How it Works: Wiped Film Molecular Cannabinoid & Terpene Distillation

Wiped Film Molecular Distillation

The Pope Difference in Cannabinoid Purification and Terpene Distillation

Pope Wiped-Film Molecular Stills are a special type of short-path distillation equipment. These are continuous mode systems, as opposed to simple batch mode boiling flask stills (the latter often referred to as “short-paths”, though ironically, these are not truly short path designs as discussed in the next paragraph). The diagram below of the cannabinoid distillation purification process illustrates the means of this technology and shows the flow of the feed material and the separation of component fractions within the equipment. This same purification process and equipment can be used for various cannabinoid distillation such as the processing of CBD, THC, THCV, CBG, CBT, CBN, CBC & others.

In wiped film processes, feed material is delivered from a feed flask or a pump into the inner wall of a vertical cylindrical evaporation section, heated from the outer wall, (either electric resistance or circulating hot fluid jacket type).   Internally, rotating diagonally slotted wipers force liquid around and downward in as highly turbulent, thin film on the inner wall.  The moving liquid is heated via conduction through the wall. During the quick journey downward, lighter (lower boiling point) fractions of the liquid begin to vaporize.  Heavier residue material (Chlorophyll, large lipids, salts, sugars, heavy wax fractions), does not evaporate and continues the travel down the full length of the still body, falling into a residue receiver flask or discharge pump.

Cannabinoid Purification

Within the evaporation body there is a vertical internal condenser positioned central, parallel, and close to, the full length of the cylindrical evaporation surface, providing a short path for evaporated vapor molecules traveling from the heated surface to the condenser surface. For cannabinoid distillation, the internal condenser fluid must be kept elevated (~70°C) to prevent high viscosity or freeze-up of the condensed THC, CBD, and other component vapors.

Due to the optimized, continuous Pope equipment design, this all happens with high evaporation efficiency and within a number of seconds, (instead of hours of high-temperature exposure in batch type “short-paths”), and under vacuum-lowered temperatures, thus minimizing any possibility of product degradation.

Prior to the cannabinoid distillation pass through the wiped film still, there is a first pass in which terpenes and any other lighter end components are removed by distillation from the feed material and collected as a distillate.  The terpenes and other light components can be condensed in the internal condenser and an optional external condenser.  The residue from this pass is collected in a different flask or vessel until all the feed material has been depleted.  The residue contains the cannabinoids and heavy compounds and this fraction will then be fed through the still again as a second pass as has been previously described.  This first pass boosts the cannabinoid percentage and decreases the volatility of the feed material such that the cannabinoid distillation pass will behave better, resulting in optimized purity and yield.

The Molecular Background:

Basic evaporation and condensation

Wiped-Film still technology takes advantage of the fact that each chemical substance has a characteristic vapor pressure. It is this relative difference in vapor pressures that dictates how easily a complex compound can be separated into its constituent components.

Since the molecules of all matter are in constant motion in varying degrees, depending upon the chemical composition of that matter and the temperature and pressure applied to it, molecules near the surface tend to escape into the surrounding atmosphere. As temperature increases and pressure decreases, this escaping tendency usually increases, and the substance is said to vaporize.

The force generated by these escaping molecules is referred to as the vapor pressure of that material at a particular temperature and pressure. It is the relative difference in vapor pressure of substances that dictates how easily a complex compound can be separated into its constituent compounds.

How the Wiped-Film Still Works:

The Pope Wiped-Film Still consists of a heated body into which a fluid system requiring some degree of separation is continuously fed. The fluid is spread into a thin film by a rotating wiper blade assembly driven at a predetermined speed. The film, while being forced into turbulent flow by the wiper blades, progresses down the inside body wall aided by gravity and the slots in the wiper blades.

Have any further questions on short-path distillation? Contact us for further information!

Wiper blade moves each plug of material around and downward.

Understanding Cannabis Distillate and Pope Scientific’s Wiped Film Distillation Equipment

What is Cannabis Distillate? Cannabis distillate is a highly refined form of cannabis extract, known for its purity and potency. It typically contains 80-95% cannabinoids, making it ideal for various products like edibles, vape cartridges, and topicals. This distillation process removes impurities and unwanted compounds, resulting in a clean and versatile product.

