A solid polymerization inhibitor for acrylic acid and its esters, preparation method and application thereof

Abstract

The invention discloses a solid polymerization inhibitor for acrylic acid and its esters, a preparation method and an application thereof, comprising component A, polyhydroxybenzaldehyde and silica gel, wherein the component A is one of aminopropyltrimethoxysilane or aminopropyltriethoxysilane, the molar ratio of the component A to the polyhydroxybenzaldehyde is 1:1-1.1, and the silica gel is 2.7-2.8 times the molar mass of the component A, and the invention relates to the technical field of organic synthesis. The solid polymerization inhibitor for acrylic acid and its esters, the preparation method and the application thereof can achieve the purpose of both achieving a good blocking effect and facilitating subsequent washing by using a solid polymerization inhibitor to block the polymerization reaction of acrylic acid and its esters during high-temperature esterification, directly filtering after the reaction without a large amount of washing, and well achieving the purpose of both achieving a good blocking effect and facilitating subsequent washing, and by adopting an annular porous pressing molding design, it can be fully and comprehensively contacted with acrylic acid and its esters like a liquid phase and a gas phase polymerization inhibitor, and will not affect the polymerization inhibition effect.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, in particular to a solid polymerization inhibitor for acrylic acid and its esters, a preparation method and application thereof. Background Art

[0002] As environmental protection requirements become increasingly stringent, effective and environmentally friendly heterogeneous catalysts are increasingly needed in the chemical industry. For example, heterogeneous solid acid catalysts that can replace traditional acid catalysts such as sulfuric acid, hydrofluoric acid, and organic sulfonic acid are needed. Their advantages include simple operation, easy separation, reusability, avoidance of side reactions, and high product selectivity.

[0003] In recent years, solid acids have been synthesized and applied to the synthesis of various acrylic esters. However, in order to prevent the polymerization reaction of acrylic acid and its esters during high-temperature esterification, it is still necessary to add a large amount of various inhibitors. After the esterification reaction is completed, in order not to affect the subsequent application, a large amount of water needs to be added to wash out the inhibitor remaining in the product. There are many operation steps, a large amount of wastewater pollution is generated, and the production cost is high. Therefore, the acrylic ester synthesis industry is in urgent need of a solid inhibitor that can effectively inhibit polymerization during the synthesis process, can be effectively separated after the synthesis is completed, and does not remain in the product.

[0004] Referring to the prior art publication number CN105732360B, a polymerization inhibitor for the refining of acrylic acid monomers is disclosed. By using hydroquinone, chlorpromazine and isopromazine to prepare a modified polymerization inhibitor, there is no need to change the original reaction conditions of the production device. The newly added polymerization inhibitor is simple and easy to obtain. The use of the modified catalyst can significantly improve the continuous production cycle of the distillation tower in the production of acrylic acid monomers, and the cycle reaches 200 days. The invention can effectively improve the continuous operation time of the acrylic acid monomer distillation tower, solves the problem of short continuous operation time of the acrylic acid monomer distillation tower in the industry, and makes the operation of the acrylic acid monomer distillation tower more stable.

[0005] Referring to the prior art publication number CN114409528B, a multifunctional and efficient inhibitor for acrylic acid refining can effectively capture the peroxy free radicals generated during the acrylic acid refining process by using a liquid phase inhibitor, thereby inhibiting the polymerization of acrylic acid, and using a gas phase inhibitor can effectively inhibit the polymerization in the gas phase when a phase change occurs during the acrylic acid refining process. The composite inhibitor provided by the invention has excellent inhibition performance and multiple functions, can effectively inhibit the polymerization of acrylic acid, and can effectively prevent the inevitable polymer scaling and adhesion on the distillation refining equipment, ensure the long-term safe and stable operation of the acrylic acid device, and promote the quality and efficiency improvement of the acrylic acid device.

