[WaterFarmFan]

I am trying to understand the variables of decarbing under vacuum versus atmospheric pressure using flower material (not solvent extract). From my experiments, it seems that residual water in the material helps act as a barrier (raises activation energy?) and keeps the material at a lower temp versus the oven temps (I am not sure if that makes sense). My calculus is a little rusty, and I am just trying to make heads and tails of it all.

In a nutshell, what I am asking is there a relationship between heat, time and vacuum level as it relates specifically to Decarboxylation? I have placed finely ground cured material in a vacuum oven at 200F+ for 4 hours and it is still slightly damp to the touch. I would think that 15-20 minutes in a traditional convection oven would dry out the material quite well.

Any thoughts on what is going on?

https://thealchemistresource.thealche...oxylation.html

https://en.wikipedia.org/wiki/Decarboxylation

"Upon heating, Δ9-Tetrahydrocannabinolic acid decarboxylates to give the psychoactive compound Δ9-Tetrahydrocannabinol.[6] When cannabis is heated in vacuum, the decarboxylation of tetrahydrocannabinolic acid (THCA) appears to follow first order kinetics. The log fraction of THCA present decreases steadily over time, and the rate of decrease varies according to temperature. At 10-degree increments from 100 to 140 C, half of the THCA is consumed in 30, 11, 6, 3, and 2 minutes; hence the rate constant follows Arrhenius' law, ranging between 10−8 and 10−5 in a linear log-log relationship with inverse temperature. However, modelling of decarboxylation of salicylic acid with a water molecule had suggested an activation barrier of 150 kJ/mol for a single molecule in solvent, much too high for the observed rate. Therefore, it was concluded that this reaction, conducted in the solid phase in plant material with a high fraction of carboxylic acids, follows a pseudo first order kinetics in which a nearby carboxylic acid participates without affecting the observed rate constant. Two transition states corresponding to indirect and direct keto-enol routes are possible, with energies of 93 and 104 kJ/mol. Both intermediates involve protonation of the alpha carbon, disrupting one of the double bonds of the aromatic ring and permitting the beta-keto group (which takes the form of an enol in THCA and THC) to participate in decarboxylation.[7]"

Arrhenius Law

https://en.wikipedia.org/wiki/Arrhenius_equation
https://www.youtube.com/watch?v=3eBu2M975hE

https://en.wikipedia.org/wiki/Activation_energy

"In chemistry, activation energy is the energy which must be available to a chemical system with potential reactants to result in a chemical reaction.[1] Activation energy may also be defined as the minimum energy required to start a chemical reaction. The activation energy of a reaction is usually denoted by Ea and given in units of kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol).

Activation energy can be thought of as the height of the potential barrier (sometimes called the energy barrier) separating two minima of potential energy (of the reactants and products of a reaction). For a chemical reaction to proceed at a reasonable rate, there should exist an appreciable number of molecules with translational energy equal to or greater than the activation energy."

[WaterFarmFan]

And just to clarify, I am extracting terpenes and not trying to decarb with this process. I want to know if there is a temp/time max using a vacuum > 28 Hg to try and avoid decarbing as much as possible.

[prune]

sponge

[WaterFarmFan]

Another example would using fresh flower versus cured flower. Both are frozen in liquid nitrogen and processed/crushed through a 750 micron stainless screen with stems separated.

Would the fresh material decarb at a slower rate in a vacuum? If so, why?

[G.O. Joe]

How is the pot being heated? Looks like molecules in the gas phase freely moving about do a lot of heat transfer. You're sucking them all out and the heat is being transferred downstream.

[Gray Wolf]

Originally Posted by WaterFarmFan

I am trying to understand the variables of decarbing under vacuum versus atmospheric pressure using flower material (not solvent extract). From my experiments, it seems that residual water in the material helps act as a barrier (raises activation energy?) and keeps the material at a lower temp versus the oven temps (I am not sure if that makes sense). My calculus is a little rusty, and I am just trying to make heads and tails of it all.

In a nutshell, what I am asking is there a relationship between heat, time and vacuum level as it relates specifically to Decarboxylation? I have placed finely ground cured material in a vacuum oven at 200F+ for 4 hours and it is still slightly damp to the touch. I would think that 15-20 minutes in a traditional convection oven would dry out the material quite well.