Steps Involved Before Distillation

1. Extraction: Cannabinoids are extracted from the cannabis plant using solvents such as ethanol or CO2.
2. Winterization: The crude extract is mixed with ethanol and chilled to remove fats, waxes, and lipids.
3. Decarboxylation: The extract is heated to convert inactive cannabinoids (like THCA and CBDA) into their active forms (THC and CBD).

Wiped-Film Distillation Technology Pope Scientific’s wiped-film distillation equipment is renowned for its efficiency and precision in producing high-quality cannabis distillate. Here’s how it works:

• Thin Film Formation: The cannabis extract is continuously fed onto a heated surface where it forms a thin film. This thin film allows for rapid and uniform heating, ensuring that cannabinoids are efficiently separated from other compounds.
• Wiping Mechanism: A mechanical wiper or roller spreads the extract into a thin film and moves it along the heated surface. This enhances the evaporation rate and ensures even exposure to the heating element.
• Vacuum Application: The distillation process occurs under vacuum, which lowers the boiling points of the cannabinoids. This allows for the separation at lower temperatures, preserving the integrity and potency of the cannabinoids.
• Condensation: As the cannabinoids evaporate, they are immediately condensed on a cooled surface and collected as purified distillate.
• Multiple Passes: For achieving the highest purity, the distillate can undergo multiple passes through the wiped-film apparatus, further refining the product with each pass.

Advantages of Pope Scientific’s Wiped-Film Distillation Equipment

• High Efficiency: Maximizes cannabinoid yield and purity with minimal thermal degradation.
• Precision Control: Advanced temperature and vacuum controls optimize the distillation process.
• Scalability: Suitable for various production scales, from small labs to large industrial facilities.
• Robust Design: Durable construction ensures long-term reliability and performance.

Pope Scientific’s wiped-film distillation technology is trusted by industry professionals to deliver consistent, high-quality cannabis distillate. This equipment’s precision and efficiency make it an indispensable tool for producing top-tier cannabis products.

For more information, contact Pope. 

Optimize Lab-Scale Purification with Pope Scientific’s Benchtop Nutsche Filter Dryers

Pope Scientific leads the way in laboratory separation equipment with its proven Benchtop Nutsche Filter Dryers. These compact units have been a staple in laboratories for years, offering researchers a powerful tool for testing, piloting, and small-scale processing.  Pharma, fine chemicals, cannabinoids, electronics, and specialty materials are just a few of the many applications.

Transition From Lab Büchner Funnels to Industrial Operations

Pope’s fully enclosed sanitary design provides numerous advantages over the traditional, open Buchner funnel apparatus. Materials are contained and isolated from the user for maintenance of purity and safety. Featuring ASME-certified pressurizability, filtering, and cake washing is faster than via vacuum. Drying of the solids is also performed in the nutsche, e

fficiently accomplished under vacuum and jacket heating, plus a raising/lowering cake agitator to break up lumps and churn the solids.  This is the same operation as industrial nutsches, but smaller!

In-Stock and Ready for Action!

Pope’s Benchtop Nutsche Filter Dryers are stocked in 1, 3, 4, and 5-liter sizes.  All come pre-tested and pre-fitted with essential components including valves, sight glasses, pressure relief, spray assembly, pressure/vacuum gauge, and a manual with a full documentation package.

Custom Nutsches Too!

In addition to stocked units, Pope specializes in custom-designed lab, pilot, and production nutsches in a wide range of sizes, features, and functionality, and are optimized to meet clients’ processing needs and preferences.  We have your solution – contact us!

Pope: A Deep History of Providing Equipment and Support to the Cannabis Industry

Founded in 1963, over the years Pope has supplied the cannabis industry with expertise and equipment. Today after celebrating over 60 years of business, we want to take a look at how far we’ve come:

