The authors wish to acknowledge start-up funding from The University of Toledo, as well as funds from the American Chemical Society&#39;s Herman Frasch Foundation in partial support of this work. Mr. Thomas Kina is acknowledged for his assistance with developing a suitable pressure gauge for measuring the reaction pressures. Mr. Steve Modar is thanked for useful discussions.

CAUTION: 1) The following protocols have been deemed safe through repeated trials. However, caution should be exercised when sealing vials, throughout the reaction, and especially when opening the reactions, as inhomogeneity in the reaction vials may lead to equipment failure. Vials should be inspected for physical defects prior to use. Vials should be placed behind some form of blast shield or hood sash immediately after sealing to prevent incidents should the vials fail. 2) Although there is little chance for asphyxiation due to the small quantities of CO2 used, reactions should be set-up as well as opened in a well-ventilated area or in a fume hood. 3) Dry ice is a cryogen and can cause serious tissue damage. Care should therefore be exercised while manipulating it to avoid frostbite, such as limiting direct contact or using cryogenic gloves. 4) Dry ice will condense water vapor, meaning that prior to use, the dry ice should be mechanically exfoliated to ensure the mass is of CO2(s) only. This can be achieved by simply rubbing the dry ice between one&#8217;s fingers, or more safely, rubbing it between one&#8217;s fingers with a protective layer such as a glove or towel.
1. Reaction in a 7.5 mL Vial (Air Not Excluded)
<ol>
	<li>Add a stir bar to a dry 7.5 mL vial.</li>
	<li>Add palladium acetate (6.7 mg, 0.03 mmol) to the vial.</li>
	<li>Add silver trifluoroacetate (99.9 mg, 0.45 mmol) to the vial.</li>
	<li>Add phenyl iodide (92.3 mg, 0.45 mmol) to the vial.</li>
	<li>Add tert-amyl amine (26.3 mg, 0.30 mmol) to the vial.</li>
	<li>Add acetic acid (1.0 mL) to the vial. 
	Note: The ratio of solution volume to vial size is important, as the immediate sublimation of CO2 upon addition of dry ice can mechanically displace solvent if too much is used relative to the size of the reaction vessel.</li>
	<li>Add deionized water (21.7 &#956;L, 12.1 mmol) to the vial.</li>
	<li>Weigh dry ice (26.3 mg, 0.60 mmol), and immediately add the dry ice to the vial, while ensuring to also immediately seal the vial with a PTFE-lined cap. 
	Note: The whole operation should be performed within approximately 5 seconds to prevent sublimation and escape of the small amount of CO2 added (this is slowed by the formation of frozen acetic acid around the dry ice). The amount of CO2 added will be an approximate value, and in our hands a deviation of a few mg is permissible.</li>
	<li>Stir the sealed reaction vial for 15 minutes at room temperature.</li>
	<li>Transfer the reaction vessel to a pre-heated plate at 110 &#176;C and stir for 14 hours before allowing to cool.</li>
	<li>Upon cooling, carefully open the vial to vent CO2.</li>
	<li>Remove all of the volatiles in vacuo. 
	Note: This operation can be performed in the vial, or the solution can be transferred to a larger round bottom flask.</li>
	<li>Add 1.2 M HCl(aq) (6 mL) to the reaction mixture and stir open to air for 15 minutes.</li>
	<li>Transfer the aqueous fraction to a separatory funnel, washing with additional 1.2 M HCl (4 mL), and extract with a 1:1 diethyl ether/hexanes mixture (3 x 8 mL). 
	Note: This organic wash contains excess phenyl iodide and other neutral by-products, and can be disposed of.</li>
	<li>Neutralize and make basic the aqueous solution by addition of saturated NH4OH(aq) (10 mL is a good starting point).</li>
	<li>Extract the aqueous layer with dichloromethane (2 x 10 mL).</li>
	<li>Dry the combined organic fractions over Na2SO4, then filter into a tared sample vial.</li>
