Method for continuously producing (alkyl) acrylates

Abstract

The invention relates to the field of organic synthesis, and discloses a method for continuously preparing (alkyl) acrylate, which comprises the following steps: (1) mixing (alkyl) acrylic acid, alcohol and an optional polymerization inhibitor, and carrying out first-stage esterification reaction; (2) separating a water phase in a product of the first-stage esterification reaction, and carrying out a second-stage esterification reaction on the residual organic phase; (3) optionally, separating the water phase in the product of the previous stage of esterification reaction, and performing the Nth stage of esterification reaction on the residual organic phase, and repeating for many times, N being greater than or equal to 3; and (4) carrying out post-treatment on the second-stage esterification reaction product in the step (2) or the Nth-stage esterification reaction product in the step (3) to obtain purified (alkyl) acrylate. The continuous preparation of the (alkyl) acrylate can be realized, the reaction period is short, the process energy consumption, the discharge of three wastes and the self-polymerization risk of the (alkyl) acrylate are low, and the method has remarkable economic benefits and environmental protection advantages.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for continuously preparing (alkyl) acrylate. Background Art

[0002] (Meth) acrylate has active double bonds and is an important class of fine chemical products and polymer monomers. Its homopolymer or copolymer has the characteristics of water resistance, flexibility, hardness and impact resistance. It is often used as oil additives, adsorption resins, adhesives and internal plasticizers. It has a wide range of uses in the fields of coatings, oil additives, plastics, papermaking, leather and cosmetics. (Meth) acrylate is usually prepared by ester exchange or (meth) acrylic acid direct esterification. Compared with the ester exchange method, the reaction efficiency of direct esterification of (meth) acrylic acid with fatty alcohol is higher, that is, (meth) acrylic acid and higher fatty alcohol are esterified; to promote the reaction, water needs to be continuously removed. In the existing continuous production method of methacrylate, such as CN113416133A, a solid acid catalyst is filled in a distillation tower, and the reaction efficiency is improved by real-time in-situ removal of water. This method has high energy consumption. Although it can promote the forward progress of the esterification reaction to a certain extent, even if a large amount of inhibitor is used, the risk of self-polymerization of methacrylate is still high, affecting the yield of methacrylate. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of high energy consumption and high risk of self-polymerization in the prior art and to provide a method for continuously preparing (alkyl) acrylate.

[0004] In order to achieve the above object, the present invention provides a method for continuously preparing (alkyl) acrylate, which comprises:

[0005] (1) mixing (alkyl) acrylic acid, alcohol and optional inhibitor to carry out a first stage esterification reaction;

[0006] (2) separating the aqueous phase from the product of the first stage esterification reaction and subjecting the remaining organic phase to a second stage esterification reaction;

[0007] (3) Optionally, separating the aqueous phase from the product of the previous esterification reaction, and subjecting the remaining organic phase to the Nth esterification reaction, and repeating this process multiple times, N≥3;

[0008] (4) post-treating the second stage esterification reaction product of step (2) or the Nth stage esterification reaction product of step (3) to obtain a purified (alkyl) acrylate.

[0009] Through the above technical scheme, the present invention can realize the continuous preparation of (alkyl) acrylates with a short reaction cycle, low process energy consumption, three waste emissions and (alkyl) acrylic acid self-polymerization risk, and has significant economic benefits and environmental advantages. DETAILED DESCRIPTION

[0010] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0011] In the present invention, unless otherwise specified, the term "(alk)acrylic acid" refers to acrylic acid and / or alkacrylic acid; and "(alk)acrylate" refers to acrylate and / or alkacrylate.

[0012] The present invention provides a method for continuously preparing (alkyl) acrylate, characterized in that the method comprises:

[0013] (1) mixing (alkyl) acrylic acid, alcohol and optional inhibitor to carry out a first stage esterification reaction;

[0014] (2) separating the aqueous phase from the product of the first stage esterification reaction and subjecting the remaining organic phase to a second stage esterification reaction;

[0015] (3) Optionally, the (remaining) aqueous phase in the product of the previous esterification reaction is separated, and the remaining organic phase is subjected to an Nth esterification reaction, and this cycle is repeated multiple times, where N ≥ 3 (e.g., 3, 4, 5, 6, 7, 8, 9 or 10).