[0006] Comprehensive analysis of the above referenced prior art reveals the following defects:

[0007] Most of the existing polymerization inhibitors adopt liquid-phase polymerization inhibitors dissolved in acrylic acid and its esters themselves to block the polymerization reaction of acrylic acid and its esters during high-temperature esterification. For example, referring to the prior art CN105732360B, a polymerization inhibitor for refining acrylic acid monomer is prepared by using hydroquinone, chlorpromazine and isopromazine. After the reaction is completed, a large amount of water is still needed to wash out the residual polymerization inhibitor in the product. There are many operation steps, a large amount of wastewater pollution is generated, the production cost is high, and it is inconvenient to clean. It is impossible to use solid polymerization inhibitors to block the polymerization reaction of acrylic acid and its esters during high-temperature esterification. Direct filtration after the reaction does not require a lot of washing. It is impossible to achieve both a good barrier effect and convenient subsequent washing, which brings great inconvenience to people's use.

[0008] Although the existing polymerization inhibitors are also used as non-liquid phase polymerization inhibitors, for example, referring to the prior art CN114409528B, a multifunctional and efficient polymerization inhibitor for acrylic acid refining is used in combination with liquid phase and gas phase polymerization inhibitors to inhibit the polymerization of acrylic acid, but a large amount of washing is still required after the acrylic acid reaction. The solid polymerization inhibitor of the present invention is designed by an annular porous pressing molding, and can fully and comprehensively contact with acrylic acid and its esters like liquid phase and gas phase polymerization inhibitors, without affecting the polymerization inhibition effect. By increasing the surface area of ​​the solid polymerization inhibitor structure design, the contact area during the polymerization inhibition reaction is greatly increased. When in use, acrylic acid and its esters will fully contact the surface of each gap in the annular filter cake, and can achieve a good polymerization inhibition effect in the same time. Summary of the invention

[0009] In view of the deficiencies in the prior art, the present invention provides a solid polymerization inhibitor for acrylic acid and its esters, a preparation method and an application thereof, which solves the problem that after the reaction of the prior polymerization inhibitor is completed, a large amount of water still needs to be added to wash out the residual polymerization inhibitor in the product, the operation steps are many, a large amount of wastewater pollution is generated, the production cost is high, and it is inconvenient to clean, and it is not possible to use a solid polymerization inhibitor to block the polymerization reaction of acrylic acid and its esters during high-temperature esterification, and directly filter after the reaction without a large amount of washing, and it is impossible to achieve both a good blocking effect and convenient subsequent washing. At the same time, the existing solid polymerization inhibitor is not in sufficient contact with acrylic acid and its esters to affect the polymerization efficiency.

[0010] To achieve the above purpose, the present invention is implemented by the following technical scheme: a solid polymerization inhibitor for acrylic acid and its esters, comprising component A, polyhydroxybenzaldehyde and silica gel, wherein component A is one of aminopropyltrimethoxysilane and aminopropyltriethoxysilane, and polyhydroxybenzaldehyde is one of benzaldehydes containing 1 hydroxyl group, 2 hydroxyl groups or 3 hydroxyl groups on the benzene ring, and the position of the hydroxyl group is any position on the benzaldehyde, such as dihydroxybenzaldehyde at positions 3,4-, 3,5-, 2,3-, 2,4-, 2,5-, 2,6-, etc. and trihydroxybenzaldehyde at positions 2,3,4-, 3,4,5-, 2,4,6-, 2,3,5-, etc.; the molar ratio of component A to polyhydroxybenzaldehyde is 1:1-1.1, and the molar mass of silica gel is 2.7-2.8 times that of component A.

[0011] Preferably, when the polyhydroxybenzaldehyde is 2,3,4-trihydroxybenzaldehyde, the structural formula of the solid polymerization inhibitor of acrylic acid and its esters is as follows:

[0012] ;

[0013] in, For silica gel.

[0014] Preferably, the silica gel is silica gel A60.

[0015] The present invention also provides a method for preparing a solid polymerization inhibitor for acrylic acid and its esters, which specifically comprises the following steps:

[0016] S1. Add component A and polyhydroxybenzaldehyde to an organic solvent with a molar mass 11-11.2 times that of component A in sequence, stir at a constant speed of 40-50 r / min, heat to reflux, and keep reacting for 19-21 hours. After the reaction is completed, cool to 60-70° C. to allow component A and polyhydroxybenzaldehyde to fully undergo a dehydration reaction to generate an intermediate;

[0017] S2, adding silica gel in batches to load the intermediate in step S1 with silica gel, after complete addition, separating the low-boiling point methanol and toluene mixture, and continuing the reflux reaction for 11-13h to separate the methanol and toluene mixture;

[0018] S3, after cooling to room temperature, filtering and draining to obtain solid filter residue of the gear, pouring the solid filter residue into a forming mold of a pressure drying device, starting the pressure drying device to press the filter residue in the mold into a ring-shaped filter cake that can fully contact with acrylic acid and its esters, and heating the ring-shaped filter cake at a temperature of 80-100° C. through a drying mechanism to dry it, keeping it for 5-10 minutes, then opening the mold and taking out the ring-shaped filter cake;

[0019] S4, washing the annular filter cake obtained in step S3 with toluene and methanol three times respectively, and then passing through a vacuum drying device to obtain a polymerization inhibitor of solid acrylic acid and its esters.

