Preparation method and distillation method of triethyl phosphate_Industrial additives

Background and overview^[1]

Triethyl phosphate is used in a wide range of applications, such as as an auxiliary in textiles and paper products, as a plasticizer in plastics and coatings, as a non-reactive flame retardant, as a hardener and accelerator, and as a lubricant. , flotation agent, defoaming agent, emulsifier, stabilizer or extraction agent.

Preparation^[1]

Continuous reactions are carried out in a jacketed cooling and stirring reactor group consisting of four jacketed cooling and stirring reactors each with a capacity of 2000 liters, which are connected to each other. The four jacketed cooling and stirring reactors use position difference and The transfer pump continuously transfers the esterification reaction products. All four jacketed cooling stirred reactors are equipped with reflux condensers and temperature-raising heat exchangers, which are connected to each other and to the -15°C cooling loop. The jacketed cooling and stirring reactor is also a jacketed cooling and stirring reaction vessel.

Through external cooling, the reaction temperature of the first jacketed cooling stirred reactor is controlled to 3-6°C, the reaction temperature of the second jacketed cooled stirred reactor is controlled to 13-18°C, and the reaction temperature of the third jacketed cooled stirred reactor is controlled The reaction temperature is 18-25°C. The fourth jacketed cooling stirred reactor controls the reaction temperature to 30-35°C. 517Kg/h ethanol and 384Kg/h phosphorus oxychloride are continuously added to the first stirred reactor. The jacketed cooling and stirring reaction kettle group and the storage tank are connected through a transfer pump, and are connected to the vacuum unit through the acrylic resin circulation column drop absorption group of the washing tower to ensure the vacuum degree of the esterification jacketed cooling and stirring reaction kettle group. The negative pressure is 700-720 mmHg. The materials in the first jacketed cooling and stirring reactor are measured by a circulating cooling pump and a rotor flowmeter, and then transferred to the second jacketed cooling and stirring reactor. The second jacketed cooling The stirred reaction kettle moves materials to the third jacketed cooling stirred reactor, the third jacketed cooling stirred reactor moves materials to the fourth jacketed cooling stirred reactor, and the reflux condenser condenses the mixture of ethanol and hydrogen chloride. Return to the stirred reaction kettle, and the remaining volatile components are passed into the washing tower circulation column and absorption group.

The washing tower is composed of regular packing and is combined with a falling film absorber. 1270Kg/h fresh water is washed and absorbed from the rear to the front. The temperature of the absorption liquid in the washing tower is controlled to 15-20°C.

When the equilibrium of the reactor is reached, the reaction product obtained in the storage tank is a mixture of 75% triethyl phosphate, 21% ethanol and 4% hydrogen chloride, which enters the degassing distillation tower for separation. The upper part of the degassing distillation tower is in addition to The gas tower, the middle part is the separation tower, and the bottom of the tower outputs materials mainly containing triethyl phosphate aqueous amino resin ester. The temperature of the degassing tower of the degassing distillation tower is controlled at 74°C and the negative pressure is 680-720°C mercury. 190Kg/h removes 90% weight of the mixture of ethanol and hydrogen chloride; the degassing tower of the degassing distillation tower is equipped with a condenser, and the temperature is controlled at 15-20°C. The rear condensate is recovered into the storage tank and returned to the first jacket cooling The reaction takes place in the stirred reaction kettle, so the non-volatile components enter the washing cycle column for absorption after passing through the degassing tower; the bottom temperature of the degassing distillation tower is controlled to 110-115°C, and the temperature at the bottom of the degassing distillation tower is The crude product was removed at 457Kg/h, which contained 98.5% 450Kg of triethyl phosphate.

The crude product is then purified by rectification. The top temperature of the rectification tower is controlled at 84°C, the negative pressure is controlled at 700-720 mmHg, and the bottom temperature of the rectification tower is controlled at 140-150°C. The temperature is 435Kg/h. 428 Kg of triethyl phosphate were recovered with a content of 99.99%, corresponding to a yield of 95%, based on the phosphorus oxychloride used. Discharge 22Kg of diethyl phosphate containing 67% content from the bottom of the rectification tower at 20Kg/h.

The hydrogen chloride gas in the esterification reaction and the hydrogen chloride gas in the dealcoholization reaction are removed. The reaction produces 273Kg of hydrogen chloride gas, which is circulated through the washing tower and down-absorbed. The temperature of the absorbent is 5-30°C. The washing tower is circulated down-absorbing. The pressure in the group is 600-740 mmHg, and the absorber is circulated. The water flow rate is 1270Kg/h, the light acid flow rate is 1000Kg/h, the dilute acid flow rate is 850Kg/h, and the concentrated acid flow rate is 850Kg/h. 750Kg/h, output 31% hydrochloric acid, 905Kg.

Distillation method^[2]

Using phosphorus oxychloride and ethanol as raw materials, esterification, dealcoholization and dehydrochlorination processes will be used to obtain crude triethyl phosphate with a content of 94.6% and the antioxidant mono-tert-butylhydroquinone, which will be mixed in the storage tank Evenly, the amount of antioxidant added is 200mg/Kg of crude triethyl phosphate. After mixing, it is pumped into the preheater of the light removal tower by a metering pump and heated to 75-80°C. The material in the tower is fed to the light removal rectification tower for negative pressure distillation. The light distillation tower has 28 to 32 theoretical plates, using JW-700 stainless steel wire mesh corrugated packing. The system vacuum is 6 to 8 mmHg. The temperature of the reboiler in the control column is 102 to 108°C, and the reflux ratio is 16 to 18:1. , the extraction temperature at the top of the tower is 52-55°C, and the diethyl phosphate by-product is continuously extracted. The triethyl phosphate semi-finished product is extracted from the tower kettle, and is continuously driven into the product distillation tower with a metering pump for negative pressure distillation.

The product distillation tower has 32 to 36 theoretical plates, using JW-700 stainless steel wire mesh corrugated packing. The system vacuum is 6 to 8 mmHg. The temperature of the reboiler in the control column is 118 to 124°C, and the reflux ratio is 3 to 4 : 1. The extraction temperature at the top of the tower is controlled at 64-68°C, and the triethyl phosphate product is continuously extracted. After stable operation, the distillation yield was 95.8%, the purity of triethyl phosphate product was 99.93%, and the acid value was 0.018mgKOH/100g.