A method for preparing trimethylolpropane product with improved calcium method

Abstract

A preparation method capable of improving the product quality of calcium method trimethylolpropane, comprising the following contents: 1) condensation reaction: hydroxy aldehyde condensation disproportionation reaction of formaldehyde and n-butyl aldehyde in process water under the alkaline environment of calcium hydroxide, at the end of the condensation reaction, residual formaldehyde in the condensation reaction liquid is oxidized by hydrogen peroxide, then formic acid is added to adjust the pH value of the condensation liquid to 6.4-6.5, then carbon dioxide is added to completely neutralize the residual alkaline substances in the condensation reaction liquid, so that the condensation reaction liquid is reversibly slightly acidic, and the pH value decreases to 5.8-6.0; a flocculating agent is added; impurity calcium residues are removed by filtration; 2) evaporation and concentration; 3) calcium formate centrifugal separation; 4) extraction; and 5) rectification. The alkaline substances remaining in the condensation reaction are neutralized by carbon dioxide to generate precipitates for separation, and the pH value of the system material is controlled, thereby reducing the occurrence of subsequent refining process side reactions, solving the problem of product quality fluctuation of calcium method trimethylolpropane, and improving the product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a preparation method capable of improving the quality of calcium-process trimethylolpropane products. Background Art

[0002] Currently, the calcium-based trimethylolpropane production process requires the addition of excessive formic acid to neutralize residual alkalinity in the condensation reaction solution. This results in a low pH value for the system material, affecting the acidity of the trimethylolpropane product. Furthermore, during the subsequent evaporation and extraction separation stages, the system material contains aldehydes and residual alkalinity, which circulate at high temperatures of 75-85°C, causing side reactions that affect product quality.

[0003] The quality of trimethylolpropane products produced by the existing calcium-based trimethylolpropane production process is unstable. Therefore, it is urgent to explore the factors affecting the quality of calcium-based trimethylolpropane products and provide a preparation method that can improve the quality of calcium-based trimethylolpropane products, so as to solve the problem of quality fluctuation of calcium-based trimethylolpropane products and improve product quality. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a preparation method for calcium-process trimethylolpropane product that can improve the quality of the product, thereby solving the problem of quality fluctuation of calcium-process trimethylolpropane product and improving product quality.

[0005] The object of the present invention is achieved through the following technical solution: a preparation method for improving the quality of calcium-process trimethylolpropane products, comprising the following contents:

[0006] 1) Condensation reaction:

[0007] Formaldehyde and n-butyraldehyde undergo aldol condensation disproportionation reaction in process water under the alkaline environment of calcium hydroxide to prepare trimethylolpropane solution. The mass ratio of formaldehyde, n-butyraldehyde and calcium hydroxide is 3.1-3.3:1:0.64. The condensation reaction is carried out at a constant temperature of 40℃-45℃ for 20-60 minutes. The reaction termination temperature is controlled at 40℃-45℃. At the end of the condensation reaction, the residual formaldehyde in the condensation reaction liquid is first oxidized by hydrogen peroxide, and the neutralization temperature is controlled at 42℃-4 5°C, then adding formic acid to adjust the pH value of the condensation liquid to 6.4-6.5, and after adding carbon dioxide, the residual alkaline substances in the condensation reaction liquid are completely neutralized, making the condensation reaction liquid reversibly slightly acidic, and the pH value drops to 5.8-6.0; then adding a flocculant to flocculate insoluble impurities, and heating the condensation reaction liquid to control the temperature at 55°C-65°C; then filtering to remove impurities and calcium residues in the condensation reaction liquid, and the pH value of the condensation reaction liquid is increased to 6.4-6.5;

[0008] 2) Evaporation and concentration;

[0009] 3) Centrifugal separation of calcium formate;

[0010] 4) Extraction;

[0011] 5) Distillation.

[0012] The step 2) evaporation concentration comprises: adding the condensation reaction liquid having a water volume content of 85%-90% into a three-effect evaporator, wherein the vacuum of each evaporator is less than 70 kPa and the temperature is less than 95° C., and the water content of the trimethylolpropane and calcium formate concentrate produced from the first effect is controlled to be 30%-50%.

[0013] The step 3) centrifugal separation of calcium formate comprises: injecting the concentrated liquid containing calcium formate solid after evaporation into a sedimentation tank, and the concentrated clear liquid without solid particles on the top overflows into the subsequent extraction section; the solid calcium formate settles to the bottom of the sedimentation tank under the influence of gravity, and the turbid liquid at the bottom of the sedimentation tank is separated into solid and liquid using a horizontal spiral centrifuge. After separation, the calcium formate wet material is then air-dried and packaged; and the mother liquor after solid-liquid separation returns to the evaporation and concentration step.

