Synthesis of TiO2 Nanoparticles In A Spinning Disc Reactor

Technology Review of Spinning Disc Reacor | Blog | Industry Series | July 2017

20170727-infininty-supercritical-review-sdr-nanoparticles

 

Review: Mohammadi, S., Harvey, A., & Boodhoo, K. V. (2014). Synthesis of TiO 2 nanoparticles in a spinning disc reactor. Chemical Engineering Journal, 258, 171-184.

A spinning disc reactor (SDR) is a reactor where reactants are injected onto the surface of a rotating disc, which creates a centrifugal force pushing the liquid out to the ends of the reactor where it exits at the bottom of the reactor.

The pros of such a reactor are that: the disc and walls can be temperature controlled, additional pipes can inject catalysts (particles in a slurry, or as a gas), pressure can be controlled, it is continuous flow, and that the disc creates a very interesting dynamic on the reaction, all allowing for a high level of process control and thus selectivity in the reaction.

It has been shown that SDR’s can be used to make quantum dots, or semiconductor nanoparticles. This paper summary of the precipitation synthesis of titanium oxide (TiO2) nanoparticles with an SDR will highlight some of the advantages to using an SDR for this purpose.

 

Nanoparticle TiO2 has many uses from being used as a pigment or catalyst, to being used in pharmaceutical products or surface coatings.

Traditionally it is made uses a sulphate or chloride process, both considered very toxic for the environment due to their waste products, but can be made through a synthetic route with adequate process control.

SDRs have been focused on recently due to their quote ability to provide a uniform and rapid micromixing environment when two liquid streams are contacted on the rotating surface unquote.

Micromixing relates to when two liquids are contacted on the disc and the extreme centrifugal force creates a thin-film region of intense heat and mass transfer.

In nanoparticle precipitation processes, micromixing is incredibly important because it allows for control of the supersaturation of the medium, a key parameter in the nucleation process.

Micromixing also gives control of the molecular diffusion which is a key parameter in the growth process of the crystals. SDRs also create near ideal plug flow conditions which helps produce quote much more well defined crystals unquote.

Finally, the operating costs of an SDR are usually much less than the operating costs of similarly continuously mixed reactors.

The production of these TiO2 nanoparticles follow two simultaneous reactions, first the hydrolysis of titanium tetra isopropoxide (TTIP) with acidic water and then the polycondensation of the resulting titanium tetrahydroxide using nitric acid as a catalyst.

Four different factors were considered in this experiment, the rotational speed of the disc, the total flow rate, the grooved nature of the disc, and the ratio of water to precursor.

First, the rotational speed of the disc from 400rpm to 1200rpm produce vast differences in both particle size, where 400rpms producing an average particle size of ~16nm while 1200rpms created an average size of ~4.8nm, and particle size distribution, where 400rpms produced a range of particle sizes of 18nm and 1200rpms produced a range of particle sizes of 3nm.

This result was found to be due to the micromixing effect causing a high uniform distribution of supersaturation in the higher rpms.

Second, at higher flow rates smaller sized particles and more uniform sizing distribution

were found due to a similar effect to the higher rotational speed, where a higher flow rate causes more surface ripples, meaning better mixing of the precursors and thus a favoring of nucleation vs crystal growth.

Third, this effect was again seen with the grooved disc preforming vastly better than the smooth disc in producing smaller and more uniformly sized particles.

Finally, a higher ratio of water to the precursor TTIP produced more uniform, smaller, and spherical in nature particles compared to less uniform, larger, and irregular particles with lower ratios.

 

This effect is due to the nucleation reaction being increased with higher water concentrations due to its large role in the hydrolysis reaction.

Comparing the SDR to more traditionally stirred reactors, the power consumption per particle was lower, the particle size was lower, and the particle size distribution was tighter in the SDR.

In conclusion, a SDR has many advantages over conventionally stirred reactors in the production of TiO2 nanoparticles and these advantages could possibly be applied to the production of other quantum dot particles.

Source:

Authors: Mohammadi, S., Harvey, A., & Boodhoo, K. V. (2014).

