Rotary evaporators are standard laboratory equipment found in nearly all laboratories. Chemical, pharmaceutical, food, and environmental industries are the most common users, but rotary evaporators, or “rotovaps,” may be found wherever processes require sample concentration or solvent distillation.
Rotary evaporator is better to use when you want to get rid from the solvent. Let’s say you have a solution of some chemical in some solvent. If you want to obtain a crystal form of the chemical, you may put solution to rotary evaporator and evaporate the solvent.
If you want to purify a solvent or other chemical which is liquid at normal conditions, you use distillation.
The difference is that with rotary evaporation you don’t really care what happens with vapors of the solvent, but distillation setup is specifically built for collecting vapors, and even separating vapors of different compounds.
The rotovap can be used for two purposes:
1) concentrate non-volatile components in a mixture (e.g, concentrating flavors from a blood orange by removing the water)
2) to extract the volatile aroma and flavor molecules from mixtures gently (e.g., extracting the desired flavors from a blend of alcohol, herbs, and fruit without heating the mixture up). The key to understanding any distillation is to remember that it is a separation. Sugars, acids, colors, and most bitter compounds are separated from aromas, alcohols, water, and small flavor molecules, etc.
Advantages of therotary evaporator
With a vacuum rotary evaporator you can carry out single-stage distilla-tion runs quickly and gently.The evaporation capacity of a rotary evaporator is about 4 timesgreater than that of a conventional, static distillation apparatus. Heattransmission in the heating bath as well as inside the flask is greatlyimproved by rotation of the evaporating flask. Rotation greatly enlargesthe active surface inside the flask, hastening the evaporation. With theliquid remaining at any one point of the flask wall for a short time only, itis subject to minimum stress during the distillation (no overheating, noincrustation). Bumping and foaming are greatly reduced by the rotation.
Why Vacuum control is necessary for Distillation or Evaporation in Rotary Evaporator
Distillation is a method of separation depending on the difference in volatility or Boiling Points of the mixture.This is particularly useful if the temperatures required for fluid to boil at atmospheric pressures would be hot enough to damage sensitive molecules through polymerization or by thermal cracking. Or can degrade Heat Sensitive substances Particularly Organic Extract of Herbs.Vacuum distillation is used to lower the pressure above a liquid to less than its vapor pressure. This allows the most volatile liquids to be selectively boiled off and distilled.We shall discuss the case of evaporation or distillation of herb extract in organic solvents or Water. As herb extracts are heat sensitive, It is commonly distilled in Reactor or Rotary Evaporator or Wiped Film Evaporator. In extraction, generally, there is a single solvent. So it is to be evaporated in either Rotary Film Evaporator or Wiped Film Evaporator under vacuum
Depending on the availability of Coolant temperatures it is desired to Evaporate solvent with 20-30 deg C to boiling point temperature higher than coolant outlet temperature for efficient condensation and recovery. As Vacuum Source say –Vacuum Pump or Ejector selected for the lowest vacuum for Multipurpose application; frequently it happens that boiling points of solvents are higher than or nearby coolant outlet temperatures. This causes weak recovery of solvents and damage to vacuum Source and Environment
In the case of Rotary Film Evaporator; Product is high-value concentrate. But in many cases product is condensate. This results in huge Monetary losses.
Please find Boiling points of different Pure solvents at different Absolute Pressures in MM of Hg. These values are calculated so it is nearby actual boiling point and of Pure solvents. To convert values in gauge vacuum, values to be subtracted from 760. Utility Temperatures in Research Labs or chemical Plant cannot be changed.
So Solution to this scene is to apply vacuum such that Solvent boils 20-30 deg above Coolant outlet temperature. It is possible with applying vacuum controller
Vacuum controllers are available which is designed for Rotary Evaporators and Reactors in Pilot plants with valve control logic. For the larger volume of Reactors, it can be made available with Proper design considering Process requirements
Vacuum control is required when High volatile solvents are to selectively boil off initially so that there shall be less impurity in Final Products
Vacuum Controllers have also available interlinked with Process parameters and time for a different application than Distillation
Rotary Evaporator-Distillation- Evaporation –Evaporation of Heat sensitive Materials- Automatic vacuum controller for Laboratory Rotary Evaporator –Vacuum control in large Reactors and distillation columns-Vacuum controllers-Vacuum Regulator