[0020] Preferably, the intermediate in step S1 is one of polyhydroxybenzylimidopropyltrimethoxysilane or polyhydroxybenzylimidopropyltriethoxysilane.

[0021] Preferably, the organic solvent in step S1 is any one of toluene or xylene.

[0022] Preferably, the specific steps of adding silica gel in batches in step S2 are: adding silica gel in three equal amounts, with the time interval between each addition being 3-5 minutes.

[0023] Preferably, in step S3, the annular filter cake is composed of an inner ring and an outer ring, and the inner ring and the outer ring are connected by six material columns that are pressed and formed at the same time, and the thickness of the entire annular filter cake is 3-7 mm.

[0024] Preferably, the process of washing the annular filter cake three times with toluene and methanol respectively in step S4 is specifically as follows:

[0025] T1. Place the annular filter cake to be washed into a washing tank filled with toluene, and vibrate the washing tank at a low speed for 5-10 minutes using an oscillating device to avoid violent collision between the annular filter cake and the washing tank, which may cause the annular filter cake to break;

[0026] T2, then drain the toluene, replace with clean toluene and repeat T1 operation, then repeat the toluene cleaning for the third time;

[0027] T3, then replace methanol and repeat step T1 for washing three times, thus completing the washing of the annular filter cake.

[0028] The present invention also provides a method for using a solid polymerization inhibitor prepared by a method for preparing a solid polymerization inhibitor for acrylic acid and its esters in a high-temperature esterification polymerization reaction of acrylic acid and its esters, which specifically comprises the following steps:

[0029] E1. Spread the annular solid inhibitor filter cake on the bottom of the reaction tank, then add acrylic acid or its ester to react with the acrylic acid or its ester. When the acrylic acid or its ester is heated to 110° C., the acrylic acid or its ester is ready to polymerize. Slowly stir the reaction tank to make the acrylic acid or its ester fully contact with the annular solid inhibitor filter cake, so as to achieve the purpose of polymerization inhibition.

[0030] E2. After the reaction of acrylic acid or its esters is completed, the solid-liquid mixture in the reaction tank is directly filtered, and part of the filter residue in the reaction liquid of the annular solid polymerization inhibitor filter cake is filtered out from the reaction liquid of acrylic acid or its esters, thus completing the barrier use of the annular solid polymerization inhibitor filter cake in the reaction of acrylic acid or its esters.

[0031] The present invention provides a solid polymerization inhibitor for acrylic acid and its esters, a preparation method and application thereof. Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The solid polymerization inhibitor for acrylic acid and its esters, preparation method and application thereof, comprising mixing aminopropyl trimethoxysilane or aminopropyl triethoxysilane with polyhydroxybenzaldehyde in an organic solvent, wherein aminopropyl trimethoxysilane or aminopropyl triethoxysilane reacts with polyhydroxybenzaldehyde to generate polyhydroxybenzyl iminopropyl trimethoxysilane or polyhydroxybenzyl iminopropyl triethoxysilane, then adding silica gel in batches, loading the silica gel, and then separating a mixture of methanol, toluene and water to prepare a solid polymerization inhibitor for acrylic acid and its esters. The polymerization inhibitor of solid acrylic acid and its esters can be used as a polymerization inhibitor in the synthesis process of various acrylic esters. After the polymerization reaction of acrylic acid and its esters is completed by high-temperature esterification, it is only necessary to filter out the polymerization inhibitor of solid acrylic acid and its esters. There is no polymerization inhibitor residue in the product, no need for water washing, and less pollution is generated. The solid polymerization inhibitor can be used to block the polymerization reaction of acrylic acid and its esters during high-temperature esterification. After the reaction, it can be directly filtered without a large amount of washing. The purpose of both achieving a good barrier effect and facilitating subsequent washing is achieved, thereby greatly facilitating people's use.