[0014] The step 4) extraction comprises: performing reverse extraction with the overflow clear liquid and the extractant in a volume ratio of 1:3, controlling the extraction temperature at 60° C.-85° C., the extract liquid entering the subsequent solvent recovery section, and the raffinate entering the raffinate settling tank for cooling and settling, controlling the settling temperature at 25° C.-40° C., sampling and observing the state of the raffinate, and filtering the material using a plate filter after it becomes turbid and has precipitated particles, and discharging the filtered residue. The filtered clear liquid is decolorized by activated carbon and then reused in the evaporation and concentration step.

[0015] The step 5) distillation comprises: feeding the extract into a solvent recovery tower with an internal temperature of 160° C.-190° C. and a vacuum degree of <40 kPa to recover the solvent; cooling the separated extractant and recycling it to the extraction section; and feeding the bottom material containing 60%-80% trimethylolpropane into a subsequent distillation tower for refining and purification. The distillation tower adopts top condensation, and the trimethylolpropane content of the finished product extracted from the tower is ≥99.0%. The bottom material of the tower enters the subsequent ditrihydroxy system.

[0016] The beneficial effects of the present invention are as follows: in the late stage of the neutralization stage of the condensation reaction, the present invention uses carbon dioxide to neutralize the alkaline substances remaining in the condensation reaction to generate a precipitate for separation, while controlling the pH value of the system material, thereby reducing the occurrence of side reactions in the subsequent refining process, solving the quality fluctuation problem of the calcium-process trimethylolpropane product, and effectively improving the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart of the method of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings.

[0019] Example 1 Condensation reaction experiment.

[0020] 1. Experimental part:

[0021] 1. Formaldehyde and n-butyraldehyde undergo an aldol condensation disproportionation reaction in process water in the presence of calcium hydroxide to produce a trimethylolpropane solution. The mass ratio of formaldehyde, n-butyraldehyde, and calcium hydroxide is 3.3:1:0.64. The condensation reaction is maintained at a constant temperature for 40 minutes, with the reaction termination temperature controlled at 45°C. After the condensation reaction is completed, hydrogen peroxide is added to oxidize the residual aldehydes in the condensation reaction solution, and the temperature is controlled at 45°C.

[0022] 2. After the oxidation is completed, add formic acid to control the pH value of the condensation reaction solution to 6.5;

[0023] 3. Carry out the following three experiments:

[0024] Experiment 1: After the pH value is constant at 6.5, formic acid is continuously added to completely neutralize the residual alkaline substances in the condensation reaction solution, making the condensation reaction solution reversibly slightly acidic, and controlling the pH value to drop to 5.8-6.0;

[0025] Experiment 2: After the pH value is constant at 6.5, carbon dioxide is added to completely neutralize the residual alkaline substances in the condensation reaction solution, making the condensation reaction solution reversibly slightly acidic, and controlling the pH value to drop to 5.8-6.0;

[0026] Experiment 3: After the pH value was constant at 6.5, carbon dioxide was added to completely neutralize the residual alkaline substances in the condensation reaction solution, making the condensation reaction solution reversibly slightly acidic, and controlling the pH value to drop to 5.5-5.6;

[0027] 4. Add flocculant to flocculate insoluble impurities, and raise the pH of the condensation reaction solution to 6.5 by heating and filtering.

[0028] 2. Data Analysis

[0029] The status analysis of the test samples is shown in Table 1.

[0030] Table 1

[0031] Material Name Neutralizing substances pH value after neutralization Material color number Material status Test 1 Formic acid 5.8-6.0 #12-#13 Clear and transparent Test 2 Appropriate amount of carbon dioxide 5.8-6.0 #9-#10 Clear and transparent Test 3 Excess carbon dioxide 5.5-5.6 #9-#10 Clear and transparent

[0032] Through experimental analysis, it can be seen that by comparing the material states of the condensation reaction liquid neutralized by carbon dioxide and the condensation reaction liquid neutralized by formic acid: the color number of the condensation reaction liquid is significantly reduced and it is clearer and more transparent.

[0033] Chromatographic analysis of the test samples is shown in Table 2.

