxyalkyl (meth) acrylate; after the reaction is finished, the reaction liquid is sent into a film evaporator for separation after heat preservation for 0.5-1 h, and a hydroxyalkyl (meth) acrylate product with relatively high purity is obtained.
Hydroxyalkyl (meth) acrylates readily self-polymerize. Even in the case of a polymerization inhibitor, if the residence time at a high temperature is long, the self-polymerization phenomenon is very serious. As a result, the conventional rectification operation is difficult to be used for the separation and purification of hydroxyalkyl (meth) acrylate, and there are problems that the start cycle is short and the polymer is difficult to clean.
The hydroxyalkyl (meth) acrylate product in the current industrial production can only be purified by simple distillation through a thin film evaporator, and the hydroxyalkyl (meth) acrylate product with high purity is difficult to obtain.
CN 102584579B-CN 102584582B disclose production processes of hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate, which are basically the same and all adopt batch tank reactors. The method comprises the steps of firstly adding a certain amount of (methyl) acrylic acid, a catalyst and a polymerization inhibitor into a reaction kettle with a stirrer, introducing nitrogen to ensure the lower oxygen concentration in the kettle, dropwise adding excessive ethylene (propylene) oxide into the kettle at 80-85 ℃, and controlling the reaction temperature through cooling water. And (3) closing cooling water after the dripping of the ethylene oxide (propane) to naturally raise the temperature of the kettle, removing light components in vacuum after the temperature is reduced, and then carrying out reduced pressure distillation to obtain the hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate products.
CN104557540A discloses a continuous clean production process of hydroxyl acrylate, which comprises the steps of feeding acrylic acid and ethylene oxide dissolved with catalyst and polymerization inhibitor into a tubular reactor according to the proportion of 1: 1.1-1: 1.5, removing light in vacuum after the reaction is finished, recovering ethylene oxide, and continuously feeding the reaction liquid into an evaporator to obtain the final product.
CN105272851A discloses a method for producing hydroxyethyl (meth) acrylate by adopting a process of combining a three-section tubular reactor and a tower reactor, wherein (meth) acrylic acid, a catalyst and a polymerization inhibitor are added from an inlet of a first-section reactor and sequentially pass through the three-section reactor, and ethylene oxide is divided into three parts which are respectively added into the three-section reactor. And (4) aging the reaction liquid flowing out of the third section of tubular reactor through a section of adiabatic tower reactor to obtain a product liquid.
The production methods of the hydroxyalkyl (meth) acrylate disclosed in CN 102584579B-CN 102584582B are all batch kettle type production, and the main problems of the production process are that: in the reaction process, the back mixing is serious, and the dropping speed of the ethylene oxide (propane) and the heat removal speed of circulating water are difficult to balance, so the production intensity of the kettle type production process is low, the retention time of materials in a reactor is longer, the side reactions are more, and the content of byproducts is higher. In addition, the simple distillation process does not yield a product of higher purity and better color.
Both the production process of hydroxyethyl acrylate disclosed in CN104557540A and the preparation method of hydroxyethyl (meth) acrylate disclosed in CN105272851A adopt tubular reactors, so that the temperature control in the reaction process is easier than that of a kettle reactor, the retention time of materials is relatively shortened, and continuous production can be realized.
In the process disclosed in CN104557540A, because of the low boiling point of ethylene oxide and the low amount of unreacted ethylene oxide, the vacuum distillation needs cryogenic process to recover ethylene oxide, and the cryogenic process has low economic efficiency compared with the amount of ethylene oxide recovered. Although the material retention time in the tubular reactor is too long, the conversion rate of the raw materials is favorably improved, but the side reactions are increased correspondingly, and the purity and the chromaticity of the product are difficult to ensure through simple distillation during the separation of reaction liquid.
The method disclosed in CN105272851A adopts a method of adding ethylene oxide in stages, which increases the number of meters and the complexity of control. The tower reactor is connected behind the tubular reactor in series, which not only increases the number of equipment, but also prolongs the retention time of materials, and is not beneficial to improving the selectivity of products.
Polyalkene amines are a class of compounds containing amine active groups and are widely used as solubilizing or detergent agents.
Lihao et al, "preparation and application of aminated polyolefins" (the university paper "modification, compounding and blending of polymeric materials" in Wuhan 10 months 2012) mention the use of aminated polyolefins as compatibilizers.
CN101130505a discloses a method for preparing polyolefinic amines and a composition containing the same, which comprises: contacting an olefin or polyolefin and an azo compound under free radical conditions to form a polyolefinic nitrile having an average molecular weight of at least 250, followed by reduction of the polyolefinic nitrile to the corresponding polyolefinic amine. The polyolefinic amines produced by the reaction may be included as detergents in compositions, such as fuel compositions, additive compositions, and/or carrier compositions.