[0033] (2) The solid polymerization inhibitor for acrylic acid and its esters, preparation method and application thereof, by adopting an annular porous pressing molding design, can fully and comprehensively contact with acrylic acid and its esters like liquid phase and gas phase polymerization inhibitors, without affecting the polymerization inhibition effect. By increasing the surface area of ​​the solid polymerization inhibitor structure design, the contact area during the polymerization inhibition reaction is greatly increased. When in use, acrylic acid and its esters will fully contact the surface of each gap in the annular filter cake, and can achieve a good polymerization inhibition effect in the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the annular filter cake of the present invention;

[0035] Figure 2 The chemical reaction diagram of the reaction of aminopropyltrimethoxysilane and 2,3,4-trihydroxybenzaldehyde to generate trihydroxybenzylimidopropyltrimethoxysilane in Example 3 of the present invention;

[0036] Figure 3The chemical reaction diagram of the reaction of trihydroxybenzylimidopropyltrimethoxysilane with silica gel to generate a solid polymerization inhibitor in Example 3 of the present invention;

[0037] Figure 4 The present invention is a flow chart of a method for preparing a solid polymerization inhibitor for acrylic acid and its esters. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-Figure 4 The embodiments of the present invention provide four technical solutions: a solid polymerization inhibitor for acrylic acid and its esters, a preparation method and application thereof, specifically including the following embodiments:

[0040] Example 1: Add 71.6g aminopropyltrimethoxysilane and 55.2g 3,4-dihydroxybenzaldehyde to 800g toluene, stir at a speed of 45r / min, heat to reflux, keep reacting for 20h, cool to 60℃ after the reaction, add 200g silica gel A60 in three equal amounts, the time interval between each addition is 3min, continue to heat after complete addition, reflux reaction for 12h, separate about 110g low boiling point mixture, the mixture contains methanol, toluene and water. Cool, filter, drain, wash the filter cake with toluene and methanol three times, and then vacuum dry to obtain 261.2g of solid acrylic acid and its ester inhibitor, with a weight gain of 61.2g.

[0041] Example 2: Add 71.6g aminopropyltrimethoxysilane and 61.6g 3,4,5-trihydroxybenzaldehyde to 800g toluene, stir at a speed of 45r / min, heat to reflux, keep reacting for 20h, cool to 60℃ after the reaction, add 200g silica gel A60 in three equal amounts, the time interval between each addition is 3min, continue to heat after complete addition, reflux reaction for 12h, separate about 110g low boiling point mixture, the mixture contains methanol, toluene and water. Cool, filter, drain, wash the filter cake with toluene and methanol three times each, and then vacuum dry to obtain 267.6g of solid acrylic acid and its ester inhibitor, with a weight gain of 67.6g.

[0042] Embodiment 3: Figure 2As shown, 71.6 g of aminopropyl trimethoxysilane and 55.2 g of 2,3,4-trihydroxybenzaldehyde were added to 800 g of toluene organic solvent, stirred at a speed of 45 r / min, heated to reflux, and kept reacting for 20 h. After the reaction, the temperature was lowered to 60 ° C to allow aminopropyl trimethoxysilane and 2,3,4-trihydroxybenzaldehyde to fully undergo a dehydration reaction to generate an intermediate trihydroxybenzyl iminopropyl trimethoxysilane. Figure 3 As shown, 200g of silica gel A60 is added in three equal amounts, with the time interval between each addition being 3min. After complete addition, the temperature is continued to rise, and the reaction is refluxed for 12h to separate out about 110g of a low-boiling mixture, which contains methanol, toluene and water. After cooling to room temperature, the solid filter residue of the gear is obtained by filtering and drying. The solid filter residue is poured into a forming mold of a pressure drying device, and the pressure device is started to press the filter residue in the mold into an annular filter cake that can fully contact with acrylic acid and its esters. The annular filter cake is heated and dried at 90°C by a drying mechanism. After maintaining for 6min, the mold is opened and the annular filter cake is taken out. The annular filter cake is composed of an inner ring and an outer ring, and the inner ring and the outer ring are connected by six material columns that are pressed and formed at the same time. The thickness of the entire annular filter cake is 5mm. The shape of the mold cavity of the pressure drying device forming mold in the embodiment of the present invention is completely consistent with the shape of the annular filter cake, and at the same time, it is produced during the pressure forming process. The residual materials should be collected and collected for subsequent reuse. In the embodiment of the present invention, the pressurized drying equipment is an existing hydraulic press with a heating and drying unit. During the process of the die clamping and pressing down, the die is heated by the heating and drying unit, so that the filter residue in the die is heated, and the water in the filter residue is evaporated and discharged from the exhaust hole in the die. After the die is opened, a dry annular filter cake can be obtained. The obtained annular filter cake is washed three times with toluene and methanol respectively, and then passed through a vacuum drying equipment to obtain a polymerization inhibitor of solid acrylic acid and its esters. 268.3g of the polymerization inhibitor of solid acrylic acid and its esters is obtained, and the weight gain is 68.3g. The process of washing the annular filter cake three times with toluene and methanol respectively is specifically as follows:

