High flux zirconia composite membrane for hydrogen separation at elevated temperature

[NNadir]

It's suddenly fashionable to hate oil, but the fact is that unless we do something to phase it out, they'll be more of the same, particularly as rigs go deeper and deeper to get to the last oil and gas fields on earth.

The key to the matter is hydrogen, not as a motor fuel for stupid http://news.nationalgeographic.com/news/2001/10/1016_TVhypercar.html">Hydrogen HYPErcars that are always supposed about to come down from the mountain and save us, sort of like Jesus, but as a captive intermediate for the manufacture, from carbon oxides, of clean highly oxygenated fuels like DME or dimethyl carbonate.

Highly educated all over the world are working on the science of producing hydrogen from raw heat, no boilers, no turbines, no wires, just heat in closed systems.

It's exciting.

I've been reading about hydrogen production technology that is not dependent on the dangerous fossil fuel crutches that so appeal to our anti-nukes. Over this weekend I went through more than 100 hydrogen thermochemical cycle papers, most written in the last 5 years.

One paper that struck my eye, but is about 10 years old and has 14 citations concerns hydrogen separations.

It's title is the title of this post. display http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGK-3YVM1S5-F&_user=10&_coverDate=05%2F15%2F2000&_alid=1357349519&_rdoc=1&_fmt=high&_orig=search&_cdi=5257&_sort=r&_docanchor=&view=c&_ct=16&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a700e10a219341b2698a4fbda3c53989">Journal of Membrane Science 170 (2000) 113–125

This is a solid membrane approach. The most widely known hydrogen membrane is the element palladium, through which hydrogen diffuses quite readily. Regrettably palladium is fairly expensive, even when isolated from used nuclear fuel, where it is a major component.

Happily some less expensive option to accomplish this exist. The current paper concerns a ternary oxide mixture containing zirconia, yttria and silica.

Some excerpts from the paper:

Expectation for hydrogen has been increasing, as a clean, renewable and flexible carrier of energy particularly for the means of transport, rockets, vehicles, aeroplanes and so on. Conventional methods of hydrogen production are steam reforming of hydrocarbon, electrolysis of water, by- production of petroleum refining, petrol-chemistry and so on. Unconventional hydrogen production methods which will use unused or untapped energy resources such as nuclear heat, hydrogen sulfide etc., has been investigated; the decomposition of hydrogen sulfide <1>, the thermochemical water decomposition (TCWD) and so on. Several attempts for TCWD process have been made but very few such as UT-3 cycle process <2> and IS process <3> are successful.

Both processes have had a lot of bugs worked out in the last 10 year, a lot in the last 3 years.

The operating conditions of TCWD process are high temperature and highly corrosive environment. Therefore, novel membrane, which have high thermal resistivity and highly corrosive resistance, are required. Zirconia is one of the most thermal resisting materials, showing melting point of 3043 K, and has highly corrosive resistance. Ohya and co-workers <6–9> successfully fabricated composite zirconia membrane on porous alumina tubing by a zirconia–silica alkoxide solution dip-coating and sintering method. The addition of tetraethoxysilane (TEOS) to zirconium-tetra

Tof 90% (membrane G00) shows better separation factor CH4=CO2 than that with 40 times of 90% (membrane C).

3. With our technology at this stage, it seems impossible to obtain successful membranes of ZrO2 contents more than 95%.

4. The pore diameter of the successful membranes were estimated as 2–3 nm by Present and de
Bethune equation <11>.

5. From the correlation of the pure gas permeances against the reciprocal of square root of the quantity of the absolute temperature times moleculer weight, the main permeation mechanism for all
gases except H2O are estimated as Knudsen diffusion and main H2O permeation mechanism surface diffusion. At higher temperature, permeation mechanism for all gases except H2O shifts to the activated diffusion but for H2O to Knudsen diffusion. 6. In the separation experiments of H2–H2O–HBr gaseous mixture, it was found that the maximum separation factors H2=H2O and H2=HBr were 4.1
and 259.

These sort of membrane are conceivably critical for many hydrogen cycles and there are other examples, such as Nalfion HI separators the nearly eliminate side reactonsl

I thought it was cool