A kind of preparation method of dimethylolbutyraldehyde

Abstract

The present application embodiment provides a method for preparing dimethylolbutyraldehyde, and relates to the field of aldehyde compounds. It includes adding 324 grams of formaldehyde solution with a content of 37% to a 1L reactor and starting stirring, uniformly dropping 144 grams of n-butyraldehyde and 59 grams of an aqueous solution with a content of 10% trimethylamine solution into the reactor, controlling the dropping speed to 2 hours, controlling the reaction temperature to 35-40°C with a water bath during the dropping process, heating to 40-45°C after the dropping is completed, and keeping the reaction for 3 hours, the device can separate the synthesized DMB and other by-products by solvent extraction, and separating the reaction liquid after the condensation reaction of these by-products can effectively improve the reaction to form DMB and increase the conversion efficiency, and the DMB benefit efficiency is high, which is more conducive to the synthesis of downstream processes, and at the same time, after a large number of by-products are separated, the by-products with no economic value will disappear or be converted into products with economic benefits, effectively increasing the economic benefits of the products and by-products prepared by dimethylolbutyraldehyde.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of aldehyde compounds, and in particular to a method for preparing dimethylolbutyraldehyde. Background Art

[0002] 2,2-Dimethylolbutyraldehyde (DMB for short) has two hydroxymethyl groups and one aldehyde group, and is chemically active. DMB can be used to prepare trimethylolpropane (TMP for short) through catalytic hydrogenation, and can also be used to prepare 2,2-dimethylolbutyric acid through catalytic oxidation. It is an important organic intermediate. However, DMB is unstable and difficult to separate and purify in industry, so the yield of preparing trimethylolpropane and 2,2-dimethylolbutyric acid through DMB is not high.

[0003] DMB is synthesized by the aldol condensation reaction of formaldehyde and n-butyraldehyde (NBD) under alkali catalysis. This reaction is a reversible reaction. Since one n-butyraldehyde molecule needs to condense with two formaldehyde molecules, the yield of the product is not very high. At present, trimethylolpropane is produced in industry by the Cannizzaro disproportionation method. Excessive alkali catalyst and excessive formaldehyde are added. The generated DMB then undergoes a disproportionation reaction with formaldehyde to generate trimethylolpropane and sodium formate. Since the condensation product DMB is converted into TMP, the reaction continues to the right. Finally, the reaction conversion rate of formaldehyde and NBD can reach almost 95% or more.

[0004] In order to solve this problem and improve the conversion rate of DMB, the product DMB must be separated by an effective method so that the reaction equilibrium can be carried out thoroughly.

[0005] However, in the existing preparation technology, a large part of the reaction of the raw material NBD produces unwanted by-products, and the yield of DMB is low, which is not conducive to the synthesis of downstream processes. At the same time, a large amount of by-products enter the downstream process for hydrogenation or oxidation, which will produce a large amount of by-products with no economic value, affecting the separation of products, thus causing a great economic burden. Summary of the invention

[0006] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a method for preparing dimethylolbutyraldehyde, which comprises:

[0007] Step 1: Add 324 g of 37% formaldehyde solution into a 1L reactor and start stirring, then evenly drop 144 g of n-butyraldehyde and 59 g of 10% trimethylamine solution into the reactor, control the dropping speed to 2 hours, and control the reaction temperature at 35-40°C with a water bath during the dropping process. After the dropping is completed, heat to 40-45°C and keep the reaction for 3 hours;

[0008] Step 2: neutralize the pH of the reaction solution to pH 6.0-7.0 with formic acid;

[0009] Step 3: Use a continuous four-stage countercurrent extraction and four-stage countercurrent water washing test tank to extract and wash the obtained reaction solution with n-butyraldehyde and pure water, and control the feed flow rate of the metering pump so that the extraction and water washing volume ratio is: reaction solution-n-butyraldehyde-water is 1:2:1;

[0010] Step 4: The obtained water-washed oil phase is distilled in a distillation tower, and part of the n-butyraldehyde is recycled as the extraction solvent. The distillation is stopped when the distillation temperature of the tower bottom rises to 85°C. The bottom liquid is returned to the first step of the condensation reaction to replace n-butyraldehyde for the feed reaction;

[0011] Step 5: The water phase obtained by extraction is evaporated under reduced pressure in an evaporator, and the evaporation temperature is controlled to be less than 80°C and the vacuum degree is 8KPa. When the water phase of the extraction is dehydrated to half of its volume, the evaporation is stopped and the evaporated water is taken out and returned to the extraction water washing to replace the pure water for reuse. The evaporation vacuum degree is controlled to be 3KPa. When the temperature in the evaporator reaches 80°C, the evaporation is stopped and the concentrated liquid is taken out to obtain the purified DMB for production and standby use;

[0012] Step 6: Repeat steps 1 to 5 multiple times, analyze the data and calculate the reaction conversion rate of DMB.

