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Ethanol recovery

Distillation-molecular sieve membrane coupling technology

Case 1: 8,000 tons/year rectification-molecular sieve membrane coupling ethanol separation device

It is used as a solvent for extracting or washing drugs in the process of synthesizing the drug enalapril. The ethanol mother liquor contains acetic acid, sodium chloride, by-products and branched chain groups in the drug synthesis process, etc. The mother liquor is yellow and has Odor, conductivity 600~1000μs/cm, water content about 10wt.%, if ethanol is to be reused, the water content must be reduced to below 0.4wt.% and it is colorless and transparent. The original owner used ethylene glycol and potassium acetate as extraction agents to extract and rectify the two mother liquors for recovery. A total of 4 rectification towers with a height of 20-25m were used. Although this process can also obtain ethanol that meets the recovery standards , but there are problems such as high energy consumption, cumbersome operation, time-consuming and laborious driving, long-term parking is easy to block the tower, and ethylene glycol needs to be replaced regularly. Therefore, the rectification-molecular sieve membrane coupling process technology is adopted for this project, and the acid-base neutralization device, rectification dehydration desalination device and molecular sieve membrane equipment are integrated in this project to complete the removal of inorganic acids, organic acids and water in ethanol in one step. Finally, qualified ethanol with a water content of ≤0.4wt.%, colorless and transparent, and in compliance with corporate recycling standards is obtained.

process flow


process flow


Process comparison

Comparison of Recovery Processes for Enalapril Ethanol Mother Liquor


extractive distillation

Distillation-molecular sieve membrane coupling

steam (t/t raw material)



Circulating water (m3/t raw material)



Low temperature water (m3/t raw material)



Electricity (kwh/t raw material)



Operating cost (yuan/t raw material)



Yield %



Maximum operating pressure (MPa(G))



Required steam pressure (MPa(G))

≥1 (recovery tower)
≥0.4 (extraction tower)


Installation height of rectification tower (m)




4-6 people/class

1~2 people/class

Operational complexity

Complicated, requires coordination and cooperation of multiple people, long driving and parking time, and long time for equipment stabilization

Simple, only one person is needed to complete the work of driving and parking, and the equipment can be stabilized in a short time

There is a problem

Long-term operation will cause high-boiling impurities and salts in the ethanol mother liquor to be mixed into ethylene glycol, which needs to be disposed of or replaced regularly. After long-term shutdown of the equipment, it is easy to block the tower and the cleaning is cumbersome

Molecular sieve membranes strictly control the properties of raw materials, and require personnel to attach great importance to and conduct regular inspections, otherwise the membrane tubes are easily damaged


Ethanol recovery

Enalapril ethanol mother liquor recovery rectification-molecular sieve membrane coupling device


Acetonitrile recovery

Ceftriaxone sodium is a broad-spectrum long-acting antibiotic launched by Swiss Roche Company in 1982. It has a small dosage, low toxicity and side effects, and has a large market share. It is the third-generation cephalosporin with broad-spectrum antibacterial activity. In actual production, when the crude product of ceftriaxone sodium is produced from the raw material 7-ACA, acetonitrile is used as a solvent for the reaction. After the reaction is over, the acetonitrile mother liquor produced is separated to obtain a certain quality index of reclaimed acetonitrile and is used again as a reaction solvent for recycling. In the production process, acetonitrile is inevitably mixed with water and other impurities to produce acetonitrile waste liquid. Since acetonitrile will form azeotrope with water (the water content of acetonitrile-water azeotrope under normal pressure is about 16 wt.%), it is impossible to directly separate and refine the acetonitrile waste liquid into a reusable reaction solvent by conventional distillation methods (The water content of solvent acetonitrile is usually ≤0.05wt.%). And from this operational route, the quality of reclaiming acetonitrile plays decisive influence on the quality of ceftriaxone sodium crude product.

In the traditional process of recovering acetonitrile, there are mainly the following four separation and refining processes: pressure swing rectification, azeotropic rectification, salting-out method, and dehydrating agent method. These several methods all use rough steaming and rectifying two steps, use special rectifying method to carry out separation treatment, there are problems such as complicated treatment method, high equipment cost, low separation efficiency, high energy consumption, low acetonitrile yield.




1 is preheater, 2 is concentration tower, 3 is neutralization tank, 4 is impurity removal tower, 5 is superheater, 6 is pervaporation separation unit, 7 is permeate condenser, 8 is vacuum pump, and 9 is refining tower.