[0043] T1. Place the annular filter cake to be washed into a washing tank filled with toluene, and vibrate the washing tank at a low speed for 5-10 minutes using an oscillating device to avoid violent collision between the annular filter cake and the washing tank, which may cause the annular filter cake to break;

[0044] T2, then drain the toluene, replace with clean toluene and repeat T1 operation, then repeat the toluene cleaning for the third time;

[0045] T3, then replace methanol and repeat step T1 for washing three times, thus completing the washing of the annular filter cake.

[0046] The embodiment of the present invention also provides a method for preparing a solid polymerization inhibitor for acrylic acid and its esters, and a method for using the solid polymerization inhibitor prepared in a high-temperature esterification polymerization reaction of acrylic acid and its esters, which specifically comprises the following steps:

[0047] E1. Spread the annular solid inhibitor filter cake on the bottom of the reaction tank, then add acrylic acid or its ester to react with the acrylic acid or its ester. When the acrylic acid or its ester is heated to 110° C., the acrylic acid or its ester is ready to polymerize. Slowly stir the reaction tank to make the acrylic acid or its ester fully contact with the annular solid inhibitor filter cake, so as to achieve the purpose of polymerization inhibition.

[0048] E2. After the reaction of acrylic acid or its esters is completed, the solid-liquid mixture in the reaction tank is directly filtered, and part of the filter residue in the reaction liquid of the annular solid polymerization inhibitor filter cake is filtered out from the reaction liquid of acrylic acid or its esters, thus completing the barrier use of the annular solid polymerization inhibitor filter cake in the reaction of acrylic acid or its esters.

[0049] Example 4: 71.6g of aminopropyltriethoxysilane and 55.2g of 2,3,4-trihydroxybenzaldehyde were added to 800g of xylene organic solvent, stirred at a uniform speed of 45r / min, heated to reflux, and maintained for 20h. After the reaction, the temperature was lowered to 60°C to allow aminopropyltriethoxysilane and 2,3,4-trihydroxybenzaldehyde to fully dehydrate and generate an intermediate trihydroxybenzyliminopropyltriethoxysilane. 200g of silica gel A60 was added in three equal amounts, with a time interval of 3min between each addition. After complete addition, the temperature was continued to rise, and the reaction was refluxed for 12h. About 110g of a low boiling point mixture was separated, and the mixture contained methanol, toluene and water. After cooling to room temperature, the solid filter residue of the gear is obtained by filtering and drying. The solid filter residue is poured into a forming mold of a pressure drying device, and the pressure device is started to press the filter residue in the mold into an annular filter cake that can fully contact with acrylic acid and its esters. The annular filter cake is heated and dried at a temperature of 90° C. by a drying mechanism. After keeping for 6 minutes, the mold is opened and the annular filter cake is taken out. The annular filter cake is composed of an inner ring and an outer ring, and the inner ring and the outer ring are connected by six material columns that are pressed and formed at the same time. The thickness of the entire annular filter cake is 5 mm. The obtained annular filter cake is washed three times with toluene and methanol respectively, and then passed through a vacuum drying device to obtain a polymerization inhibitor of solid acrylic acid and its esters. 269.8 g of the polymerization inhibitor of solid acrylic acid and its esters is obtained, and the weight gain is 69.8 g. The process of washing the annular filter cake three times with toluene and methanol respectively is specifically as follows:

[0050] T1. Place the annular filter cake to be washed into a washing tank filled with toluene, and vibrate the washing tank at a low speed for 5-10 minutes using an oscillating device to avoid violent collision between the annular filter cake and the washing tank, which may cause the annular filter cake to break;

[0051] T2, then drain the toluene, replace with clean toluene and repeat T1 operation, then repeat the toluene cleaning for the third time;

[0052] T3, then replace methanol and repeat step T1 for washing three times, thus completing the washing of the annular filter cake.