• 1963 – Pope Scientific Inc. is founded in Menomonee Falls, Wisconsin
• 1975 – Pope Scientific introduces the Wiped-Film Still product line and technology to many industries worldwide.
• 2002 – The 1st Pope WFS sale for a cannabinoid application, (CBD recovery from hemp seed oil byproduct in Canada)
• 2007 – Pope builds Turnkey 400L Reaction System for synthesis of pharmaceutical THC, (first of a series of subsequent skid modules)
• 2011 – The 2nd Pope WFS sale for a cannabinoid application to the University of Mississippi Dept. of Pharmacology, (THC purification from cannabis for research – at the time, the only authorized lab in the US)
• 2015 – Start of the THC Distillate boom in the US
• 2016 – Pope Sells over 100 Canna Wiped-film Stills
• 2017 – Start of the CBD Distillate Boom in the US and elsewhere
• 2018 – 1st Pope CBD Crystallizing Isolation System sold
• 2018 – Pope begins Cannabinoid Toll Processing and Process Development Services, (for several types of cannabinoids except THC)
• 2019 – Pope breaks ground for a 20,000 square foot building expansion (required both for cannabinoid industry and for general industry) larger scale distillation and process equipment
• 2019 – Pope sells over 500 Canna Wiped-Film Stills (in US and several countries)
• 2021 – Pope launches the ProPass 600 Canna Still
• 2023 – Pope celebrates 60 years in business
• 2023 –  Pope introduces the fully CE-certified Wiped-Film Still series at MjBizCon

Download the Timeline PDF

The Isolation of CBD

Introduction

Many processors perform CBD isolation to create a THC-free product for their end-user for a variety of reasons. For those who have had the opportunity to isolate CBD using crystallization, it is apparent that the material will readily form crystals, sometimes almost to a fault. Controlling this crystallization becomes quite important when the user is looking to create consistent and repeatable outcomes from their process. This article will focus on a high-level background of crystallization and why specific methods are recommended for isolating CBD.

Thermodynamic Background

Crystallization can occur due to the limited solubility of materials in a solvent. Many factors come into play (including temperature, solubility, concentration, etc.), but ultimately under the right conditions, many organic compounds will begin to form organized lattices, or crystals, which are a lower energy state than when dissolved in a supersaturated solution. By controlling the various factors of the process, the crystals can form with very high concentrations of the target molecule, excluding most impurities. The ability of an organic substance to crystallize is dependent on intramolecular and intermolecular forces. For certain compounds, the result of the solidification may instead form an amorphous solid or different polymorph of the isolated product.

Types of Crystallization

There are a few ways crystallization is performed, which include precipitation, evaporative crystallization, and cooling crystallization. Precipitation can be accomplished through a reaction, pH adjustment, or using anti-solvents. These methods do not seem to be common in isolation of CBD. Evaporative crystallization is performed by removing solvent until the material hits its saturation point and begins to nucleate. While effective, evaporative crystallization is not the most ideal method for isolating CBD due to the nature of the crystallization. “When using evaporative crystallization, the process is less controlled, which can lead to CBD being isolated as a paste which can, in turn, create more issues when the process is scaled,” says Ben Schilling, Tolling Manager at Pope Scientific. Evaporative crystallization also is required to be done at vacuum conditions to ensure the CBD will form a solid instead of staying in a liquid state.

Cooling crystallization takes advantage of the fact that many organic compounds have reduced solubility with reduced temperature. Pope Scientific’s recommendation for CBD isolation is to use a jacketed reactor and temperature control unit to bring the temperature of the solution down slowly. Eventually, the solution will become supersaturated. The formation of crystals in the supersaturated solution is dependent on many factors including any impurities that may be present, the mixing profile, and whether seed crystals are utilized.

Crystallization can also be done in batches or done as a continuous process. While continuous crystallization may come out on top when considering ROI, it does add validation complications for customers operating in cGMP environments.

Considerations During Crystallization

To ensure the saturation limits of the solution are not altered significantly it is important to purify the starting material as much as possible prior to crystallization. Many users will purify their cannabinoid extract by means of wiped film molecular distillation. This process will usually allow for a distillate product to be created at > 90% cannabinoid. This purification step will increase the likelihood of consistent crystallizations.

Mixing profile in the crystallizing vessel is also very important as this can have an impact on the nucleation (formation) of crystals vs the growth stage for crystals. Depending on the ultimate use of your crystalline product, certain particle sizes and particle size distributions may be beneficial. Agitators with good pumping capabilities as well as baffles in the reactor can result in more desirable crystal formation. It is important to balance minimum solvent use with the ability to have a flowable slurry that can be mixed.