There is a need in the art to find a method for preparing hydroxyalkyl (meth) acrylates of high purity by which hydroxyalkyl (meth) acrylates of high purity are obtained.
Disclosure of Invention
An object of the present invention is to provide a process for producing a hydroxyalkyl (meth) acrylate with high purity, by which a hydroxyalkyl (meth) acrylate with high purity can be obtained.
Accordingly, the present invention provides a method for preparing hydroxyalkyl (meth) acrylate, which comprises the steps of:
adding stoichiometric amount of (methyl) acrylic acid and alkylene oxide into a reactor for reaction to obtain reaction liquid;
separating and purifying to obtain hydroxyalkyl (meth) acrylate;
the method is characterized in that a catalyst and polymerization inhibitor composition is added into stoichiometric amount of (methyl) acrylic acid and alkylene oxide, the polymerization inhibitor composition comprises a polymerization inhibitor and polyolefinic amine, and the weight ratio of the polymerization inhibitor to the polyolefinic amine is 1: 1-1: 5, the weight average molecular weight of the polyolefinic amine is 250-150,000.
Drawings
The invention is further described below with reference to the accompanying drawings. In the drawings:
FIG. 1 shows a reaction system of a preferred embodiment of the present invention.
Detailed Description
The present invention relates to a process for producing hydroxyalkyl (meth) acrylates. The method comprises the step of adding stoichiometric amounts of (methyl) acrylic acid and alkylene oxide into a reactor for reaction to obtain a reaction liquid.
In the present invention, the term "hydroxyalkyl (meth) acrylate" means methacrylic acid C1-10Hydroxyalkyl esters and/or acrylic acid C1-10Hydroxyalkyl esters, preferably methylpropaneOlefine acid C1-8Hydroxyalkyl esters and/or acrylic acid C1-8Hydroxyalkyl esters, preferably methacrylic acid C1-6Hydroxyalkyl esters and/or acrylic acid C1-6Hydroxyalkyl esters, preferably methacrylic acid C1-4Hydroxyalkyl esters and/or acrylic acid C1-4A hydroxyalkyl ester.
Also, in the present invention, the term "(meth) acrylic acid" means acrylic acid and/or methacrylic acid. The term "alkylene oxide" means C1-10Alkylene oxides, preferably C1-8Alkylene oxides, preferably C1-6Alkylene oxides, preferably C1-4An alkylene oxide.
The method of the present invention for reacting by adding stoichiometric amounts of (meth) acrylic acid and alkylene oxide to a reactor is not particularly limited and may be a conventional method known in the art.
In one embodiment of the present invention, (meth) acrylic acid and alkylene oxide are fed to the reactor in a slight excess of (meth) acrylic acid to effect reaction. In one embodiment of the present invention, the ratio of alkanoic acid (mass ratio of alkylene oxide to (meth) acrylic acid) at the inlet of the tubular reactor is 0.80 to 1.00, preferably 0.85 to 0.99, and more preferably 0.90 to 0.98.
The reaction of (meth) acrylic acid and an alkylene oxide (e.g., ethylene oxide or propylene oxide) to synthesize hydroxyalkyl (meth) acrylate is a reaction having a strong exothermic effect. The inventor of the present invention has found that if the reaction heat cannot be removed in time, the reaction material stays longer at a higher temperature, which results in more byproducts of the reaction, i.e., diethylene (propylene) glycol (meth) acrylate and ethylene (propylene) glycol di (meth) acrylate. In order to overcome the defects of small heat removal rate, serious material back mixing and long retention time of a kettle type reactor, in one embodiment of the invention, the tubular reactor is adopted for carrying out the reaction, and consequently, reactants flow at a higher speed in the tube, so that the heat transfer process is enhanced and the retention time of the materials is shortened. Tubular reactors are characterized by a larger surface area for the same volume and thus a larger heat transfer area for the reactor.
Non-limiting examples of tubular reactors suitable for use in the process of the present invention are, for example, coil reactors, single pass tubular reactors, multi-pass tubular reactors, and the like.
The method also comprises a step of separating and purifying the reaction liquid to obtain the hydroxyalkyl (meth) acrylate. The separation and purification step of the invention not only uses a film evaporator adopted by the conventional method, but also uses one-stage or multi-stage rectifying tower.
In one embodiment of the invention, the separation and purification steps of the invention comprise the steps of removing catalyst from the reaction liquid by a first thin film evaporator, removing light components by a first rectifying tower, distilling the product by a second rectifying tower and the like to obtain high-purity hydroxyalkyl (meth) acrylate, and recovering hydroxyalkyl (meth) acrylate from the bottom material of the second rectifying tower 4 by a second thin film evaporator.