[0016] (4) post-treating the second stage esterification reaction product of step (2) or the Nth stage esterification reaction product of step (3) to obtain a purified (alkyl) acrylate.

[0017] According to the present invention, controlling the conversion rate of each stage of esterification reaction can more effectively promote the reaction and reduce the risk of self-polymerization. Preferably, the conversion rate of the first stage of esterification reaction is 40-98% based on alcoholic hydroxyl groups, and more preferably 70-94% (such as 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 92%, 93%, 94% or any value or range between the above values). In the present invention, the conversion rate of a certain stage of esterification reaction refers only to the conversion rate calculated based on alcoholic hydroxyl groups in that stage.

[0018] Preferably, the conversion rate of the second stage esterification reaction is 40-100%, more preferably 70-99.5%, based on the alcohol hydroxyl group.

[0019] Preferably, the conversion rate of the Nth stage esterification reaction is 40-100%, more preferably 70-99.5%, based on the alcohol hydroxyl group.

[0020] Preferably, the total conversion rate of each stage of esterification reaction is ≥99%, more preferably 99-99.9%.

[0021] Controlling the conversion rates of the first esterification reaction and the second esterification reaction in the manner described above can further promote the reaction (shorten the reaction cycle) and reduce the risk of self-polymerization.

[0022] According to the present invention, step (3) is a selective step, that is, it can be performed or not performed. According to the method of the present invention, the purpose of the present invention can be well achieved without performing step (3) and the equipment requirements are simpler and the energy consumption is lower. If the production conditions permit, step (3) can be performed according to the actual situation and the total number of stages (or the value of N) for the esterification reaction can be selected, so as to make full use of the equipment and further improve the production efficiency.

[0023] According to the present invention, the aqueous phase in the product can be separated by a method commonly used in the art, but preferably, in step (2) and / or step (3), the aqueous phase in the product of the esterification reaction is separated by distillation and / or liquid-liquid phase separation, and more preferably by at least one of distillation, flashing, stripping, sedimentation, decantation, coalescence and centrifugation.

[0024] According to a preferred embodiment of the present invention, in order to further improve production efficiency and reduce the risk of self-polymerization, each stage of esterification reaction is carried out under the flow of inert gas, and the ratio of the volume space velocity of the inert gas to the liquid hourly space velocity of the liquid raw material is: 0-1000, more preferably 10-250. More preferably, the volume space velocity of the inert gas is 3-500h -1 , more preferably 8-80h -1 , preferably 9-15h -1 The inert gas may be a common gas in the art that does not react with any raw material in the method of the present invention and is in a gaseous state under the esterification reaction conditions, for example, nitrogen and / or a rare gas. The preferred embodiment in which each stage of the esterification reaction is carried out under the flow of an inert gas is particularly suitable for a process in which the esterification reaction pressure is a positive pressure.

[0025] According to a preferred embodiment of the present invention, in order to further improve the conversion rate of the alcohol, the method further comprises: in step (2) and / or step (3), adding (alkyl) acrylic acid so that the molar ratio of each additional addition of (alkyl) acrylic acid in terms of carboxyl groups to the alcohol in terms of hydroxyl groups is 0.1-2, more preferably 0.1-0.5. In order to more effectively reduce the risk of self-polymerization, the method may further comprise: in step (2) and / or step (3), adding a polymerization inhibitor, the amount of the polymerization inhibitor added each time being 0.01-3% by weight of the total weight of the (alkyl) acrylic acid and the alcohol, more preferably 0.01-1% by weight, further preferably below 0.08% by weight, particularly preferably below 0.07% by weight.

[0026] According to the present invention, in step (1), the molar ratio of (alkyl) acrylic acid calculated as carboxyl groups to alcohol calculated as hydroxyl groups can be 0.1-2, preferably 0.8-1.1.