[0053] The embodiment of the present invention also provides a method for preparing a solid polymerization inhibitor for acrylic acid and its esters, and a method for using the solid polymerization inhibitor prepared in a high-temperature esterification polymerization reaction of acrylic acid and its esters, which specifically comprises the following steps:

[0054] E1. Spread the annular solid inhibitor filter cake on the bottom of the reaction tank, then add acrylic acid or its ester to react with the acrylic acid or its ester. When the acrylic acid or its ester is heated to 110° C., the acrylic acid or its ester is ready to polymerize. Slowly stir the reaction tank to make the acrylic acid or its ester fully contact with the annular solid inhibitor filter cake, so as to achieve the purpose of polymerization inhibition.

[0055] E2. After the reaction of acrylic acid or its esters is completed, the solid-liquid mixture in the reaction tank is directly filtered, and part of the filter residue in the reaction liquid of the annular solid polymerization inhibitor filter cake is filtered out from the reaction liquid of acrylic acid or its esters, thus completing the barrier use of the annular solid polymerization inhibitor filter cake in the reaction of acrylic acid or its esters.

[0056] Application comparison experiment:

[0057] The solid polymerization inhibitor prepared in Examples 1-4, the silica gel without polymerization inhibitor, and the polymerization inhibitor 701 produced by Zhuzhou Yuancheng Hezhong Technology Development Co., Ltd. were respectively applied to the heating process of acrylic acid to observe whether the acrylic acid is polymerized to detect the performance of Examples 1-4. Specifically, 100 grams of the solid polymerization inhibitor prepared in Examples 1-4, the silica gel without polymerization inhibitor, and the polymerization inhibitor 701 produced by Zhuzhou Yuancheng Hezhong Technology Development Co., Ltd. were added to a 500ml flask, and then about 200 grams of acrylic acid were added to make the liquid submerge the silica gel. Then heat to 110°C and keep warm while stirring slowly. When acrylic acid polymerizes, it all solidifies into a mass. When acrylic acid is not polymerized, the liquid can still flow, and the time when polymerization occurs is recorded. The results are shown in Table 1 below:

[0058] Table 1 Data table of application comparison experiment

[0059] Blank example (without inhibitor silica gel) Existing example (Polymerization inhibitor 701) Example 1 Example 2 Example 3 Example 4 Aggregation time Polymerize within 1 hour Aggregation within 33 hours No polymerization for 48 hours No polymerization for 48 hours No polymerization for 52 hours No polymerization for 52 hours

[0060] From Table 1 above, it can be seen that the solid polymerization inhibitors prepared by using Examples 1-4 of the present invention still did not polymerize within 48 hours during the heating process of acrylic acid and its esters, while the silica gel blank without polymerization inhibitor polymerized within 1 hour, and the polymerization inhibitor 701 produced by Zhuzhou Yuancheng Hezhong Technology Development Co., Ltd. polymerized within 33 hours. Through comparative analysis, it can be seen that the polymerization inhibitors prepared by using Examples 1-4 of the present invention have significantly better polymerization inhibition effects than the blank example and the existing example, and the annular filter cake design with increased contact area of ​​Examples 3 and 4 of the present invention can make the polymerization avoidance time of acrylic acid and its esters longer than that of Examples 1 and 2.