[0013] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step one, the formaldehyde content in the formaldehyde solution is 4.0 moles and is 2.0 moles relative to NBD, n-butyraldehyde is 2.0 moles, and trimethylamine is 0.1 mole and is 0.05 equivalent relative to NBD).

[0014] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step 1, the organic base catalyst used is trimethylamine, triethylamine and tripropylamine.

[0015] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step 1, the molar ratio of formaldehyde, n-butyraldehyde, and catalyst is 1.9-2.1:1:0.01-0.2.

[0016] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step three, the extractant used is preferably n-butyraldehyde.

[0017] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step three, the volume ratio of the extraction water wash used is: reaction solution-n-butyraldehyde-water is 1:1~2.5:0.5~2.

[0018] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step 4, the distillation evaporation temperature of the distillation tower is 50 to 80°C.

[0019] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step four, the distillation evaporation vacuum in the distillation tower is divided into two steps, the initial evaporation vacuum is 6 to 10 KPa (absolute pressure), and the second step evaporation vacuum is 3 to 6 KPa (absolute pressure).

[0020] According to a method for preparing dimethylolbutyraldehyde in an embodiment of the present application, in step three, the n-butyraldehyde extraction can effectively separate the unreacted raw materials and the incompletely reacted intermediate products and return them to the aldol condensation reaction.

[0021] According to a method for preparing dihydroxymethylbutyraldehyde in an embodiment of the present application, in step three, the degree of extraction and water washing is at least four levels, and the water-washed oil phase obtained by water washing mainly contains relatively large substances such as formaldehyde, NBD, MMD, ECR, etc., and after a part of n-butyraldehyde is distilled out, it is returned to step one for condensation reaction, and the extracted water phase mainly contains relatively small substances such as DMB and organic base catalyst.

[0022] Beneficial effects of this application:

[0023] 1. This method uses a reaction system that couples the aldol condensation reaction with separation methods such as extraction separation and evaporation separation, which increases the DMB conversion efficiency by 20-50 percent and effectively improves the selectivity of the reaction.

[0024] 2. The by-products MMD, ECR and raw material NBD produced during the DMB synthesis process of this method have different distribution ratios with DMB in the organic solvent. The reaction solution can be separated into the synthesized DMB, by-products MMD, ECR, etc. by solvent extraction, and these by-products are then returned to the condensation system for reaction.

[0025] Summary: This method is based on the US patent US6171971, and the main reaction process of 2,2-dimethylol n-butyraldehyde is as shown in the attached specification. Figure 3 , 4 5, and during the preparation process, the intermediate product MMB will also undergo side reactions, dehydration to form 2-ethylacrolein, the stop reaction is also reversible, and n-butyraldehyde itself will also undergo aldol condensation reaction to form 2-ethyl-3-hydroxyhexanal. From the above, it can be seen that n-butyraldehyde and formaldehyde have more condensation side reactions. Only by separating the reaction product DMB from the reaction liquid can the reaction to form DMB be effectively improved;

[0026] The dimethylolbutyraldehyde obtained by the method of the present invention has high selectivity and high yield, the selectivity is 92-94%, the yield is more than 80% (based on the mass of normal butyraldehyde), and the reaction is mild. Since the catalyst is insoluble in the solvent and the active component is not lost, no formate is generated. High-purity dimethylolbutyraldehyde can be obtained by simple separation, and can be used for direct hydrogenation to prepare trimethylolpropane or oxidation to prepare dimethylolbutyric acid.