The use of seed crystals can also be vital as this can impact the quantity and size of crystals formed. Seed crystals can also be critical in preventing the formation of amorphous solids or unwanted polymorphs. Since CBD readily crystallizes, seed crystals may not be necessary for most processors.

Isolation on a Nutsche Filter Dryer

Pope Scientific recommends using a dedicated reactor for the crystallization step as this will be specifically designed for good mixing. Additionally, while the capital cost can be reduced by using a Nutsche Filter Dryer for the crystallization step, this does run the risk of clogging the filter and causing cleaning issues.

Nutsche filter dryers are valuable tools in the GMP environment for filtering, washing, and drying. After a crystal slurry is created, the Nutsche filter-dryer can be used as a single container for the multiple unit operations that are required. This is beneficial because it eliminates the risk of contamination by eliminating any transfer steps. It also reduces the amount of equipment that must be validated as clean.

First, the slurry is transferred to the Nutsche where the “mother liquor” or supernatant can be separated from the crystalline product using a fine filter screen. The advantage of a Nutsche Filter Dryer over a standard filtration device is that it can be pressurized to speed along the filtering process and mother liquor can be recirculated allowing for the complete transfer of the crystals from the reaction vessel.

After the material is filtered, a pure solvent is typically added to remove any impurities that may be present on the surface of the crystals, often called a “wash” step. Washing is performed with either a spray nozzle or ring which allows for even distribution of solvent across the filter cake. If there is not an even distribution of solvent, channeling can occur, which will reduce the effectiveness of the wash. The washed crystals at this point should be of high purity.

These crystals can then be dried by applying heat and vacuum to the Nutsche filter dryer. For many crystals, the ability to apply vacuum in the Nutsche Filter Dryer is critical as the melting point of the crystals may be lower than the boiling point of the solvent. The agitator in the Nutsche allows for the cake to be smoothed which results in even drying and through proper process development and testing can yield a reliably solvent-free product.

While the methods and ideas described above do not delve into any new territory for organic chemistry, they are important concepts to consider when developing an isolation process. Often innovation is seen as an extremely important aspect of the cannabis industry, but it is important to consider tried and true methods when there is a need to meet cGMP requirements and put out a robust and consistent product.

For more information contact Pope today!

Optimize Your Cannabinoid Production with Pope’s Distillation Processing Services

If you’re considering adding distillation to your cannabinoid production or require help in distillation process improvement, reach out to Pope.  In addition to our well-known wiped-film molecular distillation equipment product lines, Pope runs a very active toll distillation services department.

The tolling department includes a range of toll production stills with throughputs up to 230 kg/hr, pilot plant process development equipment and lab-scale feasibility testing stills. Some of the many industries served include foods, flavors, fragrances, bio-materials, extracts, pharmaceuticals, edible and essential oils, cosmetics silicones, lubricants and polyglycerides.

Pope has many decades of experience in wiped-film operation and has harnessed that knowledge to assist our customers in developing, optimizing and commercializing their distillation processes.  We’ve been running numerous trials and piloting of a variety of different cannabinoids with customers’ feedlots for several years.  Our trials and piloting help determine what improvement in purity, yield, color and clarity is possible through distillation.  Pope operates a 2” lab wiped-film unit to conduct trials for our customers and we are capable of following distillation results by Gas Chromatography (GC).  Once your material has undergone trials, we can help suggest opportunities for improvement based upon past experience.

In addition to lab trials, Pope has extensive experience in process development and scaling studies in pilot scale and in performing toll processing for customers who would prefer to outsource to Pope to distill their cannabinoid feed rather than purchasing and running their own equipment.  (This is also a great opportunity for start-ups who want to begin producing their product before they build and run their own lab.) Pope is licensed by the FDA in food GMP and is also kosher and halal certified.  We have a Hemp Processing License with the state of Wisconsin and are able to trial any cannabinoid feed that has a Fit for Commerce Certificate.

Want to know more? Please contact us to discuss your testing and tolling needs.

Using a Mass Balance to Evaluate Your CBD Distillation Process

If the average person was asked to do a mass balance on a system, they might not quite understand what is required. However, for chemical engineers and industrial process chemists this is something learned quite early in their curriculum. While it is a tool often used by chemical engineers, there is no reason why it should not be part of any processor’s toolbox.

