The Most Abundant Element is Not Always Easily Captured
As the most abundant element in the universe, hydrogen might seem easy to come by, except that it’s usually bonded to oxygen in water or bound in organic compounds. Many applications, though, require pure hydrogen.
For example, hydrogen can be used as the carrier to separate complex mixtures with gas chromatography. Hydrogen gas can also be used in other analytical techniques, such as inductively coupled plasma mass spectrometry (ICP-MS). The applications, however, go beyond the lab. For example, hydrogen gas can fuel vehicles. The question is: How do you get pure hydrogen gas?
Typically, scientists collect hydrogen gas with an alkaline technique or with a proton exchange membrane (PEM). Both can collect pure hydrogen from water and produce a very pure gas. Canadian-based Hydrogenics makes both kinds of generators, and the company’s scientists say that both make “99.999 percent pure, dry, and carbon-free hydrogen.”
Top techniques
Ed Connor, the gas chromatography product specialist at Peak Scientific in Scotland, says, “PEM is like a reverse fuel cell. It uses electricity to split water into hydrogen and oxygen, and it works very well.” As the hydrogen ions move through the PEM cell, though, they can pull some moisture along that needs to be removed with a dryer.
As long as the water is pure in PEM, a generator can work effectively for a long time. Connor says, “If using really good water, systems can remain in the field for over ten years.” His company’s PEM generators use a deionizer resin that must be replaced as needed, usually about every six months. In general, says Connor, “All you have to do is maintain the water quality and supply electricity.”
The alkaline technique also needs pure water and electricity. Hydrogenics’ engineering team says that “even the alkaline platform is a mature and proven stable technology and requires a smaller initial investment.”
They add, “At higher capacities, the PEM technology is more cost- competitive and has several benefits, including flexibility, lower maintenance, and a smaller footprint.”
Brewing up benefits
At New Belgium Brewing Company in Colorado, scientists use hydrogen as the carrier for two kinds of gas chromatography, one with an electron capture detector (ECD) and another with MS. The hydrogen comes from a PEM-based generator. When asked about the benefits of generating hydrogen on-site, New Belgium Brewing’s chemistry lab manager Dana Sedin says, “We have no gas cylinders in our lab, to keep the cost and complexity at a minimum.” He adds, “We are located in a second-floor space, so it can be a challenge to move cylinders into the lab, or we are stuck with long gas lines, which can be problematic for troubleshooting.” In addition, Sedin points out that they don’t need to monitor the usage of tanks, since they make the hydrogen as needed. He says, “Hydrogen is also our preferred carrier gas, so generators add a sense of safety compared with cylinders.”
Hydrogenics scientists suggest several considerations when looking for a hydrogen-generating system, including the initial investment and operating costs, reliability versus state-of-the-art technology, ease of operation, and flexibility. Platforms can also provide continuous flow or batch production.
In the future, even more hydrogen is likely to be used, both inside and outside of labs. For example, the so-called “hydrogen economy” will drive the demand for hydrogen, which could be used to replace fossil fuels. While burning traditional fuel generates carbon dioxide, the combustion of hydrogen produces only water. Nonetheless, expanding the use of hydrogen gas as a fuel requires efficient and economical ways to produce it in large volumes. Ironically, the most abundant element is not always easy to capture.
For additional resources on hydrogen generators, including useful articles and a list of manufacturers, visit www.labmanager.com/gas-generators