The method of the invention also comprises the step of adding a catalyst and polymerization inhibitor composition into the stoichiometric amount of (methyl) acrylic acid and alkylene oxide, wherein the polymerization inhibitor composition comprises a polymerization inhibitor and a polyolefin amine, and the weight ratio of the polymerization inhibitor to the polyolefin amine is 1: 1-1: 5, the weight average molecular weight of the polyolefinic amine is 250-150,000.
The catalyst is a conventional catalyst known in the art. In one embodiment of the invention, the catalyst is selected from organic or inorganic salts of chromium, in an amount of 0.2 to 1.5%, preferably 0.5 to 1.2%, more preferably 0.8 to 1.0% by mass of (meth) acrylic acid.
In one embodiment of the invention, the catalyst is selected from chromium acetate, chromium acrylate, chromium chloride or a mixture of two or more thereof in any proportion.
The polymerization inhibitors are conventional polymerization inhibitors known in the art. In one embodiment of the invention, the polymerization inhibitor is selected from the group consisting of 4-hydroxy-2, 2,6, 6-tetramethylpiperidinyloxy radical phosphite triester (ZJ701), tetramethylpiperidinyloxy radical phosphite triester (ZJ705), hydroquinone monomethyl ether (MQ); the amount of the polymerization inhibitor to be used is 0.05 to 0.5%, preferably 0.08 to 0.4%, more preferably 0.1 to 0.3% by mass of (meth) acrylic acid.
In one embodiment of the invention, the polymerization inhibitor is 4-hydroxy-2, 2,6, 6-tetramethylpiperidinyloxy radical phosphite triester (ZJ701) and/or tetramethylpiperidinyloxy radical phosphite triester (ZJ 705).
The invention adopts the polyolefin amine to improve the polymerization inhibition effect of the polymerization inhibitor, and the weight ratio of the polymerization inhibitor to the polyolefin amine is 1: 1-1: 5, preferably 1: 1.5-1: 4.5, preferably 1: 2-1: 4, more preferably 1: 2.5-1: 3.5.
the present invention uses polyalkene amines as additives which are compounded with conventional polymerization inhibitors, such as 4-hydroxy-2, 2,6, 6-tetramethylpiperidinyloxy free radical (ZJ701), tetramethylpiperidinyloxy free radical phosphite triester (ZJ705), hydroquinone monomethyl ether (MQ), to further improve the polymerization inhibiting effect of the polymerization inhibitor, to prevent the self-polymerization of hydroxyalkyl (meth) acrylate compounds, to improve or prevent the clogging of reaction and/or separation equipment.
In one embodiment of the invention, the polyalkene amine has a weight average molecular weight of 250 or more, preferably 250-150,000, more preferably 500-100,000, preferably 750-75,000, most preferably 1,000-50,000, preferably 1,250-10,000.
In one embodiment of the present invention, the polymerization inhibitor composition is added in an amount of 500-5000ppm, preferably 800-4000ppm, more preferably 1000-3000ppm, based on the weight of (meth) acrylic acid.
In the polymerization inhibitor composition of the present invention, the weight ratio of the polymerization inhibitor to the polyolefinic amine is 1: 1-1: 5, preferably 1: 1.5-1: 4.5, preferably 1: 2-1: 4, more preferably 1: 2.5-1: 3.5.
in a preferred embodiment of the present invention, the polyalkene amine is used in an amount of 500-5000ppm, preferably 800-4000ppm, more preferably 1000-3000ppm, based on the weight of (meth) acrylic acid.
The polymerization inhibitor composition of the present invention can be sufficiently dissolved in (meth) acrylic acid and alkylene oxide, and therefore, the method of addition is not particularly limited, and the polymerization inhibitor composition may be added directly or after being formulated into a certain concentration using (meth) acrylic acid as a solvent.
In one embodiment of the invention, the polyalkene amine is selected from the group consisting of poly C3-C20Alkylene amines, preferably poly-C3-C18Alkylene amines, preferably poly-C3-C16The alkylene amine, preferably poly C3-C14Alkylene amines, preferably poly C3-C10An olefin amine.
In one embodiment of the invention, the polyalkene amine is selected from the group consisting of poly C3-C20Monoolefinic amines, preferably poly C3-C18Monoolefinic amines, preferably poly C3-C16Monoolefinic amines, preferably poly C3-C14Monoolefinic amines, preferably poly C3-C10A mono-olefinic amine.
