The following editor will tell you about the function of the rotary evaporator, the factors affecting the distillation efficiency and the scope of application.
1. The role of the rotary evaporator
Rotary evaporators are mainly used for continuous distillation of large quantities of volatile solvents under reduced pressure. In particular, the concentration of the extract and the distillation of the receiving liquid during chromatographic separation can separate and purify the reaction product. The basic principle of the rotary evaporator is vacuum distillation, that is, under reduced pressure, when the solvent is distilled, the distillation flask is continuously rotating.
Factors affecting the distillation efficiency of rotary evaporators
2. Vacuum degree of rotary evaporation system
①The rotary evaporator is composed of vacuum pump and its pipeline, evaporating bottle and receiving bottle, condenser tube and other components. Among them, the key factors affecting the degree of vacuum are: the power of the vacuum pump and the airtightness of the system. Among them, the equipment includes: a vacuum pump, a sealing ring and a vacuum tube.
②The lower the vacuum pump limit is, the lower the vacuum value of the system is. However, the vacuum value that the system can form is determined by the equipment pressure resistance of the rotary evaporator and the avoidance of bumping when ensuring the distillation efficiency. To set a reasonable vacuum value, it is necessary to combine the above two factors and adjust it by the vacuum controller.
③Sealing ring: Connect the key components of the seal between the evaporation tube and the condenser tube. Wear resistance and corrosion resistance are the main performance requirements. The common materials are PTFE and rubber. Among them, the wear resistance and corrosion resistance of PTFE are better than those of rubber.
④Vacuum pump and sealing ring are consumable parts. During the use of the vacuum pump, its vacuum degree should be tested frequently to ensure the stability of its vacuum degree. As a detachable accessory, the sealing ring can be directly replaced. Silicone tubing is often used in vacuum tubes instead of rubber due to its slow aging efficiency.
Heating power of rotary steamer
The higher the temperature of the oil bath, the faster the distillation rate of the solvent. In the actual distillation process, the distillation efficiency is often not pursued by setting an excessively high reaction temperature. Reasons include:
①If the distillation substance is a heat-sensitive substance, it is easy to decompose and deteriorate at high temperature;
②Excessive temperature will easily lead to high temperature softening of sealing rings and other components, reducing their service life and reducing the airtightness of the system. Usually, the oil bath is heated with a water bath, and the temperature is set below 60°C. The temperature is higher than 80 ℃, and the oil bath is used for heating.
3 Motor speed
The faster the motor rotates, the larger the infiltration area in the evaporation bottle, the larger the heating area, the thicker the formed liquid film thickness, the larger the heat transfer temperature difference, and the higher the distillation efficiency. In actual use, the speed is not as fast as possible. Mainly due to:
①The faster the rotation speed, the greater the centrifugal force formed, which is easy to cause the bottle to drop;
②The viscosity of the material is different, and there is an investigation of the rotation speed.
4 cooling system
For better distillation efficiency, the temperature of the cooling system and the temperature of the heating pot are kept at a temperature difference of 40°C, so that the formed hot steam can be rapidly condensed and the influence of the steam on the vacuum degree of the system is reduced. The commonly used cooling medium is circulating condensate. If there are substances with a particularly low boiling point, ice-water baths and ice-ethanol baths with circulating freezers as carriers are also common choices.
Rotary evaporator application range
The rotary evaporator is a device that uses a rotary evaporation bottle to increase the evaporation area and place it in a water bath under reduced pressure while rotating and heating, so that the solution in the bottle is diffused and evaporated. It is an ideal basic instrument for concentration, drying and recycling in chemical industry, pharmaceutical industry, colleges and universities and scientific research laboratories for manufacturing and analysis experiments.