[0027] According to the present invention, the molar ratio of (alkyl) acrylic acid calculated as carboxyl groups to alcohol calculated as hydroxyl groups in the entire preparation process may be 1-4, preferably 1.05-1.5.

[0028] According to the present invention, the alkyl acrylic acid can be any of the various alkyl acrylic acids commonly used in the art that can be used to prepare alkyl acrylates. Preferably, the carbon number of the alkyl group in the alkyl acrylic acid is less than or equal to 8, preferably less than or equal to 4. More preferably, the alkyl group in the alkyl acrylic acid is methyl, ethyl or propyl. Further preferably, the alkyl acrylic acid is methacrylic acid.

[0029] According to the present invention, the alcohol may be any alcohol commonly used in the art for preparing alkyl acrylates. Preferably, the alcohol is a fatty alcohol having a normal pressure boiling point higher than 100° C. and being insoluble or slightly soluble in water. “Insoluble or slightly soluble in water” refers to an alcohol having a solubility of less than or equal to 1 g in 100 g of water at 20° C. More preferably, the alcohol is at least one of monohydric alcohols having a carbon number of 9 to 22, and further preferably at least one of n-decanol, n-undecanol, n-dodecanol, n-tetradecanol, n-hexadecanol, and n-octadecyl alcohol.

[0030] According to a preferred embodiment of the present invention, the amount of the polymerization inhibitor is 0.03-5% by weight of the total weight of the (alkyl) acrylic acid and the alcohol, more preferably below 0.2% by weight, and particularly preferably below 0.15% by weight. The present invention can also achieve higher production efficiency when the amount of the polymerization inhibitor is relatively low.

[0031] According to the present invention, the polymerization inhibitor may be a common polymerization inhibitor in the art, but preferably, the polymerization inhibitor is at least one of a phenolic polymerization inhibitor, a quinone polymerization inhibitor, an aromatic amine polymerization inhibitor and an inorganic salt polymerization inhibitor. The phenolic polymerization inhibitor may be at least one of hydroquinone, pyrogallol and p-tert-butylcatechol. The quinone polymerization inhibitor may be at least one of tetrachlorobenzoquinone, 1,4-naphthoquinone and the like. The aromatic amine polymerization inhibitor may be at least one of p-phenylenediamine, benzidine, diphenylamine and p-(methyl)aniline and the like. The inorganic salt polymerization inhibitor may be at least one of ferric chloride, cuprous oxide and the like.

[0032] According to the present invention, the conditions of each stage of esterification reaction can independently include: a temperature of 80-140° C., preferably a temperature of 90-130° C. More preferably, the temperature of the first stage of esterification reaction is 1-10° C. lower than that of the second stage of esterification reaction, particularly preferably 1-5° C. lower.

[0033] According to the present invention, the conditions of each stage of esterification reaction can also independently include: a pressure of 0-10 MPaG, preferably 0.002-2 MPaG. More preferably, the pressure of the first stage of esterification reaction is 0.2-1 MPaG less than the pressure of the second stage of esterification reaction, particularly preferably 0.35-0.85 MPaG less.

[0034] According to a preferred embodiment of the present invention, step (1), step (2) and step (N) are respectively carried out in separate reactors or separators, so that the preparation process can be carried out continuously. The reactor may be filled with a solid acid catalyst (such as an acidic resin), and the total liquid hourly space velocity (volume) of (alkyl) acrylic acid, alcohol and optional inhibitor may be 0.1-3h -1 , preferably 0.18-1h -1 More preferably, the difference between the liquid hourly space velocity of the latter esterification reaction (the liquid hourly space velocity of the additional reaction raw materials, such as the additional (alkyl) acrylic acid and the optional inhibitor) and the liquid hourly space velocity of the previous esterification reaction is 0-0.2h -1 , more preferably 0-0.11h -1 .

[0035] According to the present invention, the conditions of each stage of esterification reaction can be the same or different, but controlling the temperature, pressure and liquid hourly space velocity of the previous stage of esterification reaction and the subsequent stage of esterification reaction in the manner described above can further promote the reaction and reduce the risk of self-polymerization.