Title: Synthesis of TiO 2 nanoparticles in a spinning disc reactor.

Publication: Chemical Engineering Journal, 258, 171-184.

Optimization and Characterization of Cannabis Extracts Obtained By Supercritical Fluid Extraction

PDF Review: 20170719-infinity-supercritical-sco2-review

Source Review: Authors: Omar, J., Olivares, M., Alzaga, M., and Etxebarria, N. (2013).

Title: Optimization and characterization of marihuana extracts obtained by supercritical fluid extraction and focused ultrasound extraction and retention time locking GC-MS.

Journal of Separation Science, 36(8), 1397-1404.

Several monoterpenes and sesquiterpenes are responsible for the unique and strong smell of the cannabis plant.

Terpenes are compounds in a group of naturally occurring volatile unsaturated hydrocarbons built off of isoprene which has the molecular C5H8, with monoterpenes having the structure C10H16 and sesquiterpenes having the structure C15H24.

While sesquiterpenes are in lower amounts in the buds of the cannabis plant, through drying the plant gives off a greater loss of monoterpenes, which would mean most of the smell of the plant while drying is from the monoterpenes.

Monoterpenes are mostly unstable and thus can be easily altered or destroyed in many normal extraction techniques, which has led to much focus on using supercritical fluid extraction (SFE) with CO2 to extract them.

Terpenes are miscible in CO2 at low temperatures and pressures while many non- volatile compounds (like cannabinoids) are not, which mean they can be extracted separately.

Due to these miscibility differences, two different optimal extraction parameters were found when trying to optimize the extraction yield for terpenes or for cannabinoids.

The extraction parameters investigated included pressures between 100 bar (1450psi) and 250 bar (3626 psi), temperatures between 35 (95 F) and 55 C (131 F), flow of solvent between 1-2 ml/min (extracting 100mg of plant matter), and addition of ethanol as a cosolvent between 0 and 40 percent by weight.

In reference to terpenes, temperature and ethanol percentage were significant, with low temperature and no ethanol being the best conditions.

In reference to cannabinoids, only ethanol percentage was found to be significant, with mild ethanol percentages being found to be most efficient.

Due to the insignificance of the other factors,

100 bar (3626 psi), 35 degrees Celsius (95 F), and a solvent feed of 1 ml/min are both optimal for terpenes and for cannabinoids, while 0 percent of ethanol is best for terpenes and 20 percent is best for cannabinoids.

It was also found that different cannabis strains had different concentrations of cannabinoids and terpenes.

For example, Critical and Amnesia are richer in cannabinoids than Somango, AK-47 and 1024.

Also in respect to terpenes, Critical species had the highest concentrations of alpha- pinene and beta-pinene and Amnesia has the highest concentrations of limonene.

Out of all the five species, five monoterpenes, twelve sesquiterpenes, and eight cannabinoids were able to be positively identified and quantified.

The separate extraction of terpenes and cannabinoids is important because terpenes contain their own therapeutic benefits and thus can be used without the psychotropic effects of the cannabinoids.

 

The optimal conditions mean one could extract all the terpenes first and then flush the system with ethanol to extract all the cannabinoids without changing the other parameters. To back this up, in a subsequent extraction as detailed above, all of the monoterpenes were found in the no ethanol extraction and only contain trace amounts of three of the eight cannabinoids.

 

The study also investigated the optimal extraction parameters of using focused ultrasound extraction with isopropanol and cyclohexane and found the best conditions for overall extraction were 3 s(-1) cycles, 80 percent of amplitude on the sonicator, 5 minutes of sonication time with a 1:1 mixture of isopropanol and cyclohexane.

While this extraction yielded slightly more overall extraction than the SFE, it didn’t allow for the selectivity of the terpenes and the cannabinoids.

Thus it is recommended that SFE CO2 is used for cannabis extraction’s due to the minimal difference in yields, the selectivity it offers, the food-safe nature of it, and the low-flammability of the solvent.