In a preferred embodiment of the present invention, the polyalkene amine is selected from the group consisting of polypropene amine, polybutene amine, polypentalene amine, polyisobutene amine, polypropene amine, polyhexene amine, polyheptaheptene amine, polyoctene amine, polynonalene amine, polydecene amine, polyundecene amine, polydodecene amine, polytridecyl amine, polyhexacene amine, polytetradecene amine, polypentadecene amine, polyheptadecacene amine, polynonadecene, polyoctadecene amine, polyeicosene amine, and mixed polyalkene amines formed from one or more of the above polyalkene amines.
The polyolefinic amines of the present invention are commercially available or can be prepared by methods known in the art.
In one embodiment of the invention, the polyolefinic amines are prepared by the following process: contacting an olefin or polyolefin with an azo compound in the presence of a catalyst in a molar ratio of azo compound to olefin or polyolefin double bonds of 1: 1-1: 200.
in one embodiment of the present invention, non-limiting examples of olefins in the polyolefinic amine production process are, for example, propylene, butene, pentene, isobutylene, styrene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, hexadecene, tetradecene, pentadecene, heptadecene, nonadecene, octadecene, 1-octadecene, eicosene, 1-docosene, 1-tetracosene, 1-hexacosene, 1-octacosene, 1-triacontene, or a mixed olefin of two or more of the foregoing olefins.
In one embodiment of the present invention, the polyolefin in the method for preparing polyolefinic amine is, for example, polypropylene, polybutene, polypentene, polyisobutylene, polystyrene, polyhexene, polyheptene, polyoctene, polynonacene, polydecene, polyundecene, polydodecene, polytridecene, polyhexadecene, polytetradecene, polypentadecene, polyheptadecene, polynonadecene, poly octadecene, polyeicosene, or a mixed polyolefin formed by one or more of the above polyolefins.
In a preferred embodiment of the present invention, non-limiting examples of the polyolefin in the method for producing a polyolefinic amine are, for example, an olefin blend of 1-octadecene/1-tetracosene, an olefin blend of 1-eicosene/1-docosene/1-tetracosene, and an olefin blend of 1-tetracosene/1-hexacosene/1-octacosene.
In one embodiment of the present invention, the azo compound in the process for producing a polyolefinic amine is selected from the group consisting of 2,2 ' -Azobisisobutyronitrile (AIBN), 2 ' -azobis (2-butyronitrile), 1 ' -azobis (cyclohexanecarbonitrile), 2- (tert-butylazo) -2-cyanopropane, 2 ' -azobis [ 2-methyl-N- (1, 1) -bis (hydroxymethyl) -2-hydroxyethyl ] propionamide, 2 ' -azobis (2-methyl-N-hydroxyethyl) propionamide, 2 ' -azobis (N, N ' -dimethyleneisobutyramidine) dichloride, 2 ' -azobis (2-amidinopropane) dichloride, 2 ' -azobis (N, n ' -dimethyleneisobutyramide), 2 ' -azobis (2-methyl-N- [1, 1-bis (hydroxymethyl) -2-hydroxyethyl ] propionamide), 2 ' -azobis (2-methyl-N- [1, 1-bis (hydroxymethyl) ethyl ] propionamide), 2 ' -azobis (2-methyl-N- (2-hydroxyethyl) propionamide), 2 ' -azobis (isobutyramide) dihydrate, azobisbutyronitrile, 2 ' -azobis- (4-methoxy-2, 4-dimethylvaleronitrile), 2 ' -azobis- (2-methylbutyronitrile), 2, 2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile) or a mixture of two or more thereof. In a preferred embodiment of the invention, the azo compound is selected from 2, 2' -Azobisisobutyronitrile (AIBN).
In one embodiment of the invention, the catalyst for the preparation of polyolefinic amines is selected from the group consisting of boranes, carboranes, fullerenes (fullerendes), metallocenes, and lithium-containing catalysts. In one embodiment of the invention, the lithium-containing catalyst is a weakly solvated lithium cation (e.g., LiCB)11(CH3)2。
In one embodiment of the invention, the polyolefinic amines are produced by the process described in CN 101130505A.
The invention utilizes the compounding action of the polyolefinic amine and the conventional polymerization inhibitor to more effectively prevent the (methyl) hydroxyalkyl acrylate from self-polymerization, thereby preventing the self-polymerization product of the (methyl) hydroxyalkyl acrylate from blocking equipment in the reaction process and the separation and purification process, favorably prolonging the maintenance period of a production device, improving the production efficiency and reducing the product cost.
FIG. 1 is a schematic diagram of a reaction system in one embodiment of the present invention. The reaction system shown in fig. 1 comprises a tubular reactor 1, a first thin film evaporator 2 in fluid connection with the tubular reactor 1 and a first rectification column 3 in fluid connection with the first thin film evaporator 2. The first rectification column 3 is fluidly connected at its bottom to the second rectification column 4 and at its top to the inlet of the tubular reactor 1. The bottom of the second rectification column 4 is in fluid connection with a second thin film evaporator 5.