	<li>Evaporate the solvent in vacuo, giving the product (2-Methyl-4-phenyl-butanamine) as a yellow oil.</li>
</ol>
2. Reaction in a 7.5 mL Vial (Purging Conditions &#8211; Air Excluded)
<ol>
	<li>Add a stir bar to a dry 7.5 mL vial.</li>
	<li>Add palladium acetate (6.7 mg, 0.03 mmol) to the vial.</li>
	<li>Add silver trifluoroacetate (99.9 mg, 0.45 mmol) to the vial.</li>
	<li>Add phenyl iodide (92.3 mg, 0.45 mmol) to the vial.</li>
	<li>Add tert-amyl amine (26.3 mg, 0.30 mmol) to the vial.</li>
	<li>Add acetic acid (1.0 mL) to the vial. 
	Note: The ratio of solution volume to vial size is important, as the immediate sublimation of CO2 upon addition of dry ice can mechanically displace solvent if too much is used relative to the size of the reaction vessel.</li>
	<li>Add deionized water (21.7 &#956;L, 12.1 mmol) to the vial.</li>
	<li>Tare the vial on a balance, add approximately 98 mg of dry ice, and then allow the CO2 to sublimate off until a final mass of approximately 26 mg is achieved, followed by immediately sealing the vial with a PTFE-lined cap. 
	Note: If desirable, this step can be performed with a greater mass of dry ice to further exclude air from the vial. It is noteworthy that this may introduce water, and thus may not be the most effective strategy for water sensitive reactions.</li>
	<li>Stir the sealed reaction vial for 15 minutes at room temperature.</li>
	<li>Transfer the reaction vessel to a pre-heated plate at 110 &#176;C and stir for 14 hours before allowing to cool.</li>
	<li>Upon cooling, carefully open the vial to vent CO2.</li>
	<li>Remove all of the volatiles in vacuo. 
	Note: This operation can be performed in the vial, or the solution can be transferred to a larger round bottom flask.</li>
	<li>Add 1.2 M HCl(aq) (6 mL) to the reaction mixture, and stir open to air for 15 minutes.</li>
	<li>Transfer the aqueous fraction to a separatory funnel, washing with additional 1.2 M HCl (4 mL), and extract with a 1:1 diethyl ether/hexanes mixture (3 x 8 mL). 
	Note: This organic wash contains excess phenyl iodide and other neutral by-products, and can be disposed of.</li>
	<li>Neutralize and make basic the aqueous solution by addition of saturated NH4OH(aq) (10 mL is a good starting point).</li>
	<li>Extract the aqueous layer with dichloromethane (2 x 10 mL).</li>
	<li>Dry the combined organic fractions over Na2SO4, then filter into a tared sample vial.</li>
	<li>Evaporate the solvent in vacuo, giving the product (2-Methyl-4-phenyl-butanamine) as a yellow oil.</li>
</ol>
3. Reaction in a 40 mL Vial (Air Not Excluded)
<ol>
	<li>Add a stir bar to a dry 40 mL vial.</li>
	<li>Add palladium acetate (33.5 mg, 0.15 mmol) to the vial.</li>
	<li>Add silver trifluoroacetate (499.5 mg, 2.25 mmol) to the vial.</li>
	<li>Add phenyl iodide (461.5 mg, 2.25 mmol) to the vial.</li>
	<li>Add tert-amyl amine (131.5 mg, 1.5 mmol) to the vial.</li>
	<li>Add acetic acid (5.0 mL) to the vial. 
	Note: The ratio of solution volume to vial size is important, as the immediate sublimation of CO2 upon addition of dry ice can mechanically displace solvent if too much is used relative to the size of the reaction vessel.</li>
	<li>Add deionized water (108.5 &#956;L, 6.02 mmol) to the vial.</li>
	<li>Weigh dry ice (131.5 mg, 3.0 mmol), and immediately add the dry ice to the vial, while ensuring to also immediately seal the vial with a PTFE-lined cap. 
	Note: The whole operation should be performed within approximately 5 seconds to prevent sublimation and escape of the small amount of CO2 added (this is slowed by the formation of frozen acetic acid around the dry ice). The amount of CO2 added will be an approximate value, and in our hands a deviation of a few mg is permissible.</li>
	<li>Stir the sealed reaction vial for 15 minutes at room temperature.</li>
