Also known as fractional distillation, short-path distillation is a low-pressure evaporation technique used to separate materials from various compounds. Materials frequently extracted using short-path distillation include fatty acids, fragrances, fuels, oils, polyurethane, and CBD oil from hemp plants. Multiple industries implement this method, from food to pharmaceutical.
Working Principles Short-Path Distillation
According to the Royal Society of Chemistry, short-path distillation is “A method of separating mixtures based on differences in their volatilities in a boiling liquid mixture under reduced pressure.” Because it uses a lower boiling temperature, short-path distillation equipment is especially useful for separating compounds that are unstable at higher temperatures. It’s also beneficial for purifying small quantities of compound.
Short-path distillation involves using a heated flask to gradually increase the temperature of the extraction material that’s fed into it. As the mixture heats up, its vapors rise into a fractioning tubing with the aid of a vacuum. The vapors travel a short distance—often only a few centimeters—into the tubing before being condensed, which is where the term “short-path” comes from. Because the vapors only travel a short distance, minimal quantities of the compound are wasted on the sides of the equipment. After passing through the fractioning tubing, the vapors enter the condensing tube. Here, they are cooled by water in a recirculating chiller, which allows for their condensation. Depending on the weight of each fraction, they will be separated throughout the condensing tube into different receiving flasks.
Advantages of short-path distillation
- Better for temperature-sensitive compounds: The use of a vacuum reduces pressure, so the distilling temperature used for short-path distillation can be much lower than the compound’s boiling temperature. Short-path distillation doesn’t require you to subject compounds to high temperatures for long durations, which are typically necessary when distilling at standard pressure. Since the process can take place at lower temperatures, this method is especially beneficial for compounds that become unstable at high temperatures or have a high boiling point.
- Prevents wasted compound: Short-path distillation only requires a liquid to travel a short distance, so less compound is lost in the equipment. It’s a more-efficient method that reduces material waste.
- Good for purifying small amounts of compound: Short-path distillation is the ideal method to distill small quantities. This is because the liquid travels across a shorter surface area and less compound is retained on the equipment.
- Ease of use: One of the main advantages of short-path distillation is its ease of use. Most conventional distillation techniques require large apparatuses to reach their desired purity levels. The apparatus used for short-path distillation, however, can achieve high distillate purity levels without the need for bulky, cumbersome equipment. The method is ideal for those with smaller working spaces.
- Quick heating process: While other conventional evaporation apparatuses typically take hours to complete a separation, short-path distillation may only take a few seconds.
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