[0034] Table 2

[0035] Serial number Methanol% n-Butyraldehyde% 2-Ethyl acrolein% Light component 1% CTF% Trihydroxy% Ditrihydroxy% Other Peak % Total Test 1 2.21 0.07 0.81 1.78 0.49 85.44 5.34 3.86 Test 2 1.94 0.09 0.77 1.78 0.48 85.75 5.29 3.90 Test 3 1.98 0.08 0.80 1.78 0.48 85.82 5.26 3.80

[0036] Through the above data analysis, it can be seen that neutralization of the condensation reaction liquid with formic acid or carbon dioxide has no obvious effect on the components of the condensation reaction liquid.

[0037] 3. Theoretical Analysis

[0038] 1. In the late stage of the neutralization stage of the condensation reaction, carbon dioxide is added to fully contact and mix with the condensation reaction liquid, which can completely neutralize the residual alkaline substances in the condensation reaction liquid. This solves the problem in the original process that excessive formic acid needs to be added to neutralize the residual alkaline substances in the condensation reaction liquid, resulting in a low pH value of the system material and affecting the acid value of the trimethylolpropane product.

[0039] 2. Carbon dioxide is added in the late stage of the condensation neutralization stage to completely neutralize the alkaline substances in the condensation reaction liquid, making the system materials reversibly slightly acidic. This solves the problem in the original process that aldehydes and residual alkaline substances in the system materials in the subsequent evaporation and extraction separation stages will circulate at a high temperature of 75-85°C to produce side reactions, affecting product quality.

[0040] Example 2 A preparation method capable of improving the quality of calcium-process trimethylolpropane products.

[0041] 1. Experimental part

[0042] 1) Condensation reaction:

[0043] Formaldehyde and n-butyraldehyde undergo aldol condensation disproportionation reaction in process water in an alkaline environment of calcium hydroxide to prepare trimethylolpropane solution. The mass ratio of formaldehyde, n-butyraldehyde, and calcium hydroxide is 3.1-3.3:1:0.64. The condensation reaction is carried out at a constant temperature of 40°C-45°C for 20-60 minutes, and the reaction termination temperature is controlled at 40°C-45°C. At the end of the condensation reaction, the residual formaldehyde in the condensation reaction liquid is first oxidized by hydrogen peroxide. The amount of hydrogen peroxide added is added according to the amount of residual formaldehyde in the condensation liquid after the condensation reaction is terminated. The process controls the residual formaldehyde index at 3.5±0.5g. / l, the neutralization temperature is controlled at 42°C-45°C, and then formic acid is added to adjust the pH value of the condensation liquid to 6.4-6.5. After adding carbon dioxide, the residual alkaline substances in the condensation reaction liquid are completely neutralized, making the condensation reaction liquid reversibly slightly acidic and the pH value dropped to 5.8-6.0; then 0.35kg-0.5kg of flocculant is added to each kettle to flocculate insoluble impurities, and the condensation reaction liquid is heated and the temperature is controlled at 55°C-65°C; then, the impurities calcium residue in the condensation reaction liquid are filtered to remove, and the pH value of the condensation reaction liquid is raised to 6.4-6.5;

[0044] 2) Evaporation concentration:

[0045] The condensation reaction liquid with a water volume content of 88% is added to the three-effect evaporator. The vacuum of each evaporator is less than 70Kpa and the temperature is less than 95℃. The water content of the trimethylolpropane and calcium formate concentrate produced from the first effect is controlled to be 50%.

[0046] 3) Centrifugal separation of calcium formate:

[0047] The concentrated liquid containing calcium formate solids after evaporation is injected into a sedimentation tank, and the concentrated clear liquid without solid particles on the top overflows and enters the subsequent extraction section; the solid calcium formate settles to the bottom of the sedimentation tank due to gravity, and the turbid liquid at the bottom of the sedimentation tank is separated into solids and liquids using a horizontal spiral centrifuge. After separation, the wet calcium formate is then air-dried and packaged; the mother liquor after solid-liquid separation returns to the evaporation and concentration step;

[0048] 4) Extraction:

[0049] The overflow clear liquid and the extractant are reversely extracted in a volume ratio of 1:3. The extraction temperature is controlled at 60°C-85°C. The extract enters the subsequent solvent recovery section. The raffinate enters the raffinate settling tank for cooling and sedimentation. The sedimentation temperature is controlled at 25°C-40°C. The raffinate state is observed by sampling. If the material is turbid and particles are precipitated, it is filtered using a plate filter. The filter residue is discharged for treatment. The filtered clear liquid is decolorized by activated carbon and then enters the evaporation and concentration step for reuse.