	<li>Transfer the reaction vessel to a pre-heated plate at 110 &#176;C and stir for 14 hours before allowing to cool.</li>
	<li>Upon cooling, carefully open the vial to vent CO2.</li>
	<li>Remove all of the volatiles in vacuo. 
	Note: This operation can be performed in the vial, or the solution can be transferred to a larger round bottom flask.</li>
	<li>Add 1.2 M HCl(aq) (30 mL) to the reaction mixture and stir open to air for 15 minutes.</li>
	<li>Transfer the aqueous fraction to a separatory funnel, washing with additional 1.2 M HCl (20 mL), and extract with a 1:1 diethyl ether/hexanes mixture (3 x 8 mL). 
	Note: This organic wash contains excess phenyl iodide and other neutral by-products, and can be disposed of.</li>
	<li>Neutralize and make basic the aqueous solution by addition of saturated NH4OH(aq) (10 mL is a good starting point).</li>
	<li>Extract the aqueous layer with dichloromethane (2 x 20 mL).</li>
	<li>Dry the combined organic fractions over Na2SO4, then filter into a tared sample vial.</li>
	<li>Evaporate the solvent in vacuo, giving the product (2-Methyl-4-phenyl-butanamine) as a yellow oil.</li>
</ol>
4. Reaction in a 35 mL Pressure Tube (Air not excluded)
<ol>
	<li>Add a stir bar to a dry 35 mL pressure tube.</li>
	<li>Add palladium acetate (6.7 mg, 0.03 mmol) to the pressure tube.</li>
	<li>Add silver trifluoroacetate (132.5 mg, 0.6 mmol) to the pressure tube.</li>
	<li>Add phenyl iodide (183.6 mg, 0.9 mmol) to the pressure tube.</li>
	<li>Add 2-methyl-N-(3-methylbenzyl)butan-2-amine (57.4 mg, 0.3 mmol) to the pressure tube.</li>
	<li>Add acetic acid (1.0 mL) to the vial, followed by 1,1,1,3,3,3,-hexafluoroisopropanol (1.0 mL). 
	Note: The ratio of solution volume to vial size is important, as the immediate sublimation of CO2 upon addition of dry ice can mechanically displace solvent if too much is used relative to the size of the reaction vessel.</li>
	<li>Add deionized water (21.7 &#956;L, 1.2 mmol) to the pressure tube.</li>
	<li>Weigh dry ice (1.32 g, 30 mmol), and immediately add the dry ice to the pressure tube, while ensuring to also immediately seal the pressure tube with the appropriate Teflon screw cap. 
	Note: The whole operation should be performed within approximately 5 seconds to prevent sublimation and escape of the small amount of CO2 added (this is slowed by the formation of frozen acetic acid around the dry ice). The amount of CO2 added will be an approximate value, and in our hands a deviation of a few mg is permissible.</li>
	<li>Stir the sealed reaction vessel for 15 minutes at room temperature.</li>
	<li>Transfer the reaction vessel to a pre-heated plate at 90 &#176;C and stir for 24 hours before allowing to cool.</li>
	<li>Upon cooling, put a towel or padded glove over the cap, and carefully open the pressure tube to vent CO2.</li>
	<li>Remove all of the volatiles in vacuo. 
	Note: This operation can be performed in the pressure tube with an appropriate adaptor, or the solution can be transferred to a larger round bottom flask.</li>
	<li>Add 1.2 M HCl(aq) (12 mL) to the reaction mixture and stir open to air for 15 minutes.</li>
	<li>Transfer the aqueous fraction to a separatory funnel, washing with additional 1.2 M HCl (8 mL), and extract with a 1:1 diethyl ether/hexanes mixture (3 x 8 mL). 
	Note: This organic wash contains excess phenyl iodide and other neutral by-products and can be disposed of.</li>
	<li>Neutralize and make basic the aqueous solution by addition of saturated NH4OH(aq) (10 mL is a good starting point).</li>
	<li>Extract the aqueous layer with dichloromethane (2 x 10 mL).</li>
	<li>Dry the combined organic fractions over Na2SO4, then filter into a tared sample vial.</li>
	<li>Evaporate the solvent in vacuo, giving the product (2-Methyl-N-(3-methylbenzyl)-4-phenylbutan-2-amine) as a yellow oil.</li>
</ol>

