Preparation of triisopropanolamine_industrial additives

Background and overview^[1][2]

Triisopropanolamine is a white or light yellow waxy crystalline solid that is easily soluble in water, ethanol, diethanol and acetone. Since the molecule contains both amine and hydroxyl groups at the same time, it has the combined effect of amine and alcohol. Performance, it is widely used as surfactant in industry.

Triisopropanolamine is mostly prepared by the reaction of pure ammonia and propylene oxide. At present, it is generally produced at home and abroad by the intermittent reaction of 25% saturated ammonia water and propylene oxide. Water acts as a catalyst and does not act as a solvent. The formula is as follows:

At the same time, the water in ammonia also produces the following side reactions with propylene oxide, producing by-products propylene glycol and propylene glycol propylamino ether:

It can be seen from the above reaction that during the reaction between ammonia (NH3) and propylene oxide, monoisopropanolamine, diisopropanolamine and triisopropanolamine will be generated in sequence. If the molar ratio of the reactants is not consistent with the reaction process, If controlled, propylene glycol and propylene glycol oxyether by-products will also be produced. If you want to use triisopropanolamine as the target product, the ratio of NH3 and propylene oxide should be strictly controlled to ensure the purity of the product; because the reaction speed of pure ammonia and propylene oxide is extremely slow, a catalyst needs to be added for catalysis. In this reaction, water serves as both a catalyst and a solvent.

Domestic production technologies are: the reaction of saturated ammonia water 25-28% (m/m) with propylene oxide to produce the target product, but the generated product has a large water content and the final product concentration is low, requiring a large amount of removal water requires a large amount of heat energy, so the energy consumption is high. Most foreign companies use 60-90% ammonia solution as raw material for continuous production. The reaction pressure is 6-8Mpa, which requires high-pressure equipment. The investment in production equipment is large and the process is complicated.

Grinding aids are additives used in the cement clinker grinding process, which can significantly improve grinding efficiency or reduce energy consumption. Cement grinding aids are mainly based on alcohol amines, usually including triethanolamine, triisopropanolamine, methyldiethanolamine, tetrahydroxyethylethylenediamine, diethanolmonoisopropanolamine, and diisopropanolmonoethanolamine. wait. Among them, triethanolamine was used earlier and has a wider range of use. Compared with triethanolamine, triisopropanolamine has strong dispersion properties due to its three-dimensional molecular structure, and its later strength is better than triethanolamine. The range gradually increases. .

Physical and chemical properties and structure^[1]

Triisopropanolamine is a white or slightly yellow solid at room temperature. Its scientific name is 1,1′,1″-nitriloyl tripropan-2-ol, and its chemical formula is (CH3CHOHCH2)3N. Triisopropanol Amines have a wide range of uses and can be used as auxiliary fillers in the rubber industry; they can be used as chain terminators for certain polymerization reactions; they can be used as raw materials for various cosmetic creams, wool fabrics and wool detergents; they can be used in fiber oils , cutting oil and latex paint; can be used for the synthesis of drugs and new polymer materials. The zincate zinc plating additive prepared from triisopropanolamine can also be used in the cyanide-free electroplating process to make the electroplated layer smooth, bright and firmly adhered. And corrosion-resistant.

Project�In industry, ammonia or liquid ammonia and propylene oxide are usually used as raw materials to synthesize triisopropanolamine. The products synthesized by this method contain monoisopropanolamine, diisopropanolamine and triisopropanolamine. The mixture needs to be separated again, but the separation is difficult and the energy consumption is high. The purity of the finally separated triisopropanolamine is not high. Moreover, when the temperature reaches above 170°C during the synthesis and separation process, the triisopropanolamine will Propanolamine will decompose, which will affect the purity and quality of the product. The product is generally slightly yellow or yellow. In addition, existing commercially available triisopropanolamine products will slowly oxidize at room temperature and are hygroscopic. They are also prone to color changes and increased water content during storage and use.

Triisopropanolamine

Preparation ^[2]

Method 1:

Follow the following steps to prepare triisopropanolamine:

(1) In terms of parts by weight, first prepare 1 part of liquid ammonia into an ammonia solution with a concentration of 22% and inject it into the reaction vessel. Replace it with nitrogen three times. The side oxygen content is <150ppm. Then add 8 parts of propylene oxide. It is directly pressurized by 0.2mpa from the metering tank and enters the reaction vessel to react with the ammonia solution;

(2) Use the external circulation pump to move the materials out of the reaction vessel, cool down the reaction temperature through the heat exchanger, and then spray them into the reaction vessel through the static atomization injector installed in the reaction vessel to accelerate the reaction of the materials, for 6 hours After the reaction is completed, a stock solution of triisopropanolamine is obtained, wherein the temperature in the reaction vessel is 70°C and the reaction is carried out under vacuum;

(3) The prepared triisopropanolamine stock solution enters the distillation kettle, and the water in the stock solution is evaporated to produce triisopropanolamine.

Method 2:

Prepare 100Kg of liquid ammonia into an ammonia solution with a mass concentration of 15% and inject it into the reaction vessel. Then 1020Kg propylene oxide is directly pressurized from the metering tank and enters the reaction vessel through the feed pipe extending into the reaction vessel. At the same time, the circulation pump 5 is started to remove the material in the reaction vessel 1. After being cooled by the heat exchanger 4 , and then sprayed into the reaction vessel through the atomization injector 3 in the reaction vessel, and then operated in a continuous cycle to obtain triisopropanolamine stock solution. The entire reaction time is about 2 hours, the temperature in the reaction vessel 1 is about 70°C, and the reaction pressure is ≤0.2MPa. After feeding propylene oxide, the material continues to be circulated and the reaction temperature is maintained for 0.5 to 1.5 hours. That is, the original solution of triisopropanolamine is obtained, and the excess water is removed by distillation to obtain a product containing 80% of triisopropanolamine.

Main reference materials

[1] Shi Caijun, Liu Hui, Li Pingliang, & He Fuqiang. (2011). Effect of triisopropanolamine on the hydration mechanism and microstructure of limestone Portland cement. Journal of Ceramics, 39 (10), 1673-1681.

[2] Cheng Guangbin, & Zhang Shu. (2008). Development status and prospects of isopropanolamine industry. Acetaldehyde Acetic Acid Chemical Industry (1), 3-4.

[3] Yang Changhui, Wang Qiao, & Huang Hong. (2018). Effect of So_3 content on hydration of triisopropanolamine-containing cement. Silicate Bulletin, 37(7).