[0036] According to the present invention, in order to promote the reaction, the esterification reaction can be carried out in the presence of a catalyst, and the catalyst can be at least one of sulfuric acid, sulfonic acid catalyst, heteropoly acid catalyst and acidic resin, and the amount of the catalyst is 0.05-10 weight % of the total weight of (alkyl) acrylic acid and alcohol, and more preferably 0.3-3 weight %. The sulfonic acid catalyst can be at least one of p-toluenesulfonic acid and methanesulfonic acid. The heteropoly acid catalyst is a class of oxygen-containing polyacids composed of heteroatoms and multi-coordinate atoms through oxygen atom coordination bridging, and the heteropoly acid catalyst can be at least one of phosphotungstic acid, phosphotungstomolybdic acid and silicotungstic acid, etc. The acidic resin can release hydrogen ions, and the acidic resin can be a macroporous acidic resin, etc.

[0037] According to the present invention, in order to purify the esterification reaction product, step (4) may include the operation of removing the inhibitor, and the method of removing the inhibitor may be alkali washing or extraction. The alkali washing method may be: alkali washing with an alkali metal hydroxide solution (especially sodium hydroxide solution) with a concentration of 1-20wt%, and then treating with desalted water to neutrality.

[0038] Preferably, the inhibitor is removed by extraction. More preferably, the extractant used for extraction includes an alcohol-based extractant and / or a water-based extractant, and a water-based extractant is further preferred. Most preferably, the water content in the water-based extractant is 10-100% by weight, preferably 60-100% by weight, and the remainder is a hydrophilic monohydric alcohol and / or a hydrophilic polyhydric alcohol, such as methanol.

[0039] According to the present invention, in order to purify the esterification reaction product, step (4) may further include a decolorization step, which may be performed in a manner commonly used in the art, for example, using white clay for decolorization, which will not be described in detail herein.

[0040] According to the present invention, the method may further include step (5): further recovering (alkyl) acrylic acid from the aqueous phase obtained in step (2) and / or step (3), preferably extracting and recovering (alkyl) acrylic acid in the aqueous phase with an extractant. The recovery method may specifically include: mixing the extractant and the aqueous phase, extracting, and obtaining water and an organic phase containing (alkyl) acrylic acid after phase separation, wherein the extractant is at least one of the hydrophobic higher fatty alcohols (see 202210554398.8 for details). When the method as described above is adopted to recover (alkyl) acrylic acid, the operation is simple, the extraction rate of (alkyl) acrylic acid is high, and no additional polymerization inhibitor is required, which is environmentally friendly. The hydrophobic higher fatty alcohol is at least one of the monohydric fatty alcohols having a carbon number of 9-26, preferably at least one of the monohydric fatty alcohols having a carbon number of 9-16. More preferably, the hydrophobic higher fatty alcohol is at least one of (n-) decanol, (n-) undecanol, (n-) dodecanol, (n-) tridecanol and (n-) tetradecanol. According to a particularly preferred embodiment of the present invention, the extractant is dodecanol and the volume ratio of dodecanol to the aqueous phase is 2.8-3.2:1.

[0041] The present invention will be described in detail below through examples. In the following examples, the macroporous acidic resin is a commercially available macroporous sulfonic acidic resin; "room temperature" refers to 25°C; the temperature of the mixed raw materials after preheating is about 100°C;

[0042] The post-treatment includes: removing the polymerization inhibitor and decoloring in sequence, removing the polymerization inhibitor by alkali washing, and the alkali washing organic phase is operated by using a 5 weight percent sodium hydroxide aqueous solution; and the material after alkali washing is decolorized by using white clay.

[0043] The calculation method of alcohol conversion rate is as follows: the residual alcohol content in the reaction solution is obtained by gas chromatography detection, and then the amount of converted alcohol is obtained, and the ratio of the amount of alcohol initially input is the conversion rate.