For processes involving chemical reactions, the mass balance is written out as:

INPUT + GENERATION = OUTPUT + ACCUMULATION + CONSUMPTION

However, when you are just using separation equipment (such as a wiped-film molecular still for distillation), the equation gets simplified to:

INPUT = OUTPUT + ACCUMULATION

Then, by defining the boundaries of a system, it becomes possible to check where your material is going which can allow you to make better decisions and optimize your process.

Let’s assume you are running a wiped-film molecular still to create CBD distillate. The INPUT to the still will be the feed material (the crude). The OUTPUT of this separation will be terpenes, residue, and CBD distillate. The ACCUMULATION would be any residual material left in the still. There are other outputs; the ethanol collected in the cold trap and any material that is lost through the vacuum pump, however, to simplify this exercise we will lump these into the accumulation and simply define them all as material loss.

While losses to accumulation are important, wiped film stills do not have miles of process piping, so overall this should not be a major concern on the equipment. However, by adding some analytical data to the mass balance much can be learned about your operation.

Example:

Prior to distillation, you have your crude CBD extract analyzed and the lab results come back indicating the material is 65% CBD by mass. You load the feed flask on your system with 2,000 grams of the material. You perform your first distillation and remove 160 grams of terpenes. On your second pass you get 1,155 grams of distillate and 635 grams of residue. When the lab results on your distillate come back, they show 90% CBD by mass. This seems good, but a mass balance will allow you to best review this.

For a Very Simple Mass Balance, You Have:

m_crude = m_terpenes + m_distillate + m_residue + m_loss  (1)

Where:

m_crude = mass of crude

m_terpenes = mass of terpenes collected

m_distillate = mass of distillate collected

m_residue = mass of residue collected

m_loss = material lost (to accumulate, transfer, etc.)

This yields 50 grams of material that is considered lost. Which could either be escaped ethanol or material that sticks as residual in the system (a common occurrence with high viscosity fluids).

Since there is not a large amount of material that was lost, it is now time to look at the amount of CBD you have recovered, also known as your yield. First, you must determine how much CBD is present to start, using equation (2):

m_CBD-C = m_crude * C_CBD-C (2)

Where:

m_CBD-C  = mass of CBD in crude

m_crude = mass of crude

C_CBD-C = _CBD Concentration in crude (mass %)

This equation shows that 1,300 grams of CBD are present in your crude. A similar equation can be used to determine the amount of CBD in your distillate:

m_CBD-D = m_distillate * C_CBD-D  (3)

Where:

m_CBD-D = mass of CBD in distillate

C_CBD-D = _CBD Concentration in distillate (mass %)

Leading to a total of 1,039.5 grams of CBD in your distillate. To calculate the yield of your process you then use Equation 4:

% Yield = m_CBD-D ÷ m_CBD-C  (4)

The percent yield from this distillation is approximately 80%, which would be considered quite sufficient. By further calculation, you can also estimate the amount of CBD that remains in your residue. We will assume that the 50 grams of lost material were at 65% CBD content, like the crude, meaning that 32.5 g of CBD where “lost”. By Equations 5 and 6, you can assume your remaining residue contains 228 grams of CBD or is 36% CBD (mass %):

m_CBD-R = m_CBD-C – m_CBD-D – m_CBD-L  (5)

Where:

m_CBD-R = mass of CBD in residue

m_CBD-L = mass of CBD lost

C_CBD–R = m_CBD-R ÷ m_residue (6)

Where:

C_CBD–R = CBD concentration in residue (mass %)

A great amount of processing in the cannabis industry is performed without much attention to mass balancing and utilizing before/after analyses between process steps.  In many of these cases, the company will get by, obtaining adequate purities and (often unknown) yields.  A somewhat careful operator will often be able to “get the job done”.  However, consistent utilization of the principles of mass balancing, together with obtaining and studying analyses of every batch and run will allow an OK  operator to become an excellent operator.  This person will be able to plan parameters as well as strategies for each run, resulting in optimal purity and yield, leading to lower costs, better product quality, at better pricing, all eventually leading to greater profit for their company than their competitors.