Technology Review of Cell Lysis Methods

PDF Download: 20170718-infinity-supercritical-cell-lysis-methods

 

Plant Cell Pressure |Strength of Plant Cell Walls | Ways to Break Cell Walls

 

How to Break Down Cell Walls:

Mechanical:

-Grinding: Mortar and pestle, which is often done with plants frozen in liquid nitrogen.

-Beadbeating: Cracking open cells using ceramic or glass beads, typically done in suspension and in a vortex.
-Sonification: Using ultrasound with plant matter in a solution, by cavitation shockwave. -Homogenizer: Shear force by forcing cells through tubes smaller than cells, by rotor- stator (rotating blade) or outer layer shear (French Press).

-Freezing: Cell rupture from freeze thaw process. Can take lots of time.

-High Temperature (and Pressure): Cells walls are disrupted, but denatures proteins, and heat can damage cell contents. Typically by autoclave, microwave, steam, etc.

Non-Mechanical Methods:

-Enzymes: Remove cell wall by using naturally occurring enzymes.

-Chemicals: Organic solvents like ethanol (alcohol), especially for hydrophobic (doesn’t like water) molecules. Commonly used with shearing forces.
-Bacteria: EDTA, negative bacteria, to chelate cations that bore holes in cell walls.

REF: http://bitesizebio.com/13536/bringing- down-the-walls-part-ii-8-methods-to-break- down-cell-walls/

 

Cell Lysis Methods:
Reagent Based Methods:
-Fast, efficient, reproducible
-Can extract total protein or subcellular fractions
-Disrupts cell wall and or lipid membrane

 

Physical Methods:
-Expensive equipment
-Larger footprint for equipment

-Less reproducible

-Not compatible with high-throughput and small volumes

-Aggregation and denaturation of protein may occur
-Cells disrupt at different times

REF: https://www.thermofisher. com/us/en/home/life-science/protein- biology/protein-biology-learning- center/protein-biology-resource-library/pierce- protein-methods/traditional-methods-cell-

 

 

Tensile Strength of Cell Walls

Cylindrical Cell Shape: 100 atm or 1,470 psi

Spherical Cell Shape: 95 atm or 1,396 psi

Spherical Cell Shape: 30 atm or 441 psi

REF: https://www.ncbi.nlm.nih. gov/pmc/articles/PMC1074911/pdf/plntphys0 0593-0165.pdf

Plant Cell Vacuoles

The central vacuole (may be 80 percent of space) is a membrane bound sac which provides cell support and helps the plant function with growth.

Turgor Pressure: Vacuoles help to maintain and control the rigidity of the cell (structure),

by compensating the osmotic pressure from within the cell and pressure exerted from outside the cell.

REF: https://micro.magnet.fsu.edu/cells/plants/vacuole.html

Additional Reading:

Cannabis sativa: The Plant of the Thousand and One Molecules

REF: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740396/

 

Cell Disruption Using a Microfluidizer

Using a Microfluidizer versus a French Press using the same 20,000 psi back pressure, resulted in 92 percent breakage in 8 passes, versus only 50 percent breakge for the French Press in 7 passes.

REF: https://www.microfluidicscorp.com/sites/default/files/application-note-cell- disruption-publication-summaries.pdf

Practical Use of Continuous Processing in Developing and Scaling Up Laboratory Processes

Continuous flow reactors allow for better control of exothermic processing than do batch reactions, and allow for a more efficient and safe scale-up of rapid reactions in a smaller footprint.

REF: http://pubs.acs. org/doi/abs/10.1021/op0100605? journalCode=oprdfk

Supercritical Carbon Dioxide Extraction of Cannabinoids from Cannabis Sativa

PDF Link to Review: 20170714-infinity-supercritical-sco2-science-review

SEATTLE, WA  July 2017 (Infinity Supercritical Staff Article Review)

Supercritical fluid extraction with CO2 is already used on a large scale for botanical extraction due to its low cost, generally safe nature, and well known properties.