[0044] Yield of dodecyl methacrylate = molar yield of dodecyl methacrylate / molar amount of alcohol initially fed × 100%.

[0045] Comparative Example 1

[0046] Methacrylic acid, dodecanol and hydroquinone were mixed in the following proportions: 766.55 g methacrylic acid, 1102.05 g 1-dodecanol and 2.65 g hydroquinone. The mixed raw materials were preheated and heated at a liquid hourly space velocity of 0.1 h -1 The fixed bed reactor filled with macroporous acidic resin was passed through. The center temperature of the fixed bed reactor was 111°C, the reaction pressure was 0.95 MPa, and nitrogen was co-flowed during the reaction. The nitrogen space velocity was 33.63 h -1; After the reaction liquid passes through the reactor, it is cooled to room temperature and centrifuged (2000rpm, 20min, the same below) to obtain an organic phase and an aqueous phase, wherein the amount of water in the aqueous phase is 86% of the amount of water generated, and the organic phase is post-treated to obtain dodecyl methacrylate. The final product is analyzed by gas chromatography, and the conversion rate of dodecyl alcohol is 98.99%, and the yield of dodecyl methacrylate is 94.75%. The residence time of the reaction liquid in the fixed bed reactor is 10h.

[0047] Comparative Example 2

[0048] Add 77.48g of methacrylic acid, 111.81g of 1-dodecanol and 0.28g of hydroquinone to the reaction bottle and mix them thoroughly, add 5g of macroporous acidic resin catalyst, pass N2 into the reaction solution and start heating, distill at normal pressure, heat the reaction solution to 100°C to start timing the esterification reaction, control the reaction temperature to 113°C, and use a water separator to continuously distill the water generated in the esterification reaction with methacrylic acid. After the reaction is carried out for 14h, the unreacted methacrylic acid is distilled out under reduced pressure, the catalyst is removed by filtration, and at 30°C, alkali washing is carried out with a sodium hydroxide solution with a concentration of 5wt%, and then treated with desalted water to neutrality, and vacuum distillation is carried out under a vacuum degree of 10kPa, and then decolorization is carried out using white clay to obtain lauryl methacrylate. The reaction solution is subjected to gas chromatography analysis, and the conversion rate of dodecanol is 98.01%.

[0049] Example 1

[0050] 571.98 g of methacrylic acid, 1179.03 g of 1-dodecanol and 1.22 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.1936 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 1.6 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 9.61 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 93.18%; 151.19g of methacrylic acid and 1.22g of hydroquinone were added to the organic phase, and after thorough mixing, the liquid hourly space velocity was 0.2581h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 113°C, the reaction pressure was 1.3 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 11.24 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 99.69%, and the yield of dodecyl methacrylate was 98.7%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 9.04h.

[0051] Example 2

[0052] 659.20 g of methacrylic acid, 1301.78 g of 1-dodecanol and 1.3 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.2582 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 0.68 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 14.98 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 87.61%; 30.57g of methacrylic acid and 1.3g of hydroquinone were added to the organic phase, and after thorough mixing, the mixture was heated to room temperature at a liquid hourly space velocity of 0.2582h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 113°C, the reaction pressure was 1.04 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 12.18 h -1 The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 98.54%, and the yield of dodecyl methacrylate was 98.17%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 7.75h.

[0053] Example 3

[0054] 708.52 g of methacrylic acid, 1301.78 g of 1-dodecanol and 1.3 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.2582 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 0.68 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 14.98 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 87.61%; 80.36g of methacrylic acid and 1.3g of hydroquinone were added to the organic phase, and after thorough mixing, the mixture was heated to room temperature at a liquid hourly space velocity of 0.2582h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 113°C, the reaction pressure was 1.2 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 10.75 h -1The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 99.04%, and the yield of dodecyl methacrylate was 98.85%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 7.75h.