The use of CO2 as a directing group for C-H activation of Lewis basic substrates is currently the focus of United States Provisional Patent #62/608,074.

Using the van der Waals Equation of State, the approximate pressure of these systems can be calculated45
Eq. 1:&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;<img alt="Equation" src="/files/ftp_upload/58281/58281eq1.jpg" />
Under the conditions in Protocol 1, we can assume 26.3 mg of CO2 gives n =5.98 x 10-4 mols
<img alt="Equation 1b" src="/files/ftp_upload/5828...

The use of gaseous compounds in chemical reactions typically requires specialized equipment and procedures1,2. At bench scale, some gases can be added directly from a tank using a high pressure regulator3. An alternative method is to condense the gas under cryogenic conditions4,5. Although useful, these strategies require the use of specialized pressure reactors with valves, which can be cost prohibitive for running numerous reactions in parallel. This can therefore greatly slow the rate at which reaction screening can proceed. As a result, chemists have found it desirable to introduce these compounds using alternative methods. Ammonia can be added to reactions using different ammonium carboxylate salts, taking advantage of the weak equilibrium between these salts and free ammonia6. Transfer hydrogenation is an important strategy for reduction reactions of olefins, carbonyl, and nitro groups that circumvents the use of flammable hydrogen gas with compounds such as ammonium formate or hydrazine as carriers of H27. Another gas of interest in this area is carbon monoxide8 &#8211; CO can be generated in situ by liberation from metal carbonyl complexes9,10, or alternatively it can be generated by decarbonylation from sources such as formates and formamides11,12,13 or chloroform14,15.
One gas which has not enjoyed significant development in this respect is carbon dioxide16. One reason for this is that many transformations that involve CO2 also require high temperatures and pressures, and thus are automatically relegated to specialized reactors17,18. Recent efforts to develop more reactive catalysts, however, have facilitated running many of these reactions under atmospheric pressures of CO219,20,21,22. We recently discovered a reaction in which carbon dioxide could be used to mediate the &#947;-C(sp3)&#8211;H arylation of aliphatic amines23. This strategy was expected to combine the benefits of a static directing group approach including amide24,25,26,27,28, sulfonamide29,30,31,32, thiocarbonyl33,34, or hydrazone35-based directing groups (chemical robusticity), with the ease of a transient directing group (decreased step economy)36,37,38,39.
Although the reaction could occur under atmospheric pressure of CO2, the need for a Schlenk set-up to screen reactions proved prohibitively slow. Furthermore, increasing the pressure slightly led to improved reaction yields, but could not be easily achieved using a Schlenk line. We therefore sought an alternative strategy, and subsequently identified that dry ice could be easily used as a solid source of CO2 that could be added to a variety of reaction vessels to introduce the necessary amount of carbon dioxide to achieve moderate pressures (Figure 1). Though underutilized in synthesis, a similar strategy is fairly common as a method to generate liquid CO2 for chromatography and extraction applications40,41,42,43,44. Utilizing this strategy allowed our group to rapidly screen large numbers of reactions in parallel, while the ability to access moderate CO2 pressures of between 2-20 atmospheres were critical to improving the yields of the reactions. Under these conditions, both primary (1&#176;) and secondary (2&#176;) amines can be arylated with electron rich and electron poor aryl halides.