Put the acetonitrile waste liquid in the synthesis of ceftriaxone sodium into the concentration tower, and use rectification to remove part of the water and heavy components; after concentration, the acetonitrile distillate is sent to the neutralization tank to adjust the pH; the neutralized acetonitrile distillate The acetonitrile distillate is sent to the impurity removal tower for further impurity removal. After removing impurities in the impurity removal tower, the acetonitrile distillate enters the pervaporation membrane separation unit, and the residual liquid returns to the front stage concentration tower to recover the acetonitrile; After the separation, the crude acetonitrile is obtained, and the water and a small amount of acetonitrile in the solution on the feed liquid side pass through the pervaporation membrane in the form of steam to obtain the permeate. After the permeate is condensed, it returns to the neutralization tank and recovers the acetonitrile in it again; The acetonitrile is sent to the refining tower for refining to obtain finished acetonitrile, and the acetonitrile-water azeotrope distilled out of the refining tower is returned to the impurity removal tower to recover the acetonitrile therein.


Project case


Isopropanol recovery

A rectification-pervaporation membrane coupling technology

The isopropanol feed liquid from the production process is transported by the feed pump, and then enters the rectification tower after heat exchange with the steam of the finished membrane product in turn, and the tower is pressurized for continuous operation. After the stable operation of total reflux, isopropanol vapor with a water content of ~12wt.% is extracted from the top of the rectification tower. After being partially condensed by the decondenser, it flows into the reflux tank, and then is transported to the top of the rectification tower by the reflux pump. Part of the non-condensed isopropanol vapor enters the membrane separation unit after being overheated by the superheater. The membrane separation unit is composed of multiple membrane modules connected in series. The water in the raw material and a small amount of isopropanol permeate from the upstream side of the membrane to the downstream side of the membrane through the membrane module, and the final stage of the upstream side of the membrane is used to obtain the finished product. The downstream side of the membrane adopts the method of vacuuming and condensing to form the vapor partial pressure difference between the upstream and downstream components of the membrane. The permeate steam enters the condenser under the suction of the vacuum unit, and the condensed permeate is sent to waste water treatment. The waste liquid in the rectification column is sent to waste water treatment after being cooled by the cooler.


Isopropanol recovery



Isopropanol recovery


Shenyang Sanjiu Pharmaceutical Co., Ltd. 3000 tons/year rectification-molecular sieve membrane coupled isopropanol separation device


B Adsorption-pervaporation membrane coupling technology

34,400 tons of ethanol and isopropanol dehydration project of Zhangjiagang Kailing Chemical Industry: The enterprise uses isopropyl acetate and hydrogen as raw materials, and through catalyst catalysis, realizes the hydrogenation reaction of isopropyl acetate to produce ethanol and isopropanol, but in ethanol and isopropanol In the separation process of alcohol products, the separation process becomes complicated due to the existence of a small amount of water, so the reaction production mixture must be dehydrated before further separation to obtain ethanol and isopropanol. In the original process, the reaction solution is sent to the molecular sieve adsorption process for dehydration to obtain anhydrous ethanol isopropanol mixture, and then further refined to obtain the product. However, in the molecular sieve adsorption process, the molecular sieve needs to be desorbed after the adsorption is saturated, and the water content of desorption is 2~ The 3% ethanol-isopropanol mixture cannot be processed, and the annual production of this aqueous mixture is about 34,400 tons. If it cannot be effectively recycled, the yield, economic benefits and environmental protection pressure of the entire production line will be severely tested. For this reason, the company ordered a set of ethanol-isopropanol mixed system molecular sieve membrane dehydration device with a processing capacity of 34,400 tons/year from Jiangsu Jiutian High-Tech Co., Ltd., which is used to treat the desorption liquid generated by the molecular sieve adsorption device and dehydrate the desorption liquid. After reaching the water content of 0.3%, enter the next process to continue the separation of ethanol and isopropanol.


Isopropanol recovery


Molecular sieve adsorption-molecular sieve membrane coupling device in the process of hydrogenation of isopropyl acetate to produce ethanol and isopropanol

After adopting this technology, it is calculated that 1.2 tons of steam and 90m 3 of circulating water can be saved per ton of product compared with the traditional technology . At the same time, labor and environmental protection costs are significantly reduced, and the annual increase in benefits is 9 million yuan, which greatly improves the company's market competitiveness. Competitiveness.