[0027] Therefore, through the above two operations, a new reaction system can be used to prepare dimethylolbutyraldehyde, and the conversion efficiency of DMB in the preparation of dimethylolbutyraldehyde can be improved. The synthesized DMB and other by-products can be separated by solvent extraction. The reaction liquid is separated after the condensation reaction of these by-products to effectively improve the reaction to form DMB, which increases the conversion efficiency. The DMB yield efficiency is high and is more conducive to the synthesis of downstream processes. At the same time, after a large number of by-products are separated, by-products with no economic value will disappear or be converted into products with economic benefits, which effectively increases the economic benefits of products and by-products after the preparation of dimethylolbutyraldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a bar chart comparing the data content of GC analysis results in two methods for preparing dimethylolbutyraldehyde in the present invention;

[0030] Figure 2 A bar chart comparing the conversion rate data content in two methods for preparing dimethylolbutyraldehyde in the present invention;

[0031] Figure 3 It is a reaction equation diagram of the first part of the main reaction process of 2,2-dimethylol n-butyraldehyde in the present invention;

[0032] Figure 4 It is a reaction equation diagram of the second part of the main reaction process of 2,2-dimethylol n-butyraldehyde in the present invention;

[0033] Figure 5 It is a reaction equation diagram of the second part of the main reaction process of 2,2-dimethylol n-butyraldehyde in the present invention;

[0034] Figure 6 It is a curve chart of the purified DMB content when preparing dimethylolbutyraldehyde in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0036] In order to make the purpose, technical solutions and advantages of the implementation methods of this application clearer, the technical solutions in the implementation methods of this application will be clearly and completely described below in conjunction with the drawings in the implementation methods of this application. Obviously, the described implementation methods are part of the implementation methods of this application, not all of the implementation methods. Based on the implementation methods in this application, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] A method for preparing dimethylolbutyraldehyde and a method for producing dimethylolbutyraldehyde according to an embodiment of the present application are described below with reference to the accompanying drawings, and include two methods for calculating the reaction conversion rate of DMB in the preparation of dimethylolbutyraldehyde.

[0038] Embodiment 1,

[0039] According to a method for preparing dimethylolbutyraldehyde according to an embodiment of the present application, the method comprises the following steps:

[0040] Step 1, add 324 grams of 37% formaldehyde solution (4.0 moles of formaldehyde, 2.0 equivalents relative to NBD) into a 1L reactor and start stirring, and evenly add 144 grams of n-butyraldehyde (2.0 moles of n-butyraldehyde) and 59 grams of 10% trimethylamine solution (0.1 mole of trimethylamine, 0.05 equivalents relative to NBD) into the reactor, and control the dropping speed to 2 hours. During the dropping process, control the reaction temperature at 35-40°C with a water bath. After the dropping is completed, heat the temperature to 40-45°C and keep the reaction for 3 hours.

[0041] Step 2: Use formic acid to neutralize the pH of the reaction solution to pH 6.0-7.0

[0042] Step 3: Use a continuous four-stage countercurrent extraction and four-stage countercurrent water washing test tank to extract and wash the obtained reaction liquid with n-butyraldehyde and pure water, and control the feed flow rate of the metering pump so that the extraction and washing volume ratio is: reaction liquid-n-butyraldehyde-water is 1:2:1.

[0043] Step 4: The obtained water-washed oil phase is rectified in a rectification tower, and part of the n-butyraldehyde is recycled as an extraction solvent. The rectification is stopped when the tower bottom distillation temperature rises to 85° C. The tower bottom liquid is returned to the first step condensation reaction to replace n-butyraldehyde for feeding reaction.

[0044] Step 5, the aqueous phase obtained by extraction is evaporated under reduced pressure in an evaporator, and the evaporation temperature is controlled to be less than 80°C and the vacuum degree is 8KPa. When the extracted aqueous phase is dehydrated to half of its volume, the evaporation is stopped and the evaporated water is taken out and returned to the extraction water washing instead of pure water for reuse. In the second step, the evaporation vacuum degree is controlled to be 3KPa. When the temperature in the evaporator reaches 80°C, the evaporation is stopped and the concentrated liquid is taken out to obtain the purified DMB for production and standby use.

[0045] Step 6: Repeat the above steps several times to calculate the reaction conversion rate.

[0046] Embodiment 2,

[0047] According to a method for preparing dimethylolbutyraldehyde according to an embodiment of the present application, the method comprises the following steps:

[0048] Step 1, add 308 grams of 37% formaldehyde solution (3.8 moles of formaldehyde, 2.0 equivalents relative to NBD) into a 1L reactor and start stirring, and evenly add 144 grams of n-butyraldehyde (2.0 moles of n-butyraldehyde) and 94 grams of 10% trimethylamine solution (0.16 moles of trimethylamine, 0.08 equivalents relative to NBD) into the reactor, and control the dropping speed to 2 hours. During the dropping process, the reaction temperature is controlled at 35-40°C with a water bath. After the dropping is completed, the temperature is raised to 40-45°C and the reaction is kept warm for 3 hours.