[0061] In the above comparative application experiment, the same amount of acrylic acid and polymerization inhibitor mixtures in the blank example and the prior art example were marked as group A and group B respectively, and the acrylic acid and solid polymerization inhibitor mixture that did not polymerize in the above Example 3 was taken as group C. Then, the above group A, group B and group C were washed and filtered with a mass of 100g as the uniform condition until the acrylic acid did not contain other substances. The washing times, water consumption and time were recorded in this process, while only the filtering time was recorded for filtering. The specific experimental data are shown in Table 2:

[0062] Table 2 Washing and filtration experiment results

[0063] Group A Group B Group C Experimental situation Wash 4 times, the total water consumption is 67.3mL, and the washing time is 2.7h Wash 4 times, the total water consumption is 56.8mL, and the washing time is 2.2h Filter twice, no washing, filtration time 0.6h

[0064] It can be seen from Table 2 that the solid polymerization inhibitor prepared by Example 3 of the present invention takes the shortest time to treat the polymerization inhibitor after the acrylic acid reaction is completed, and there is no washing wastewater. However, Group A and Group B obviously consume a large amount of washing water during the polymerization inhibitor treatment in acrylic acid, and the time is longer. Therefore, whether from the perspective of water saving or treatment efficiency, the polymerization inhibitor prepared by Example 3 of the present invention is more economical and practical.

[0065] In summary, the present invention mixes aminopropyl trimethoxysilane or aminopropyl triethoxysilane with polyhydroxybenzaldehyde in an organic solvent, and aminopropyl trimethoxysilane or aminopropyl triethoxysilane undergoes a dehydration reaction with polyhydroxybenzaldehyde to generate polyhydroxybenzyl iminopropyl trimethoxysilane or polyhydroxybenzyl iminopropyl triethoxysilane, and then silica gel is added in batches to load the silica gel, and then a mixture of methanol, toluene and water is separated to prepare a polymerization inhibitor of solid acrylic acid and its esters. The polymerization inhibitor of solid acrylic acid and its esters can be used as a polymerization inhibitor in the synthesis process of various acrylic esters. When the polymerization reaction of acrylic acid and its esters is completed by high-temperature esterification, it is only necessary to filter out the polymerization inhibitor of solid acrylic acid and its esters, and no polymerization inhibitor remains in the product. , no need for water washing, less pollution is generated, and solid inhibitors can be used to prevent acrylic acid and its esters from undergoing polymerization reactions during high-temperature esterification. After the reaction, they can be directly filtered without a large amount of washing, which achieves the purpose of both achieving a good barrier effect and facilitating subsequent washing, thereby greatly facilitating people's use. At the same time, by adopting an annular porous pressing molding design, it can fully and comprehensively contact with acrylic acid and its esters like liquid and gas phase inhibitors, without affecting the inhibition effect. By increasing the surface area of ​​the solid inhibitor structure design, the contact area during the inhibition reaction is greatly increased. When in use, acrylic acid and its esters will fully contact the surfaces of each gap in the annular filter cake, and can achieve a good inhibition effect in the same time.

[0066] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0067] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A solid polymerization inhibitor for acrylic acid and its esters, characterized in that: The preparation method is as follows, which specifically comprises the following steps: S1. Add component A and polyhydroxybenzaldehyde to an organic solvent with a molar mass 11-11.2 times that of component A in sequence, stir at a constant speed of 40-50 r / min, heat to reflux, and keep reacting for 19-21 hours. After the reaction is completed, cool to 60-70° C. to allow component A and polyhydroxybenzaldehyde to fully undergo a dehydration reaction to generate an intermediate; S2, adding silica gel in batches to load the intermediate in step S1 with silica gel, after complete addition, separating the low-boiling point methanol and toluene mixture, and continuing the reflux reaction for 11-13h to separate the methanol and toluene mixture; S3, after cooling to room temperature, filtering and draining to obtain a solid filter residue, pouring the solid filter residue into a forming mold of a pressure drying device, starting the pressure device to press the filter residue in the mold into a ring-shaped filter cake that can fully contact with acrylic acid and its esters, and heating the ring-shaped filter cake at a temperature of 80-100° C. through a drying mechanism to dry it, keeping it for 5-10 minutes, then opening the mold and taking out the ring-shaped filter cake; S4, washing the annular filter cake obtained in step S3 with toluene and methanol three times respectively, and then passing through a vacuum drying device to obtain a polymerization inhibitor of solid acrylic acid and its esters; The component A is one of aminopropyltrimethoxysilane and aminopropyltriethoxysilane, the polyhydroxybenzaldehyde is one of benzaldehydes containing 1 hydroxyl group, 2 hydroxyl groups or 3 hydroxyl groups on the benzene ring, the molar ratio of the component A to the polyhydroxybenzaldehyde is 1:1-1.1, and the molar mass of the silica gel is 2.7-2.8 times that of the component A.

