Report I:
A process method for continuous production of 2,2-Bis (hydroxymethyl) butyric acid using a microreactor includes the following steps:
S1. Measure a certain amount of formaldehyde, butyraldehyde and triethylamine with a metering pump and place them in the mixer for forced mixing, and then enter the micro-reactor for condensation reaction. The flow rates of triethylamine, formaldehyde and n-butyraldehyde are 250ml/min, 2000ml/min and 1100ml/min respectively. The flow rates of triethylamine, formaldehyde and n-butyraldehyde are 0.1m/s, the reaction temperature is 50 ℃, the pressure is 0.2MPa, and the reaction residence time is 70 seconds, The mixer is connected with three metering pumps and a micro-reactor. The materials of the mixer and micro-reactor can be any one or more of glass, stainless steel, resin and silicon carbide. The micro-reactor can be one or more in series. The micro-reactor is installed with a heat exchanger inside to obtain the reaction liquid mainly containing 2,2-dihydroxymethylbutyraldehyde;
S2. The reaction solution mainly containing 2,2-dihydroxymethylbutyraldehyde obtained from S1 is continuously distilled and concentrated through a thin film rotary evaporator, and the low-boiling matter is recycled and applied to obtain the concentrated solution of 2,2-dihydroxymethylbutyraldehyde;
S3. Then pump hydrogen peroxide into the micro-reactor containing the concentrated solution of dimethylol butyraldehyde through a metering pump for oxidation reaction. The flow rate of hydrogen peroxide for oxidation reaction is 1200 ml/min, the residence time is 360 seconds, and the pressure is 0.2 MPa to obtain the reaction solution of 2,2-dimethylol butyric acid;
S4. Take the reaction solution of 2,2-dihydroxymethylbutyric acid obtained in S3 and put it in a concentration kettle for concentration to obtain the concentrated solution of 2,2-dihydroxymethylbutyric acid, and then extract the concentrated solution of 2,2-dihydroxymethylbutyric acid three times with methyl isobutyl ketone, triethylamine and hydrogen peroxide can be recovered by low boiling, and methyl isobutyl ketone can be recovered by solvent, combined with the extracted solution, concentrated at atmospheric pressure, and then refrigerated and cooled, The separated product is centrifugally dried to obtain qualified 2,2-dihydroxymethylbutyric acid product.
Report II:
Preparation of activated carbon-supported alkali catalyst:
Add the activated carbon into 30% liquid alkali, stir for 24 hours, filter, dry the activated carbon, put it into a muffle furnace under the protection of nitrogen at 600 ℃, and activate for 5 hours, which is the catalyst.
Preparation of 2,2-dihydroxymethylbutyric acid:
Add 45g of formaldehyde, 72g of butyraldehyde and 3.6g of catalyst into the flask. After reaction at 50 ℃ for 10 hours, remove the catalyst by filtration. After the unreacted formaldehyde and butyraldehyde are evaporated, reduce to normal temperature. Add 72g of water, heat to 80 ℃, add 34g of hydrogen peroxide, react for 2 hours, evaporate the unreacted substances, and cool down to obtain white crystals, namely, 2,2-dimethylolbutyric acid.
Report III:
(1) Add 1000kg of water into the condensation kettle, add 12kg of soda ash and 5kg of sodium hydroxide, add 650kg of formaldehyde after mixing, cool to 10-15 ℃, add 240kg of n-butyraldehyde dropwise, and maintain a constant temperature for 16 hours after dropwise addition;
(2) Pump to the oxidation kettle, add formic acid water and, adjust the PH value to 6-7, reduce the pressure and concentration vacuum to -0.085MPa, recover n-butyraldehyde in the second stage, use water for cooling in the first stage, and use brine for cooling in the second stage.
(3) When the temperature rises to 50 ℃, add 500Kg of hydrogen peroxide by dropping. After dropping, keep the temperature at 60~62 ℃ for 4 hours and 70~72 ℃ for 4 hours;
(4) Maintain a vacuum of -0.060MPa for concentration, add 200Kg of water every 2 hours, add a total of 600Kg of water for azeotropic removal of formic acid, and recover 50% of the total amount of formic acid water for neutralization of soda ash and sodium hydroxide.
(5) Concentrate until the water content is below 1.0%, and add 100Kg of dichloroethane as diluent.
(6) After cooling, centrifuge and recover dichloroethane from mother liquor at atmospheric pressure.
(7) Primary refining: put methanol and crude products in the ratio of 1.5 ∶ 1, filter to remove insoluble substances, concentrate the filtrate, cool and crystallize, and obtain a high-quality product after centrifugation. The mother liquor of primary refining is treated with methyl isobutyl ketone.
(8) Secondary refining: put primary refined products and water in a ratio of 2:1, and cool them to recrystallize. The second best product of Lixinde. Apply the secondary refining mother liquor.
(9) Drying: control the temperature of the drying room at 80 ℃, cool it in the drying room after passing the moisture detection, and then take it out for crushing and screening.
(10) Put the primary refining mother liquor and methyl isobutyl ketone in the proportion of 5:1, cool and crystallize, and recover the product - 2.2 - dihydroxymethyl butyric acid by centrifugation, and then refine it again.
Report IV:
Add 96g of polyformaldehyde and 96g of water into a 1000ml four-necked flask, start the mixing, raise the temperature, add 80g of 5% liquid alkali at about 50 ° C, control the pH value between 910 and complete the dripping within 2 hours, continue the heat preservation reaction for 4 hours, raise the temperature to 80 ° C to recover the unreacted n-butyraldehyde and a small amount of formaldehyde solution, steam the internal temperature to 100 ° C, stop the distillation, lower the temperature, control the temperature at about 50 ° C, and slowly add 220g of 27% hydrogen peroxide, Control the completion of dripping within 2 hours. After the completion of dripping, the reaction is held for 6 hours. After adding concentrated sulfuric acid for acidification, reduce the pressure to 12 kPa and evaporate the water. After evaporation, add 200 grams of methyl isobutyl ketone, and then heat it up to 100 ℃ to separate the water. After the water is separated, cool it down. Filter the solid salt while it is hot, further cool the filtrate, and precipitate the crystals to obtain the crude product. Add the crude product into the solvent for recrystallization again to obtain white crystals, The total yield of 2,2-dimethylolbutyric acid was 41%.