Difference between Rotary Evaporator and Short Path Distillation

Rotary evaporator and short path distillation are both used to concentrate or extract substances from mixtures. They are very similar but still have some differences between them. Next, let’s go through the differences between rotary evaporator and short path distillation:

1. Different working principles.

Rotary evaporator keeps rotating the evaporation flask by electric, in order to enlarge the evaporation area to accelerate the evaporating speed. Short path distillation decreases the pressure within the distillation equipment, in order to decrease substances’ boiling points. Compared with under normal pressure, many substances’ boiling points could decrease 80C-100C under pressure 1.3-2.0KPa.

2. Different applications.

Rotary evaporator is mainly used to continuously distill volatile solvent under reduced pressure in chemical, industrial, biology medicine and so on. Short path distillation is mainly used for the separation and extraction of high boiling point substances and the compounds which have been thermally decomposed, oxidized or polymerized without reaching the boiling point at atmospheric distillation.

3. Different parts.

Rotary evaporator consists of rotor, evaporation flask, heating mantle, condensing tubes and so on. Short path distillation equipment consists of evaporation flask, vacuum pump, protection and pressure-measuring part. The glassware in the whole equipment must be made of thick glass. Otherwise, the short path distillation equipment could explode because of the uneven force on the glassware.

Similarities between them

Both the rotary evaporator and the short path distillation are the equipment to extract or concentrate substances from mixtures, and both are high efficient and widely used in many fields. That is to say that the rotary evaporator and short path distillation have the same function.

Because the cleaning requirements of laboratory glassware, users should clean them very frequently, in order to guarantee the quality of experiments. Therefore, the glassware in rotary evaporator equipment and short path distillation equipment should all be cleaned frequently.

Rotary evaporator and short path distillation are both used for the extraction of heat-sensitive substances. And they both are widely used in many fields, including people’s daily life at home, chemical, biochemical, make up and perfume, industrial and other fields.

How does short path distillation work?

The rotary evaporation, or rotavap, is a common and essential equipment used for  concentration, crystallization, drying, separation and solvent recovery in pharmaceutical,chemical and bio-pharmaceutical fields and other fields. Generally, it is used to remove a valtile solvent from a liquid mixture. A rotary evaporator mainly compose of following parts: a vacuum pump, a chiller, a condenser pump, a rotating flask and a receiving flask and other components. Most of people may be interested in a question how a rotary evaporator works. Hence, the working process of a rotary evaporator will be introduced specifically in the next section.

The working process of rotary evaporator is a consecutive process under a reduced environment. There are several steps for the operation:

a. Under reduced pressure, the evaporation flask was continuously rotated while the solvent was being distilled. The evaporation flask is a pear-shaped or round-bottomed flask with a standard ground mouth connection. It is connected with the pressure reduction pump through a serpentine condenser.

b. After substances get evaporated by heating, the gas-phase substances will go into condensing part to get condensed. In this step, gas substances are transferred through the glass tubes.

c. After gas-phase substances got condensed into liquid-phase, the liquid-phase substances will be transferred into receiving flask, which is the final destination of extracted substances. And then users will take the receiving flask out of rotary evaporator equipment.

During the whole working process, there is always a vacuum pump providing a vacuum environment for the rotary evaporator, which guarantees the whole system work in a reduced environment and the automatic feeding system formed by the pressure difference between atmosphere pressure and vacuum pressure.

How does short path distillation work?

1. Molecules diffuse from the liquid phase to the evaporation surface:

The beginning of short path distillation’s working is from evaporation flask. Sample will be placed in the evaporation flask and be heated by heating mantle. The temperature that heating mantle provides can be adjusted according to the boiling points of different solvents.

2. Free evaporation of molecules on the liquid surface:

The evaporation speed of solvents can be changed by the heating temperature. Besides, the stability of sample solvents is also an important factor to influence the evaporation speed.

3. Molecules fly from the evaporation to the condensation surface:

The extracted gas-phase solvents will be transferred along a short distance, and be condensed along this distance. During this process, gas-phase solvents will be cooled down by the condensing part and turned into liquid-phase solvents.

4. Solvents will be collected in the receiving flask:

After gas-phase solvents being turned into liquid-phase solvents, it will be transferred into receiving flask and be collected efficiently. Collecting extracted solvents in the receiving flask is very convenient for users to get.

In the whole working process of short path distillation, there are always vacuum pump providing vacuum and condensing part turning gas-phase solvents into liquid-phase solvents.

What is Short Path Distillation Used for?

Short path distillation is widely used in many fields, for example, petrochemical industry, pharmacy industry, oil production industry, food-processing industry and other fields. Therefore, there are so many applications of short path distillation, and they are as follows:

1. In petrochemical industry, the applications are waste oil regeneration, oil deweighting, ammonia, amine, quinoline derivatives, epoxy resin, resinous acid, isocyanate, isobutyl ketone, peroxide, liquid crystal, polyethylene glycol, silicone oil, softener and so on. Among these applications, waste oil regeneration is very environment-protecting and energy-saving, because regenerating waste oil products more oil that people can use, which means people can make full use of waste oil.

2. In pharmacy industry, the applications are amino acid ester, polymer intermediate products, vitamin E, vitamin life and so on. Among these applications, vitamin E is widely used in skin care field and is very popular nowadays.

3. In oil production industry, the applications are diglycerides, dimer fatty acids, fatty acids, fatty acid derivatives, polyglycerides, acids, wool ester alcohol and so on.

In food-processing industry, the applications are monoglyceride, lauric acid, propylene glycol, l-lactic acid, cod liver oil, rice bran oil, wheat germ oil, cinnamon oil, rose oil and so on. Among these applications, rose oil is used in skin care field a lot. Cinnamon oil is used in skin care and health care a lot, especially dispelling wind and dampness, warming and strengthening spleen and stomach.