2. A solid polymerization inhibitor for acrylic acid and its esters according to claim 1, characterized in that: The silica gel is silica gel A60.

3. A method for preparing the solid polymerization inhibitor for acrylic acid and its esters according to any one of claims 1 to 2, characterized in that: The specific steps include: S1. Add component A and polyhydroxybenzaldehyde to an organic solvent with a molar mass 11-11.2 times that of component A in sequence, stir at a constant speed of 40-50 r / min, heat to reflux, and keep reacting for 19-21 hours. After the reaction is completed, cool to 60-70° C. to allow component A and polyhydroxybenzaldehyde to fully undergo a dehydration reaction to generate an intermediate; S2, adding silica gel in batches to load the intermediate in step S1 with silica gel, after complete addition, separating the low-boiling point methanol and toluene mixture, and continuing the reflux reaction for 11-13h to separate the methanol and toluene mixture; S3, after cooling to room temperature, filtering and draining to obtain a solid filter residue, pouring the solid filter residue into a forming mold of a pressure drying device, starting the pressure device to press the filter residue in the mold into a ring-shaped filter cake that can fully contact with acrylic acid and its esters, and heating the ring-shaped filter cake at a temperature of 80-100° C. through a drying mechanism to dry it, keeping it for 5-10 minutes, then opening the mold and taking out the ring-shaped filter cake; S4, washing the annular filter cake obtained in step S3 with toluene and methanol three times respectively, and then passing through a vacuum drying device to obtain a polymerization inhibitor of solid acrylic acid and its esters.

4. The method for preparing a solid polymerization inhibitor for acrylic acid and its esters according to claim 3, characterized in that: The intermediate in step S1 is one of polyhydroxybenzylimidopropyltrimethoxysilane and polyhydroxybenzylimidopropyltriethoxysilane.

5. The method for preparing a solid polymerization inhibitor for acrylic acid and its esters according to claim 3, characterized in that: In step S1, the organic solvent is any one of toluene or xylene.

6. The method for preparing a solid polymerization inhibitor for acrylic acid and its esters according to claim 3, characterized in that: The specific steps of adding silica gel in batches in step S2 are: adding silica gel in three equal amounts, with the time interval between each addition being 3-5 minutes.

7. The method for preparing a solid polymerization inhibitor for acrylic acid and its esters according to claim 3, characterized in that: In step S3, the annular filter cake is composed of an inner ring and an outer ring, and the inner ring and the outer ring are connected by six material columns that are pressed and formed at the same time. The thickness of the entire annular filter cake is 3-7 mm.

8. The method for preparing a solid polymerization inhibitor for acrylic acid and its esters according to claim 3, characterized in that: The process of washing the annular filter cake three times with toluene and methanol respectively in step S4 is specifically as follows: T1. Place the annular filter cake to be washed into a washing tank filled with toluene, and vibrate the washing tank at a low speed for 5-10 minutes using an oscillating device to avoid violent collision between the annular filter cake and the washing tank, which may cause the annular filter cake to break; T2, then drain the toluene, replace with clean toluene and repeat T1 operation, then repeat the toluene cleaning for the third time; T3, then replace methanol and repeat step T1 for washing three times, thus completing the washing of the annular filter cake.

9. A method for using the solid polymerization inhibitor prepared by the method of any one of claims 3 to 8 in the high-temperature esterification polymerization reaction of acrylic acid and its esters, characterized in that: The specific steps include: E1. Spread the annular solid inhibitor filter cake on the bottom of the reaction tank, then add acrylic acid or its ester to react with the acrylic acid or its ester. When the acrylic acid or its ester is heated to 110° C., the acrylic acid or its ester is ready to polymerize. Slowly stir the reaction tank to make the acrylic acid or its ester fully contact with the annular solid inhibitor filter cake, so as to achieve the purpose of polymerization inhibition. E2. After the reaction of acrylic acid or its esters is completed, the solid-liquid mixture in the reaction tank is directly filtered, and part of the filter residue in the reaction liquid of the annular solid polymerization inhibitor filter cake is filtered out from the reaction liquid of acrylic acid or its esters, thus completing the barrier use of the annular solid polymerization inhibitor filter cake in the reaction of acrylic acid or its esters.

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