[0050] 5) Distillation:

[0051] The extract is fed into a solvent recovery tower with an internal temperature of 180°C and a vacuum degree of <40Kpa for solvent recovery. The separated extractant is cooled and recycled to the extraction section. The bottom material containing 78% trimethylolpropane enters a subsequent distillation tower for refining and purification. The distillation tower adopts top condensation. The content of trimethylolpropane in the finished product extracted from the tower is ≥99.0%. The bottom material enters the subsequent ditrihydroxy system.

[0052] 2. Results Analysis:

[0053] The experiment significantly improved the quality of trimethylolpropane products. The original acid value of trimethylolpropane products was 0.005%-0.010%, and the acid value after the experiment was 0.001%-0.003%, reaching the industry standard of ≤0.002%. The original trihydroxy content of trimethylolpropane products was 99.0%-99.1%, and after the experiment, the trihydroxy content was stabilized at above 99.15%, and the trihydroxy content of the product remained stable.

[0054] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing trimethylolpropane produced by a calcium process to improve its product quality, characterized in that Includes the following: 1) Condensation reaction: Formaldehyde and n-butyraldehyde undergo aldol condensation disproportionation reaction in process water under the alkaline environment of calcium hydroxide to prepare trimethylolpropane solution. The mass ratio of formaldehyde, n-butyraldehyde and calcium hydroxide is 3.1-3.3:1:0.

64. The condensation reaction is carried out at a constant temperature of 40℃-45℃ for 20-60 minutes. The reaction termination temperature is controlled at 40℃-45℃. At the end of the condensation reaction, the residual formaldehyde in the condensation reaction liquid is first oxidized by hydrogen peroxide, and the neutralization temperature is controlled at 42℃-4 5°C, then adding formic acid to adjust the pH value of the condensation liquid to 6.4-6.5, and after adding carbon dioxide, the residual alkaline substances in the condensation reaction liquid are completely neutralized, making the condensation reaction liquid reversibly slightly acidic, and the pH value drops to 5.8-6.0; then adding a flocculant to flocculate insoluble impurities, and heating the condensation reaction liquid to control the temperature at 55°C-65°C; then filtering to remove impurities and calcium residues in the condensation reaction liquid, and the pH value of the condensation reaction liquid is increased to 6.4-6.5; 2) Evaporation and concentration; 3) Centrifugal separation of calcium formate; 4) Extraction; 5) Distillation.

2. The method for preparing calcium-process trimethylolpropane (TMP) according to claim 1, wherein: The step 2) evaporation concentration comprises: adding the condensation reaction liquid having a water volume content of 85%-90% into a three-effect evaporator, wherein the vacuum of each evaporator is less than 70 kPa and the temperature is less than 95° C., and the water content of the trimethylolpropane and calcium formate concentrate produced from the first effect is controlled to be 30%-50%.

3. The method for preparing calcium-process trimethylolpropane (TMP) according to claim 1, wherein: The step 3) centrifugal separation of calcium formate comprises: injecting the concentrated liquid containing calcium formate solid after evaporation into a sedimentation tank, and the concentrated clear liquid without solid particles on the top overflows into the subsequent extraction section; the solid calcium formate settles to the bottom of the sedimentation tank under the influence of gravity, and the turbid liquid at the bottom of the sedimentation tank is separated into solid and liquid using a horizontal spiral centrifuge. After separation, the calcium formate wet material is then air-dried and packaged; and the mother liquor after solid-liquid separation returns to the evaporation and concentration step.

4. The method for preparing calcium-process trimethylolpropane (TMP) according to claim 1, wherein: The step 4) extraction comprises: performing reverse extraction with the overflow clear liquid and the extractant in a volume ratio of 1:3, controlling the extraction temperature at 60° C.-85° C., the extract liquid enters the subsequent solvent recovery section, the raffinate enters the raffinate settling tank for cooling and settling, and controlling the settling temperature at 25° C.-40° C., sampling and observing the state of the raffinate, and filtering the material using a plate filter after it becomes turbid and has precipitated particles, and discharging the filtered residue. The filtered clear liquid is decolorized by activated carbon and then enters the evaporation and concentration step for reuse.

5. The method for preparing calcium-process trimethylolpropane (TMP) according to claim 1, wherein: The step 5) distillation comprises: feeding the extract into a solvent recovery tower with an internal temperature of 160° C.-190° C. and a vacuum degree of <40 kPa to recover the solvent; cooling the separated extractant and recycling it to the extraction section; and feeding the bottom material containing 60%-80% trimethylolpropane into a subsequent distillation tower for refining and purification. The distillation tower adopts top condensation, and the trimethylolpropane content of the finished product extracted from the tower is ≥99.0%. The bottom material of the tower enters the subsequent ditrihydroxy system.

Images