[0055] Example 4

[0056] 633.34 g of methacrylic acid, 1301.78 g of 1-dodecanol and 1.3 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.2151 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 0.68 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 14.61 h -1 ; After the reaction solution passes through the reactor, it is cooled to room temperature and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol is 89.77%; 95.49g of methacrylic acid and 1.3g of hydroquinone are added to the organic phase, and after thorough mixing, the mixture is heated to room temperature at a liquid hourly space velocity of 0.2797h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 113°C, the reaction pressure was 1.49 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 10.47 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 99.33%, and the yield of dodecyl methacrylate was 99.12%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 8.22h.

[0057] Example 5

[0058] 633.34 g of methacrylic acid, 1301.78 g of 1-dodecanol and 1.3 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.2151 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 0.68 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 14.61 h -1 ; After the reaction liquid passes through the reactor, it is cooled to room temperature and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol is 89.77%; 95.49g of methacrylic acid and 1.3g of hydroquinone are added to the organic phase, and after thorough mixing, the mixture is heated to room temperature at a liquid hourly space velocity of 0.3227h -1The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 113°C, the reaction pressure was 1.2 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 10.4 h -1 The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 99.25%, and the yield of dodecyl methacrylate was 98.8%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 7.75h.

[0059] Example 6

[0060] Methacrylic acid 607.08g, 1-dodecanol 976.56g, 1-tetradecanol 312.39g and hydroquinone 1.3g were fully mixed. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.323h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 0.3 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 70.41 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 92.55%, and the conversion rate of tetradecanol was 90.17%. The organic phase was distilled under reduced pressure to reduce the water content in the organic phase to 870ppm; 148.54g of methacrylic acid and 1.3g of hydroquinone were added to the organic phase, and after thorough mixing, the mixture was heated to a liquid hourly space velocity of 0.387h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 111°C, the reaction pressure was 0.3 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 8.4 h -1 ; After the reaction liquid passes through the reactor, it is cooled to room temperature, centrifuged to obtain an organic phase, and then subjected to post-treatment to obtain a mixture of dodecyl methacrylate and tetradecyl methacrylate. The final product is analyzed by gas chromatography, and the conversion rate of dodecyl alcohol is 99.45%, the conversion rate of tetradecyl alcohol is 99.5%, the yield of dodecyl methacrylate is 98.75%, and the yield of tetradecyl methacrylate is 98.25%. The total residence time of the reaction liquid in the two-stage fixed bed reactor is 5.68h.

[0061] Example 7

[0062] Methacrylic acid 607.08g, 1-dodecanol 976.56g, 1-tetradecanol 312.39g and hydroquinone 1.3g were fully mixed. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.323h -1The reaction mixture was introduced into a first fixed bed reactor filled with a macroporous acidic resin, wherein the center temperature of the first fixed bed reactor was 111°C, the reaction pressure was 10 kPa, and there was no nitrogen co-flow during the reaction. The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 96.25%, and the conversion rate of tetradecanol was 93.57%. 210.36 g of methacrylic acid and 1.3 g of hydroquinone were added to the organic phase, and after being fully mixed, the reaction mixture was concentrated to a liquid hourly space velocity of 0.43 h -1 The reaction mixture was introduced into a second fixed bed reactor filled with macroporous acidic resin, the center temperature of the second fixed bed reactor was 112°C, the reaction pressure was 10 kPa, and there was no nitrogen co-flow during the reaction; the reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation, and then a mixture of dodecyl methacrylate and tetradecyl methacrylate was obtained by post-treatment. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 99.41%, the conversion rate of tetradecyl alcohol was 98.78%, the yield of dodecyl methacrylate was 98.85%, and the yield of tetradecyl methacrylate was 98.45%. The total residence time of the reaction liquid in the two fixed bed reactors was 5.42 h.