<table><tbody><tr><td>7.5 mL Sample Vial with Screw Cap (Thermoset)</td><td>Qorpak</td><td>GLC-00984</td><td>Can be reused.</td></tr><tr><td>40 mL Sample Vial with Screw Cap (Thermoset)</td><td>Qorpak</td><td>GLC-01039</td><td>Can be reused.</td></tr><tr><td>Pressure Tube, #15 Thread, 7&quot; Long, 25.4 mm O.D.</td><td>Ace Glass</td><td>8648-06</td><td>Can be reused.</td></tr><tr><td>Pie-Block for 2 Dram Vials</td><td>ChemGlass</td><td>CG-1991-P14</td><td>Can be reused.</td></tr><tr><td>Pie-Block for 10 Dram Vials</td><td>ChemGlass</td><td>CG-1991-P12</td><td>Can be reused.</td></tr><tr><td>3.2 mm PTFE Disposable Stir Bars</td><td>Fisher</td><td>14-513-93</td><td>Can be reused.</td></tr><tr><td>C-MAG HS 7 Control Hotplate</td><td>IKA</td><td>20002695</td><td></td></tr><tr><td>Analytical Weighing Balance</td><td>Sartorius</td><td>QUINTIX2241S</td><td></td></tr><tr><td>Double-Ended Micro-Tapered Spatula</td><td>Fisher Scientific</td><td>21-401-10</td><td></td></tr><tr><td>Hei-VAP Advantage - Hand Lift Model with G5 Dry Ice Condenser Rotary Evaporator</td><td>Heidolph</td><td>561-01500-00</td><td></td></tr><tr><td>Bump Trap 14/20 Joint</td><td>ChemGlass</td><td>CG-1322-01</td><td></td></tr><tr><td>&lt;em&gt;tert&lt;/em&gt;-Amyl amine</td><td>Alfa Aesar</td><td>B24639-14</td><td>Used as received.</td></tr><tr><td>2-Methyl-N-(3-methylbenzyl)butan-2-amine</td><td>N/A</td><td>N/A</td><td>Prepared from reductive amination of &lt;em&gt;tert&lt;/em&gt;-amyl amine and 3-tolualdehyde in the presence of sodium borohydride in methanol.</td></tr><tr><td>Palladium Acetate</td><td>Chem-Impex International, Inc.</td><td>4898</td><td>Used as received.</td></tr><tr><td>Silver Trifluoroacetate</td><td>Oakwood Chemicals</td><td>007271</td><td>Used as received.</td></tr><tr><td>Phenyl Iodide</td><td>Oakwood Chemicals</td><td>003461</td><td>Used as received.</td></tr><tr><td>Acetic Acid</td><td>Fisher Chemical</td><td>A38</td><td>Used as received.</td></tr><tr><td>1,1,1,3,3,3-Hexafluoroisopropanol</td><td>Oakwood Chemicals</td><td>003409</td><td>Used as received.</td></tr><tr><td>Deionized Water</td><td></td><td></td><td>Obtained from &lt;em&gt;in-house&lt;/em&gt; deionized water system.</td></tr><tr><td>Dry Ice</td><td>Carbonic Enterprises Dry Ice Inc.</td><td></td><td>&lt;em&gt;Non-food grade&lt;/em&gt; dry ice.</td></tr><tr><td>Concentrated Hydrochloric Acid</td><td>Fisher Chemical</td><td>A144SI</td><td>Diluted to a 1.2 M solution prior to use.</td></tr><tr><td>Diethyl Ether, Certified</td><td>Fisher Chemical</td><td>E138</td><td>Used as received.</td></tr><tr><td>Hexanes, Certified ACS</td><td>Fisher Chemical</td><td>H292</td><td>Used as received.</td></tr><tr><td>Saturated Ammonium Hydroxide</td><td>Fisher Chemical</td><td>A669</td><td>Used as received.</td></tr><tr><td>Dichloromethane</td><td>Fisher Chemical</td><td>D37</td><td>Used as received.</td></tr><tr><td>Sodium Sulfate, Anhydrous</td><td>Oakwood Chemicals</td><td>044702</td><td>Used as received.</td></tr><tr><td>250 mL Separatory Funnel</td><td></td><td></td><td>Prepared &lt;em&gt;in-house&lt;/em&gt; by staff glassblower.</td></tr><tr><td>100 mL Round Bottom Flask</td><td></td><td></td><td>Prepared &lt;em&gt;in-house&lt;/em&gt; by staff glassblower.</td></tr><tr><td>Scientific Disposable Funnel</td><td>Caplugs</td><td>2085136030</td><td></td></tr><tr><td>Borosilicate Glass Scintillation Vials, 20 mL</td><td>Fisher Scientific</td><td>03-337-15</td><td></td></tr><tr><td>5 mm O.D. Thin Walled Precision NMR Tubes</td><td>Wilmad</td><td>666000575</td><td></td></tr><tr><td>Chloroform-&lt;em&gt;d&lt;/em&gt;</td><td>Cambridge Isotope Laboratories, Inc.</td><td>DLM-7</td><td>Used as received.</td></tr></tbody></table>