[0049] Step 2: Use formic acid to neutralize the pH of the reaction solution to pH 6.0-7.0

[0050] Step 3: Use a continuous four-stage countercurrent extraction and four-stage countercurrent water washing test tank to extract and wash the obtained reaction liquid with n-butyraldehyde and pure water, and control the feed flow of the metering pump so that the extraction and washing volume ratio is: reaction liquid-n-butyraldehyde-water is 1:2.5:1.5.

[0051] Step 4: The obtained water-washed oil phase is rectified in a rectification tower, and part of the n-butyraldehyde is recycled as an extraction solvent. The rectification is stopped when the tower bottom distillation temperature rises to 85° C. The tower bottom liquid is returned to the first step condensation reaction to replace n-butyraldehyde for feeding reaction.

[0052] Step 5, the aqueous phase obtained by extraction is evaporated under reduced pressure in an evaporator, and the evaporation temperature is controlled to be less than 80°C and the vacuum degree is 8KPa. When the extracted aqueous phase is dehydrated to half of its volume, the evaporation is stopped and the evaporated water is taken out and returned to the extraction water washing instead of pure water for reuse. In the second step, the evaporation vacuum degree is controlled to be 3KPa. When the temperature in the evaporator reaches 80°C, the evaporation is stopped and the concentrated liquid is taken out to obtain the purified DMB for production and standby use.

[0053] Step 6: Repeat the above steps several times to calculate the reaction conversion rate.

[0054] In addition to the above two embodiments, further, in step 1, the formaldehyde content in the formaldehyde solution is 4.0 moles and is 2.0 moles relative to NBD, the butyraldehyde is 2.0 moles, and the trimethylamine is 0.1 mole and is 0.05 equivalent relative to NBD).

[0055] In addition to the above two embodiments, in step 1, the organic base catalyst used is trimethylamine, triethylamine and tripropylamine.

[0056] In addition to the above two embodiments, in step 1, the molar ratio of formaldehyde, n-butyraldehyde and catalyst is 1.9-2.1:1:0.01-0.2.

[0057] In addition to the above two embodiments, in step three, the extractant used is preferably n-butyraldehyde.

[0058] In addition to the above two embodiments, in step three, the volume ratio of the extraction water wash used is: reaction solution-n-butyraldehyde-water is 1:1~2.5:0.5~2.

[0059] In addition to the above two embodiments, further, in step 4, the distillation evaporation temperature of the distillation tower is 50-80°C.

[0060] To supplement the above two embodiments, further, in step 4, the distillation evaporation vacuum of the distillation tower is divided into two steps, the initial evaporation vacuum is 6 to 10 KPa (absolute pressure), and the second step evaporation vacuum is 3 to 6 KPa (absolute pressure).

[0061] In addition to the above two embodiments, in step three, the n-butyraldehyde extraction can effectively separate the unreacted raw materials and the incompletely reacted intermediate products and return them to the aldol condensation reaction.

[0062] In addition to the above two embodiments, in step three, the degree of extraction and water washing is at least four levels, and the water-washed oil phase obtained by water washing mainly contains relatively large formaldehyde, NBD, MMD, ECR and other substances, and after part of n-butyraldehyde is distilled out, it returns to step one for condensation reaction, and the extracted water phase mainly contains relatively small DMB and organic base catalyst.

[0063] According to the operation of the above two embodiments, the GC analysis results of the obtained DMB concentrated solution and the calculation results of the yields of TMP and DMB produced by the reaction based on the raw material NBD are shown in the following table.

[0064]

[0065] It can be seen from the above table that in the two improved embodiments, the conversion rates of DMB are both higher than 90%, and the DMB conversion rate data of embodiment 1 is higher after multiple operations, so embodiment 1 can be selected for operation.

[0066] And the important component NBD in the table is introduced: Dicycloheptadiene is an organic compound with the chemical formula C7H8. It is toxic. If there is a leak, you need to cut off the fire source, wear a self-contained breathing apparatus, and wear general fire protection clothing. Seal the leak under safe conditions. Spraying water mist can reduce evaporation. Mix with sand or other non-flammable adsorbents for absorption. Then transport it to an open place for burial, evaporation, or incineration. If there is a large amount of leakage, use a dike to contain it, and then collect, transfer, recycle or dispose of it harmlessly.