When the method is used, the (methyl) acrylic acid, the alkylene oxide, the catalyst and the polymerization inhibitor composition are continuously added into a tubular reactor 1, reaction liquid obtained from the outlet of the tubular reactor 1 sequentially passes through the steps of removing the catalyst by a first film evaporator 2, removing light components by a first rectifying tower 3, separating products by a second rectifying tower 4 and the like to obtain the high-purity hydroxyalkyl (methyl) acrylate, and in order to improve the yield of the hydroxyalkyl (methyl) acrylate, tower bottom materials of the second rectifying tower 4 are sent into a second film evaporator 5 to recover the hydroxyalkyl (methyl) acrylate.
The outlet of the tubular reactor 1 contains, in addition to the product hydroxyalkyl (meth) acrylate, catalyst, inhibitor, polyalkene amine, unreacted (meth) acrylic acid, low amounts of by-products such as diethylene (propylene) glycol (meth) acrylate and ethylene (propylene) glycol di (meth) acrylate, and heavy components. Therefore, the outlet material of the tubular reactor 1 passes through the first thin film evaporator 2, the first rectifying tower 3, the second rectifying tower 4 and the second thin film evaporator 5 in turn, and the hydroxyalkyl (meth) acrylate product is obtained at the top of the second rectifying tower 4. Wherein, the material obtained from the top of the first rectifying tower 3 contains hydroxyalkyl (meth) acrylate and unreacted (meth) acrylic acid, and the material is recycled to the inlet of the reactor to recycle the unreacted (meth) acrylic acid, and simultaneously, fresh (meth) acrylic acid and ethylene oxide (propane) are diluted, thereby inhibiting the temperature of the reaction material from rising too fast.
In the disclosed production method for producing hydroxyalkyl (meth) acrylate by using a tank reactor or a tubular reactor, the excessive reaction material proportion of alkylene oxide is generally adopted, and after the reaction is finished, or light components such as unreacted ethylene oxide and the like are directly removed in vacuum, so that certain pollution to the environment is caused; or is uneconomical due to difficulty in recycling, so that the production cost is increased. Therefore, in the process of the present invention, the alkanoic acid ratio (mass ratio of alkylene oxide to (meth) acrylic acid, for example, the mass ratio of ethylene oxide (propane) to (meth) acrylic acid) at the inlet of the tubular reactor is a raw material ratio including recycled (meth) acrylic acid, and is 0.80 to 1.00, preferably 0.90 to 0.98.
In the method of the present invention, the operation temperature of the tubular reactor is preferably lower than the activation temperature of the reactant molecules and lower than the temperature at which the by-products are generated, and the range is 80 to 160 ℃, preferably 85 to 130 ℃. The operating pressure is determined in consideration of appropriate piping and equipment resistance without vaporization of alkylene oxide (e.g., ethylene (propylene) oxide) at the reaction temperature, and is 0.5 to 5.0MPa, preferably 2.0 to 4.5 MPa.
In one embodiment of the present invention, the boiling points of the diethylene glycol (meth) acrylate and ethylene (propylene) glycol di (meth) acrylate, which are byproducts of the hydroxyethyl (meth) acrylate synthesis reaction, are closer to the boiling point of the hydroxyethyl (meth) acrylate product, and the byproducts are not easily separated from the product even by rectification separation, so that it is better to avoid the generation of byproducts in a reaction stage.
The inventor of the present invention has found that, in the reaction of (meth) acrylic acid and ethylene oxide (propane) to synthesize hydroxyethyl (meth) acrylate, under proper temperature and in the presence of a catalyst, the (meth) acrylic acid and ethylene oxide (propane) can reach a high conversion rate relatively quickly, and the reaction to generate the byproducts such as diethylene (propylene) glycol (meth) acrylate and ethylene (propylene) glycol di (meth) acrylate is a series side reaction of a main reaction, and the rate of the main reaction is higher than that of the side reaction, and if the material stays for a long time under the reaction conditions, the byproducts will be generated more. Therefore, in the method of the present invention, the residence time of the material in the reactor is controlled to be 0.5 to 50min, preferably 5.0 to 30.0 min.
In addition, the reaction of (meth) acrylic acid and ethylene oxide (propane) to synthesize hydroxyethyl (meth) acrylate has a large thermal effect, if the reaction heat cannot be removed in time, the reaction temperature rise is too high, side reactions are more likely to occur, and even the reaction materials polymerize, so that the flow rate of the materials in the reaction tube is high, the heat transfer process is enhanced, and the tubular reactor used has a large specific surface area, therefore, the reaction tube is a stainless steel tube with a diameter of less than or equal to 25mm, preferably a stainless steel tube with a diameter of less than or equal to 15 mm.
