Creating aerogel with supercritical methanol

In previous videos, I used supercritical CO2 to dry my homemade aerogels. This time, I soaked the aerogel in methanol, then raised the temperature and pressure of the methanol itself to make it supercritical. This allows the gels to be dried without an additional solvent exchange into CO2. The downside is that it requires a chamber full of methanol at 460*F and over 1200 psi, which is a much bigger hazard than using CO2.

The aerogels dried with methanol shrank less than the ones dried with CO2, but there was still a lot of cracking, and I have yet to create a high-quality monolith.

Extracting caffeine with methylene chloride

In a previous video, I showed how to extract caffeinated water from green coffee beans with supercritical CO2. Here, I show how to extract dry caffeine crystals from the caffeinated water (ie coffee, in this case). I used a vacuum filtration setup to create very strong coffee, then mixed it with methylene chloride in a seperatory funnel. The methylene chloride sinks below the water, taking most of the caffeine with it. By opening the funnel carefully, only the methylene chloride and caffeine can be transferred to a flask where the methylene chloride is boiled away. I then mounted a test tube in a rubber stopped and filled the tube with ice. With the stopped in the flask, I evacuated the flask and applied heat. The caffeine will sublimate and collect on the cold test tube. I scraped off the caffeine and measured the mass.

Making astronaut ice cream in my home shop

In his recent post, Chris Gammell used astronaut ice cream as a fun example of how high tech innovation trickles down to consumer-level products. Seeing an image of astronaut ice cream in my G+ feed got me thinking about making some of my own. I managed to accomplish this with a harbor freight vacuum pump, some dry ice and various hoses and fittings. The process is known as freeze-drying and allows water to pass directly from ice to vapor, thus allowing the ice cream to maintain its physical structure while it is dried.

What should I freeze-dry next?

http://engineerblogs.org/2012/01/weekend-journal-the-trickle-down-techonomy/

Caffeine extraction from green coffee with supercritical CO2

I finally succeeded in extracting caffeine from green coffee beans by using supercritical CO2. I built a high pressure chamber from 2" steel pipe fittings, and poured in 200mL of water. There is an aluminum screen above the water line, which held 0.75 lbs of moisturized green coffee beans in the upper part of the chamber. I added liquid CO2 to the chamber, then closed all valves and raised the temperature, making the CO2 pass into the supercritical phase. I left the system overnight at about 60*C, 3000 psi, then drained the water. It was very black due to impurities and some bean burning that occurred where my electric strip heater caused localized overheated zones in the chamber. The water was highly caffeinated, and tasted somewhat like coffee. I used a typical hydrocarbon extraction process to isolate the caffeine from the water (will show this in a later video).

Interview with me on the Amp Hour podcast

http://www.theamphour.com/2011/12/26/the-amp-hour-75-sprauncy-saccadic-spintherism/