[0067] The method adopts a reaction system that couples the aldol condensation reaction with separation methods such as extraction separation and evaporation separation, which increases the DMB conversion efficiency by 20-50%, effectively improving the selectivity of the reaction. In addition, the byproducts MMD, ECR and raw material NBD generated during the DMB synthesis process of the method have a different distribution ratio from that of DMB in the organic solvent. The reaction solution can be separated by solvent extraction to obtain the synthesized DMB, byproducts MMD, ECR, etc., and these byproducts are then returned to the condensation system for reaction.

[0068] The main reaction process of 2,2-dihydroxymethyl n-butyraldehyde is as shown in the attached manual. Figure 3 , 4 5, and during the preparation process, the intermediate product MMB will also undergo side reactions, dehydration to form 2-ethylacrolein, the stop reaction is also reversible, and n-butyraldehyde itself will also undergo aldol condensation reaction to form 2-ethyl-3-hydroxyhexanal. From the above, it can be seen that n-butyraldehyde and formaldehyde have more condensation side reactions. Only by separating the reaction product DMB from the reaction liquid can the reaction to form DMB be effectively improved;

[0069] The dimethylolbutyraldehyde obtained by the method of the present invention has high selectivity and high yield, the selectivity is 92-94%, the yield is more than 80% (based on the mass of normal butyraldehyde), and the reaction is mild. Since the catalyst is insoluble in the solvent and the active component is not lost, no formate is generated. High-purity dimethylolbutyraldehyde can be obtained by simple separation, and can be used for direct hydrogenation to prepare trimethylolpropane or oxidation to prepare dimethylolbutyric acid.

[0070] Therefore, through the above two operations, a new reaction system can be used to prepare dimethylolbutyraldehyde, and the conversion efficiency of DMB in the preparation of dimethylolbutyraldehyde can be improved. The synthesized DMB and other by-products can be separated by solvent extraction. The reaction liquid is separated after the condensation reaction of these by-products to effectively improve the reaction to form DMB, which increases the conversion efficiency. The DMB yield efficiency is high and is more conducive to the synthesis of downstream processes. At the same time, after a large number of by-products are separated, by-products with no economic value will disappear or be converted into products with economic benefits, which effectively increases the economic benefits of products and by-products after the preparation of dimethylolbutyraldehyde.

[0071] The above are only embodiments of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0072] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing dimethylolbutyraldehyde, characterized in that: The dimethylolbutyraldehyde preparation method comprises: Step 1: Add 324 g of 37% formaldehyde solution into a 1L reactor and start stirring, then uniformly drop 144 g of n-butyraldehyde and 59 g of 10% organic base catalyst aqueous solution into the reactor, control the dropping speed to 2 hours, and control the reaction temperature at 35-40°C with a water bath during the dropping process. After the dropping is completed, heat to 40-45°C and keep the reaction for 3 hours; Step 2: neutralize the pH of the reaction solution to pH 6.0-7.0 with formic acid; Step 3: Use a continuous four-stage countercurrent extraction and four-stage countercurrent water washing test tank to extract and wash the obtained reaction solution with n-butyraldehyde and pure water, and control the feed flow rate of the metering pump so that the extraction and water washing volume ratio is: reaction solution-n-butyraldehyde-water is 1:2:1; Step 4: The obtained water-washed oil phase is distilled in a distillation tower, and part of the n-butyraldehyde is recycled as an extraction solvent. When the distillation temperature of the tower bottom rises to 85°C, the distillation is stopped, and the bottom liquid is returned to the first step of the condensation reaction to replace the n-butyraldehyde for the feed reaction; Step 5: The water phase obtained by extraction is evaporated under reduced pressure in an evaporator, and the evaporation temperature is controlled to be less than 80°C and the vacuum degree is 8KPa. When the water phase of the extraction is dehydrated to half of its volume, the evaporation is stopped and the evaporated water is taken out and returned to the extraction water washing to replace the pure water for reuse. The evaporation vacuum degree is controlled to be 3KPa. When the temperature in the evaporator reaches 80°C, the evaporation is stopped and the concentrated liquid is taken out to obtain the purified DMB for production and standby use; Step 6: Repeat steps 1 to 5 multiple times, analyze the data and calculate the reaction conversion rate of DMB.

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