achieving moderate pressures in sealed vessels using dry ice as a solid co2 source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Following these protocols, it is possible to charge a reaction vial with an appropriate amount of carbon dioxide to achieve chemical reactions that require CO2 atmospheres. The pressure achieved in Step 1 is calculated to be approximately 3 atmospheres (see discussion for determination of this value), although due to partial solvation, the observed pressure is in the vicinity of 2 atmospheres at room temperature, and should be approximately 2.6 atmospheres under the reaction co...

Watch this Scientific Journal Video about Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source at JoVE.com

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

achieving-moderate-pressures-sealed-vessels-using-dry-ice-as-solid

Research

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Chemistry

9.9K Views.  University of Toledo. Hier presenteren we een protocol voor het uitvoeren van reacties in eenvoudige reactie vaartuigen onder lage tot matige druk van CO2. De reacties kunnen worden uitgevoerd in een verscheidenheid van vaartuigen gewoon door het toedienen van de kooldioxide in de vorm van droogijs, zonder de noodzaak voor dure of ingewikkelde apparatuur of set-ups.

Video: Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40&#160;&#176;C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure.
The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure.

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. ...

Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. Therefore, it is highly desirable to remove biofilms from surfaces. Many studies on CO2 aerosol cleaning have employed nitrogen purges to increase biofilm removal efficiency by reducing the moisture condensation generated during the cleaning. However, in this study, periodic jets of CO2 aerosols without nitrogen purges were used to remove Pseudomonas putida biofilms from polished stainless steel surfaces. CO2 aerosols are mixtures of solid and gaseous CO2 and are generated when high-pressure CO2 gas is adiabatically expanded through a nozzle. These high-speed aerosols were applied to a biofilm that had been grown for 24 hr. The removal efficiency ranged from 90.36% to 98.29% and was evaluated by measuring the fluorescence intensity of the biofilm as the treatment time was varied from 16 sec to 88 sec. We also performed experiments to compare the removal efficiencies with and without nitrogen purges; the measured biofilm removal efficiencies were not significantly different from each other (t-test, p &gt; 0.55). Therefore, this technique can be used to clean various bio-contaminated surfaces within one minute.

Biofilms on surfaces can be effectively and rapidly removed by using a periodic jet of carbon dioxide aerosols without a nitrogen purge.

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. ...

Environment

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).

Fizzy extraction is a new laboratory technique for analysis of volatile and semivolatile compounds. A carrier gas is dissolved in the liquid sample by applying overpressure and stirring the sample. The sample chamber is then decompressed. The analyte species are liberated to the gas phase due to effervescence.