To avoid continued promotion of the reaction by the catalyst during product separation and to avoid full recovery of the heavy components
The invention relates to a hydroxyalkyl (meth) acrylate product, which adopts a first thin film evaporator 2 to remove a catalyst in a reaction liquid at the beginning of a product separation stage and adopts a second thin film evaporator 5 to treat materials in a tower bottom of a second rectifying tower 4.
The thin film evaporator involved in the method is a universal thin film evaporator, wherein the operating pressure of the first thin film evaporator 2 is 0.4-5.0 kPaA, preferably 0.5-2.0 kPaA; the operation temperature is 80-140 ℃, and preferably 90-120 ℃. The second thin film evaporator 5 is operated at a pressure of 0.8 to 6.0kPa, preferably 1.0 to 3.0 kPa; the operation temperature is 120-160 ℃, preferably 125-150 ℃.
In view of the fact that simple distillation is difficult to obtain products with high purity and good chromaticity, the first rectifying tower 3 is adopted to remove light components, so that the acidity in the final product can be greatly reduced. The product is purified by the second rectifying tower 4, so that the purity and the chromaticity of the product are obviously improved. The rectifying tower related in the method is a macroporous flow-through sieve plate tower, materials at the top of the tower are cooled and condensed by adopting circulating water and (or) chilled water (liquid), wherein the operating pressure at the top of the first rectifying tower 3 is set to be 0.2-3.0 kPaA, and preferably 0.5-1.5 kPaA; the corresponding operating temperature is 75-120 ℃, preferably 85-110 ℃. The operation pressure at the top of the second rectifying tower 4 is set to 0.1 to 2.5kPa, preferably 0.2 to 1.5 kPa; the corresponding operating temperature is 70-120 ℃, preferably 80-110 ℃.
The rectification column is used in the separation process of the hydroxyalkyl (meth) acrylate, and can improve the product quality, but the hydroxyalkyl (meth) acrylate has a longer retention time in a higher temperature environment and is easily polymerized even if a polymerization inhibitor exists, so that the rectification column used for the separation of the hydroxyalkyl (meth) acrylate has a problem of a shorter start cycle. The inventor discovers through research that the polymerization tendency of hydroxyalkyl (meth) acrylate in the heat exchanger tubes and on the rectifying tower plates can be greatly delayed or prevented when the polyalkene amine and the conventional polymerization inhibitor are compounded in the rectifying process, so that the start cycle is prolonged.
In a preferred embodiment of the present invention, the process relates to a process for producing hydroxyethyl acrylate, which comprises, as shown in FIG. 1, feeding ethylene oxide, acrylic acid in which a polymerization inhibitor, a polyolefinic amine and a catalyst are dissolved, and a feed from the top of a first rectifying column 3 into a static mixer 6 to be mixed and then into a tubular reactor 1, wherein fresh ethylene oxide and acrylic acid are added in such amounts that the ratio of alkanoic acid at the inlet of the reactor 1 is 0.80 to 1.00 by weight. The material at the outlet of the tubular reactor 1 enters a first thin film evaporator 2 to remove the catalyst, then the material is sent to a first rectifying tower 3 to recover light components such as unreacted acrylic acid, the material containing the light components obtained at the top of the tower is circulated to the inlet of the tubular reactor 1, the material at the bottom of the tower is sent to a second rectifying tower 4, a high-purity hydroxyethyl acrylate product is obtained at the top of the second rectifying tower 4, and the material at the bottom of the second rectifying tower 4 is sent to a second thin film evaporator 5 to further recover the hydroxyethyl acrylate therein. In the rectifying operation process, a mixture of polymerization inhibitor and polyolefinic amines is continuously added into the feeding materials of the first rectifying tower 3 and the second rectifying tower 4.
In one embodiment of the invention, the mixer, the reactor, the thin film evaporator and the rectifying tower are all made of 316L. In one embodiment of the invention, the tubular reactor 1 is 6 tube passes, the reactor tube is 6; the diameter of the rectifying tower is DN150, and a flow-through sieve plate with the aperture of 2mm is arranged in the rectifying tower.
The present invention is further illustrated by the following examples.
Example 1
According to the flow of the attached figure 1, 0.08kg/h of chromium acetate, 0.03kg/h of ZJ705 and 0.03kg/h of polyacrylamide are dissolved in 15.05kg/h of acrylic acid, the solution, 8.88kg/h of ethylene oxide and circulating materials at the top of a first rectifying tower are mixed in a mixer and then are sent into a reactor (the ratio of the amount of actually consumed ethylene oxide to the amount of actually consumed acrylic acid is 0.968), the reaction temperature is controlled at 100 ℃, the inlet pressure of the reactor is 3.0MPa, and the residence time of the reaction materials in the reactor is 20 min. The operation pressure and the corresponding temperature of the separation equipment such as the first thin film evaporator, the first rectifying tower, the second rectifying tower and the second thin film evaporator are shown in table 1.
