Views: 17 Author: Rotary evaporator Publish Time: 2021-09-14 Origin: Rotary evaporator manufacturer
The rotary evaporator uses a rotary evaporator bottle to increase the evaporation area and place it in a water bath under reduced pressure while rotating while heating the device to diffuse and evaporate the solution in the bottle. When using a rotary evaporator for experiments, distillation efficiency is a very important performance. On the one hand, distillation efficiency reflects the quality of the product, but also determines the efficiency of the experiment. In this case, the higher the distillation efficiency, the higher the number of distillation samples achieved will also increase significantly. The reasons that affect the distillation efficiency of the rotary evaporator are as follows:
1. The vacuum degree of the rotary evaporator system
① The rotary evaporation evaporator is composed of a vacuum pump and its pipeline, an evaporating flask, a receiving flask, and a condenser tube. Among them, the key factors that affect the degree of vacuum are: the power of the vacuum pump and the airtightness of the system. Among them, the equipment includes: vacuum pump, sealing ring and vacuum tube.
② The lower the vacuum pump limit, the lower the vacuum value of the system. However, the vacuum value that the system can form is determined by two factors: the pressure resistance of the rotary evaporator and the avoidance of bumping when ensuring the distillation efficiency. To set a reasonable vacuum value, the above two factors need to be combined and adjusted by the vacuum controller. At present, the ultimate vacuum of the diaphragm vacuum pump is as low as 2 mbar, and the ultimate vacuum of the circulating water pump is about 50 mbar.
③ Sealing ring: connects the key components of the seal between the evaporator tube and the condenser tube. Wear resistance and corrosion resistance are the most important performance requirements. Common materials are PTFE and rubber. Among them, PTFE has better wear resistance and corrosion resistance than rubber.
④Vacuum pumps and sealing rings are all easy to wear parts. The vacuum degree of the vacuum pump should be tested frequently during the use process to ensure the stability of its vacuum degree. As a detachable accessory, the sealing ring can be replaced directly. Silicone tubes are often used to replace rubber for vacuum tubes because of their slow aging efficiency.
2. Heating power of rotary steaming
The higher the temperature of the oil bath, the faster the solvent distillation rate. In the actual distillation process, the distillation efficiency is often not pursued by setting an excessively high reaction temperature. The reasons include:
① If the distilled substance is a heat-sensitive substance, it is easy to decompose and deteriorate at high temperature;
② Excessively high temperature will easily cause the sealing ring and other parts to soften at high temperature, reduce their service life, and reduce the airtightness of the system. Generally, the oil bath is heated by a water bath, and the temperature is set below 60 ℃. If the temperature is higher than 80 ℃, use oil bath for heating.
3. Motor speed
The faster the motor speed, the larger the immersion area in the evaporating flask, the larger the heated area, the thicker the liquid film formed, the greater the heat transfer temperature difference, and the higher the distillation efficiency. In actual use, the speed is not as fast as possible. It is mainly due to:
① The faster the rotation speed, the greater the centrifugal force formed, which will easily cause the bottle to fall;
② The viscosity of the materials is different, and there is an investigation of the optimal speed
4. Cooling system
For the best 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 as to quickly condense the formed hot steam and reduce the influence of the steam on the vacuum of the system. The commonly used cooling medium is circulating condensate water. If there are substances with a particularly low boiling point, ice-water baths and ice-ethanol baths with a circulating refrigerator as a carrier are also commonly used choices.
Rotary evaporator purchase skills
Before purchasing a rotary evaporator, you must clarify some questions, such as the amount of distillation at one time, the number of samples that need to be distilled every day, the approximate solvents to be distilled, the approximate range of the boiling points of the solvents, and whether these solvents are Flammable, explosive or toxic and harmful solvents. After determining the experimental requirements and the type of solvent to be distilled, you can start purchasing a rotary evaporator.