[0063] Example 8

[0064] 905.62 g of methacrylic acid, 1305.8 g of 1-dodecanol and 1.3 g of hydroquinone were mixed thoroughly. After preheating, the mixed raw materials were heated at a liquid hourly space velocity of 0.172 h -1 The first fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the first fixed bed reactor was 115°C, the reaction pressure was 0.3 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 10.71 h -1 ; The reaction liquid was cooled to room temperature after passing through the reactor, and centrifuged to obtain an organic phase and an aqueous phase. At this time, the conversion rate of dodecanol was 94.92%; 1.3 g of hydroquinone was added to the organic phase, and after thorough mixing, the liquid hourly space velocity was 0.172 h -1 The second fixed bed reactor filled with macroporous acidic resin was introduced. The center temperature of the second fixed bed reactor was 115°C, the reaction pressure was 0.3 MPa, nitrogen was co-flowed during the reaction, and the nitrogen space velocity was 11.13 h -1 The reaction liquid was cooled to room temperature after passing through the reactor, and the organic phase was obtained by centrifugation and then post-treated to obtain dodecyl methacrylate. The final product was analyzed by gas chromatography, and the conversion rate of dodecyl alcohol was 97.26%, and the yield of dodecyl methacrylate was 93.11%. The total residence time of the reaction liquid in the two-stage fixed bed reactor was 11.63h.

[0065] In the above embodiments and comparative examples, comparative examples 1-2 did not adopt a segmented reaction mode, comparative example 1 did not carry out nitrogen co-flow, and comparative example 2 used a water separator to continuously distill and separate the water generated in the esterification reaction along with methacrylic acid, but none of them could obtain the results of high conversion rate and yield as in the embodiments of the present invention; the esterification reaction in Examples 1-6 was carried out under the condition of nitrogen co-flow, which was able to obtain results similar to the esterification reaction in Example 7 under negative pressure conditions, and the nitrogen co-flow method was better controlled than the negative pressure condition; comparing Examples 1-6 with Example 8, it can be seen that controlling the liquid hourly space velocity, the esterification reaction temperature difference and the amount of additional (alkyl) acrylic acid within the preferred range can obtain a better reaction effect.

[0066] The following examples are used to demonstrate that the preferred method of removing the polymerization inhibitor of the present invention can achieve a better effect of removing the polymerization inhibitor.

[0067] Example 9

[0068] A dodecyl methacrylate solution containing 0.14wt% of hydroquinone is extracted with a water-based extraction solvent (a mixture of water and methanol) having a water content of 60wt% as an extractant, and the dosage of the single-stage extractant is 60wt% of the mass of the phenolic dodecyl methacrylate solution. A secondary cross-current extraction is performed at 30°C. After the extraction, the hydroquinone content in the dodecyl methacrylate solution is 0.0008wt%, and the dephenolization efficiency is as high as 99.43%.

[0069] Example 10

[0070] A dodecyl methacrylate solution containing 0.14wt% of hydroquinone is subjected to continuous countercurrent extraction using a water-based extraction solvent with a water content of 100wt% as an extractant. The flow rate of the phenolic dodecyl methacrylate solution is 265.83g / h, the flow rate of the extractant is 159.50g / h, and the extraction temperature is 71.14°C. After continuous countercurrent extraction, the hydroquinone content in the dodecyl methacrylate solution is 0.0015wt%, and the dephenolization efficiency is as high as 98.93%.

[0071] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for continuously preparing (alkyl) acrylate, characterized in that: The method includes: (1) mixing (alkyl) acrylic acid, alcohol and optional inhibitor to carry out a first stage esterification reaction; (2) separating the aqueous phase from the product of the first stage esterification reaction and subjecting the remaining organic phase to a second stage esterification reaction; (3) Optionally, the aqueous phase of the product of the previous esterification reaction is separated, and the remaining organic phase is subjected to the Nth esterification reaction, and this cycle is repeated multiple times, N≥3. (4) post-treating the second stage esterification reaction product of step (2) or the Nth stage esterification reaction product of step (3) to obtain a purified (alkyl) acrylate.

2. The method according to claim 1, wherein: The conversion rate of the first stage esterification reaction is 40-98%, preferably 70-94%, based on alcohol hydroxyl groups; and / or, the conversion rate of the second stage esterification reaction is 40-100%, preferably 70-99.5%, based on alcohol hydroxyl groups; and / or, the conversion rate of the Nth stage esterification reaction is 40-100%, preferably 70-99.5%, based on alcohol hydroxyl groups; And / or, the total conversion rate of each stage of esterification reaction is ≥99%.