Table 1 example 1 operating pressure and operating temperature of the separation apparatus concerned
| Operating pressure (kPa) | Operating temperature (. degree.C.) | |
| First film evaporator | 1.0 | 101.3 |
| First rectifying tower | 0.8 | 87.4 |
| Second rectifying tower | 0.4 | 81.3 |
| Second film evaporator | 1.2 | 148.1 |
The reaction and isolation results are shown in table 2.
Table 2 reaction and isolation results of example 1
Note: in the table, AA-acrylic acid;
HEA-hydroxyethyl acrylate;
EGDA-ethylene glycol diacrylate;
DEGMA-diethylene glycol acrylate
Example 2 (comparative example)
The difference from example 1 was that the material at the top of the first rectifying column was not circulated, and the amount of acrylic acid added was 15.3kg/h (the ratio of the amounts of ethylene oxide and acrylic acid actually consumed was 0.95), and the other conditions were the same as in example 1. The reaction and isolation results are shown in table 3.
Table 3 reaction and isolation results of example 2
Example 3 (comparative example)
0.08kg of chromium acetate and 0.03kg of ZJ705 were dissolved in 15.05kg of acrylic acid, the solution was added to a reaction kettle at one time, heated to 80-85 ℃, the air in the reaction kettle was replaced with nitrogen, and then 9.66kg of ethylene oxide (the ratio of the amount of ethylene oxide to the amount of acrylic acid actually consumed was 1.05) was added dropwise over 3 hours. In the dropping process, circulating water is introduced into the jacket of the reaction kettle to remove heat, and the reaction temperature is kept at about 85 ℃. After the dripping of the ethylene oxide is finished, the temperature is kept for 0.5 h. And a thin film evaporator is adopted to sequentially remove the catalyst, remove light and evaporate the product under the negative pressure state.
The reaction and isolation results are shown in table 4.
Table 4 reaction and isolation results of example 3
Example 4
1. Preparation of polymerization inhibitor composition
1 part by weight of ZJ705 and 3.3 parts by weight of polyisobutylene amine (PBA, weight average molecular weight 350, prepared by the method described in CN 101130505A) were added to one reaction vessel and mixed well to obtain a polymerization inhibitor composition.
2. Testing polymerization inhibition Properties
150g of hydroxyethyl acrylate having a purity of 95.6% was charged into a 500ml glass beaker, 15ppm of the above-mentioned polymerization inhibitor composition was added to the beaker, and after stirring and sufficient dissolution, the beaker was placed in an oil bath at 80 ℃ to observe the occurrence of a polymer (the time interval from the start of stirring to the occurrence of a polymer is referred to as an induction period), and after about 3 hours, the beaker was taken out and cooled, and then filtered through a 60-mesh stainless steel filter, and the polymer on the filter was collected and weighed.
The above experiments were repeated three times and the results are shown in table 5.
TABLE 5 inhibition of hydroxyethyl acrylate by the inhibitor composition of the present invention
Comparative example 1
1. Preparation of polymerization inhibitor composition
4.3 parts by weight of ZJ705 was charged into one reaction vessel to obtain a polymerization inhibitor composition.
2. Testing polymerization inhibition Properties
150g of hydroxyethyl acrylate having a purity of 95.6% was charged into a 500ml glass beaker, 15ppm of the above-mentioned polymerization inhibitor composition was added to the beaker, and after being sufficiently dissolved by stirring, the beaker was placed in an oil bath at 80 ℃ to observe the occurrence of a polymer (the time interval from the start of stirring to the occurrence of a polymer is referred to as an induction period), the polymer appeared after about 2 hours, and after 4 hours, the beaker was taken out and cooled, and then filtered with a 60-mesh stainless steel filter, and the polymer on the filter was collected and weighed.
The above experiments were repeated three times and the results are shown in table 6.
TABLE 6 inhibition of acrylic acid by conventional polymerization inhibitor compositions
As can be seen by comparing the test results in tables 5 and 6, the induction period of the hydroxyethyl acrylate material is significantly prolonged from about 2 hours to about 3 hours after the addition of the polyolefinic amine, the polymer quality is greatly reduced, and the polymerization inhibiting effect is significant.