Any thoughts on what is going on?

https://thealchemistresource.thealch...oxylation.html

https://en.wikipedia.org/wiki/Decarboxylation

"Upon heating, Δ9-Tetrahydrocannabinolic acid decarboxylates to give the psychoactive compound Δ9-Tetrahydrocannabinol.[6] When cannabis is heated in vacuum, the decarboxylation of tetrahydrocannabinolic acid (THCA) appears to follow first order kinetics. The log fraction of THCA present decreases steadily over time, and the rate of decrease varies according to temperature. At 10-degree increments from 100 to 140 C, half of the THCA is consumed in 30, 11, 6, 3, and 2 minutes; hence the rate constant follows Arrhenius' law, ranging between 10−8 and 10−5 in a linear log-log relationship with inverse temperature. However, modelling of decarboxylation of salicylic acid with a water molecule had suggested an activation barrier of 150 kJ/mol for a single molecule in solvent, much too high for the observed rate. Therefore, it was concluded that this reaction, conducted in the solid phase in plant material with a high fraction of carboxylic acids, follows a pseudo first order kinetics in which a nearby carboxylic acid participates without affecting the observed rate constant. Two transition states corresponding to indirect and direct keto-enol routes are possible, with energies of 93 and 104 kJ/mol. Both intermediates involve protonation of the alpha carbon, disrupting one of the double bonds of the aromatic ring and permitting the beta-keto group (which takes the form of an enol in THCA and THC) to participate in decarboxylation.[7]"

Arrhenius Law

https://en.wikipedia.org/wiki/Arrhenius_equation
https://www.youtube.com/watch?v=3eBu2M975hE

https://en.wikipedia.org/wiki/Activation_energy

"In chemistry, activation energy is the energy which must be available to a chemical system with potential reactants to result in a chemical reaction.[1] Activation energy may also be defined as the minimum energy required to start a chemical reaction. The activation energy of a reaction is usually denoted by Ea and given in units of kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol).

Activation energy can be thought of as the height of the potential barrier (sometimes called the energy barrier) separating two minima of potential energy (of the reactants and products of a reaction). For a chemical reaction to proceed at a reasonable rate, there should exist an appreciable number of molecules with translational energy equal to or greater than the activation energy."

What vacuum level? How much material and how is it packed?

[WaterFarmFan]

Originally Posted by G.O. Joe

How is the pot being heated? Looks like molecules in the gas phase freely moving about do a lot of heat transfer. You're sucking them all out and the heat is being transferred downstream.

Hi Joe. I have 0.9 AI vacuum oven. What I am trying to understand is how the lack of gas phase molecules in the vacuum effects decarb times. And also how residual water in the material seems to be providing some kind of buffer.

[WaterFarmFan]

Originally Posted by Gray Wolf

What vacuum level? How much material and how is it packed?

Hey GW. With my current 4 stage cold trap setup, I am able to pull a max of 28 Hg in the oven. I usually put 150-200g of very high quality flowers that has been ln2 processed to a rough grind. I use a 10" stainless high wall pan that acts as container start to finish. Stainless Honey strainer drops on top of pan and material is frozen and crushed through. The layer of material is ~3/4" inch thick and I stir the material with a stainless pestle every 45-60 minutes that it is in the oven.

[G.O. Joe]

If you don't have hot molecules actively transferring heat to other molecules, you need some radiation for effective heating in hard vacuum or obviously decarboxylation is mooted by inefficient heat transfer. Does anyone remember any decarboxylation analysis of microwave drying - maybe someone has been puttering around with a Milestone lately? Perhaps there are one or two members who have compared BHO decarboxylation with and without vacuum - my uneducated guess is vacuum might be slightly faster but needs as much heat.

[Gray Wolf]

Originally Posted by WaterFarmFan

Hey GW. With my current 4 stage cold trap setup, I am able to pull a max of 28 Hg in the oven. I usually put 150-200g of very high quality flowers that has been ln2 processed to a rough grind. I use a 10" stainless high wall pan that acts as container start to finish. Stainless Honey strainer drops on top of pan and material is frozen and crushed through. The layer of material is ~3/4" inch thick and I stir the material with a stainless pestle every 45-60 minutes that it is in the oven.

You might try preheating the oven and bringing the material up to temperature, before pulling a vacuum. As GJ notes, no convection heat transfer in a vacuum, leaving only radiation and conduction.