Post-Extraction Cannabinoid Decarboxylation and Its Relationship To Solvent Removal

Introduction to Cannabinoid Decarboxylation

During the course of post-extraction cannabinoid processing, one of the steps normally (though not always) carried out is the conversion of the non-active acid form of the cannabinoid(s) to the active form, prior to final product completion. This is accomplished utilizing a chemical reaction named decarboxylation, (“decarbing” for short). The reaction can be performed at a choice of two different stages in the processing sequence; either with the biomass prior to extraction or else with the liquid form after extraction. In either case, the reaction is driven by heating to increased temperatures (normally between 110° and 150°C) for a specified amount of time (normally between 0.5 and 3 hours), though some operators use more extreme parameters. The reasons for choosing between the pre-extraction and post-extraction methods and the specific parameters used are various and depend on the processor’s feedstock and product goals. Post-extraction decarbing is more common and is the method covered here.

The Reaction & Efficiency

The reaction takes place at a position on the cannabinoid molecule containing a carboxyl group (-COOH). Heat induces substituting the carboxy group by the single hydrogen atom (-H). In the process, the carbon and the two oxygen atoms break away from the cannabinoid as carbon dioxide (CO2) in gas form. For the case of post-extraction decarbing, one of the most efficient known methods is to have a batch of liquid extract contained within a stainless steel reaction vessel which is heated under vacuum conditions and rapidly stirred.

The purpose of agitation is three-fold:

• Agitation helps transfer and distribute the heat required for reaction rapidly, from the vessel walls to the liquid.
• Agitation enables the released CO₂ to better dissipate out of the liquid and into the vapor space, which is under vacuum, helping the reaction to “go to the right” and be conducted efficiently.
• Agitation makes other gases and evaporating solvents efficiently escape from the liquid to the upper space for removal from the vessel.

CO₂ and Ethanol Dissipation

In the majority of cases, the non-active extract will also contain some amount of solvent ethanol, usually as a result of either solvent extraction and/or winterization with chilled ethanol and filtering for wax elimination. After those steps, the bulk removal of the ethanol will have been carried out typically with rotary evaporators for smaller scale or with falling film evaporators in larger-scale operations. However, in many cases, the ethanol is not sufficiently removed to the levels achieved with more careful processing. Often, a decision is made to remove the remainder during the decarbing process since it will conveniently be under raised temperature and vacuum. Thus, the decarbing apparatus serves double duty as a reactor and as an evaporator, discharging both CO2 and ethanol.  However, it is possible, and fairly common, to leave “too much” ethanol in the extract prior to decarbing, resulting in lingering ethanol in the extract, even with a successful decarbing cannabinoid conversion. This occurs due to weak hydrogen bonding of alcohols to organic compounds such as cannabinoids, effectively increasing the alcohol’s boiling point. Too much ethanol remaining in the distillation feed batch can impact the effectiveness of terpenes removal in the 1st distillation pass, with a spillover effect impacting the cannabinoid distillation in the 2nd pass, resulting in a product of lesser quality and yield.

A Turnkey Approach

Pope Scientific provides decarboxylation reaction equipment and complete turnkey systems designed for optimal processing of any required size range to the cannabinoid industry. A complete system includes a jacketed 316L stainless steel reaction vessel with ASME vacuum and pressure rating and food or pharma grade finish, a matching agitator, a heating circulator, condenser, dry running vacuum pump, and instrumentation. Controls can range from simple manual type to automated PLC stations with advanced data handling, depending on the customer’s budget and preferences. All parameters and sequences can be preprogrammed, including an increasing vacuum level during the process, reaching better than 0.5 torr near the end for better subsequent distillation processing. Options include portability and XP Div. 1 or 2 ratings. For increased convenience, the decarbing vessel can be made portable to double as a feed vessel for a Pope Wiped-film Molecular Still.

Optimizing Evaporation Beforehand

It is mentioned above that rotary evaporators and falling film evaporators often do not completely remove ethanol to ideal levels, (<0.1%).  Pope can provide guidance for dealing with these problems.  For various reasons, it is not possible to effectively decrease solvent from high levels to very low levels, (e.g., from 80% to 0.1%) in continuous mode evaporators in a single pass. Pope offers multistage evaporation systems incorporating either a falling film evaporator or a wiped film evaporator for the first stage and a smaller wiped film evaporator for the second stage. This equipment is available in fully turnkey integrated and automated skid-mounted systems.

Contact Pope today or request a quote to discuss your current or future decarboxylation and evaporation equipment requirements.