Claims (18)
1. A method for preparing hydroxyalkyl (meth) acrylate, comprising the steps of:
adding (methyl) acrylic acid and alkylene oxide into a reactor for reaction to obtain reaction liquid;
separating and purifying to obtain hydroxyalkyl (meth) acrylate;
the method is characterized in that a catalyst and a polymerization inhibitor composition are added into (methyl) acrylic acid and alkylene oxide, the polymerization inhibitor composition comprises a polymerization inhibitor and polyolefinic amine, and the weight ratio of the polymerization inhibitor to the polyolefinic amine is 1: 1-1: 5, the weight average molecular weight of the polyolefinic amine is 250-150,000.
2. The method of claim 1, wherein the polyolefinic amine is selected from the group consisting of poly-C3-C20An olefin amine.
3. The method of claim 1, wherein the polyolefinic amine is selected from the group consisting of poly-C3-C18An olefin amine.
4. The method of claim 1, wherein the polyolefinic amine is selected from the group consisting of poly-C3-C16An olefin amine.
5. The method of claim 1, wherein the polyolefinic amine is selected from the group consisting of poly-C3-C14An olefin amine.
6. The method of claim 1, wherein the polyolefinic amine is selected from the group consisting of poly-C3-C10An olefin amine.
7. The method of claim 1, wherein the polyalkene amine is selected from the group consisting of polyallylamine, polybutene amine, polypentaenamine, polyisobutene amine, polyallylamine, polyhexene, polyheptaheptene amine, polyoctenylamine, polynonalene amine, polydecene amine, polyundecene amine, polydodecene, polytridecyl enamine, polyhexacene amine, polytetradecene amine, polypentadecene amine, polyheptadecene amine, polynonadecene amine, polyoctadecene amine, polyeicosene amine, and mixtures of polyalkene amines.
8. The method as claimed in any of claims 1 to 7, characterized in that the method uses a system comprising a tubular reactor (1), a first thin-film evaporator (2) in fluid connection with the tubular reactor (1) and a first rectification column (3) in fluid connection with the first thin-film evaporator (2), the first rectification column (3) being in fluid connection at its bottom with a second rectification column (4) and at its top with the inlet of the tubular reactor (1), the second rectification column (4) being in fluid connection at its bottom with a second thin-film evaporator (5).
9. The method of claim 8, wherein the (meth) acrylic acid and the alkylene oxide are fed into the tubular reactor (1) in such a manner that the (meth) acrylic acid is in excess, the reaction solution is subjected to catalyst removal by a first thin film evaporator (2), light components removal by a first rectifying column (3), product distillation by a second rectifying column (4) to obtain hydroxyalkyl (meth) acrylate, and the hydroxyalkyl (meth) acrylate in the residue from the second rectifying column (4) is recovered by a second thin film evaporator (5).
10. The process according to claim 8, characterized in that the tubular reactor (1) is selected from a coil-and-tube reactor, a single-pass shell-and-tube reactor or a multi-pass shell-and-tube reactor.
11. The process according to claim 8, characterized in that the tubular reactor has a tube diameter of 25mm or less; the mass ratio of the alkylene oxide to the (meth) acrylic acid is 0.80 to 1.00.
12. The process according to claim 8, characterized in that the tubular reactor has a tube diameter of 15mm or less; the mass ratio of the alkylene oxide to the (meth) acrylic acid is 0.90 to 0.98.
13. The method according to claim 8, wherein the tubular reactor is operated at a temperature of 80 to 160 ℃; the operating pressure is 0.5-5.0 MPa; the retention time of the materials is 0.5-50 min.
14. The method according to claim 8, wherein the tubular reactor is operated at a temperature of 85 to 130 ℃; the operating pressure is 2.0-4.5 MPa; the retention time of the materials is 5.0-30.0 min.
15. The method of claim 8, wherein the first thin film evaporator is operated at a pressure of from 0.4 to 5.0 kPa; the operation temperature is 80-140 ℃; the tower top operating pressure of the first rectifying tower is 0.2-3.0 kPa; the operation temperature is 75-120 ℃.
16. The method of claim 8, wherein the first thin film evaporator is operated at a pressure of from 0.5 to 2.0 kPa; the operation temperature is 90-120 ℃; the tower top operating pressure of the first rectifying tower is 0.5-1.5 kPa; the operation temperature is 85-110 ℃.
17. The method according to claim 8, wherein the operating pressure at the top of the second rectifying tower is 0.1-2.5 kPa; the operation temperature is 70-120 ℃; the distillate at the top of the first rectifying tower is recycled to the inlet of the reactor.
18. The method according to claim 8, wherein the operating pressure at the top of the second rectifying tower is 0.2-1.5 kPa; the operation temperature is 80-110 ℃; the distillate at the top of the first rectifying tower is recycled to the inlet of the reactor.
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