Reference science pdf article: Rovetto, Laura J., and Niccolo V. Aieta. Supercritical carbon dioxide extraction of cannabinoids from Cannabis sativa L.  The Journal of Supercritical Fluids (2017)

Supercritical (SC) CO2 properties, like density, and thus solvent power, change with temperature and pressure allowing for selectivity via tuning.

One can also use more polar co-solvents, like ethanol, to expand the extraction range of the low-polarity CO2 to include more polar components.

Previous research has shown two different optimal extraction parameters with SFE for terpenes and cannabinoids.

This study did not find a significant difference in extraction rate from 313-333 Kelvin (104- 140 F).
During the extraction time (during the linear trend before exhaustion), a yield of 0.00243g of extract/g of CO2, 0.00455g of extract/g of CO2, and 0.00666g of extract/g of CO2 was found for 17 MPa, 24 MPa, and 34 MPa respectively at 328K. 16.63 percent THC plant potency.

At 34 MPa, 0.0066g of extract/g of CO2, 0.01361g of extract/g of CO2, 0.00431g of extract/g of feed, and 0.00186g of extract/g of feed for the potencies 16.63 percent, 14.03 percent, 10.11 percent and 6.05 percent THC cannabis respectively.

Comparing using SC CO2 at 328K between 17, 24, and 34 MPa, the higher the pressure, the higher the yield, but lower the THC potency of the final mixture. 7.4 percent, 17.2 percent, 18.5 percent extract yield in comparison to total start weight; 76.23 percent, 70.63 percent, 69.41 percent THC potency for over 2 hours. 16.63 percent THC potency starting material and S/F ratios of 50 for high pressures, 100 for low.

At these temperature and pressures, partial decarboxylation takes place on the THCA to THC.

Higher Pressure = Lower Potency

They used a multi-stage depressurization chillers to precipitate the extract. Most of theTHC (and highest extract amount) was found in the first stage at 13 MPa (1,885 psi) and 328K (130 F), but was waxy, pasty, and darker in color. In the second and third separator MPa (1,305 psi) and 328K (130 F) and MPa (870 psi) and 298K (77 F), more fluid yellow color extract appeared.

Compared different potency cannabis (A 16.63 percent, B 14.03 percent, C 10.11 percent, and D 6.05 percent), leading to potencies of extract of A 69.41 percent, B 61.21 percent, C 57.86 percent, and D 56.06 percent total THC. Thus the more originally potent, the more potent the extract.

Extraction efficiency (in relation to THC) rises slightly as potencies decreases (A 89.89 percent, B 89.17 percent, C 90.31 percent, D 92.23 percent).

Extraction efficiency increases as potency decreases.

They attempted to use ethanol as a co- solvents. This would cause more additional process steps, unless you want to use winterization, in which case it does not heavily modify your process line.

No major difference between using 5 percent and 10 percent ethanol by weight in extraction, but noticeable decrease dropping to 2.5 percent. Thus 5 percent is an efficient amount of co-solvents. (328K 131 F, 34 MPa 4,931 psi, S/F 20)

If ethanol is used, use 5 percent.

With the conditions in 12, the plant material was exhausted within 50 minutes of extraction.

Ethanol pulses versus constant flow was compared and pulses either performed better, or the same as constant flow. (2 hour extraction, 5 percent by weight ethanol divided into 3 pulses at 0 minutes, 50 minutes and 110 minutes.)

Since plant material was at exhaustion by the 50 minute mark, only the first pulse was needed to be applied, meaning minimal ethanol is necessary.

Ethanol drastically decreases the SF ratio necessary for lower potencies cannabis to be extracted (only 60 percent of the mass of extract gained using ethanol achieved at 2 hours, compared to the 100 percent gained in 50 minutes).

Something not mentioned in the article, the residual THC in the exhausted plant material is about the same for the lower potency cannabis, implying that the 2 hour extraction extracts all the THC and the extra mass accumulated with the ethanol comes from additional cannabinoids.

Summary:

  1. Higher Pressure = Lower Potency

2. Extraction efficiency increases as potency decreases.

3. Ethanol cosolvent increases extraction, optimized at 5 percent ethanol added.

4. Pulsing performs better than constant flow.