3. The method according to claim 1 or 2, wherein: In step (2) and / or step (3), the aqueous phase in the product of the esterification reaction is separated by distillation and / or liquid-liquid phase separation, preferably at least one of distillation, flashing, stripping, sedimentation, decantation, coalescence and centrifugation.

4. The method according to claim 1, wherein: Each stage of esterification reaction is carried out under the flow of inert gas, and the ratio of the volume space velocity of the inert gas to the liquid hourly space velocity of the liquid raw material is: 0-1000, preferably 10-250; Preferably, the volume space velocity of the inert gas is 3-500h -1 , preferably 8-80h -1 .

5. The method according to claim 1 or 2, wherein: The method further comprises: in step (2) and / or step (3), adding (alkyl) acrylic acid and an optional polymerization inhibitor, so that the molar ratio of each additional amount of (alkyl) acrylic acid added in terms of carboxyl groups to the alcohol in terms of hydroxyl groups is 0.05-2, preferably 0.05-0.5, and the amount of the polymerization inhibitor added each time is 0.01-3 wt %, preferably 0.01-1 wt %, of the total weight of the (alkyl) acrylic acid and the alcohol.

6. The method according to claim 1 or 2, wherein: In step (1), the molar ratio of (alkyl) acrylic acid calculated as carboxyl group to alcohol calculated as hydroxyl group is 0.1-2, preferably 0.8-1.1; And / or, the molar ratio of (alkyl) acrylic acid calculated as carboxyl groups to alcohol calculated as hydroxyl groups during the entire preparation process is 1-4, preferably 1.05-1.

5.

7. The method according to claim 1 or 2, wherein: The number of carbon atoms of the alkyl group in the alkyl acrylic acid is less than or equal to 8, preferably less than or equal to 4, and more preferably, the alkyl group in the alkyl acrylic acid is methyl, ethyl or propyl; And / or, the alcohol is a fatty alcohol having a normal pressure boiling point higher than 100° C. and being insoluble or slightly soluble in water, preferably at least one of monohydric alcohols having a carbon number of 9 to 22, more preferably at least one of n-decanol, n-undecanol, n-dodecanol, n-tetradecanol, n-hexadecanol and n-octadecyl alcohol.

8. The method according to claim 1 or 2, wherein: The amount of the polymerization inhibitor is 0.03-5% by weight of the total weight of the (alkyl) acrylic acid and the alcohol; And / or, the polymerization inhibitor is at least one of a phenol polymerization inhibitor, a quinone polymerization inhibitor, an aromatic amine polymerization inhibitor and an inorganic salt polymerization inhibitor.

9. The method according to claim 1 or 2, wherein: The conditions of each stage of esterification reaction are independently as follows: temperature is 80-140°C, pressure is 0-10MPaG, liquid hourly space velocity of the reaction raw material is 0.1-3h -1 ; And / or, the temperature of the first stage esterification reaction is 1-10°C lower than the temperature of the second stage esterification reaction.

10. The method according to claim 9, wherein: The conditions of each stage of esterification reaction are independently as follows: temperature is 90-130°C, pressure is 0.002-2MPaG, liquid hourly space velocity of the reaction raw material is 0.18-1h -1 ; And / or, the temperature of the first stage esterification reaction is 1-5°C lower than the temperature of the second stage esterification reaction.

11. The method according to claim 1, wherein: Step (4) includes removing the polymerization inhibitor by alkali washing or extraction, preferably extraction; Preferably, the extractant used for extraction includes an alcohol-based extractant and / or a water-based extractant, preferably a water-based extractant; More preferably, the water content of the water-based extractant is 10-100 wt%, preferably 60-100 wt%.

12. The method according to claim 1, wherein: The method further comprises step (5): further recovering (alkyl) acrylic acid from the aqueous phase obtained in step (2) and / or step (3), preferably by extracting and recovering the (alkyl) acrylic acid in the aqueous phase with an extractant.