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid cooling, to prepare the desired cryogenic temperature phase. Microliter to picoliter size drops are cooled by projection into a liquid nitrogen-argon (N2-Ar) mixture. The cryogenic temperature phase of the drop is evaluated using a visual assay that correlates with X-ray diffraction measurements. The density of the liquid N2-Ar mixture is adjusted by adding N2 or Ar until the drop becomes neutrally buoyant. The density of this mixture and thus of the drop is determined using a test mass and Archimedes principle. With appropriate care in drop preparation, management of gas above the liquid cryogen mixture to minimize icing, and regular mixing of the cryogenic mixture to prevent density stratification and phase separation, densities accurate to &#60;0.5% of drops as small as 50 pL can readily be determined. Measurements on aqueous cryoprotectant mixtures provide insight into cryoprotectant action, and provide quantitative data to facilitate thermal contraction matching in biological cryopreservation.

A protocol for determining the vitreous phase densities of micro- to pico-liter size drops of aqueous mixtures at cryogenic temperatures is described.

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid ...

Engineering

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and increasing the recovery of coalbed methane. A visualized and constant-volume gas-solid coupling system is introduced here to investigate the influence of CO2 sorption on the physical and mechanical properties of coal. Being able to keep a constant volume and monitor the sample using a camera, this system offers the potential to improve instrument accuracy and analyze fracture evolution with a fractal geometry method. This paper provides all steps to perform a uniaxial compression experiment with a briquette sample in different CO2 pressures with the gas-solid coupling test system. A briquette, cold-pressed by raw coal and sodium humate cement, is loaded in high-pressure CO2, and its surface is monitored in real-time using a camera. However, the similarity between the briquette and the raw coal still needs improvement, and a flammable gas such as methane (CH4) cannot be injected for the test. The results show that CO2 sorption leads to peak strength and elastic modulus reduction of the briquette, and the fracture evolution of the briquette in a failure state indicates fractal characteristics. The strength, elastic modulus, and fractal dimension are all correlated with CO2 pressure but not with a linear correlation. The visualized and constant-volume gas-solid coupling test system can serve as a platform for experimental research about rock mechanics considering the multifield coupling effect.

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

This protocol demonstrates how to prepare a briquette sample and conduct a uniaxial compression experiment with a briquette in different CO2 pressures using a visualized and constant-volume gas-solid coupling test system. It also aims to investigate changes in terms of coal&#8217;s physical and mechanical properties induced by CO2 adsorption.

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and ...

Methane Hydrate Crystallization on Sessile Water Droplets

This paper describes a method to form methane hydrate shells on water droplets. In addition, it provides blueprints for a pressure cell rated to 10 MPa working pressure, containing a stage for sessile droplets, a sapphire window for visualization, and temperature and pressure transducers. A pressure pump connected to a methane gas cylinder is used to pressurize the cell to 5 MPa. The cooling system is a 10 gallon (37.85 L) tank containing a 50% ethanol solution cooled via ethylene glycol through copper coils. This setup enables the observation of the temperature change associated with hydrate formation and dissociation during cooling and depressurization, respectively, as well as visualization and photography of the morphologic changes of the droplet. With this method, rapid hydrate shell formation was observed at ~-6 &#176;C to -9 &#176;C. During depressurization, a 0.2 &#176;C to 0.5 &#176;C temperature drop was observed at the pressure/temperature (P/T) stability curve due to exothermic hydrate dissociation, confirmed by visual observation of melting at the start of the temperature drop. The "memory effect" was observed after repressurizing to 5 MPa from 2 MPa. This experimental design allows the monitoring of pressure, temperature, and morphology of the droplet over time, making this a suitable method for testing various additives and substrates on hydrate morphology.

We describe a method to form gas hydrate on sessile water droplets to study the effects of various inhibitors, promoters, and substrates on the hydrate crystal morphology.

This paper describes a method to form methane hydrate shells on water droplets. In addition, it provides blueprints for a pressure cell rated to 10 MPa ...

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol&#8211;gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development.

Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

This procedure describes how to encapsulate cytochrome c (cyt. c) in silica (SiO2) sol-gels, process these gels to form bioaerogels, and use these bioaerogels to rapidly recognize nitric oxide (NO) through a gas-phase reaction. This type of protocol may aid in the future development of biosensors or other bioanalytical devices.

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are ...

Bioengineering

Cryogenic Liquid Jets for High Repetition Rate Discovery Science

This protocol presents a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as described here, the jet exhibits high laminarity and stability for centimeters. Successful operation of a cryogenic liquid jet in the Rayleigh regime requires a basic understanding of fluid dynamics and thermodynamics at cryogenic temperatures. Theoretical calculations and typical empirical values are provided as a guide to design a comparable system. This report identifies the importance of both cleanliness during cryogenic source assembly and stability of the cryogenic source temperature once liquefied. The system can be used for high repetition rate laser-driven proton acceleration, with an envisioned application in proton therapy. Other applications include laboratory astrophysics, materials science, and next-generation particle accelerators.

This protocol presents the operation and principles of micron-scale cylindrical and planar cryogenic liquid jets. Until now, this system has been used as a high repetition rate target in laser-plasma experiments. Anticipated cross-disciplinary applications range from laboratory astrophysics to material science, and eventually next-generation particle accelerators.

This protocol presents a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as ...

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a result, these platforms have not been fully exploited for direct observation of high-pressure transport in fractures. This work introduces microfluidic platforms that enable direct observation of multiphase flow in devices featuring surrogate permeable media and fractured systems. Such platforms provide a pathway to address important and timely questions such as those related to CO2 capture, utilization and storage. This work provides a detailed description of the fabrication techniques and an experimental setup that may serve to analyze the behavior of supercritical CO2 (scCO2) foam, its structure and stability. Such studies provide important insights regarding enhanced oil recovery processes and the role of hydraulic fractures in resource recovery from unconventional reservoirs. This work presents a comparative study of microfluidic devices developed using two different techniques: photolithography/wet-etching/thermal-bonding versus Selective Laser-induced Etching. Both techniques result in devices that are chemically and physically resistant and tolerant of high pressure and temperature conditions that correspond to subsurface systems of interest. Both techniques provide pathways to high-precision etched microchannels and capable lab-on-chip devices. Photolithography/wet-etching, however, enables fabrication of complex channel networks with complex geometries, which would be a challenging task for laser etching techniques. This work summarizes a step-by-step photolithography, wet-etching and glass thermal-bonding protocol and, presents representative observations of foam transport with relevance to oil recovery from unconventional tight and shale formations. Finally, this work describes the use of a high-resolution monochromatic sensor to observe scCO2 foam behavior where the entirety of the permeable medium is observed simultaneously while preserving the resolution needed to resolve features as small as 10 &#181;m.

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs

This paper describes a protocol along with a comparative study of two microfluidic fabrication techniques, namely photolithography/wet-etching/thermal-bonding and Selective Laser-induced Etching (SLE), that are suitable for high-pressure conditions. These techniques constitute enabling platforms for direct observation of fluid flow in surrogate permeable media and fractured systems under reservoir conditions.

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a ...

Degassing Liquids with Freeze-Pump-Thaw Cycling

Source: Laboratory of Dr. Neil Branda &#8212;&#160;Simon Fraser University
Degassing refers to the process by which dissolved gases are removed from a liquid. The presence of dissolved gases such as oxygen or carbon dioxide can impede chemical reactions that utilize sensitive reagents, interfere with spectroscopic measurements, or can induce unwanted bubble formation.

A number of different techniques are available for degassing liquids; some of these include heating, ultrasonic agitation, chemical removal of gases, substitution with inert gas by bubbling and freeze-pump-thaw cycling. Freeze-pump-thaw cycling is a common and effective method for small scale degassing, and will be demonstrated here in more detail.

Source: Laboratory of Dr. Neil Branda &#8212;&#160;Simon Fraser University
Degassing refers to the process by which dissolved gases are removed from a ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO₂ Source

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