An Experimental Protocol for Studying Mineral Effects on Organic Hydrothermal Transformations

This method can help answer key questions in the organic chemistry field such as how earth abundant minerals influence organic molecules in deep ocean hydrothermal systems. The main advantage of this technique is that it is low cost, easy to use, and reliable. Though this method can provide insight into organic mineral interactions in natural hydrothermal systems, it can also be applied to other areas such as hydrothermal treatment of organic glutens or biofused hydrothermal synthesis in green chemistry.

Demonstrating the procedure will be Dr.Xuan Fu from my lab. To begin this procedure, choose a tube size and material and determine the amounts of organic compounds and minerals to use, as outlined in the text protocol. This demonstration will be carried out using nitrobenzene and magnetite loaded into a silicon tube with an inner diameter of two millimeters and an outer diameter of six millimeters.

Using a tube cutter, cut the tubing into small pieces about 30 centimeters in length. Then, use an oxyhydrogen torch with an appropriate flame head to seal one end of the tube closed. If any of the starting organic compounds are liquid, use a microliter syringe to transfer it into the tube.

Using a pasteur pipette, add the pre-weighed materials. Then, add deionized and deoxygenated water. Connect the tube to a vacuum line with a closed valve.

Use a clamp to tightly hold the tube and immerse it in a dewar flask filled with liquid nitrogen. Leave the tube in the liquid nitrogen for approximately three minutes until the organics and water are completely frozen. While the tube is still immersed in liquid nitrogen, open the vacuum valve to remove the air from the headspace of the tube.

After this, switch off the valve. Remove the tube from the liquid nitrogen and let the tube warm up to room temperature. When it has warmed, gently tap the bottom of the tube to release any remaining air bubbles from the solution into the head space.

Repeat this freeze, pump, thaw cycle twice more. Then, while the tube is still immersed in liquid nitrogen, close the vacuum line and use the oxyhydrogen torch to seal the open end of the tube. After the tube has been sealed, transfer it into a small steel pipe equipped with screw caps.

Seal the screw caps loosely to prevent any damage from pressure build up or tube failure. Place the pipe inside a temperature controlled furnace or oven and heat it to the desired temperature. Use a thermocouple inside the oven to monitor the temperature throughout the hydrothermal reaction.

As soon as the reaction time is reached, remove the pipe from the oven and put the tube into a cold water bath to quench the experiment. First, make dichloromethane extraction solution that contains 8.8 micromolar dodecane, as an internal standard for gas chromatography. Transfer three milliliters of the extraction solution into a 10 milliliter glass vial.

Then, use a tube cutter to open the tube and use a pasteur pipette to quickly transfer all of the product into the glass vial. Next, vortex the solution for one minute. Let the mineral particles settle for five minutes.

After this, use a pasteur pipette to carefully transfer approximately one milliliter of the sample from the dichloromethane layer into a GC vial. Using a polycapillary column and a flame ionization detector, analyze the product distribution by gas chromatography as outlined in the text protocol. Build the GC calibration curves and use them to quantify the organic products.

Then, calculate the reaction conversion as outlines in the text protocol. Use these conversions to determine if the mineral facilitates or slows down the hydrothermal organic transformations. This approach to study hydrothermal organic mineral interactions is demonstrated here using nitrobenzene with the mineral magnetite at a hydrothermal condition of 150 degrees Celsius and five bars for two hours.

After the hydrothermal process, the tube containing no magnetite showed no color change, while the tube that did contain magnetite turned a brown color. This implies that an oxidation reaction took place, with magnetite being converted into hematite. Gas chromatography analysis is then performed to determine the amount of magnetite on nitrobenzene conversion.

In the no mineral experiment, the calculated conversion for nitrobenzene is seen to be 5.2%However, in the presence of magnetite, the nitrobenzene conversion is 30.3%an increase by a factor of six. This suggests that magnetite can significantly promote the reaction of nitrobenzene at the utilized hydrothermal conditions. While attempting this procedure, it's important to remember to follow the SOP of using the oxyhydrogen torch.

So following this procedure, other analytical methods like scan electron microscopy and gas chromatography mass spectroscopy can be performed in order to answer additional questions, like whether there's morphology change of the minerals and what are the molecules masses of unknown organic products. After its development, this technique paved the way for researchers in the field of hydrothermal organic chemistry to explore organic mineral interactions in natural hydrothermal systems.